Hyperluminous starburst gives up its secrets

Ivison, RJ; Page, MJ; Cirasuolo, M; Harrison, CM; Mainieri, V; Arumugam, V; Dudzevičiūtė, U

Abstract

HATLAS J084933.4+021443 was identified as a dusty starburst via its rest-frame far-infrared (far-IR) emission. Multi-frequency imaging and spectroscopy revealed a cluster of four dusty galaxies at z = 2.41, covering 80 kpc. Here, we use ALMA to confirm a more distant, fifth protocluster member, and present X-ray and rest-frame optical imaging spectroscopy of the brightest, an unlensed hyperluminous IR galaxy (HyLIRG). The data reveal broad Hα and bright [N II] lines, and bright X-ray emission, characteristics that betray a Type-1 active galactic nucleus (AGN), strengthening evidence that AGN are ubiquitous amongst HyLIRGs. The accreting black hole is super massive, Mbh ≈ 2 × 109 M⊙, with little intrinsic absorption, NH ≈ 5 × 1021 cm−2. The X-ray properties suggest the accretion luminosity rivals that of the starburst, yet it is not obvious where this emerges in its panchromatic spectral energy distribution (SED). We outline three scenarios that could give rise to the observed characteristics, and how we might distinguish between them. In the first, we see the AGN through the host galaxy because of the cavity it excavates. In the others, the AGN is not co-spatial with the starburst, having been ejected via asymmetric gravitational radiation, or having evolved towards the naked quasar phase in an unseen companion.

Citation

Ivison, R., Page, M., Cirasuolo, M., Harrison, C., Mainieri, V., Arumugam, V., & Dudzevičiūtė, U. (2019). Hyperluminous starburst gives up its secrets. Monthly Notices of the Royal Astronomical Society, 489(1), 427-436. https://doi.org/10.1093/mnras/stz2180

• Journal Article Type: Article
• Acceptance Date: Jul 26, 2019
• Online Publication Date: Aug 8, 2019
• Publication Date: Oct 31, 2019
• Deposit Date: Aug 13, 2019
• Publicly Available Date: Aug 13, 2019
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 489
• Issue: 1
• Pages: 427-436
• DOI: https://doi.org/10.1093/mnras/stz2180
• Public URL: https://durham-repository.worktribe.com/output/1290496