- 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.
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Search Results
- ID:
- ivo://CDS.VizieR/B/iram
- Title:
- IRAM Observation Logs
- Short Name:
- B/iram
- Date:
- 04 Jan 2022 15:31:49
- Publisher:
- CDS
- Description:
- The Institut de Radio Astronomie Millimetrique (IRAM) was founded in 1979 and is operated as a French-German-Spanish collaboration. Its partner institutes are the CNRS (Centre National de la Recherche Scientifique, France), the MPG (Max Planck Gesellschaft, Germany), and the IGN (Instituto Geografico Nacional, Spain). The principal activity of IRAM is the study of cold matter (molecular gas and dust) in the solar system, in our Galaxy, and out to cosmological distances in order to determine its composition, density, mass, temperature, and kinematics. IRAM operates two observatories at millimeter wavelengths which are open to the international astronomical community: The 30-m single-dish telescope on Pico Veleta (2850m), Spain, and the six-antenna interferometer on the Plateau de Bure (2550m) in France. Both sites are at high altitude to reduce the absorption by water vapor. The observatories are supported by the IRAM offices and laboratories in Granada and Grenoble. The observation log included here concerns the Plateau de Bure site, and summarizes the observations made there from December 1990. The observations log of the 30-m single-dish telescope covers a period starting in January 2009. This log was produced using a header archive, a collaborative effort between IRAM and IAA/CSIC. NOEMA (NOrthern Extended Millimeter Array) is the successor to the Plateau du Bure observatory. During its history, the observatory at the Plateau de Bure underwent several track extensions, received additional antennas (all of 15m diameter and similar construction as the first ones) and technical upgrades. From a three antenna interferometer with a maximum baseline of 288 meters in 1988, it has evolved to a eight-antenna array with baselines up to 760 meters in 2016. With the inauguration of the seventh antenna in September 2014, the observatory has started its transformation into NOEMA.
- ID:
- ivo://CDS.VizieR/J/A+A/475/925
- Title:
- IRAS 05358+3543 (sub)mm maps
- Short Name:
- J/A+A/475/925
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the small-scale structure of massive star-forming regions through interferometric observations in several (sub)mm wavelength bands. We determine the kinetic temperature of the gas around the protostars, and derive the column density of several molecular species. For two of the protostars, constrains on the density are also inferred.
- ID:
- ivo://CDS.VizieR/J/A+A/529/A161
- Title:
- IRDC core G11.11-0.12P1 methanol maps
- Short Name:
- J/A+A/529/A161
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study with the Plateau de Bure Interferometer of a core in the archetypal filamentary IRDC G11.11-0.12 of a few arcsecond resolution to determine its physical and chemical structures. The data consist of continuum and line observations covering the C^34^S 2-1 line and the methanol 2_k_-1_k_ v_t_=0 lines at 3mm and the methanol 5_k_-4_k_ v_t_=0 lines at1mm. Our observations show extended emission in the continuum at 1 and 3mm. The methanol 2-1 emission has three maxima extending over a 1pc scale (when merged with single-dish short-spacing observations); one of the maxima is spatially coincident with the continuum emission. The fitting results show an enhanced methanol fractional abundance at the central peak with respect to the other two peaks, where it decreases by about an order of magnitude. Wings in the CH_3_OH 2-1 spectra, and CH_3_OH abundance enhancements point to the presence of an outflow in the east-west direction. In addition, we find a gradient of ~4km/s in the same direction, which we interpret as being produced by an outflow(s)-cloud interaction.
