- 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.
Number of results to display per page
Search Results
- 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/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/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/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/MNRAS/410/2662
- Title:
- AMI 1.8cm observations in c2d small clouds
- Short Name:
- J/MNRAS/410/2662
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We perform deep 1.8-cm radio continuum imaging towards 13 protostellar regions selected from the Spitzer c2d small clouds and cores programme at high resolution (25-arcsec) in order to detect and quantify the cm-wave emission from deeply embedded young protostars. Within these regions we detect 15 compact radio sources which we identify as radio protostars including two probable new detections. The sample is in general of low bolometric luminosity and contains several of the newly detected VeLLO sources. We determine the 1.8cm radio luminosity to bolometric luminosity correlation, L_rad_-L_bol_, for the sample and discuss the nature of the radio emission in terms of the available sources of ionized gas. We also investigate the Lrad-LIR correlation and suggest that radio flux density may be used as a proxy for the internal luminosity of low-luminosity protostars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/429/3330
- Title:
- AMI Galactic Plane Survey at 16GHz. I.
- Short Name:
- J/MNRAS/429/3330
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The AMI Galactic Plane survey is being made with the Arcminute Microkelvin Imager (AMI) Small Array at 15.7GHz and with resolution of approximately 3arcmin. This is the first data release, covering ~868deg^2^ of the Northern Galactic plane between |b|~+/-5{deg} and above {delta}=40{deg} with a noise level of ~3mJy/beam away from bright sources. The source catalogue contains a total of 3503 sources.
- ID:
- ivo://CDS.VizieR/J/MNRAS/453/1396
- Title:
- AMI Galactic Plane Survey at 16GHz. II.
- Short Name:
- J/MNRAS/453/1396
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Arcminute Microkelvin Imager Galactic Plane Survey (AMIGPS) provides mJy-sensitivity, arcminute-resolution interferometric images of the northern Galactic plane at ~16GHz. The first data release covered 76{deg}<=l<=170{deg} between latitudes of |b|<=5{deg}; here we present a second data release, extending the coverage to 53{deg}<=l<=193{deg} and including high-latitude extensions to cover the Taurus and California giant molecular cloud regions, and the recently discovered large supernova remnant G159.6+7.3. The total coverage is now 1777{deg}^2^ and the catalogue contains 6509 sources. We also describe the improvements to the data processing pipeline which improves the positional and flux density accuracies of the survey.