anderson

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Author name code: anderson
ADS astronomy entries on 2022-09-14
author:"Anderson, Lawrence S."

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Title: Self-absorption in [C II], 12CO, and H II in
RCW120. Building up a geometrical and physical model of the region
(Corrigendum)
Authors: Kabanovic, S.; Schneider, N.; Ossenkopf-Okada, V.; Falasca,
F.; Güsten, R.; Stutzki, J.; Simon, R.; Buchbender, C.; Anderson,
L.; Bonne, L.; Guevara, C.; Higgins, R.; Koribalski, B.; Luisi,
M.; Mertens, M.; Okada, Y.; Röllig, M.; Seifried, D.; Tiwari, M.;
Wyrowski, F.; Zavagno, A.; Tielens, A. G. G. M.
2022A&A...660C...2K Altcode:
No abstract at ADS

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Title: Self-absorption in [C II], 12CO, and H I in
RCW120. Building up a geometrical and physical model of the region
Authors: Kabanovic, S.; Schneider, N.; Ossenkopf-Okada, V.; Falasca,
F.; Güsten, R.; Stutzki, J.; Simon, R.; Buchbender, C.; Anderson,
L.; Bonne, L.; Guevara, C.; Higgins, R.; Koribalski, B.; Luisi,
M.; Mertens, M.; Okada, Y.; Röllig, M.; Seifried, D.; Tiwari, M.;
Wyrowski, F.; Zavagno, A.; Tielens, A. G. G. M.
2022A&A...659A..36K Altcode: 2021arXiv211211336K
 Aims: Revealing the 3D dynamics of H II region bubbles and
their associated molecular clouds and H I envelopes is important
for developing an understanding of the longstanding problem as to
how stellar feedback affects the density structure and kinematics
of the different phases of the interstellar medium. Methods:
We employed observations of the H II region RCW 120 in the [C II] 158
μm line, observed within the Stratospheric Observatory for Infrared
Astronomy (SOFIA) legacy program FEEDBACK, and in the 12CO
and 13CO (3 →2) lines, obtained with the Atacama Pathfinder
Experiment (APEX) to derive the physical properties of the gas in the
photodissociation region (PDR) and in the molecular cloud. We used high
angular resolution H I data from the Southern Galactic Plane Survey
to quantify the physical properties of the cold atomic gas through
H I self-absorption. The high spectral resolution of the heterodyne
observations turns out to be essential in order to analyze the physical
conditions, geometry, and overall structure of the sources. Two types
of radiative transfer models were used to fit the observed [C II] and CO
spectra. A line profile analysis with the 1D non-LTE radiative transfer
code SimLine proves that the CO emission cannot stem from a spherically
symmetric molecular cloud configuration. With a two-layer multicomponent
model, we then quantified the amount of warm background and cold
foreground gas. To fully exploit the spectral-spatial information in
the CO spectra, a Gaussian mixture model was introduced that allows for
grouping spectra into clusters with similar properties. Results:
The CO emission arises mostly from a limb-brightened, warm molecular
ring, or more specifically a torus when extrapolated in 3D. There is
a deficit of CO emission along the line-of-sight toward the center
of the H II region which indicates that the H II region is associated
with a flattened molecular cloud. Self-absorption in the CO line may
hide signatures of infalling and expanding molecular gas. The [C II]
emission arises from an expanding [C II] bubble and from the PDRs in the
ring/torus. A significant part of [C II] emission is absorbed in a cool
(~60-100 K), low-density (&lt;500 cm−3) atomic foreground
layer with a thickness of a few parsec. Conclusions: We propose
that the RCW 120 H II region formed in a flattened, filamentary, or
sheet-like, molecular cloud and is now bursting out of its parental
cloud. The compressed surrounding molecular layer formed a torus around
the spherically expanding H II bubble. This scenario can possibly be
generalized for other H II bubbles and would explain the observed "flat"
structure of molecular clouds associated with H II bubbles. We suggest
that the [C II] absorption observed in many star-forming regions is at
least partly caused by low-density, cool, H I -envelopes surrounding the
molecular clouds. The 12CO and 13CO (3 →2)
data shown in Fig. 4 are only available at the CDS via anonymous ftp
to <A href="http://cdsarc.u-strasbg.fr">cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/659/A36">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/659/A36</A>
The [C II] data are provided at the
NASA/IPAC Infrared science archive at <A
href="https://irsa.ipac.caltech.edu/Missions/sofia.html">https://irsa.ipac.caltech.edu/Missions/sofia.html</A>

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Title: The SEDIGISM survey: The influence of spiral arms on the
molecular gas distribution of the inner Milky Way
Authors: Colombo, D.; Duarte-Cabral, A.; Pettitt, A. R.; Urquhart,
J. S.; Wyrowski, F.; Csengeri, T.; Neralwar, K. R.; Schuller, F.;
Menten, K. M.; Anderson, L.; Barnes, P.; Beuther, H.; Bronfman,
L.; Eden, D.; Ginsburg, A.; Henning, T.; König, C.; Lee, M. -Y.;
Mattern, M.; Medina, S.; Ragan, S. E.; Rigby, A. J.; Sánchez-Monge,
Á.; Traficante, A.; Yang, A. Y.; Wienen, M.
2022A&A...658A..54C Altcode: 2021arXiv211006071C
The morphology of the Milky Way is still a matter of debate. In
order to shed light on uncertainties surrounding the structure of
the Galaxy, in this paper, we study the imprint of spiral arms on the
distribution and properties of its molecular gas. To do so, we take
full advantage of the SEDIGISM (Structure, Excitation, and Dynamics
of the Inner Galactic Interstellar Medium) survey that observed a
large area of the inner Galaxy in the 13CO (2-1) line
at an angular resolution of 28”. We analyse the influences of the
spiral arms by considering the features of the molecular gas emission
as a whole across the longitude-velocity map built from the full
survey. Additionally, we examine the properties of the molecular clouds
in the spiral arms compared to the properties of their counterparts
in the inter-arm regions. Through flux and luminosity probability
distribution functions, we find that the molecular gas emission
associated with the spiral arms does not differ significantly from
the emission between the arms. On average, spiral arms show masses
per unit length of ~105-106 M⊙
kpc−1. This is similar to values inferred from data
sets in which emission distributions were segmented into molecular
clouds. By examining the cloud distribution across the Galactic plane,
we infer that the molecular mass in the spiral arms is a factor of 1.5
higher than that of the inter-arm medium, similar to what is found
for other spiral galaxies in the local Universe. We observe that
only the distributions of cloud mass surface densities and aspect
ratio in the spiral arms show significant differences compared to
those of the inter-arm medium; other observed differences appear
instead to be driven by a distance bias. By comparing our results
with simulations and observations of nearby galaxies, we conclude
that the measured quantities would classify the Milky Way as a
flocculent spiral galaxy, rather than as a grand-design one. Full Table 1 is only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/658/A54">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/658/A54</A>

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Title: VizieR Online Data Catalog: Self-absorption in RCW 120
(Kabanovic+, 2022)
Authors: Kabanovic, S.; Schneider, N.; Ossenkopf-Okada, V.; Falasca,
F.; Guesten, R.; Stutzki, J.; Simon, R.; Buchbender, C.; Anderson,
L.; Bonne, L.; Guevara, C.; Higgins, R.; Koribalski, B.; Luisi,
M.; Mertens, M.; Okada, Y.; Roellig, M.; Seifried, D.; Tiwari, M.;
Wyrowski, F.; Zavagno, A.; Tielens, A. G. G. M.
2021yCat..36590036K Altcode:
Spectral data cubes of 12CO (3-2) (at 345.796GHz) and
1 (at 330.588GHz),using the LAsMA array on APEX (Atacama
Pathfinder Experiment) telescope. All spectra are calibrated in main
beam brightness temperatures with a main-beam efficiency of 0.68 at
345.8GHz. The observed spectra are convolved with a Gaussian
function to 20” resolution on a grid with a pixel size of 5”. The spectra are resampled to a velocity resolution of 1 km/s. (2 data files).

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Title: ePESSTO+ spectroscopic classification of optical transients
Authors: Pessi, P. J.; Galbany, L.; Gromadzki, M.; Benetti, S.; Ihanec,
N.; Paraskeva, E.; Chen, T. W.; Strotjohann, N. L.; Anderson; Bravo,
T. M.; Inserra, C.; Kankare, E.; Nicholl, M.; Yaron, O.; Young, D.;
Tonry, J.; Denneau, L.; Heinze, A.; Weiland, H.; Stalder, B.; Rest, A.;
Smith, K. W.; Smartt, S. J.; Gillanders, J.; McBrien, O.; Srivastav, S.
2021TNSAN.209....1P Altcode:
This report includes classifications of 8 Type Ia's, 2 Type Ic-BL's,
2 Type II's and a Tybe Ib, We encourage follow-up observations.

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Title: The SEDIGISM survey: First Data Release and overview of the
Galactic structure
Authors: Schuller, F.; Urquhart, J. S.; Csengeri, T.; Colombo,
D.; Duarte-Cabral, A.; Mattern, M.; Ginsburg, A.; Pettitt, A. R.;
Wyrowski, F.; Anderson, L.; Azagra, F.; Barnes, P.; Beltran, M.;
Beuther, H.; Billington, S.; Bronfman, L.; Cesaroni, R.; Dobbs, C.;
Eden, D.; Lee, M. -Y.; Medina, S. -N. X.; Menten, K. M.; Moore, T.;
Montenegro-Montes, F. M.; Ragan, S.; Rigby, A.; Riener, M.; Russeil,
D.; Schisano, E.; Sanchez-Monge, A.; Traficante, A.; Zavagno, A.;
Agurto, C.; Bontemps, S.; Finger, R.; Giannetti, A.; Gonzalez,
E.; Hernandez, A. K.; Henning, T.; Kainulainen, J.; Kauffmann, J.;
Leurini, S.; Lopez, S.; Mac-Auliffe, F.; Mazumdar, P.; Molinari, S.;
Motte, F.; Muller, E.; Nguyen-Luong, Q.; Parra, R.; Perez-Beaupuits,
J. -P.; Schilke, P.; Schneider, N.; Suri, S.; Testi, L.; Torstensson,
K.; Veena, V. S.; Venegas, P.; Wang, K.; Wienen, M.
2021MNRAS.500.3064S Altcode: 2020arXiv201201527S; 2020MNRAS.tmp.2600S; 2020MNRAS.500.3064S
The SEDIGISM (Structure, Excitation and Dynamics of the Inner
Galactic Interstellar Medium) survey used the APEX telescope to map 84
deg2 of the Galactic plane between ℓ = -60° and +31°
in several molecular transitions, including 13CO (2 -
1) and C18O (2 - 1), thus probing the moderately dense
(∼103 cm-3) component of the interstellar
medium. With an angular resolution of 30 arcsec and a typical 1σ
sensitivity of 0.8-1.0 K at 0.25 km s-1 velocity resolution,
it gives access to a wide range of structures, from individual
star-forming clumps to giant molecular clouds and complexes. The
coverage includes a good fraction of the first and fourth Galactic
quadrants, allowing us to constrain the large-scale distribution of
cold molecular gas in the inner Galaxy. In this paper, we provide an
updated overview of the full survey and the data reduction procedures
used. We also assess the quality of these data and describe the data
products that are being made publicly available as part of this First
Data Release (DR1). We present integrated maps and position-velocity
maps of the molecular gas and use these to investigate the correlation
between the molecular gas and the large-scale structural features
of the Milky Way such as the spiral arms, Galactic bar and Galactic
Centre. We find that approximately 60 per cent of the molecular
gas is associated with the spiral arms and these appear as strong
intensity peaks in the derived Galactocentric distribution. We also
find strong peaks in intensity at specific longitudes that correspond
to the Galactic Centre and well-known star-forming complexes, revealing
that the 13CO emission is concentrated in a small number
of complexes rather than evenly distributed along spiral arms.

