- ID:
- ivo://CDS.VizieR/J/A+A/633/A160
- Title:
- ALMA Frontier Fields Survey. V.
- Short Name:
- J/A+A/633/A160
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Hubble Frontier Fields offer an exceptionally deep window into the high-redshift universe, covering a substantially larger area than the Hubble Ultra-Deep field at low magnification and probing 1-2mags deeper in exceptional high-magnification regions. This unique parameter space, coupled with the exceptional multi-wavelength ancillary data, can facilitate for useful insights into distant galaxy populations. We aim to leverage Atacama Large Millimetre Array (ALMA) band 6 (~263GHz) mosaics in the central portions of five Frontier Fields to characterize the infrared (IR) properties of 1582 ultraviolet (UV)-selected Lyman-Break Galaxies (LBGs) at redshifts of z~2-8. We investigated individual and stacked fluxes and IR excess (IRX) values of the LBG sample as functions of stellar mass (M_star), redshift, UV luminosity and slope {beta}, and lensing magnification. LBG samples were derived from color-selection and photometric redshift estimation with Hubble Space Telescope photometry. Spectral energy distributions (SED)-templates were fit to obtain luminosities, stellar masses, and star formation rates for the LBG candidates. We obtained individual IR flux and IRX estimates, as well as stacked averages, using both ALMA images and u-v visibilities. Two (2) LBG candidates were individually detected above a significance of 4.1-sigma, while stacked samples of the remaining LBG candidates yielded no significant detections. We investigated our detections and upper limits in the context of the IRX-M_star and IRX-{beta} relations, probing at least one dex lower in stellar mass than past studies have done. Our upper limits exclude substantial portions of parameter space and they are sufficiently deep in a handful of cases to create mild tension with the typically assumed attenuation and consensus relations. We observe a clear and smooth trend between M* and {beta}, which extends to low masses and blue (low) {beta} values, consistent with expectations from previous works.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/820/83
- Title:
- ALMA galaxy properties in the COSMOS survey field
- Short Name:
- J/ApJ/820/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- ALMA Cycle 2 observations of long-wavelength dust emission in 145 star-forming galaxies are used to probe the evolution of the star-forming interstellar medium (ISM). We also develop a physical basis and empirical calibration (with 72 low-z and z~2 galaxies) for using the dust continuum as a quantitative probe of ISM masses. The galaxies with the highest star formation rates (SFRs) at <z>=2.2 and 4.4 have gas masses up to 100 times that of the Milky Way and gas mass fractions reaching 50%-80%, i.e., gas masses 1-4x their stellar masses. We find a single high-z star formation law: SFR=35 M_mol_^0.89^x(1+z)_z=2_^0.95^x(sSFR)_MS_^0.23^ M_{sun}_/yr - an approximately linear dependence on the ISM mass and an increased star formation efficiency per unit gas mass at higher redshift. Galaxies above the main sequence (MS) have larger gas masses but are converting their ISM into stars on a timescale only slightly shorter than those on the MS; thus, these "starbursts" are largely the result of having greatly increased gas masses rather than an increased efficiency of converting gas to stars. At z>1, the entire population of star-forming galaxies has ~2-5 times shorter gas depletion times than low-z galaxies. These shorter depletion times indicate a different mode of star formation in the early universe - most likely dynamically driven by compressive, high-dispersion gas motions - a natural consequence of the high gas accretion rates.
- ID:
- ivo://CDS.VizieR/J/ApJ/783/84
- Title:
- ALMA observations in 107 galaxies at z=0.2-2.5
- Short Name:
- J/ApJ/783/84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The use of submillimeter dust continuum emission to probe the mass of interstellar dust and gas in galaxies is empirically calibrated using samples of local star-forming galaxies, Planck observations of the Milky Way, and high-redshift submillimeter galaxies. All of these objects suggest a similar calibration, strongly supporting the view that the Rayleigh-Jeans tail of the dust emission can be used as an accurate and very fast probe of the interstellar medium (ISM) in galaxies. We present ALMA Cycle 0 observations of the Band 7 (350GHz) dust emission in 107 galaxies from z=0.2 to 2.5. Three samples of galaxies with a total of 101 galaxies were stellar-mass-selected from COSMOS to have M_*_=~10^11^M_{sun}_:37 at z~0.4, 33 at z~0.9, and 31 at z=2. A fourth sample with six infrared-luminous galaxies at z=2 was observed for comparison with the purely mass-selected samples. From the fluxes detected in the stacked images for each sample, we find that the ISM content has decreased by a factor ~6 from 1 to 2x10^10^M_{sun}_ at both z=2 and 0.9 down to ~2x10^9^M_{sun}_at z=0.4. The infrared-luminous sample at z=2 shows a further ~4 times increase in M_ISM_compared with the equivalent non-infrared-bright sample at the same redshift. The gas mass fractions are ~2%+/-0.5%, 12%+/-3%, 14%+/-2%, and 53%+/-3% for the four subsamples (z=0.4, 0.9, and 2 and infrared-bright galaxies).
