ABeppoSAXObservation of the IC 1262 Galaxy Cluster
Author(s) -
Daniel Hudson,
M. J. Henriksen,
S. Colafrancesco
Publication year - 2003
Publication title -
the astrophysical journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.376
H-Index - 489
eISSN - 1538-4357
pISSN - 0004-637X
DOI - 10.1086/345492
Subject(s) - physics , astrophysics , rosat , spectral index , flux (metallurgy) , sky , galaxy , photon , cluster (spacecraft) , spectral line , astronomy , optics , materials science , computer science , metallurgy , programming language
We present an analysis of BeppoSAX observations of the IC1262 galaxy clusterand report the first temperature and abundance measurements, along withpreliminary indications of diffuse, nonthermal emission. By fitting a 6' (~360h_50^-1 kpc) region with a single Mewe-Kaastra-Liedahl model with photoelectricabsorption, we find a temperature of 2.1 - 2.3 keV, and abundance of 0.45 -0.77 (both 90% confidence). We find the addition of a power-law componentprovides a statistically significant improvement (F-test = 90%) to the fit. Theaddition of a second thermal component also improves the fit but we argue thatit is physically implausible. The power-law component has a photon index(Gamma_X) of 0.4 - 2.8 and a nonthermal flux of (4.1 - 56.7) x 10-5 photonscm^-2 s^-1 over the 1.5 - 10.5 keV range in the Medium Energy Concentratorspectrometer detector. An unidentified X-ray source found in the ROSAT HighResolution Imager observation (~0'.9 from the center of the cluster) is apossible explanation for the nonthermal flux; however, additional evidence ofdiffuse, nonthermal emission comes from the NRAO VLA Sky Survey and theWesterbork Northern Sky Survey radio measurements, in which excess diffuse,radio flux is observed after point-source subtraction. The radio excess can befitted to a simple power law with a spectral index of ~1.8, which is consistentwith the nonthermal X-ray emission spectral index. The steep spectrum istypical of diffuse emission and the size of the radio source implies that it islarger than the cD galaxy and not due to a discreet source
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