[Paper Review] BeppoSAX observations of two high redshift clusters of galaxies: RXJ0152.7-1357 and MS2053.7-0449

R. Della Ceca, R. Scaramella+4 more|arXiv (Cornell University)|Oct 27, 1999

Galaxies: Formation, Evolution, Phenomena3 citations

TL;DR

This paper presents BeppoSAX X-ray observations of two high-redshift galaxy clusters, RXJ0152.7-1357 (z=0.83) and MS2053.7-0449 (z=0.58), measuring gas temperature and metallicity to probe the evolution of the X-ray luminosity–temperature (L(bol)–T) relation. The data support a non-evolving or mildly evolving L(bol)–T relation, favoring low-Omega cosmological models.

ABSTRACT

We present X-ray observations of two high redshift clusters of galaxies carried out with the BeppoSAX satellite. One cluster, RXJ0152.7-1357 at z = 0.83, was selected from the ROSAT Deep Cluster Survey sample, as one of the most X-ray luminous systems known at z>0.5. The optical and ROSAT-PSPC data show a complex morphology with at least two cores. Our SAX observations yield a gas temperature kT = 6.46^{+1.74}_{-1.19} keV and a metallicity A = 0.53^{+0.29}_{-0.24}, with a prominent iron K(alpha) line. The second cluster, MS2053.7-0449 at z = 0.58, was selected from the EMSS sample. Given the poor statistics no constraints on the metallicity can be derived from the present data. Large uncertainties are associated to the gas temperature (kT = 6.7^{+6.8}_{-2.3} keV), which has been obtained after fixing the abundance to 0.3 solar. Combining these results with those obtained for similarly high redshift (z >= 0.5) clusters of galaxies with broad band X-ray spectra, we discuss the high redshift L(bol) - T relationship. The data can easily be accommodated with a non-evolving (or mildly evolving) L(bol) - T relation, a result which, when combined with the little observed evolution in the bulk of the X-ray cluster population, gives support to low Omega cosmological models.

Motivation & Objective

• To study the X-ray properties of two high-redshift galaxy clusters, RXJ0152.7-1357 (z=0.83) and MS2053.7-0449 (z=0.58), using BeppoSAX data.
• To measure the hot plasma temperature and metallicity in these clusters to assess the evolution of the X-ray luminosity–temperature (L(bol)–T) relation at high redshift.
• To test cosmological models by comparing observed cluster scaling relations with predictions under different Omega values.
• To investigate whether the high-redshift cluster population shows significant evolution in X-ray properties compared to low-redshift systems.

Proposed method

• X-ray data were collected using the BeppoSAX satellite's Medium Energy Concentrator and Low Energy Concentrator instruments.
• Spectral fitting was applied to the X-ray data using a thermal plasma model with a fixed abundance of 0.3 solar for MS2053.7-0449 due to low signal-to-noise.
• For RXJ0152.7-1357, a free-fit model was used to derive temperature (kT = 6.46^{+1.74}_{-1.19} keV) and metallicity (A = 0.53^{+0.29}_{-0.24}) with an iron K-alpha line detected.
• The L(bol)–T relation was derived from the observed X-ray luminosities and temperatures, combining these results with those from other high-redshift clusters with broad-band spectra.
• Cosmological implications were assessed by comparing the observed scaling relation with predictions for low-Omega and high-Omega models.

Experimental results

Research questions

• RQ1 Does the X-ray luminosity–temperature (L(bol)–T) relation of high-redshift clusters (z ≥ 0.5) show significant evolution compared to low-redshift clusters?
• RQ2 What are the temperature and metallicity of the hot intracluster plasma in RXJ0152.7-1357 and MS2053.7-0449 as measured by BeppoSAX?
• RQ3 How do the observed X-ray properties of these clusters constrain the value of Omega in cosmological models?
• RQ4 Is the observed L(bol)–T relation consistent with a non-evolving or mildly evolving relation at high redshift?

Key findings

• The hot plasma temperature in RXJ0152.7-1357 was measured as kT = 6.46^{+1.74}_{-1.19} keV with a metallicity of A = 0.53^{+0.29}_{-0.24} solar, indicating a moderately metal-rich environment.
• A prominent iron K-alpha emission line was detected in the spectrum of RXJ0152.7-1357, supporting the presence of enhanced iron abundance.
• For MS2053.7-0449, the temperature was constrained to kT = 6.7^{+6.8}_{-2.3} keV with large uncertainties due to poor signal-to-noise, and no reliable metallicity measurement was possible.
• When combined with other high-redshift clusters, the observed L(bol)–T relation shows no significant evolution, consistent with a non-evolving or mildly evolving relation.
• The lack of strong evolution in the L(bol)–T relation supports low-Omega cosmological models over high-Omega alternatives.