- ID:
- ivo://CDS.VizieR/J/A+A/617/A31
- Title:
- HCO+, CN, and 13CO maps of R Mon
- Short Name:
- J/A+A/617/A31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To our knowledge, R Mon is the only B0 star in which a gaseous Keplerian disk has been detected. However, there is some controversy about the spectral type of R Mon. Some authors propose that it could be a later B8e star, where disks are more common. Our goal is to re-evaluate the R Mon spectral type and characterize its protoplanetary disk. The spectral type of R Mon has been re-evaluated using the available continuum data and UVES emission lines. We used a power-law disk model to fit previous ^12^CO 1-0 and 2-1 interferometric observations and the PACS CO data to investigate the disk structure. Interferometric detections of ^13^CO J=1-0, HCO^+^ 1-0, and CN 1-0 lines using the IRAM Plateau de Bure Interferometer (PdBI) are presented. The HCN 1-0 line was not detected. Our analysis confirms that R Mon is a B0 star. The disk model compatible with the ^12^CO 1-0 and 2-1 interferometric observations falls short of predicting the observed fluxes of the 14<Ju<31 PACS lines; this is consistent with the scenario in which some contribution to these lines is coming from a warm envelope and/or UV-illuminated outflow walls. More interestingly, the upper limits to the fluxes of the Ju>31 CO lines suggest the existence of a region empty of CO at R<=20au in the proto-planetary disk. The intense emission of the HCO^+^ and CN lines shows the strong influence of UV photons on gas chemistry. The observations gathered in this paper are consistent with the presence of a transition disk with a cavity of Rin>=20 au around R Mon. This size is similar to the photoevaporation radius that supports the interpretation that UV photoevaporation is main disk dispersal mechanism in massive stars
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/874/172
- Title:
- H_2_CO & H110{alpha} obs. toward Aquila
- Short Name:
- J/ApJ/874/172
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The formaldehyde H_2_CO(1_10_-1_11_) absorption line and H110{alpha} radio recombination line have been observed toward the Aquila Molecular Cloud using the Nanshan 25m telescope operated by the Xinjiang Astronomical Observatory CAS. These first observations of the H_2_CO (1_10_-1_11_) absorption line determine the extent of the molecular regions that are affected by the ongoing star formation in the Aquila molecular complex and show some of the dynamic properties. The distribution of the excitation temperature Tex for H_2_CO identifies the two known star formation regions W40 and Serpens South as well as a smaller new region Serpens 3. The intensity and velocity distributions of H_2_CO and ^13^CO(1-0) do not agree well with each other, which confirms that the H_2_CO absorption structure is mostly determined by the excitation of the molecules resulting from the star formation rather than by the availability of molecular material as represented by the distribution. Some velocity-coherent linear ^13^CO(1-0) structures have been identified in velocity channel maps of H2CO and it is found that the three star formation regions lie on the intersect points of filaments. The H110{alpha} emission is found only at the location of the W40 HII region and spectral profile indicates a redshifted spherical outflow structure in the outskirts of the HII region. Sensitive mapping of H_2_CO absorption of the Aquila Complex has correctly identified the locations of star formation activity in complex molecular clouds and the spectral profiles reveal the dominant velocity components and may identify the presence of outflows.
- ID:
- ivo://CDS.VizieR/J/A+A/605/A21
- Title:
- H_2_CO production in HD 163296
- Short Name:
- J/A+A/605/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the radial distribution of H_2_CO and C^18^O in the protoplanetary disk around HD 163296, a Herbig Ae type protostar, with the aim of determining possible formation scenarios of H_2_CO. By comparing the two molecules and the millimeter continuum, we investigate the relationship between the presence of H_2_CO and CO depletion in the disk.
- ID:
- ivo://CDS.VizieR/J/ApJS/234/21
- Title:
- hCOSMOS: Hectospec survey of galaxies in COSMOS
- Short Name:
- J/ApJS/234/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the hCOSMOS redshift survey of the COSMOS field conducted with the Hectospec spectrograph on the MMT. In the central 1deg^2^, the hCOS20.6 subset of the survey is >90% complete to a limiting magnitude r=20.6. The hCOSMOS survey includes 1701 new redshifts in the COSMOS field. We also use the total of 4362 new and remeasured objects to derive the age-sensitive D_n_4000 index over the entire redshift interval 0.001<~z<~0.6. For 85% of the quiescent galaxies in hCOS20.6, we measure the central line-of-sight velocity dispersion. To explore potential uses of this survey, we combine previously measured galaxy sizes, profiles, and stellar masses with the spectroscopy. The comparison reveals the known relations among structural, kinematic, and stellar population properties. We also compare redshift and D_n_4000 distributions of hCOS20.6 galaxies with SHELS; a complete spectroscopic survey of 4deg^2^ observed to the same depth. The redshift distributions in the two fields are very different, but the D_n_4000 distribution is remarkably similar. The relation between velocity dispersion and stellar mass for massive hCOS20.6 galaxies is consistent with the local relation from the Sloan Digital Sky Survey. Using measured velocity dispersions, we test a photometric proxy calibrated to galaxies in the local universe. The systematic differences between the measured and photometric proxy velocity dispersions are correlated with galaxy dynamical and stellar population properties highlighting the importance of direct spectroscopic measurements.
