136 research outputs found
Resolving the Interstellar Medium at the Peak of Cosmic Star Formation
The interstellar medium feeds both the formation of stars and the growth of
black holes, making it a key ingredient in the evolution of galaxies. With the
advent of the Atacama Large Millimeter/ submillimeter Array (ALMA), we can now
probe the interstellar medium within high-redshift galaxies in increasingly
exquisite detail. Our recent ALMA observations map the molecular gas and dust
continuum emission in sub-millimetre-selected galaxies on 1-5 kpc scales,
revealing significant differences in how the gas, dust continuum, and existing
stellar emission are distributed within the galaxies. This study demonstrates
the power of ALMA to shed new light on the structure and kinematics of the
interstellar medium in the early Universe, suggesting that the interpretation
of such observations is more complex than typically assumed.Comment: 4 pages, 5 figures, published on The Messenger, No. 173 (September
2018
Thallium-201 myocardial scintigraphy in the left bundle branch block patient : the importance of left ventricular size
Measuring the Effectiveness of the Communications Electronics Life Cycle Management Command (CE-LCMC) Internship Pilot Training Program
Joint Applied ProjectOver the next seven years, more than 50 percent of DoD’s acquisition workforce will be eligible for
retirement. To replace these highly skilled acquisition professionals, the Department of Defense (DoD) will need
to efficiently and effectively train employees who are entering the contracting profession. In 2003, the
Communications Electronics Life Cycle Management Command (CE-LCMC) established a pilot training program
that was intended to accelerate the training and development of contracting interns. The purpose of this study was
to examine the effectiveness of this program from the perspectives of the 91 participating interns, the Contracting
Officers who work with these interns, and the managers/supervisors in the Acquisition Center. Based on the
analysis of five surveys, recommendations are offered for the improvement of the CE-LCMC’s pilot intern
training program.http://archive.org/details/measuringeffecti109457604United States Army,United States Army,United States Arm
Extended Cold Molecular Gas Reservoirs in z~3.4 Submillimeter Galaxies
We report the detection of spatially resolved CO(1-0) emission in the z~3.4
submillimeter galaxies (SMGs) SMM J09431+4700 and SMM J13120+4242, using the
Expanded Very Large Array (EVLA). SMM J09431+4700 is resolved into the two
previously reported millimeter sources H6 and H7, separated by ~30kpc in
projection. We derive CO(1-0) line luminosities of L'(CO 1-0) = (2.49+/-0.86)
and (5.82+/-1.22) x 10^10 K km/s pc^2 for H6 and H7, and L'(CO 1-0) =
(23.4+/-4.1) x 10^10 K km/s pc^2 for SMM J13120+4242. These are ~1.5-4.5x
higher than what is expected from simple excitation modeling of higher-J CO
lines, suggesting the presence of copious amounts of low-excitation gas. This
is supported by the finding that the CO(1-0) line in SMM J13120+4242, the
system with lowest CO excitation, appears to have a broader profile and more
extended spatial structure than seen in higher-J CO lines (which is less
prominently seen in SMM J09431+4700). Based on L'(CO 1-0) and excitation
modeling, we find M_gas = 2.0-4.3 and 4.7-12.7 x 10^10 Msun for H6 and H7, and
M_gas = 18.7-69.4 x 10^10 Msun for SMM J13120+4242. The observed CO(1-0)
properties are consistent with the picture that SMM J09431+4700 represents an
early-stage, gas-rich major merger, and that SMM J13120+4242 represents such a
system in an advanced stage. This study thus highlights the importance of
spatially and dynamically resolved CO(1-0) observations of SMGs to further
understand the gas physics that drive star formation in these distant galaxies,
which becomes possible only now that the EVLA rises to its full capabilities.Comment: 6 pages, 4 figures, to appear in ApJL (EVLA Special Issue; accepted
May 19, 2011
An Analysis of ALMA Deep Fields and the Perceived Dearth of High-z Galaxies
Deep, pencil-beam surveys from ALMA at 1.1-1.3mm have uncovered an apparent
absence of high-redshift dusty galaxies, with existing redshift distributions
peaking around . This has led to a perceived dearth of dusty
systems at , and the conclusion, according to some models, that the early
Universe was relatively dust-poor. In this paper, we extend the backward
evolution galaxy model described by Casey et al. (2018) to the ALMA regime (in
depth and area) and determine that the measured number counts and redshift
distributions from ALMA deep field surveys are fully consistent with
constraints of the infrared luminosity function (IRLF) at determined by
single-dish submillimeter and millimeter surveys conducted on much larger
angular scales (deg). We find that measured 1.1-1.3mm number
counts are most constraining for the measurement of the faint-end slope of the
IRLF at . Recent
studies have suggested that UV-selected galaxies at may be particularly
dust-poor, but we find their millimeter-wave emission cannot rule out
consistency with the Calzetti dust attenuation law even by assuming relatively
typical, cold-dust (K) SEDs. Our models suggest that
