We present initial results from the \textit{ COS and Gemini Mapping the Circumgalactic Medium} (\mbox{ CGMCGM} $\equiv$ CGM$^{ 2}$) survey. The CGM$^{ 2}$ survey consists of 1689 galaxies, all with high-quality Gemini GMOS spectra, within 1 Mpc of twenty-two $z \lesssim 1$ quasars, all with S/N$\sim$10 { \emph{ HST/COS}} G130M$+$G160M spectra. For 572 of these galaxies having stellar masses $10^{ 7} M_{ \odot} < M_{ \star} < 10^{ 11} M_{ \odot}$ and $z \lesssim 0.5$, we show that the \ion{ H}{ 1} covering fraction above a threshold of \NHI$>10^{ 14} $cm$^{ -2}$ is $\gtrsim 0.5$ within 1.5 virial radii ($R_{ \rm vir} \sim R_{ 200m}$). We examine the \ion{ H}{ 1} kinematics and find that the majority of absorption lies within $\pm$ 250 km s$^{ -1}$ of the galaxy systemic velocity. We examine \ion{ H}{ 1} covering fractions over a range of impact parameters to infer a characteristic size of the CGM, $R^{ 14}_{ \rm CGM}$, as a function of galaxy mass. $R^{ 14}_{ \rm CGM}$ is the impact parameter at which the probability of observing an absorber with \NHI $>$ 10$^{ 14}$ cm$^{ -2}$ is $>$ 50\%. In this framework, the radial extent of the CGM of $M_{ \star} > 10^{ 9.9} M_{ \odot}$ galaxies is $R^{ 14}_{ \rm CGM} = 346^{ +57}_{ -53}$ kpc or $R^{ 14}_{ \rm CGM} \simeq 1.2R_{ \rm vir}$. Intermediate-mass galaxies with $10^{ 9.2} < M_{ \star}/M_{ \odot} < 10^{ 9.9}$ have an extent of $R^{ 14}_{ \rm CGM} = 353^{ +64}_{ -50}$ kpc or $R^{ 14}_{ \rm CGM} \simeq 2.4R_{ \rm vir}$. Low-mass galaxies, $M_{ \star} < 10^{ 9.2} M_{ \odot}$, show a smaller physical scale $R^{ 14}_{ \rm CGM} = 177_{ -65}^{ +70}$ kpc and extend to $R^{ 14}_{ \rm CGM} \simeq 1.6R_{ \rm vir}$. Our analysis suggests that using $R_{ \rm vir}$ as a proxy for the characteristic radius of the CGM likely underestimates its extent.
Categories: astro-ph.GA