- ID:
- ivo://CDS.VizieR/J/ApJ/842/L9
- Title:
- ALMA obs. of polarized dust emission from Ser-emb 8
- Short Name:
- J/ApJ/842/L9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report Atacama Large Millimeter/submillimeter Array (ALMA) observations of polarized dust emission from the protostellar source Ser-emb 8 at a linear resolution of 140au. Assuming models of dust-grain alignment hold, the observed polarization pattern gives a projected view of the magnetic field structure in this source. Contrary to expectations based on models of strongly magnetized star formation, the magnetic field in Ser-emb 8 does not exhibit an hourglass morphology. Combining the new ALMA data with previous observational studies, we can connect magnetic field structure from protostellar core (~80000au) to disk (~100au) scales. We compare our observations with four magnetohydrodynamic gravo-turbulence simulations made with the AREPO code that have initial conditions ranging from super-Alfvenic (weakly magnetized) to sub-Alfvenic (strongly magnetized). These simulations achieve the spatial dynamic range necessary to resolve the collapse of protostars from the parsec scale of star-forming clouds down to the ~100au scale probed by ALMA. Only in the very strongly magnetized simulation do we see both the preservation of the field direction from cloud to disk scales and an hourglass-shaped field at <1000au scales. We conduct an analysis of the relative orientation of the magnetic field and the density structure in both the Ser-emb 8 ALMA observations and the synthetic observations of the four AREPO simulations. We conclude that the Ser-emb 8 data are most similar to the weakly magnetized simulations, which exhibit random alignment, in contrast to the strongly magnetized simulation, where the magnetic field plays a role in shaping the density structure in the source. In the weak-field case, it is turbulence-not the magnetic field-that shapes the material that forms the protostar, highlighting the dominant role that turbulence can play across many orders of magnitude in spatial scale.
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- ID:
- ivo://CDS.VizieR/J/ApJ/883/129
- Title:
- ALMA obs. of star-forming regions toward NGC6334I
- Short Name:
- J/ApJ/883/129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The relative column densities of the structural isomers methyl formate, glycolaldehyde, and acetic acid are derived for a dozen positions toward the massive star-forming regions MM1 and MM2 in the NGC 6334I complex, which are separated by ~4000au. Relative column densities of these molecules are also gathered from the literature for 13 other star-forming regions. In this combined data set, a clear bimodal distribution is observed in the relative column densities of glycolaldehyde and methyl formate. No such distribution is evident with acetic acid. The two trends are comprised of star-forming regions with a variety of masses, suggesting that there must be some other common parameter that is heavily impacting the formation of glycolaldehyde. This is indicative of some demonstrable differentiation in these cores; studying the abundances of these isomers may provide a clue as to the integral chemical processes ongoing in a variety of protostellar environments.
- 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/886/102
- Title:
- ALMA obs. of 70um dark high-mass clumps (ASHES)
- Short Name:
- J/ApJ/886/102
- Date:
- 08 Mar 2022 13:24:32
- Publisher:
- CDS
- Description:
- The ALMA Survey of 70{mu}m dark High-mass clumps in Early Stages (ASHES) is designed to systematically characterize the earliest stages and constrain theories of high-mass star formation. Twelve massive (>500M_{sun}_), cold (<=15K), 3.6-70{mu}m dark prestellar clump candidates, embedded in infrared dark clouds, were carefully selected in the pilot survey to be observed with the Atacama Large Millimeter/submillimeter Array (ALMA). We have mosaicked each clump (~1arcmin^2^) in continuum and line emission with the 12m, 7m, and Total Power (TP) arrays at 224GHz (1.34mm), resulting in ~1.2" resolution (~4800au, at the average source distance). As the first paper in the series, we concentrate on the continuum emission to reveal clump fragmentation. We detect 294 cores, from which 84 (29%) are categorized as protostellar based on outflow activity or "warm core" line emission. The remaining 210 (71%) are considered prestellar core candidates. The number of detected cores is independent of the mass sensitivity range of the observations and, on average, more massive clumps tend to form more cores. We find a large population of low-mass (<1M_{sun}_) cores and no high-mass (>30M_{sun}_) prestellar cores (maximum mass 11M_{sun}_). From the prestellar core mass function, we derive a power-law index of 1.17+/-0.10, which is slightly shallower than Salpeter. We used the minimum spanning tree (MST) technique to characterize the separation between cores and their spatial distribution, and to derive mass segregation ratios. While there is a range of core masses and separations detected in the sample, the mean separation and mass per clump are well explained by thermal Jeans fragmentation and are inconsistent with turbulent Jeans fragmentation. Core spatial distribution is well described by hierarchical subclustering rather than centrally peaked clustering. There is no conclusive evidence of mass segregation. We test several theoretical conditions and conclude that overall, competitive accretion and global hierarchical collapse scenarios are favored over the turbulent core accretion scenario.