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Title: Stellar feedback and triggered star formation in the
prototypical bubble RCW 120
Authors: Luisi, M.; Anderson, L.; Schneider, N.; Simon, R.; Kabanovic,
S.; Guesten, R.; Zavagno, A.; Broos, P.; Buchbender, C.; Guevara,
C.; Jacobs, K.; Justen, M.; Klein, B.; Linville, D.; Roellig, M.;
Russeil, D.; Stutzki, J.; Tiwari, M.; Townsley, L.; Tielens, A.
2021AAS...23713704L Altcode:
Radiative and mechanical feedback of massive stars regulates star
formation and galaxy evolution. Positive feedback triggers the creation
of new stars by collecting dense shells of gas, while negative feedback
disrupts star formation by shredding molecular clouds. Although
key to understanding star formation, their relative importance is
unknown. Here we report velocity-resolved observations from the SOFIA
legacy program FEEDBACK of the massive star-forming region RCW 120 in
the [CII] 1.9 THz fine-structure line, revealing a gas shell expanding
at 15 km/s. Complementary APEX CO J=3-2 345 GHz observations exhibit
a ring-structure of molecular gas, fragmented into clumps that are
actively forming stars. Our observations demonstrate that triggered star
formation can occur on much shorter timescales than hitherto thought
(&lt;0.15 Myr), suggesting that positive feedback operates on short
time periods.

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Title: Stellar feedback and triggered star formation in the
prototypical bubble RCW 120
Authors: Luisi, M.; Anderson, L.; Schneider, N.; Simon, R.; Kabanovic,
S.; Guesten, R.; Zavagno, A.; Broos, P.; Buchbender, C.; Guevara,
C.; Jacobs, K.; Justen, M.; Klein, B.; Linville, D.; Roellig, M.;
Russeil, D.; Stutzki, J.; Tiwari, M.; Townsley, L.; Tielens, A.
2021AAS...23711403L Altcode:
Radiative and mechanical feedback of massive stars regulates star
formation and galaxy evolution. Positive feedback triggers the creation
of new stars by collecting dense shells of gas, while negative feedback
disrupts star formation by shredding molecular clouds. Although
key to understanding star formation, their relative importance is
unknown. Here we report velocity-resolved observations from the SOFIA
legacy program FEEDBACK of the massive star-forming region RCW 120 in
the [CII] 1.9 THz fine-structure line, revealing a gas shell expanding
at 15 km/s. Complementary APEX CO J=3-2 345 GHz observations exhibit
a ring-structure of molecular gas, fragmented into clumps that are
actively forming stars. Our observations demonstrate that triggered star
formation can occur on much shorter timescales than hitherto thought
(&lt;0.15 Myr), suggesting that positive feedback operates on short
time periods.

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Title: Modeling Chemical Abundance Evolution in Dwarf Galaxies
Authors: Kwon, A. Y.; Anderson, L.; Kumar, S.
2021AAS...23714702K Altcode:
The abundance of elements within a galaxy can give a strong insight into
the physical processes that have occurred within the galaxy. Thus, an
important part of understanding galaxy evolution relies on knowing how
the chemical abundance in a galaxy has changed over time. However, there
is no way to retroactively observe the evolving chemical composition
of a galaxy, which is why we turn to the present day metallicities
of stars. Since stars were formed from the materials within the
galaxy, the metallicity of each star is somewhat representative
of the metallicity of the entire galaxy at the time the star was
formed. Using the observed metallicities of stars within a galaxy
and the measured star formation rate of the galaxy our model infers
parameters within the Chempy chemical evolution model (Rybizki et
al. 2017) to find not only the most likely chemical abundances over
time but also other important characteristics of the galaxy including
the outflow feedback fraction and SN1a time delay. When applied to a
simulated FIRE dwarf galaxy, our model was able to closely predict the
galaxy's chemical evolution, verifying the accuracy of our model. In
the future, we will apply the model to the Sculptor dwarf galaxy
and add in a metallicity variance parameter to better understand the
spread of elements within the galaxy. Overall, our model can serve as
a powerful tool in improving both the predicted metallicity evolution
and inferred galactic parameters of real dwarf galaxies.

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Title: Detecting HII Regions in the Outer Scutum-Centaurus Arm
Authors: Johnson, A.; Armentrout, W.; Anderson, L.; Bania, T.; Balser,
D.; Wenger, T.
2021AAS...23715310J Altcode:
There is relatively little known about Galactic star formation in the
outer edges of the Milky Way, particularly in the Outer Scutum-Centaurus
spiral arm (OSC). Lying about 15 kpc from the center of the Galaxy,
the OSC was discovered in 2011 and is the most distant molecular
spiral arm of the Milky Way. The OSC warps up to 4 degrees above the
Galactic plane and as a result, has been excluded from the scope of many
surveys of the Galactic plane, typically confined to a single degree
above or below the plane. The goal of our study is to identify radio
continuum from HII regions in the OSC in order to better understand the
population of high-mass star formation regions in the outer Galaxy. We
observed 12 HII Regions in the OSC using the Very Large Array at 10
GHz. Of our 12 targets, 7 are re-observations of undetected sources
from Armentrout et al. (2017). The remaining 5 targets are sources
without previously observed 10 GHz radio continuum data. We identify
10 GHz radio continuum associated with 7 of our OSC HII region targets
for the first time. Assuming one dominant ionizing source per HII
region, we assign spectral types from O9 to O5.5 for these sources,
depending on their distance and continuum intensity. The remaining
5 nondetections represent lower-mass (B-type) star-forming regions
below the sensitivity limit of our survey. These regions represent
very high-mass star formation on the outer edge of the Galaxy, where
densities and metallicities might be more similar to that of a much
younger Milky Way or lower mass galaxies like the Magellanic Clouds.

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Title: Oxygen Isotopes in Tree Cellulose Reveal Ecohydrological
Relationships in the Colorado Rocky Mountains
Authors: Brice, B.; Anderson, L.; Berkelhammer, M. B.; Mast, A.
2020AGUFMPP006..02B Altcode:
Oxygen isotopes in xylem water or cellulose can be useful as an
indicator of the moisture sources for trees in modern and paleo
contexts. In the snow-dominated high elevations of the Rocky Mountains,
the oxygen isotope ratio in the cellulose of conifer trees may provide
valuable information about the seasonal origins of tree water use,
which can be key to understanding how snowpack or summer rains have
varied through time and how this has affected tree growth. In this pilot
study, annual and sub-annual tree-ring cellulose isotopic measurements
from Picea engelmannii were compared with monthly meteoric oxygen
isotope measurements, precipitation amount (P) and temperature (T)
data to investigate the climate-proxy response and to refine the use
of wood cellulose oxygen isotopes as a hydroclimate proxy. Preliminary
results indicate that annual-ring cellulose generally coincides with
year-to-year variation of volume-weighted meteoric (p-weight) oxygen
isotopes between the years 2007-2016. The relationship among cellulose
oxygen isotopes, p-weight oxygen isotopes, and temperature is more
pronounced for the annual growing season average (May-Sep). Sub-annual
tree-ring increments indicate inter-annual differences between cellulose
oxygen isotope values and the timing of p-weight oxygen isotopes,
which may indicated tree-level discrimination between cool-season and
growing season source water depending on environmental conditions for
that year. The statistical relationship between sub-annual cellulose
oxygen isotopes and the climate variables (P and T) suggests that T is
an important control on tree-ring growth in May through August. May and
July P corresponds to the early portion of the growth ring, while August
P corresponds to late season growth. Our results indicate that there
is a connection between seasonal climate and oxygen isotope values
derived from tree-ring cellulose in high-elevation, snow-dominated
systems. An improved understanding of this relationship will assist
in proxy-refinement and contribute to robust future reconstructions
of hydroclimate.

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Title: A Reconstruction of Southcentral Alaska Late Holocene
Hydroclimate from Peatland Cellulose Oxygen Isotopes
Authors: Nash, B. C.; Jones, M.; Berkelhammer, M. B.; Anderson, L.
2020AGUFMPP0030003N Altcode:
The use of peat cellulose oxygen isotopes as a proxy for hydroclimate
has commonly been applied to a single species in Sphagnum-dominated
bogs; however, recent advances in the application of this proxy to
wetlands with diverse species, such as fens, broadens the scope of their
utility. Here we present a late-Holocene record of species-specific
cellulose oxygen isotopes (δ18Ocellulose)
from a 7-m peat core collected from a fen located on the Kenai
Peninsula in Southcentral Alaska. Plant macrofossils were categorized
(herbaceous, bryophytic, ligneous) and tallied (e.g., seeds, leaves)
for the size fraction &gt;250 µm, and select specimens were picked
for 14C dating to generate a chronology in conjunction
with 210Pb. Oxygen isotopic analysis was performed on
alpha cellulose extracted from moss (Sphagnum and brown mosses)
and sedge (Carex spp.) macrofossils that were separated prior to
cellulose extraction to account for unique fractionation factors
resulting from differences in plant physiology. Previous analyses
revealed that the moss δ18Ocellulose values
were ~2 ‰ lighter on average than sedge at the same site. Fen
surface water δ18O values fall on the global meteoric
water line, indicating they accurately reflect precipitation. The
average isotopic difference between modern plant cellulose and peatland
water (Δδ18Ocellulose-water) is 33.9 ± 1.2
‰. Lacustrine sediments with aquatic macrofossils (Chara oospores,
Daphnia ephippia, and chironomids) comprise the lower half of the core,
indicating a shallow pond persisted from ~10 ka to ~6 ka, when the pond
terrestrialized to a peatland. Between ~6 to 4 ka, sedge macrofossils
dominated, followed by a period when the system fluctuated between sedge
and Sphagnum, before transitioning back to sedge by ~2 ka. An abrupt
transition to Sphagnum peat occurred in the last several decades and
persists to present. The δ18Ocellulose values
during the past 3 kyr range from ~17 ‰ to ~21.5 ‰, with higher
values at the core top. The inferred bog water values between -12.5
‰ and -17 ‰ are consistent with modern precipitation values and
indicate that this record can be placed into the context of regional
synoptic-scale hydroclimate changes throughout the late-Holocene,
including variability in the strength and position of the Aleutian Low.

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Title: VizieR Online Data Catalog: Stellar parameters for 13196
Kepler dwarfs (Angus+, 2020)
Authors: Angus, R.; Beane, A.; Price-Whelan, A. M.; Newton, E.;
Curtis, J. L.; Berger, T.; van Saders, J.; Kiman, R.; Foreman-Mackey,
D.; Lu, Y.; Anderson, L.; Faherty, J. K.
2020yCat..51600090A Altcode:
We used the publicly available Kepler-Gaia DR2 crossmatched catalog to
combine the McQuillan+ (2014, J/ApJS/211/24) catalog of stellar rotation
periods, measured from Kepler light curves, with the Gaia DR2 catalog of
parallaxes, proper motions, and apparent magnitudes. (1 data file).

