TY - JOUR
T1 - Gas kinematics in FIRE simulated galaxies compared to spatially unresolved HI observations
AU - El-Badry, Kareem
AU - Bradford, Jeremy
AU - Quataert, Eliot
AU - Geha, Marla
AU - Boylan-Kolchin, Michael
AU - Weisz, Daniel R.
AU - Wetzel, Andrew
AU - Hopkins, Philip F.
AU - Chan, T. K.
AU - Fitts, Alex
AU - Kereš, Dušan
AU - Faucher-Giguère, Claude André
N1 - Publisher Copyright:
© 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.
PY - 2018/6/21
Y1 - 2018/6/21
N2 - 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, HI-detected galaxies with Mstar = 107-11M⊙ and compare to the simulated galaxies. At Mstar ≳ 1010M⊙, 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 Mstar = 108-10M⊙, 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.
AB - 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, HI-detected galaxies with Mstar = 107-11M⊙ and compare to the simulated galaxies. At Mstar ≳ 1010M⊙, 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 Mstar = 108-10M⊙, 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.
KW - Galaxies: Dwarf
KW - Galaxies: Irregular
KW - Galaxies: Kinematics and dynamics
UR - http://www.scopus.com/inward/record.url?scp=85047158222&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85047158222&partnerID=8YFLogxK
U2 - 10.1093/mnras/sty730
DO - 10.1093/mnras/sty730
M3 - Article
C2 - 30713356
AN - SCOPUS:85047158222
SN - 0035-8711
VL - 477
SP - 1536
EP - 1548
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 2
ER -