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Register a new userModerate Temperature Clusters of Galaxies from the RDCS and the High Redshift Luminosity-Temperature Relation
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B. P. Holden
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We present our discovery observations and analysis of RDCS1317+2911, z = 0.805, and RDCS1350+6007, z= 0.804, two clusters of galaxies identified through X-ray emission in the ROSAT Deep Cluster Survey (RDCS). We find a temperature of 3.7 +1.5 -0.9 keV and a bolometric luminosity of 8.2e43 +1.7e43 -1.6e43 erg/s for RDCS1317+2911, and a temperature of 4.9 +1.3 -0.9 keV and a bolometric luminosity of 4.1e44 +0.5e44 -0.4e44 erg/s for RDCS1350+6007. Our weak lensing analysis of RDCS1350+6007 confirms the general shape of the inner density profile but predicts twice the mass of the model based on the X-ray profile. We combine the X-ray luminosities and temperatures for RDCS clusters of galaxies with such measurements of other clusters at high redshift (z>0.7) and fit the luminosity-temperature relation. We find no statistically significant evolution in the slope or zero-point of this relation at a median of z=0.83. This result is in agreement with models of intracluster medium evolution with significant pre-heating or high initial entropy values. We discuss how low temperature, high redshift clusters of galaxies will allow us to improve on this result and announce the discovery of two such objects, CXOU J0910.1+5419 and CXOU J1316.9+2914.
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We have obtained the first large sample of accurate temperatures for clusters at z>0.14 from ASCA. We compare the luminosity temperature (L-T) distribution for these clusters with the low redshift sample of David et al (1993) and find that there is no evidence for evolution. We also find that the intrinsic variance in this relation is roughly constant with redshift. Additionally, there is no detectable change in the relationship of optical velocity dispersion to X-ray temperature with redshift. Most cosmological simulations driven primarily by gravity predict substantial changes in the L-T relation due to the recent rapid growth of clusters. Our results are consistent either with models in which the cluster core entropy is dominated by pre-heating, or with low Omega models in which cluster structure does not evolve strongly with time. The intrinsic variance in the L-T relation at a fixed redshift can be due a variety of possibilites e.g. a change in the baryonic fraction from cluster to cluster, variation in the fraction of the total energy in the system arising from shocks or supernova heating or variations in the emission measure distributions in multiphase gas.
A luminosity-temperature relation for clusters of galaxies is derived. The two models used, take into account the angular momentum acquisition by the proto-structures during their expansion and collapse. The first one is a modification of the self-similar model (SSM) while the second one is a modification of the Punctuated Equilibria Model (Cavaliere et al. 1999). In both models the mass-temperature relation (M-T) used is based on the calculations of Del Popolo (2002b). We show that the above models lead, in X-rays, to a luminosity-temperature relation that scales as L propto T^5, at scale of groups, flattening to L propto T^3 for rich clusters and converging to L propto T^2 at higher temperatures. However a fundamental result of our paper is that the non-similarity in the L-T relation, can be explained by a simple model that takes into account the amount of the angular momentum of a proto-structure. This result is in disagreement with the widely accepted idea that the above non-similarity is due to non-gravitating processes as those of heating/cooling.
The color-magnitude relation has been determined for the RDCS J0910+5422 cluster of galaxies at redshift z = 1.106. Cluster members were selected from HST ACS images, combined with ground--based near--IR imaging and optical spectroscopy. The observed early--type color--magnitude relation (CMR) in (i_775 -z_850) versus z_850 shows intrinsic scatters in color of 0.042 +/- 0.010 mag and 0.044 +/- 0.020 mag for ellipticals and S0s, respectively. From the scatter about the CMR, a mean luminosity--weighted age t > 3.3 Gyr (z > 3) is derived for the elliptical galaxies. Strikingly, the S0 galaxies in RDCS J0910+5422 are systematically bluer in (i_775 - z_850) by 0.07 +/- 0.02 mag, with respect to the ellipticals. The ellipticity distribution as a function of color indicates that the face-on S0s in this particular cluster have likely been classified as elliptical. Thus, if anything, the offset in color between the elliptical and S0 populations may be even more significant. The color offset between S0 and E corresponds to an age difference of ~1 Gyr, for a single-burst solar metallicity model. A solar metallicity model with an exponential decay in star formation will reproduce the offset for an age of 3.5 Gyr, i.e. the S0s have evolved gradually from star forming progenitors. The early--type population in this cluster appears to be still forming. The blue early-type disk galaxies in RDCS J0910+5422 likely represent the direct progenitors of the more evolved S0s that follow the same red sequence as ellipticals in other clusters. Thirteen red galaxy pairs are observed and the galaxies associated in pairs constitute ~40% of the CMR galaxies in this cluster.
We post-process galaxies in the IllustrisTNG simulations with SKIRT radiative transfer calculations to make predictions for the rest-frame near-infrared (NIR) and far-infrared (FIR) properties of galaxies at $zgeq 4$. The rest-frame $K$- and $z$-band galaxy luminosity functions from TNG are overall consistent with observations, despite a $sim 0.4,mathrm{dex}$ underprediction at $z=4$ for $M_{rm z}lesssim -24$. Predictions for the JWST MIRI observed galaxy luminosity functions and number counts are given. We show that the next-generation survey conducted by JWST can detect 500 (30) galaxies in F1000W in a survey area of $500,{rm arcmin}^{2}$ at $z=6$ ($z=8$). As opposed to the consistency in the UV, optical and NIR, we find that TNG, combined with our dust modelling choices, significantly underpredicts the abundance of most dust-obscured and thus most luminous FIR galaxies. As a result, the obscured cosmic star formation rate density (SFRD) and the SFRD contributed by optical/NIR dark objects are underpredicted. The discrepancies discovered here could provide new constraints on the sub-grid feedback models, or the dust contents, of simulations. Meanwhile, although the TNG predicted dust temperature and its relations with IR luminosity and redshift are qualitatively consistent with observations, the peak dust temperature of $zgeq 6$ galaxies are overestimated by about $20,{rm K}$. This could be related to the limited mass resolution of our simulations to fully resolve the porosity of the interstellar medium (or specifically its dust content) at these redshifts.
K band luminosity functions (LFs) of three, massive, high redshift clusters of galaxies are presented. The evolution of K*, the characteristic magnitude of the LF, is consistent with purely passive evolution, and a redshift of forma tion z = 1.5-2.
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