- ID:
- ivo://CDS.VizieR/J/ApJ/846/98
- Title:
- Jet kinematics of blazars at 43GHz with the VLBA
- Short Name:
- J/ApJ/846/98
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the parsec-scale jet kinematics from 2007 June to 2013 January of a sample of {gamma}-ray bright blazars monitored roughly monthly with the Very Long Baseline Array at 43GHz. In a total of 1929 images, we measure apparent speeds of 252 emission knots in 21 quasars, 12 BL Lacertae objects (BLLacs), and 3 radio galaxies, ranging from 0.02c to 78c; 21% of the knots are quasi-stationary. Approximately one-third of the moving knots execute non-ballistic motions, with the quasars exhibiting acceleration along the jet within 5pc (projected) of the core, and knots in BLLacs tending to decelerate near the core. Using the apparent speeds of the components and the timescales of variability from their light curves, we derive the physical parameters of 120 superluminal knots, including variability Doppler factors, Lorentz factors, and viewing angles. We estimate the half-opening angle of each jet based on the projected opening angle and scatter of intrinsic viewing angles of knots. We determine characteristic values of the physical parameters for each jet and active galactic nucleus class based on the range of values obtained for individual features. We calculate the intrinsic brightness temperatures of the cores, T_b,int_^core^, at all epochs, finding that the radio galaxies usually maintain equipartition conditions in the cores, while ~30% of T_b,int_^core^ measurements in the quasars and BLLacs deviate from equipartition values by a factor >10. This probably occurs during transient events connected with active states.
- ID:
- ivo://CDS.VizieR/II/300
- Title:
- JMMC Stellar Diameters Catalogue - JSDC
- Short Name:
- II/300
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalogue contains stellar angular diameter estimate for bright stars, complete for all stars with Hipparcos parallaxes. The JMMC Calibrator Workgroup has long developed methods to estimate the angular diameter of stars, and provides this expertise in the SearchCal software (http://www.jmmc.fr/searchcal). "SearchCal" creates a dynamical catalogue of stars suitable to calibrate Optical Long-Baseline Interferometry (OLBI) observations from on-line queries of CDS catalogues, according to observational parameters. In essence, SearchCal is limited only by the completeness of the stellar catalogues it uses, and in particular is not limited in magnitude. SearchCal being an application centered on OLBI peculiar purposes, it appeared useful to publish the estimated angular diameters of all stars with known parallaxes in a static catalogue. The present catalogue of stellar angular diameters has been obtained from an automated SearchCal results aggregation on the whole celestial sphere. For each star, the value of the limb-darkened angular diameters are computed using a surface brightness method and calibrations for (B-V), (V-R) and (V-K) color indexes. Stars whose angular diameters estimated from the various color indexes are not comparable, are rejected, and a reliable error on the estimated diameter is computed (1). For details of the method see Bonneau et al. (2006A&A...456..789B). To avoid specific confusion problems, spectroscopic binaries in the 9th Catalogue of Spectroscopic Binary Orbits (Pourbaix et al., 2009, Cat. B/sb9) or close visual binaries with a separation of less than 2 arc seconds in the Washington Visual Double Star Catalog (Mason et al., 2001, Cat. B/wds) have been filtered out.
- ID:
- ivo://CDS.VizieR/II/346
- Title:
- JMMC Stellar Diameters Catalogue - JSDC. Version 2
- Short Name:
- II/346
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalogue contains stellar angular diameter estimates for nearly all the stars of the Hipparcos and Tycho catalogue that have an associated spectral type in Simbad/CDS. The median error on the diameters is around 1.5%, with possible biases of around ~2%. For each object, the limb-darkened diameter retained is the mean value of several estimates performed using different couples of photometries. The chi-square representing the dispersion between these values is also given (it is below 2 for ~400000 stars). An additional flag signals stars that could represent a risk if chosen as calibrators for Optical Long-Baseline Interferometry, independently of the correctness of their apparent diameter estimate. This catalog replaces the catalog II/300/jsdc .
