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X-Ray Emission as Evidence of Activity in Otherwise “Normal” Galaxies

Published online by Cambridge University Press:  04 August 2017

T. Maccacaro
Affiliation:
Harvard-Smithsonian Center for Astrophysics, Cambridge, Ma.
I.M. Gioia
Affiliation:
Harvard-Smithsonian Center for Astrophysics, Cambridge, Ma.
R. Schild
Affiliation:
Harvard-Smithsonian Center for Astrophysics, Cambridge, Ma.
D. Maccagni
Affiliation:
CNR, Istituto di Fisica Cosmica, Milano, Italy
J. Stocke
Affiliation:
Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, Co.

Abstract

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The very large majority of the galaxies selected in X-ray surveys are active galaxies (e.g. narrow emission line galaxies, Seyfert galaxies etc.). There are however a few examples of normal galaxies, which are sometimes characterized by an X-ray luminosity in excess of what is expected on the basis of their optical appearance. A closer look at these galaxies may reveal the presence of a mini active nucleus or of other processes responsible for the powerful X-ray emission. Here we consider the normal galaxies selected in the Medium Sensitivity Survey and we discuss the properties of the most X-ray luminous one. We show that this object, which has an optical spectrum lacking any evidence of nuclear activity and which has a radio luminosity typical of early type galaxies, is indeed a peculiar galaxy surrounded by a hot (>2 keV) halo extending out to a radius of 300 kpc, implying a total mass of ∼3 × 1013 M.

Type
VII. Low Level Activity and Intermediate Objects
Copyright
Copyright © Reidel 1987 

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