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Stellar Populations of over one thousand $zsim0.8$ Galaxies from LEGA-C: Ages and Star Formation Histories from D$_n$4000 and H$delta$ | | Po-Feng Wu
; Arjen van der Wel
; Anna Gallazzi
; Rachel Bezanson
; Camilla Pacifici
; Caroline Straatman
; Marijn Franx
; Ivana Barišić
; Eric F. Bell
; Gabriel B. Brammer
; Joao Calhau
; Priscilla Chauke
; Josha van Houdt
; Michael V. Maseda
; Adam Muzzin
; Hans-Walter Rix
; David Sobral
; Justin Spilker
; Jesse van de Sande
; Pieter van Dokkum
; Vivienne Wild
; | | Date: |
19 Feb 2018 | | Abstract: | Drawing from the LEGA-C dataset, we present the spectroscopic view of the
stellar population across a large volume- and mass-selected sample of galaxies
at large lookback time. We measure the 4000AA break (D$_n$4000) and Balmer
absorption line strengths (probed by H$delta$) from 1019 high-quality spectra
of $z=0.6 - 1.0$ galaxies with $M_ast = 2 imes 10^{10} M_odot - 3 imes
10^{11} M_odot$. Our analysis serves as a first illustration of the power of
high-resolution, high-S/N continuum spectroscopy at intermediate redshifts as a
qualitatively new tool to constrain galaxy formation models. The observed
D$_n$4000-EW(H$delta$) distribution of our sample overlaps with the
distribution traced by present-day galaxies, but $zsim 0.8$ galaxies populate
that locus in a fundamentally different manner. While old galaxies dominate the
present-day population at all stellar masses $> 2 imes10^{10} M_odot$, we see
a bimodal D$_n$4000-EW(H$delta$) distribution at $zsim0.8$, implying a
bimodal light-weighted age distribution. The light-weighted age depends
strongly on stellar mass, with the most massive galaxies
$>1 imes10^{11}M_odot$ being almost all older than 2 Gyr. At the same time we
estimate that galaxies in this high mass range are only $sim3$ Gyr younger
than their $zsim0.1$ counterparts, at odd with pure passive evolution given a
difference in lookback time of $>5$ Gyr; younger galaxies must grow to
$>10^{11}M_odot$ in the meantime, and/or small amounts of young stars must
keep the light-weighted ages young. Star-forming galaxies at $zsim0.8$ have
stronger H$delta$ absorption than present-day galaxies with the same
D$_n$4000, implying larger short-term variations in star-formation activity. | | Source: | arXiv, 1802.6799 | | Services: | Forum | Review | PDF | Favorites | |
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