The bright extragalactic ALMA redshift survey (BEARS) – II. Millimetre photometry of gravitational lens candidates

Abstract

We present 101- and 151-GHz ALMA continuum images for 85 fields selected from Herschel observations that have 500-μm flux densities >80 mJy and 250–500-μm colours consistent with z > 2, most of which are expected to be gravitationally lensed or hyperluminous infrared galaxies. Approximately half of the Herschel 500-μm sources were resolved into multiple ALMA sources, but 11 of the 15 brightest 500-μm Herschel sources correspond to individual ALMA sources. For the 37 fields containing either a single source with a spectroscopic redshift or two sources with the same spectroscopic redshift, we examined the colour temperatures and dust emissivity indices. The colour temperatures only vary weakly with redshift and are statistically consistent with no redshift-dependent temperature variations, which generally corresponds to results from other samples selected in far-infrared, submillimetre, or millimetre bands but not to results from samples selected in optical or near-infrared bands. The dust emissivity indices, with very few exceptions, are largely consistent with a value of 2. We also compared spectroscopic redshifts to photometric redshifts based on spectral energy distribution templates designed for infrared-bright high-redshift galaxies. While the templates systematically underestimate the redshifts by ∼15 per cent, the inclusion of ALMA data decreases the scatter in the predicted redshifts by a factor of ∼2, illustrating the potential usefulness of these millimetre data for estimating photometric redshifts.

An ALMA Spectroscopic Survey of the Brightest Submillimeter Galaxies in the SCUBA-2-COSMOS Field (AS2COSPEC): Physical Properties of z = 2–5 Ultra- and Hyperluminous Infrared Galaxies

“…Figures 9(e) and (f) present the variations of β as a function of L IR and redshift for our sample, the literature SMGs (Birkin et al 2021;Bendo et al 2023;McKay et al 2023), and the local Herschel-selected galaxies from Smith et al (2013). We perform linear fits to the parameters and find no correlations with either L IR or redshift, suggesting that the dust grain properties do not significantly correlate with L IR or redshift in galaxies.…”

“…For studies that lack sufficient photometry, β, which is degenerate with temperature, is commonly fixed. While β is typically assumed to be between 1.5 and 2.0 (Scoville et al 2017;Kaasinen et al 2019;Dudzevičiūtė et al 2020), recent studies suggest that β is consistent with or possibly greater than 2 (Magnelli et al 2012;Casey et al 2021;da Cunha et al 2021;Cooper et al 2022;Bendo et al 2023;McKay et al 2023), which is similar to the value in the local Universe (Smith et al 2013) and suggests a dust assembly scenario by dust grain growth in the interstellar medium (ISM). A detailed investigation of β is useful not only in constraining dust grain growth models (Hirashita et al 2014) but also in analyses of even higher-redshift galaxies that usually have sparse sampling of millimeter photometry.…”

Observing Dusty Star-Forming Galaxies at the Cosmic Noon through Gravitational Lensing: Perspectives from New-Generation Telescopes

“…The BEARS survey is another recent redshift campaign [143][144][145] performed with the ALMA using both the 12 m array and the Atacama Compact Array (ACA) and targeting the brightest sources in the southern field of the H-ATLAS. While 81 sources were targeted, 142 objects were resolved, and 71 were spectroscopically confirmed through the detection of [CI], CO, and H 2 O lines.…”

“…The outcomes of this redshift campaign lead to several follow-up observations. The authors of [144] measured the continuum emission by reconstructing the SED of these data, and [145] estimated the physical conditions of the ISM through the detected spectral lines ([CI], CO, and H 2 O lines).…”

The z-GAL survey

“…Using the detected 12 CO lines and typical typical line luminosity ratios of sub-millimetre galaxies (SMGs) [40], [36] computed the 12 CO(1 − 0) luminosities of the z-GAL sources and converted them into molecular gas masses, M mol , adopting a conversion factor α CO = 4.0 M (K km s −1 pc 2 ) −1 [41]. [39]). The solid black line is the fitted relation we find for the z-GAL sources with α = 0.69 ± 0.04 and the shaded region is the corresponding confidence level.…”