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تسجيل مستخدم جديدCGM$^{2}$ I: The Extent of the Circumgalactic Medium Traced by Neutral Hydrogen
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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.
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