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Author Faisst, Andreas L. ♦ Capak, Peter L. ♦ Masters, Daniel C. ♦ Yan, Lin ♦ Pavesi, Riccardo ♦ Riechers, Dominik A. ♦ Barišić, Ivana ♦ Cooke, Kevin C. ♦ Kartaltepe, Jeyhan S.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword ASTROPHYSICS, COSMOLOGY AND ASTRONOMY ♦ BALANCES ♦ COMPARATIVE EVALUATIONS ♦ COSMIC DUST ♦ ENERGY SPECTRA ♦ LIFETIME ♦ LUMINOSITY ♦ MAIN SEQUENCE STARS ♦ MILKY WAY ♦ RADIATION PRESSURE ♦ RED SHIFT ♦ STAR EVOLUTION
Abstract Recent studies have found a significant evolution and scatter in the relationship between the UV spectral slope ( β {sub UV}) and the infrared excess (IRX; L {sub IR}/ L {sub UV}) at z > 4, suggesting different dust properties of these galaxies. The total far-infrared (FIR) luminosity is key for this analysis, but it is poorly constrained in normal (main-sequence) star-forming z > 5 galaxies, where often only one single FIR point is available. To better inform estimates of the FIR luminosity, we construct a sample of local galaxies and three low-redshift analogues of z > 5 systems. The trends in this sample suggest that normal high-redshift galaxies have a warmer infrared (IR) spectral energy distribution (SED) compared to average z < 4 galaxies that are used as priors in these studies. The blueshifted peak and mid-IR excess emission could be explained by a combination of a larger fraction of metal-poor interstellar medium being optically thin to ultraviolet (UV) light and a stronger UV radiation field due to high star formation densities. Assuming a maximally warm IR SED suggests a 0.6 dex increase in total FIR luminosities, which removes some tension between the dust attenuation models and observations of the IRX− β relation at z > 5. Despite this, some galaxies still fall below the minimum IRX− β relation derived with standard dust cloud models. We propose that radiation pressure in these highly star-forming galaxies causes a spatial offset between dust clouds and young star-forming regions within the lifetime of O/B stars. These offsets change the radiation balance and create viewing-angle effects that can change UV colors at fixed IRX. We provide a modified model that can explain the location of these galaxies on the IRX− β diagram.
ISSN 0004637X
Educational Use Research
Learning Resource Type Article
Publisher Date 2017-09-20
Publisher Place United States
Journal Astrophysical Journal
Volume Number 847
Issue Number 1


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