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We present the brightest cluster galaxies (BCGs) catalog for SPectroscoic IDentification of eROSITA Sources (SPIDERS) DR14 cluster program value-added catalog. We list the 416 BCGs identified as part of this process, along with their stellar mass, star formation rates (SFRs), and morphological properties. We identified the BCGs based on the available spectroscopic data from SPIDERS and photometric data from SDSS. We computed stellar masses and SFRs of the BCGs on the basis of SDSS, WISE, and GALEX photometry using spectral energy distribution fitting. Morphological properties for all BCGs were derived by Sersic profile fitting using the software package SIGMA in different optical bands (g,r,i). We combined this catalog with the BCGs of galaxy groups and clusters extracted from the deeper AEGIS, CDFS, COSMOS, XMM-CFHTLS, and XMM-XXL surveys to study the stellar mass-halo mass relation using the largest sample of X-ray groups and clusters known to date. This result suggests that the mass growth of the central galaxy is controlled by the hierarchical mass growth of the host halo. We find a strong correlation between the stellar mass of BCGs and the mass of their host halos. This relation shows no evolution since z similar to 0.65. We measure a mean scatter of 0.21 and 0.25 for the stellar mass of BCGs in a given halo mass at low (0.1

In this work, we examine the properties with respect to environment of brightest cluster galaxies (BCGs), the most massive population of galaxies in the known Universe, and also, the link between these galaxies and the intracluster light component (ICL) within galaxy clusters. The ICL is a flat, diffuse, low surface brightness (LSB) feature thought to contain a significant fraction of stellar mass contained within galaxy clusters; it is believed primarily to be formed from stripped stars during galaxy-galaxy interactions in the cluster core. Through our work, we attempt to discern the well-known observational and theoretical tensions which exist regarding the accretion history of stellar mass in the cores of galaxy clusters, as well as attempting to address some of the commonly-known systematics that accompany such studies. In Part I (Chapters 2-3), we analyse the structural parameters of a sample of 329 optically-confirmed, X-ray selected clusters in the SPectroscopic IDentification of eROSITA Sources Survey (SPIDERS) out to z ~ 0.3 with respect to three environmental properties (velocity dispersion-based halo mass, X-ray luminosity and optical richness). We quantify the morphologies of our BCGs by modelling their light profiles using GALFIT 3 (via the SIGMA pipeline), which we also use to obtain integrated magnitude-based stellar masses. We test the software thoroughly using ~ 20,000 mock galaxies implanted across 8 arbitrary cluster fields within our sample, which include field PSF convolutions and an idealised Poisson noise component. We find that we are able to recover our SDSS r-band profiles (with similar results in i and g) accurately out to ~ 16.5 magnitudes; fainter than this, we begin to observe biases in our results, especially in recovered Sersic index; such surface brightness-dependent structural biases have important consequences for evolutionary claims regarding BCG structure. Regarding environment, we find no evidence for any correlations between the structural properties of our science sample of 198 BCGs and any of the environmental properties used here, beyond BCG stellar mass. This observed homogeneity leads us to conclude that the majority of structural evolution of BCGs is likely to have occurred at earlier cosmic epochs than z ~ 0.3, with little evidence for much evolutionary activity at more recent epochs. In Part II, (Chapters 4-5), we attempt to quantify the ICL within a sample of 19 clusters detected in XMM Cluster Survey (XCS) data, with optical counterparts in the SDSS footprint. To do so, we use deep (~ 26.8) Hyper Suprime Cam Subaru Strategic Program DR1 (HSC-SSP DR1) i-band data. We apply a rest-frame mu_B = 25 mag/arcsec^2 isophotal threshold to our clusters, below which we define light as the ICL within an aperture of R_X,500 centered on the BCG. We apply extensive masking and careful post-processing correction techniques to address the persistent challenges which face observers attempting to analyse ICL; through application of our post-processing method, we recover a significant fraction (~ 1/5) of ICL flux previously lost during processing, significantly higher than our estimate of the image background at at the same isophotal level. We find, on average, that the ICL makes up about ~ 25% of the total cluster stellar mass on average (~ 41% including the flux contained in the BCG within 50kpc); this value is well-matched with other observational studies and SAM/numerical simulations, but is significantly smaller than results from recent hydrodynamical simulations (even when measured in an observationally consistent way). We find no evidence for any links between the amount of ICL flux with cluster mass, but find a growth rate of 2-4 for the ICL between 0 < z < 0.5; however, we find no evidence for any growth in our BCGs, finding the fractional contribution of BCG light to be strongly anti-correlated with halo mass at fixed redshift. We conclude that the ICL is the dominant evolutionary component of stellar mass in clusters from z ~ 1.

This paper defines the UK Infra-red Telescope (UKIRT) Hemisphere Survey (UHS) and release of the complete J-band dataset. The UHS provides continuous coverage in the northern hemisphere from a declination of 0 deg to 60 deg by combining the existing Large Area Survey, Galactic Plane Survey and Galactic Clusters Survey conducted under the UKIRT Infra-red Deep Sky Survey (UKIDSS) programme with a new additional ~12,700 sq.deg area not covered by UKIDSS. This data release includes J-band imaging and source catalogues over the new area, which, together with UKIDSS, completes the J-band UHS coverage over the full ~17,900 sq.deg area. 98 per cent of the data in this release have passed quality control criteria, the remaining 2 per cent being scheduled for re-observation. The median 5-sigma point source sensitivity of the released data is 19.6 mag (Vega). The median full width at half-maximum of the point spread function across the dataset is 0.75 arcsec. In this paper, we outline the survey management, data acquisition, processing and calibration, quality control and archiving as well as summarising the characteristics of the released data products. The data are initially available to a limited consortium with a world-wide release scheduled for August 2018.

Data from the SPectroscopic IDentification of ERosita Sources (SPIDERS) are searched for a detection of the gravitational redshifting of light from $\sim\!20\,000$ galaxies in $\sim\!2500$ galaxy clusters using three definitions of the cluster centre: its Brightest Cluster Galaxy (BCG), the redMaPPer identified Central Galaxy (CG), or the peak of X-ray emission. Distributions of velocity offsets between galaxies and their host cluster's centre, found using observed redshifts, are created. The quantity $\hat{\Delta}$, the average of the radial velocity difference between the cluster members and the cluster systemic velocity, reveals information on the size of a combination of effects on the observed redshift, dominated by gravitational redshifting. The change of $\hat{\Delta}$ with radial distance is predicted for SPIDERS galaxies in General Relativity (GR), and $f(R)$ gravity, and compared to the observations. The values of $\hat{\Delta}=-13.5\pm4.7$ km s$^{-1}$, $\hat{\Delta}=-12.5\pm5.1$ km s$^{-1}$, and $\hat{\Delta}=-18.6\pm4.8$ km s$^{-1}$ for the BCG, X-ray and CG cases respectively broadly agree with the literature. There is no significant preference of one gravity theory over another, but all cases give a clear detection ($>2.5\sigma$) of $\hat{\Delta}$. The BCG centroid is deemed to be the most robust method in this analysis, due to no well defined central redshift when using an X-ray centroid, and CGs identified by redMaPPer with no associated spectroscopic redshift. For future gravitational redshift studies, an order of magnitude more galaxies, $\sim\!500\,000$, will be required-a possible feat with the forthcoming Vera C. Rubin Observatory, Euclid and eROSITA., Comment: Accepted for publication in MNRAS. 11 pages, 10 figures