Environment from cross-correlations: connecting hot gas and the quenching of galaxies. (arXiv:1907.06645v1 [astro-ph.GA])

Environment from cross-correlations: connecting hot gas and the quenching of galaxies. (arXiv:1907.06645v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Kukstas_E/0/1/0/all/0/1">Egidijus Kukstas</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+McCarthy_I/0/1/0/all/0/1">Ian G. McCarthy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Baldry_I/0/1/0/all/0/1">Ivan K. Baldry</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Font_A/0/1/0/all/0/1">Andreea S. Font</a>

The observable properties of galaxies are known to depend on both internal
processes and the external environment. In terms of the environmental role, we
still do not have a clear picture of the processes driving the transformation
of galaxies. This may be due to the fact that these environmental processes
depend on local physical conditions (e.g., local tidal force or hot gas
density), whereas observations typically probe only broad-brush proxies for
these conditions (e.g., host halo mass, distance to the N^th nearest neighbour,
etc.). Here we propose a new method that directly links galaxies to their local
environments, by using spatial cross-correlations of galaxy catalogues with
maps from large-scale structure surveys (e.g., thermal Sunyaev-Zel’dovich [tSZ]
effect, diffuse X-ray emission, weak lensing of galaxies or the CMB). We focus
here on the quenching of galaxies and its link to local hot gas properties.
Maps of galaxy overdensity and quenched fraction excess are constructed from
volume-limited SDSS catalogs, which are cross-correlated with maps of tSZ
effect from Planck and X-ray emission from ROSAT. Strong signals out to Mpc
scales are detected for all cross-correlations and are compared to predictions
from cosmological hydrodynamical simulations (the EAGLE and BAHAMAS
simulations). The simulations successfully reproduce many, but not all, of the
observed power spectra, with an indication that environmental quenching may be
too efficient in the simulations. We demonstrate that the cross-correlations
are sensitive to both the internal and external processes responsible for
quenching. The methods outlined in this paper can be easily adapted to other
observables and, with upcoming surveys, will provide a stringent direct test of
physical models for environmental transformation.

The observable properties of galaxies are known to depend on both internal
processes and the external environment. In terms of the environmental role, we
still do not have a clear picture of the processes driving the transformation
of galaxies. This may be due to the fact that these environmental processes
depend on local physical conditions (e.g., local tidal force or hot gas
density), whereas observations typically probe only broad-brush proxies for
these conditions (e.g., host halo mass, distance to the N^th nearest neighbour,
etc.). Here we propose a new method that directly links galaxies to their local
environments, by using spatial cross-correlations of galaxy catalogues with
maps from large-scale structure surveys (e.g., thermal Sunyaev-Zel’dovich [tSZ]
effect, diffuse X-ray emission, weak lensing of galaxies or the CMB). We focus
here on the quenching of galaxies and its link to local hot gas properties.
Maps of galaxy overdensity and quenched fraction excess are constructed from
volume-limited SDSS catalogs, which are cross-correlated with maps of tSZ
effect from Planck and X-ray emission from ROSAT. Strong signals out to Mpc
scales are detected for all cross-correlations and are compared to predictions
from cosmological hydrodynamical simulations (the EAGLE and BAHAMAS
simulations). The simulations successfully reproduce many, but not all, of the
observed power spectra, with an indication that environmental quenching may be
too efficient in the simulations. We demonstrate that the cross-correlations
are sensitive to both the internal and external processes responsible for
quenching. The methods outlined in this paper can be easily adapted to other
observables and, with upcoming surveys, will provide a stringent direct test of
physical models for environmental transformation.

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