Connection Between the Circumgalactic Medium and the Interstellar Medium
  of Galaxies: Results from the COS-GASS Survey
  We present a study exploring the nature and properties of the Circum-Galactic
Medium (CGM) and its connection to the atomic gas content in the interstellar
medium (ISM) of galaxies as traced by the HI 21cm line. Our sample includes 45
low-z (0.026-0.049) galaxies from the GALEX Arecibo SDSS Survey. Their CGM was
probed via absorption in the spectra of background Quasi-Stellar Objects at
impact parameters of 63 to 231kpc. The spectra were obtained with the Cosmic
Origins Spectrograph aboard the Hubble Space Telescope. We detected neutral
hydrogen (Ly$\alpha$ absorption-lines) in the CGM of 92% of the galaxies. We
find the radial profile of the CGM as traced by the Ly$\alpha$ equivalent width
can be fit as an exponential with a scale length of roughly the virial radius
of the dark matter halo. We found no correlation between the orientation of
sightline relative to the galaxy major axis and the Ly$\alpha$ equivalent
width. The velocity spread of the circumgalactic gas is consistent with that
seen in the atomic gas in the interstellar medium. We find a strong correlation
(99.8% confidence) between the gas fraction (M(HI)/M*) and the
impact-parameter-corrected Ly$\alpha$ equivalent width. This is stronger than
the analogous correlation between corrected Ly$\alpha$ equivalent width and
SFR/M* (97.5% confidence). These results imply a physical connection between
the HI disk and the CGM, which is on scales an order-of-magnitude larger. This
is consistent with the picture in which the HI disk is nourished by accretion
of gas from the CGM.
