- ID:
- ivo://CDS.VizieR/J/ApJ/688/L83
- Title:
- Detection of C_5_N^-^ in IRC +10216
- Short Name:
- J/ApJ/688/L83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the detection in the envelope of the C-rich star IRC+10216 of four series of lines with harmonically related frequencies: B1389, B1390, B1394, and B1401. The four series must arise from linear molecules with mass and size close to those of C_6_H and C_5_N. Three of the series have half-integer rotational quantum numbers; we assign them to the ^2^{Delta} and ^2^{Sigma}^-^ vibronic states of C_6_H in its lowest ({nu}_11_) bending mode. The fourth series, B1389, has integer J with no evidence of fine or hyperfine structure; it has a rotational constant of 1388.860(2)MHz and a centrifugal distortion constant of 33(1)Hz; it is almost certainly the C_5_N^-^ anion.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/585/A36
- Title:
- Deuterated water in prestellar cores
- Short Name:
- J/A+A/585/A36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on new APEX observations of the ground state 1_0,1_-0_0,0_ HDO transition at 464.92452GHz toward the prestellar core L1544. The line is undetected and we present an extensive study on the conditions for its detectability in cold and dense cloud cores. The water and deuterated water abundances have been estimated using an advanced chemical model simplified for the limited number of reactions or processes that are active in cold regions (<15K). We use the LIME radiative transfer code to compute the expected intensity and profile of both H_2_O and HDO lines and compare them with the observations. We present several ad hoc profiles that best-fit the observations and compare the profiles with results from an astrochemical modeling, coupling gas phase and grain surface chemistry. Our comparison between observations, radiative transfer and chemical modeling shows the limits of detectability for singly deuterated water with single-dish telescopes as well as interferometric observations.
- ID:
- ivo://CDS.VizieR/J/MNRAS/329/227
- Title:
- 2dF Galaxy Redshift Survey. II.
- Short Name:
- J/MNRAS/329/227
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have cross-matched the 1.4-GHz NRAO VLA Sky Survey (NVSS, Condon 1998, Cat. <VIII/65>) with the first 210 fields observed in the 2dF Galaxy Redshift Survey (2dFGRS, Colless, 2001, Cat. <VII/226>), covering an effective area of 325{deg}^2^ (about 20 per cent of the final 2dFGRS area). This yields a set of optical spectra of 912 candidate NVSS counterparts, of which we identify 757 as genuine radio identifications - the largest and most homogeneous set of radio source spectra ever obtained. The 2dFGRS radio sources span the redshift range z=0.005 to 0.438, and are a mixture of active galaxies (60 per cent) and star-forming galaxies (40 per cent). About 25 per cent of the 2dFGRS radio sources are spatially resolved by NVSS, and the sample includes three giant radio galaxies with projected linear size greater than 1 Mpc. The high quality of the 2dF spectra means we can usually distinguish unambiguously between AGN and star-forming galaxies. We make a new determination of the local radio luminosity function at 1.4 GHz for both active and star-forming galaxies, and derive a local star formation density of 0.022+/-0.004M_{sun}_/yr/Mpc^3^ (H_0_=50km/s/Mpc)
- ID:
- ivo://CDS.VizieR/J/A+A/636/A65
- Title:
- DG Tau B ALMA observations
- Short Name:
- J/A+A/636/A65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The chemical composition of planets is determined by the distribution of the various molecular species in the protoplanetary disk at the time of their formation. To date, only a handful of disks have been imaged in multiple spectral lines with high spatial resolution. As part of a small campaign devoted to the chemical characterization of disk-outflow sources in Taurus, we report on new ALMA Band 6 (1.3mm) observations with 0.15" (20au) resolution toward the embedded young star DG Tau B. Images of the continuum emission reveals a dust disk with rings and, putatively, a leading spiral arm. The disk, as well as the prominent outflow cavities, are detected in CO, H_2_CO, CS, and CN; instead, they remain undetected in SO_2_, HDO, and CH_3_OH. From the absorption of the back-side outflow, we inferred that the disk emission is optically thick in the inner 50au. This morphology explains why no line emission is detected from this inner region and poses some limitations toward the calculation of the dust mass and the characterization of the inner gaseous disk. The H_2_CO and CS emission from the inner 200au is mostly from the disk, and their morphology is very similar. The CN emission significantly differs from the other two molecules as it is observed only beyond 150au. This ring-like morphology is consistent with previous observations and the predictions of thermochemical disk models. Finally, we constrained the disk-integrated column density of all molecules. In particular, we found that the CH_3_OH/H_2_CO ratio must be smaller than ~2, making the methanol non-detection still consistent with the only such ratio available from the literature (1.27 in TW Hya).
- ID:
- ivo://CDS.VizieR/J/ApJ/734/98
- Title:
- DISCS. II. Southern sky disk data
- Short Name:
- J/ApJ/734/98
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the second in a series of papers based on data from DISCS, a Submillimeter Array observing program aimed at spatially and spectrally resolving the chemical composition of 12 protoplanetary disks. We present data on six Southern sky sources -IM Lup, SAO 206462 (HD 135344b), HD 142527, AS 209, AS 205, and V4046 Sgr- which complement the six sources in the Taurus star-forming region reported previously. CO 2-1 and HCO^+^ 3-2 emission are detected and resolved in all disks and show velocity patterns consistent with Keplerian rotation. Where detected, the emission from DCO^+^ 3-2, N_2_H^+^ 3-2, H_2_CO 3_0 3_-2_0 2_ and 4_1 4_-3_1 3_, HCN 3-2, and CN 2_3 3/4/2_-1_2 2/3/1_ are also generally spatially resolved. The detection rates are highest toward the M and K stars, while the F star SAO 206462 has only weak CN and HCN emission, and H2CO alone is detected toward HD 142527.
