A Highly Accreting Low-Mass Black Hole Hidden in the Dust

Studying the circumnuclear environment, which is the key element in the unification model of AGN, is the first step in probing obscured accretion and understanding the formation and growth history of SMBHs. An interesting discovery by large X-ray surveys is that radiative feedback on dusty gas is regulating the circumnuclear environment where the effective Eddington ratio for cool dusty gas is lower than that for ionised dust-free gas.

I will present a peculiar NLS1 AGN, Mrk 1239. Unlike typical type-1 AGN, its soft X-ray emission is so obscured that the X-ray emission from the star-forming region dominates. Meanwhile, Mrk 1239 also remains a high accretion rate as most other NLS1s. Therefore, radiation-driven dusty winds might be forming near the edge of its torus along our line of sight while the overall torus remains stable thanks to its high average column density. In the NIR band, Mrk 1239 shows strong blackbody emission of 1200 K peaking at 2.2 micrometres. Such a high temperature is rare as it is close to the sublimation limit. This strong thermal emission is believed to be from the dust on the inner side of the torus heated by the radiation from the central engine.

In the end, I will discuss how the study of Mrk 1239 provides a pilot study for future large surveys of obscured AGN at higher redshifts e.g., from Athena, JWST and 8m class ground-based telescopes.