The ALMA Frontier Fields Survey

Abstract

Context. Characterizing the number counts of faint (i.e., sub-mJy and especially sub-100 μJy), dusty star-forming galaxies is currently a challenge even for deep, high-resolution observations in the FIR-to-mm regime. They are predicted to account for approximately half of the total extragalactic background light at those wavelengths. Searching for dusty star-forming galaxies behind massive galaxy clusters benefits from strong lensing, enhancing their measured emission while increasing spatial resolution. Derived number counts depend, however, on mass reconstruction models that properly constrain these clusters. Aims. We aim to estimate the 1.1 mm number counts along the line of sight of three galaxy clusters, Abell 2744, MACS J0416.1–2403, and MACS J1149.5+2223, which are part of the ALMA Frontier Fields Survey. We have performed detailed simulations to correct these counts for lensing effects, probing down to the sub-mJy flux density level. Methods. We created a source catalog based on ALMA 1.1 mm continuum detections. We used several publicly available lensing models for the galaxy clusters to derive the intrinsic flux densities of these sources. We performed Monte Carlo simulations of the number counts for a detailed treatment of the uncertainties in the magnifications and adopted source redshifts. Results. We estimate lensing-corrected number counts at 1.1 mm using source detections down to S/N = 4.5. In each cluster field, we find an overall agreement among the number counts derived for the different lens models, despite their systematic variations regarding source magnifications and effective areas. Combining all cluster fields, our number counts span ∼2.5 dex in demagnified flux density, from several mJy down to tens of μJy. Both our differential and cumulative number counts are consistent with recent estimates from deep ALMA observations at a 3σ level. Below ≈0.1 mJy, however, our cumulative counts are lower by ≈1 dex, suggesting a flattening in the number counts. Conclusions. We derive 1.1 mm number counts around three well-studied galaxy clusters following a statistical approach. In our deepest ALMA mosaic, we estimate number counts for intrinsic flux densities ≈4 times fainter than the rms level. This highlights the potential of probing the sub-10 μJy population in larger samples of galaxy cluster fields with deeper ALMA observations.

The ALMA Spectroscopic Survey in the HUDF: Deep 1.2 mm Continuum Number Counts

“…These studies mainly sample the bright end of the 1 mm galaxy population and correspond to a flux density range of > n S 1 mJy. The studies at 1.1-1.3 millimeters correspond to deep fields and large mosaics in blank and lensing fields (Hatsukade et al 2013(Hatsukade et al , 2016Aravena et al 2016;Dunlop et al 2017;Umehata et al 2017;Franco et al 2018;Hatsukade et al 2018;Muñoz Arancibia et al 2018) as well as to the combination of multiple targeted fields (Ono et al 2014;Carniani et al 2015;Fujimoto et al 2016;Oteo et al 2016). Our results are in agreement with the results from other studies at S ν >0.1 mJy but are lower than the rest at fainter flux density values.…”

“…The next step was to conduct deep ALMA surveys to search for the population of faint DSFGs. These first attempts focused on fields with deep archival data such as the Subaru/ XMM-Newton Deep Survey Field (Hatsukade et al 2013(Hatsukade et al , 2016, SSA22 (Umehata et al 2017), the GOODS-S/Hubble Ultra Deep Field (HUDF, Aravena et al 2016;Walter et al 2016;Dunlop et al 2017;Franco et al 2018;Hatsukade et al 2018), Frontier Fields (González-López et al 2017;Muñoz Arancibia et al 2018), on calibrator fields (Oteo et al 2016), and on combined multiple single-pointing fields (Ono et al 2014;Carniani et al 2015;Fujimoto et al 2016;Oteo et al 2016).…”

Using ALMA to resolve the nature of the early star-forming large-scale structure PLCK G073.4−57.5

“…Hatsukade et al 2013;Ono et al 2014;Carniani et al 2015;Oteo et al 2016;Fujimoto et al 2016), or source numbers found in lensing cluster fields (e.g. González-López et al 2016;Muñoz Arancibia et al 2018), we estimate an expected 1.2-mm source density of 0.6-2 × 10 3 deg −2 , where the lower estimate (from Oteo et al 2016) is derived from a relatively large area of different fields used for the serendipitous searches, which might be expected to reach beyond the effects of cosmic variance. Thus, the number of sources we find in the ALMA pointings of G073.4−57.5 is a factor of 8-30 higher than estimates of the average number of mm sources in the sky.…”

An ALMA survey of the SCUBA-2 CLS UDS field: physical properties of 707 sub-millimetre galaxies

“…The pace of progress of our understanding of the nature and properties of the SMG population has accelerated in the last five years, owing to the commissioning of the Atacama Large Millimetre/Submillimetre Telescope (ALMA), which has enabled high-sensitivity ( 1 mJy rms) and highangular-resolution ( 1 FWHM) observations in the sub-/millimetre wavebands of samples of dust-obscured galaxies at high redshifts, including SMGs. In the first few years of operations, ALMA has been used to undertake a number of typically deeper continuum surveys of small contiguous fields (including lensing clusters and proto-cluster regions), with areas of 10s of arcmin 2 (Walter et al 2016;Hatsukade et al 2016;Dunlop et al 2017;Umehata et al 2018;Hatsukade et al 2018;Franco et al 2018;Muñoz Arancibia et al 2018). These small field studies typically contain modest numbers of sources at flux limits of S 870 0.1-1 mJy (corresponding to star-formation rates of ∼ 10-100 M yr −1 ) and so provide a valuable link between the bright SMGs seen in the panoramic single-dish surveys and the populations of typically less-actively star-forming galaxies studied in UV/optical-selected surveys.…”