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Title: High-Mass Star Formation in the Far Outer Galaxy
Authors: Armentrout, W.; Anderson, L.; Frayer, D.; Balser, D.; Bania,
T.; Dame, T.; Wenger, T.
2020AAS...23620906A Altcode:
HII regions are the archetypical tracers of high-mass star
formation. Because of their high luminosities, they can be seen across
the entire Galactic disk from mid-infrared to radio wavelengths. A
uniformly sensitive survey of Galactic HII regions across the disk
would allow us to constrain the properties of Galactic structure
and star formation. We have cataloged over 8000 HII regions
and candidates in the WISE Catalog of Galactic HII Regions (<A
href="http://astro.phys.wvu.edu/wise">astro.phys.wvu.edu/wise</A>), but
only 2000 of these are confirmed HII regions. The work is ongoing, but
from our survey completeness limits and population synthesis modeling,
we predict there are nearly 10,000 HII regions in the Milky Way created
by a central star of type B2 or earlier. A population of especially
interesting HII regions trace the Outer Scutum-Centaurus spiral arm
(OSC), the most distant molecular spiral arm in the Milky Way. These
regions represent star formation at low densities and low metallicities,
similar to the conditions in galaxies like the Large Magellanic Cloud
or a much younger Milky Way. To date, we have detected high-mass star
formation at 17 locations in the OSC, with the most distant source
at 23.5 kpc from the Sun and 17 kpc from the Galactic Center. They
have molecular cloud masses up to 105 Msol
and central stellar types as early as O4. By comparing molecular and
stellar masses, we can begin to put constraints on the star formation
efficiency of these distant outer Galaxy sources. We map the ionized
gas using the Very Large Array at X-band in the D-configuration. We
map the 13CO, HCN, and HCO+ molecular gas emission using the
Argus array on the Green Bank Telescope, producing individual 5 arcmin
maps with 8 arcsec resolution and 0.5 K sensitivity in 20 minutes.

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Title: Unusual Galactic HII Regions at the Intersection of the
Central Molecular Zone and the Far Dust Lane
Authors: Anderson, L.
2020AAS...23621301A Altcode:
Sgr E is a star formation complex found toward the Galactic center that
consists of numerous discrete, compact HII regions. It is located at
the intersection between the Central Molecular Zone (CMZ) and the far
dust lane of the Galactic bar, similar to "hot spots" seen in external
Galaxies. Sgr E is unusual in that: 1) the individual Sgr E HII regions
all share similar radio luminosities and angular extents; 2) it has
the largest absolute radial velocity of any known Galactic HII region;
and 3) the individual Sgr E HII regions are deficient in ∼10μm
emission from polycyclic aromatic hydrocarbons. Green Bank Telescope
(GBT) radio recombination line observations allowed us to increase
the known membership of Sgr E to 20 HII regions, although the many
mid-infrared sources in the area indicates that there may be as many as
100 HII regions in Sgr E. Using APEX SEDIGISM 13CO 3-2 data,
we discover a 3.0×105 Solar mass molecular cloud associated
with Sgr E, but find no molecular or far-infrared concentrations at
the locations of the Sgr E HII regions. Far-infrared data and new
GBT NH3 observations both show that the dust and gas have
elevated temperatures relative to the dust and gas temperatures of
other known HII regions. Comparison with simulations indicates that
the Sgr E HII regions formed in the dust lane of the Galactic bar a
couple Myr ago and will overshoot the CMZ, crashing into the near dust
lane. We propose that the PDRs of the Sgr E HII regions were stripped
during its orbit about that Galactic center.

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Title: The Galactic HII Region Luminosity Function at Radio and
Infrared Wavelengths
Authors: Mascoop, J.; Anderson, L.; Makai, Z.; Armentrout, W.; Balser,
D.; Wenger, T.; Bania, T.
2020AAS...23633303M Altcode:
We determine the form of the Galactic HII region luminosity function
(LF) at multiple infrared and radio frequencies. The HII region LF has
been extensively studied in external galaxies, but has not received as
much attention in the Milky Way. Investigations of the Galactic HII
region LF have historically been limited by small sample sizes and
incompleteness at lower luminosities. We find that our sample of 797
first Galactic quadrant HII regions is complete for all HII regions
ionized by single O9.5 stars, and therefore provides an excellent
dataset to use for extragalactic comparisons. The data are best fit by
a single power law with an index of -1.73. There is little variation
in the power law index with frequency. We find agreement between our
result and previous studies in Hα, and therefore expect that future
LF studies at wavelengths less affected by extinction should find
similar results to those done in Hα. Many extragalactic LF studies
suggest that a more general form of the HII region LF is a double power
law. Such a form may reflect two physically distinct subpopulations;
previous studies suggest the break in the double power law occurs at the
transition between ionization- and density-bounded regions or regions
ionized by single and multiple stars. We find that the Galactic LF is
best fit by a single power law, even when it is divided into subsets
by heliocentric distance, Galactocentric radius, angular size, and
location relative to the spiral arms.

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Title: GDIGS and the Distribution of Diffuse Ionized Gas in the
Milky Way
Authors: Linville, D. J.; Anderson, L.; Luisi, M.
2020AAS...23633302L Altcode:
We present results from the Green Bank Telescope (GBT) Diffuse
Ionized Gas Survey (GDIGS), which traces ionized gas in the inner
Galactic plane by measuring radio recombination line (RRL) emission
between 4 and 8 GHz. The survey covers the area within 0.5 degrees
of the Galactic plane, from Galactic longitudes 32.3 degrees to
-5 degrees, but there are extensions above and below the plane in
select fields and extra coverage around W47 and W49. We automatically
Gaussian-decomposed the GDIGS Hydrogen RRL emission, and furthermore
separate the emission of diffuse ionized gas (DIG) from that of HII
regions. The height of the Gaussian serves as an indicator of emission
measure, while the full width at half maximum reflects temperature. Our
decompositions therefore allow us to explore how these properties
vary with Galactocentric radius, Galactic latitude, and Galactic
longitude. The velocities obtained from the decompositions also allow
us to construct longitude-velocity diagrams, which are informative of
the structure of the Milky Way and its spiral arms.

---------------------------------------------------------
Title: A VLA Census of the Galactic HII Region Population
Authors: Armentrout, W.; Anderson, L.; Wenger, T.; Balser, D.;
Bania, T.
2020AAS...23523603A Altcode:
The Milky Way contains a significant number of unconfirmed HII regions,
the archetypical tracers of Galactic high-mass star formation. There
are over 2000 confirmed HII regions in the Milky Way, but our Milky Way
surveys are deficient by several thousand HII regions when compared
to external galaxies with similar star formation rates. This is odd
given our close proximity to these Milky Way HII regions compared to
distant extragalactic sources. Through sensitive 9 GHz radio continuum
observations with the Jansky Very Large Array, we explore a faint
class of unconfirmed HII region candidates to put limits on the total
population of Galactic HII regions. We show that stars of spectral
type B2 create HII regions with similar infrared and radio continuum
morphologies as those HII regions created by O-stars. We achieve
this by measuring the peak and integrated radio flux densities from
these faint infrared-identified objects and comparing the inferred
Lyman continuum fluxes with spectral models of OB-stars. From our
50% detection rate of previously "radio quiet" sources from the WISE
Catalog of Galactic HII regions, we expect a lower limit of ~7000 HII
regions in our Galaxy. We have not yet discovered the vast majority
of the Milky Way's HII regions.

---------------------------------------------------------
Title: A Beam-Forming Receiver for the GBT at 23 GHz
Authors: Skipper, J.; Morgan, L.; Bandura, K.; Di Francesco, J.;
Lockman, J.; Armentrout, W.; Frayer, D.; Jensen, L.; O'Neil, K.;
White, S.; Anderson, L.; Araya, E. D.; Cazzoli, S.; Rosolowsky, E.;
Sadavoy, S.; Sahlen, M.; Tobin, J.
2020AAS...23545104S Altcode:
We are investigating the proposal to support the design, construction
and commissioning of a K-band (18-26 GHz) 256 element phased array
feed (PAF) receiver and associated beam-former capable of forming
225 independent beams (i.e. a 225 pixel spectroscopic camera), for
the 100m diameter Green Bank Telescope (GBT). The proposed receiver
will simultaneously observe the (1,1), (2,2), and (3,3) inversion
transitions of ammonia, a critically important probe of dense molecular
gas that can trace kinetic temperatures, optical depth and column
densities simultaneously with minimal bias. There are other molecular
tracers of star formation activity observable at this frequency band,
including CCS and HC7N, which act as 'chemical clocks' and thus can
distinguish between different modes of star formation (e.g. Seo et
al., 2019). Water masers are also strong emitters in the range of the
proposed receiver, tracing shocked gas and outflow motions in low- and
high-mass star-forming regions (see Walsh et al., 2011) in addition to
providing distance measurements to nearby active galaxies, yielding
a direct measurement of the Hubble constant, independent of standard
candles (Braatz et al., 2019). Furthermore, several radio recombination
lines, including hydrogen and carbon transitions between 63α and 70α,
will be observable, which will allow comprehensive studies of ionized
gas and photon-dominated regions in star-forming regions and planetary
nebulae.The GBT presents a 100m unblocked active surface, providing
a combination of higher gain, higher sensitivity and better angular
resolution at K-band than any other radio telescope. In comparison,
interferometers such as the Very Large Array (VLA) offer higher
angular resolution but simply do not have the sensitivity to large
scales needed to detect extended emission from dense clumps within
molecular clouds. The ∼32" angular resolution of the GBT at 23.7
GHz is well-matched to star-forming substructures in nearby clouds
(0.07 pc at 450 pc, the distance of Orion) and the field-of-view
of the instrument will surpass that of the 2' primary beam of the
VLA. This will provide excellent short-spacing data for combination
with interferometric observations, as well as make large area mapping
more efficient.

---------------------------------------------------------
Title: Modeling Color-Magnitude Diagrams with Bayesian Neural Flows
Authors: Cranmer, M.; Galvez, R.; Anderson, L.; Spergel, D.; Ho, S.
2020AAS...23538609C Altcode:
We demonstrate an algorithm for learning a flexible Color-Magnitude
Diagram (CMD) from noisy parallax and photometric measurements using
a normalizing flow, a deep neural network capable of learning an
arbitrary multi-dimensional probability distribution. Dust estimation
and dereddening is done iteratively inside the model and without prior
distance information, using the Bayestar map. Using this model, we
can improve Gaia distance estimates and also learn CMDs specific to a
particular stellar population. We conclude with a discussion of future
work, which exploits the normalizing flow architecture to allow us to
exactly marginalize over missing photometry, enabling the inclusion
of many surveys without losing coverage.

---------------------------------------------------------
Title: CubeSat active thermal management in support of cooled
electro-optical instrumentation for advanced atmospheric observing
missions
Authors: Anderson, L.; Swenson, C.; Davidson, R.; Mastropietro, A. J.;
Maghsoudi, E.; Luong, S.; Cappucci, S.; Mckinley, I.
2018SPIE10769E..07A Altcode:
The need for advanced cooled electro-optical instrumentation in remote
observations of the atmosphere is well known and demonstrated by SABER
on the TIMED mission. The relatively new use of small satellites
in remote earth observing missions as, well as the challenges, are
epitomized by the upcoming NOAA EON-IR 12U CubeSat missions. These
advanced CubeSat missions, which hope to accomplish scientific
objectives on the same scale as larger more traditional satellites,
require advanced miniaturized cryocoolers and active methods for thermal
management and power control. The active CryoCubeSat project (ACCS)
is a demonstration of such a technology. Utilizing Ultrasonic Additive
Manufacturing (UAM) techniques, a Mechanical Pumped Fluid Loop (MPFL),
and miniature pumps and cryocoolers to create a closed loop fluid-based
heat interchange system. The ACCS project creates a two-stage thermal
control system targeting 6U CubeSat platforms. The first stage is
composed of a miniature Ricor K508N cryocooler while the second is
formed by a UAM fabricated heat exchanger MPFL system powered by a micro
TCS M510 pump. The working fluid is exchanged between a built-in chassis
heat exchanger and a deployable tracking radiator. This work details
the theory design and testing of a relevant ground-based prototype and
the analysis and modeling of the results as well as the development
of a design tool to help in customized active thermal control designs
for small satellites. Ultimately, the ACCS project hopes to enable a
new generation of advanced CubeSat atmospheric observing missions.

