X-Ray Evidence for Multiphase Hot Gas with Nearly Solar Fe Abundances in the Brightest Groups of Galaxies

We investigate the history of galactic feedback and chemical enrichment within a sample of 15 X-ray bright groups of galaxies, on the basis of the inferred Fe and Si distributions in the hot gas and the associated metal masses produced by core-collapse and type Ia supernovae (SN). Most of these cool-core groups show a central Fe and Si excess, which can be explained by prolonged enrichment by SN Ia and stellar winds in the central early-type galaxy alone, but with tentative e...

I review the results of recent analysis and interpretation of X-ray observations of elliptical galaxies, focusing on elemental abundances and dark matter. The hot ISM is characterized by subsolar Fe abundances and solar Si-to-Fe ratios; and, I compare these with stellar abundances and discuss implications of these measurements. From models constructed to explain X-ray temperatures and their correlation with optical properties in a complete sample of ellipticals, I demonstrate...

We perform a spatially resolved X-ray spectroscopic study of a set of 18 relaxed clusters of galaxies with gas temperatures below 4 keV. Spectral analysis was done using ASCA/SIS data coupled with the spatial information contained in ROSAT/PSPC and Einstein/IPC observations. We derive the temperature profiles using single-temperature fits and also correct for the presence of cold gas at the cluster centers. For all of the clusters in the sample, we derive Si and Fe abundance ...

Utilizing ASCA archival data of about 300 objects of elliptical galaxies, groups, and clusters of galaxies, we performed systematic measurements of the X-ray properties of hot gas in their systems, and compiled them in this paper. The steepness of the luminosity--temperature (LT) relation, $L_{\rm X}\propto(kT)^{\alpha}$, in the range of $kT=$1.5--15 keV is $\alpha=3.17\pm0.15$, consistent with previous measurements. In the relation, we find two breaks at around ICM temperatu...

The recent {\em ASCA} results show that the iron abundance of the X-ray gas of elliptical galaxies is less than the solar abundance ($Z_{\sun}$). The observed low iron abundance is inconsistent with the predictions of the previous chemical evolution models. In order to solve this problem, we present a simple model of chemical evolution for elliptical galaxies after the galactic wind period under the assumption that the gases ejected from stars do not mix with the circumferent...

We discuss the X-ray properties of the cooling flows in a sample of thirty highly X-ray luminous clusters of galaxies observed with the ASCA and ROSAT satellites. We demonstrate the need for multiphase models to consistently explain the spectral and imaging X-ray data for the clusters. The mass deposition rates of the cooling flows, independently determined from the ASCA spectra and ROSAT images, exhibit good agreement and exceed 1000 solar masses per year in the largest syst...

We have analyzed ASCA data of 27 early-type galaxies, and studied the properties of their X-ray emitting ISM (Inter Stellar Medium) in detail. We found that overlapping lines and free-bound continuum cause strong coupling in the derived abundances of various elements. The abundance determination is also difficult due to the uncertainties in the Fe-L atomic physics, because Fe-L lines couple with O and Ne K-lines. However, when abundances of $\alpha$-elements are fixed, all ...

We present estimates for the iron content of the stellar and diffused components of elliptical galaxies, as derived respectively from integrated optical spectra and from ASCA X-ray observations. A macroscopic discrepancy emerges between the expected iron abundances in the hot interstellar medium (ISM) and what is indicated by the X-ray observations, especially when allowance is made for the current iron enrichment by Type Ia supernovae. This strong discrepancy, that in some e...

We present the first in a series of papers studying the X-ray properties of 28 early type galaxies spanning ~3 orders of magnitude in L_x. We report emission-weighted constraints for Fe, O, Ne, Mg, Si, S and Ni. We find no evidence of the very sub-solar Z_Fe historically reported, confirming a trend in recent X-ray observations of bright galaxies and groups, nor do we find Z_Fe correlates with L_x. In general we find no evidence for multi-phase ISM, indicating multi-temperatu...

Galaxy groups are the least massive systems where the bulk of baryons begin to be accounted for. Not simply the scaled-down versions of rich clusters following self-similar relations, galaxy groups are ideal systems to study baryon physics, which is important for both cluster cosmology and galaxy formation. We review the recent observational results on the hot gas in galaxy groups. The first part of the paper is on the scaling relations, including X-ray luminosity, entropy, g...