PASJ 2007
ADS
High-sensitivity wide-band X-ray spectroscopy is the key feature of the Suzaku X-ray observatory, launched on 2005 July 10. This paper summarizes the spacecraft, in-orbit performance, operations, and data processing that are related to observations. The scientific instruments, the high-throughput X-ray telescopes, X-ray CCD cameras, non-imaging hard X-ray detector are also described.
2007/03/01
すざく衛星によるペルセウス銀河団の高温ガスバルク運動の測定(1)
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http://www.asj.or.jp/nenkai/2007a/html/T10b.html
http://www.asj.or.jp/nenkai/2007a/html/T10b.html
銀河団中の高温ガスのバルクモーション及び乱流の測定は、 銀河団高温ガスの構造や進化をさぐる新たなツールになりえる。 特に、数1000km/sの速度で二つの銀河団が合体するマージング の過程で、それぞれの銀河団に付随する高温ガスがいかに混合され リラックスした系に移行していくか、バルクモーションの測定による ダイナミックな描像が期待される。 また、バルクモーションや乱流の測定は、通常、静水圧平衡を仮定する 銀河団の質量測定の精度を検証する上でも重要である。
ペルセウス座銀河団は全天でもっとも高いＸ線表面輝度をもち 鉄輝線のドップラーシフトを通してバルクモーションをさぐるのに 最適な天体である。 すざくXISでは、SWG期間内にエネルギースケールの較正を主目的 として、2006年2月、8月の２回の観測が行われている。２回目の観測では、 放射線損傷を補償するSCIという新たなCCD駆動方法もテストした。
鉄輝線のドップラーシフトを測定するのに最も重要なのが検出器（XIS）の エネルギースケールの精度である。XISのエネルギースケールの精度は0.2\%、速度に 換算して600km/sと評価されている。今回のデータ解析では、電荷転送方向 が 天空座標で互いに異なる4台のXISのデータを同時に利用して、エネルギースケールの 誤差（CTI補正の誤差）をさらに小さくする工夫を試みた。 続いて、検討すべきはスペクトルモデルの妥当性である。本発表では、以上の解析方 法と 検討結果を中心に紹介する（結果と議論に関しては、金丸他の発表参照のこと）
2007/01/01
Suzaku Observations of the Centaurus Cluster: Absence of Bulk Motions in the Intracluster Medium
Ota et al. 2007
http://adsabs.harvard.edu/abs/2007PASJ...59S.351O
The Centaurus cluster (z=0.0104) was observed with the X-ray Imaging Spectrometer (XIS) onboard the Suzaku X-ray satellite in three pointings, one centered on the cluster core and the other two offset by ±8' in declination. To search for possible bulk motions of the intracluster medium, the central energy of a He-like Fe K line (at a rest-frame energy of 6.7keV) was examined to look for a positional dependence. Over spatial scales of 50kpc to 140kpc around the cluster core, the central line energy was found to be constant within a calibration error of 15eV. The 90% upper limit on the line-of-sight velocity difference is |Δv| < 1400 km s-1, giving a tighter constraint than previous measurements. The significant velocity gradients inferred from a previous Chandra study were not detected between two pairs of rectangular regions near the cluster core. These results suggest that the bulk velocity does not largely exceed the thermal velocity of the gas in the central region of the Centaurus cluster. The mean redshift of the intracluster medium was determined to be 0.0097, in agreement with the optical redshift of the cluster within the calibration uncertainty. Implications of the present results for estimating the cluster mass are briefly discussed.
http://adsabs.harvard.edu/abs/2007PASJ...59S.351O
The Centaurus cluster (z=0.0104) was observed with the X-ray Imaging Spectrometer (XIS) onboard the Suzaku X-ray satellite in three pointings, one centered on the cluster core and the other two offset by ±8' in declination. To search for possible bulk motions of the intracluster medium, the central energy of a He-like Fe K line (at a rest-frame energy of 6.7keV) was examined to look for a positional dependence. Over spatial scales of 50kpc to 140kpc around the cluster core, the central line energy was found to be constant within a calibration error of 15eV. The 90% upper limit on the line-of-sight velocity difference is |Δv| < 1400 km s-1, giving a tighter constraint than previous measurements. The significant velocity gradients inferred from a previous Chandra study were not detected between two pairs of rectangular regions near the cluster core. These results suggest that the bulk velocity does not largely exceed the thermal velocity of the gas in the central region of the Centaurus cluster. The mean redshift of the intracluster medium was determined to be 0.0097, in agreement with the optical redshift of the cluster within the calibration uncertainty. Implications of the present results for estimating the cluster mass are briefly discussed.
2006/11/22
A very deep Chandra observation of the Perseus cluster: shocks, ripples and conduction
MNRAS, 2006
We present the first results from a very deep Chandra X-ray observation of the core of the Perseus cluster of galaxies. A pressure map reveals a clear thick band of high pressure around the inner radio bubbles. The gas in the band must be expanding outwards and the sharp front to it is identified as a shock front, yet we see no temperature jump across it; indeed, there is more soft emission behind the shock than in front of it. We conclude that in this inner region either thermal conduction operates efficiently or the co-existing relativistic plasma seen as the radio mini-halo is mediating the shock. If common, isothermal shocks in cluster cores mean that we cannot diagnose the expansion speed of radio bubbles from temperature measurements alone. They can at times expand more rapidly than currently assumed without producing significant regions of hot gas. Bubbles may also be significantly more energetic. The pressure ripples found in earlier images are identified as isothermal sound waves. A simple estimate based on their amplitude confirms that they can be an effective distributed heat source able to balance radiative cooling. We see multiphase gas with about 109Msolar at a temperature of about 0.5 keV. Much, but not all, of this X-ray emitting cooler gas is spatially associated with the optical filamentary nebula around the central galaxy, NGC1275. A residual cooling flow of about 50Msolaryr-1 may be taking place. A channel is found in the pressure map along the path of the bubbles, with indications found of outer bubbles. The channel connects in the south (S) with a curious cold front.
We present the first results from a very deep Chandra X-ray observation of the core of the Perseus cluster of galaxies. A pressure map reveals a clear thick band of high pressure around the inner radio bubbles. The gas in the band must be expanding outwards and the sharp front to it is identified as a shock front, yet we see no temperature jump across it; indeed, there is more soft emission behind the shock than in front of it. We conclude that in this inner region either thermal conduction operates efficiently or the co-existing relativistic plasma seen as the radio mini-halo is mediating the shock. If common, isothermal shocks in cluster cores mean that we cannot diagnose the expansion speed of radio bubbles from temperature measurements alone. They can at times expand more rapidly than currently assumed without producing significant regions of hot gas. Bubbles may also be significantly more energetic. The pressure ripples found in earlier images are identified as isothermal sound waves. A simple estimate based on their amplitude confirms that they can be an effective distributed heat source able to balance radiative cooling. We see multiphase gas with about 109Msolar at a temperature of about 0.5 keV. Much, but not all, of this X-ray emitting cooler gas is spatially associated with the optical filamentary nebula around the central galaxy, NGC1275. A residual cooling flow of about 50Msolaryr-1 may be taking place. A channel is found in the pressure map along the path of the bubbles, with indications found of outer bubbles. The channel connects in the south (S) with a curious cold front.
2005/09/01
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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