- ID:
- ivo://CDS.VizieR/J/ApJ/903/145
- Title:
- ALMaQUEST. IV. ALMA-MaNGA QUEnching & star formation
- Short Name:
- J/ApJ/903/145
- Date:
- 15 Mar 2022
- Publisher:
- CDS
- Description:
- The ALMaQUEST (ALMA-MaNGA QUEnching and STar formation) survey is a program with spatially resolved 12CO(1-0) measurements obtained with the Atacama Large Millimeter Array (ALMA) for 46 galaxies selected from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) DR15 optical integral-field spectroscopic survey. The aim of the ALMaQUEST survey is to investigate the dependence of star formation activity on the cold molecular gas content at kiloparsec scales in nearby galaxies. The sample consists of galaxies spanning a wide range in specific star formation rate (sSFR), including starburst (SB), main-sequence (MS), and green valley (GV) galaxies. In this paper, we present the sample selection and characteristics of the ALMA observations and showcase some of the key results enabled by the combination of spatially matched stellar populations and gas measurements. Considering the global (aperture-matched) stellar mass, molecular gas mass, and star formation rate of the sample, we find that the sSFR depends on both the star formation efficiency (SFE) and the molecular gas fraction (f_H_2__), although the correlation with the latter is slightly weaker. Furthermore, the dependence of sSFR on the molecular gas content (SFE or f_H_2__) is stronger than that on either the atomic gas fraction or the molecular-to-atomic gas fraction, albeit with the small Hi sample size. On kiloparsec scales, the variations in both SFE and f_H_2__ within individual galaxies can be as large as 1-2dex, thereby demonstrating that the availability of spatially resolved observations is essential to understand the details of both star formation and quenching processes.
- 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/ApJ/828/46
- Title:
- ALMA survey of Lupus protoplanetary disks. I.
- Short Name:
- J/ApJ/828/46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first high-resolution sub-millimeter survey of both dust and gas for a large population of protoplanetary disks. Characterizing fundamental properties of protoplanetary disks on a statistical level is critical to understanding how disks evolve into the diverse exoplanet population. We use the Atacama Large Millimeter/Submillimeter Array (ALMA) to survey 89 protoplanetary disks around stars with M*>0.1M_{sun}_ in the young (1-3Myr), nearby (150-200pc) Lupus complex. Our observations cover the 890{mu}m continuum and the ^13^CO and C^18^O 3-2 lines. We use the sub-millimeter continuum to constrain M_dust_ to a few Martian masses (0.2-0.4M_{Earth}_) and the CO isotopologue lines to constrain M_gas_ to roughly a Jupiter mass (assuming an interstellar medium (ISM)-like [CO]/[H_2_] abundance). Of 89 sources, we detect 62 in continuum, 36 in ^13^CO, and 11 in C^18^O at >3{sigma} significance. Stacking individually undetected sources limits their average dust mass to <~6 Lunar masses (0.03M_{Earth}_), indicating rapid evolution once disk clearing begins. We find a positive correlation between M_dust_ and M*, and present the first evidence for a positive correlation between M_gas_ and M*, which may explain the dependence of giant planet frequency on host star mass. The mean dust mass in Lupus is 3x higher than in Upper Sco, while the dust mass distributions in Lupus and Taurus are statistically indistinguishable. Most detected disks have M_gas_<~1M_Jup_ and gas-to-dust ratios <100, assuming an ISM-like [CO]/[H_2_] abundance; unless CO is very depleted, the inferred gas depletion indicates that planet formation is well underway by a few Myr and may explain the unexpected prevalence of super-Earths in the exoplanet population.
