- 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.
« Previous |
1 - 10 of 11
|
Next »
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/452/3969
- Title:
- ATCA Survey of Sagittarius B2 at 7mm
- Short Name:
- J/MNRAS/452/3969
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a 30-50GHz survey of Sagittarius B2(N) conducted with the Australia Telescope Compact Array (ATCA) with 5 - 10 arcsec resolution. We analyze the spectra towards three HII regions that have foreground molecular gas in Sgr B2. Towards the most line-dense region, we detect >500 spectral line components, >90% of which are assigned to H and He recombination lines and 53 firmly identified molecular species (not including isotopologues). The data reveal extremely subthermally excited molecular gas in Sgr B2 absorbing against the continuum background, as well as molecular line emission from two hot cores in Sgr B2(N). They also also contain line-of-sight absorption by ~15 molecules observed in translucent gas in the Galactic Center, bar, and intervening spiral arm clouds, revealing the complex chemistry and clumpy structure of this gas. Formamide (NH_2_CHO) is detected for the first time in a translucent cloud.
- ID:
- ivo://CDS.VizieR/V/112A
- Title:
- Catalog of Star-Forming Regions in the Galaxy
- Short Name:
- V/112A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This Catalog of Star-Forming Regions in the Galaxy contains coordinates and fluxes of young objects in the radio and infrared, as well as data on the radial velocities of recombination and molecular lines, for more than three thousand star-forming regions. In addition to photometric and kinematic data, we present information on diffuse and reflecting nebulae, dark and molecular clouds, and other objects related to young stars. The catalog consists of two parts. The main catalog lists star-forming regions in order of Galactic longitude and is supplemented by analogous information for star-forming regions in complexes of dark clouds with large angular sizes that are closest to the Sun. In our preliminary study of the catalog data using a formal classification of the star-forming regions, we subdivided these objects into several classes and characterized them as being populated primarily by massive or low-mass stars at early or late stages of the star-formation process. We also distinguish between relatively nearby and distant complexes.
- ID:
- ivo://CDS.VizieR/J/A+A/592/A54
- Title:
- Combined ArTeMiS+SPIRE 350um image of NGC6334
- Short Name:
- J/A+A/592/A54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Herschel observations of nearby molecular clouds suggest that interstellar filaments and prestellar cores represent two fundamental steps in the star formation process. The observations support a picture of low-mass star formation according to which filaments of ~0.1pc width form first in the cold interstellar medium, probably as a result of large-scale compression of interstellar matter by supersonic turbulent flows, and then prestellar cores arise from gravitational fragmentation of the densest filaments. Whether this scenario also applies to regions of high-mass star formation is an open question, in part because the resolution of Herschel is insufficient to resolve the inner width of filaments in the nearest regions of massive star formation. In an effort to characterize the inner width of filaments in high-mass star-forming regions, we imaged the central part of the NGC 6334 complex at a resolution higher by a factor of >3 than Herschel at 350microns. We used the large-format bolometer camera ArTeMiS on the APEX telescope and combined the high-resolution ArTeMiS data at 350microns with Herschel/HOBYS data at 70-500microns to ensure good sensitivity to a broad range of spatial scales. This allowed us to study the structure of the main narrow filament of the complex with a resolution of 8" or <0.07pc at d~1.7kpc. Our study confirms that this filament is a very dense, massive linear structure with a line mass ranging from ~500M_{sun}_/pc to ~2000M_{sun}_/pc over nearly 10pc. It also demonstrates for the first time that its inner width remains as narrow as W~0.15+/-0.05pc all along the filament length, within a factor of <2 of the characteristic 0.1pc value found with Herschel for lower-mass filaments in the Gould Belt. While it is not completely clear whether the NGC 6334 filament will form massive stars in the future, it is two to three orders of magnitude denser than the majority of filaments observed in Gould Belt clouds, and has a very similar inner width. This points to a common physical mechanism for setting the filament width and suggests that some important structural properties of nearby clouds also hold in high-mass star-forming regions.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A59
- Title:
- Fluctuations of UV background from GALEX
- Short Name:
- J/A+A/631/A59
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The all sky survey run by the Galaxy Evolution Explorer (GALEX AIS) mapped about 85 % of the Galaxy at ultraviolet (UV) wavelengths and detected the diffuse UV background produced by the scattering of the radiation from OBA stars by interstellar dust grains. Against this background, diffuse weak structures are detected as well as the UV counterparts to nebulae and molecular clouds. To make full profit of the survey, unsupervised and semi-supervised procedures need to be implemented. The main objective of this work is to implement and analyze the results of the method developed by us for the blind detection of ISM features in the GALEX AIS. Most ISM features are detected at very low signal levels (dark filaments, globules) against the already faint UV background. We have defined an index the UV background fluctuations index (or UBF index) to identify areas of the sky where these fluctuations are detected. The algorithm is applied to the images obtained in the FUV (1344-1786{AA}) band since this is less polluted by stellar sources, facilitating the automated detection. The UBF index is shown to be sensitive to the main star forming regions within the Gould's Belt, as well as to some prominent loops like Loop I or the Eridanus and Monogem areas. The catalogue with the UBF index values is made available on-line to the community.
