We investigate a sample of 152 dusty sources at 1.5<z<2.5 to understand the connection of enhanced star formation rate (SFR) and black hole accretion rate. The sources are Herschel-selected, having stellar masses M*>1010Me and SFR (∼100–1000Me yr−1) elevated (>4×) above the star-forming “main sequence,” classifying them as starbursts (SBs). Through a multiwavelength fitting approach (including a dusty torus component), we divided the sample into active SBs (dominated by an active galactic nucleus (AGN) emission, SBs-AGN, ∼23% of the sample) and purely star-forming SBs (SBs-SFR). We visually inspected their Hubble Space Telescope/ultraviolet (UV) rest frame maps: SBs-SFR are generally irregular and composite systems; ∼50% of SBs-AGN are instead dominated by regular compact morphologies. We then found archival Atacama Large Millimeter/submillimeter Array continuum counterparts for 33 galaxies (12 SBs-AGN and 21 SBs-SFR). For these sources we computed dust masses, and, with standard assumptions, we also guessed total molecular gas masses. SBs turn into gas-rich systems ( fgas =Mgas/(Mgas+M*);20%–70%), and the gas fractions of the two SB classes are very similar ( fgas = 43% ± 4% and fgas = 42% ± 2%). Our results show that SBs are consistent with a mixture of: (1) highly star-forming merging systems (dominating the SBs-SFR) and (2) primordial galaxies, rapidly growing their M* together with their black hole (mainly the more compact SBs-AGN). Feedback effects have not yet reduced their fgas. Indeed, SBs at z=2, with relatively low bolometric AGN luminosities in the range 1044<Lbol(AGN)<1046 erg s−1 (compared to bright optical and X-ray quasars), are still relatively far from the epoch when the AGN feedback will quench the SFR in the host and will substantially depress the gas fractions.
|Titolo:||Active Galactic Nuclei in Dusty Starbursts at z = 2: Feedback Still to Kick in|
|Autori:||Rodighiero, G.; Enia, A.; Delvecchio, I.; Lapi, A.; Magdis, G. E.; Rujopakarn, W.; Mancini, C.; Rodríguez-Muñoz, L.; Carraro, R.; Iani, E.; Negrello, M.; Franceschini, A.; Renzini, A.; Gruppioni, C.; Perna, M.; Baronchelli, I.; Puglisi, A.; Cassata, P.; Daddi, E.; Morselli, L.; Silverman, J.|
|Data di pubblicazione:||2019|
|Numero di Articolo:||L38|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.3847/2041-8213/ab222e|
|Appare nelle tipologie:||1.1 Journal article|