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Gas kinematics in FIRE simulated galaxies compared to spatially unresolved H I observations

El-Badry, Kareem and Bradford, Jeremy and Quataert, Eliot and Geha, Marla and Boylan-Kolchin, Michael and Weisz, Daniel R. and Wetzel, Andrew and Hopkins, Philip F. and Chan, T. K. and Fitts, Alex and Kereš, Dušan and Faucher-Giguère, Claude-André (2018) Gas kinematics in FIRE simulated galaxies compared to spatially unresolved H I observations. Monthly Notices of the Royal Astronomical Society, 477 (2). pp. 1536-1548. ISSN 0035-8711.

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The shape of a galaxy's spatially unresolved, globally integrated 21-cm emission line depends on its internal gas kinematics: galaxies with rotationally supported gas discs produce double-horned profiles with steep wings, while galaxies with dispersion-supported gas produce Gaussian-like profiles with sloped wings. Using mock observations of simulated galaxies from the FIRE project, we show that one can therefore constrain a galaxy's gas kinematics from its unresolved 21-cm line profile. In particular, we find that the kurtosis of the 21-cm line increases with decreasing V/σ and that this trend is robust across a wide range of masses, signal-to-noise ratios, and inclinations. We then quantify the shapes of 21-cm line profiles from a morphologically unbiased sample of ∼2000 low-redshift, H I-detected galaxies with M_(star) = 10^(7−11) M_⊙ and compare to the simulated galaxies. At M_(star) ≳ 10^(10) M_⊙, both the observed and simulated galaxies produce double-horned profiles with low kurtosis and steep wings, consistent with rotationally supported discs. Both the observed and simulated line profiles become more Gaussian like (higher kurtosis and less-steep wings) at lower masses, indicating increased dispersion support. However, the simulated galaxies transition from rotational to dispersion support more strongly: at M_(star) = 10^(8−10) M_⊙, most of the simulations produce more Gaussian-like profiles than typical observed galaxies with similar mass, indicating that gas in the low-mass simulated galaxies is, on average, overly dispersion supported. Most of the lower-mass-simulated galaxies also have somewhat lower gas fractions than the median of the observed population. The simulations nevertheless reproduce the observed line-width baryonic Tully–Fisher relation, which is insensitive to rotational versus dispersion support.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
El-Badry, Kareem0000-0002-6871-1752
Quataert, Eliot0000-0001-9185-5044
Geha, Marla0000-0002-7007-9725
Boylan-Kolchin, Michael0000-0002-9604-343X
Wetzel, Andrew0000-0003-0603-8942
Hopkins, Philip F.0000-0003-3729-1684
Chan, T. K.0000-0003-2544-054X
Kereš, Dušan0000-0002-1666-7067
Additional Information:© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2018 March 13. Received 2018 March 6; in original form 2018 January 11. We thank the referee, Danail Obreschkow, for a constructive report and Alyson Brooks and Pascal Elahi for helpful discussions. K.E. acknowledges support from a Berkeley graduate fellowship, a Hellman award for graduate study, and an NSF Graduate Research Fellowship. E.Q. and K.E. are supported by a Simons Investigator Award from the Simons Foundation and by an NSF grant AST-1715070. M.B.K. acknowledges support from NSF grant AST-1517226 and from NASA grants NNX17AG29G and HST-AR-13888, HST-AR-13896, HST-AR-14282, HST-AR-14554, HST-GO-12914, and HST-GO-14191 from STScI. D.R.W. is supported by a fellowship from the Alfred P. Sloan Foundation. A.W. was supported by NASA through grants HST-GO-14734 and HST-AR-15057 from STScI. Support for P.F.H. was provided by an Alfred P. Sloan Research Fellowship, NASA ATP grant NNX14AH35G, NSF Collaborative Research grant #1411920, and CAREER grant #1455342. D.K. and T.K.C. were supported by NSF grants AST-1412153 and AST-1715101 and by the Cottrell Scholar Award from the Research Corporation for Science Advancement. CAFG was supported by NSF through grants AST-1412836, AST-1517491, AST-1715216; by CAREER award AST-1652522; and by NASA through grant NNX15AB22G. We ran numerical calculations on the Caltech compute cluster ‘Wheeler’, allocations TG-AST130039 & TG-AST150080 granted by the Extreme Science and Engineering Discovery Environment (XSEDE) supported by the NSF, and the NASA HEC Program through the NAS Division at Ames Research Center and the NCCS at Goddard Space Flight Center. The analysis in this paper relied on the PYTHON packages NUMPY (Van Der Walt, Colbert & Varoquaux 2011), MATPLOTLIB (Hunter 2007), and ASTROPY (Astropy Collaboration et al. 2013).
Funding AgencyGrant Number
University of California, BerkeleyUNSPECIFIED
Hellman FellowshipUNSPECIFIED
NSF Graduate Research FellowshipUNSPECIFIED
Simons FoundationUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Cottrell Scholar of Research CorporationUNSPECIFIED
Subject Keywords:galaxies: dwarf, galaxies: irregular, galaxies: kinematics and dynamics
Record Number:10.1093/mnras/sty730
Persistent URL:
Official Citation:Kareem El-Badry, Jeremy Bradford, Eliot Quataert, Marla Geha, Michael Boylan-Kolchin, Daniel R Weisz, Andrew Wetzel, Philip F Hopkins, T K Chan, Alex Fitts, Dušan Kereš, Claude-André Faucher-Giguère; Gas kinematics in FIRE simulated galaxies compared to spatially unresolved H I observations, Monthly Notices of the Royal Astronomical Society, Volume 477, Issue 2, 21 June 2018, Pages 1536–1548,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:87412
Deposited By: George Porter
Deposited On:27 Jun 2018 21:59
Last Modified:27 Jun 2018 21:59

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