---------------------------------------------------------
Title: The Romulus cosmological simulations: a physical approach to
the formation, dynamics and accretion models of SMBHs
Authors: Tremmel, M.; Karcher, M.; Governato, F.; Volonteri, M.;
Quinn, T. R.; Pontzen, A.; Anderson, L.; Bellovary, J.
2017MNRAS.470.1121T Altcode: 2016arXiv160702151T
We present a novel implementation of supermassive black hole (SMBH)
formation, dynamics and accretion in the massively parallel tree+SPH
code, ChaNGa. This approach improves the modelling of SMBHs in fully
cosmological simulations, allowing for a more detailed analysis of
SMBH-galaxy co-evolution throughout cosmic time. Our scheme includes
novel, physically motivated models for SMBH formation, dynamics and
sinking timescales within galaxies and SMBH accretion of rotationally
supported gas. The sub-grid parameters that regulate star formation (SF)
and feedback from SMBHs and SNe are optimized against a comprehensive
set of z = 0 galaxy scaling relations using a novel, multidimensional
parameter search. We have incorporated our new SMBH implementation and
parameter optimization into a new set of high-resolution, large-scale
cosmological simulations called Romulus. We present initial results
from our flagship simulation, Romulus25, showing that our SMBH model
results in SF efficiency, SMBH masses and global SF and SMBH accretion
histories at high redshift that are consistent with observations. We
discuss the importance of SMBH physics in shaping the evolution of
massive galaxies and show how SMBH feedback is much more effective
at regulating SF compared to SNe feedback in this regime. Further,
we show how each aspect of our SMBH model impacts this evolution
compared to more common approaches. Finally, we present a science
application of this scheme studying the properties and time evolution
of an example dual active galactic nucleus system, highlighting how
our approach allows simulations to better study galaxy interactions
and SMBH mergers in the context of galaxy-BH co-evolution.

---------------------------------------------------------
Title: High sensitivity of gross primary production in the Rocky
Mountains to summer rain
Authors: Berkelhammer, M.; Stefanescu, I. C.; Joiner, J.; Anderson, L.
2017GeoRL..44.3643B Altcode:
In the catchments of the Rocky Mountains, peak snowpack is declining
in response to warmer spring temperatures. To understand how
this will influence terrestrial gross primary production (GPP),
we compared precipitation data across the intermountain west with
satellite retrievals of solar-induced fluorescence (SIF), a proxy
for GPP. Annual precipitation patterns explained most of the spatial
and temporal variability of SIF, but the slope of the response was
dependent on site to site differences in the proportion of snowpack to
summer rain. We separated the response of SIF to different seasonal
precipitation amounts and found that SIF was approximately twice as
sensitive to variations in summer rain than snowpack. The response
of peak GPP to a secular decline in snowpack will likely be subtle,
whereas a change in summer rain amount will have precipitous effects on
GPP. The study suggests that the rain use efficiency of Rocky Mountain
ecosystems is strongly dependent on precipitation form and timing.

---------------------------------------------------------
Title: Nickel Distribution Between Immiscible Melts as a Means to
Understand the Influence of Ferric Iron on NiO Activity Coefficients
Authors: Colson, R. O.; Young, E.; Anderson, L.
2017LPI....48.1548C Altcode:
Distribution of NiO between two immiscible melts, NiO activity
coefficient, and the effects of ferric iron.

---------------------------------------------------------
Title: Artview: Artview Release 1.2.3
Authors: Nick; Anderson; Lang, Timothy; Helmus, Jonathan J.; your
git settings!, Check; Nesbitt, Steve
2016zndo.....47224N Altcode:
We are happy to announce the release of ARTview v1.2! Highlights
Restructing of Menu for easier use Introduction of modes -
predefined configurations that can be changed at run time Reconfigure
“`SelectRegion“` module Add new components: “`FileNavigator“`
and “`PointsDisplay“` Add new plugins: “`DirectoryList“`,
“`ManualFilter“`, “`ManualUnfold“`, “`AccessTerminal“` (Py-ART
1.6 compatilbility) Add support for new-style and legacy grids (Py-ART
1.6) Ability to use Py-ART configuration file for defining colormaps
Rename and redesign “`LinkPlugins“` to “`LinkSharedVariables“
Create conda package for easier installation (thanks Jonathan Helmus)
Drop official support for Python 2.6 Add video Tutorials for help

---------------------------------------------------------
Title: Detection of two power-law tails in the probability
distribution functions of massive GMCs.
Authors: Schneider, N.; Bontemps, S.; Girichidis, P.; Rayner, T.;
Motte, F.; André, P.; Russeil, D.; Abergel, A.; Anderson, L.;
Arzoumanian, D.; Benedettini, M.; Csengeri, T.; Didelon, P.; di,
Francesco J.; Griffin, M.; Hill, T.; Klessen, R. S.; Ossenkopf,
V.; Pezzuto, S.; Rivera-Ingraham, A.; Spinoglio, L.; Tremblin, P.;
Zavagno, A.
2015MNRAS.453L..41S Altcode: 2015arXiv150708869S
We report the novel detection of complex high column density tails
in the probability distribution functions (PDFs) for three high-mass
star-forming regions (CepOB3, MonR2, NGC 6334), obtained from dust
emission observed with Herschel. The low column density range can be
fitted with a lognormal distribution. A first power-law tail starts
above an extinction (AV) of ∼6-14. It has a slope of α 1.3-2 for
the &amp;ρ ≈ r-α profile for an equivalent density distribution
(spherical or cylindrical geometry), and is thus consistent with
free-fall gravitational collapse. Above AV ∼40, 60, and 140, we detect
an excess that can be fitted by a flatter power-law tail with α &gt;
2. It correlates with the central regions of the cloud (ridges/hubs) of
size ∼;1 pc and densities above 104 cm-3. This excess may be caused
by physical processes that slow down collapse and reduce the flow
of mass towards higher densities. Possible are: (1) rotation, which
introduces an angular momentum barrier, (2) increasing optical depth
and weaker cooling, (3) magnetic fields, (4) geometrical effects, and
(5) protostellar feedback. The excess/second power-law tail is closely
linked to high-mass star-formation though it does not imply a universal
column density threshold for the formation of (high-mass) stars.

---------------------------------------------------------
Title: All about baryons: revisiting SIDM predictions at small
halo masses
Authors: Fry, A. Bastidas; Governato, F.; Pontzen, A.; Quinn, T.;
Tremmel, M.; Anderson, L.; Menon, H.; Brooks, A. M.; Wadsley, J.
2015MNRAS.452.1468F Altcode: 2015arXiv150100497B
We use cosmological hydrodynamic simulations to consistently compare
the assembly of dwarf galaxies in both Λ dominated, cold dark matter
(CDM) and self-interacting dark matter (SIDM) models. The SIDM model
adopts a constant cross-section of 2 cm2 g-1,
a relatively large value to maximize its effects. These are the first
SIDM simulations that are combined with a description of stellar
feedback that naturally drives potential fluctuations able to create
dark matter (DM) cores. Remarkably, SIDM fails to significantly
lower the central DM density within the central 500 pc at halo peak
velocities Vmax &lt; 30 km s-1. This is due to
the fact that the central regions of very low mass field haloes have
relatively low central velocity dispersion and densities, leading
to time-scales for SIDM collisions greater than a Hubble time. CDM
haloes with Vmax &lt; 30 km s-1 have inefficient
star formation, and hence weak supernova feedback. At a fixed 2
cm2 g-1 SIDM cross-section, the DM content of
very low mass CDM and SIDM haloes differs by no more than a factor
of 2 within 100-200 pc. At larger halo masses (∼1010
M⊙), the introduction of baryonic processes creates field
dwarf galaxies with DM cores and central DM+baryon distributions that
are effectively indistinguishable between CDM and SIDM. Both models
are in broad agreement with observed Local Group field galaxies across
the range of masses explored. To significantly differentiate SIDM
from CDM at the scale of faint dwarf galaxies, a velocity-dependent
cross-section that rapidly increases to values larger than 2
cm2 g-1 for haloes with Vmax &lt;
25-30 km s-1 needs to be introduced.

---------------------------------------------------------
Title: Modeling NiO Activities in Silicate Melts Considering
Separate Contributions from Ni2+ and O2-: Dependence of O2- on Melt
Polymerization
Authors: Anderson, L.; Young, E.; Colson, R. O.
2015LPI....46.1358A Altcode: 2015LPICo1832.1358A
We propose a model for trace element oxide activities successful
for NiO. The activity of the oxide ion varies according to the
polymerization of the melt.

---------------------------------------------------------
Title: Worldwide Weather Radar Imagery May Allow Substantial Increase
in Meteorite Fall Recovery
Authors: Fries, M.; Matson, R.; Schaefer, J.; Fries, J.; Anderson, L.
2014LPICo1800.5443F Altcode:
Radars everywhere / Watching stones fall overseas / There's more than
you think.

---------------------------------------------------------
Title: SIGGMA: A Survey of Ionized Gas in the Galaxy, Made with the
Arecibo Telescope
Authors: Liu, B.; McIntyre, T.; Terzian, Y.; Minchin, R.; Anderson,
L.; Churchwell, E.; Lebron, M.; Anish Roshi, D.
2013AJ....146...80L Altcode: 2013arXiv1308.3122L
A Survey of Ionized Gas in the Galaxy, made with the Arecibo telescope
(SIGGMA), uses the Arecibo L-band Feed Array (ALFA) to fully sample
the Galactic plane (30° &lt;= l &lt;= 75° and -2° &lt;= b &lt;= 2°
175° &lt;= l &lt;= 207° and -2° &lt;= b &lt;= 1°) observable with
the telescope in radio recombination lines (RRLs). Processed data sets
are being produced in the form of data cubes of 2° (along l) × 4°
(along b) × 151 (number of channels), archived and made public. The
151 channels cover a velocity range of 600 km s-1 and the
velocity resolution of the survey changes from 4.2 km s-1
to 5.1 km s-1 from the lowest frequency channel to the
highest frequency channel. RRL maps with 3.'4 resolution and a line
flux density sensitivity of ~0.5 mJy will enable us to identify new
H II regions, measure their electron temperatures, study the physics
of photodissociation regions with carbon RRLs, and investigate the
origin of the extended low-density medium. Twelve Hnα lines fall
within the 300 MHz bandpass of ALFA; they are resampled to a common
velocity resolution to improve the signal-to-noise ratio (S/N) by
a factor of three or more and preserve the line width. SIGGMA will
produce the most sensitive fully sampled RRL survey to date. Here,
we discuss the observing and data reduction techniques in detail. A
test observation toward the H II region complex S255/S257 has detected
Hnα and Cnα lines with S/N &gt; 10.