- ID:
- ivo://CDS.VizieR/J/ApJ/859/21
- Title:
- ALMA survey of Lupus protoplanetary disks. II.
- Short Name:
- J/ApJ/859/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Atacama Large Millimeter/Sub-Millimeter Array (ALMA) Band 6 observations of a complete sample of protoplanetary disks in the young (~1-3Myr) Lupus star-forming region, covering the 1.33mm continuum and the ^12^CO, ^13^CO, and C^18^O J=2-1 lines. The spatial resolution is ~0.25" with a medium 3{sigma} continuum sensitivity of 0.30mJy, corresponding to Mdust ~0.2M_{Earth}_. We apply Keplerian masking to enhance the signal-to-noise ratios of our ^12^CO zero-moment maps, enabling measurements of gas disk radii for 22 Lupus disks; we find that gas disks are universally larger than millimeter dust disks by a factor of two on average, likely due to a combination of the optically thick gas emission and the growth and inward drift of the dust. Using the gas disk radii, we calculate the dimensionless viscosity parameter, {alpha}_visc_, finding a broad distribution and no correlations with other disk or stellar parameters, suggesting that viscous processes have not yet established quasi-steady states in Lupus disks. By combining our 1.33mm continuum fluxes with our previous 890{mu}m continuum observations, we also calculate the millimeter spectral index, {alpha}_mm_, for 70 Lupus disks; we find an anticorrelation between {alpha}_mm_ and millimeter flux for low-mass disks (M_dust_<~5), followed by a flattening as disks approach {alpha}_mm_~2, which could indicate faster grain growth in higher-mass disks, but may also reflect their larger optically thick components. In sum, this work demonstrates the continuous stream of new insights into disk evolution and planet formation that can be gleaned from unbiased ALMA disk surveys.
- ID:
- ivo://CDS.VizieR/J/ApJS/251/20
- Title:
- ALMA survey of Orion PGCCs (ALMASOP). II. 1.3mm
- Short Name:
- J/ApJS/251/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Planck Galactic Cold Clumps (PGCCs) are considered to be the ideal targets to probe the early phases of star formation. We have conducted a survey of 72 young dense cores inside PGCCs in the Orion complex with the Atacama Large Millimeter/submillimeter Array (ALMA) at 1.3mm (band 6) using three different configurations (resolutions ~0.35", 1.0", and 7.0") to statistically investigate their evolutionary stages and substructures. We have obtained images of the 1.3mm continuum and molecular line emission (^12^CO, and SiO) at an angular resolution of ~0.35" (~140au) with the combined arrays. We find 70 substructures within 48 detected dense cores with median dust mass ~0.093M_{sun}_ and deconvolved size ~0.27". Dense substructures are clearly detected within the central 1000au of four candidate prestellar cores. The sizes and masses of the substructures in continuum emission are found to be significantly reduced with protostellar evolution from Class 0 to Class I. We also study the evolutionary change in the outflow characteristics through the course of protostellar mass accretion. A total of 37 sources exhibit CO outflows, and 20 (>50%) show high-velocity jets in SiO. The CO velocity extents ({Delta}Vs) span from 4 to 110km/s with outflow cavity opening angle width at 400au ranging from [{Theta}_obs_]_400_~0.6"-3.9", which corresponds to 33.4{deg}-125.7{deg}. For the majority of the outflow sources, the {Delta}Vs show a positive correlation with [{Theta}_obs_]_400_, suggesting that as protostars undergo gravitational collapse, the cavity opening of a protostellar outflow widens and the protostars possibly generate more energetic outflows.