- ID:
- ivo://CDS.VizieR/J/ApJ/768/91
- Title:
- ALMA observations of LESS submm galaxies
- Short Name:
- J/ApJ/768/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 0 survey of 126 submillimeter sources from the LABOCA ECDFS Submillimeter Survey (LESS). Our 870{mu}m survey with ALMA (ALESS) has produced maps ~3x deeper and with a beam area ~200x smaller than the original LESS observations, doubling the current number of interferometrically-observed submillimeter sources. The high resolution of these maps allows us to resolve sources that were previously blended and accurately identify the origin of the submillimeter emission. We discuss the creation of the ALESS submillimeter galaxy (SMG) catalog, including the main sample of 99 SMGs and a supplementary sample of 32 SMGs. We find that at least 35% (possibly up to 50%) of the detected LABOCA sources have been resolved into multiple SMGs, and that the average number of SMGs per LESS source increases with LESS flux density. Using the (now precisely known) SMG positions, we empirically test the theoretical expectation for the uncertainty in the single-dish source positions. We also compare our catalog to the previously predicted radio/mid-infrared counterparts, finding that 45% of the ALESS SMGs were missed by this method. Our ~1.6" resolution allows us to measure a size of ~9kpcx5kpc for the rest-frame ~300{mu}m emission region in one resolved SMG, implying a star formation rate surface density of 80M_{sun}_/yr/kpc2, and we constrain the emission regions in the remaining SMGs to be <10kpc. As the first statistically reliable survey of SMGs, this will provide the basis for an unbiased multiwavelength study of SMG properties.
- ID:
- ivo://CDS.VizieR/J/ApJ/901/74
- Title:
- ALMA obs. of UDS and GOODS-S massive galaxies
- Short Name:
- J/ApJ/901/74
- Date:
- 18 Feb 2022 09:10:36
- Publisher:
- CDS
- Description:
- We present 0.2 resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations at 870um in a stellar mass-selected sample of 85 massive (M*>10^11^M_{sun}_) star-forming galaxies (SFGs) at z=1.9-2.6 in the CANDELS/3D-Hubble Space Telescope fields of UDS and GOODS-S. We measure the effective radius of the rest-frame far-infrared (FIR) emission for 62 massive SFGs. They are distributed over wide ranges of FIR size from R_e,FIR_=0.4kpc to R_e,FIR_=6kpc. The effective radius of the FIR emission is smaller by a factor of 2.3_-1.0_^+1.9^ than the effective radius of the optical emission and is smaller by a factor of 1.9_-1.0_^+1.9^ than the half-mass radius. Taking into account potential extended components, the FIR size would change only by ~10%. By combining the spatial distributions of the FIR and optical emission, we investigate how galaxies change the effective radius of the optical emission and the stellar mass within a radius of 1kpc, M_1kpc_. The compact starburst puts most of the massive SFGs on the mass-size relation for quiescent galaxies (QGs) at z~2 within 300Myr if the current star formation activity and its spatial distribution are maintained. We also find that within 300Myr, ~38% of massive SFGs can reach the central mass of M_1kpc_=10^10.5^M_{sun}_, which is around the boundary between massive SFGs and QGs. These results suggest an outside-in transformation scenario in which a dense core is formed at the center of a more extended disk, likely via dissipative in-disk inflows. Synchronized observations at ALMA 870um and James Webb Space Telescope 3-4um will explicitly verify this scenario.
