ALMA Lensing Cluster Survey: Deep 1.2 mm Number Counts and Infrared Luminosity Functions at z~1-8
Seiji Fujimoto (Cosmic Dawn Center, Niels Bohr Institute)
Tuesday 20/09/2022 @ 14:00, Sala IV piano Battiferro + remote
I present a large statistics of 180 dust continuum sources identified in 33 massive cluster fields by ALMA Lensing Cluster Survey (ALCS) over a total of 133 arcmin^2 area homogeneously observed at 1.2~mm. ALCS enables us to detect extremely faint mm sources by lensing magnification and near infrared (NIR) dark objects showing no counterparts in deep Hubble Space Telescope and Spitzer images. The dust continuum sources belong to a blind sample N=141 with S/N >~ 5.0 (a purity of > 0.99) or a secondary sample (N=39) with S/N=4.0-5.0 screened by priors. With the blind sample, we securely derive 1.2-mm number counts down to ~7uJy, and find that the total integrated 1.2mm flux is 20.5^{+0.3}_{-0.3} Jy deg^-2, resolving ~ 80% of the cosmic infrared background light. The resolved fraction can be changed by a factor of 0.6-1.1 due to the completeness correction depending on the faint-end slope. In conjunction with serendipitous mm sources at z>7 presented in the literature, we also derive infrared (IR) luminosity functions (LFs) at z=0.6-7.5 with the 1/V_max method. We confirm recent reports of the redshift evolution of IR LFs characterized by the positive luminosity and negative density evolution. The total (=UV+IR) cosmic star-formation rate density (SFRD) at z>4 is estimated to be 140^{+60}_{-64} % of the established measurements from optical-NIR surveys. Although our general understanding of the cosmic SFRD is unchanged beyond a factor of 2, our results suggest a possibility that there is an additional (~ 40%) SFRD component contributed by the faint-mm population including NIR dark objects.