The Evolution of the IR Luminosity Function and Dust-obscured Star Formation over the Past 13 Billion Years

Abstract

We present the first results from the Mapping Obscuration to Reionization with ALMA (MORA) survey, the largest Atacama Large Millimeter/submillimeter Array (ALMA) blank-field contiguous survey to date (184 arcmin 2 ) and the only at 2 mm to search for dusty star-forming galaxies (DSFGs). We use the 13 sources detected above 5σ to estimate the first ALMA galaxy number counts at this wavelength. These number counts are then combined with the state-of-the-art galaxy number counts at 1.2 and 3 mm and with a backward evolution model to place constraints on the evolution of the IR luminosity function and dust-obscured star formation in the past 13 billion years. Our results suggest a steep redshift evolution on the space density of DSFGs and confirm the flattening of the IR luminosity function at faint luminosities, with a slope of a = --+ 0.42 LF 0.04 0.02 . We conclude that the dust-obscured component, which peaks at z ≈ 2-2.5, has dominated the cosmic history of star formation for the past ∼12 billion years, back to z ∼ 4. At z = 5, the dust-obscured star formation is estimated to be ∼35% of the total star formation rate density and decreases to 25%-20% at z = 6-7, implying a minor contribution of dustenshrouded star formation in the first billion years of the universe. With the dust-obscured star formation history constrained up to the end of the epoch of reionization, our results provide a benchmark to test galaxy formation models, to study the galaxy mass assembly history, and to understand the dust and metal enrichment of the universe at early times.

Cosmic Evolution of the H2 Mass Density and the Epoch of Molecular Gas

“…We note that our inferred contribution of SMGs is also likely under-estimated as we expect that approximately 20% of SMGs are undetected in our nearinfrared selected sample (e.g., Dudzevičiūtė et al 2019). Our finding is in keeping with Zavala et al (2021) who find that bright SMGS (L IR > 10 12 L ) dominate the obscured star formation rate density at z ≈ 2 and also Magnelli et al (2020) who find that the bulk of dust and gas in galaxies is locked in massive star-forming galaxies.…”

Early science with the Large Millimeter Telescope: a 1.1 mm AzTEC survey of red-Herschel dusty star-forming galaxies

“…Combining our estimated space density and the median SFR of our phot > 4 sample (∼ 2500 M ⊙ yr −1 not corrected for potential gravitational lensing effects), we conclude that luminous red Herschel sources contribute 8 × 10 −4 M ⊙ yr −1 Mpc −3 to the obscured star formation at 4 < < 6. This value is in very good agreement with the recent estimations of the dust-obscured star formation rate density presented by Zavala et al (2021) based on ALMA number counts at 1.2 mm, 2 mm, and 3 mm. Their model predicts a dustobscured star formation rate density of ≈ 10 +5 −6 ×10 −4 M ⊙ yr −1 Mpc −3 at = 5 from galaxies with IR luminosities in the range of our sources (12.8 ≤ log 10 ( IR / ⊙ ) ≤ 13.5).…”

“…Note that our observations are far from being confusion noise limited. Assuming the most recent 1.1 mm number counts fromZavala et al (2021) and defining confusion noise at the level of 1/30 source per beam, we estimate the confusion noise to be around 0.35 mJy for the 32-m LMT, which is a factor of ≈ 4 − 6× deeper than the typical noise in our observations. MNRAS 000, 1-24 (2021)…”

Measurements of the Dust Properties in z ≃ 1–3 Submillimeter Galaxies with ALMA

“…Selecting SMGs from observations at longer wavelengths is thought to favor galaxies at higher redshifts (e.g., Smolčić et al 2012;Vieira et al 2013;Staguhn et al 2014;Magnelli et al 2019;Hodge & da Cunha 2020), although it is difficult to compare the redshift distributions in an unbiased way (see, e.g., Zavala et al 2014 for a discussion), and account for intrinsic variations of galaxy far-IR spectral energy distributions (SEDs). Nevertheless, the 2 mm band has been put forth as a potential candidate to detect high-redshift (z > 3) galaxies (e.g., Casey et al 2018aCasey et al , 2018bCasey et al , 2019Zavala et al 2021). The negative k-correction is stronger at 2 mm than at 850 μm; thus, for a fixed SED, the 2 mm band should pick up more high-redshift galaxies than at 870 μm.…”

“…In addition, better atmospheric transmission and larger fields of view can be achieved at 2 mm (but corresponding poorer resolution). Such an effort is currently ongoing (see Zavala et al 2021 for first results). To understand the relationship between the populations detected at 850 μm and at 2 mm, we require a detailed characterization of the (sub)millimeter SEDs of these sources.…”