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Authors
K. Kohno
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We have conducted 1.1 mm ALMA observations of a contiguous $105 times 50$ or 1.5 arcmin$^2$ window in the SXDF-UDS-CANDELS. We achieved a 5$sigma$ sensitivity of 0.28 mJy, providing a flat sensus of dusty star-forming galaxies with $L_{rm IR} sim6times10^{11}$ $L_odot$ (for $T_{rm dust}$ =40K) up to $zsim10$ thanks to the negative K-correction at this wavelength. We detected 5 brightest sources (S/N$>$6) and 18 low-significance sources (5$>$S/N$>$4; these may contain spurious detections, though). One of the 5 brightest ALMA sources ($S_{rm 1.1mm} = 0.84 pm 0.09$ mJy) is extremely faint in the WFC3 and VLT/HAWK-I images, demonstrating that a contiguous ALMA imaging survey is able to uncover a faint dust-obscured population that is invisible in deep optical/near-infrared surveys. We found a possible [CII]-line emitter at $z=5.955$ or a low-$z$ CO emitting galaxy within the field, which may allow us to constrain the [CII] and/or the CO luminosity functions across the history of the universe.
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We report 1.1 mm number counts revealed with the Atacama Large Millimeter/submillimeter Array (ALMA) in the Subaru/XMM-Newton Deep Survey Field (SXDF). The advent of ALMA enables us to reveal millimeter-wavelength number counts down to the faint end without source confusion. However, previous studies are based on the ensemble of serendipitously-detected sources in fields originally targeting different sources and could be biased due to the clustering of sources around the targets. We derive number counts in the flux range of 0.2-2 mJy by using 23 (>=4sigma) sources detected in a continuous 2.0 arcmin$^2$ area of the SXDF. The number counts are consistent with previous results within errors, suggesting that the counts derived from serendipitously-detected sources are not significantly biased, although there could be field-to-field variation due to the small survey area. By using the best-fit function of the number counts, we find that ~40% of the extragalactic background light at 1.1 mm is resolved at S(1.1mm) > 0.2 mJy.
We present first results from the SXDF-ALMA 1.5 arcmin^2 deep survey at 1.1 mm using Atacama Large Millimeter Array (ALMA). The map reaches a 1sigma depth of 55 uJy/beam and covers 12 Halpha-selected star-forming galaxies at z = 2.19 or z=2.53. We have detected continuum emission from three of our Halpha-selected sample, including one compact star-forming galaxy with high stellar surface density, NB2315-07. They are all red in the rest-frame optical and have stellar masses of log (M*/Msun)>10.9 whereas the other blue, main-sequence galaxies with log(M*/Msun)=10.0-10.8 are exceedingly faint, <290 uJy (2sigma upper limit). We also find the 1.1 mm-brightest galaxy, NB2315-02, to be associated with a compact (R_e=0.7+-0.1 kpc), dusty star-forming component. Given high gas fraction (44^{+20}_{-8}% or 37^{+25}_{-3}%) and high star formation rate surface density (126^{+27}_{-30} Msun yr^{-1}kpc^{-2}), the concentrated starburst can within less than 50^{+12}_{-11} Myr build up a stellar surface density matching that of massive compact galaxies at z~2, provided at least 19+-3% of the total gas is converted into stars in the galaxy centre. On the other hand, NB2315-07, which already has such a high stellar surface density core, shows a gas fraction (23+-8%) and is located in the lower envelope of the star formation main-sequence. This compact less star-forming galaxy is likely to be in an intermediate phase between compact dusty star-forming and quiescent galaxies.
