- ID:
- ivo://CDS.VizieR/J/A+A/628/A72
- Title:
- C_2_O and C_3_O in low-mass star-forming regions
- Short Name:
- J/A+A/628/A72
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- C_2_O and C_3_O belong to the carbon chain oxides family. Both molecules have been detected in the gas phase towards several star-forming regions, and to explain the observed abundances, ion-molecule gas-phase reactions have been invoked. On the other hand, laboratory experiments have shown that carbon chain oxides are formed after energetic processing of CO-rich solid mixtures. Therefore, it has been proposed that they are formed in the solid phase in dense molecular clouds after cosmic ion irradiation of CO-rich icy grain mantles and released in the gas phase after their desorption. In this work, we contribute to the understanding of the role of both gas-phase reactions and energetic processing in the formation of simple carbon chain oxides that have been searched for in various low-mass star-forming regions. We present observations obtained with the Noto-32m and IRAM-30m telescopes towards star-forming regions. We compare these with the results of a gas-phase model that simulates C_2_O and C_3_O formation and destruction, and laboratory experiments in which both molecules are produced after energetic processing (with 200 keV protons) of icy grain mantle analogues. New detections of both molecules towards L1544, L1498, and Elias 18 are reported. The adopted gas phase model is not able to reproduce the observed C_2_O/C_3_O ratios, while laboratory experiments show that the ion bombardment of CO-rich mixtures produces C_2_O/C_3_O ratios that agree with the observed values. Based on the results obtained here, we conclude that the synthesis of both species is due to the energetic processing of CO-rich icy grain mantles. Their subsequent desorption because of non-thermal processes allows the detection in the gas-phase of young star-forming regions. In more evolved objects, the non-detection of both C_2_O and C_3_O is due to their fast destruction in the warm gas.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/475/559
- Title:
- 12CO(1-0) and 12CO(2-1) maps of EP Aqr
- Short Name:
- J/A+A/475/559
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CO rotational lines are frequently used to trace the outflows from AGB stars. Some profiles are composite, with a narrow component super-imposed on a broader one. These profiles have been interpreted in different ways, calling for episodic mass loss, a bipolar flow, or a circumstellar disk.
- ID:
- ivo://CDS.VizieR/J/A+A/600/A71
- Title:
- C17O and C18O spectra of nine AGB stars
- Short Name:
- J/A+A/600/A71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We seek to investigate the ^17^O/^18^O ratio for a sample of AGB stars containing M-, S-, and C-type stars. These ratios are evaluated in relation to fundamental stellar evolution parameters: the stellar initial mass and pulsation period. Circumstellar ^13^C^16^O, ^12^C^17^O, and ^12^C^18^O line observations were obtained for a sample of nine stars with various singledish long-wavelength facilities. Line intensity ratios are shown to relate directly to the surface ^17^O/^18^O abundance ratio. Stellar evolution models predict the ^17^O/^18^O ratio to be a sensitive function of initial mass and to remain constant throughout the entire TP-AGB phase for stars initially less massive than 5 solar masses. This makes the measured ratio a probe of the initial stellar mass. Observed ^17^O/^18^O ratios are found to be well in the range predicted by stellar evolution models that do not consider convective overshooting. From this, accurate initial mass estimates are calculated for seven sources. For the remaining two sources, there are two mass solutions, although there is a larger probability that the low-mass solution is correct. Finally, we present hints at a possible separation between M/S- and C-type stars when comparing the ^17^O/^18^O ratio to the stellar pulsation period.
