THE COS-DWARFS SURVEY: THE CARBON RESERVOIR AROUND SUB-<i>L</i>* GALAXIES

Abstract

We report new observations of circumgalactic gas from the COS-Dwarfs survey,\na systematic investigation of the gaseous halos around 43 low-mass z $\\leq$ 0.1\ngalaxies using background QSOs observed with the Cosmic Origins Spectrograph.\nFrom the projected 1D and 2D distribution of C IV absorption, we find that C IV\nabsorption is detected out to ~ 0.5 R$_{vir}$ of the host galaxies. The C IV\nabsorption strength falls off radially as a power law and beyond 0.5 R$_{vir}$,\nno C IV absorption is detected above our sensitivity limit of ~ 50-100 m$\\AA$.\nWe find a tentative correlation between detected C IV absorption strength and\nstar formation, paralleling the strong correlation seen in highly ionized\noxygen for L~L* galaxies by the COS-Halos survey. The data imply a large carbon\nreservoir in the CGM of these galaxies, corresponding to a minimum carbon mass\nof $\\gtrsim$ 1.2$\\times 10^6$ $M_\\odot$ out to ~ 110 kpc. This mass is\ncomparable to the carbon mass in the ISM and more than the carbon mass\ncurrently in stars of these galaxies. The C IV absorption seen around these\nsub-L* galaxies can account for almost two-thirds of all $W_r$&gt; 100 m$\\AA$ C IV\nabsorption detected at low z. Comparing the C IV covering fraction with\nhydrodynamical simulations, we find that an energy-driven wind model is\nconsistent with the observations whereas a wind model of constant velocity\nfails to reproduce the CGM or the galaxy properties.\n