25 research outputs found
ALMA Observations of Giant Molecular Clouds in the Starburst Dwarf Galaxy Henize 2-10
We present new CO(J=1-0) observations of Henize 2-10, a blue
compact dwarf galaxy about 8.7 Mpc away, taken with the Atacama Large
Millimeter Array. These are the highest spatial and spectral resolution
observations, to date, of the molecular gas in this starburst galaxy. We
measure a molecular mass of in Henize 2-10, and most of
the molecular gas is contained within a region having a size of about 310 pc.
We use the CPROPS algorithm to identify 119 resolved giant molecular clouds
distributed throughout the galaxy, and the molecular gas contained within these
clouds make up between 45 to 70% of the total molecular mass. The molecular
clouds in Henize 2-10 have similar median sizes (~26 pc), luminous masses (~ ), and surface densities (~ pc) to
Milky Way clouds. We provide evidence that Henize 2-10 clouds tend to be in
virial equilibrium, with the virial and luminous masses scaling according to
, similar to clouds in the Milky Way.
However, we measure a scaling relationship between luminous mass and size,
, that is steeper than what is observed in Milky
Way clouds. Assuming Henize 2-10 molecular clouds are virialized, we infer
values of the CO-to-H conversion factor ranging from 0.5 to 13 times the
standard value in the Solar Neighborhood. Given star formation efficiencies as
low as 5%, the most massive molecular clouds in Henize 2-10 currently have
enough mass to form the next generation of super-star clusters in the galaxy
The Global Structure of Molecular Clouds: I. Trends with Mass and Star Formation Rate
We introduce a model for the large-scale, global 3D structure of molecular
clouds. Motivated by the morphological appearance of clouds in surface density
maps, we model clouds as cylinders, with the aim of backing out information
about the volume density distribution of gas and its relationship to star
formation. We test our model by applying it to surface density maps for a
sample of nearby clouds and find solutions that fit each of the observed radial
surface density profiles remarkably well. Our most salient findings are that
clouds with higher central volume densities are more compact and also have
lower total mass. These same lower-mass clouds tend to have shorter gas
depletion times, regardless of whether we consider their total mass or dense
mass. Our analyses lead us to conclude that cylindrical clouds can be
characterized by a universal structure that sets the timescale on which they
form stars.Comment: Accepted to ApJ. 12 pages, 9 figure
A Model Connecting Galaxy Masses, Star Formation Rates, and Dust Temperatures Across Cosmic Time
We investigate the evolution of dust content in galaxies from redshifts z=0
to z=9.5. Using empirically motivated prescriptions, we model galactic-scale
properties -- including halo mass, stellar mass, star formation rate, gas mass,
and metallicity -- to make predictions for the galactic evolution of dust mass
and dust temperature in main sequence galaxies. Our simple analytic model,
which predicts that galaxies in the early Universe had greater quantities of
dust than their low-redshift counterparts, does a good job at reproducing
observed trends between galaxy dust and stellar mass out to z~6. We find that
for fixed galaxy stellar mass, the dust temperature increases from z=0 to z=6.
Our model forecasts a population of low-mass, high-redshift galaxies with
interstellar dust as hot as, or hotter than, their more massive counterparts;
but this prediction needs to be constrained by observations. Finally, we make
predictions for observing 1.1-mm flux density arising from interstellar dust
emission with the Atacama Large Millimeter Array.Comment: Accepted for publication in Ap
Astrophysical Russian dolls
Are there examples of "astrophysical Russian dolls," and what could we learn from their similarities? In this article, we list a few such examples, including disks, filaments, and clusters. We suggest that forging connections across disciplinary borders enhances our perception of beauty, while simultaneously leading to a more comprehensive understanding of the Universe.Astronom
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Limits on Intergalactic Dust During Reionization
In this Letter, we constrain the dust-to-gas ratio in the intergalactic medium (IGM) at high redshifts. We employ models for dust in the local Universe to contrain the dust-to-gas ratio during the epoch of reionization at redshifts z ~ 6-10. The observed level of reddening of high redshift galaxies implies that the IGM was enriched to an intergalactic dust-to-gas ratio of less than 3% of the Milky Way value by a redshift of z=10.Astronom
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The Distortion of the Cosmic Microwave Background Spectrum Due to Intergalactic Dust
Infrared emission from intergalactic dust might compromise the ability of future experiments to detect subtle spectral distortions in the Cosmic Microwave Background (CMB) from the early Universe. We provide the first estimate of foreground contamination of the CMB signal due to diffuse dust emission in the intergalactic medium. We use models of the extragalactic background light to calculate the intensity of intergalactic dust emission and find that emission by intergalactic dust at redshifts z<0.5 exceeds the sensitivity of the planned Primordial Inflation Explorer (PIXIE) to CMB spectral distortions by 1-3 orders of magnitude. We place an upper limit of 0.23% on the contribution to the far-infrared background from intergalactic dust emission.Astronom