14,227 research outputs found
The IRX- relation: Insights from simulations
We study the relationship between the UV continuum slope and infrared excess
(IRX) predicted by performing dust radiative
transfer on a suite of hydrodynamical simulations of galaxies. Our suite
includes both isolated disk galaxies and mergers intended to be representative
of galaxies at both and . Our low-redshift isolated
disks and mergers often populate a region around the the locally calibrated
\citet[][M99]{M99} relation but move well above the relation during
merger-induced starbursts. Our high-redshift simulated galaxies are blue and
IR-luminous, which makes them lie above the M99 relation. The value of UV
continuum slope strongly depends on the dust type used in the radiative
transfer calculations: Milky Way-type dust leads to significantly more negative
(bluer) slopes compared with Small Magellanic Cloud-type dust. The effect on
due to variations in the dust composition with galaxy properties or
redshift can dominate over other sources of variations and is the
dominant model uncertainty. The dispersion in is anticorrelated with
specific star formation rate and tends to be higher for the
simulations. In the actively star-forming simulated galaxies, dust
attenuation dominates the dispersion in , whereas in the
simulations, the contributions of SFH variations and dust are similar. For
low-SSFR systems at both redshifts, SFH variations dominate the dispersion.
Finally, the simulated isolated disks and mergers both occupy a
region in the \irxbeta\ plane consistent with observed dusty
star-forming galaxies (DSFGs). Thus, contrary to some claims in the literature,
the blue colors of high-z DSFGs do not imply that they are short-lived
starbursts.Comment: 20 pages+a 4-page appendix, Accepted for publication at Ap
A complete distribution of redshifts for sub-millimetre galaxies in the SCUBA-2 Cosmology Legacy Survey UDS field
This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. Available online at https://doi.org/10.1093/mnras/stx1689. © 2017 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.Sub-milllimetre galaxies (SMGs) are some of the most luminous star-forming galaxies in the Universe, however their properties remain hard to determine due to the difficulty of identifying their optical\slash near-infrared counterparts. One of the key steps to determining the nature of SMGs is measuring a redshift distribution representative of the whole population. We do this by applying statistical techniques to a sample of 761 850m sources from the SCUBA-2 Cosmology Legacy Survey observations of the UKIDSS Ultra-Deep Survey (UDS) Field. We detect excess galaxies around per cent of the 850m positions in the deep UDS catalogue, giving us the first 850m selected sample to have virtually complete optical\slash near-infrared redshift information. Under the reasonable assumption that the redshifts of the excess galaxies are representative of the SMGs themselves, we derive a median SMG redshift of , with 68 per cent of SMGs residing between $1.07Peer reviewedFinal Accepted Versio
What shapes the far-infrared spectral energy distributions of galaxies?
To explore the connection between the global physical properties of galaxies
and their far-infrared (FIR) spectral energy distributions (SEDs), we study the
variation in the FIR SEDs of a set of hydrodynamically simulated galaxies that
are generated by performing dust radiative transfer in post-processing. Our
sample includes both isolated and merging systems at various stages of the
merging process and covers infrared (IR) luminosities and dust masses that are
representative of both low- and high-redshift galaxies. We study the FIR SEDs
using principle component analysis (PCA) and find that 97\% of the variance in
the sample can be explained by two principle components (PCs). The first PC
characterizes the wavelength of the peak of the FIR SED, and the second encodes
the breadth of the SED. We find that the coefficients of both PCs can be
predicted well using a double power law in terms of the IR luminosity and dust
mass, which suggests that these two physical properties are the primary
determinants of galaxies' FIR SED shapes. Incorporating galaxy sizes does not
significantly improve our ability to predict the FIR SEDs. Our results suggest
that the observed redshift evolution in the effective dust temperature at fixed
IR luminosity is not driven by geometry: the SEDs of ultraluminous
IR galaxies (ULIRGs) are cooler than those of local ULIRGs not because the
high-redshift galaxies are more extended but rather because they have higher
dust masses at fixed IR luminosity. Finally, based on our simulations, we
introduce a two-parameter set of SED templates that depend on both IR
luminosity and dust mass.Comment: Submitted to ApJ, comments welcom
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