Stacked Star Formation Rate Profiles of Bursty Galaxies Exhibit "coherent" Star Formation

Matthew E. Orr; Christopher C. Hayward; Erica J. Nelson; Philip F. Hopkins; Claude André Faucher-Giguère; Dušan Kereš; T. K. Chan; Denise M. Schmitz; Tim B. Miller

doi:10.3847/2041-8213/aa8f93

Stacked Star Formation Rate Profiles of Bursty Galaxies Exhibit "coherent" Star Formation

Matthew E. Orr, Christopher C. Hayward, Erica J. Nelson, Philip F. Hopkins, Claude André Faucher-Giguère, Dušan Kereš, T. K. Chan, Denise M. Schmitz, Tim B. Miller

Physics and Astronomy

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17 Scopus citations

Abstract

In a recent work based on 3200 stacked Hα maps of galaxies at , 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 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.

Original language	English (US)
Article number	L2
Journal	Astrophysical Journal Letters
Volume	849
Issue number	1
DOIs	https://doi.org/10.3847/2041-8213/aa8f93
State	Published - Nov 1 2017

Keywords

galaxies: evolution
galaxies: formation
galaxies: high-redshift
galaxies: star formation
galaxies: structure
methods: observational

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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10.3847/2041-8213/aa8f93

Cite this

@article{86fdb4043cab46ed860e28b7f45a9263,

title = "Stacked Star Formation Rate Profiles of Bursty Galaxies Exhibit {"}coherent{"} Star Formation",

abstract = "In a recent work based on 3200 stacked Hα maps of galaxies at , 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 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.",

keywords = "galaxies: evolution, galaxies: formation, galaxies: high-redshift, galaxies: star formation, galaxies: structure, methods: observational",

author = "Orr, {Matthew E.} and Hayward, {Christopher C.} and Nelson, {Erica J.} and Hopkins, {Philip F.} and Faucher-Gigu{\`e}re, {Claude Andr{\'e}} and Du{\v s}an Kere{\v s} and Chan, {T. K.} and Schmitz, {Denise M.} and Miller, {Tim B.}",

note = "Funding Information: 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. Publisher Copyright: {\textcopyright} 2017. The American Astronomical Society. All rights reserved.",

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doi = "10.3847/2041-8213/aa8f93",

language = "English (US)",

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journal = "Astrophysical Journal Letters",

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T1 - Stacked Star Formation Rate Profiles of Bursty Galaxies Exhibit "coherent" Star Formation

AU - Orr, Matthew E.

AU - Hayward, Christopher C.

AU - Nelson, Erica J.

AU - Hopkins, Philip F.

AU - Faucher-Giguère, Claude André

AU - Kereš, Dušan

AU - Chan, T. K.

AU - Schmitz, Denise M.

AU - Miller, Tim B.

N1 - Funding Information: 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. Publisher Copyright: © 2017. The American Astronomical Society. All rights reserved.

PY - 2017/11/1

Y1 - 2017/11/1

N2 - In a recent work based on 3200 stacked Hα maps of galaxies at , 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 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.

AB - In a recent work based on 3200 stacked Hα maps of galaxies at , 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 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.

KW - galaxies: evolution

KW - galaxies: formation

KW - galaxies: high-redshift

KW - galaxies: star formation

KW - galaxies: structure

KW - methods: observational

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DO - 10.3847/2041-8213/aa8f93

M3 - Article

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SN - 2041-8205

VL - 849

JO - Astrophysical Journal Letters

JF - Astrophysical Journal Letters

IS - 1

M1 - L2

ER -

Stacked Star Formation Rate Profiles of Bursty Galaxies Exhibit "coherent" Star Formation

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