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Title: When the Jeans Do Not Fit: How Stellar Feedback Drives Stellar Kinematics and Complicates Dynamical Modeling in Low-mass Galaxies

Abstract

In low-mass galaxies, stellar feedback can drive gas outflows that generate non-equilibrium fluctuations in the gravitational potential. Using cosmological zoom-in baryonic simulations from the Feedback in Realistic Environments project, we investigate how these fluctuations affect stellar kinematics and the reliability of Jeans dynamical modeling in low-mass galaxies. We find that stellar velocity dispersion and anisotropy profiles fluctuate significantly over the course of galaxies’ starburst cycles. We therefore predict an observable correlation between star formation rate and stellar kinematics: dwarf galaxies with higher recent star formation rates should have systemically higher stellar velocity dispersions. This prediction provides an observational test of the role of stellar feedback in regulating both stellar and dark-matter densities in dwarf galaxies. We find that Jeans modeling, which treats galaxies as virialized systems in dynamical equilibrium, overestimates a galaxy’s dynamical mass during periods of post-starburst gas outflow and underestimates it during periods of net inflow. Short-timescale potential fluctuations lead to typical errors of ∼20% in dynamical mass estimates, even if full three-dimensional stellar kinematics—including the orbital anisotropy—are known exactly. When orbital anisotropy is not known a priori, typical mass errors arising from non-equilibrium fluctuations in the potential are larger than those arising from the mass-anisotropy degeneracy. However,more » Jeans modeling alone cannot reliably constrain the orbital anisotropy, and problematically, it often favors anisotropy models that do not reflect the true profile. If galaxies completely lose their gas and cease forming stars, fluctuations in the potential subside, and Jeans modeling becomes much more reliable.« less

Authors:
;  [1]; ;  [2];  [3]; ;  [4];  [5]
  1. Department of Astronomy, University of California, Berkeley, CA (United States)
  2. TAPIR, California Institute of Technology, Pasadena, CA (United States)
  3. Department of Astronomy, Yale University, New Haven, CT (United States)
  4. Department of Physics, Center for Astrophysics and Space Sciences, University of California at San Diego, La Jolla (United States)
  5. Department of Physics and Astronomy and CIERA, Northwestern University, Evanston, IL (United States)
Publication Date:
OSTI Identifier:
22663920
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 835; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANISOTROPY; BARYONS; CORRELATIONS; DENSITY; DISPERSIONS; EQUILIBRIUM; ERRORS; FEEDBACK; FLUCTUATIONS; FORECASTING; GALAXIES; MASS; NONLUMINOUS MATTER; RELIABILITY; SIMULATION; STARS; THREE-DIMENSIONAL CALCULATIONS; VELOCITY

Citation Formats

El-Badry, Kareem, Quataert, Eliot, Wetzel, Andrew R., Hopkins, Philip F., Geha, Marla, Kereš, Dusan, Chan, T. K., and Faucher-Giguère, Claude-André, E-mail: kelbadry@berkeley.edu. When the Jeans Do Not Fit: How Stellar Feedback Drives Stellar Kinematics and Complicates Dynamical Modeling in Low-mass Galaxies. United States: N. p., 2017. Web. doi:10.3847/1538-4357/835/2/193.
El-Badry, Kareem, Quataert, Eliot, Wetzel, Andrew R., Hopkins, Philip F., Geha, Marla, Kereš, Dusan, Chan, T. K., & Faucher-Giguère, Claude-André, E-mail: kelbadry@berkeley.edu. When the Jeans Do Not Fit: How Stellar Feedback Drives Stellar Kinematics and Complicates Dynamical Modeling in Low-mass Galaxies. United States. doi:10.3847/1538-4357/835/2/193.
El-Badry, Kareem, Quataert, Eliot, Wetzel, Andrew R., Hopkins, Philip F., Geha, Marla, Kereš, Dusan, Chan, T. K., and Faucher-Giguère, Claude-André, E-mail: kelbadry@berkeley.edu. Wed . "When the Jeans Do Not Fit: How Stellar Feedback Drives Stellar Kinematics and Complicates Dynamical Modeling in Low-mass Galaxies". United States. doi:10.3847/1538-4357/835/2/193.
@article{osti_22663920,
title = {When the Jeans Do Not Fit: How Stellar Feedback Drives Stellar Kinematics and Complicates Dynamical Modeling in Low-mass Galaxies},
author = {El-Badry, Kareem and Quataert, Eliot and Wetzel, Andrew R. and Hopkins, Philip F. and Geha, Marla and Kereš, Dusan and Chan, T. K. and Faucher-Giguère, Claude-André, E-mail: kelbadry@berkeley.edu},
abstractNote = {In low-mass galaxies, stellar feedback can drive gas outflows that generate non-equilibrium fluctuations in the gravitational potential. Using cosmological zoom-in baryonic simulations from the Feedback in Realistic Environments project, we investigate how these fluctuations affect stellar kinematics and the reliability of Jeans dynamical modeling in low-mass galaxies. We find that stellar velocity dispersion and anisotropy profiles fluctuate significantly over the course of galaxies’ starburst cycles. We therefore predict an observable correlation between star formation rate and stellar kinematics: dwarf galaxies with higher recent star formation rates should have systemically higher stellar velocity dispersions. This prediction provides an observational test of the role of stellar feedback in regulating both stellar and dark-matter densities in dwarf galaxies. We find that Jeans modeling, which treats galaxies as virialized systems in dynamical equilibrium, overestimates a galaxy’s dynamical mass during periods of post-starburst gas outflow and underestimates it during periods of net inflow. Short-timescale potential fluctuations lead to typical errors of ∼20% in dynamical mass estimates, even if full three-dimensional stellar kinematics—including the orbital anisotropy—are known exactly. When orbital anisotropy is not known a priori, typical mass errors arising from non-equilibrium fluctuations in the potential are larger than those arising from the mass-anisotropy degeneracy. However, Jeans modeling alone cannot reliably constrain the orbital anisotropy, and problematically, it often favors anisotropy models that do not reflect the true profile. If galaxies completely lose their gas and cease forming stars, fluctuations in the potential subside, and Jeans modeling becomes much more reliable.},
doi = {10.3847/1538-4357/835/2/193},
journal = {Astrophysical Journal},
number = 2,
volume = 835,
place = {United States},
year = {Wed Feb 01 00:00:00 EST 2017},
month = {Wed Feb 01 00:00:00 EST 2017}
}