The Mass Evolution of the First Galaxies: Stellar Mass Functions and Star Formation Rates at 4 < z < 7 in the CANDELS GOODS-South Field

Authors

K. Duncan, University of Nottingham, UK
C. J. Conselice, University of Nottingham, UK
A. Mortlock, University of Nottingham, UK
W. G. Hartley, University of Nottingham, UK
Y. Guo, University of California - Santa Cruz
H. C. Ferguson, Space Telescope Science Institute
R. Davé, University of the Western Cape, South Africa
Y. Lu, Kavli Institute for Particle Astrophysics and Cosmology
J. Owensworth, University of Nottingham, UK
M. L. N. Ashby, Harvard-Smithsonian Center for Astrophysics
A. Dekel, Hebrew University, Israel
M. Dickinson, National Optical Astronomy Observatory
S. Faber, University of California - Santa Cruz
M. Giavalisco, University of Massachusetts - Amherst
N. Grogin, Kavli Institute for Particle Astrophysics and Cosmology
Dale D. Kocevski, University of KentuckyFollow
A. Koekemoer, Space Telescope Science Institute
R. S. Somerville, Rutgers University
C. E. White, Johns Hopkins University

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 M_UV - 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.

Document Type

Article

Publication Date

11-1-2014

Notes/Citation Information

Published in Monthly Notices of the Royal Astronomical Society, v. 444, no. 3, p. 2960-2984.

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

Digital Object Identifier (DOI)

http://dx.doi.org/10.1093/mnras/stu1622

Funding Information

This work is based on observations taken by the CANDELS Multi-Cycle Treasury Program with the NASA/ESA HST, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA. AM acknowledges funding via an ERC consolidator grant (PI: McLure). We would also like to acknowledge funding from the Science and Technology Facilities Council (STFC) and the Leverhulme Trust.

Repository Citation

Duncan, K.; Conselice, C. J.; Mortlock, A.; Hartley, W. G.; Guo, Y.; Ferguson, H. C.; Davé, R.; Lu, Y.; Owensworth, J.; Ashby, M. L. N.; Dekel, A.; Dickinson, M.; Faber, S.; Giavalisco, M.; Grogin, N.; Kocevski, Dale D.; Koekemoer, A.; Somerville, R. S.; and White, C. E., "The Mass Evolution of the First Galaxies: Stellar Mass Functions and Star Formation Rates at 4 < z < 7 in the CANDELS GOODS-South Field" (2014). Physics and Astronomy Faculty Publications. 281.
https://uknowledge.uky.edu/physastron_facpub/281