| 1. |
- