The mass evolution of the first galaxies: stellar mass functions and star formation rates at 4 < z < 7 in the CANDELS GOODS-south field

K. Duncan, C. J. Conselice, A. Mortlock, W. G. Hartley, Y. Guo, H. C. Ferguson, R. Davé, Y. Lu, J. Ownsworth, M. L N Ashby, A. Dekel, M. Dickinson, S. Faber, M. Giavalisco, N. Grogin, D. Kocevski, A. Koekemoer, R. S. Somerville, C. E. White

Research output: Contribution to journalArticlepeer-review

Abstract

We measure new estimates for the galaxy stellar mass function and star formation rates for samples of galaxies at z ∼ 4, 5, 6 and 7 using data in the CANDELS GOODS South field. The deep near-infrared observations allow us to construct the stellar mass function at z ≥ 6 directly for the first time. We estimate stellar masses for our sample by fitting the observed spectral energy distributions with synthetic stellar populations, including nebular line and continuum emission. The observed UV luminosity functions for the samples are consistent with previous observations; however, we find that the observed MUV-M* relation has a shallow slope more consistent with a constant mass-to-light ratio and a normalization which evolves with redshift. Our stellar mass functions have steep low-mass slopes (α ≈ −1.9), steeper than previously observed at these redshifts and closer to that of the UV luminosity function. Integrating our new mass functions, we find the observed stellar mass density evolves from log10ρ=6.64+0.58−0.89 at z ∼ 7 to 7.36 ± 0.06 M Mpc− 3 at z ∼ 4. Finally, combining the measured UV continuum slopes (β) with their rest-frame UV luminosities, we calculate dust-corrected star formation rates (SFR) for our sample. We find the specific SFR for a fixed stellar mass increases with redshift whilst the global SFR density falls rapidly over this period. Our new SFR density estimates are higher than previously observed at this redshift.

Original languageEnglish
Pages (from-to)2960-2984
Number of pages25
JournalMonthly Notices of the Royal Astronomical Society
Volume444
Issue number3
Early online date12 Sep 2014
DOIs
Publication statusPublished - 1 Nov 2014

Keywords

  • Galaxies: Evolution
  • Galaxies: Formation
  • Galaxies: High-redshift
  • Galaxies: Luminosity function, mass function

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