- 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.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/153/240
- Title:
- ALMA survey of protoplanetary disks in sigma Ori
- Short Name:
- J/AJ/153/240
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The {sigma} Orionis cluster is important for studying protoplanetary disk evolution, as its intermediate age (~3-5Myr) is comparable to the median disk lifetime. We use ALMA to conduct a high-sensitivity survey of dust and gas in 92 protoplanetary disks around {sigma} Orionis members with M_*_>~0.1M_{Sun}_. Our observations cover the 1.33mm continuum and several CO J=2-1 lines: out of 92 sources, we detect 37 in the millimeter continuum and 6 in ^12^CO, 3 in ^13^CO, and none in C^18^O. Using the continuum emission to estimate dust mass, we find only 11 disks with M_dust_>~10M_{Earth}_, indicating that after only a few Myr of evolution most disks lack sufficient dust to form giant planet cores. Stacking the individually undetected continuum sources limits their average dust mass to 5x lower than that of the faintest detected disk, supporting theoretical models that indicate rapid dissipation once disk clearing begins. Comparing the protoplanetary disk population in {sigma} Orionis to those of other star-forming regions supports the steady decline in average dust mass and the steepening of the M_dust_-M_*_ relation with age; studying these evolutionary trends can inform the relative importance of different disk processes during key eras of planet formation. External photoevaporation from the central O9 star is influencing disk evolution throughout the region: dust masses clearly decline with decreasing separation from the photoionizing source, and the handful of CO detections exist at projected separations of >1.5pc. Collectively, our findings indicate that giant planet formation is inherently rare and/or well underway by a few Myr of age.
- 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/A+A/641/L2
- Title:
- ALMA third image of lensed quasar PKS 1830-211
- Short Name:
- J/A+A/641/L2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Strong gravitational lensing distorts our view of sources at cosmological distances but brings invaluable constraints on the mass content of foreground objects and on the geometry and properties of the Universe. We report the detection of a third continuum source toward the strongly lensed quasar PKS 1830-211 in ALMA multi-frequency observations of high dynamic range and high angular resolution. This third source is point-like and located slightly to the north of the diagonal joining the two main lensed images, A and B, 0.3" away from image B. It has a flux density that is 140 times weaker than images A and B and a similar spectral index, compatible with synchrotron emission. We conclude that this source is most likely the expected highly de-magnified third lensed image of the quasar. In addition, we detect, for the first time at millimeter wavelengths, weak and asymmetrical extensions departing from images A and B that correspond to the brightest regions of the Einstein ring seen at centimeter wavelengths. Their spectral index is steeper than that of compact images A, B, and C, which suggests that they arise from a different component of the quasar. Using the GravLens code, we explore the implications of our findings on the lensing model and propose a simple model that accurately reproduces our ALMA data and previous VLA observations. With a more precise and accurate measurement of the time delay between images A and B, the system PKS 1830-211 could help to constrain the Hubble constant to a precision of a few percent.
- 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/618/A164
- Title:
- ALMA viewing of OH 231.8+4.2
- Short Name:
- J/A+A/618/A164
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present continuum and molecular line emission ALMA observations of OH 231.8+4.2, a well studied bipolar nebula around an asymptotic giant branch (AGB) star. The high angular resolution (~0.2"-0.3") and sensitivity of our ALMA maps provide the most detailed and accurate description of the overall nebular structure and kinematics of this object to date. We have identified a number of outflow components previously unknown. Species studied in this work include ^12^CO, ^13^CO, CS, SO, SO_2_, OCS, SiO, SiS, H_3_O^+^, Na^37^Cl, and CH_3_OH. The molecules Na^37^Cl and CH_3_OH are first detections in OH 231.8+4.2, with CH_3_OH being also a first detection in an AGB star.