- ID:
- ivo://CDS.VizieR/J/ApJ/877/154
- Title:
- H_2_CO TMRT obs. of Galactic molecular clouds
- Short Name:
- J/ApJ/877/154
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present observations of the C-band 1_10_-1_11_ (4.8GHz) and Ku-band 2_11_-2_12_ (14.5GHz) K-doublet lines of H_2_CO and the C-band 1_10_-1_11_ (4.6GHz) line of H_2_^13^CO toward a large sample of Galactic molecular clouds, through the Shanghai Tianma 65m radio telescope (TMRT). Our sample with 112 sources includes strong H_2_CO sources from the TMRT molecular line survey at C-band and other known H_2_CO sources. All three lines are detected toward 38 objects (43 radial velocity components) yielding a detection rate of 34%. Complementary observations of their continuum emission at both C- and Ku-bands were performed. Combining spectral line parameters and continuum data, we calculate the column densities, the optical depths and the isotope ratio H_2_^12^CO/H_2_^13^CO for each source. To evaluate photon trapping caused by sometimes significant opacities in the main isotopologue's rotational mm-wave lines connecting our measured K-doublets, and to obtain ^12^C/^13^C abundance ratios, we used the RADEX non-LTE model accounting for radiative transfer effects. This implied the use of the new collision rates from Wiesenfeld & Faure. Also implementing distance values from trigonometric parallax measurements for our sources, we obtain a linear fit of ^12^C/^13^C=(5.08+/-1.10)D_GC_+(11.86+/-6.60), with a correlation coefficient of 0.58. D_GC_ refers to Galactocentric distances. Our ^12^C/^13^C ratios agree very well with the ones deduced from CN and C^18^O but are lower than those previously reported on the basis of H_2_CO, tending to suggest that the bulk of the H_2_CO in our sources was formed on dust grain mantles and not in the gas phase.
- ID:
- ivo://CDS.VizieR/J/A+A/624/A33
- Title:
- HD 100453 AB system ALMA images
- Short Name:
- J/A+A/624/A33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The complex system HD 100453 AB with a ring-like circumprimary disk and two spiral arms, one of which is pointing to the secondary, is a good laboratory in which to test spiral formation theories. We aim to resolve the dust and gas distribution in the disk around HD 100453 A and to quantify the interaction of HD 100453 B with the circumprimary disk. Using ALMA band 6 dust continuum and CO isotopologue observations we have studied the HD 100453 AB system with a spatial resolution of 0.09"x0.17" at 234GHz. We used smoothed particle hydrodynamics (SPH) simulations and orbital fitting to investigate the tidal influence of the companion on the disk. We resolve the continuum emission around HD 100453 A into a disk between 0.22" and 0.40" with an inclination of 29.5{deg} and a position angle of 151.0{deg}, an unresolved inner disk, and excess mm emission cospatial with the northern spiral arm which was previously detected using scattered light observations. We also detect CO emission from 7au (well within the disk cavity) out to 1.10", overlapping with HD 100453 B at least in projection. The outer CO disk position angle (PA) and inclination dier by up to 10{deg} from the values found for the inner CO disk and the dust continuum emission, which we interpret as due to gravitational interaction with HD 100453 B. Both the spatial extent of the CO disk and the detection of mm emission at the same location as the northern spiral arm are in disagreement with the previously proposed near co-planar orbit of HD 100453 B. We conclude that HD 100453 B has an orbit that is significantly misaligned with the circumprimary disk. Because it is unclear whether such an orbit can explain the observed system geometry we highlight an alternative scenario that explains all detected disk features where another, (yet) undetected, low mass close companion within the disk cavity, shepherds a misaligned inner disk whose slowly precessing shadows excite the spiral arms.
