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The COSMOS2015 galaxy stellar mass function: 13 billion years of stellar mass assembly in 10 snapshots

Davidzon, I. and Ilbert, O. and Laigle, C. and Coupon, J. and McCracken, H. J. and Delvecchio, I. and Masters, D. and Capak, P. L. and Hsieh, B. C. and Tresse, L. and Le Fevre, O. and Bethermin, M. and Chang, Y. -Y. and Faisst, A. L. and Le Floc'h, E. and Steinhardt, C. and Toft, S. and Aussel, H. and Dubois, C. and Hasinger, G. and Salvato, M. and Sanders, D. B. and Scoville, N. and Silverman, J. D. (2017) The COSMOS2015 galaxy stellar mass function: 13 billion years of stellar mass assembly in 10 snapshots. . (Submitted)

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We measure the stellar mass function (SMF) of galaxies in the COSMOS field up to $z\sim6$. We select them in the near-IR bands of the COSMOS2015 catalogue, which includes ultra-deep photometry from UltraVISTA-DR2, SPLASH, and Subaru/Hyper-SuprimeCam. At $z>2.5$ we use new precise photometric redshifts with error $\sigma_z=0.03(1+z)$ and an outlier fraction of $12\%$, estimated by means of the unique spectroscopic sample of COSMOS. The increased exposure time in the DR2, along with our panchromatic detection strategy, allow us to improve the stellar mass completeness at high $z$ with respect to previous UltraVISTA catalogues. We also identify passive galaxies through a robust colour-colour selection, extending their SMF estimate up to $z=4$. Our work provides a comprehensive view of galaxy stellar mass assembly between $z=0.1$ and 6, for the first time using consistent estimates across the entire redshift range. We fit these measurements with a Schechter function, correcting for Eddington bias. We compare the SMF fit with the halo mass function predicted from $\Lambda$CDM simulations. We find that at $z>3$ both functions decline with a similar slope in the high-mass end. This feature could be explained assuming that the mechanisms that quench star formation in massive haloes become less effective at high redshift; however further work needs to be done to confirm this scenario. Concerning the SMF low-mass end, it shows a progressive steepening as moving towards higher redshifts, with $\alpha$ decreasing from $-1.47_{-0.02}^{+0.02}$ at $z\simeq0.1$ to $-2.11_{-0.13}^{+0.30}$ at $z\simeq5$. This slope depends on the characterisation of the observational uncertainties, which is crucial to properly remove the Eddington bias. We show that there is currently no consensus on the method to quantify such errors: different error models result in different best-fit Schechter parameters. [Abridged]

Item Type:Report or Paper (Discussion Paper)
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Scoville, N.0000-0002-0438-3323
Additional Information:The authors warmly thank the anonymous referee for her/his constructive comments. The authors thank Shoubaneh Hemmati and Hooshang Nayyeri for providing us with the CANDELS Multiwavelength Catalog in the COSMOS field, and Andrea Grazian and Thibault Garel for sending their results in a convenient digitalised format. ID thanks Marta Volonteri, Jeremy Blaizot, Yohan Dubois, Andrea Grazian, Roberto Maiolino for very useful discussions. ID and OI acknowledge funding of the French Agence Nationale de la Recherche for the SAGACE project. CL acknowledges support from a Beecroft fellowship. ID acknowledges the European Union’s Seventh Framework programme under grant agreement 337595 (ERC Starting Grant, “CoSMass”) AF acknowledges support from the Swiss National Science Foundation. The COSMOS team in France acknowledges support from the Centre National d’Études Spatiales.
Funding AgencyGrant Number
Beecroft fellowshipUNSPECIFIED
European Research Council (ERC)337595
Swiss National Science Foundation (SNSF)UNSPECIFIED
Centre National d’Études Spatiales (CNES)UNSPECIFIED
Record Number:CaltechAUTHORS:20170628-140248161
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:78661
Deposited By: Joy Painter
Deposited On:28 Jun 2017 21:13
Last Modified:28 Jun 2017 21:13

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