- ID:
- ivo://CDS.VizieR/J/A+A/610/A10
- Title:
- Sgr B2 los molecular absorption line spectra
- Short Name:
- J/A+A/610/A10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The 1-50 GHz PRebiotic Interstellar MOlecular Survey (PRIMOS) contains >50 molecular absorption lines observed in clouds located in the line-of-sight to Sgr B2(N). The line-of- sight material is associated with diffuse and translucent clouds located in the Galactic Center, Bar, and spiral arms in the disk. We measure the column densities and estimate abundances, relative to H_2_, of 11 molecules and additional isotopologues observed in this material. We use absorption by optically thin transitions of c-C_3_H_2_ to estimate the molecular hydrogen columns, and argue that this method is preferable to more commonly used methods. We discuss the kinematic structure and abundance patterns of small molecules including the sulfur-bearing species CS, SO, CCS, H_2_CS, and HCS+; oxygen-bearing molecules OH, SiO, and H_2_CO; and simple hydrocarbon molecules c-C_3_H_2_, l-C_3_H, and l-C_3_H^+^. Finally, we discuss the implications of the observed chemistry for the structure of the gas and dust in the ISM. Highlighted results include the following. First, whereas gas in the disk has a molecular hydrogen fraction of 0.65, clouds on the outer edge of the Galactic Bar and in or near the Galactic Center have molecular fractions of 0.85 and >0.9, respectively. Second, we observe trends in isotope ratios with Galactocentric distance; while carbon and silicon show enhancement of the rare isotopes at low Galactocentric distances, sulfur exhibits no trend with Galactocentric distance. We also determine that the ratio of c-C_3_H_2_/c-H^13^CCCH provides a good estimate of the ^12^C/^13^C ratio, whereas H_2_CO/H_2_(^13^C)O exhibits fractionation. Third, we report the presence of l-C_3_H^+^ in diffuse clouds for the first time. Finally, we suggest that CS has an enhanced abundance within higher density clumps of material in the disk, and therefore may be diagnostic of cloud conditions. If this holds, the diffuse clouds in the Galactic disk contain multiple embedded hyperdensities in a clumpy structure, and the density profile is not a simple function of A_V_.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/633/A120
- Title:
- SgrB2(M) ^13^CCC and C^13^CC spectra
- Short Name:
- J/A+A/633/A120
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Carbon molecules and their ^13^C-isotopologues can be used to determine the ^12^C/^13^C abundance ratios in stellar and interstellar objects. C3 is a pure carbon chain molecule found in star forming regions and in stellar shells of carbon-rich late-type stars. Latest laboratory data of ^13^C-isotopologues of C3 allow a selective search for the mono-substituted species ^13^CCC and C^13^CC based on accurate ro-vibrational frequencies. Our aim was to provide the first detection of the ^13^C-isotopologues ^13CCC and C^13^CC in space and to derive the ^12^C/ ^13^C ratio of interstellar gas in the massive star-forming region SgrB2(M) near the Galactic Center. We used the heterodyne receivers GREAT and upGREAT on board SOFIA to search for the ro-vibrational transitions Q(2) and Q(4) of ^13^CCC and C^13^CC at 1.9THz along the line of sight towards SgrB2(M). In addition, to determine the local excitation temperature we analyzed data from nine ro-vibrational transitions of the main isotopologue CCC in the frequency range between 1.6-1.9THz which were taken from the Herschel Science Data Archive. We report the first detection of the isotopologues ^13^CCC and C^13^CC. For both species the ro-vibrational absorption lines Q(2) and Q(4) have been identified, primarily arising from the warm gas physically associated with the strong continuum source SgrB2(M). From the available CCC ro-vibrational transitions we derived a gas excitation temperature of Tex=44.4^+4.7^_-3.9_K and a total column density of N(CCC)=3.88^+0.39^_-0.35_x10^15^cm^-2.. Assuming the excitation temperatures of C^13^CC and ^13^CCC to be the same as for CCC, we obtained column densities of the ^13^C-isotopologues of N(C^13^CC)=2.1^+0.9^_-0.6^_x10^14^cm^-2^ and N(^13^CCC)=2.4^+1.2^_-0.8_x10^14^cm^-2^. The derived ^12^C/^13^C abundance ratio in the C3 molecules is 20.5+/-4.2, which is in agreement with the elemental ratio of 20, typically observed in SgrB2(M). However, we find the N(^13^CCC)/N(C^13^CC) ratio to be 1.2+/-0.1, which is shifted from the statistically expected value of 2. We propose that the discrepant abundance ratio arises due to the the lower zero-point energy of C^13^CC which makes position- exchange reaction converting C^13^CC to C^13^CC energetically favorable.
