부산대학교 도서관

We present evidence for the existence of the splashback radius in galaxy clusters selected using the Sunyaev-Zel'dovich effect. We show that the deprojected cross-correlation of galaxy clusters found in the Planck survey with galaxies detected photometrically in the Pan-STARRS survey, shows a sharp steepening feature (a logarithmic slope steeper than $-3$), which we associate with the splashback radius. We infer the three-dimensional splashback radius for the SZ cluster sample to be $r_{\rm sp}=1.85_{-0.30}^{+0.26}$ $h^{-1}$Mpc, where the cluster sample has an average halo mass $M_{500c}=3.0\times10^{14}h^{-1}M_\odot$ at an average redshift of $z=0.18$. The inferred value of the splashback radius appears consistent with the expected location for dark matter halos in the standard cold dark matter paradigm. However, given the limited precision of our measurements, we cannot conclusively rule out the smaller splashback radius measured so far in the literature for optically selected galaxy clusters. We show that the splashback radius does not depend upon the galaxy magnitude for galaxies fainter than $M_i-5\log h=-19.44$, and is present at a consistent location in galaxy populations divided by color. The presence of the splashback radius in the star-forming galaxy population could potentially be used to put lower limits on the quenching timescales for galaxies. We can marginally rule out the contamination of the star-forming galaxy sample by quenched galaxies, but the results would need further verification with deeper datasets.
Comment: 17 pages, 16 figures, submitted and defended as a Masters thesis by Dominik Zuercher at the DPHYS in ETH Zurich in June 2018