Evolution of Galactic Outflows at z ∼ 0-2 Revealed with SDSS, DEEP2, and Keck Spectra

Yuma Sugahara, Masami Ouchi, Lihwai Lin, Crystal L. Martin, Yoshiaki Ono, Yuichi Harikane, Takatoshi Shibuya, Renbin Yan

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29 Scopus citations


We conduct a systematic study of galactic outflows in star-forming galaxies at z ∼ 0-2 based on the absorption lines of optical spectra taken from SDSS DR7, DEEP2 DR4, and Keck (Erb et al.). We carefully make stacked spectra of homogeneous galaxy samples with similar stellar mass distributions at z ∼ 0-2 and perform the multicomponent fitting of model absorption lines and stellar continua to the stacked spectra. We obtain the maximum (vmax) and central (vout) outflow velocities and estimate the mass loading factors (η), a ratio of the mass outflow rate to the star formation rate (SFR). Investigating the redshift evolution of the outflow velocities measured with the absorption lines whose depths and ionization energies are similar (Na I D and Mg I at z ∼ 0-1; Mg II and C II at z ∼ 1-2), we identify, for the first time, that the average value of vmax (vout) significantly increases by 0.05-0.3 dex from z ∼ 0 to 2 at a given SFR. Moreover, we find that the value of η increases from z ∼ 0 to 2 by η ∝ (1 + z)1.2±0.3 at a given halo circular velocity vcir, albeit with a potential systematics caused by model parameter choices. The redshift evolution of vmax (vout) and η is consistent with the galaxy-size evolution and the local velocity-SFR surface density relation and explained by high gas fractions in high-redshift massive galaxies, which is supported by recent radio observations. We obtain a scaling relation of η ∝ νcira for a = -0.2 ± 1.1 in our z ∼ 0 galaxies that agrees with the momentum-driven outflow model (a = -1) within the uncertainties.

Original languageEnglish
Article number51
JournalAstrophysical Journal
Issue number1
StatePublished - Nov 20 2017

Bibliographical note

Funding Information:
Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The DEEP2 team and Keck Observatory acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community and appreciate the opportunity to conduct observations from this mountain. The analysis pipeline used to reduce the DEIMOS data was developed at UC Berkeley with support from NSF grant AST-0071048. Funding for the DEEP2 Galaxy Redshift Survey has been provided by NSF grants AST-95-09298, AST-0071048, AST-0507428, and AST-0507483, as well as NASA LTSA grant NNG04GC89G. This research has made use of the Keck Observatory Archive (KOA), which is operated by the W. M. Keck Observatory and the NASA Exoplanet Science Institute (NExScI), under contract with the National Aeronautics and Space Administration.

Funding Information:
Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSS website ishttp://www.sdss.org/. The SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions. The Participating Institutions are the American Museum of Natural History, Astrophysical Institute Potsdam, University of Basel, University of Cambridge, Case Western Reserve University, University of Chicago, Drexel University, Fermilab, the Institute for Advanced Study, the Japan Participation Group, Johns Hopkins University, the Joint Institute for Nuclear Astrophysics, the Kavli Institute for Particle Astrophysics and Cosmology, the Korean Scientist Group, the Chinese Academy of Sciences (LAMOST), Los Alamos National Laboratory, the Max-Planck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, Ohio State University, University of Pittsburgh, University of Portsmouth, Princeton University, the United States Naval Observatory, and the University of Washington.

Funding Information:
This work is supported by the World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan, and the KAKENHI (15H02064) Grant-in-Aid for Scientific Research (A) through the Japan Society for the Promotion of Science (JSPS).

Publisher Copyright:
© 2017. The American Astronomical Society. All rights reserved.


  • galaxies: ISM
  • galaxies: evolution
  • galaxies: formation
  • galaxies: kinematics and dynamics

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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