The MOSDEF Survey: Stellar Continuum Spectra and Star Formation Histories of Active, Transitional, and Quiescent Galaxies at 1.4 < z < 2.6

Tom O. Zick, Mariska Kriek, Alice E. Shapley, Naveen A. Reddy, William R. Freeman, Brian Siana, Alison L. Coil, Mojegan Azadi, Guillermo Barro, Tara Fetherolf, Francesca M. Fornasini, Laura De Groot, Gene Leung, Bahram Mobasher, Sedona H. Price, Ryan L. Sanders, Irene Shivaei

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Using the MOSFIRE Deep Evolution Field (MOSDEF) rest-frame optical spectroscopic survey, we investigate the star formation histories (SFHs) of different galaxy types, ranging from actively star-forming to quiescent at 1.4 ≤ z ≤ 2.6. SFHs are constrained utilizing stellar continuum spectroscopy, specifically through a combination of Balmer absorption lines, the 4000 Å break, and the equivalent width of the Hα emission line. To attain a sufficiently high signal-to-noise ratio (S/N) to conduct these measurements we stack spectra of galaxies with similar spectral types, as determined from their rest-frame U - V and V - J colors. We bin the MOSDEF sample into five spectral types, subdividing the quiescent and star-forming bins to better explore galaxies transitioning between the two. We constrain the average SFHs for each type, finding that quiescent and transitional galaxies in the MOSDEF sample are dominated by an SFH with an average star formation timescale of τ ∼ 0.1-0.2 Gyr. These findings contrast with measurements from the low-redshift Universe where, on average, galaxies form their stars over a more extended time period (τ > 1 Gyr). Furthermore, our spectral index measurements correlate with mass surface density for all spectral types. Finally, we compare the average properties of the galaxies in our transitional bins to investigate possible paths to quiescence, and speculate on the viability of a dusty post-starburst phase.

Original languageEnglish
Article numberL16
JournalAstrophysical Journal Letters
Issue number1
StatePublished - Nov 1 2018

Bibliographical note

Funding Information:
We would like to thank Dan Kelson for a referee report that improved the clarity and quality of the manuscript. Funding for the MOSDEF survey is provided by NSF-AAG grants AST-1312780, 1312547, 1312764, and 1313171, grant AR-13907 provided by NASA through a grant from the Space Telescope Science Institute, and NASA-ADAP grant NNX16AF54G. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Funding for T.O.Z. was provided by LLNL Livermore Graduate Scholar Program. We also acknowledge the members of the 3D-HST collaboration, who provided us with spectroscopic and photometric catalogs used to select MOSDEF targets and derive stellar population parameters.

Publisher Copyright:
© 2018. The American Astronomical Society. All rights reserved.


  • galaxies: evolution
  • galaxies: high-redshift

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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