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The no-spin zone: rotation vs dispersion support in observed and simulated dwarf galaxies

Wheeler, Coral and Pace, Andrew B. and Bullock, James S. and Boylan-Kolchin, Michael and Oñorbe, José and Fitts, Alex and Hopkins, Philip F. and Kereš, Dušan (2017) The no-spin zone: rotation vs dispersion support in observed and simulated dwarf galaxies. Monthly Notices of the Royal Astronomical Society, 465 (2). pp. 2420-2431. ISSN 0035-8711.

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We perform a systematic Bayesian analysis of rotation vs. dispersion support (v_(rot)/σ) in 40 dwarf galaxies throughout the Local Volume (LV) over a stellar mass range 10^(3.5) M_⊙ < M⋆ < 10^8 M_⊙. We find that the stars in ∼90% of the LV dwarf galaxies studied -- both satellites and isolated systems -- are dispersion-supported. In particular, we show that 7/10 *isolated* dwarfs in our sample have stellar populations with v_(rot)/σ<0.6. All have v_(rot)/σ≲2. These results challenge the traditional view that the stars in gas-rich dwarf irregulars (dIrrs) are distributed in cold, rotationally-supported stellar disks, while gas-poor dwarf spheroidals (dSphs) are kinematically distinct in having dispersion-supported stars. We see no clear trend between v_(rot)/σ and distance to the closest L⋆ galaxy, nor between v_(rot)/σ and M⋆ within our mass range. We apply the same Bayesian analysis to four FIRE hydrodynamic zoom-in simulations of isolated dwarf galaxies (10^9M⊙<M_(vir)<10^(10)M⊙) and show that the simulated *isolated* dIrr galaxies have stellar ellipticities and stellar v_(rot)/σ ratios that are consistent with the observed population of dIrrs *and* dSphs without the need to subject these dwarfs to any external perturbations or tidal forces. We posit that most dwarf galaxies form as puffy, dispersion-supported systems, rather than cold, angular momentum-supported disks. If this is the case, then transforming a dIrr into a dSph may require little more than removing its gas.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Pace, Andrew B.0000-0002-6021-8760
Bullock, James S.0000-0003-4298-5082
Boylan-Kolchin, Michael0000-0002-9604-343X
Fitts, Alex0000-0002-8928-6011
Hopkins, Philip F.0000-0003-3729-1684
Kereš, Dušan0000-0002-1666-7067
Additional Information:© 2016 Oxford University Press. Received: 03 November 2015. Revision Received: 04 October 2016. Accepted: 04 October 2016. Published: 08 October 2016. We thank the anonymous referee, for comments that made the paper clearer and more robust. We also thank Josh Simon, Marla Geha, Ngoc Nhung Ho, Nicolas Martin, Serge Demers, Evan Kirby, and Ryan Leaman for generously providing their data for this project. We further thank Ryan Leaman and Evan Kirby for very helpful discussions. This work used computational resources granted by NASA Advanced Supercomputing (NAS) Division, NASA Center for Climate Simulation, Teragrid, and by the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation grant numbers OCI-1053575 and ACI-1053575, the latter through allocation AST140080 (PI: Boylan-Kolchin). CW acknowledges support from the Josephine de Karman Fellowship Trust. CW and JB were supported in part by Hubble Space Telescope grants HST-AR-13921.002-A and HST-AR-13888.003-A. MBK acknowledges support from NASA through Hubble Space Telescope theory grants (programs AR-12836 and AR-13888) from the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS5-26555. MBK and AF acknowledge support from NSF grant AST-1517226. OE acknowledges funds from NSF grant NSF-AST 1518291 and Hubble Space Telescope grant HST-GO-13343.09-A. Support for PFH was provided by an Alfred P. Sloan Research Fellowship, NASA ATP Grant NNX14AH35G, and NSF Collaborative Research Grant #1411920 and CAREER grant #1455342. Some numerical calculations were run on the Caltech compute cluster ‘Zwicky’ (NSF MRI award #PHY-0960291) and allocation TG-AST130039 granted by the Extreme Science and Engineering Discovery Environment (XSEDE) supported by the NSF. DK received support from XSEDE allocation TG-AST-120025 (PI: Kereš) National Science Foundation grant number AST-1412153, and funds from the University of California, San Diego.
Group:TAPIR, Astronomy Department
Funding AgencyGrant Number
Josephine de Karman Fellowship TrustUNSPECIFIED
NASA Hubble FellowshipAR-12836
NASA Hubble FellowshipAR-13888
Alfred P. Sloan FoundationUNSPECIFIED
University of California, San DiegoUNSPECIFIED
Subject Keywords:galaxies: dwarf – galaxies: formation – galaxies: star formation – galaxies: kinematics and dynamics – Local Group
Issue or Number:2
Record Number:CaltechAUTHORS:20151118-080725780
Persistent URL:
Official Citation:Coral Wheeler, Andrew B. Pace, James S. Bullock, Michael Boylan-Kolchin, Jose Oñorbe, Oliver D. Elbert, Alex Fitts, Philip F. Hopkins, Dušan Kereš; The no-spin zone: rotation versus dispersion support in observed and simulated dwarf galaxies. Mon Not R Astron Soc 2017; 465 (2): 2420-2431. doi: 10.1093/mnras/stw2583
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:62187
Deposited By: Tony Diaz
Deposited On:18 Nov 2015 18:06
Last Modified:09 Mar 2020 13:19

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