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.
2004/01/01
Wide-Field X-Ray Temperature, Pressure, and Entropy Maps of A754
Henry et al. 2004
copy from http://adsabs.harvard.edu/abs/2004ApJ...615..181H
We present a mosaic of XMM-Newton observations of the nearby major-merger cluster A754 that has either a wider field or better spectral or spatial resolution than previous observations. We construct maps of X-ray surface brightness and temperature integrated along the line of sight. From these two primary maps we derive pseudopressure and pseudoentropy maps. There is structure on a large range of scales in these maps, but the basic pattern is similar to numerical hydrodynamic simulations of cluster mergers. The high surface brightness eastern bar contains gas with the minimum entropy and temperature coupled with the highest iron abundance and density in the cluster. A new feature revealed by these observations is a plumelike structure that appears to emerge from the bar heading northwest. The diffuse radio source also occupies this region, and there is some correspondence between the two. Another new feature is a rim of hot gas to the east, south, and west. We interpret the bar as the core gas from the original main cluster flattened and displaced from the dark matter potential minimum by the merger. The hot rim is the outgoing forward shock from the merger. However, this and previous shocks were weak (M<=2.25), so they are likely only small contributors to the radio-emitting particles. These observations lend support to the merger hypothesis in A754, but some of the parameters of existing models need modification.
Based on observations with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA).
copy from http://adsabs.harvard.edu/abs/2004ApJ...615..181H
We present a mosaic of XMM-Newton observations of the nearby major-merger cluster A754 that has either a wider field or better spectral or spatial resolution than previous observations. We construct maps of X-ray surface brightness and temperature integrated along the line of sight. From these two primary maps we derive pseudopressure and pseudoentropy maps. There is structure on a large range of scales in these maps, but the basic pattern is similar to numerical hydrodynamic simulations of cluster mergers. The high surface brightness eastern bar contains gas with the minimum entropy and temperature coupled with the highest iron abundance and density in the cluster. A new feature revealed by these observations is a plumelike structure that appears to emerge from the bar heading northwest. The diffuse radio source also occupies this region, and there is some correspondence between the two. Another new feature is a rim of hot gas to the east, south, and west. We interpret the bar as the core gas from the original main cluster flattened and displaced from the dark matter potential minimum by the merger. The hot rim is the outgoing forward shock from the merger. However, this and previous shocks were weak (M<=2.25), so they are likely only small contributors to the radio-emitting particles. These observations lend support to the merger hypothesis in A754, but some of the parameters of existing models need modification.
Based on observations with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA).
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