A New Cluster of Galaxies Towards the Galactic Bulge, Suzaku J1759-3450

Abstract

We observed an extended X-ray source, designated as Suzaku J1759-3450, with Suzaku and Chandra observations towards 1RXS J175911.0-344921, which is an unidentified X-ray source listed in the ROSAT Bright Source Catalogue. A conspicuous emission line at 6 keV was also found in the Suzaku J1759-3450 spectrum. Assuming the emission line to be K emission from He-like Fe ions, we inferred Suzaku J1759-3450 to be an extragalactic object located at z = 0.13. The radial profile of the surface brightness in the 0.5-10 keV band was explained well with an isothermal β-model of $r_\textrm c=1{.^\prime}61$ and $\beta=0.78$. The X-ray spectrum was well reproduced by an opticallythin thermal plasma with the electron temperature of $kT_e = 5.3$ keV, attenuated by the photoelectric absorption of $N_\textrm H = 2.3 \times 10^{21} \textrm c\textrm m^{-2}$. The bolometric X-ray luminosity of $L_\textrm X(r < r_{500}) = 4.3 \times 10^{44} \textrm {erg} \textrm s^{-1}$ is consistent with that expected from the L _X-T relation of clusters of galaxies. In terms of the spatial extent, the X-ray spectrum, and the bolometric luminosity of the X-ray emitting gas, we concluded that Suzaku J1759-3450 is a new cluster of galaxies.