- ID:
- ivo://CDS.VizieR/J/A+A/481/93
- Title:
- CO and HC3N maps of IRAS 20050+2720
- Short Name:
- J/A+A/481/93
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the third in a series of papers devoted to studying intermediate- mass molecular outflows and their powering sources in detail and with high -angular resolution. This paper studies the intermediate-mass YSO IRAS 20050+2720 and its molecular outflow and puts the results of this and the previous studied sources in the context of intermediate-mass star formation. We carried out VLA observations of the 7mm continuum emission and OVRO observations of the 2.7mm continuum emission, CO (1-0), C18O (1-0) and HC3N (12-11) to map the core towards IRAS 20050+2720. The high-angular resolution of the observations allowed us to derive the properties of the dust emission, the molecular outflow, and the dense protostellar envelope. By adding this source to the sample of intermediate-mass protostars with outflows, we compared their properties and evolution with those of lower mass counterparts. The 2.7mm continuum emission has been resolved into three sources, labeled OVRO 1, OVRO 2, and OVRO 3. Two of them, OVRO 1 and OVRO 2, have also been detected at 7mm. OVRO 3, which is located close to the C18O emission peak, could be associated with IRAs 20050+2720. The mass of the sources, estimated from the dust continuum emission, is 6.5M_{sun}_ for OVRO 1, 1.8M_{sun}_ for OVRO 2, and 1.3M_{sun}_ for OVRO 3. The CO (1-0) emission traces two bipolar outflows within the OVRO field of view, a roughly east-west bipolar outflow, labeled A, driven by the intermediate-mass source OVRO 1, and a northeast-southwest bipolar outflow, labeled B, probably powered by a YSO engulfed in the circumstellar envelope surrounding OVRO 1. The multiplicity of sources observed towards IRAS 20050+2720 appears to be typical of intermediate-mass protostars, which form in dense clustered environments. In some cases, as for example IRAS 20050+2720, intermediate- mass protostars would start forming after a first generation of low-mass stars has completed their main accretion phase. The properties of intermediate-mass protostars and their outflows are not significantly different from those of low-mass stars. Although intermediate-mass outflows are intrinsically more energetic than those driven by low-mass YSOs, they do not show intrinsically more complex morphologies when observed at high angular resolution. Known intermediate-mass protostars do not form a homogeneous group. Some objects are likely in an earlier evolutionary stage as suggested by the infrared emission and the outflow properties.
- ID:
- ivo://CDS.VizieR/J/A+AS/99/291
- Title:
- CO and HCN observations of circumstellar envelopes
- Short Name:
- J/A+AS/99/291
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have searched the literature for all observations of the ^12^CO(1-0), ^12^CO(2-1), and HCN(1-0) lines in circumstellar envelopes of late type stars published between January 1985 and September 1992. We report data for 1361 observations (stellar velocity, expansion velocity, peak intensity, integrated area, noise level). This CO-HCN sample now contains 444 sources. 184 are identified as oxygen-rich, 205 as carbon-rich, and there are 9 S stars. About 85% of the sources are AGB stars. There are 32 planetary nebulae and about thirty post-AGB stars candidates. Besides results of millimeter observations, we also list identifications, coordinates, IRAS data, chemical and spectral types for every source. For AGB stars, we have estimated (or compiled) bolometric fluxes and distances for 349 sources, and mass loss rates deduced from CO results for 324 sources, taking into account the influence of the CO photodissociation radius. We also list mass loss rates derived from detailed models of CO emission which we could find in the literature.
- ID:
- ivo://CDS.VizieR/J/A+AS/126/3
- Title:
- CO and HI in interacting galaxies
- Short Name:
- J/A+AS/126/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using SEST, the Parkes antenna and the Australia Telescope Compact Array, we have made a survey of the ^12^CO(1-0) and HI emission of an optically-selected sample of =~60 southern interacting and merging galaxies. In this paper we present the data and determine global masses of neutral gas (in molecular and atomic form) for the observed galaxies. We have detected HI in 26 systems and found that these galaxies have less than 15% of their gas in molecular form.
- ID:
- ivo://CDS.VizieR/J/ApJ/831/20
- Title:
- C/O and Mg/Si for solar neighborhood's stars
- Short Name:
- J/ApJ/831/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The carbon-to-oxygen ratio in a protoplanetary disk can have a dramatic influence on the compositions of any terrestrial planets formed. In regions of high C/O, planets form primarily from carbonates, and in regions of low C/O, the ratio of magnesium to silicon determines the types of silicates that dominate the compositions. We present C/O and Mg/Si ratios for 852 F, G, and K dwarfs in the solar neighborhood. We find that the frequency of carbon-rich dwarfs in the solar neighborhood is <0.13% and that 156 known planet hosts in the sample follow a similar distribution as all of the stars as a whole. The cosmic distribution of Mg/Si for these same stars is broader than the C/O distribution and peaks near 1.0, with ~60% of systems having 1<=Mg/Si<2, leading to rocky planet compositions similar to the Earth. This leaves 40% of systems that can have planets that are silicate-rich and that may have very different compositions than our own.
