3.10. X-ray constraints on accretion and starburst processes in galactic nuclei
Symposium - International astronomical union
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 withT~ 8 × 106K and an absorbed (NH~ 1022cm−2) power-law with an energy indexα~ 0.7–0.8. Both the "soft" component, most likely due to SN or superwind-heated ISM, and the "hard" power-law,
... e "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 toα-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.