Structural evolution of the central galaxies in galaxy clusters

In this study, we aim to characterize evolution of the structural parameters of the brightest cluster galaxies (BCGs) by means of surface brightness analysis. In a redshift range of 0.1 < z < 1.0 we will be able to show how the size of BCGs evolve. Deviation of the surface brightness – profile from ordinary elliptical galaxies can shed light onto possible merging histories. Thus, our aim is to present the evolution of structural parameters of BCGs and their correlation with cluster environments as a function of cluster redshift. The central galaxies of galaxy clusters are known as (BCGs). They are the brightest, with quite homogeneous luminosities, and the most massive galaxies in the universe. These galaxies are elliptical galaxies, with no prominent star formation, and are usually found very close to the center of the clusters of galaxies. Due to being in the center of the host cluster, which could be playing a significant role in the formation of the BCG, interactions with the other galaxies in the cluster, and even cannibalization occur frequently. BCGs have distinct surface brightness profiles than regular elliptical galaxies. The unusual properties of the BCGs make the study of formation and evolution of the BCGs interesting. Modern theories explained many methods of galaxy formation: Galaxies can grow by mergers, or the accretion of intergalactic gas, or in situ star formation in collapsing galaxies. The challenge of our studying the development of galaxies is to compare between different galaxies at different redshifts. Surveys provide us a lot of information in this regard. For instance, with its Deep Field observations, the Hubble Space Telescope (HST) offers images of galaxies at redshift z > 1. Furthermore, numerous neighbouring galaxies are covered by the Sloan Digital Sky Survey (SDSS) and Millenium Galaxy Catalogue surveys. They offer data on spectroscopy and imaging. Moreover, the Canada–France–Hawaii Telescope Legacy Survey (CFHTLS) survey, used in this study, is a major imaging project aimed to explore high redshift universe and huge scale structure. TERAPIX has calculated the photometric redshifts (zp) of the CFHTLS using LePhare. The Le Phare programme applied to calculate photometric redshifts. LePhare is a SED fitting tool that uses χ2 minimization to get the most successful comparison of template spectra. Five various template spectra (E, Sbc, Scd, Irr, and SB) are used in the CFHTLS fields' photometric redshift computation. Covering a redshift range up to z ∼ 1.2, these five templates are expanded into 66 templates. Using spectroscopic redshifts (zs) from a VIMOS VLT Deep Survey (VVDS), the templates have been calibrated. Understanding the structural parameters of (BCGs) offers crucial hints for understanding how they formed and evolved. The surface brightness profile fitting findings of 1685 brightest cluster galaxies (BCGs) obtained from the (CFHTLS) in the redshift range of 0.1 < z < 1.0 are presented. We used a single Sérsic profile to fit r-band images of BCGs. To examine the effect of the environment, based on the richness of the host cluster, our sample is separated into two categories. According to our findings, based on statistics, BCGs in rich clusters are larger than those in poor clusters. For the Kormendy, the log Re − log n, and the size-luminosity relations, we present the best-fit linear regressions. We plan to analyze the surface brightness distribution and examine how the structural parameters evolved of various BCGs in the optical images obtained from the CFHTLS survey. The main tool for analysis will be GALFIT which is a data analysis algorithm that fits a 2-D analytic functions to galaxies and point sources directly on digital images. GALFIT is essentially used to gain more information and hints about the origin of galaxies from the analysis of its hidden fine structures. Studies of galaxies using a 2-D modeling has been applied as it can recover the true parameter values without any degeneration. GALFIT, the fitting algorithm, is capable of modeling celestial object profiles in two-dimensional (2D) formats from their raw images. The main functions used in GALFIT to fit a galaxy are; Sérsic, Exponential disk, Nuker, Modified Ferrer, and Edge-on disk. Basically, one model for a specific galaxy is used, otherwise, additional models to minimize the residuals for a complex galaxy with multi-components can be added. Fitting a model to a galaxy image at the simplest conceptual stage is about defining a merit function. Χ2, which is the precision of GALFIT fits, whose value varies from 1 to 2. In the current study, we explored the structural evolution of BCGs found in clusters observed in the CFHTLS's W1 field. The coordinates and geometry of the W1 field has 9 × 8 certain pointings. The overall effective survey area in W1 is 63.75 deg2 due to overlaps between the pointings. The 80% completeness limit in r-band for extended sources is 24 mag, while the median seeing of r band images for the W1 field is 0.71′′. The W1 galaxy catalogue, which masks the regions surrounding brilliant stars, ghosts, spikes, and other places of lower cosmietic quality, allowed the detection of galaxy clusters and associated BCGs. As a result, there are 2 871 455 (r ≤ 24) galaxies in our object catalogue. Among the data outputs of CFHTLS are images, mask files, object and photometric redshift catalogues, and more. TERAPIX processes, produces, and distributes these products. Since the most recent data release in 2012, all data has been made accessible to the public and may be viewed through the Canadian Astronomy Data Centre (CADC). According to the host cluster richness, we separated the cluster sample into two subsamples, such as poor (λ ≤ 30) and rich (λ > 30), to investigate any possible environmental effects. The variety of effective radii suggests that the environmental influences on the development of the BCG can vary. Galactic merger and cannibalism could be more frequent in richer clusters since BCGs existing in the middle of the potential well of galaxy clusters. Additionally, in the literature, it has been demonstrated that the host cluster characteristics and the BCG structural parameters for a BCG sample at z∼0 are correlated. However, the Sérsic index distributions for the poor and rich clusters are almost equal, as predicted by the K-S test. In order to investigate for any evolutionary effects, we divided our BCGs into three redshift bins (i.e., 0.1 < z ≤ 0.4, 0.4 < z ≤ 0.7 and, 0.7 < z ≤ 1.0). The offsets in the Kormendy relation at various redshift bins are mostly caused by cosmic dimming. The slopes of the various relations seem to be consistent with one another.