Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evidence for galaxy quenching in the green valley caused by a lack of a
  circumgalactic medium   The relationship between a galaxy's properties and its circumgalactic medium
(CGM) provides a unique view of how galaxies evolve. We present an interesting
edge-on (i=86 degrees) disk galaxy (G1547) where the CGM is probed by a
background quasar at a distance of 84 kpc and within 10 degrees of the galaxy
major axis. G1547 does not have any detectable CGM absorption down to stringent
limits, covering HI (EW$_r$<0.02A, log(N(HI)/cm$^{-2}$)<12.6) and a range of
low and high ionisation absorption lines (OI, CII, NII, SiII, CIII, NIII,
SiIII, CIV, SiIV, NV and OVI). This system is rare, given the covering fraction
of $1.00_{-0.04}^{+0.00}$ for sub-L* galaxies within 50-100 kpc of quasar
sightlines. G1547 has a low SFR (1.1 M$_{\odot}$yr$^{-1}$), SSFR
($1.5\times10^{-10}$yr$^{-1}$) and $\Sigma_{\rm SFR}$ (0.06
M$_{\odot}$yr$^{-1}$kpc$^{-2}$) and does not exhibit AGN or star-formation
driven outflows. Compared to the general population of galaxies, G1547 is in
the green valley and has an above average metallicity with a negative gradient.
When compared to other HI absorption-selected galaxies, we find that quiescent
galaxies with log(SSFR/yr$^{-1})<-11$ have a low probability (4/12) of
possessing detectable HI in their CGM, while all galaxies (40/40) with
log(SSFR/yr$^{-1})>-11$ have HI absorption. We conclude that SSFR is a good
indicator of the presence of HI CGM. Interestingly however, G1547 is the only
galaxy with log(SSFR/yr$^{-1})>-11$ that has no detectable CGM. Given the
properties of G1547, and its absent CGM, it is plausible that G1547 is
undergoing quenching due to a lack of accreting fuel for star-formation, with
an estimated quenching timescale of $4\pm1$ Gyr. G1547 provides a unique
perspective into the external mechanisms that could explain the migration of
galaxies into the green valley.

20
The categories of this paper are: acc-phys
16
The categories of this paper are: stat
2
The categories of this paper are: math
34
The categories of this paper are: chem-ph
0
The categories of this paper are: hep-ph
24
The categories of this paper are: dg-ga
3
The categories of this paper are: physics
17
The categories of this paper are: q-fin
18
The categories of this paper are: econ
27
The categories of this paper are: comp-gas
15
The categories of this paper are: nucl-ex
8
The categories of this paper are: hep-ex
25
The categories of this paper are: patt-sol
1
The categories of this paper are: cs
21
The categories of this paper are: adap-org
12
The categories of this paper are: nucl-th