- ID:
- ivo://CDS.VizieR/J/ApJ/720/480
- Title:
- DISCS. I. Taurus protoplanetary disk data
- Short Name:
- J/ApJ/720/480
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Chemistry plays an important role in the structure and evolution of protoplanetary disks, with implications for the composition of comets and planets. This is the first of a series of papers based on data from DISCS (Disk Imaging Survey of Chemistry with SMA), a Submillimeter Array survey of the chemical composition of protoplanetary disks. The six Taurus sources in the program (DM Tau, AA Tau, LkCa 15, GM Aur, CQ Tau, and MWC 480) range in stellar spectral type from M1 to A4 and offer an opportunity to test the effects of stellar luminosity on the disk chemistry. The disks were observed in 10 different lines at ~3" resolution and an rms of ~100mJy/beam at ~0.5km/s.
- ID:
- ivo://CDS.VizieR/J/A+A/469/173
- Title:
- Dissipative structures of diffuse molecular gas
- Short Name:
- J/A+A/469/173
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- These maps are part of a large project aimed at analyzing the small scale morphology and velocity structure of the parsec-scale environment of a low mass dense core. The Polaris field is translucent and shows no signpost of star formation, therefore allowing an analysis of a purely turbulent field prior to star formation. Our work is based on large maps made with the IRAM-30m telescope in the two lowest rotational transitions of ^12^CO and ^13^CO (1-0) with high angular (20" or 0.015pc at 115GHz) and spectral (0.055km/s) resolutions. The new data superseeds the first IRAM Key-project of Falgarone et al. (1998A&A...331..669F, Cat. <VIII/66>). The field is centered at 02:00:06.0-87:42:04.1 (J2000); at the estimated distance of 150pc, the size of the maps are 0.72*0.55pc^2^.
- ID:
- ivo://CDS.VizieR/J/ApJ/690/706
- Title:
- Distances of Galactic HII regions
- Short Name:
- J/ApJ/690/706
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We resolve the kinematic distance ambiguity for 266 inner Galaxy HII regions out of a sample of 291 using existing HI and ^13^CO sky surveys. Our sample contains all HII regions with measured radio recombination line emission over the extent of the ^13^CO Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey (18<l<55{deg} and |b|<1) and contains ultra compact (UC), compact, and diffuse HII regions. We use two methods for resolving the distance ambiguity for each HII region: HI emission/absorption (HI E/A) and HI self-absorption (HI SA).
- ID:
- ivo://CDS.VizieR/J/ApJ/689/194
- Title:
- Distances of galactic planetary nebulae
- Short Name:
- J/ApJ/689/194
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Galactic planetary nebula (PN) distances are derived, except in a small number of cases, through the calibration of statistical properties of PNs. Such calibrations are limited by the accuracy of individual PN distances, which are obtained with several nonhomogeneous methods, each carrying its own set of liabilities. In this paper we use the physical properties of the PNs in the Magellanic Clouds and their accurately known distances to recalibrate the Shklovsky/Daub (1982ApJ...260..612D) distance technique. Our new calibration is very similar (within 1%) to the commonly used distance scale by Cahn et al. (1992, Cat. J/A+AS/94/399), although there are important differences. We present a catalog of Galactic PN distances using our recalibration, which can be used for future applications, and compare the best individual Galactic PN distances to our new and several other distance scales, both in the literature and newly recalibrated by us, finding that our scale is the most reliable to date.
- ID:
- ivo://CDS.VizieR/J/ApJ/459/606
- Title:
- Distances of planetary nebulae
- Short Name:
- J/ApJ/459/606
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe an improved method for determining the distances of planetary nebulae (PNe) based on a theoretical/empirical relationship between their radii and radio surface brightness. Like the Shklovsky (constant mass) distance method, our relationship requires only radio flux density and angular size measurements, which are widely available in the literature. Based on models matching the overall Galactic distribution of PNe, we determine how PNe observed in the direction of the Galactic center are actually distributed relative to the bulge in order to establish the usefulness of these PNe for distance studies. We then use the bulge PNe along with PNe with independent distances to establish, calibrate, and test the accuracy of the method. When compared to the best available data our distance method appears to yield distance errors consistent with a scatter of <25% (1{sigma}). And, based on our models scaled to local PNe, we find a mean Galactic center distance of 8.3+/-2.6kpc for the bulge PNe. The relationship that PNe exhibit between radius and surface brightness is in excellent agreement with our simulated nebulae from Paper I (Buckley & Schneider, 1995ApJ...446..279B). We find that no simple power law can describe the changing mass and radius of a PN as it ages; however, our empirical relationship has a limiting behavior that is almost indistinguishable from the assumption made in Shklovsky's distance method that PNe have a constant ionized mass. We reexamine the dispute about the validity of the Shklovsky's distance method as applied to Galactic center PNe in light of these results, and we argue that the Shklovsky method does predict the distances of large, low surface brightness PNe well, but it increasingly overestimates the distance of smaller PNe.