---------------------------------------------------------
Title: Model based systems engineering (MBSE) applied to Radio Aurora
Explorer (RAX) CubeSat mission operational scenarios
Authors: Spangelo, S. C.; Cutler, J.; Anderson, L.; Fosse, E.;
Cheng, L.; Yntema, R.; Bajaj, M.; Delp, C.; Cole, B.; Soremekum, G.;
Kaslow, D.
2013aero.confE..81S Altcode:
Small satellites are more highly resource-constrained by mass, power,
volume, delivery timelines, and financial cost relative to their
larger counterparts. Small satellites are operationally challenging
because subsystem functions are coupled and constrained by the limited
available commodities (e.g. data, energy, and access times to ground
resources). Furthermore, additional operational complexities arise
because small satellite components are physically integrated, which
may yield thermal or radio frequency interference. In this paper, we
extend our initial Model Based Systems Engineering (MBSE) framework
developed for a small satellite mission by demonstrating the ability
to model different behaviors and scenarios. We integrate several
simulation tools to execute SysML-based behavior models, including
subsystem functions and internal states of the spacecraft. We
demonstrate utility of this approach to drive the system analysis
and design process. We demonstrate applicability of the simulation
environment to capture realistic satellite operational scenarios, which
include energy collection, the data acquisition, and downloading to
ground stations. The integrated modeling environment enables users to
extract feasibility, performance, and robustness metrics. This enables
visualization of both the physical states (e.g. position, attitude) and
functional states (e.g. operating points of various subsystems) of the
satellite for representative mission scenarios. The modeling approach
presented in this paper offers satellite designers and operators the
opportunity to assess the feasibility of vehicle and network parameters,
as well as the feasibility of operational schedules. This will enable
future missions to benefit from using these models throughout the
full design, test, and fly cycle. In particular, vehicle and network
parameters and schedules can be verified prior to being implemented,
during mission operations, and can also be updated in near real-time
with oper- tional performance feedback.

---------------------------------------------------------
Title: Color Distributions of Stars in the WISE Preliminary Data
Release
Authors: Hunt-Walker, Nicholas; Davenport, J. R. A.; Lewis, A. R.;
Ruan, J.; Anderson, L.; AlSayyad, Y.; Becker, A.; Ivezic, Z.
2012AAS...21915216H Altcode:
We present a preliminary characterization of the Galactic stellar
populations from the Wide-field Infrared Space Explorer (WISE)
Preliminary Data Release. We trace the main sequence color locus in
16 dimensions using a matched sample between IRAS, SDSS and 2MASS for
several million stars. This exquisite characterization of "normal”
stars enables efficient and robust searches for non-main-sequence
stars. For example, the excellent faint limit of WISE yields a sample of
AGB candidates using the 4.6, 12, and 22 micron bandpasses that exceeds
the IRAS AGB catalog by up to an order of magnitude. Our preliminary
analysis suggests that the WISE database will be a goldmine for studies
of Galactic stellar populations.

---------------------------------------------------------
Title: OT2_landerso_1: Tracing Galactic Metallicity with Herschel
Authors: Anderson, L.
2011hers.prop.1692A Altcode:
Galactic abundances trace the processing of primordial elements
by stars from the birth of the Milky Way to the present day. HII
regions, because of their short lifetimes, are ideal targets for
abundance determinations because they sample the current state of
the interstellar medium. We propose to observe the [OIII], [NIII],
and [NII] lines of 31 well-studied Galactic HII regions with the PACS
spectrometer to derive the oxygen and nitrogen abundances. We hope to
address two long-standing problems in Galactic abundance measurements:
1) abundances traced in the far-infrared show discrepancies with those
in the optical, and 2) HII region electron temperatures derived from
radio observations, which can be used as a proxy for metallicity,
are not well calibrated with abundance measurements.

---------------------------------------------------------
Title: Dust in molecular clumps from the Hi-GAL survey
Authors: Marshall, D. J.; Montier, L. A.; Ristorcelli, I.; Anderson,
L.; Bernard, J. P.; Brunt, C.; Martin, P.; Mottram, J.; Paradis, D.;
Rodon, J.
2010sf2a.conf..233M Altcode:
Dust properties in molecular clouds may give clues to the star formation
process.By using recent observations of dust and gas emission, we seek
to constrain the dust properties in discrete molecular clumps in the
plane of the Milky Way.Using observations of the interstellar gas,
we separate observed dust emission from the Hi-GAL survey, using the
Herschel Space Observatory, into discrete line of sight components. A
new dust spectral inversion technique is used where the dust emission
is assumed to be a linear sum of a finite number of components,
where the emission from each component follows a modified blackbody
emission law. We are able to obtain the dust properties in over 60
molecular clumps in a 4 square degree zone centred on l=30o,
b=0o. The dust in a few of the molecular clumps is found
to be warmer than the dust associated with the atomic phase of the
gas. This suggests that these clumps are not heated solely by the
interstellar radiation field, but also contain an internal heating
source suggesting the onset of an initial stage of star formation.

---------------------------------------------------------
Title: Clouds, filaments, and protostars: The Herschel Hi-GAL
Milky Way
Authors: Molinari, S.; Swinyard, B.; Bally, J.; Barlow, M.; Bernard,
J. -P.; Martin, P.; Moore, T.; Noriega-Crespo, A.; Plume, R.; Testi,
L.; Zavagno, A.; Abergel, A.; Ali, B.; Anderson, L.; André, P.;
Baluteau, J. -P.; Battersby, C.; Beltrán, M. T.; Benedettini,
M.; Billot, N.; Blommaert, J.; Bontemps, S.; Boulanger, F.; Brand,
J.; Brunt, C.; Burton, M.; Calzoletti, L.; Carey, S.; Caselli, P.;
Cesaroni, R.; Cernicharo, J.; Chakrabarti, S.; Chrysostomou, A.; Cohen,
M.; Compiegne, M.; de Bernardis, P.; de Gasperis, G.; di Giorgio,
A. M.; Elia, D.; Faustini, F.; Flagey, N.; Fukui, Y.; Fuller, G. A.;
Ganga, K.; Garcia-Lario, P.; Glenn, J.; Goldsmith, P. F.; Griffin,
M.; Hoare, M.; Huang, M.; Ikhenaode, D.; Joblin, C.; Joncas, G.;
Juvela, M.; Kirk, J. M.; Lagache, G.; Li, J. Z.; Lim, T. L.; Lord,
S. D.; Marengo, M.; Marshall, D. J.; Masi, S.; Massi, F.; Matsuura,
M.; Minier, V.; Miville-Deschênes, M. -A.; Montier, L. A.; Morgan,
L.; Motte, F.; Mottram, J. C.; Müller, T. G.; Natoli, P.; Neves,
J.; Olmi, L.; Paladini, R.; Paradis, D.; Parsons, H.; Peretto, N.;
Pestalozzi, M.; Pezzuto, S.; Piacentini, F.; Piazzo, L.; Polychroni,
D.; Pomarès, M.; Popescu, C. C.; Reach, W. T.; Ristorcelli, I.;
Robitaille, J. -F.; Robitaille, T.; Rodón, J. A.; Roy, A.; Royer,
P.; Russeil, D.; Saraceno, P.; Sauvage, M.; Schilke, P.; Schisano,
E.; Schneider, N.; Schuller, F.; Schulz, B.; Sibthorpe, B.; Smith,
H. A.; Smith, M. D.; Spinoglio, L.; Stamatellos, D.; Strafella,
F.; Stringfellow, G. S.; Sturm, E.; Taylor, R.; Thompson, M. A.;
Traficante, A.; Tuffs, R. J.; Umana, G.; Valenziano, L.; Vavrek, R.;
Veneziani, M.; Viti, S.; Waelkens, C.; Ward-Thompson, D.; White, G.;
Wilcock, L. A.; Wyrowski, F.; Yorke, H. W.; Zhang, Q.
2010A&A...518L.100M Altcode: 2010arXiv1005.3317M
We present the first results from the science demonstration phase
for the Hi-GAL survey, the Herschel key program that will map the
inner Galactic plane of the Milky Way in 5 bands. We outline our
data reduction strategy and present some science highlights on the
two observed 2° × 2° tiles approximately centered at l = 30° and
l = 59°. The two regions are extremely rich in intense and highly
structured extended emission which shows a widespread organization in
filaments. Source SEDs can be built for hundreds of objects in the two
fields, and physical parameters can be extracted, for a good fraction
of them where the distance could be estimated. The compact sources
(which we will call cores' in the following) are found for the most
part to be associated with the filaments, and the relationship to
the local beam-averaged column density of the filament itself shows
that a core seems to appear when a threshold around AV ~
1 is exceeded for the regions in the l = 59° field; a AV
value between 5 and 10 is found for the l = 30° field, likely due
to the relatively higher distances of the sources. This outlines an
exciting scenario where diffuse clouds first collapse into filaments,
which later fragment to cores where the column density has reached a
critical level. In spite of core L/M ratios being well in excess of a
few for many sources, we find core surface densities between 0.03 and
0.5 g cm-2. Our results are in good agreement with recent
MHD numerical simulations of filaments forming from large-scale
converging flows. Herschel is an ESA space observatory with
science instruments provided by European-led Principal Investigator
consortia and with important participation from NASA.

---------------------------------------------------------
Title: Galactic cold cores: Herschel study of first Planck detections
Authors: Juvela, M.; Ristorcelli, I.; Montier, L. A.; Marshall, D. J.;
Pelkonen, V. -M.; Malinen, J.; Ysard, N.; Tóth, L. V.; Harju, J.;
Bernard, J. -P.; Schneider, N.; Verebélyi, E.; Anderson, L.; André,
P.; Giard, M.; Krause, O.; Lehtinen, K.; Macias-Perez, J.; Martin,
P.; McGehee, P. M.; Meny, C.; Motte, F.; Pagani, L.; Paladini, R.;
Reach, W.; Valenziano, L.; Ward-Thompson, D.; Zavagno, A.
2010A&A...518L..93J Altcode:
Context. We present the first results from the project Galactic
cold cores, where the cold interstellar clouds detected by the Planck
satellite are studied with Herschel photometric observations. The final
Planck catalogue is expected to contain several thousand sources. The
Herschel observations during the science demonstration phase provided
the first glimpse into the nature of these sources. Aims: The
main goal of the project is to derive the physical properties of the
cold core population revealed by Planck. We examine three fields and
confirm the Planck detections with Herschel data, which we also use
to establish the evolutionary stage of the identified cores. 
Methods: We study the morphology and spectral energy distribution
of the sources using the combined wavelength coverage of Planck and
Herschel. The dust colour temperatures and emissivity indices are
determined. The masses of the cores are determined with distance
estimates which are taken from the literature and are confirmed by
kinematic and extinction information. Results: The observations
reveal extended regions of cold dust with dust colour temperatures
down to Tdust ~ 11 K. The fields represent different
evolutionary stages ranging from a quiescent, cold filament in Musca
to regions of active star formation in Cepheus. Conclusions:
The Herschel observations confirm that the all-sky survey of Planck
is capable of making a large number of new cold core detections. Our
results suggest that many of the sources may already have left the
pre-stellar phase or are at least closely associated with active
star formation. High-resolution Herschel observations are needed to
establish the true nature of the Planck detections. Planck (<A
href="http://www.esa.int/Planck">http://www.esa.int/Planck</A>) is a
project of the European Space Agency - ESA - with instruments provided
by two scientific consortia funded by ESA member states (in particular
the lead countries: France and Italy) with contributions from NASA
(USA), and telescope reflectors provided in a collaboration between
ESA and a scientific Consortium led and funded by Denmark.Herschel
is an ESA space observatory with science instruments provided by
European-led Principal Investigator consortia and with important
participation from NASA.