- ID:
- ivo://CDS.VizieR/J/A+A/608/A133
- Title:
- Gas and dust in star-forming region rho OphA
- Short Name:
- J/A+A/608/A133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate to what degree local physical and chemical conditions are related to the evolutionary status of various objects in star-forming media. rho Oph A displays the entire sequence of low-mass star formation in a small volume of space. Using spectrophotometric line maps of H_2_, H_2_O, NH_3_, N_2_H^+^, O_2_, OI, CO, and CS, we examine the distribution of the atomic and molecular gas in this dense molecular core. The physical parameters of these species are derived, as are their relative abundances in rho Oph A. Using radiative transfer models, we examine the infall status of the cold dense cores from their resolved line profiles of the ground state lines of H_2_O and NH_3_, where for the latter no contamination from the VLA 1623 outflow is observed and line overlap of the hyperfine components is explicitly taken into account. The stratified structure of this photon dominated region (PDR), seen edge-on, is clearly displayed. Polycyclic aromatic hydrocarbons (PAHs) and OI are seen throughout the region around the exciting star S1. At the interface to the molecular core 0.05pc away, atomic hydrogen is rapidly converted into H_2_, whereas OI protrudes further into the molecular core. This provides oxygen atoms for the gas-phase formation of O_2_ in the core SM1, where X(O_2_)~5x10^-8^. There, the ratio of the O_2_ to H_2_O abundance [X(H_2_O)~5x10^-9^] is significantly higher than unity. Away from the core, O_2_ experiences a dramatic decrease due to increasing H_2_O formation. Outside the molecular core, on the far side as seen from S1, the intense radiation from the 0.5pc distant early B-type star HD147889 destroys the molecules. Towards the dark core SM1, the observed abundance ratio X(O_2_)/X(H_2_O)>1, which suggests that this object is extremely young, which would explain why O_2_ is such an elusive molecule outside the solar system.
- ID:
- ivo://CDS.VizieR/J/A+A/578/A131
- Title:
- Gas and dust in the star-forming region rho OphA
- Short Name:
- J/A+A/578/A131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using mapping observations of the very dense rho Oph A core, we examined standard 1D and non-standard 3D methods to analyse data of far-infrared and submillimeter continuum radiation. The resulting dust surface density distribution can be compared to that of the gas. The latter was derived from the analysis of accompanying molecular line emission, observed with Herschel from space and with APEX from the ground. As a gas tracer we used N_2_H^+^, which is believed to be much less sensitive to freeze-out than CO and its isotopologues. Radiative transfer modelling of the N_2_H^+^(J=3-2) and (J=6-5) lines with their hyperfine structure explicitly taken into account provides solutions for the spatial distribution of the column density N(H2), hence the surface density distribution of the gas. The gas-to-dust mass ratio is varying across the map, with very low values in the central regions around the core SM1. The global average, =88, is not far from the canonical value of 100, however. In rho Oph A, the exponent beta of the power-law description for the dust opacity exhibits a clear dependence on time, with high values of 2 for the envelope-dominated emission in starless Class-1 sources to low values close to 0 for the disk-dominated emission in ClassIII objects. beta assumes intermediate values for evolutionary classes in between. Since beta is primarily controlled by grain size, grain growth mostly occurs in circumstellar disks. The spatial segregation of gas and dust, seen in projection toward the core centre, probably implies that, like C^18^O, also N_2_H^+^ is frozen onto the grains.
