We investigate a sample of 152 dusty sources at 1.5 <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 ∗ > 1010 M o and SFR (∼100-1000 M o 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 (f gas = M gas/(M gas + M ∗) ≃20%-70%), and the gas fractions of the two SB classes are very similar (f gas = 43% ± 4% and f gas = 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 f gas. Indeed, SBs at z =2, with relatively low bolometric AGN luminosities in the range 1044
Active Galactic Nuclei in Dusty Starbursts at z = 2: Feedback Still to Kick in / Rodighiero G.; Enia A.; Delvecchio I.; Lapi A.; Magdis G.E.; Rujopakarn W.; Mancini C.; Rodriguez-Munoz 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.. - In: THE ASTROPHYSICAL JOURNAL LETTERS. - ISSN 2041-8205. - ELETTRONICO. - 877:2(2019), pp. L38.38-L38.44. [10.3847/2041-8213/ab222e]
Active Galactic Nuclei in Dusty Starbursts at z = 2: Feedback Still to Kick in
Enia A.;Delvecchio I.;Renzini A.;Gruppioni C.;Perna M.;
2019
Abstract
We investigate a sample of 152 dusty sources at 1.5 <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 ∗ > 1010 M o and SFR (∼100-1000 M o 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 (f gas = M gas/(M gas + M ∗) ≃20%-70%), and the gas fractions of the two SB classes are very similar (f gas = 43% ± 4% and f gas = 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 f gas. Indeed, SBs at z =2, with relatively low bolometric AGN luminosities in the range 1044I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