We present a multi-wavelength analysis of five submillimeter sources (S_1.1mm = 0.54-2.02 mJy) that were detected during our 1.1-mm-deep continuum survey in the SXDF-UDS-CANDELS field (2 arcmin^2, 1sigma = 0.055 mJy beam^-1) using the Atacama Large Millimeter/submillimeter Array (ALMA). The two brightest sources correspond to a known single-dish (AzTEC) selected bright submillimeter galaxy (SMG), whereas the remaining three are faint SMGs newly uncovered by ALMA. If we exclude the two brightest sources, the contribution of the ALMA-detected faint SMGs to the infrared extragalactic background light is estimated to be ~ 4.1^{+5.4}_{-3.0} Jy deg^{-2}, which corresponds to ~ 16^{+22}_{-12}% of the infrared extragalactic background light. This suggests that their contribution to the infrared extragalactic background light is as large as that of bright SMGs. We identified multi-wavelength counterparts of the five ALMA sources. One of the sources (SXDF-ALMA3) is extremely faint in the optical to near-infrared region despite its infrared luminosity (L_IR ~ 1e12 L_sun or SFR ~ 100 M_sun yr^{-1}). By fitting the spectral energy distributions (SEDs) at the optical-to-near-infrared wavelengths of the remaining four ALMA sources, we obtained the photometric redshifts (z_photo) and stellar masses (M_*): z_photo ~ 1.3-2.5, M_* ~ (3.5-9.5)e10 M_sun. We also derived their star formation rates (SFRs) and specific SFRs (sSFRs) as ~ 30-200 M_sun yr^{-1} and ~ 0.8-2 Gyr^{-1}, respectively. These values imply that they are main-sequence star-forming galaxies.
We present the public release of the stellar mass catalogs for the GOODS-S and UDS fields obtained using some of the deepest near-IR images available, achieved as part of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) project. We combine the effort from ten different teams, who computed the stellar masses using the same photometry and the same redshifts. Each team adopted their preferred fitting code, assumptions, priors, and parameter grid. The combination of results using the same underlying stellar isochrones reduces the systematics associated with the fitting code and other choices. Thanks to the availability of different estimates, we can test the effect of some specific parameters and assumptions on the stellar mass estimate. The choice of the stellar isochrone library turns out to have the largest effect on the galaxy stellar mass estimates, resulting in the largest distributions around the median value (with a semi interquartile range larger than 0.1 dex). On the other hand, for most galaxies, the stellar mass estimates are relatively insensitive to the different parameterizations of the star formation history. The inclusion of nebular emission in the model spectra does not have a significant impact for the majority of galaxies (less than a factor of 2 for ~80% of the sample). Nevertheless, the stellar mass for the subsample of young galaxies (age < 100 Myr), especially in particular redshift ranges (e.g., 2.2 < z < 2.4, 3.2 < z < 3.6, and 5.5 < z < 6.5), can be seriously overestimated (by up to a factor of 10 for < 20 Myr sources) if nebular contribution is ignored.
We present the catalogue and properties of sources in AS2UDS, an 870-$mu$m continuum survey with the Atacama Large Millimetre/sub-millimetre Array (ALMA) of 716 single-dish sub-millimetre sources detected in the UKIDSS/UDS field by the SCUBA-2 Cosmology Legacy Survey. In our sensitive ALMA follow-up observations we detect 708 sub-millimetre galaxies (SMGs) at $>$,4.3$sigma$ significance across the $sim$,1-degree diameter field. We combine our precise ALMA positions with the extensive multi-wavelength coverage in the UDS field to fit the spectral energy distributions of our SMGs to derive a median redshift of $z_{rm phot}=$,2.61$pm$0.09. This large sample reveals a statistically significant trend of increasing sub-millimetre flux with redshift suggestive of galaxy downsizing. 101 ALMA maps do not show a $>$,4.3$sigma$ SMG, but we demonstrate from stacking {it Herschel} SPIRE observations at these positions, that the vast majority of these blank maps correspond to real single-dish sub-millimetre sources. We further show that these blank maps contain an excess of galaxies at $z_{rm phot}=$,1.5--4 compared to random fields, similar to the redshift range of the ALMA-detected SMGs. In addition, we combine X-ray and mid-infrared active galaxy nuclei activity (AGN) indicators to yield a likely range for the AGN fraction of 8--28,% in our sample. Finally, we compare the redshifts of this population of high-redshift, strongly star-forming galaxies with the inferred formation redshifts of massive, passive galaxies being found out to $zsim$,2, finding reasonable agreement -- in support of an evolutionary connection between these two classes of massive galaxy.
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