Tracing the evolution of dust-obscured activity using sub-millimetre galaxy populations from STUDIES and AS2UDS

Abstract

We analyse the physical properties of 121 SNR ≥ 5 sub-millimetre galaxies (SMGs) from the STUDIES 450-μm survey. We model their UV-to-radio spectral energy distributions using magphys+photo-z and compare the results to similar modelling of 850-μm-selected SMG sample from AS2UDS, to understand the fundamental physical differences between the two populations at the observed depths. The redshift distribution of the 450-μm sample has a median of z = 1.85 ± 0.12 and can be described by strong evolution of the far-infrared luminosity function. The fainter 450-μm sample has ∼ 14 times higher space density than the brighter 850-μm sample at z ≲ 2, and a comparable space density at z = 2–3, before rapidly declining, suggesting LIRGs are the main obscured population at z ∼ 1–2, while ULIRGs dominate at higher redshifts. We construct rest-frame ∼ 180-μm-selected and dust-mass-matched samples at z = 1–2 and z = 3–4 from the 450-μm and 850-μm samples, respectively, to probe the evolution of a uniform sample of galaxies spanning the cosmic noon era. Using far-infrared luminosity, dust masses and an optically-thick dust model, we suggest that higher-redshift sources have higher dust densities due to inferred dust continuum sizes which are roughly half of those for the lower-redshift population at a given dust mass, leading to higher dust attenuation. We track the evolution in the cosmic dust mass density and suggest that the dust content of galaxies is governed by a combination of both the variation of gas content and dust destruction timescale.

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

“…This leads to a strong offset in the inferred dust masses, which are typically 0.5 dex (i.e., a factor of 3) lower in the general opacity scenario than in the optically thin case (the same offsets are also seen in the medians of the stacked likelihood distributions in Figure 9). These differences can have very strong implications when interpreting inferred dust masses in the context of chemical evolution and dust production models, especially at high redshift, where current models required substantial ISM growth to account for large inferred dust masses (e.g., Rowlands et al 2014;Mancini et al 2015;Dudzevičiūtė et al 2020Dudzevičiūtė et al , 2021. Nevertheless, we find that the inferred dust luminosities and emissivity indexes seem quite robust against dust model assumptions, with no systematic offsets.…”

“…This is true at least for SMGs, which, based on their relatively high stellar masses (M *  10 10 M e ; da Cunha et al 2015;Dudzevičiūtė et al 2020), are likely to have already reached solar metallicities in their ISM. We speculate that therefore they are likely to have reached a critical metallicity for their dust-grain evolution to be happening mainly through ISM growth (see Dudzevičiūtė et al 2021), which is also thought to be the dominant mechanism in the Milky Way and other present-day galaxies (e.g., Asano et al 2013). A larger number of robust measurements of the emissivity index of high-redshift galaxies of lower masses/metallicities with ALMA would help establish whether there is an evolution of the dust-grain properties in galaxies with a less chemically evolved ISM.…”

“…In recent years, there has been much debate over the origin of the large dust masses of SMGs (typically  10 8 M e , i.e., a few percent of their stellar mass; e.g., Dudzevičiūtė et al 2020). However, such measurements have mostly been performed for biased samples (that favor the dustiest sources) and until recently relied solely on single-dish observations (e.g., Rowlands et al 2014;Dudzevičiūtė et al 2021). The buildup of such large dust masses over timescales ∼0.5-2 Gyr is extremely difficult to explain with models of dust production and growth relying solely on stellar sources (e.g., Morgan & Edmunds 2003;Dwek et al 2007).…”

Extensive Lensing Survey of Optical and Near-infrared Dark Objects (El Sonido): HST H-faint Galaxies behind 101 Lensing Clusters

“…This is typically observed at flux densities of 1 mJy shortward of 1 mm in the submillimeter galaxies (SMGs) that are discovered in abundance at z ; 1-4 (see reviews in Casey et al 2014a;Hodge & da Cunha 2020). The high observed dust-to-stellar luminosity ratio and red stellar continuum color of SMGs suggest a high dust attenuation, which is typically A V  2 (e.g., da Cunha et al 2015;Dudzevičiūtė et al 2020Dudzevičiūtė et al , 2021.…”

A simple numerical experiment on the dust temperature bias for Lyman break galaxies at $z\gtrsim 5$

“…Recently, the SCUBA-2 Ultra Deep Imaging East Asian Observatory Survey (STUDIES) has been conducted at 450 𝜇m, starting to detect galaxies at the knee of the IR luminosity function up to 𝑧 ∼ 3 (Wang et al 2017b). Optical counterpart identifications and multi-wavelength SED fitting were successfully performed up to 𝑧 ∼ 4 (Lim et al 2020;Dudzevičiūtė et al 2021). It is highly probable that the 450 𝜇m band is also useful at 𝑧 5; thus, we discuss the detectability at 450 𝜇m in this paper.…”