Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/230870

Title

Chandra observations of NGC4342, an optically faint, x-ray gas-rich early-type galaxy

Author(s)

Bogdan, Akos;  Forman, William R.;  Kraft, Ralph P.;  Jones, Christine;  Blom, Christina;  Randall, Scott W.;  Zhang, Zhongli;  Zhuravleva, Irina;  Churazov, Eugene;  Li, Zhiyuan;  Nulsen, Paul E. J.;  Vikhlinin, Alexey;  Schindler, Sabine

Abstract

Chandra X-ray observations of NGC4342, a low stellar mass (M_K=-22.79 mag) early-type galaxy, show luminous, diffuse X-ray emission originating from hot gas with temperature of kT~0.6 keV. The observed 0.5-2 keV band luminosity of the diffuse X-ray emission within the D_25 ellipse is L_0.5-2keV = 2.7 x 10^39 erg/s. The hot gas has a significantly broader distribution than the stellar light, and shows strong hydrodynamic disturbances with a sharp surface brightness edge to the northeast and a trailing tail. We identify the edge as a cold front and conclude that the distorted morphology of the hot gas is produced by ram pressure as NGC4342 moves through external gas. From the thermal pressure ratios inside and outside the cold front, we estimate the velocity of NGC4342 and find that it moves supersonically (M~2.6) towards the northeast. Outside the optical extent of the galaxy we detect ~17 bright (L_0.5-8keV > 3 x 10^37 erg/s) excess X-ray point sources. The excess sources are presumably low-mass X-ray binaries (LMXBs) located in metal-poor globular clusters (GCs) in the extended dark matter halo of NGC4342. Based on the number of excess sources and the average frequency of bright LMXBs in GCs, we estimate that NGC4342 may host roughly 850-1700 GCs. In good agreement with this, optical observations hint that NGC4342 may harbor 1200 +/- 500 GCs. This number corresponds to a GC specific frequency of S_N = 19.9 +/- 8.3, which is among the largest values observed in full-size galaxies.

Publication type

Journal article

Research centre

Swinburne University of Technology. Faculty of Information and Communication Technologies. Centre for Astrophysics and Supercomputing

Source

Astrophysical Journal, Vol. 755, no. 1 (Aug 2012), article no. 25

Publication year

2012

FOR Code(s)

0201 Astronomical and Space Sciences;  0305 Organic Chemistry;  0306 Physical Chemistry (Incl. Structural)

Keyword(s)

Galaxies;  Intergalactic medium;  ISM;  NGC 4342;  Stellar content;  X-rays

Publisher

Institute of Physics Publishing

ISSN

0004-637X

Publisher URL

http://dx.doi.org/10.1088/0004-637X/755/1/25

Copyright

Copyright © 2012 The American Astronomical Society. All rights reserved. The American Astronomical Society does not allow Swinburne Research Bank to archive either the accepted manuscript or the published version of the article. However you can find an earlier version of the full text here: http://arxiv.org/abs/1203.1642.

Peer reviewed