- ID:
- ivo://CDS.VizieR/J/A+A/632/A19
- Title:
- IRAM intensity maps of 3 low-mass protostars
- Short Name:
- J/A+A/632/A19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Methanol is a key species in astrochemistry since it is the most abundant organic molecule in the interstellar medium and is thought to be the mother molecule of many complex organic species. Estimating the deuteration of methanol around young protostars is of crucial importance because it highly depends on its formation mechanisms and the physical conditions during its moment of formation. We analyse several dozens of transitions from deuterated methanol isotopologues coming from various existing observational datasets obtained with the IRAM-PdBI and ALMA sub-mm interferometers to estimate the methanol deuteration surrounding three low-mass protostars on Solar System scales. A population diagram analysis allows us to derive a [CH_2_DOH]/[CH_3_OH] abundance ratio of 3-6% and a [CH_3_OD]/[CH_3_OH] ratio of 0.4-1.6% in the warm inner (<100-200AU) protostellar regions. These values are typically ten times lower than those derived with previous single-dish observations towards these sources but they are one to two orders of magnitude higher than the methanol deuteration measured in massive hot cores. Dust temperature maps obtained from Herschel and Planck observations show that massive hot cores are located in warmer molecular clouds than low-mass sources, with temperature differences of about 10K. The comparison of our measured values with the predictions of the gas-grain astrochemical model GRAINOBLE shows that such a temperature difference is sufficient to explain the different deuteration observed in low- to high-mass sources. This suggests that the physical conditions of the molecular cloud at the origin of the protostars mostly govern the present observed deuteration of methanol and, therefore, of more complex organic molecules. Finally, the methanol deuteration measured towards young solar-type protostars on Solar System scales seems to be higher by a factor of about 5 than the upper limit in methanol deuteration estimated in comet Hale-Bopp. If this result is confirmed by subsequent observations of other comets, this would imply that an important reprocessing of the organic material likely occurred in the solar nebula during the formation of the Solar System.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/II/125
- Title:
- IRAS catalogue of Point Sources, Version 2.0
- Short Name:
- II/125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is a catalog of some 250,000 well-confirmed infrared point sources observed by the Infrared Astronomical Satellite, i.e., sources with angular extents less than approximately 0.5, 0.5, 1.0, and 2.0 arcmin in the in-scan direction at 12, 25, 60, and 100 microns, respectively. Positions, flux densities, uncertainties, associations with known astronomical objects and various cautionary flags are given for each object. While two other complementary data sets - the Working Survey Data Base and a file of rejected sources - give information about point-like sources, the information available in the Point Source Catalog should satisfy almost all users. Away from confused regions of the sky, the survey is complete to about 0.4, 0.5, 0.6, and 1.0 Jy at 12, 25, 60, and 100 microns. Typical position uncertainties are about 2 to 6 arcseconds in-scan and about 8 to 16 arcseconds cross-scan. The processing steps applied to detect and confirm point sources, and the positional and photometric error analyses are described in the IRAS Catalogs and Atlases Explanatory Supplement; the catalog format is described in Chapter X. The sources appear in order of increasing (1950.0) right ascension. The included script "tofits.sh" should generate the FITS version of the tables on Unix platforms.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A137
- Title:
- IRAS 16293-2422 CH_3_CCH spectral cubes
- Short Name:
- J/A+A/631/A137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Propyne (CH_3_CCH) has been detected in a variety of environments, from Galactic star-forming regions to extragalactic sources. Such molecules are excellent tracers of the physical conditions in star-forming regions. This study explores the emission of CH_3_CCH in the low-mass protostellar binary, IRAS 16293-2422, examining the spatial scales traced by this molecule, as well as its formation and destruction pathways. ALMA observations from the Protostellar Interferometric Line Survey (PILS) are used to determine the abundances and excitation temperatures of CH_3_CCH towards both protostars, exploring spatial scales from 70 to 2400au. The three-phase chemical kinetics model MAGICKAL is also used, to explore the chemical reactions of this molecule. CH_3_CCH is detected towards both IRAS 16293A and IRAS 16293B and is found to trace the hot corino component around each source in the PILS dataset. Eighteen transitions above 3{sigma} are detected, enabling robust excitation temperatures and column densities to be determined in each source. In IRAS 16293A, an excitation temperature of 90K and a column density of 7.8x10^15^cm^-2^ best fits the spectra. In IRAS 16293B, an excitation temperature of 100K and 6.8x10^15^cm^-2^ best fits the spectra. The chemical modelling finds that in order to reproduce the observed abundances, both gas-phase and grain-surface reactions are needed. CH_3_CCH is a molecule whose brightness and abundance in many different regions can be utilised to provide a benchmark of molecular variation with the physical properties of star-forming regions. It is essential when making such comparisons, that the abundances are determined with a good understanding of the spatial scale of the emitting region, to ensure that accurate abundances are derived
- ID:
- ivo://CDS.VizieR/J/A+A/422/141
- Title:
- IRAS 08211-4158 cluster IR photometry
- Short Name:
- J/A+A/422/141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the astrometry and near infrared photometry (H, K, L, M) of the cluster associated with the star forming region IRAS 08211-4158 in the Vela Molecular Clouds. The observations were carried out with SofI at NTT (H, K) and ISAAC at VLT (L, M ).