- ID:
- ivo://CDS.VizieR/J/ApJ/882/138
- Title:
- ALMA Spectroscopic Survey in the HUDF (ASPECS)
- Short Name:
- J/ApJ/882/138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use the results from the ALMA large program ASPECS, the spectroscopic survey in the Hubble Ultra Deep Field (HUDF), to constrain CO luminosity functions of galaxies and the resulting redshift evolution of {rho}(H_2_). The broad frequency range covered enables us to identify CO emission lines of different rotational transitions in the HUDF at z>1. We find strong evidence that the CO luminosity function evolves with redshift, with the knee of the CO luminosity function decreasing in luminosity by an order of magnitude from ~2 to the local universe. Based on Schechter fits, we estimate that our observations recover the majority (up to ~90%, depending on the assumptions on the faint end) of the total cosmic CO luminosity at z=1.0-3.1. After correcting for CO excitation, and adopting a Galactic CO-to-H_2_ conversion factor, we constrain the evolution of the cosmic molecular gas density {rho}(H_2_): this cosmic gas density peaks at z~1.5 and drops by a factor of 6.5_-1.4_^+1.8^ to the value measured locally. The observed evolution in {rho}(H_2_), therefore, closely matches the evolution of the cosmic star formation rate density {rho}SFR. We verify the robustness of our result with respect to assumptions on source inclusion and/or CO excitation. As the cosmic star formation history can be expressed as the product of the star formation efficiency and the cosmic density of molecular gas, the similar evolution of {rho}(H_2_) and {rho}SFR leaves only little room for a significant evolution of the average star formation efficiency in galaxies since z~3 (85% of cosmic history).
- ID:
- ivo://CDS.VizieR/J/ApJ/839/58
- Title:
- ALMA submm galaxies multi-wavelength data
- Short Name:
- J/ApJ/839/58
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a multi-wavelength analysis of 52 submillimeter galaxies (SMGs), identified using ALMA 870{mu}m continuum imaging in a pilot program to precisely locate bright SCUBA-2-selected submillimeter sources in the UKIDSS Ultra Deep Survey (UDS) field. Using the available deep (especially near-infrared) panoramic imaging of the UDS field at optical-to-radio wavelengths we characterize key properties of the SMG population. The median photometric redshift of the bright ALMA/SCUBA-2 UDS (AS2UDS) SMGs that are detected in a sufficient number of wavebands to derive a robust photometric redshift is z=2.65+/-0.13. However, similar to previous studies, 27% of the SMGs are too faint at optical-to-near-infrared wavelengths to derive a reliable photometric redshift. Assuming that these SMGs lie at z>~3 raises the median redshift of the full sample to z=2.9+/-0.2. A subset of 23 unlensed, bright AS2UDS SMGs have sizes measured from resolved imaging of their rest- frame far-infrared emission. We show that the extent and luminosity of the far-infrared emission are consistent with the dust emission arising from regions that are, on average, optically thick at a wavelength of {lambda}_0_>=75{mu}m (1{sigma} dispersion of 55-90{mu}m). Using the dust masses derived from our optically thick spectral energy distribution models, we determine that these galaxies have a median hydrogen column density of N_H_=9.8_-0.7_^+1.4^x10^23^cm^-2^, or a corresponding median V-band obscuration of Av=540_-40_^+80^mag, averaged along the line of sight to the source of their rest-frame ~200{mu}m emission. We discuss the implications of this extreme attenuation by dust for the multi-wavelength study of dusty starbursts and reddening-sensitive tracers of star formation.
- ID:
- ivo://CDS.VizieR/J/A+A/608/A15
- Title:
- ALMA survey of submm galaxies in COSMOS field
- Short Name:
- J/A+A/608/A15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We carried out targeted ALMA observations of 129 fields in the COSMOS region at 1.25mm, detecting 152 galaxies at S/N>=5 with an average continuum RMS of 150 {mu}Jy. These fields represent a S/N-limited sample of AzTEC/ASTE sources with 1.1mm S/N>=4 over an area of 0.72 square degrees. Given ALMA's fine resolution and the exceptional spectroscopic and multiwavelength photometric data available in COSMOS, this survey allows us unprecedented power in identifying submillimeter galaxy counterparts and determining their redshifts through spectroscopic or photometric means. In addition to 30 sources with prior spectroscopic redshifts, we identified redshifts for 113 galaxies through photometric methods and an additional nine sources with lower limits, which allowed a statistically robust determination of the redshift distribution. We have resolved 33 AzTEC sources into multi-component systems and our redshifts suggest that nine are likely to be physically associated. Our overall redshift distribution peaks at z~2.0 with a high-redshift tail skewing the median redshift to z^~^=2.48+/-0.05. We find that brighter millimeter sources are preferentially found at higher redshifts. Our faintest sources, with S_1.25mm_<1.25mJy, have a median redshift of z^~^=2.18+/-0.09, while the brightest sources, S_1.25mm_>1.8mJy, have a median redshift of z^~^=3.08+/-0.17. After accounting for spectral energy distribution shape and selection effects, these results are consistent with several previous submillimeter galaxy surveys, and moreover, support the conclusion that the submillimeter galaxy redshift distribution is sensitive to survey depth.