---------------------------------------------------------
Title: Commissioning the Spectrographs for the Baryon Oscillation
Spectroscopic Survey (BOSS)
Authors: Bhardwaj, Vaishali; Dawson, K.; Anderson, L.; Bizyaev,
D.; Brewington, H.; Brown, P.; Eisenstein, D. J.; Harding, P.;
Malanushenko, E.; Malanushenko, V.; Maraston, C.; Olmstead, M.;
Oravetz, D.; Pan, K.; Roe, N.; Schlegel, D. J.; Shelden, A.; Simmons,
A.; Snedden, S.; Stromback, G.
2010AAS...21547102B Altcode: 2010BAAS...42..517B
The Baryon Oscillation Spectroscopic Survey (BOSS) on the Sloan
Telescope will map 1.4 million galaxies at z &lt; 0.7 and 160,000
QSOs at 2.2 &lt; z &lt; 3.5. Operations began in September 2009 and
will continue through June 2014. BOSS features rebuilt spectrographs
that improve the throughput and extend the wavelength coverage to span
3600 to 10,000 Ang. We report on the commissioning of the spectroscopic
system.

---------------------------------------------------------
Title: An Algorithm for the Simultaneous Solution of Thousands of
Transfer Equations under Global Constraints
Authors: Anderson, Lawrence S.
2009nrt..book..163A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Speckle Imaging with an Electron-multiplying CCD Camera at
the WIYN Telescope
Authors: Horch, Elliott; Anderson, L.; DeSousa, M.; van Altena, W. F.
2009DDA....40.1604H Altcode:
Electron-multiplying CCD (EMCCD) cameras have extremely strong
characteristics for speckle imaging including high quantum efficiency,
extremely low effective read noise, and high bandwidth. We report on
our first results for binary star astrometry and photometry using an
Andor iXon EMCCD at the WIYN 3.5-m Telescope at Kitt Peak. We find
that diffraction-limited image reconstructions can be achieved to
approximately 15th magnitude and that the device appears to deliver
reliable differential photometry of the components of binary star
systems. Some implications for stellar astrophysics are discussed.

---------------------------------------------------------
Title: Milky Way HII Regions: From A GLIMPSE To A Stare
Authors: Bania, Thomas M.; Anderson, L.
2008AAS...212.1801B Altcode: 2008BAAS...40..212B
The completion of the SPITZER Legacy GLIMPSE survey, the BU-FCRAO
13-CO Galactic Ring Survey (GRS), the HI VLA Galactic Plane Survey
(VGPS), the Multi-Array Galactic Plane Imaging Survey (MAGPIS), and
the imminent release of the SPITZER Legacy MIPSGAL survey together
enable for the first time a multi-wavelength analysis of the physical
properties and evolutionary state of a large sample of inner Galaxy
HII regions. Existing radio recombination line surveys show that
nearly 300 HII regions are located in the zone where GLIMPSE and GRS
overlap. Most of the sources are not optically visible. The HII region
radio recombination line position and velocity targets a location
where GRS 13-CO and MAGPIS/VGPS 20/21 cm continuum images show the
distribution and relative geometry of molecular and ionized gas. The
SPITZER GLIMPSE and MIPSGAL mid-infrared mosaic images reveal the highly
embedded star cluster that ionizes the nebula, probe the distribution of
the warm dust, and trace the polycyclic aromatic hydrocarbon emission
from the photo-dissociation region that lies between the molecular and
ionized zones. The VGPS HI survey is critical to this effort because
HI absorption against the thermal continuum from the HII region can
be used to resolve the kinematic distance ambiguity. Knowing the
distance, one can derive the intrinsic physical properties of the
nebula, turning column densities and line intensities into masses
and luminosities. Compiling the physical properties of the ionized,
atomic, and molecular components of this large sample of star forming
regions in all stages of evolution and line of sight geometries will
provide a fundamental database for studies of the evolution of the
interstellar medium and the Giant Molecular Cloud/HII region/Star
Cluster/Supernova Bubble life-cycle. Here we give several case study
examples of individual Galactic HII regions.

---------------------------------------------------------
Title: Tracing Ghost Cavities with Low Frequency Radio Observations
Authors: Clarke, T.; Blanton, E.; Sarazin, C. L.; Kassim, N.; Anderson,
L.; Schmitt, H.; Gopal-Krishna; Neumann, D. M.
2007hvcg.conf..124C Altcode: 2006astro.ph.12595C
We present X-ray and multi-frequency radio observations of the central
radio sources in several X-ray cavity systems. We show that targeted
radio observations are key to determining if the lobes are being
actively fed by the central AGN. Low frequency observations provide
a unique way to study both the lifecycle of the central radio source
as well as its energy input into the ICM over several outburst episodes.

---------------------------------------------------------
Title: Tracing AGN Outbursts in Clusters Cores using X-ray and Low
Frequency Radio Observations
Authors: Clarke, Tracy E.; Blanton, E.; Sarazin, C.; Kassim, N.;
Anderson, L.
2006HEAD....9.1331C Altcode: 2006BAAS...38..371C
X-ray observations of the thermal gas in the central regions of cooling core clusters have revealed spectacular details of the interactions between the central radio sources and the surrounding thermal intracluster medium. In addition to depressions and filaments
associated with the active central radio source, there are a
number of cases of 'ghost cavities' in the thermal gas which may
trace buoyant lobes from past radio outbursts. The ghost cavities
provide details on the lifecycle of the central radio sources as
well as their energy input into the ICM. We present a detailed
X-ray and multi-frequency radio analysis of the central radio
sources in several of these ghost cavity systems. Our new low
frequency radio observations allow us to trace multiple cycles
of radio outbursts and reveal evidence of radio emission filling
X-ray tunnels in both Abell 2597 and Abell 262. Basic research in
radio astronomy at the NRL is supported by the Office of Naval Research.

---------------------------------------------------------
Title: XRF 020427: sudden ionospheric disturbance (SID).
Authors: Fishman, G. J.; Woods, P. M.; Hossfield, C.; Anderson, L.
2002GCN..1394....1F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A New Improved Balloon System at ESRANGE
Authors: Anderson, L.
1997ESASP.397..439A Altcode: 1997erbp.conf..439A
No abstract at ADS

---------------------------------------------------------
Title: Solar and Stellar Atmospheres in the Graduate Curriculum
Authors: Anderson, L. S.
1996AAS...188.3205A Altcode: 1996BAAS...28..867A
The study of semi-infinite radiating media has reached a critical stage
in its development. Back in Eddington's day, analytic theory blossomed
and set seed for the present, with fertilization from quantum mechanics
and stellar spectroscopy. In the 1970's, computers became powerful
enough to integrate all the interactions of radiation with cosmic
plasmas in simple geometries. Today, the classical atmosphere problem,
consisting of atoms and molecules stratified in a simple one-dimensional
geometry and in hydrostatic and radiative equilibrium with a constant
radiative luminosity, essentially has been solved. Such model solutions
can (or should) be found for most of the HR Diagram with a little
exploration of the internet. Because of this completion of a global
problem, work in the field has fragmented. The classical models are
pretty good at matching today's high signal-to-noise observations. The
failures of the models cannot be as easily classified as the original
stellar spectra the models were designed to match. These failures vary
between individual stars and/or small classes of stars by as much as
the error itself, so it is harder to make general statements and for
workers to compare results. The non-classical physics in one area of the
HR Diagram might be completely different from that of a nearby area,
or even from one star to the next in the same area. How do we train
today's students to approach this scattered disparity? How do we excite
students to carry on in the steps of Eddington, Mihalas, Kurucz, and the
many other contributors to the solution of the classical problem? What,
if any, are the outstanding problems of global significance? Our tools
are extremely powerful; any department or personal workstation can do
the work of yesterday's Cray, and the supercomputers today can take
on the challenge of multi-dimentional moving media.

---------------------------------------------------------
Title: Infrared line emission in 10 Lacertae.
Authors: Murdoch, K. A.; Drew, J. E.; Anderson, L. S.
1994A&A...284L..27M Altcode:
We report the presence of Brα and Brγ emission features in the
infrared spectrum of the O9V MK standard star 10 Lac. Waters et
al. (1993) have reported similar emission in the spectrum of the
B0.2V star τ Sco and have suggested that the emission is from a
low-density disk and that τ Sco is a mild, pole-on member of the
Be class of stars. We argue that such emission features arise as a
natural consequence of the structure of these stars'outer atmospheres,
thus eliminating the need to introduce departures from spherical
symmetry. Indeed, theoretical Brα and Brγ line profiles calculated
using stellar parameters derived from 10 Lac by Grigsby et al. (1992)
show a striking similarity to our observations

---------------------------------------------------------
Title: A Determination of the Basic Atmospheric Parameters of phi
Cassiopeiae
Authors: Rosenzweig, Patricia; Anderson, Lawrence
1993ApJ...411..207R Altcode:
By constructing non-LTE spherical model atmospheres, we have calculated
a theoretical distribution of the emergent radiation that best matches
the observed distribution of the supergiant Phi Cas, and so derived
its effective temperature, surface gravity, and radius. Since Phi
Cas is very likely a member of the open cluster NGC 457, we made
extinction corrections using the extinction determined for this
cluster by Rosenzweig and Morrison (1986). Moreover, the theoretical
atmospheres used for the comparison are line-blanketed models in
hydrostatic and radiative equilibrium. Several tests have demonstrated
that the models are reliable. The comparison of the observed UV and
visible energy distributions and the H-delta, Ca II K, and Mg II h and
k line profiles with the theoretical results indicates that the best
model for Phi Cas has T(eff) = 7200 +/- 100 K, log g = 0.4 +/- 0.1,
and R* = 263 +/- 34 R(solar). These results imply a mass of 6.3 +/-
3.6 solar masses, which is lower than but within the error of the mass
of the main-sequence turnoff point in NGC 457.

---------------------------------------------------------
Title: PAM: a Code for Non-LTE Line Blanketed Atmospheres
Authors: Anderson, L. S.
1992ASPC...26..509A Altcode: 1992csss....7..509A
No abstract at ADS

---------------------------------------------------------
Title: Non--LTE, Line-blanketed Model Atmospheres for Late O- and
Early B-Type Stars
Authors: Grigsby, James A.; Morrison, Nancy D.; Anderson, Lawrence S.
1992ApJS...78..205G Altcode:
The use of non-LTE line-blanketed model atmospheres to analyze the
spectra of hot stars is reported. The stars analyzed are members of
clusters and associations, have spectral types in the range O9-B2
and luminosity classes in the range III-IV, have slow to moderate
rotation, and are photometrically constant. Sampled line opacities
of iron-group elements were incorporated in the radiative transfer
solution; solar abundances were assumed. Good to excellent agreement
is obtained between the computed profiles and essentially all the line
profiles used to fix the model, and reliable stellar parameters are
derived. The synthetic M II 5581 equivalent widths agree well with
the observed ones at the low end of the temperature range studied,
but, above 25,000 K, the synthetic line is generally stronger than the
observed line. The behavior of the observed equivalent widths of N II,
N III, C II and C III lines as a function of Teff is studied. Most
of the lines show much scatter, with no consistent trend that could
indicate abundance differences from star to star.

---------------------------------------------------------
Title: Line Blanketing Without LTE - the Effect on Diagnostics for
B-Type Stars
Authors: Anderson, L.; Grigsby, J. A.
1991ASIC..341..365A Altcode: 1991sabc.conf..365A
No abstract at ADS

---------------------------------------------------------
Title: The photosphere as a radiative boundary.
Authors: Anderson, Lawrence S.; Avrett, Eugene H.
1991sia..book..670A Altcode:
The authors review the role of the photosphere as a radiative
boundary for the solar interior, concentrating on semi-empirical and
a priori models for the structure and emergent radiation. Contents:
1. Introduction. 2. Plane-parallel models. 3. Departures from
plane-parallel structure. 4. Dynamical convection models.

