ALMA confirmation of an obscured hyperluminous radio-loud AGN at z = 6.853 associated with a dusty starburst in the 1.5 deg2 COSMOS field

Abstract

We present band 6 ALMA observations of a heavily obscured radio-loud (L1.4 GHz = 1025.4 W Hz−1) active galactic nucleus (AGN) candidate at zphot = 6.83 ± 0.06 found in the 1.5 deg2 COSMOS field. The ALMA data reveal detections of exceptionally strong [C ii]158 $\mu$m (z[C ii] = 6.8532) and underlying dust continuum emission from this object (COS-87259), where the [C ii] line luminosity, line width, and 158 $\mu$m continuum luminosity are comparable to those seen from z ∼ 7 sub-mm galaxies and quasar hosts. The 158 $\mu$m continuum detection suggests a total infrared luminosity of $9\times 10^{12}\, \mathrm{ L}_\odot$ with corresponding very large obscured star formation rate (1300 M⊙ yr−1) and dust mass ($2\times 10^9\, \mathrm{ M}_\odot$). The strong break seen between the VIRCam and IRAC photometry perhaps suggests that COS-87259 is an extremely massive reionization-era galaxy with $M_\ast \approx 1.7\times 10^{11}\, \mathrm{ M}_\odot$. Moreover, the MIPS, PACS, and SPIRE detections imply that this object harbours an AGN that is heavily obscured ($\tau _{_{\mathrm{9.7\,\mu m}}}=2.3$) with a bolometric luminosity of approximately $5\times 10^{13}\, \mathrm{ L}_\odot$. Such a very high AGN luminosity suggests that this object is powered by an ≈1.6 × 10$^9\, \mathrm{ M}_\odot$ black hole if accreting near the Eddington limit, and is effectively a highly obscured version of an extremely ultraviolet (UV)-luminous (M1450 ≈ −27.3) z ∼ 7 quasar. Notably, these z ∼ 7 quasars are an exceedingly rare population (∼0.001 deg−2), while COS-87259 was identified over a relatively small field. Future very wide area surveys with e.g. Roman and Euclid have the potential to identify many more extremely red yet UV-bright z ≳ 7 objects similar to COS-87259, providing richer insight into the occurrence of intense obscured star formation and supermassive black hole growth among this population.

CEERS Spectroscopic Confirmation of NIRCam-selected z ≳ 8 Galaxy Candidates with JWST/NIRSpec: Initial Characterization of Their Properties

“…This finding is in line with recent JWST results that less luminous LBGs at z ∼ 7 − 8 have similarly high sSFR of ;80 Gyr −1 (Endsley et al 2023). As discussed in Endsley et al (2023), the high sSFR in the less luminous LBGs, highlighted by our z spec sample and the lensed galaxies, is likely caused by young stellar populations. This is consistent with our SED results showing the presence of the young stellar populations (<10 Myr) accounting for the total mass of ;20% of the galaxy mass (Table 2).…”

“…The upper limits of Hβ EW (MPT-ID2, ID4) are also included in this calculation, assuming that zero and the 3σ error correspond to its center and standard deviation of the log-normal distribution. For comparison, we also present the EW distribution estimated from the photometric-based SED analysis for LBGs at z ∼ 7 with similar UV luminosity (M UV ∼ −19.5; solid line) with JWST data and brighter LBGs (M UV ∼ −21.5; dashed line) at z ∼ 7 (Endsley et al 2023).…”

Yeah or Nay on Black Holes as Explanation for Dark Energy?

“…Conventional views agree with our analysis: inflation (from 10 −36 seconds to between 10−33 and 10 −32 seconds after the Big Bang) takes place before the radiation dominated area (After Inflation, and until about 47,000 years after the Big Bang), when the primordial black holes are expected to have appeared [23,[33][34][35][36][37], if they exist at all.…”

“…This, along with the very old galaxies recently encountered with JWST are challenging Cosmology today. Especially very early on after the big bang as for example reported in [32,33], and references in [34]. Yet it does not challenge the existence of the big bang contrary to what others have claimed [125,126].…”

Quasar Luminosity Function at z = 7

“…Onoue et al (2021) detected strong C IV λ1549 emission in one of them, pointing to the presence of hard ionizing radiation from AGN. A number of other observations (e.g., Fujimoto et al 2022;Endsley et al 2023) are revealing (candidates for) such a high-z obscured population, and substantially more objects may be identified in the coming few years with the James Webb Space Telescope (JWST).…”