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1211. Orion B in 18 molecular tracers maps
ID:
ivo://CDS.VizieR/J/A+A/645/A27
Title:
Orion B in 18 molecular tracers maps
Short Name:
J/A+A/645/A27
Date:
21 Oct 2021
Publisher:
CDS
Description:
Molecular hydrogen being unobservable in cold molecular clouds, the column density measurements of molecular gas currently rely either on dust emission observation in the far-IR or on star counting. (Sub-)millimeter observations of numerous trace molecules are effective from ground based telescopes, but the relationships between the emission of one molecular line and the H_2_ column density (NH_2_) is non-linear and sensitive to excitation conditions, optical depths, abundance variations due to the underlying physico-chemistry. We aim to use multi-molecule line emission to infer NH_2_ from radio observations. We propose a data-driven approach to determine NH_2_ from radio molecular line observations. We use supervised machine learning methods (Random Forests) on wide-field hyperspectral IRAM-30m observations of the Orion B molecular cloud to train a predictor of NH_2_, using a limited set of molecular lines as input, and the Herschel-based dust-derived NH_2_ as ground truth output. For conditions similar to the Orion B molecular cloud, we obtain predictions of NH_2_ within a typical factor of 1.2 from the Herschel-based estimates. An analysis of the contributions of the different lines to the predictions show that the most important lines are ^13^CO(1-0), ^12^CO(1-0), C^18^O(1-0), and HCO+(1-0). A detailed analysis distinguishing between diffuse, translucent, filamentary, and dense core conditions show that the importance of these four lines depends on the regime, and that it is recommended to add the N_2_H+(1-0) and CH_3_OH(2_0_-1_0_) lines for the prediction of NH_2_ in dense core conditions. This article opens a promising avenue to directly infer important physical parameters from the molecular line emission in the millimeter domain. The next step will be to try to infer several parameters simultaneously (e.g., NH_2_ and far-UV illumination field) to further test the method.
1212. Orion-KL substructure at 1.3mm
ID:
ivo://CDS.VizieR/J/A+A/581/A71
Title:
Orion-KL substructure at 1.3mm
Short Name:
J/A+A/581/A71
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Kleinmann-Low nebula in Orion (Orion-KL) is the nearest example of a high-mass star-forming environment. For the first time, we complemented 1.3mm Submillimeter Array (SMA) interferometric line survey with IRAM 30m single-dish observations of the Orion-KL region. Covering a 4GHz bandwidth in total, this survey contains over 160 emission lines from 20 species (25 isotopologues), including 10 complex organic molecules (COMs). At a spatial resolution of 1200AU, the continuum substructures are resolved. Extracting the spectra from individual substructures and providing the intensity-integrated distribution map for each species, we studied the small-scale chemical variations in this region. Our main results are: (1) We identify lines from the low-abundance COMs CH3COCH3 and CH3CH2OH, as well as tentatively detect CH3CHO and long carbon-chains C6H and HC7N. (2) We find that while most COMs are segregated by type, peaking either towards the hot core (e.g., N-bearing species) or the compact ridge (e.g., O-bearing species like HCOOCH3, CH3OCH3, the distributions of others do not follow this segregated structure (e.g., CH3CH2OH, CH3OH, CH3COCH3). (3) We find a second velocity component of HNCO, 34SO2, and SO lines, which may be associated with a strong shock event in the low-velocity outflow. (4) Temperatures and molecular abundances show large gradients between central condensations and the outflow regions, illustrating a transition between hot molecular core and shock-chemistry dominated regimes. Our observations of spatially resolved chemical variations in Orion-KL provide the nearest reference source for hot molecular core and outflow chemistry, which will be an important example for interpreting the chemistry of more distant HMSFRs.
1213. Orion Source I 3mm SiO maser emission
ID:
ivo://CDS.VizieR/J/A+A/606/A126
Title:
Orion Source I 3mm SiO maser emission
Short Name:
J/A+A/606/A126
Date:
21 Oct 2021
Publisher:
CDS
Description:
High-mass star formation remains poorly understood due to observational difficulties (e.g. high dust extinction and large distances) hindering the resolution of disk-accretion and out ow-launching regions. Orion Source I is the closest known massive young stellar object (YSO) and exceptionally powers vibrationally excited SiO masers at radii within 100AU, providing a unique probe of gas dynamics and energetics. We seek to observe and image these masers with Very Long Baseline Interferometry (VLBI). We present the first images of the ^28^SiO v=1, J=2-1 maser emission around Orion Source I observed at ({lambda}2mm) with the Very Long Baseline Array (VLBA). These images have high spatial (~0.3mas) and spectral (~0.054km/s) resolutions.
