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3.10. X-ray constraints on accretion and starburst processes in galactic nuclei

Published online by Cambridge University Press:  25 May 2016

A. Ptak
Affiliation:
Code 662, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA
P. Serlemitsos
Affiliation:
Code 662, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA
T. Yaqoob
Affiliation:
Code 662, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA
R. Mushotzky
Affiliation:
Code 662, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA
Y. Terashima
Affiliation:
Department of Physics, Nagoya University, Chikusa-ku, Nagoya, Japan
H. Kunieda
Affiliation:
Department of Physics, Nagoya University, Chikusa-ku, Nagoya, Japan

Abstract

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Although the galaxies in our sample are heterogenous in their optical classifications (LLAGN: M51, NGC 3147, NGC 4258; LINER: NGC 3079, NGC 3310, NGC 3998, NGC 4579, NGC 4594; starburst: M82, NGC 253, NGC 3628, NGC 6946), they are fit well by a “canonical” spectrum with a hot, optically-thin thermal component with T ~ 8 × 106 K and an absorbed (NH ~ 1022 cm−2) power-law with an energy index α ~ 0.7–0.8. Both the “soft” component, most likely due to SN or superwind-heated ISM, and the “hard” power-law, most likely due to a micro-AGN and/or blackhole candidates, appear to be common in low-activity galaxies. If the soft component is associated with a superwind outflow, than ~ 10% of the X-ray emission is due to “swept-up” ISM rather than superwind emission. The abundance of Fe relative to α-process elements tends to be sub-solar, possibly due to dust-depletion and/or type-II SN enrichment. The lack of short-term variability in the hard component suggests that if it is due to an AGN, then the mode of accretion is probably fundamentally different from “normal” Seyfert galaxies.

Type
Part I. Stellar Cluster, Star Formation
Copyright
Copyright © Kluwer 1998