---------------------------------------------------------
Title: Line Blanketing Without Lts - Simple and Complex Spectra
Authors: Anderson, L.
1991ASIC..341...29A Altcode: 1991sabc.conf...29A
No abstract at ADS

---------------------------------------------------------
Title: Non-LTE line blanketing with elements 1 - 28.
Authors: Anderson, Lawrence Sven
1990ASPC....7...77A Altcode: 1990phls.work...77A
The author reports on the status of a continuing effort to calculate
non-LTE models of stellar atmospheres including the blanketing of
several million atomic transitions. In addition to the multi-frequency /
multi-gray algorithm for solving many coupled equations of radiative
transfer, the author has developed two independent ways of statistically
treating the ensemble of transitions within an ion in non-LTE. The
millions of real transitions are reduced to about 800 model transitions
in 22 ions, well within the capabilities of the transfer algorithm. The
author presents a model for a main sequence B-type star with an
effective temperature of 25,000K, a surface gravity of 104cm
s-2, and solar abundances.

---------------------------------------------------------
Title: Chromospheric Thermal Equilibrium - Varying Effective
Temperature and Gravity
Authors: Anderson, L. S.
1990ASPC....9..110A Altcode: 1990csss....6..110A
No abstract at ADS

---------------------------------------------------------
Title: Model Solar Chromosphere with Prescribed Heating
Authors: Anderson, Lawrence S.; Athay, R. Grant
1989ApJ...346.1010A Altcode:
Computed model solar chromospheres for prescribed departures from
radiative equilibrium are specified in terms of the local mechanical
(nonradiative) heat input. The computations are fully non-LTE and
include millions of spectral lines. From the variety of models
considered, the requirements on the heat input for a positive
temperature gradient, dT/dh, in different layers of the chromosphere
are discussed. The derived radiative cooling function for different
models show that the cooling function is model-dependent. By comparing
the computed models with the Vernazza, Avrett, and Loeser (1981) models,
it is shown that the VAL-C model is characterized by a total heat flux
1.4 x 10 to the 7th ergs/sq cm/per sec, most of which is dissipated
near the base of the temperature plateau. Half of the radiation loss
is provided by Fe II, with Ca II, Mg II, and H playing important,
but secondary, roles. CO molecules and H(-) are of lesser importance
even near the temperature minimum, except in cases of minimal heating.

---------------------------------------------------------
Title: Line Blanketing without Local Thermodynamic Equilibrium. II. A
Solar-Type Model in Radiative Equilibrium
Authors: Anderson, Lawrence S.
1989ApJ...339..558A Altcode:
A statistical solution for the problem of non-LTE radiative transfer
in the millions of atomic transitions responsible for line blanketing
is proposed which takes into account the influence of scattering on
the atomic populations. A multifrequency/multigray algorithm is used
to analyze the thermal equilibrium. Although CO is shown to cool the
upper atmosphere to a boundary temperature of 2640 K, the molecule
has little influence in the region of the solar temperature minimum.

---------------------------------------------------------
Title: An Atlas of B-type Stellar Atmosphere Models with NonLTE
Line Blanketing
Authors: Anderson, L. S.
1989BAAS...21..742A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Chromospheric and Coronal Heating
Authors: Anderson, Lawrence S.; Athay, R. Grant
1989ApJ...336.1089A Altcode:
From computations for a theoretical model chromosphere matched to the
empirical model of Vernazza, Avrett, and Loeser published in 1981,
it is concluded that the required magnitude and mass dependence of the
heat input are compatible with heating by sound waves whose velocity
amplitude is near the sound speed. However, the required rate of
heat input per gram increases markedly at the top of the neutral
chromosphere, and a different form of heating appears necessary in
the corona and transition region.

---------------------------------------------------------
Title: A New Spherical, Non-LTE, Blanketed Model Stellar Atmosphere
for ø Cas(FOla)
Authors: Rosenzweig, P.; Anderson, L. S.
1988BAAS...20..698R Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Statistical Mechanics of Partially Ionized Stellar Plasmas:
The Planck-Larkin Partition Function, Polarization Shifts, and
Simulations of Optical Spectra
Authors: Dappen, Werner; Anderson, Lawrence; Mihalas, Dimitri
1987ApJ...319..195D Altcode:
We discuss a recent controversy about the Planck-Larkin partition
function, and present optical simulations of high-quality spectra
from laboratory hydrogen plasmas (Wiese, Kelleher, and Paquette) using
several partition function formalisms. We point out that the controversy
has arisen from a misunderstanding about the use of the Planck-Larkin
partition function. A Planck-Larkin cancellation may still have its
place in equations of state that are based on quantum-statistical
many-body theory (i.e., the "physical picture"). However, experimental
evidence shows that it is inconsistent to use the Planck-Larkin
partition function as the internal partition function in simple
models of reacting gases (i.e., the "chemical picture"). Moreover,
the more sophisticated equations of state of the physical picture
will have to be subjected to the same comparison with experimental
data. We also address the question of plasma polarization shifts of
bound-state energies. We discuss the static-screened Coulomb potential
(SSCP) as an atomic potential: from theoretical considerations and
observational constraints we conclude that it should not be used. The
only useful result of the SSCP potential its prediction of the number
of excited be obtained by alternative means, e.g., by an occupation
probability formalism.

---------------------------------------------------------
Title: Radiative Cooling in the Solar Chromosphere
Authors: Anderson, L. S.; Athay, R. G.
1987BAAS...19R.930A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Line blanketing without local thermodynamic equilibrium. I - A
hydrostatic stellar atmosphere with hydrogen, helium, and carbon lines
Authors: Anderson, L. S.
1985ApJ...298..848A Altcode:
A numerical code designed to calculate radiation transport and
atmospheric structure under the constraints of statistical equilibrium
in atomic transitions and radiative and hydrostatic equilibrium in
the medium has been applied to a stellar atmosphere with effective
temperature of 35,000 K and surface gravity of 10,000 cm/sq sec. The
calculation includes 93 bound-free transitions and 128 bound-bound
transitions (112 including radiative rates in 143 multiplet components)
between 83 states in 29 ions of nine cosmically abundant species. The
calculated depth-dependence of the electron temperature superficially
resembles that in local thermodynamic equilibrium (LTE), but the
ionization balance shifts toward higher ion states. The transition
dominating the thermodynamic equilibrium shifts from C III 977 A in
LTE to C IV 1548-1551 A in non-LTE, and the electron temperatures in
the upper atmosphere drop by 15 percent. In addition, the ultraviolet
continua with energies h-nu greater than 24 eV are from 5 to 100
times stronger in non-LTE. Little change in the hydrogen spectra from
previous non-LTE models occurs. The implications for spectral synthesis
and ionization in stellar winds are discussed.

---------------------------------------------------------
Title: A code for line blanketing without local thermodynamic
equilibrium.
Authors: Anderson, L. S.
1985ASIC..152..225A Altcode: 1985pssl.proc..225A
A numerical code has been written which is designed to
calculate radiation transport and atmospheric structure under the
constraints of statistical equilibrium in atomic transitions and
radiative and hydrostatic equilibrium in the medium. It uses a
multi-frequency/multi-grey algorithm which admits the inclusion of
many spectral lines in full statistical equilibrium. The program
can comfortably accept up to about 300 specific lines arising from
about 30 lower states and any number of continua. By way of example,
the author presents a model of a stellar atmosphere with effective
temperature 35000K and surface gravity 104cm s-2.

---------------------------------------------------------
Title: Frequency dependence of Q in the mantle underlying the shield
areas of eurasia
Authors: der, Z. A.; Lees, A. C.; Cormier, V. F.; Anderson, L.;
Burnetti, J.
1985tege.rept.....D Altcode:
In Part I the results of short and intermediate period data analyses
for the determination of a frequency dependent Q model of the mantle
under the shield areas of Eurasia are presented. The spectra of short
period P waves from nuclear explosions in the 1-8 Hz frequency range
give t* sub p = approx. 0.15-0.2 seconds. Part II presents analyses of
long period data. Long period multiple S and ScS phases observed in
northern Europe were analyzed to determine mantle attenuation in the
0.02 to 0.2 Hz range under the Eurasian shield. Two groups of events
are used: deep Far-Eastern earthquakes and large earthquakes near the
edges of the shield areas of Eurasia. Part III provides the Q model. A
large set of broad band data was analyzed to determine the frequency and
depth dependence of Q for P and S waves under the northern shield areas
of Eurasia. A wide range of techniques utilizing spectra, amplitude
ratios and waveform modeling were used to derive apparent and absolute
t* estimated for P and S waves covering the seismic band between 0.01
to 10 Hz. A supplement discusses methodologies for estimating t*(f)
from Short Period Body Waves and Regional Variations of t*(f) in the
United States.

---------------------------------------------------------
Title: Stellar images derived from rotation broadening : AW Ursae
Majoris.
Authors: Anderson, L.; Stanford, D.; Leininger, D.
1983ApJ...270..200A Altcode:
New spectroscopic observations of the W UMa star AW Ursae Majoris are
interpreted by retrieving the star's continuum Doppler redistribution
function through the Fourier deconvolution of broadened strong lines
by a standard flux profile, and the star's shape and surface brightness
distribution are derived. The graphical approach to rotation broadening
is briefly reviewed, and the implicit assumptions are stated. The
observations and data reduction method are described, and the assumption
that the locally emitted spectral profile is uniform over the stellar
surface is examined. The Doppler redistribution functions obtained
for AW UMa are consistently too narrow and asymmetric for the assumed
geometry of the system. It is concluded that a large fraction of the
primary component is covered with a solarlike plage centered on the
side away from the secondary, which radically alters the local line
equivalent widths.

---------------------------------------------------------
Title: Non-LTE Line Blanketing: A Code and Some Early Results
Authors: Anderson, L. S.
1982BAAS...14..921A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: X-rays and HZ Herculis
Authors: Anderson, L.
1981ApJ...244..555A Altcode:
A detailed calculation of the structural and radiant characteristics of
the X-ray-illuminated atmosphere of HZ Her is necessary before it is
possible to substract its contribution from the total light and study
the more subtle effects of nonuniform illumination and contributions
from other system components. It is shown that an X-ray-irradiated
atmosphere can be divided into four distinct zones. In order of
decreasing height, these zones are a nearly isothermal photosphere
strongly coupled to its own thermal radiation with additional heating
by hard X-ray photoionization and Compton scattering, and two sharp
transitions to a high-temperature corona in equilibrium with the
X-rays. The corona becomes gravitationally unbound a short distance
(compared to the binary separation) above the transition and expands
into a stellar wind. Both the lines and continuum observations, when
compared with emergent radiation calculations, are consistent with an
incident spectrum containing as much flux below hv = 1 keV as above hv =
1 keV.

---------------------------------------------------------
Title: On various criticisms of the contact discontinuity model
Authors: Shu, F. H.; Lubow, S. H.; Anderson, L.
1980ApJ...239..937S Altcode:
We discuss various criticisms raised recently by Lucy and Wilson,
by Papaloizou and Pringle, and by Smith, Robertson, and Smith against
the contact discontinuity model for contact binaries. In the process
we discover a promising means by which the filled fraction occupied by
the common envelope could, in principle, be determined mechanistically
for a contact binary of given total mass, angular momentum, initial
chemical composition, and age.

