Kavli Affiliate: Robert A. Simcoe
| First 5 Authors: Zhijie Qu, Hsiao-Wen Chen, Gwen C. Rudie, Fakhri S. Zahedy, Sean D. Johnson
| Summary:
This paper presents a systematic study of the photoionization and
thermodynamic properties of the cool circumgalactic medium (CGM) as traced by
rest-frame ultraviolet absorption lines around 26 galaxies at redshift
$zlesssim1$. The study utilizes both high-quality far-ultraviolet and optical
spectra of background QSOs and deep galaxy redshift surveys to characterize the
gas density, temperature, and pressure of individual absorbing components and
to resolve their internal non-thermal motions. The derived gas density spans
more than three decades, from $log (n_{rm H}/{rm cm^{-3}}) approx -4$ to
$-1$, while the temperature of the gas is confined in a narrow range of $log
(T/{rm K})approx 4.3pm 0.3$. In addition, a weak anti-correlation between
gas density and temperature is observed, consistent with the expectation of the
gas being in photoionization equilibrium. Furthermore, decomposing the observed
line widths into thermal and non-thermal contributions reveals that more than
30% of the components at $zlesssim 1$ exhibit line widths driven by
non-thermal motions, in comparison to $<20$% found at $zapprox 2$-3.
Attributing the observed non-thermal line widths to intra-clump turbulence, we
find that massive quenched galaxies on average exhibit higher non-thermal
broadening/turbulent energy in their CGM compared to star-forming galaxies at
$zlesssim 1$. Finally, strong absorption features from multiple ions covering
a wide range of ionization energy (e.g., from Mg II to O IV) can be present
simultaneously in a single absorption system with kinematically aligned
component structure, but the inferred pressure in different phases may differ
by a factor of $approx 10$.
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