The nature of massive transition galaxies in CANDELS, GAMA and cosmological simulations

Viraj Pandya, Ryan Brennan, Rachel S. Somerville, Ena Choi, Guillermo Barro, Stijn Wuyts, Edward N. Taylor, Peter Behroozi, Allison Kirkpatrick, Sandra M. Faber, Joel Primack, David C. Koo, Daniel H. McIntosh, Dale Kocevski, Eric F. Bell, Avishai Dekel, Jerome J. Fang, Henry C. Ferguson, Norman Grogin, Anton M. KoekemoerYu Lu, Kameswara Mantha, Bahram Mobasher, Jeffrey Newman, Camilla Pacifici, Casey Papovich, Arjen van der Wel, Hassen M. Yesuf

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66 Scopus citations


We explore observational and theoretical constraints on how galaxies might transition between the 'star-forming main sequence' (SFMS) and varying 'degrees of quiescence' out to z = 3. Our analysis is focused on galaxies with stellar mass M* > 1010M, and is enabled by GAMA and CANDELS observations, a semi-analytic model (SAM) of galaxy formation, and a cosmological hydrodynamical 'zoom in' simulation with momentum-driven AGN feedback. In both the observations and the SAM, transition galaxies tend to have intermediate Sérsic indices, half-light radii, and surface stellar mass densities compared to star-forming and quiescent galaxies out to z=3.We place an observational upper limit on the average population transition time-scale as a function of redshift, finding that the average high-redshift galaxy is on a 'fast track' for quenching whereas the average low-redshift galaxy is on a 'slow track' for quenching. We qualitatively identify four physical origin scenarios for transition galaxies in the SAM: oscillations on the SFMS, slow quenching, fast quenching, and rejuvenation. Quenching time-scales in both the SAM and the hydrodynamical simulation are not fast enough to reproduce the quiescent population that we observe at z ~ 3. In the SAM, we do not find a clear-cut morphological dependence of quenching time-scales, but we do predict that the mean stellar ages, cold gas fractions, SMBH (supermassive black hole) masses and halo masses of transition galaxies tend to be intermediate relative to those of star-forming and quiescent galaxies at z < 3.

Original languageEnglish (US)
Pages (from-to)2054-2084
Number of pages31
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
StatePublished - Dec 2017
Externally publishedYes

Bibliographical note

Funding Information:
We thank the anonymous referee for suggestions that improved the manuscript. We further thank James E. Gunn, Barry Madore, Jennifer Lotz, Romeel Dave, Phil Hopkins, Lars Hernquist, Aaron Romanowsky, Irene Shivaei, Sandro Tacchella and Samir Salim for inspiring discussions. VP is grateful for the encouragement and support from Roderich Tumulka, the astronomy faculty at Rutgers (in particular Saurabh Jha, Andrew Baker and Tad Pryor), the Princeton Post-Baccalaureate Program in Astrophysics (in particular Jenny Greene, Anatoly Spitkovsky, Michael Strauss, Jill Knapp and Jesus Hinojosa), and John Mulchaey. RB was supported in part by HST Theory grant HST-AR-13270-A. RSS thanks the Downsbrough family for their generous support, and acknowledges support from the Simons Foundation through a Simons Investigator grant. PB was supported by programme number HST-HF2-51353.001-A, provided by NASA through a Hubble Fellowship grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. AK gratefully acknowledges support from the YCAA Prize Postdoctoral Fellowship. We acknowledge the contributions of hundreds of individuals to the planning and support of the CANDELS observations, and to the development and installation of new instruments on HST, without which this work would not have been possible. Support for programme number HST-GO-12060 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, incorporated under NASA contract NAS5-26555. This work has made use of the Rainbow Cosmological Surveys Database, which is operated by the Universidad Complutense de Madrid (UCM), partnered with the University of California Observatories at Santa Cruz (UCO/ Lick, UCSC)

Publisher Copyright:
© 2017 The Authors.


  • Galaxies: bulges
  • Galaxies: evolution
  • Galaxies: formation
  • Galaxies: highredshift
  • Galaxies: star formation
  • Galaxies: structure


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