---------------------------------------------------------
Title: Comparison of Submillimeter and CO Brightness in Orion and
MONOCEROS-R2
Authors: Cudaback, D.; Anderson, L.; Lynch, D.; Smith, J.
1980IAUS...87..135C Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Rotation broadening and the shapes of W Ursae Majoris Stars
Authors: Anderson, L.; Raff, M.; Shu, F. H.
1980IAUS...88..485A Altcode:
Rotation broadening functions are extracted from the spectra of W
Ursae Majoris Stars. A fast Fourier transform is used to deconvolve
photographic spectra, covering some 500 A including dozens of strong
lines, with equivalent spectra from non-rotating stars of similar
spectral type. The resulting rotation functions contain information
about global features such as the shape of the stellar surface
(e.g. mass ratio and degree of contact), gravity brightening and
limb darkening. Preliminary data on the stars VW Cep and ER Vul are
presented. The rotation function of the former reveals the presence
of the third component found visually by Heintz (1975), while that of
the latter shows it to be detached and have mass ratio 0.9.

---------------------------------------------------------
Title: A theoretical atlas of light curves and rotation broadening
functions for contact binary stars.
Authors: Anderson, L.; Shu, F. H.
1979ApJS...40..667A Altcode:
Bolometric light curves and rotation broadening functions of contact
binaries are computed for a grid of values of mass ratio, filled
fraction, and orbital inclination, assuming three different extreme
combinations of gravity brightening and limb darkening. The results
are presented in a standard graphical format which is readily usable
for comparisons with observations.

---------------------------------------------------------
Title: On the structure of contact binaries. III. Mass and energy
flow.
Authors: Shu, F. H.; Lubow, S. H.; Anderson, L.
1979ApJ...229..223S Altcode:
A variety of topics dealing with the mass and energy flow in contact
binaries is examined. It is argued that the contact discontinuity
hypothesis proposed in earlier communications is both necessary
and sufficient to resolve Kuiper's (1941) paradox concerning the
existence of contact binaries with unequal components. A detailed
qualitative picture of the maintenance by fluid flow of the contact
and weak discontinuities of zero-order models in presented. This
discussion supplies a description of the mechanism by which the
interior luminosities are redistributed to give common envelope
luminosities. It also provides order-of-magnitude estimates for the
thickness of the transition layer and mixing region that constitute
the actual structure of the contact and weak discontinuities. The gas
dynamics of mass loss that occurs if stellar evolution should cause
a synchronously rotating common surface to try to expand beyond the
outer critical surface is calculated. The role of various processes
in the problem of the evolution of contact binaries is considered.

---------------------------------------------------------
Title: Rotation Broadening Functions of Selected W Ursae Majoris
Stars.
Authors: Anderson, L.; Raff, M.; Shu, F. H.
1979BAAS...11..438A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Nucleus-nucleus total cross sections for light nuclei at 1.55
and 2.89 GeV/c per nucleon
Authors: Jaros, J.; Wagner, A.; Anderson, L.; Chamberlain, O.; Fuzesy,
R. Z.; Gallup, J.; Gorn, W.; Schroeder, L.; Shannon, S.; Shapiro,
G.; Steiner, H.
1978PhRvC..18.2273J Altcode:
We have measured total cross sections for protons, dueterons,
α particles, and 12C on hydrogen, deuterium,
helium, and carbon targets at 1.55 and 2.89 GeV/c nucleon
using the "good geometry" transmission method. In addition,
we measured the inelastic cross sections and elastic slope
parameters for reactions initiated by deuterons, α particles,
and 12C. Our results are in good agreement with
Glauber theory predictions, but the factorization relation
σT(AA)=[σT(AB)]2σT(BB)
is not a good guide. We find
σT~=144(AT13-Ap13-1.48)2
mb and
σIN~=78(AT13+Ap13-1.25)2
mb, where AT(Ap) is the atomic mass number of the
target (projectile). NUCLEAR REACTIONS 12C(12C,
X), (α, X), (d, X), (p, X), E=0.87 and 2.10 GeV/nucleon; measured total
cross section, total inelastic cross section, and slope parameter of
elastic scattering.

---------------------------------------------------------
Title: The S19 Guidance System for Reduction of Sounding Rocket
Dispersion
Authors: Anderson, L.; Lundin, S.; Andersson, J.
1978ESASP.135..437A Altcode: 1978esrb.rept..437A
The S19 guidance system used to significantly reduce the impact
dispersion of sounding rockets is described. With the guidance system,
the main contributions to impact dispersion caused by wind errors and
thrust misalignment are reduced by a factor of up to ten depending
on the comparative unguided case. Therefore, the guidance system will
make it possible to launch sounding rockets to much higher altitudes at
restricted ranges and will reduce the stand-by time due to severe wind
conditions. The modular concept has the advantage that the guidance
system, with mirror changes, can be mounted on several different one-
or two-stage rockets without any modification of the rocket. Another
benefit is that the modular concept permits re-use, since the guidance
system can be recovered with the payload.

---------------------------------------------------------
Title: On the role of photospheric convection in W Ursae Majoris
stars.
Authors: Anderson, L.; Shu, F. H.
1978ApJ...221..926A Altcode:
We correct the derivation of the source function in the atmospheres
of contact binaries given in an earlier communication by Anderson and
Shu. This correction affects the cases when convection is present in
the photosphere. In our new treatment photospheric convection is more
efficient for reducing limb darkening. This result does not, however,
modify the numerical examples considered in our earlier paper. Subject
headings: convection - stars: W Ursae Majoris

---------------------------------------------------------
Title: New morphometric data for fresh lunar craters.
Authors: Wood, C. A.; Anderson, L.
1978LPSC....9.3669W Altcode:
Morphometric relations have been determined for 2598 fresh craters on
the lunar nearside using data given in the catalog of Wood and Andersson
(1978). For each of five principal morphological types, typified by
Albategnius C, Biot, Sosigenes, Triesnecker, and Tycho, statistical
relations are documented for the following: crater diameter and depth;
floor diameter and crater diameter; central peak height and crater
diameter; average wall slope and crater depth; central peak occurrence
and crater diameter; occurrence of scallops or terraces and crater
diameter. The first four relations generally confirm the conclusions
of Pike (1977), but the last two differ from results reported by Smith
and Sanchez (1973). Small (diameter less than 20 km) flat-floored
craters formed in mare terrains are as much as 10% deeper than those
formed in the highlands, and the depths of small bowl-shaped craters
reflect even greater dependence on terrain. Larger, scalloped-walled
craters are deeper in highland terrain than on the maria. Although
wall failure does not occur until the crater diameter reaches 13 km,
central peaks are found in flat floor craters as small as 2 km.

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Title: On the light curves of W Ursae Majoris stars.
Authors: Anderson, L.; Shu, F. H.
1977ApJ...214..798A Altcode:
We develop a physical theory for the light curves of contact binaries
based on the assumption that the dynamical time scale is very short
in comparison with the thermal time scale at the base of the common
envelope. In contrast with the case for common radiative envelopes,
the flux distribution in common convective envelopes does not exhibit
any effect of gravity brightening. Combined with a unified treatment
of reflection and limb darkening, this result produces Wtype light
curves for W UMa stars of spectral type later than F5 if the orbit
is inclined by less than approximately 70 90o. The sign of the
effect is in rough accord with the observations, but some discrepancy
remains concerning the magnitude of the effect. We speculate that the
interaction between rapid rotation and convection may contribute to
the remaining discrepancy; it may also produce the asymmetry and time
variability which are observed in some light curves. Subject headings:
stars: binaries - stars: W Ursae Majoris

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Title: The Minkowski Symposium and summer meeting of the Astronomical
Society of the Pacific.
Authors: Fawley, W.; Thorstensen, J.; Anderson, L.; Zook, A.
1977Mercu...6....6F Altcode:
No abstract at ADS

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Title: Stellar Atmospheres with Incident Radiation: HZ Herculis.
Authors: Anderson, L. S.
1977PhDT.........7A Altcode:
The solutions are presented for plane parallel, hydrostatic, radiative,
and statistical (non-LTE) equilibrium atmospheres with a variety of
incident spectra. The general structure is found to be qualitatively
similar to that of previous analyses. The irradiated atmosphere
divides onto four distinct zones. The condition that the luminosity
of Her X-1 is entirely due to matter overflowing the Roche lobe of HZ
Her and falling on a neutron star is sufficient to determine the gas
density at the gravitational saddle between the two stars. This density
corresponds almost exactly to the density at the top of the photosphere
in the irradiated atmosphere, implying that the transition zone is just
outside the saddlepoint. It is shown that the fact that the luminosity
of Her X-1 is about one-tenth of its Eddington luminosity is related
to this finding.

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Title: On the structure of contact binaries. I. The contact
discontinuity.
Authors: Shu, F. H.; Lubow, S. H.; Anderson, L.
1976ApJ...209..536S Altcode:
The problem of the interior structure of contact binaries is reviewed,
and a simple resolution of the difficulties which plague the theory
is suggested. It is proposed that contact binaries contain a contact
discontinuity between the lower surface of the common envelope and the
Roche lobe of the cooler star. This discontinuity is maintained against
thermal diffusion by fluid flow, and the transition layer is thin to
the extent that the dynamical time scale is short in comparison with
the thermal time scale. The idealization that the transition layer has
infinitesimal thickness allows a simple formulation of the structure
equations which are closed by appropriate jump conditions across
the discontinuity. The further imposition of the standard boundary
conditions suffices to define a unique model for the system once the
chemical composition, the masses of the two stars, and the orbital
separation are specified.

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Title: Statistical Equilibrium Models of the Atmosphere of HZ
Herculis.
Authors: Anderson, L.
1976BAAS....8..507A Altcode:
No abstract at ADS

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Title: On the Light Curves of W Ursae Majoris Stars.
Authors: Anderson, L.; Shu, F. H.
1976BAAS....8R.521A Altcode:
No abstract at ADS

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Title: Development of the S19 Guidance System for the Reduction of
Sounding-Rocket Dispersion
Authors: Anderson, L.; Anderson, J.
1976ESASP.115..497A Altcode: 1976epsr.conf..497A
No abstract at ADS

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Title: X-rays from degenerate stars. Part II.
Authors: Anderson, L.
1976Mercu...5....2A Altcode:
No abstract at ADS

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Title: X-rays from degenerate stars. Part I.
Authors: Anderson, L.
1976Mercu...5....6A Altcode:
No abstract at ADS

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Title: On the long-term behavior of the HZ Herculis/Hercules X-1
system.
Authors: Anderson, L.
1975ApJ...202..232A Altcode:
In accretion models for binary X-ray sources based on Roche-lobe
overflow, mass transfer from an otherwise normal, expanding star to a
collapsed companion is responsible for the production of X-rays. For
a range of time-averaged rates of mass transfer, the instantaneous
rate of transfer depends on the X-ray luminosity. Thus the rate
may be subject to a feedback instability. We propose that such an
instability is responsible for the long-period on-off behavior of HZ
Herculis. Subject headings: binaries - X-ray sources

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Title: The origin and history of the moon.
Authors: Anderson, L.
1974Moon...11..440A Altcode:
No abstract at ADS

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Title: Hydrodynamic Atmospheres for Companions of Binary X-ray Sources
Authors: Anderson, L.; Arons, J.
1974BAAS....6..280A Altcode:
No abstract at ADS

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Title: Hydrogen emission phenomena in T Tauri stars
Authors: Anderson, L.; Kuhi, L. V.
1969CoKon..65...93A Altcode: 1969nppv.conf...93A
No abstract at ADS