Bahram Mobasher, University of California - Riverside
Tomas Dahlen, Space Telescope Science Institute
Henry C. Ferguson, Space Telescope Science Institute
Viviana Acquaviva, CUNY NYC College of Technology
Guillermo Barro, University of California - Santa Cruz
Steven L. Finkelstein, University of Texas at Austin
Adriano Fontana, Osservatorio Astronomico di Roma, Italy
Ruth Gruetzbauch, Observatorio Astronomico de Lisboa, Portugal
Seth Johnson, University of Massachusetts
Yu Lu, Stanford University
Casey Papovich, Texas A&M Research Foundation
Janine Pforr, National Optical Astronomy Observatories
Mara Salvato, Max-Planck-Institut für extraterrestrische Physik, Germany
Rachel S. Somerville, Rutgers University
Tommy Wiklind, Joint ALMA Observatory, Chile
Stijn Wuyts, Max-Planck-Institut für extraterrestrische Physik, Germany
Matthew L.N. Ashby, Harvard-Smithsonian Center for Astrophysics
Eric Bell, University of Michigan
Christopher J. Conselice, University of Nottingham, UK
Mark E. Dickinson, National Optical Astronomy Observatories
Sandra M. Faber, University of California - Santa Cruz
Giovanni Fazio, Harvard-Smithsonian Center for Astrophysics
Kristian Finlator, Niels Bohr Institute, Denmark
Audrey Galametz, Osservatorio Astronomico di Roma, Italy
Eric Gawiser, Rutgers University
Mauro Giavalisco, University of Massachusetts
Andrea Grazian, Osservatorio Astronomico di Roma, Italy
Norman A. Grogin, Space Telescope Science Institute
Yicheng Guo, University of California - Santa Cruz
Nimish Hathi, LAM—Laboratoire d'Astrophysique de Marseille, France
Dale Kocevski, University of KentuckyFollow
Anton M. Koekemoer, Space Telescope Science Institute
David C. Koo, University of California - Santa Cruz
Jeffrey A. Newman, University of Pittsburgh
Naveen Reddy, University of California - Riverside
Paola Santini, Osservatorio Astronomico di Roma, Italy
Risa H. Wechsler, Stanford University


This is the second paper in a series aimed at investigating the main sources of uncertainty in measuring the observable parameters in galaxies from their spectral energy distributions (SEDs). In the first paper we presented a detailed account of the photometric redshift measurements and an error analysis of this process. In this paper we perform a comprehensive study of the main sources of random and systematic error in stellar mass estimates for galaxies, and their relative contributions to the associated error budget. Since there is no prior knowledge of the stellar mass of galaxies (unlike their photometric redshifts), we use mock galaxy catalogs with simulated multi-waveband photometry and known redshift, stellar mass, age and extinction for individual galaxies. The multi-waveband photometry for the simulated galaxies were generated in 13 filters spanning from U-band to mid-infrared wavelengths. Given different parameters affecting stellar mass measurement (photometric signal-to-noise ratios (S/N), SED fitting errors and systematic effects), the inherent degeneracies and correlated errors, we formulated different simulated galaxy catalogs to quantify these effects individually. For comparison, we also generated catalogs based on observed photometric data of real galaxies in the Great Observatories Origins Deep Survey-South field, spanning the same passbands. The simulated and observed catalogs were provided to a number of teams within the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey collaboration to estimate the stellar masses for individual galaxies. A total of 11 teams participated, with different combinations of stellar mass measurement codes/methods, population synthesis models, star formation histories, extinction and age. For each simulated galaxy, the differences between the input stellar masses, Minput, and those estimated by each team, Mest, is defined as Δlog(M) ≡ log(Mestimated) - log(Minput), and used to identify the most fundamental parameters affecting stellar mass estimate in galaxies, with the following results. (1) No significant bias in Δ log(M) was found among different codes, with all having comparable scatter (σ(Δlog(M))= 0.136 dex). The estimated stellar mass values are seriously affected by low photometric S/N, with the rms scatter increasing for galaxies with HAB > 26 mag; (2) A source of error contributing to the scatter in Δ log(M) is found to be due to photometric uncertainties (0.136 dex) and low resolution in age and extinction grids when generating the SED templates; (3) The median of stellar masses among different methods provides a stable measure of the mass associated with any given galaxy (σ(Δlog(M))= 0.142 dex); (4) The Δ log(M) values are strongly correlated with deviations in age (defined as the difference between the estimated and expected values), with a weaker correlation with extinction; (5) The rms scatter in the estimated stellar masses due to free parameters (after fixing redshifts and initial mass function) are quantified and found to be σ(Δlog(M))= 0.110 dex; (6) Using the observed data, we studied the sensitivity of stellar masses to both the population synthesis codes and inclusion of nebular emission lines and found them to affect the stellar mass by 0.2 and 0.3 dex respectively.

Document Type


Publication Date


Notes/Citation Information

Published in The Astrophysical Journal, v. 808, no. 1, article 101, p. 1-28.

© 2015. The American Astronomical Society. All rights reserved.

Reproduced by permission of the AAS.

Digital Object Identifier (DOI)

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