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The Atacama Large Millimeter Array (ALMA) Large Program to INvestigate [CII] at Early times (ALPINE) targets the [CII] 158 μ m line and the far-infrared continuum in 118 spectroscopically confirmed star-forming galaxies between z = 4.4 and z = 5.9. It represents the first large [CII] statistical sample built in this redshift range. We present details regarding the data processing and the construction of the catalogs. We detected 23 of our targets in the continuum. To derive accurate infrared luminosities and obscured star formation rates (SFRs), we measured the conversion factor from the ALMA 158 μ m rest-frame dust continuum luminosity to the total infrared luminosity ( L IR ) after constraining the dust spectral energy distribution by stacking a photometric sample similar to ALPINE in ancillary single-dish far-infrared data. We found that our continuum detections have a median L IR of 4.4 × 10 11 L ⊙ . We also detected 57 additional continuum sources in our ALMA pointings. They are at a lower redshift than the ALPINE targets, with a mean photometric redshift of 2.5 ± 0.2. We measured the 850 μ m number counts between 0.35 and 3.5 mJy, thus improving the current interferometric constraints in this flux density range. We found a slope break in the number counts around 3 mJy with a shallower slope below this value. More than 40% of the cosmic infrared background is emitted by sources brighter than 0.35 mJy. Finally, we detected the [CII] line in 75 of our targets. Their median [CII] luminosity is 4.8 × 10 8 L ⊙ and their median full width at half maximum is 252 km s −1 . After measuring the mean obscured SFR in various [CII] luminosity bins by stacking ALPINE continuum data, we find a good agreement between our data and the local and predicted SFR– L [CII] relations.
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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.
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- Award ID(s):
- 1908284
- PAR ID:
- 10398610
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 520
- Issue:
- 3
- ISSN:
- 0035-8711
- Format(s):
- Medium: X Size: p. 4609-4620
- Size(s):
- p. 4609-4620
- Sponsoring Org:
- National Science Foundation
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