1214. Outbursts of GX339-4 at 5.5 and 9.0GHz fluxes
ID:
ivo://CDS.VizieR/J/MNRAS/431/L107
Title:
Outbursts of GX339-4 at 5.5 and 9.0GHz fluxes
Short Name:
J/MNRAS/431/L107
Date:
21 Oct 2021
Publisher:
CDS
Description:
Galactic black hole binaries produce powerful outflows which emit over almost the entire electromagnetic spectrum. Here, we report the first detection with the Herschel observatory of a variable far-infrared source associated with the compact jets of the black hole transient GX 339-4 during the decay of its recent 2010-2011 outburst, after the transition to the hard state. We also outline the results of very sensitive radio observations conducted with the Australia Telescope Compact Array, along with a series of near-infrared, optical (OIR) and X-ray observations, allowing for the first time the re-ignition of the compact jets to be observed over a wide range of wavelengths. The compact jets first turn on at radio frequencies with an optically thin spectrum that later evolves to an optically thick synchrotron emission. An OIR reflare is observed about 10d after the onset of radio and hard X-ray emission, likely reflecting the necessary time to build up enough density, as well as to have acceleration (e.g. through shocks) along an extended region in the jets. The Herschel measurements are consistent with an extrapolation of the radio inverted power-law spectrum, but they highlight a more complex radio to OIR spectral energy distribution for the jets.
1215. Outer Galaxy IRAS sources and 12CO emission
ID:
ivo://CDS.VizieR/J/A+A/399/1083
Title:
Outer Galaxy IRAS sources and 12CO emission
Short Name:
J/A+A/399/1083
Date:
21 Oct 2021
Publisher:
CDS
Description:
We examined all of the IRAS sources within the Five College Radio Astronomy Observatory (FCRAO) Outer Galaxy Survey (OGS) region for associated ^12^CO emission (as accounted for in the Brunt, Kerton, and Pomerleau (2003, in press) catalogue of ^12^CO emission in the OGS). Table 1 provides a ranked listing of IRAS-CO associations and Table 2 provides a listing of those IRAS sources with no CO associations. In order to rank the various IRAS-CO associations we examined the association of random lines of sight with CO emission in the OGS. The resulting expectation numbers are provided to the reader in Table A1.
1216. Outer galaxy molecular cloud catalog
ID:
ivo://CDS.VizieR/J/ApJS/144/47
Title:
Outer galaxy molecular cloud catalog
Short Name:
J/ApJS/144/47
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Five College Radio Astronomy Observatory (FCRAO) Outer Galaxy Survey (OGS) of ^12^CO(J=1-0) emission was carried out between 1994May and 1997September, using the FCRAO focal plane array QUARRY (Erickson et al. 1992, IEEE Trans. 40, 1), and initially described by Heyer et al. (1998ApJS..115..241H). The OGS covers the Galactic area 102.5<l<141.5, -3<b<54, and the velocity range -152km/s<vlsr<40km/s, at 45'' spatial resolution sampled every 50.22'', and 0.98km/s velocity resolution (1.39km/s for l<106) sampled every 0.81km/s. The typical sensitivity of the OGS at these resolutions is 0.6K (T*_R_ temperature scale). The catalog was generated in a two-phase object identification procedure. The first phase consists of grouping pixels into contiguous structures above a radiation temperature threshold of 0.8K; the second phase decomposes the first-phase objects by an enhanced version of the CLUMPFIND algorithm, using dynamic thresholding, and again with a threshold of 0.8K used for discrimination. Basic attributes of the clouds (coordinates, bounding boxes, integrated intensities, peak observed temperatures) are tabulated in the catalog. A two-dimensional elliptical Gaussian is fitted to the velocity- integrated map of each cloud; the major and minor axis sizes and major axis position angles thus derived are included in the catalog. To the spatially integrated emission line of each cloud, a Gaussian profile is fitted to measure the global linewidth. Model Gaussian clouds, truncated at 0.8K, are examined to determine the effects of biases on measured quantities, induced by truncation. Coupled with detailed analysis of the catalogued clouds, statistical corrections for the effects of truncation on measured sizes, linewidths, and integrated intensities are derived and applied, along with corrections for the effects of finite resolution on the measured attributes. The catalogued emission accounts for 76.4% of the total emission in the Outer Galaxy Survey. The deficit is shown to arise mainly from low-intensity emission on the periphery of larger objects, rather than from a large number of small and/or low-intensity features.
