Zusammenfassung
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 21 cm 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 231 kpc. 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 about 0.85 times the virial
radius of the dark matter halo. We found no correlation between the orientation
of the galaxies and their Ly\alpha equivalent widths. The velocity spread of
the circumgalactic gas is consistent with that seen in the atomic gas in the
interstellar medium. We find strong correlations (99.5% confidence) between the
gas fraction (M(HI)/M*) and the impact parameter corrected neutral hydrogen
content in the CGM. These are stronger than the analogous correlations between
the star-formation rates and CGM gas content (97% confidence). These results
imply a physical connection between the H I disk and the CGM on scales an
order-of-magnitude larger. This is consistent with the picture in which the H I
disk is nourished by accretion of gas from the CGM.
Nutzer