1,174 research outputs found
Resolving Star Formation on Sub-Kiloparsec Scales in the High-Redshift Galaxy SDP.11 Using Gravitational Lensing
We investigate the properties of the interstellar medium, star formation, and
the current-day stellar population in the strongly-lensed star-forming galaxy
H-ATLAS J091043.1-000321 (SDP.11), at z = 1.7830, using new Herschel and ALMA
observations of far-infrared fine-structure lines of carbon, oxygen and
nitrogen. We report detections of the [O III] 52 um, [N III] 57 um, and [O I]
63 um lines from Herschel/PACS, and present high-resolution imaging of the [C
II] 158 um line, and underlying continuum, using ALMA. We resolve the [C II]
line emission into two spatially-offset Einstein rings, tracing the red- and
blue-velocity components of the line, in the ALMA/Band-9 observations at 0.2"
resolution. The values seen in the [C II]/FIR ratio map, as low as ~ 0.02% at
the peak of the dust continuum, are similar to those of local ULIRGs,
suggesting an intense starburst in this source. This is consistent with the
high intrinsic FIR luminosity (~ 3 x 10^12 Lo), ~ 16 Myr gas depletion
timescale, and < 8 Myr timescale since the last starburst episode, estimated
from the hardness of the UV radiation field. By applying gravitational lensing
models to the visibilities in the uv-plane, we find that the lensing
magnification factor varies by a factor of two across SDP.11, affecting the
observed line profiles. After correcting for the effects of differential
lensing, a symmetric line profile is recovered, suggesting that the starburst
present here may not be the result of a major merger, as is the case for local
ULIRGs, but instead could be powered by star-formation activity spread across a
3-5 kpc rotating disk.Comment: 17 pages, 8 figures, 3 tables, accepted for publication in the
Astrophysical Journa
Galactic distribution of interstellar Al-26
A narrow cosmic gamma ray line at 1809 keV was discovered which was interpreted as resulting from the decay of approximately 3 M sub theta of Al-26 residing in the galactic disk. While its intrinsic width was unresolved by the HEAO 3 spectrometer, a (1 sigma) limit of 3 keV FWHM was obtained; this corresponds to bulk motions of v 250 km/s, which is consistent with material at rest in the ISM. Sites which have been suggested include type II supernovae and massive stars which are members of the extreme population I, as well as novae and red giants which are associated with an older disk population. The HEAO 3 data was used to distinguish between these two stellar populations
Calibration of Computational Models with Categorical Parameters and Correlated Outputs via Bayesian Smoothing Spline ANOVA
It has become commonplace to use complex computer models to predict outcomes
in regions where data does not exist. Typically these models need to be
calibrated and validated using some experimental data, which often consists of
multiple correlated outcomes. In addition, some of the model parameters may be
categorical in nature, such as a pointer variable to alternate models (or
submodels) for some of the physics of the system. Here we present a general
approach for calibration in such situations where an emulator of the
computationally demanding models and a discrepancy term from the model to
reality are represented within a Bayesian Smoothing Spline (BSS) ANOVA
framework. The BSS-ANOVA framework has several advantages over the traditional
Gaussian Process, including ease of handling categorical inputs and correlated
outputs, and improved computational efficiency. Finally this framework is then
applied to the problem that motivated its design; a calibration of a
computational fluid dynamics model of a bubbling fluidized which is used as an
absorber in a CO2 capture system
Baseline Evaluation of the DC Emergency Healthcare Coalition
The DC Healthcare Facilities Emergency Care Coalition, funded by a grant by the U.S. Department of Health and Human Services Assistant Secretary for Preparedness and Response (ASPR), was designed to significantly improve the state of emergency preparedness in health care facilities in the District of Columbia (DC), and to create a model for emergency preparedness that can be used by other large cities or regions of care across the nation. Its goal is to provide a comprehensive, uniform, and consistent framework and infrastructure for emergency preparedness across the full continuum of patient care. Devised to address the inconsistencies, shortcomings, fragmentations, and gaps present in current District hospital and healthcare facility emergency preparedness and response capabilities, the Coalition will achieve the following durable results and benefits for the District\u27s medical preparedness and response to a catastrophic event
A Spitzer Infrared Spectrograph Survey of Warm Molecular Hydrogen in Ultra-luminous Infrared Galaxies
We have conducted a survey of Ultra-luminous Infrared Galaxies (ULIRGs) with
the Infrared Spectrograph on the Spitzer Space Telescope, obtaining spectra
from 5.0-38.5um for 77 sources with 0.02<z <0.93. Observations of the pure
rotational H2 lines S(3) 9.67um, S(2) 12.28um, and S(1) 17.04um are used to
derive the temperature and mass of the warm molecular gas. We detect H2 in 77%
of the sample, and all ULIRGs with F(60um)>2Jy. The average warm molecular gas
mass is ~2x10^8solar-masses. High extinction, inferred from the 9.7um silicate
absorption depth, is not observed along the line of site to the molecular gas.