- ID:
- ivo://CDS.VizieR/J/MNRAS/399/1506
- Title:
- IRDC cores in SCUBA Legacy Catalogue
- Short Name:
- J/MNRAS/399/1506
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an investigation of candidate infrared dark cloud (IRDC) cores as identified by Simon et al. (2006, Cat. J/ApJ/639/227) located within the Submillimetre Common User Bolometer Array (SCUBA) Legacy Catalogue. After applying a uniform noise cut to the catalogue data, we identify 154 IRDC cores that were detected at 850um and 51 cores that were not. We derive column densities for each core from their 8um extinction and find that the IRDCs detected at 850um have higher column densities (a mean of 1.7x10^22^cm^-2^) compared to those cores not detected at 850um (a mean of 1.0x10^22^cm-2).
- ID:
- ivo://CDS.VizieR/J/A+A/575/A9
- Title:
- M17-SW datacubes in C and CO lines
- Short Name:
- J/A+A/575/A9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We probe the column densities and masses traced by the ionized [CII] and neutral [CI] atomic carbon with spectrally resolved maps, and compare them to the diffuse and dense molecular gas traced by [CI] and low-J CO lines toward the star-forming region M17 SW. We mapped a 4.1pcx4.7pc region in the [CI] 609{mu}m line using the APEX telescope, as well as the CO isotopologues with the IRAM 30m telescope. Data are analyzed based on velocity channel maps that are 1km/s wide. We correlate their spatial distribution with that of the [CII] map obtained with SOFIA/GREAT. Optically thin approximations were used to estimate the column densities of [CI] and [CII] in each velocity channel.
- ID:
- ivo://CDS.VizieR/J/AJ/147/46
- Title:
- Properties of clumps in the NAN complex
- Short Name:
- J/AJ/147/46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present observations of a 4.25deg^2^ area toward the North American and Pelican Nebulae in the J=1-0 transitions of ^12^CO, ^13^CO, and C^18^O. Three molecules show different emission areas with their own distinct structures. These different density tracers reveal several dense clouds with a surface density of over 500M_{sun}_pc^-2^ and a mean H_2_ column density of 5.8, 3.4, and 11.9x10^21^/cm2 for ^12^CO, ^13^CO, and C^18^O, respectively. We obtain a total mass of 5.4x10^4^M_{sun}_(^12^CO), 2.0x10^4^M_{sun}_(^13^CO), and 6.1x10^3^M_{sun}_(C^18^O) in the complex. The distribution of excitation temperature shows two phases of gas: cold gas (~10K) spreads across the whole cloud; warm gas (>20K) outlines the edge of the cloud heated by the W80 HII region. The kinetic structure of the cloud indicates an expanding shell surrounding the ionized gas produced by the HII region. There are six discernible regions in the cloud: the Gulf of Mexico, Caribbean Islands and Sea, and Pelican's Beak, Hat, and Neck. The areas of ^13^CO emission range within 2-10pc^2^ with mass of (1-5)x10^3^M_{sun}_ and line width of a few km/s. The different line properties and signs of star-forming activity indicate they are in different evolutionary stages. Four filamentary structures with complicated velocity features are detected along the dark lane in LDN 935. Furthermore, a total of 611 molecular clumps within the ^13^CO tracing cloud are identified using the ClumpFind algorithm. The properties of the clumps suggest that most of the clumps are gravitationally bound and at an early stage of evolution with cold and dense molecular gas.
