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Detection of hot, metal-enriched outflowing gas around $zapprox,$2.3 star-forming galaxies in the Keck Baryonic Structure Survey | | Monica L. Turner
; Joop Schaye
; Charles C. Steidel
; Gwen C. Rudie
; Allison L. Strom
; | | Date: |
30 Oct 2014 | | Abstract: | We use quasar absorption lines to study the physical conditions in the
circumgalactic medium of redshift $zapprox 2.3$ star-forming galaxies taken
from the Keck Baryonic Structure Survey (KBSS). In Turner et al. 2014 we used
the pixel optical depth technique to show that absorption by HI and the metal
ions OVI, NV, CIV, CIII and SiIV is strongly enhanced within $|Delta
v|lesssim170$ km/s and projected distances $|d|lesssim180$ proper kpc from
sightlines to the background quasars. Here we demonstrate that the OVI
absorption is also strongly enhanced at fixed HI, CIV, and SiIV optical depths,
and that this enhancement extends out to $sim350$ km/s. At fixed HI the
increase in the median OVI optical depth near galaxies is 0.3-0.7 dex and is
detected at 2--3-$sigma$ confidence for all seven HI bins that have
$log_{10} au_{
m HI}ge-1.5$. We use ionisation models to show that the
observed strength of OVI as a function of HI is consistent with enriched,
photoionised gas for pixels with $ au_{
m HI}gtrsim10$. However, for pixels
with $ au_{
m HI} lesssim 1$ this would lead to implausibly high
metallicities at low densities if the gas were photoionised by the background
radiation. This indicates that the galaxies are surrounded by gas that is
sufficiently hot to be collisionally ionised ($T > 10^5,$K) and that a
substantial fraction of the hot gas has a metallicity $gtrsim 10^{-1}$ of
solar. Given the high metallicity and large velocity extent (out to
$sim1.5 imes v_{
m circ}$) of this gas, we conclude that we have detected
hot, metal enriched outflows arising from star-forming galaxies. | | Source: | arXiv, 1410.8214 | | Services: | Forum | Review | PDF | Favorites | |
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