The derived H2 mass does not depend on F(25um)/F(60um), which has been used to
infer either starburst or AGN dominance. Similarly, the molecular mass does not
scale with the 25 or 60um luminosities. In general, the H2 emission is
consistent with an origin in photo-dissociation regions associated with star
formation. We detect the S(0) 28.22um emission line in a few ULIRGs. Including
this line in the model fits tends to lower the temperature by ~50-100K,
resulting in a significant increase in the gas mass. The presence of a cooler
component cannot be ruled out in the remainder of our sample, for which we do
not detect the S(0) line. The measured S(7) 5.51um line fluxes in six ULIRGs
implies ~3x10^6 solar-masses of hot (~1400K) H2. The warm gas mass is typically
less than 1% of the cold gas mass derived from CO observations.Comment: Accepted ApJ 01 September 2006, v648n1 issue. 14 pages 12 figures
IRAS 06361-6217 the f25/f60 ratio is 0.10 not 1.0
N-body simulations of galaxies and groups of galaxies with the Marseille GRAPE systems
I review the Marseille GRAPE systems and the N-body simulations done with
them. I first describe briefly the available hardware and software, their
possibilities and their limitations. I then describe work done on interacting
galaxies and groups of galaxies. This includes simulations of the formation of
ring galaxies, simulations of bar destruction by massive compact satellites, of
merging in compact groups and of the formation of brightest members in clusters
of galaxies.Comment: 13 pages, 5 figures, to be published in "Non-linear Dynamics and
Chaos in Astrophysics", eds. J.R. Buchler, S. Gottesman, J. Hunter and H.
Kandrup, Annals of the New York Academy of Science
Plasma and Warm Dust in the Collisional Ring Galaxy VIIZw466 from VLA and ISO Observations
We present the first mid-infrared (Mid-IR) (m) and radio
continuum (20,~6 and 3.6 cm) observations of the star-forming
collisional ring galaxy VII Zw 466 and its host group made with the Infrared
Space Observatory and the NRAO Very Large Array. A search was also made for CO
line emission in two of the galaxies with the Onsala 20m radio telescope and
upper limits were placed on the mass of molecular gas in those galaxies. The
ring galaxy is believed to owe its morphology to a slightly off-center
collision between an `intruder' galaxy and a disk. An off-center collision is
predicted to generate a radially expanding density wave in the disk which
should show large azimuthal variations in overdensity, and have observational
consequences. The radio continuum emission shows the largest asymmetry,
exhibiting a crescent-shaped distribution consistent with either the trapping
of cosmic-ray particles in the target disk, or an enhanced supernova rate in
the compressed region. On the other hand, the ISO observations (especially
those made at m) show a more scattered distribution, with
emission centers associated with powerful star formation sites distributed more
uniformly around the ring. Low-signal to noise observations at
m show possible emission inside the ring, with little emission
directly associated with the \ion{H}{2} regions. The observations emphasize the
complex relationship between the generation of radio emission and the
development of star formation even in relatively simple and well understood
collisional scenarios.Comment: Accepted for publication in The Astrophysical Journal, 23 pages + 6
PS figure
A thorough study of the intriguing X-ray emission from the Cartwheel ring
We present the results from the high resolution Chandra observation of the
Cartwheel galaxy. Many individual sources are resolved in the image, mostly
associated with the outer ring. All detected sources have a very high X-ray
luminosity ( erg s)that classifies them as Ultra Luminous
X-ray sources (ULX). The brightest of them is possibly the most luminous
individual non-nuclear source observed so far, with L erg
s (at D=122 Mpc). The spatial extent of this source is consistent with a
point source at the Chandra resolution. The luminosity function of individual
X-ray sources extends about an order of magnitude higher than previously
reported in other galaxies. We discuss this in the context of the "universal"
luminosity function for High Mass X-ray Binaries and we derive a Star Formation
Rate higher than in other starburst galaxies studied so far. A diffuse
component, associated with hot gas, is present. However, deeper observations
that we will obtain with XMM-Newton are needed to constrain its properties.Comment: 14 pages; accepted for publication in A&
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