- ID:
- ivo://CDS.VizieR/J/A+A/629/A8
- Title:
- IRAS 16342-3814 12CO (1-0) and (3-2) datacubes
- Short Name:
- J/A+A/629/A8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Water-fountain nebulae are asymptotic giant branch (AGB) and post-AGB objects that exhibit high-velocity outflows traced by water-maser emission. Their study is important for understanding the interaction between collimated jets and the circumstellar material that leads to the formation of bipolar and/or multi-polar morphologies in evolved stars. The aim of this paper is to describe the three-dimensional morphology and kinematics of the molecular gas of the water-fountain nebula IRAS 16342-3814. Data was retrieved from the ALMA archive for analysis using a simple spatio-kinematical model. The software SHAPE was employed to construct a three-dimensional, spatio-kinematical model of the molecular gas in IRAS 16342-3814, and to then reproduce the intensity distribution and position-velocity diagram of the CO emission from the ALMA observations to derive the morphology and velocity field of the gas. Data from CO(J=1->0) supported the physical interpretation of the model. A spatio-kinematical model that includes a high-velocity collimated outflow embedded within material expanding at relatively lower velocity reproduces the images and position-velocity diagrams from the observations. The derived morphology is in good agreement with previous results from IR and water-maser emission observations. The high-velocity collimated outflow exhibits deceleration across its length, while the velocity of the surrounding component increases with distance. The morphology of the emitting region, the velocity field, and the mass of the gas as function of velocity are in excellent agreement with the properties predicted for a molecular outflow driven by a jet. The timescale of the molecular outflow is estimated to be ~70-100yr. The scalar momentum carried by the outflow is much larger than it can be provided by the radiation of the central star. An oscillating pattern was found associated with the high-velocity collimated outflow. The oscillation period of the pattern is T~=60-90yr and its opening angle is {theta}_op_~=2{deg}. The CO (J=3->2) emission in IRAS 16342-3814 is interpreted in terms of a jet-driven molecular outflow expanding along an elongated region. The position-velocity diagram and the mass spectrum reveal a feature due to entrained material that is associated with the driving jet. This feature is not seen in other more evolved objects that exhibit more developed bipolar morphologies. It is likely that the jet in those objects has already disappeared since it is expected to last only for a couple hundred years. This strengthens the idea that water fountain nebulae are undergoing a very short transition during which they develop the collimated outflows that shape the circumstellar envelopes. The oscillating pattern seen in the CO high-velocity outflow is interpreted as due to precession with a relatively small opening angle. The precession period is compatible with the period of the corkscrew pattern seen at IR wavelengths. We propose that the high-velocity molecular outflow traces the underlying primary jet that produces such a pattern.
- ID:
- ivo://CDS.VizieR/J/A+A/642/L7
- Title:
- IRAS 04302+2247 CO, CS, CN, H2CO, CH3OH maps
- Short Name:
- J/A+A/642/L7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The chemical composition of planets is inherited from that of the natal protoplanetary disk at the time of planet formation. Increasing observational evidence suggests that planet formation occurs in less than 1-2Myr. This motivates the need for spatially resolved spectral observations of young Class I disks, as carried out by the ALMA chemical survey of Disk-Outflow sources in Taurus (ALMA-DOT). In the context of ALMA-DOT, we observe the edge-on disk around the Class I source IRAS 04302+2247 (the butterfly star) in the 1.3mm continuum and five molecular lines. We report the first tentative detection of methanol (CH_3_OH) in a Class I disk and resolve, for the first time, the vertical structure of a disk with multiple molecular tracers. The bulk of the emission in the CO 2-1, CS 5-4, and o-H_2_CO 3_1,2_-2_1,1_ lines originates from the warm molecular layer, with the line intensity peaking at increasing disk heights, z, for increasing radial distances, r. Molecular emission is vertically stratified, with CO observed at larger disk heights (aperture z/r~0.41-0.45) compared to both CS and H2CO, which are nearly cospatial (z/r~0.21-0.28). In the outer midplane, the line emission decreases due to molecular freeze-out onto dust grains (freeze-out layer) by a factor of >100 (CO) and 15 (CS). The H_2_CO emission decreases by a factor of only about 2, which is possibly due to H2CO formation on icy grains, followed by a nonthermal release into the gas phase. The inferred [CH_3_OH]/[H_2_CO] abundance ratio is 0.5-0.6, which is 1-2 orders of magnitude lower than for Class 0 hot corinos, and a factor ~2.5 lower than the only other value inferred for a protoplanetary disk (in TW Hya, 1.3-1.7). Additionally, it is at the lower edge but still consistent with the values in comets. This may indicate that some chemical reprocessing occurs in disks before the formation of planets and comets.
