The Splashback Feature around DES Galaxy Clusters: Galaxy Density and Weak Lensing Profiles

Abstract

Splashback refers to the process of matter that is accreting onto a dark matter halo reaching its first orbital apocenter and turning around in its orbit. The clustercentric radius at which this process occurs, r sp , defines a halo boundary that is connected to the dynamics of the cluster. A rapid decline in the halo profile is expected near r sp . We measure the galaxy number density and weak lensing mass profiles around REDMAPPER galaxy clusters in the first-year Dark Energy Survey (DES) data. For a cluster sample with mean M 200m mass ≈2.5×1014 M e , we find strong evidence of a splashback-like steepening of the galaxy density profile and measure r sp =1.13± 0.07 h −1 Mpc, consistent with the earlier Sloan Digital Sky Survey measurements of More et al. and Baxter et al. Moreover, our weak lensing measurement demonstrates for the first time the existence of a splashback-like steepening of the matter profile of galaxy clusters. We measure r sp =1.34±0.21 h −1 Mpc from the weak lensing data, in good agreement with our galaxy density measurements. For different cluster and galaxy samples, we find that, consistent with ΛCDM simulations, r sp scales with R 200m and does not evolve with redshift over the redshift range of 0.3-0.6. We also find that potential systematic effects associated with the REDMAPPER algorithm may impact the location of r sp . We discuss the progress needed to understand the systematic uncertainties and fully exploit forthcoming data from DES and future surveys, emphasizing the importance of more realistic mock catalogs and independent cluster samples.

Signatures of self-interacting dark matter on cluster density profile and subhalo distributions

“…It should be noted that, in fact, galaxy number density profiles from observations follow the particle distributions from simulations more closely than subhalo distributions (see Fig. 4 in [55]). This can be attributed to tidal stripping (both real and artificial) of subhalos in the simulation causing subhalos to pass below the mass-resolution.…”

“…This effect can be probed using the stacked ∆Σ profiles of clusters, measured via weak lensing. In fact, such measurements around similar mass objects have been performed already [55]. Current uncertainties are already at a level sufficient to probe interactions with σ T ≥ 3 cm 2 /g.…”

“…It is also possible to place constraints on the strength of self-interaction by using the stacked projected satellite counts around the clusters, which has also been measured in [54][55][56]68]. In fact this measurement has much higher statistical signal to noise compared to the lensing measurements referred to above.…”

Persistence of the colour–density relation and efficient environmental quenching to z ∼ 1.4

“…These values are also well in excess of the average time required for galaxies to move to their first pericentric passage after being accreted by their parent group or cluster at the median redshift of the ORELSE sample (Wetzel 2011;Wetzel et al 2013). Such a long delay time is supported by recent evidence taken from SDSS and redMaPPer clusters at low-to intermediate-redshift that show appreciable populations of galaxies far from center of clusters thought to have survived their first passage through the cluster to make it to their first apogee (i.e., "splashback" galaxies, More et al 2016;Baxter et al 2017;Chang et al 2018). The fact that the bulk of group/cluster galaxies remain largely unperturbed in their star-formation activity at least through their initial pericentric passage and that an additional ∼0.5-1.5 Gyr is allowed to elapse prior to the inception of quenching appears to place most galaxies in the more rarefied regions of their parent groups/clusters when quenching is initiated.…”

Filament profiles from WISExSCOS galaxies as probes of the impact of environmental effects

“…The average properties of these objects are known (e.g., Kravtsov & Borgani 2012;Bykov et al 2015;Walker et al 2019), thanks to numerical simulations, but also to actual observations of galaxies in optical and near-infrared, of hot gas via the Sunyaev-Zel'dovich effect (SZ, Sunyaev & Zeldovich 1970, 1972 and in the X-rays, and of dark matter via gravitational lensing. As a matter of fact, around these structures, dark matter and hot gas universal density profiles have already been derived (e.g., Nagai et al 2007;Arnaud et al 2010;Planck Collaboration et al 2013;Bartalucci et al 2017;Ghirardini et al 2019), and a global picture of the distribution and of the properties (such as the star formation rate and the stellar mass) of galaxies that fall into their gravitational potential has already been drawn (e.g., Mahajan & Raychaudhury 2009;Mahajan et al 2011;Baxter et al 2017;Chang et al 2018;Adhikari et al 2019;Pintos-Castro et al 2019).…”