On The Effect of Environment on Line Emission from the Circumgalactic Medium. (arXiv:1906.01643v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_H/0/1/0/all/0/1">Huanian Zhang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zaritsky_D/0/1/0/all/0/1">Dennis Zaritsky</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Behroozi_P/0/1/0/all/0/1">Peter Behroozi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Werk_J/0/1/0/all/0/1">Jessica Werk</a>
We measure differences in the emission line flux from the circumgalactic
medium, CGM, of galaxies in different environments. Such differences could be a
critical clue in explaining a range of galaxy properties that depend on
environment. Using large samples of stacked archival spectra from the Sloan
Digital Sky Survey, we find that the H$alpha$ + [N {small II}] emission line
flux from the CGM within 50 kpc of $sim$ L$^*$ galaxies is lower both for
galaxies that lie within a projected distance of $sim$ 500 kpc from a massive
($M_*>10^{11} M_odot$) galaxy and for galaxies in richer/denser environments.
The environmental differences are statistically significant even after we
control for galaxy mass and morphology. We interpret these observations as a
direct signature of environmentally-caused strangulation. We present a simple,
heuristic model for the effect of a massive parent galaxy. In this model, the
CGM cool gas fraction within 50 kpc is significantly decreased for galaxies
that lie within 700 kpc of a massive galaxy, with about 80% of the cool gas
removed even when the galaxy is at a distance of 500 kpc from its massive
parent. However, we discuss alternative physical causes for the observed
behavior and discuss ways forward in addressing open questions.
We measure differences in the emission line flux from the circumgalactic
medium, CGM, of galaxies in different environments. Such differences could be a
critical clue in explaining a range of galaxy properties that depend on
environment. Using large samples of stacked archival spectra from the Sloan
Digital Sky Survey, we find that the H$alpha$ + [N {small II}] emission line
flux from the CGM within 50 kpc of $sim$ L$^*$ galaxies is lower both for
galaxies that lie within a projected distance of $sim$ 500 kpc from a massive
($M_*>10^{11} M_odot$) galaxy and for galaxies in richer/denser environments.
The environmental differences are statistically significant even after we
control for galaxy mass and morphology. We interpret these observations as a
direct signature of environmentally-caused strangulation. We present a simple,
heuristic model for the effect of a massive parent galaxy. In this model, the
CGM cool gas fraction within 50 kpc is significantly decreased for galaxies
that lie within 700 kpc of a massive galaxy, with about 80% of the cool gas
removed even when the galaxy is at a distance of 500 kpc from its massive
parent. However, we discuss alternative physical causes for the observed
behavior and discuss ways forward in addressing open questions.
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