- ID:
- ivo://CDS.VizieR/J/ApJS/117/427
- Title:
- Sgr B2 spectral survey
- Short Name:
- J/ApJS/117/427
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have surveyed the frequency band 218.30-263.55GHz toward the core positions N and M and the quiescent cloud position NW in the Sgr B2 molecular cloud using the Swedish-ESO Submillimetre Telescope. In total 1730, 660, and 110 lines were detected in N, M, and NW, respectively, and 42 different molecular species were identified. The number of unidentified lines are 337, 51, and eight. Toward the N source, spectral line emission constitutes 22% of the total detected flux in the observed band, and complex organic molecules are the main contributors. Toward M, 14% of the broadband flux is caused by lines, and SO2 is here the dominant source of emission. NW is relatively poor in spectral lines and continuum. In this paper we present the spectra together with tables of suggested line identifications.
- ID:
- ivo://CDS.VizieR/J/AJ/151/143
- Title:
- Silicon depletion in the interstellar medium
- Short Name:
- J/AJ/151/143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report interstellar silicon (Si) depletion and dust-phase column densities of Si along 131 Galactic sight lines using archival observations. The data were corrected for differences in the assumed oscillator strength. This is a much larger sample than previous studies but confirms the majority of results, which state that the depletion of Si is correlated with the average density of hydrogen along the line of sight (<n(H)>) as well as the fraction of hydrogen in molecular form (f(H_2_)). We also find that the linear part of the extinction curve is independent of Si depletion. Si depletion is correlated with the bump strength (c_3_/R_V_) and the FUV curvature (c_4_/R_V_) suggesting that silicon plays a significant role in both the 2175{AA} bump and the FUV rise.
- ID:
- ivo://CDS.VizieR/J/A+A/627/A16
- Title:
- Silicon K-edge dust absorption cross sections
- Short Name:
- J/A+A/627/A16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The composition and properties of interstellar silicate dust are not well understood. Inthe X-rays, interstellar dust can be studied in detail, by making use of the fine structure features inthe Si K-edge. The features in the Si K-edge offer a range of possibilities to study silicon-bearingdust, such as investigating the crystallinity, abundance and the chemical composition along a given line of sight. We present newly acquired laboratory measurements of the silicon K-edge of several silicate-compounds which complement our measurements from our earlier pilot study. The resulting dust extinction profiles serve as templates for the interstellar extinction that we observe. The extinction profiles were used to model the interstellar dust in the dense environments of the Galaxy. The laboratory measurements, taken at the Soleil synchrotron facility in Paris, were adapted for astrophysical data analysis and implemented in the SPEX spectral fitting program. The models were used to fit the spectra of nine low-mass X-ray binaries located in the Galactic center neighborhood in order to determine the dust properties along those lines of sight. In most lines of sight can be well fitted by amorphous olivine. We also established upper limits on the amount of crystalline material that the modeling allows. We obtained values of the total silicon abundance, silicon dust abundance and depletion along each of the sightlines. We find a possible gradient of 0.06+/-0.02dex/kpc for the total silicon abundance versus the Galactocentric distance. We do not find a relation between the depletion and the extinction along the line of sight.
786. SimDAL Repository
- ID:
- ivo://vopdc.obspm/lerma/simrepo
- Title:
- SimDAL Repository
- Short Name:
- SimDAL Repo
- Date:
- 10 Jan 2017
- Publisher:
- Paris Astronomical Data Centre - LERMA
- Description:
- The SimDAL repository hosts numerical projects descriptions as standard XML documents following the Simulation Data Model serialization xsd. It allows clients to search (fulltext) for simulation projects or associated protocols of interest and get URIs towards other SimDAL components: SimDAL Search and SimDAL Data Access.
