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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. J. Duncan1School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD UKChristopher J. Conselice1School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD UKA. Mortlock1School of Physics & Astronomy, University of Nottingham, Nottingham NG7 2RD, UKW. G. Hartley3Department of Physics, ETH Zurich, CH-8093 Zurich, SwitzerlandYicheng Guo5Department of Astronomy, University of Massachusetts, Amherst, MA 01003, USAHenry C. Ferguson[Space Telescope Science Institute]Romeel Davé7University of the Western Cape, Bellville, Cape Town 7535, South AfricaYu Lu8Kavli Institute for Particle Astrophysics and Cosmology, Stanford, CA 94309, USAJamie R. Ownsworth1School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD UKM. L. N. Ashby9Harvard–Smithsonian Center for Astrophysics, 60 Garden St, Cambridge, MA 02138, USAAvishai Dekel10Racah Institute of Physics, The Hebrew University, Jerusalem 91904, IsraelMark DickinsonS. M. Faber4UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064, USAM. Giavalisco5Department of Astronomy, University of Massachusetts, Amherst, MA 01003, USANorman A. Grogin8Kavli Institute for Particle Astrophysics and Cosmology, Stanford, CA 94309, USAD. Kocevski12Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506, USAA. M. Koekemoer[Space Telescope Science Institute]Rachel Somerville13Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854, USACatherine E. White14Department of Physics and Astronomy, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA
2014en
ABI

Аннотация

We measure new estimates for the galaxy stellar mass function and star formation rates for samples of galaxies at $z \sim 4,~5,~6~\&~7$ using data in the CANDELS GOODS South field. The deep near-infrared observations allow us to construct the stellar mass function at $z \geq 6$ 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 normalisation which evolves with redshift. Our stellar mass functions have steep low-mass slopes ($\alpha \approx -1.9$), 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 $\log_{10} \rho_{*} = 6.64^{+0.58}_{-0.89}$ at $z \sim 7$ to $7.36\pm0.06$ $\text{M}_{\odot} \text{Mpc}^{-3}$ at $z \sim 4$. Finally, combining the measured UV continuum slopes ($\beta$) with their rest-frame UV luminosities, we calculate dust corrected star-formation rates (SFR) for our sample. We find the specific star-formation rate 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.

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DOI
10.1093/mnras/stu1622

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