1217. Outer galaxy VLA survey
ID:
ivo://CDS.VizieR/J/AJ/92/787
Title:
Outer galaxy VLA survey
Short Name:
J/AJ/92/787
Date:
21 Oct 2021
Publisher:
CDS
Description:
The VLA has been used to make a "snapshot" survey of all radio continuum sources stronger than 0.3Jy at 21cm, smaller than 2arcmin, and in the area in the sky defined by l=93{deg} to 163{deg}, b=-4{deg} to +4{deg}. These objects were observed at 6 cm with a resolution of 4 arcsec and a sensitivity of 1mJy. A second set of observations were carried out to determine the spectral indices of all objects not resolved in the 6 cm survey. These objects were observed at a wavelength of 2cm with resolution and sensitivity similar to the 6cm survey. The purpose of this study was to identify objects within the disk of the outer parts of our galaxy. It is shown that the current lists of identified H II regions in this area are better than ~70% complete for H II regions in the Perseus arm or closer. The only supernova remnants remaining to be discovered in this field are either extremely young, and therefore possibly radio quiet, or they are among those objects too extended to be observed at the VLA in this survey (i.e., greater than 2arcmin in diameter).
1218. Outflows and bubbles in Taurus
ID:
ivo://CDS.VizieR/J/ApJS/219/20
Title:
Outflows and bubbles in Taurus
Short Name:
J/ApJS/219/20
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have identified outflows and bubbles in the Taurus molecular cloud based on the ~100deg^2^ Five College Radio Astronomy Observatory ^12^CO(1-0) and ^13^CO(1-0) maps and the Spitzer young stellar object catalogs. In the main 44deg^2^ area of Taurus, we found 55 outflows, of which 31 were previously unknown. We also found 37 bubbles in the entire 100deg^2^ area of Taurus, none of which had been found previously. The total kinetic energy of the identified outflows is estimated to be ~3.9x10^45^erg, which is 1% of the cloud turbulent energy. The total kinetic energy of the detected bubbles is estimated to be ~9.2x10^46^erg, which is 29% of the turbulent energy of Taurus. The energy injection rate from the outflows is ~1.3x10^33^erg/s, which is 0.4-2 times the dissipation rate of the cloud turbulence. The energy injection rate from bubbles is ~6.4x10^33^erg/s, which is 2-10 times the turbulent dissipation rate of the cloud. The gravitational binding energy of the cloud is ~1.5x10^48^erg, that is, 385 and 16 times the energy of outflows and bubbles, respectively. We conclude that neither outflows nor bubbles can provide sufficient energy to balance the overall gravitational binding energy and the turbulent energy of Taurus. However, in the current epoch, stellar feedback is sufficient to maintain the observed turbulence in Taurus.
