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Date and Time of the Query: 2019-07-19 T12:28:43 PDT
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For refcode 2009ApJ...701.1283P:
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2009ApJ...701.1283P Discrepant Mass Estimates in the Cluster of Galaxies Abell 1689 Peng, E.-H.; Andersson, K.; Bautz, M. W.; Garmire, G. P. Abstract. We present a new mass estimate of a well studied gravitational lensing cluster, Abell 1689, from deep Chandra observations with a total exposure of 200 ks. Within r = 200 h ^-1^ kpc, the X-ray mass estimate is systematically lower than that of lensing by 30%-50%. At r>200 h ^-1^ kpc, the mass density profiles from X-ray and weak lensing methods give consistent results. The most recent weak lensing work suggests a steeper profile than what is found from the X-ray analysis, while still in agreement with the mass at large radii. Fitting the total mass profile to a Navarro-Frenk-White model, we find M_200_ = (1.16^+0.45^_-0.27_) x 10^15^ h ^-1^ M_sun_ with a concentration, c_200_ = 5.3^+1.3^_-1.2_, using nonparametric mass modeling. With parametric profile modeling, we find M_200_ = (0.94^+0.11^_-0.06_) x 10^15^ h ^-1^ M_sun_ and c_200_ = 6.6^+0.4^_-0.4_. This is much lower compared to masses deduced from the combined strong and weak lensing analysis. Previous studies have suggested that cooler small-scale structures can bias X-ray temperature measurements or that the northern part of the cluster is disturbed. We find these scenarios unlikely to resolve the central mass discrepancy since the former requires 70%-90% of the space to be occupied by these cool structures, and excluding the northern substructure does not significantly affect the total mass profiles. A more plausible explanation is a projection effect. Assuming that the gas temperature and density profiles have a prolate symmetry, we can bring the X-ray mass estimate into a closer agreement with that of lensing. We also find that the previously reported high hard-band to broadband temperature ratio in A1689, and many other clusters observed with Chandra, may be resulting from the instrumental absorption that decreases 10%-15% of the effective area at ~1.75 keV. Caution must be taken when analyzing multiple spectral components under this calibration uncertainty. Key words: galaxies: clusters: individual (Abell 1689); X-rays: galaxies: clusters
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