- ID:
- ivo://CDS.VizieR/J/A+A/554/A55
- Title:
- C^18^O(1-0) and N_2_H^+^(1-0) in L1495/B213
- Short Name:
- J/A+A/554/A55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Core condensation is a critical step in the star-formation process, but it is still poorly characterized observationally. We have studied the 10pc-long L1495/B213 complex in Taurus to investigate how dense cores have condensed out of the lower density cloud material. We observed L1495/B213 in C^18^O(1-0), N_2_H^+^(1-0), and SO(J_N_=3_2_-2_1_) with the 14m FCRAO telescope, and complemented the data with dust continuum observations using APEX (870um) and IRAM 30m (1200um).
- ID:
- ivo://CDS.VizieR/J/A+A/489/1271
- Title:
- CO and OH abundances of 23 K-M giants
- Short Name:
- J/A+A/489/1271
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on the high resolution infrared spectra observed with the Fourier Transform Spectrometer (FTS) at the 4m telescope of the Kitt Peak National Observatory (KPNO), ro-vibrational lines of ^12^C^16^O, ^13^C^16^O, ^12^C^17^O, and ^16^OH were measured. Some details of the observed spectra including the resolution, S/N ratio, and data of observation are given in table2. The spectroscopic and equivalent width data are given in table3 for 23 red giant stars. The resulting data are used to investigate the nature of the infrared spectra of K-M giant stars. It is found that only the weak lines (log(W/nu)<-4.75) carry the information on the photosphere and hence can be used to extract the nature of the photosphere such as the stellar abundances. The intermediate-strength (-4.75<log(W/nu)<-4.40) as well as the strong (log(W/nu)>-4.4) lines are badly disturbed by the lines of non-photospheric origin. In other words, most lines dominating the infrared spectra, except for the weak lines, are actually hybrid of at least two different kinds of lines originating in the photosphere and in an extra molecular layers outside of photosphere. The nature of the extra layers is not known well, but it may be related to the molecular envelope producing H_2_O lines, not only in late M but also in early M giants as well. Also, the intermediate-strength lines include those with LEP as high as 2eV and hence the extra molecular layer should be quite warm. For the reason outlined above, we determine C, O, and their isotopic abundances using only the weak lines, but we listed the measured data not only of the weak lines but also of the stronger lines as well in table3, with the hope that these data can be of some use to clarify the nature of the warm extra molecular layers.
- ID:
- ivo://CDS.VizieR/J/ApJS/236/49
- Title:
- CO and 850um obs. of Planck Galactic cold clumps
- Short Name:
- J/ApJS/236/49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to understand the initial conditions and early evolution of star formation in a wide range of Galactic environments, we carried out an investigation of 64 Planck Galactic cold clumps (PGCCs) in the second quadrant of the Milky Way. Using the ^13^CO and C^18^O J=1-0 lines and 850{mu}m continuum observations, we investigated cloud fragmentation and evolution associated with star formation. We extracted 468 clumps and 117 cores from the ^13^CO line and 850{mu}m continuum maps, respectively. We made use of the Bayesian distance calculator and derived the distances of all 64 PGCCs. We found that in general, the mass-size plane follows a relation of m~r^1.67^. At a given scale, the masses of our objects are around 1/10 of that of typical Galactic massive star-forming regions. Analysis of the clump and core masses, virial parameters, densities, and mass-size relation suggests that the PGCCs in our sample have a low core formation efficiency (~3.0%), and most PGCCs are likely low-mass star-forming candidates. Statistical study indicates that the 850{mu}m cores are more turbulent, more optically thick, and denser than the ^13^CO clumps for star formation candidates, suggesting that the 850{mu}m cores are likely more appropriate future star formation candidates than the ^13^CO clumps.
