ALMA Lensing Cluster Survey: Deep 1.2 mm Number Counts and Infrared Luminosity Functions at z ≃ 1–8
Seiji Fujimoto, Kotaro Kohno, Masami Ouchi, Masamune Oguri, Vasily Kokorev, Gabriel Brammer, Fengwu Sun, Jorge González-López, Franz E. Bauer, G. B. Caminha, Bunyo Hatsukade, Johan Richard, Ian Smail, Akiyoshi Tsujita, Yoshihiro Ueda, Ryosuke Uematsu, Adi Zitrin, Dan Coe, Jean-Paul Kneib, Marc Postman, Keiichi Umetsu, Claudia del P. Lagos, Gergö Popping, Yiping Ao, Larry Bradley, K. I. Caputi, M. Dessauges‐Zavadsky, Eiichi Egami, Daniel Espada, R. J. Ivison, Mathilde Jauzac, K. K. Knudsen, Anton M. Koekemoer, Georgios E. Magdis, Guillaume Mahler, A. M. Muñoz Arancibia, Timothy Rawle, Kazuhiro Shimasaku, Sune Toft, Hideki Umehata, Francesco Valentino, Tao Wang, Wei-Hao Wang
Abstract
Abstract We present a statistical study of 180 dust continuum sources identified in 33 massive cluster fields by the Atacama Large Millimeter/submillimeter Array 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 millimeter sources by lensing magnification, including near-infrared (NIR) dark objects showing no counterparts in existing Hubble Space Telescope and Spitzer images. The dust continuum sources belong to a blind sample ( N = 141) with signal-to-noise ratio (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 ∼7 μ Jy, and find that the total integrated 1.2 mm flux is <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>20.7</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>6.5</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>8.5</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> Jy deg −2 , resolving ≃80% of the cosmic infrared background light. The resolved fraction varies by a factor of 0.6–1.1 due to the completeness correction depending on the spatial size of the millimeter emission. We also derive infrared (IR) luminosity functions (LFs) at z = 0.6–7.5 with the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>1</mml:mn> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:msub> <mml:mrow> <mml:mi>V</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>max</mml:mi> </mml:mrow> </mml:msub> </mml:math> method, finding the redshift evolution of IR LFs characterized by positive luminosity and negative density evolution. The total (= UV + IR) cosmic star formation rate density (SFRD) at z > 4 is estimated to be <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>161</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>21</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>25</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> % of the Madau and Dickinson measurements mostly based on rest-frame UV surveys. Although our general understanding of the cosmic SFRD is unlikely to change beyond a factor of 2, these results add to the weight of evidence for an additional (≈60%) SFRD component contributed by the faint millimeter population, including NIR-dark objects.