THE COS-DWARFS SURVEY: THE CARBON RESERVOIR AROUND SUB-L GALAXIES

We report new observations of circumgalactic gas from the COS-Dwarfs survey, a systematic investigation of the gaseous halos around 43 low-mass z <= 0.1 galaxies using background QSOs observed with the Cosmic Origins Spectrograph. From the projected one-dimensional and two-dimensional distribution of C iv absorption, we find that Civ is detected out to approximate to 100 kpc (corresponding roughly to approximate to 0.5 R-vir) of the host galaxies. The Civ absorption strength falls off radially as a power law, and beyond approximate to 0.5 R-vir, no Civ absorption is detected above our sensitivity limit of approximate to 50-100 m angstrom . We find a tentative correlation between detected C iv absorption strength and star formation, paralleling the strong correlation seen in highly ionized oxygen for L similar to L* galaxies by the COS-Halos survey. The data imply a large carbon reservoir in the circumgalactic medium (CGM) of these galaxies, corresponding to a minimum carbon mass of greater than or similar to 1.2 x 10(6) M circle dot out to similar to 110 kpc. This mass is comparable to the carbon mass in the interstellar medium and exceeds the carbon mass currently in the stars of these galaxies. The Civ absorption seen around these sub-L* galaxies can account for almost two-thirds of all W-r >= 100 m angstrom C iv absorption detected at low z. Comparing the Civ covering fraction with hydrodynamical simulations, we find that an energy-driven wind model is consistent with the observations whereas a wind model of constant velocity fails to reproduce the CGM or the galaxy properties.