- ID:
- ivo://CDS.VizieR/J/A+A/603/A10
- Title:
- ALMA view of G351.77-0.54
- Short Name:
- J/A+A/603/A10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The fragmentation of high-mass gas clumps and the formation of the accompanying accretion disks lie at the heart of high-mass star formation research. We resolve the small-scale structure around the high-mass hot core G351.77-0.54 to investigate its disk and fragmentation properties. Using the Atacama Large Millimeter Array at 690GHz with baselines exceeding 1.5km, we study the dense gas, dust, and outflow emission at an unprecedented spatial resolution of 0.06" (130AU at 2.2kpc). Within the inner few 1000AU, G351.77 is fragmenting into at least four cores (brightness temperatures between 58 and 201K). The central structure around the main submm source #1 with a diameter of ~0.5" does not show additional fragmentation. While the CO(6-5) line wing emission shows an outflow lobe in the northwestern direction emanating from source #1, the dense gas tracer CH_3_CN shows a velocity gradient perpendicular to the outflow that is indicative of rotational motions. Absorption profile measurements against the submm source #2 indicate infall rates on the order of 10^-4^ to 10^-3^M_{sun}_/yr, which can be considered as an upper limit of the mean accretion rates. The position-velocity diagrams are consistent with a central rotating disk-like structure embedded in an infalling envelope, but they may also be influenced by the outflow. Using the CH_3_CN(37k-36k) k-ladder with excitation temperatures up to 1300K, we derive a gas temperature map for source #1 exhibiting temperatures often in excess of 1000K. Brightness temperatures of the submm continuum barely exceed 200K. This discrepancy between gas temperatures and submm dust brightness temperatures (in the optically thick limit) indicates that the dust may trace the disk mid-plane, whereas the gas could trace a hotter gaseous disk surface layer. We conduct a pixel-by-pixel Toomre gravitational stability analysis of the central rotating structure. The derived high Q values throughout the structure confirm that this central region appears stable against gravitational instability. Resolving for the first time a high-mass hot core at 0.06 resolution at submm wavelengths in the dense gas and dust emission allowed us to trace the fragmenting core and the gravitationally stable inner rotating disk-like structure. A temperature analysis reveals hot gas and comparably colder dust that may be attributed to different disk locations traced by dust emission and gas lines. The kinematics of the central structure #1 reveal contributions from a rotating disk, an infalling envelope, and potentially an outflow as well, whereas the spectral profile toward source #2 can be attributed to infall.
- ID:
- ivo://CDS.VizieR/J/ApJ/857/19
- Title:
- ALMA view of GMCs in NGC 300
- Short Name:
- J/ApJ/857/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted a ^12^CO(2-1) survey of several molecular gas complexes in the vicinity of HII regions within the spiral galaxy NGC300 using the Atacama Large Millimeter Array (ALMA). Our observations attain a resolution of 10pc and 1km/s, sufficient to fully resolve giant molecular clouds (GMCs) and the highest obtained to date beyond the Local Group. We use the CPROPS algorithm to identify and characterize 250 GMCs across the observed regions. GMCs in NGC300 appear qualitatively and quantitatively similar to those in the Milky Way disk: they show an identical scaling relationship between size R and linewidth {Delta}V ({Delta}V{propto}R^0.48+/-0.05^), appear to be mostly in virial equilibrium, and are consistent with having a constant surface density of about 60M_{sun}_/pc^2^. The GMC mass spectrum is similar to those in the inner disks of spiral galaxies (including the Milky Way). Our results suggest that global galactic properties such as total stellar mass, morphology, and average metallicity may not play a major role in setting GMC properties, at least within the disks of galaxies on the star-forming main sequence. Instead, GMC properties may be more strongly influenced by local environmental factors such as the midplane disk pressure. In particular, in the inner disk of NGC 300, we find this pressure to be similar to that in the local Milky Way but markedly lower than that in the disk of M51, where GMCs are characterized by systematically higher surface densities and a higher coefficient for the size-linewidth relation.
