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Stacked Star Formation Rate Profiles of Bursty Galaxies Exhibit “Coherent” Star Formation

Orr, Matthew E. and Hayward, Christopher C. and Nelson, Erica J. and Hopkins, Philip F. and Faucher-Giguère, Claude-André and Kereš, Dušan and Chan, T. K. and Schmitz, Denise M. and Miller, Tim B. (2017) Stacked Star Formation Rate Profiles of Bursty Galaxies Exhibit “Coherent” Star Formation. Astrophysical Journal Letters, 849 (1). Art. No. L2. ISSN 2041-8213. doi:10.3847/2041-8213/aa8f93.

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In a recent work based on 3200 stacked Hα maps of galaxies at z ~ 1, Nelson et al. find evidence for "coherent star formation": the stacked star formation rate (SFR) profiles of galaxies above (below) the "star formation main sequence" (MS) are above (below) that of galaxies on the MS at all radii. One might interpret this result as inconsistent with highly bursty star formation and evidence that galaxies evolve smoothly along the MS rather than crossing it many times. We analyze six simulated galaxies at z ~ 1 from the Feedback in Realistic Environments (FIRE) project in a manner analogous to the observations to test whether the above interpretations are correct. The trends in stacked SFR profiles are qualitatively consistent with those observed. However, SFR profiles of individual galaxies are much more complex than the stacked profiles: the former can be flat or even peak at large radii because of the highly clustered nature of star formation in the simulations. Moreover, the SFR profiles of individual galaxies above (below) the MS are not systematically above (below) those of MS galaxies at all radii. We conclude that the time-averaged coherent star formation evident stacks of observed galaxies is consistent with highly bursty, clumpy star formation of individual galaxies and is not evidence that galaxies evolve smoothly along the MS.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Orr, Matthew E.0000-0003-1053-3081
Hayward, Christopher C.0000-0003-4073-3236
Nelson, Erica J.0000-0002-7524-374X
Hopkins, Philip F.0000-0003-3729-1684
Faucher-Giguère, Claude-André0000-0002-4900-6628
Kereš, Dušan0000-0002-1666-7067
Chan, T. K.0000-0003-2544-054X
Schmitz, Denise M.0000-0001-6297-9312
Additional Information:© 2017 The American Astronomical Society. Received 2017 July 12; revised 2017 September 25; accepted 2017 September 27; published 2017 October 20. M.E.O. is grateful for the encouragement of his late father, S.R.O., in studying astrophysics, and is supported by the National Science Foundation Graduate Research Fellowship under grant No. 1144469. We are grateful to the anonymous referee for providing us with constructive comments and suggestions. The Flatiron Institute is supported by the Simons Foundation. Support for P.F.H. was provided by an Alfred P. Sloan Research Fellowship, NASA ATP grant NNX14AH35G, and NSF Collaborative Research grant No. 1411920 and CAREER grant No. 1455342. C.A.F.G. was supported by NSF through grants AST-1412836 and AST-1517491, by NASA through grant NNX15AB22G, and by STScI through grant HST-AR-14562.001. D.K. acknowledges support from NSF grant AST-1412153 and the Cottrell Scholar Award from the Research Corporation for Science Advancement. D.M.S. is supported by the National Science Foundation Graduate Research Fellowship under grant No. 2015192719.
Group:TAPIR, Astronomy Department
Funding AgencyGrant Number
NSF Graduate Research FellowshipDGE-1144469
Simons FoundationUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Research CorporationUNSPECIFIED
NSF Graduate Research Fellowship2015192719
Subject Keywords:galaxies: evolution – galaxies: formation – galaxies: high-redshift – galaxies: star formation – galaxies: structure – methods: observational
Issue or Number:1
Record Number:CaltechAUTHORS:20171023-105621121
Persistent URL:
Official Citation:Matthew E. Orr et al 2017 ApJL 849 L2
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:82580
Deposited By: Tony Diaz
Deposited On:24 Oct 2017 18:47
Last Modified:15 Nov 2021 19:51

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