- ID:
- ivo://irsa.ipac/IRAS/Catalog/FSC
- Title:
- IRAS Faint Source Catalog
- Short Name:
- IRAS-FSC
- Date:
- 01 Oct 2018 20:27:21
- Publisher:
- NASA/IPAC Infrared Science Archive
- Description:
- The Faint Source Survey (FSS) is the definitive IRAS data set for faint point sources. The FSS was produced by point-source filtering the individual detector data streams and then coadding those data streams using a trimmed-average algorithm. The resulting images, or plates, give the best estimate from the IRAS survey data of the point source flux density at every surveyed point of the sky. The Faint Source Catalog (FSC) is a compilation of the sources extracted from the FSS plates that have met reasonable reliability requirements. Averaged over the whole catalog, the FSC is at least 98.5% reliable at 12 and 25 microns, and ~94% at 60 microns. For comparison, the IRAS Point Source Catalog (PSC) is > 99.997% reliable, but the sensitivity of the FSC exceeds that of the PSC by about a factor of 2.5. The FSC contains data for 173,044 point sources in unconfused regions with flux densities typically greater than 0.2 Jy at 12, 25, and 60 microns and greater than 1.0 Jy at 100 microns.
- ID:
- ivo://CDS.VizieR/II/156A
- Title:
- IRAS Faint Source Catalog, |b| > 10, Version 2.0
- Short Name:
- II/156A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Faint Source Survey (FSS) is the definitive Infrared Astronomical Satellite data set for faint point sources. The FSS was produced by point-source filtering the individual detector data streams and then coadding those data streams using a trimmed-average algorithm. The resulting images, or plates, give the best estimate from the IRAS survey data of the point source flux density at every surveyed point of the sky. The Faint Source Catalog (FSC) is a compilation of the sources extracted from the FSS plates that have met reasonable reliability requirements. Averaged over the whole catalog, the FSC is at least 98.5% reliable at 12 and 25 microns, and ~94% at 60 microns. For comparison, the IRAS Point Source Catalog (PSC) is >99.997% reliable, but the sensitivity of the FSC exceeds that of the PSC by about a factor of 2.5. The FSC contains data for 173,044 point sources in unconfused regions with flux densities typically above 0.2 Jy at 12, 25, and 60 microns, and above 1.0 Jy at 100 microns. The FSS plates are somewhat more sensitive but less reliable than the FSC; typically, only sources with SNR>5-6 in the plates are contained in the FSC. Sources with SNR>3 but which do not meet the reliability requirements of the FSC are catalogued in the Faint Source Reject File (FSR, Cat. II/275). The data products, the processing methods used to produce them, results of an analysis of these products, and cautionary notes are given in the Explanatory Supplement to the IRAS Faint Source Survey (see references in fsc.txt).
- ID:
- ivo://CDS.VizieR/II/275
- Title:
- IRAS Faint Source Reject Catalog
- Short Name:
- II/275
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Faint Source Reject Catalog contains 593,516 sources rejected for inclusion in the Faint Source Catalog (Cat. II/156) because they failed to meet one or more of the criteria established to ensure the reliability of the FSC. The REJECTED sources in the FSR are either in confused regions of the sky, or in areas with |b|<10-20{deg}, or were detected only in a single band with a signal-to-noise ratio of 3-6. The FSR also includes sources from areas of the sky covered by fewer than six detector passes, and sources contaminated by or caused by cometary debris trails. The files described here contain selected columns from the original Faint Source Reject IRAS catalogue; the full set is available as a ascii FITS table. In the descriptions below, the original names of the columns are added at the end of the explanations of each column.
- ID:
- ivo://CDS.VizieR/J/A+A/451/431
- Title:
- IRAS fluxes in LMC starburst regions
- Short Name:
- J/A+A/451/431
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Filamentary structures of early type stars are found to be a common feature of the Magellanic Clouds formed at an age of about 0.9-2x10^8^yr. As we go to younger ages these large structures appear fragmented and sooner or later form young clusters and associations. In the optical domain we have detected 56 such large structures of young objects, known as stellar complexes in the LMC for which we give coordinates and dimensions. We also investigate star formation activity and evolution of these stellar complexes and define the term "starburst region".