1219. 4 oxygen-rich evolved stars NH3 spectra
ID:
ivo://CDS.VizieR/J/A+A/612/A48
Title:
4 oxygen-rich evolved stars NH3 spectra
Short Name:
J/A+A/612/A48
Date:
21 Oct 2021
Publisher:
CDS
Description:
The circumstellar ammonia (NH_3_) chemistry in evolved stars is poorly understood. Previous observations and modelling showed that NH_3_ abundance in oxygen-rich stars is several orders of magnitude above that predicted by equilibrium chemistry. We would like to characterise the spatial distribution and excitation of NH_3_ in the oxygen-rich circumstellar envelopes (CSEs) of four diverse targets: IK Tau, VY CMa, OH 231.8+4.2, and IRC +10420. We observed NH_3_ emission from the ground state in the inversion transitions near 1.3cm with the Very Large Array (VLA) and submillimetre rotational transitions with the Heterodyne Instrument for the Far-Infrared (HIFI) aboard Herschel Space Observatory from all four targets. For IK Tau and VY CMa, we observed NH_3_ rovibrational absorption lines in 2 band near 10.5um with the Texas Echelon Cross Echelle Spectrograph (TEXES) at the NASA Infrared Telescope Facility (IRTF).We also attempted to search for the rotational transition within the excited vibrational state (v_2_=1) near 2mm with the IRAM 30m Telescope. Non-LTE radiative transfer modelling, including radiative pumping to the vibrational state, was carried out to derive the radial distribution of NH_3_ in the CSEs of these targets. We detected NH_3_ inversion and rotational emission in all four targets. IK Tau and VY CMa show blueshifted absorption in the rovibrational spectra. We did not detect vibrationally excited rotational transition from IK Tau. Spatially resolved VLA images of IK Tau and IRC +10420 show clumpy emission structures; unresolved images of VY CMa and OH 231.8+4.2 indicate that the spatial-kinematic distribution of NH_3_ is similar to that of assorted molecules, such as SO and SO2, that exhibit localised and clumpy emission. Our modelling shows that the NH_3_ abundance relative to molecular hydrogen is generally of the order of 10^-7^, which is a few times lower than previous estimates that were made without considering radiative pumping and is at least ten times higher than that in the carbon-rich CSE of IRC +10216. NH_3_ in OH 231.8+4.2 and IRC +10420 is found to emit in gas denser than the ambient medium. Incidentally, we also derived a new period of IK Tau from its V-band light curve. NH_3_ is again detected in very high abundance in evolved stars, especially the oxygen-rich ones. Its emission mainly arises from localised spatial-kinematic structures that are probably denser than the ambient gas. Circumstellar shocks in the accelerated wind may contribute to the production of NH_3_. Future mid-infrared spectroscopy and radio imaging studies are necessary to constrain the radii and physical conditions of the formation regions of NH_3_.
1220. Parallaxes of high mass star forming regions
ID:
ivo://CDS.VizieR/J/ApJ/783/130
Title:
Parallaxes of high mass star forming regions
Short Name:
J/ApJ/783/130
Date:
21 Oct 2021
Publisher:
CDS
Description:
Over 100 trigonometric parallaxes and proper motions for masers associated with young, high-mass stars have been measured with the Bar and Spiral Structure Legacy Survey, a Very Long Baseline Array key science project, the European VLBI Network, and the Japanese VLBI Exploration of Radio Astrometry project. These measurements provide strong evidence for the existence of spiral arms in the Milky Way, accurately locating many arm segments and yielding spiral pitch angles ranging from about 7{deg} to 20{deg}. The widths of spiral arms increase with distance from the Galactic center. Fitting axially symmetric models of the Milky Way with the three-dimensional position and velocity information and conservative priors for the solar and average source peculiar motions, we estimate the distance to the Galactic center, R_0_, to be 8.34+/-0.16kpc, a circular rotation speed at the Sun, {Theta}_0_, to be 240+/-8km/s, and a rotation curve that is nearly flat (i.e., a slope of -0.2+/-0.4km/s/kpc) between Galactocentric radii of {approx}5 and 16kpc. Assuming a "universal" spiral galaxy form for the rotation curve, we estimate the thin disk scale length to be 2.44+/-0.16kpc. With this large data set, the parameters R_0_ and {Theta}_0_are no longer highly correlated and are relatively insensitive to different forms of the rotation curve. If one adopts a theoretically motivated prior that high-mass star forming regions are in nearly circular Galactic orbits, we estimate a global solar motion component in the direction of Galactic rotation, V_{sun}_=14.6+/-5.0km/s. While {Theta}_0_and V_{sun}_are significantly correlated, the sum of these parameters is well constrained, {Theta}_0_+V_{sun}_=255.2+/-5.1km/s, as is the angular speed of the Sun in its orbit about the Galactic center, ({Theta}_0_+V_{sun}_)/R_0_=30.57+/-0.43km/s/kpc. These parameters improve the accuracy of estimates of the accelerations of the Sun and the Hulse-Taylor binary pulsar in their Galactic orbits, significantly reducing the uncertainty in tests of gravitational radiation predicted by general relativity.