国立天文台研究会
東京大学(化学本館 ５階講堂)
2004年12月25日(土)〜27日(月)
folder name
NextAstronomy2004
2004/12/25
ASCA Compilation of X-Ray Properties of Hot Gas in Elliptical Galaxies and Galaxy Clusters: Two Breaks in the Temperature Dependences
Fukazawa, Makishima, Ohashi
http://adsabs.harvard.edu/abs/2004PASJ...56..965F
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, LiX ∝ (kT)α, in the range of kT ˜ 1.5 ‑ 15 keV is α = 3.17 ± 0.15, consistent with previous measurements. In the relation, we find two breaks at around ICM temperatures of 1 keV and 4 keV: α = 2.34 ± 0.29 above 4 keV, 3.74 ± 0.32 in 1.5-5 keV, and 4.03 ± 1.07 below 1.5keV. Such two breaks are also evident in the temperature and size relation. The steepness in the LT relation at kT > 4 keV is consistent with the scale-relation derived from the CDM model, indicating that the gravitational effect is dominant in richer clusters, while poorer clusters suffer non-gravity effects. The steep LT relation below 1keV is almost attributed to X-ray faint systems of elliptical galaxies and galaxy groups. We found that the ICM mass within the scaling radius R1500 follows the relation of Mgas ∝ T2.33±0.07 from X-ray faint galaxies to rich clusters. Therefore, we speculate that even such X-ray faint systems contain a large-scale hot gas, which is too faint to detect.
http://adsabs.harvard.edu/abs/2004PASJ...56..965F
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, LiX ∝ (kT)α, in the range of kT ˜ 1.5 ‑ 15 keV is α = 3.17 ± 0.15, consistent with previous measurements. In the relation, we find two breaks at around ICM temperatures of 1 keV and 4 keV: α = 2.34 ± 0.29 above 4 keV, 3.74 ± 0.32 in 1.5-5 keV, and 4.03 ± 1.07 below 1.5keV. Such two breaks are also evident in the temperature and size relation. The steepness in the LT relation at kT > 4 keV is consistent with the scale-relation derived from the CDM model, indicating that the gravitational effect is dominant in richer clusters, while poorer clusters suffer non-gravity effects. The steep LT relation below 1keV is almost attributed to X-ray faint systems of elliptical galaxies and galaxy groups. We found that the ICM mass within the scaling radius R1500 follows the relation of Mgas ∝ T2.33±0.07 from X-ray faint galaxies to rich clusters. Therefore, we speculate that even such X-ray faint systems contain a large-scale hot gas, which is too faint to detect.
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