- ID:
- ivo://CDS.VizieR/J/A+A/552/L2
- Title:
- SINFONI K-band observations of IRS54(YLW52)
- Short Name:
- J/A+A/552/L2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Molecular outflows from very low-mass stars (VLMSs) and brown dwarfs have been studied very little. So far, only a few CO outflows have been observed, allowing us to map the immediate circumstellar environment. We present the first spatially resolved H_2_ emission around IRS54 (YLW52), a ~0.1-0.2M_{sun}_ Class I source. By means of VLT SINFONI K-band observations, we probed the H2 emission down to the first ~50AU from the source. The molecular emission shows a complex structure delineating a large outflow cavity and an asymmetric molecular jet. Thanks to the detection of several H_2_transitions, we are able to estimate average values along the jet-like structure (from source position to knot D) of Av~28mag, T~2000-3000K, and H_2_column density N(H_2)~1.7x10^17cm^-2. This allows us to estimate a mass loss rate of ~2x10^-10M_{sun}_/yr for the warm H_2_component . In addition, from the total flux of the Br gamma line, we infer an accretion luminosity and mass accretion rate of 0.64L_{sun}_ and ~3x10^-7M_{sun}_/yr, respectively. The outflow structure is similar to those found in low-mass Class I and CTTS. However, the Lacc/Lbol ratio is very high (~80%), and the mass accretion rate is about one order of magnitude higher when compared to objects of roughly the same mass, pointing to the young nature of the investigated source.
- ID:
- ivo://CDS.VizieR/J/A+A/557/A94
- Title:
- SiO and HCO+ massive molecular outflows
- Short Name:
- J/A+A/557/A94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a study of 14 molecular outflows associated with high-mass star formation. We used the IRAM30m telescope to characterize the outflow emission in the SiO(2-1), SiO(5-4) and HCO^+^(1-0) lines. We detect outflows in all the 14 high-mass star-forming regions in both, the SiO and HCO^+^ lines. Six of the fourteen outflows show bipolarity. The physical parameters derived for these outflows are consistent with outflows powered by massive young stellar objects with luminosities in the range 10^3^-10^4^L_{sun}_. We found a decrease of the SiO abundance (from 10^-8^ to 10^-9^) as the object evolves in time, while there are hints of a possible increase of the HCO^+^ outflow energetics with time. These results suggest a scenario in which SiO is largely enhanced in the first evolutionary stages, probably due to strong shocks produced by the protostellar jet. As the object evolves, the power of the jet would decrease and so does the SiO abundance. During this process, however, the material surrounding the protostar would have been swept up by the jet, and the outflow activity, traced by entrained molecular material (HCO^+^), would increase with time.
- ID:
- ivo://CDS.VizieR/J/A+A/586/A149
- Title:
- SiO in ATLASGAL-selected massive clumps
- Short Name:
- J/A+A/586/A149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The processes leading to the birth of high-mass stars are poorly understood. The key first step to reveal their formation processes is characterising the clumps and cores from which they form. We define a representative sample of massive clumps in different evolutionary stages selected from the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL), from which we aim to establish a census of molecular tracers of their evolution. As a first step, we study the shock tracer, SiO, mainly associated with shocks from jets probing accretion processes. In low-mass young stellar objects (YSOs), outflow and jet activity decreases with time during the star formation processes. Recently, a similar scenario was suggested for massive clumps based on SiO observations. Here we analyse observations of the SiO (2-1) and (5-4) lines in a statistically significant sample to constrain the change of SiO abundance and the excitation conditions as a function of evolutionary stage of massive star-forming clumps. We performed an unbiased spectral line survey covering the 3-mm atmospheric window between 84-117GHz with the IRAM 30m telescope of a sample of 430 sources of the ATLASGAL survey, covering various evolutionary stages of massive clumps. A smaller sample of 128 clumps has been observed in the SiO (5-4) transition with the APEX telescope to complement the (2-1) line and probe the excitation conditions of the emitting gas. We derived detection rates to assess the star formation activity of the sample, and we estimated the column density and abundance using both an LTE approximation and non-LTE calculations for a smaller subsample, where both transitions have been observed.
- ID:
- ivo://CDS.VizieR/J/A+A/321/293
- Title:
- SiO production in interstellar shocks
- Short Name:
- J/A+A/321/293
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the production of SiO in the gas phase of molecular outflows, through the sputtering of Si-bearing material in grains. The sputtering is driven by neutral particle impact on charged grains in C-type shocks, at the speed corresponding to ambipolar diffusion. Shock speeds in the range 10<v_s_<40km/s and preshock densities 10^4^<n_H_<10^7^cm^-3^ have been investigated. Sputtering of Si-bearing material in both the cores and the mantles of the grains is considered. We find that, for v_s_ of approximately 25km/s and n_H_ of the order 10^5^cm^-3^, column densities of SiO similar to those observed in molecular out flow regions can be generated by either mechanism. Impact by particles heavier than helium dominates the core-sputtering process for shock velocities of this order. The profiles of rotational transitions of SiO are computed and compared with observations of molecular outflows.