- 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.
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Search Results
- 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.
- ID:
- ivo://CDS.VizieR/J/ApJ/843/33
- Title:
- SOFIA Massive (SOMA) Star Formation Survey. I.
- Short Name:
- J/ApJ/843/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an overview and first results of the Stratospheric Observatory For Infrared Astronomy Massive (SOMA) Star Formation Survey, which is using the FORCAST instrument to image massive protostars from ~10 to 40{mu}m. These wavelengths trace thermal emission from warm dust, which in Core Accretion models mainly emerges from the inner regions of protostellar outflow cavities. Dust in dense core envelopes also imprints characteristic extinction patterns at these wavelengths, causing intensity peaks to shift along the outflow axis and profiles to become more symmetric at longer wavelengths. We present observational results for the first eight protostars in the survey, i.e., multiwavelength images, including some ancillary ground-based mid- infrared (MIR) observations and archival Spitzer and Herschel data. These images generally show extended MIR/FIR emission along directions consistent with those of known outflows and with shorter wavelength peak flux positions displaced from the protostar along the blueshifted, near-facing sides, thus confirming qualitative predictions of Core Accretion models. We then compile spectral energy distributions and use these to derive protostellar properties by fitting theoretical radiative transfer models. Zhang and Tan models, based on the Turbulent Core Model of McKee and Tan, imply the sources have protostellar masses m*~10-50M_{sun}_ accreting at ~10^-4^-10^-3^M_{sun}_/yr inside cores of initial masses Mc~30-500M_{sun}_ embedded in clumps with mass surface densities {Sigma}_cl_~0.1-3g/cm^2^. Fitting the Robitaille et al. models typically leads to slightly higher protostellar masses, but with disk accretion rates ~100x smaller. We discuss reasons for these differences and overall implications of these first survey results for massive star formation theories.
- ID:
- ivo://CDS.VizieR/J/ApJ/874/16
- Title:
- SOFIA Massive Star Formation Survey. II. 7 protostars
- Short Name:
- J/ApJ/874/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present multiwavelength images observed with SOFIA-FORCAST from ~10 to 40{mu}m of seven high luminosity massive protostars, as part of the SOFIA Massive Star Formation Survey. Source morphologies at these wavelengths appear to be influenced by outflow cavities and extinction from dense gas surrounding the protostars. Using these images, we build spectral energy distributions (SEDs) of the protostars, also including archival data from Spitzer, Herschel, and other facilities. Radiative transfer (RT) models of Zhang & Tan (2018ApJ...853...18Z), based on Turbulent Core Accretion theory, are then fit to the SEDs to estimate key properties of the protostars. Considering the best five models fit to each source, the protostars have masses m*~12-64M_{sun}_ accreting at rates of dm/dt_*_~10^-4^-10^-3^M_{sun}_/yr inside cores of initial masses M_c_~100-500M_{sun}_ embedded in clumps with mass surface densities {Sigma}_cl_~0.1-3g/cm^2^ and span a luminosity range of 10^4^-10^6^L_{sun}_. Compared with the first eight protostars in Paper I (De Buizer+ 2017ApJ...843...33D), the sources analyzed here are more luminous and, thus, likely to be more massive protostars. They are often in a clustered environment or have a companion protostar relatively nearby. From the range of parameter space of the models, we do not see any evidence that {Sigma}cl needs to be high to form these massive stars. For most sources, the RT models provide reasonable fits to the SEDs, though the cold clump material often influences the long wavelength fitting. However, for sources in very clustered environments, the model SEDs may not be such a good description of the data, indicating potential limitations of the models for these regions.