- ID:
- ivo://CDS.VizieR/J/A+A/659/A20
- Title:
- 2A0335+096 LOFAR images
- Short Name:
- J/A+A/659/A20
- Date:
- 04 Mar 2022 06:16:07
- Publisher:
- CDS
- Description:
- Radio observations represent a powerful probe of the physics occurring in the intracluster medium (ICM) because they trace the relativistic cosmic rays in the cluster magnetic fields, or within galaxies themselves. By probing the low-energy cosmic rays, low-frequency radio observations are especially interesting because they unveil emission powered by low-efficiency particle acceleration processes, which are believed to play a crucial role in the origin of diffuse radio emission. We investigate the origin of the radio mini-halo at the center of the galaxy cluster 2A0335+096 and its connection to the central galaxy and the sloshing cool core. We also study the properties of the head-tail galaxy GB6 B0335+096 hosted in the cluster to explore the lifecycle of the relativistic electrons in its radio tails. We use new LOw Frequency ARray (LOFAR) observations from the LOFAR Two-meter Sky Survey at 144MHz to map the low-frequency emission with a high level of detail. The new data were combined with archival Giant Metrewave Radio Telescope and Chandra observations to carry out a multi-wavelength study. We have made the first measurement of the spectral index of the mini-halo ({alpha}=-1.2+/-0.1 between 144MHz and 1.4GHz) and the lobes of the central source ({alpha}=~-1.5+/-0.1 between 144 and 610MHz). Based on the low-frequency radio emission morphology with respect to the thermal ICM, we propose that the origin of the diffuse radio emission is linked to the sloshing of the cool core. The new data revealed the presence of a Mpc-long radio tail associated with GB6 B0335+096. The observed projected length is a factor 3 longer than the expected cooling length, with evidence of flattening in the spectral index trend along the tail. Therefore, we suggest that the electrons toward the end of the tail are kept alive by the ICM gentle re-acceleration.
- ID:
- ivo://CDS.VizieR/J/A+A/658/A167
- Title:
- (Al2O3)n, n=1-10, clusters data
- Short Name:
- J/A+A/658/A167
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Aluminium oxide (alumina; Al_2_O_3_) is a promising candidate as a primary dust condensate in the atmospheres of oxygen-rich evolved stars. Therefore, alumina 'seed' particles might trigger the onset of stellar dust formation and of stellar mass loss in the wind. However, the formation of alumina dust grains is not well understood. Aims. We aim to shed light on the initial steps of cosmic dust formation (i.e. nucleation) in oxygen-rich environments via a quantum- chemical bottom-up approach. Starting with an elemental gas-phase composition, we construct a detailed chemical-kinetic network that describes the formation and destruction of aluminium-bearing molecules and dust- forming (Al_2_O_3_)_n_ clusters up to the size of dimers (n=2) coagulating to tetramers (n=4). Intermediary species include the prevalent gas- phase molecules AlO and AlOH as well as Al_x_O_y_ clusters with x=1-5, y=1-6. The resulting extensive network is applied to two model stars, which represent a semi-regular variable and a Mira type, and to different circumstellar gas trajectories, including a non-pulsating outflow and a pulsating model. The growth of larger-sized (Al_2_O_3_)_n_ clusters with n=4-10 is described by the temperature-dependent Gibbs free energies of the most favourable structures (i.e. the global minima clusters) as derived from global optimisation techniques and calculated via density functional theory. We provide energies, bond characteristics, electrostatic properties, and vibrational spectra of the clusters as a function of size, n, and compare these to corundum, which corresponds to the crystalline bulk limit (n to infinity). The circumstellar aluminium gas-phase chemistry in oxygen- rich giants is primarily controlled by AlOH and AlO, which are tightly coupled by the reactions AlO+H_2_, AlO+H_2_O, and their reverse. Models of semi-regular variables show comparatively higher AlO abundances, as well as a later onset and a lower efficiency of alumina cluster formation when compared to Mira-like models. The Mira-like models exhibit an efficient cluster production that accounts for more than 90% of the available aluminium content, which is in agreement with the most recent ALMA observations. Chemical equilibrium calculations fail to predict both the alumina cluster formation and the abundance trends of AlO and AlOH in the asymptotic giant branch dust formation zone. Furthermore, we report the discovery of hitherto unreported global minimum candidates and low-energy isomers for cluster sizes n=7, 9, and 10. A homogeneous nucleation scenario, where Al2O3 monomers are successively added, is energetically viable. However, the formation of the Al2O3 monomer itself represents an energetic bottleneck. Therefore, we provide a bottom-up interpolation of the cluster characteristics towards the bulk limit by excluding the monomer, approximately following an n^(-1/3)^ dependence.
