- 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.
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- 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.
- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/598/A76
- Title:
- Six infrared dark clouds multi-wavelength obs.
- Short Name:
- J/A+A/598/A76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Infrared dark clouds (IRDCs) are ubiquitous in the Milky Way, yet they play a crucial role in breeding newly-formed stars. In order to further understand the dynamics, chemistry, and evolution of IRDCs, we carried out multi-wavelength observations towards a small sample. We performed new observations with the IRAM 30m and CSO 10.4m telescopes, with tracers HCO^+^, HCN, N_2_H^+^, C^18^O, DCO^+^, SiO, and DCN towards six IRDCs G031.97+00.07, G033.69-00.01, G034.43+00.24, G035.39-00.33, G038.95-00.47, and G053.11+00.05.
- ID:
- ivo://CDS.VizieR/J/A+A/229/362
- Title:
- Small-scale structures in HI hole of M33
- Short Name:
- J/A+A/229/362
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent high-resolution HI observations of M33 reveal a large number of regions that are devoid of emission. We interpret these regions as holes formed by interstellar winds; a catalogue containing 148 of these HI holes has been compiled. Their diameters range from the survey resolution limit (>40pc) to 1kpc. The swept-up mass, estimated from surrounding HI densities, ranges from 10^3^M_{sun}_ to 10^7^M_{sun}_. Energies needed to excavate such holes are between 10^49^ to 10^54^erg. Indicative ages, based on derived expansion velocities and diameters, show a cutoff near 7x10^6^yr. Three statistical analysis techniques are applied to determine positional correlation of the H I holes with H II regions, OB associations, and supernova remnants.
- ID:
- ivo://CDS.VizieR/J/ApJ/744/20
- Title:
- S^4^MC project: 6 star forming regions PAHs
- Short Name:
- J/ApJ/744/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of mid-infrared spectroscopic mapping observations of six star-forming regions in the Small Magellanic Cloud (SMC) from the Spitzer Spectroscopic Survey of the SMC (S^4^MC). We detect the mid-IR emission from polycyclic aromatic hydrocarbons (PAHs) in all of the mapped regions, greatly increasing the range of environments where PAHs have been spectroscopically detected in the SMC. We investigate the variations of the mid-IR bands in each region and compare our results to studies of the PAH bands in the SINGS sample and in a sample of low-metallicity starburst galaxies. PAH emission in the SMC is characterized by low ratios of the 6-9um features relative to the 11.3um feature and weak 8.6 and 17.0um features. Interpreting these band ratios in the light of laboratory and theoretical studies, we find that PAHs in the SMC tend to be smaller and less ionized than those in higher metallicity galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/587/A71
- Title:
- SNR G11.0-0.0 1.4GHz radio continuum image
- Short Name:
- J/A+A/587/A71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The main goal of this paper is to provide new insights on the origin of the observable flux of {gamma} rays from HESS J1809-193 using new high-quality observations in the radio domain. We used the Expanded Very Large Array (now known as the Karl G. Jansky Very large Array, JVLA) to produce a deep full-synthesis imaging at 1.4GHz of the vicinity of PSR J1809-1917. These data were used in conjunction with 12CO observations from the James Clerk Maxwell Telescope in the transition line J=3-2 and atomic hydrogen data from the Southern Galactic Plane Survey to investigate the properties of the interstellar medium in the direction of the source HESS J1809-193.