- ID:
- ivo://CDS.VizieR/J/ApJ/812/43
- Title:
- ALMA 870um obs. of HerMES galaxies
- Short Name:
- J/ApJ/812/43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Herschel Multi-tiered Extragalactic Survey (HerMES, Oliver et al. 2012, VIII/95) has identified large numbers of dusty star-forming galaxies (DSFGs) over a wide range in redshift. A detailed understanding of these DSFGs is hampered by the limited spatial resolution of Herschel. We present 870{mu}m 0.45" resolution imaging obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) of a sample of 29 HerMES DSFGs that have far-infrared (FIR) flux densities that lie between the brightest of sources found by Herschel and fainter DSFGs found via ground-based surveys in the submillimeter region. The ALMA imaging reveals that these DSFGs comprise a total of 62 sources (down to the 5{sigma} point-source sensitivity limit in our ALMA sample; {sigma}~0.2mJy). Optical or near-infrared imaging indicates that 36 of the ALMA sources experience a significant flux boost from gravitational lensing ({mu}>1.1), but only six are strongly lensed and show multiple images. We introduce and make use of uvmcmcfit, a general-purpose and publicly available Markov chain Monte Carlo visibility-plane analysis tool to analyze the source properties. Combined with our previous work on brighter Herschel sources, the lens models presented here tentatively favor intrinsic number counts for DSFGs with a break near 8mJy at 880um and a steep fall-off at higher flux densities. Nearly 70% of the Herschel sources break down into multiple ALMA counterparts, consistent with previous research indicating that the multiplicity rate is high in bright sources discovered in single-dish submillimeter or FIR surveys. The ALMA counterparts to our Herschel targets are located significantly closer to each other than ALMA counterparts to sources found in the LABOCA ECDFS Submillimeter Survey. Theoretical models underpredict the excess number of sources with small separations seen in our ALMA sample. The high multiplicity rate and small projected separations between sources seen in our sample argue in favor of interactions and mergers plausibly driving both the prodigious emission from the brightest DSFGs as well as the sharp downturn above S880=8mJy.
- ID:
- ivo://CDS.VizieR/J/A+A/580/A113
- Title:
- A low-luminosity type-1 QSO sample. III.
- Short Name:
- J/A+A/580/A113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the optical spectroscopic analysis of a sample of 99 low-luminosity quasi-stellar objects (LLQSOs) at z<=0.06 base the Hamburg/ESO QSO Survey (HES). To better relate the low-redshift active galactic nucleus (AGN) to the QSO population it is important to study samples of the latter type at a level of detail similar to that of the low-redshift AGN. Powerful QSOs, however, are absent at low redshifts due to evolutionary effects and their small space density. Our understanding of the (distant) QSO population is, therefore, significantly limited by angular resolution and sensitivity. The LLQSOs presented here offer the possibility of studying the faint end of this population at smaller cosmological distances and, therefore, in greater detail. In comparing two spectroscopic methods, we aim to establish a reliable activity classification scheme of the LLQSOs sample. Our goal is to enrich our systematic multiwavelength analysis of the AGN/starburst relation in these systems and give a complementary information on this particular sample of LLQSOs from the Hamburg ESO survey. Here, we present results of the analysis of visible wavelength spectroscopy provided by the HES and the 6 Degree Field Galaxy Survey (6dFGS). These surveys use different spectroscopic techniques, long-slit and circular fiber, respectively. These allow us to assess the influence of different apertures on the activity of the LLQSOs using classical optical diagnostic diagrams. We perform a Gaussian fitting of strong optical emission lines and decompose narrow and broad Balmer components. A small number of our LLQSO present no broad component, which is likely to be present but buried in the noise. Two sources show double broad components, whereas six comply with the classic NLS1 requirements. As expected in NLR of broad line AGNs, the [SII]-based electron density values range between 100 and 1000N_e_/cm^3^. Using the optical characteristics of Populations A and B, we find that 50% of our sources with H{beta} broad emission are consistent with the radio-quiet sources definition. The remaining sources could be interpreted as low-luminosity radio-loud quasar. The BPT-based classification renders an AGN/Seyfert activity between 50 to 60%. For the remaining sources, the possible starburst contribution might control the LINER and HII classification. Finally, we discuss the aperture effect as responsible for the differences found between data sets, although variability in the BLR could play a significant role as well.