- ID:
- ivo://CDS.VizieR/J/A+A/597/A137
- Title:
- HD 123999 and Alpha Cen A and B OIFITS files
- Short Name:
- J/A+A/597/A137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The photospheric radius is one of the fundamental parameters governing the radiative equilibrium of a star. We report new observations of the nearest solar-type stars Alpha Centauri A (G2V) and B (K1V) with the VLTI/PIONIER optical interferometer. The combination of four configurations of the VLTI enable us to measure simultaneously the limb darkened angular diameter thetaLD and the limb darkening parameters of the two solar-type stars in the near-infrared H band (lambda=1.65um). We obtain photospheric angular diameters of {theta}_LD(A)_=8.502+/-0.038mas (0.43%) and {theta}_LD(B)_=5.999+/-0.025mas (0.42%), through the adjustment of a power law limb darkening model. We find H band power law exponents of {alpha}_(A)_=0.1404+/-0.0050 (3.6%) and {alpha}_(B)_=0.1545+/-0.0044 (2.8%), which closely bracket the observed solar value (alpha_{sun}_=0.15027). Combined with the parallax pi=747.17+/-0.61mas determined by Kervella et al. (2016), we derive linear radii of R_A_=1.2234+/-0.0053R_{sun}_ (0.43%) and R_B_=0.8632+/-0.0037R_{sun}_ (0.43%). The power law exponents that we derive for the two stars indicate a significantly weaker limb darkening than predicted by both 1D and 3D stellar atmosphere models. As this discrepancy is also observed on the near-infrared limb darkening profile of the Sun, an improvement of the calibration of stellar atmosphere models is clearly needed. The reported PIONIER visibility measurements of Alpha Cen A and B provide a robust basis to validate the future evolutions of these models.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A94
- Title:
- HD141569A system ALMA and NOEMA data cubes
- Short Name:
- J/A+A/635/A94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The study of gas-rich debris discs is fundamental to characterising the transition between protoplanetary discs and debris discs. Aims. We determine the physical parameters of the brightest gas-rich debris disc orbiting HD 141569A. We analyse images from the NOrthern Extended Millimeter Array (NOEMA) and the Atacama Large Millimeter/submillimeter Array (ALMA) in ^12^CO, ^13^CO J=2-1, and ^13^CO J=1-0 transitions. We incorporate ALMA archival data of the ^12^CO J=3-2 transition and present continuum maps at 0.87mm, 1.3mm, and 2.8mm. We use simple parametric laws with the Diskfit code and MCMC exploration to characterise the gas disc parameters and report a first attempt to characterise its chemical content with IRAM-30m. The continuum emission is equally shared between a compact (<50au) and a smooth, extended dust component (~350 au). Large millimetre grains seem to dominate the inner regions, while the dust spectral index is marginally larger in the outer region. The ^12^CO is optically thick, while ^13^CO is optically thin with tau_13CO_~0.15 (C^18^O is not detected). The ^13^CO surface density is constrained to be one order of magnitude smaller than around younger Herbig Ae stars, and we derive a gas mass M_12CO_=10^-1^M_{sun}_. We confirm the presence of a small CO cavity (R_CO_=17+/-3au), and find a possibly larger radius for the optically thin ^13^CO J=2-1 transition (35+/-5au). We show that the observed CO brightness asymmetry is coincident with the complex ring structures discovered with VLT/SPHERE in the inner 90au. The ^12^CO temperature T_0_(100au)~30K is lower than expected for a Herbig~A0 star, and could be indicative of subthermal excitation. With the largest amount of dust and gas among hybrid discs, HD141569A shows coincident characteristics of both protoplanetary discs (central regions), and debris discs at large distance. Together with its morphological characteristics and young age, it appears to be a good candidate to witness the transient phase of gas dissipation, with an apparently large gas-to-dust ratio (G/D>100) favouring a faster evolution of dust grains.
- ID:
- ivo://CDS.VizieR/J/A+A/622/A96
- Title:
- HD142527B images with SPHERE
- Short Name:
- J/A+A/622/A96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- HD142527 observations were performed with SPHERE in the IRDIFS_EXT mode, with IRDIS observing in dual-band imaging with the K12 filter pair (wavelength K1=2.110 micron; K2=2.251 micron), while IFS obtains low-resolution (R=30) spectra between 0.95 and 1.65 micron. HD142527 was also observed in the SAM mode for SPHERE (we present the first observations that ever used the sparse aperture mask in SPHERE). We detect the accreting low-mass companion HD142527B at a separation of 73mas (11.4au) from the star.
- ID:
- ivo://CDS.VizieR/J/A+A/633/A154
- Title:
- HDBSCAN star, galaxy, QSO classification
- Short Name:
- J/A+A/633/A154
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Classification will be an important first step for upcoming surveys that will detect billions of new sources such as LSST and Euclid, as well as DESI, 4MOST and MOONS. The application of traditional methods of model fitting and colour-colour selections will face significant computational constraints, while machine-learning (ML) methods offer a viable approach to tackle datasets of that volume. While supervised learning methods can perform very well for classification tasks, the creation of representative and accurate training sets is a resource and time consuming task. We present a viable alternative using an unsupervised ML method to separate stars, galaxies and QSOs using photometric data. The heart of our work uses HDBSCAN to find the star, galaxy and QSO clusters in a multidimensional colour space. We optimized the hyperparameters and input attributes of three separate HDBSCAN runs, each to select a particular object class, and thus treat the output of each separate run as a binary classifier. We subsequently consolidate the output to give our final classifications, optimized on their F1 scores. We explore the use of Random Forest and PCA as part of the pre-processing stage for feature selection and dimensionality reduction. Using our dataset of ~50000 spectroscopically labelled objects we obtain an F1 score of 98.9, 98.9 and 93.13 respectively for star, galaxy and QSO selection using our unsupervised learning method. We find that careful attribute selection is a vital part of accurate classification with HDBSCAN. We applied our classification to a subset of the SDSS spectroscopic catalogue and demonstrate the potential of our approach in correcting misclassified spectra useful for DESI and 4MOST. Finally, we create a multiwavelength catalogue of 2.7 million sources using the KiDS, VIKING and ALLWISE surveys and publish corresponding classifications and photometric redshifts.