the design of ALMA deep fields requires substantial revision to constrain the
prevalence of early Universe obscured starbursts. The most promising
avenue for detection and characterization of such early dusty galaxies will
come from future ALMA 2mm blank field surveys covering a few hundred
arcmin and the combination of existing and future dual-purpose 3mm
datasets.Comment: 21 pages, 12 figures, accepted for publication in Ap
Evidence for a clumpy, rotating gas disk in a submillimeter galaxy at z=4
We present Karl G. Jansky Very Large Array (VLA) observations of the CO(2-1)
emission in the z=4.05 submillimeter galaxy (SMG) GN20. These high-resolution
data allow us to image the molecular gas at 1.3 kpc resolution just 1.6 Gyr
after the Big Bang. The data reveal a clumpy, extended gas reservoir, 14 +/- 4
kpc in diameter, in unprecedented detail. A dynamical analysis shows that the
data are consistent with a rotating disk of total dynamical mass 5.4 +/- 2.4 X
10^11 M_sun. We use this dynamical mass estimate to constrain the CO-to-H_2
mass conversion factor (alpha_CO), finding alpha_CO=1.1 +/- 0.6 M_sun (K km
s^-1 pc^2)^-1. We identify five distinct molecular gas clumps in the disk of
GN20 with masses a few percent of the total gas mass, brightness temperatures
of 16-31K, and surface densities of >3,200-4,500 X (alpha_CO/0.8) M_sun pc^-2.
Virial mass estimates indicate they could be self-gravitating, and we constrain
their CO-to-H_2 mass conversion factor to be <0.2-0.7 M_sun (K km s^-1
pc^2)^-1. A multiwavelength comparison demonstrates that the molecular gas is
concentrated in a region of the galaxy that is heavily obscured in the
rest-frame UV/optical. We investigate the spatially-resolved gas excitation and
find that the CO(6-5)/CO(2-1) ratio is constant with radius, consistent with
star formation occuring over a large portion of the disk. We discuss the
implications of our results in the context of different fueling scenarios for
SMGs.Comment: 15 pages, 9 figures, accepted for publication in Ap
HI Density Distribution Driven by Supernovae: A Simulation Study
We model the complex distribution of atomic hydrogen (HI) in the interstellar
medium (ISM) assuming that it is driven entirely by supernovae (SN). We develop
and assess two different models. In the first approach, the simulated volume is
randomly populated with non-overlapping voids of a range of sizes. This may
relate to a snapshot distribution of supernova-remnant voids, although somewhat
artificially constrained by the non-overlap criterion. In the second approach,
a simplified time evolution (considering momentum conservation as the only
governing constraint during interactions) is followed as SN populate the space
with the associated input mass and energy.
We describe these simulations and present our results in the form of images
of the mass and velocity distributions and the associated power spectra. The
latter are compared with trends indicated by available observations. In both
approaches, we find remarkable correspondence with the observed statistical
description of well-studied components of the ISM, wherein the spatial spectra
have been found to show significant deviations from the Kolmogorov spectrum.
One of the key indications from this study, regardless of whether or not the
SN-induced turbulence is the dominant process in the ISM, is that the apparent
non-Kolmogorov spectral characteristics (of HI and/or electron column density
across thick or thin screens) needed to explain related observations may not at
all be in conflict with the underlying turbulence (i.e. the velocity structure)
being of Kolmogorov nature. We briefly discuss the limitations of our
simulations and the various implications of our results.Comment: To appear in Astrophysical Journal. 21 pages, 6 figure
An Exploratory Study to Understand Factors Associated with Health-related Quality of Life Among Uninsured/Underinsured Patients as Identified by Clinic Providers and Staff
Since the release of Healthy People 2020, there has been extensive research understanding factors associated with health-related quality of life (HRQoL) among specific populations. Despite this growing body of research, little has been conducted to understand the factors associated with HRQoL among uninsured/underinsured Americans. The purposes of the present study were to assess clinic staff to determine: (1) whether there is a need to examine HRQoL among uninsured/underinsured individuals, (2) whether there is a need for tailored HRQoL-promoting interventions among uninsured/underinsured individuals, and (3) the factors associated with HRQoL among uninsured/underinsured individuals. A survey was sent to an association of 41 clinics that provides free medical services to uninsured/underinsured individuals. The majority of participants indicated that uninsured/underinsured individuals experience unique factors associated with HRQoL and that there was a need to implement tailored HRQoL-improving interventions among uninsured/underinsured individuals. The results also present the personal/contextual factors associated with HRQoL of uninsured/underinsured individuals
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