HICOSMO – cosmology with a complete sample of galaxy clusters – I. Data analysis, sample selection and luminosity–mass scaling relation

Abstract

The X-ray regime, where the most massive visible component of galaxy clusters, the intra cluster medium (ICM), is visible, offers directly measured quantities, like the luminosity, and derived quantities, like the total mass, to characterize these objects. The aim of this project is to analyze a complete sample of galaxy clusters in detail and constrain cosmological parameters, like the matter density, Ω m , or the amplitude of initial density fluctuations, σ 8 . The purely X-ray flux-limited sample (HIFLUGCS ) consists of the 64 X-ray brightest galaxy clusters, which are excellent targets to study the systematic effects, that can bias results. We analyzed in total 196 Chandra observations of the 64 HIFLUGCS clusters, with a total exposure time of 7.7 Ms. Here we present our data analysis procedure (including an automated substructure detection and an energy band optimization for surface brightness profile analysis) which gives individually determined, robust total mass estimates. These masses are tested against dynamical and Planck Sunyaev-Zeldovich (SZ) derived masses of the same clusters, where good overall agreement is found with the dynamical masses. The Planck SZ masses seem to show a mass dependent bias to our hydrostatic masses; possible biases in this mass-mass comparison are discussed including the Planck selection function. Furthermore, we show the results for the (0.1 − 2.4) keV-luminosity vs. mass scalingrelation. The overall slope of the sample (1.34) is in agreement with expectations and values from literature. Splitting the sample into galaxy groups and clusters reveals, even after a selection bias correction, that galaxy groups exhibit a significantly steeper slope (1.88) compared to clusters (1.06).

Probing cosmic isotropy with a new X-ray galaxy cluster sample through theLX–Tscaling relation

“…For the Chandra analysis, we followed the standard data reduction tasks using the CIAO software package (version 4.8,CALDB 4.7.6). A more detailed description is given in Schellenberger & Reiprich (2017) (S17). For the XMM-Newton analysis, we followed the exact same procedure as described in detail by R19.…”

X-Ray Scaling Relations for a Representative Sample of Planck-selected Clusters Observed with XMM-Newton

“…The profiles are then deprojected, using the method presented in Vikhlinin (2006). The implementation has been done following Schellenberger & Reiprich (2017), where the parameters of the deprojected temperature profile are determined using a Markov Chain Monte Carlo. The input temperature profiles are projected along the line of sight at every radius that has a measurement and compared to the observed profile, until convergence.…”

“…We solved Eq. 1 for the radii of the spectral extraction regions (temperature measurements) and fited an NFW model up to the outer regions (Navarro et al 1997) for the mass profile with the relation from Bhattacharya et al (2013) between the Dark Matter concentration c 500 and R 500 as a prior, which constrains the posterior distribution of R 500 to reasonable values (see Schellenberger & Reiprich 2017 for more details). The mass of the gas is then calculated by integrating the density profile within R 500 estimated from Eq.…”

“…While several methods (see e.g. Pacaud et al 2006, Vikhlinin et al 2009, Pratt et al 2009, Mantz et al 2010, Schellenberger & Reiprich 2017 have been proposed to account for Malmquist and Eddington biases, little has been done to incorporate and account for the morphology bias which is expected to be important for eROSITA (and for X-ray survey data in general). In fact, most of the clusters detected with eROSITA will have too few photons to derive gas density and temperature profiles (and thus too few to determine mass profiles).…”

Reliable photometric membership (RPM) of galaxies in clusters – I. A machine learning method and its performance in the local universe

“…Galaxy clusters represent the most massive and latest systems to form in the Universe due to their own gravity. Therefore, they provide an important cosmological tool, especially through the investigation of the cluster mass function and its time evolution, which display a strong dependence on several cosmological parameters (Eke et al 1998;Bahcall et al 2003;de Haan et al 2016;Mantz et al 2014;Schellenberger & Reiprich 2017;Planck Collaboration et al 2016).…”