- ID:
- ivo://CDS.VizieR/J/ApJ/768/128
- Title:
- K-band calibrated visibilities of 24 Be stars
- Short Name:
- J/ApJ/768/128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on a high angular resolution survey of circumstellar disks around 24 northern sky Be stars. The K-band continuum survey was made using the CHARA Array long baseline interferometer (baselines of 30-331m). The interferometric visibilities were corrected for the flux contribution of stellar companions in those cases where the Be star is a member of a known binary or multiple system. For those targets with good (u, v) coverage, we used a four-parameter Gaussian elliptical disk model to fit the visibilities and to determine the axial ratio, position angle, K-band photospheric flux contribution, and angular diameter of the disk's major axis. For the other targets with relatively limited (u, v) coverage, we constrained the axial ratio, inclination angle, and/or disk position angle where necessary in order to resolve the degeneracy between possible model solutions. We also made fits of the ultraviolet and infrared spectral energy distributions (SEDs) to estimate the stellar angular diameter and infrared flux excess of each target. The mean ratio of the disk diameter (measured in K-band emission) to stellar diameter (from SED modeling) is 4.4 among the 14 cases where we reliably resolved the disk emission, a value which is generally lower than the disk size ratio measured in the higher opacity H{alpha} emission line. We estimated the equatorial rotational velocity from the projected rotational velocity and disk inclination for 12 stars, and most of these stars rotate close to or at the critical rotational velocity.
- ID:
- ivo://CDS.VizieR/J/A+A/636/A62
- Title:
- Light curves of 3C273 during 2015-2019
- Short Name:
- J/A+A/636/A62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The powerful radiation over the entire electromagnetic spectrum and its radio jet activity of the blazar 3C 273 offer the opportunity of studying the physics of {gamma}-ray emission from active galactic nuclei. Since the historically strong outburst in 2009, 3C 273 showed relatively weak emission in the {gamma}-ray band over several years. However, recent Fermi-Large Area Telescope observations indicate higher activity during 2015-2019. We constrain the origin of the {gamma}-ray outbursts toward 3C 273 and investigate their connection to the parsec-scale jet. We generated Fermi-LAT {gamma}-ray light curves with multiple binning intervals and studied the spectral properties of the {gamma}-ray emission. Using a 3mm ALMA light curve, we studied the correlation between radio and {gamma}-ray emission. The relevant activity in the parsec-scale jet of 3C 273 was investigated with 7 mm VLBA observations that were obtained close in time to notable {gamma}-ray outbursts. We find two prominent {gamma}-ray outbursts in 2016 (MJD 57382) and 2017 (MJD 57883) accompanied by millimeter-wavelength flaring activity. The {gamma}-ray photon index time series show a weak hump-like feature around the {gamma}-ray outbursts. The monthly {gamma}-ray flux-index plot indicates a transition from softer-when-brighter to harder-when-brighter states at 1.03x10^-7^ph/cm^2^/s. A significant correlation between the {gamma}-ray and millimeter-wavelength emission is found, and the radio lags the {gamma}-rays by about 105-112 days. The 43GHz jet images reveal the known stationary features (i.e., the core, S1, and S2) in a region upstream of the jet. We find an indication for a propagating disturbance and a polarized knot between the stationary components at about the times of the two {gamma}-ray outbursts. Our results support a parsec-scale origin for the observed higher {gamma}-ray activity, which suggests that this is associated with standing shocks in the jet.
- ID:
- ivo://CDS.VizieR/J/ApJ/813/39
- Title:
- LIGO gravitational-wave (GW) searches from SNRs
- Short Name:
- J/ApJ/813/39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe directed searches for continuous gravitational waves (GWs) in data from the sixth Laser Interferometer Gravitational-wave Observatory (LIGO) science data run. The targets were nine young supernova remnants not associated with pulsars; eight of the remnants are associated with non-pulsing suspected neutron stars. One target's parameters are uncertain enough to warrant two searches, for a total of 10. Each search covered a broad band of frequencies and first and second frequency derivatives for a fixed sky direction. The searches coherently integrated data from the two LIGO interferometers over time spans from 5.3-25.3 days using the matched-filtering F-statistic. We found no evidence of GW signals. We set 95% confidence upper limits as strong (low) as 4x10^-25^ on intrinsic strain, 2x10^-7^ on fiducial ellipticity, and 4x10^-5^ on r-mode amplitude. These beat the indirect limits from energy conservation and are within the range of theoretical predictions for neutron-star ellipticities and r-mode amplitudes.
