Stacking and Analyzing $z\approx 2$ MOSDEF Galaxies by Spectral Types: Implications for Dust Geometry and Galaxy Evolution
Abstract
We examine star-formation and dust properties for a sample of 660 galaxies at $1.37\leq z\leq 2.61$ in the MOSDEF survey by dividing them into groups with similarly-shaped spectral energy distributions (SEDs). For each group, we combine the galaxy photometry into a finely-sampled composite SED, and stack their spectra. This method enables the study of more complete galaxy samples, including galaxies with very faint emission lines. We fit these composite SEDs with Prospector to measure the stellar attenuation and SED-based star-formation rates (SFRs). We also derive emission-line properties from the spectral stacks, including Balmer decrements, dust-corrected SFRs, and metallicities. We find that stellar attenuation correlates most strongly with mass, while nebular attenuation correlates strongly with both mass and SFR. Furthermore, the excess of nebular compared to stellar attenuation correlates most strongly with SFR. The highest SFR group has 2 mag of excess nebular attenuation. Our results are consistent with a model in which star-forming regions become more dusty as galaxy mass increases. To explain the increasing excess nebular attenuation, we require a progressively larger fraction of star formation to occur in highly-obscured regions with increasing SFR. This highly-obscured star formation could occur in dusty clumps or central starbursts. Additionally, as each galaxy group represents a different evolutionary stage, we study their locations on the UVJ and SFR-mass diagrams. As mass increases, metallicity and dust attenuation increase, while sSFR decreases. However, the most massive group moves towards the quiescent region of the UVJ diagram, while showing less obscuration, potentially indicating removal of dust.
Authors 15
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Leiden University · Leiden Observatory
Affiliation as printed
Leiden Observatory , Leiden University , P.O. Box 9513 , 2300 RA Leiden , The Netherlands
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University of California San Diego
Affiliation as printed
Center for Astrophysics and Space Sciences , Department of Physics , University of California , San Diego , 9500 Gilman Dr. , La Jolla , CA 92093 , USA
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Affiliation as printed
Department of Astronomy and Astrophysics , The Pennsylvania State University , University Park , PA 16802 , USA
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University of California, Riverside
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Department of Physics and Astronomy , University of California , Riverside , 900 University Ave. , Riverside , CA 92521 , USA
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University of Colorado Boulder
Affiliation as printed
Department for Astrophysical and Planetary Science , University of Colorado , Boulder , CO 80309 , USA
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Affiliation as printed
Department of Physics and Astronomy and PITT PACC , University of Pittsburgh , Pittsburgh , PA 15260 , USA
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University of California, Riverside
Affiliation as printed
Department of Physics and Astronomy , University of California , Riverside , 900 University Ave. , Riverside , CA 92521 , USA
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University of California, Los Angeles
Affiliation as printed
Department of Physics and Astronomy , University of California , Los Angeles , 430 Portola Plaza , Los Angeles , CA 90095 , USA
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Kavli Institute for Particle Astrophysics and Cosmology
Affiliation as printed
Kavli Institute for Particle Astrophysics and Cosmology and
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Affiliation as printed
Steward Observatory , University of Arizona , Tucson , AZ 85721 , USA
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University of California, Riverside
Affiliation as printed
Department of Physics and Astronomy , University of California , Riverside , 900 University Ave. , Riverside , CA 92521 , USA
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University of California, Berkeley · Stanford University
Affiliation as printed
Department of Astronomy , University of California , Berkeley , CA 94720 , USA
Department of Physics , Stanford University , Stanford , CA 94305 , USA
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