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Title: | Stellar Populations of over 1000 z ̃ 0.8 Galaxies from LEGA-C: Ages and Star Formation Histories from D n 4000 and Hδ | Authors: | Wu, Po-Feng VAN DER WEL, ARJEN GALLAZZI, Anna Rita Bezanson, Rachel Pacifici, Camilla Straatman, Caroline Franx, Marijn Barišić, Ivana Bell, Eric F. Brammer, Gabriel B. Calhau, Joao Chauke, Priscilla van Houdt, Josha Maseda, Michael V. Muzzin, Adam Rix, Hans-Walter Sobral, David Spilker, Justin van de Sande, Jesse van Dokkum, Pieter Wild, Vivienne |
Issue Date: | 2018 | Journal: | THE ASTROPHYSICAL JOURNAL | Number: | 855 | Issue: | 2 | First Page: | 85 | Abstract: | Drawing from the LEGA-C data set, we present the spectroscopic view of the stellar population across a large volume- and mass-selected sample of galaxies at large look-back time. We measure the 4000 Å break (D<SUB> n </SUB>4000) and Balmer absorption line strengths (probed by Hδ) from 1019 high-quality spectra of z = 0.6-1.0 galaxies with M <SUB>*</SUB> = 2 × 10<SUP>10</SUP> M <SUB>☉</SUB> to 3 × 10<SUP>11</SUP> M <SUB>☉</SUB>. Our analysis serves as a first illustration of the power of high-resolution, high signal-to-noise ratio continuum spectroscopy at intermediate redshifts as a qualitatively new tool to constrain galaxy formation models. The observed D<SUB> n </SUB>4000-EW(Hδ) distribution of our sample overlaps with the distribution traced by present-day galaxies, but z ̃ 0.8 galaxies populate that locus in a fundamentally different manner. While old galaxies dominate the present-day population at all stellar masses >2 × 10<SUP>10</SUP> M <SUB>☉</SUB>, we see a bimodal D<SUB> n </SUB>4000-EW(Hδ) distribution at z ̃ 0.8, implying a bimodal light-weighted age distribution. The light-weighted age depends strongly on stellar mass, with the most massive galaxies >1 × 10<SUP>11</SUP> M <SUB>☉</SUB> being almost all older than 2 Gyr. At the same time, we estimate that galaxies in this high-mass range are only ̃3 Gyr younger than their z ̃ 0.1 counterparts, at odds with purely passive evolution given a difference in look-back time of >5 Gyr; younger galaxies must grow to >10<SUP>11</SUP> M <SUB>☉</SUB> in the meantime, or small amounts of young stars must keep the light-weighted ages young. Star-forming galaxies at z ̃ 0.8 have stronger Hδ absorption than present-day galaxies with the same D<SUB> n </SUB>4000, implying larger short-term variations in star formation activity. | URI: | http://hdl.handle.net/20.500.12386/27958 | URL: | https://iopscience.iop.org/article/10.3847/1538-4357/aab0a6 | ISSN: | 0004-637X | DOI: | 10.3847/1538-4357/aab0a6 | Bibcode ADS: | 2018ApJ...855...85W | Fulltext: | open |
Appears in Collections: | 1.01 Articoli in rivista |
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Wu_2018_ApJ_855_85.pdf | Pdf editoriale | 1.41 MB | Adobe PDF | View/Open |
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