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28 March 2024 |
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Article overview
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When the Jeans don't fit: How stellar feedback drives stellar kinematics and complicates dynamical modeling in low-mass galaxies | Kareem El-Badry
; Andrew R. Wetzel
; Marla Geha
; Eliot Quataert
; Philip F. Hopkins
; Dusan Kereš
; T.K. Chan
; Claude-André Faucher-Giguère
; | Date: |
13 Oct 2016 | 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 (FIRE)
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 $sim 20\%$ in dynamical mass estimates, even if full
3-dimensional stellar kinematics -- including the orbital anisotropy -- are
known exactly. When orbital anisotropy is $ extit{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 $ extit{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. | Source: | arXiv, 1610.4232 | Services: | Forum | Review | PDF | Favorites |
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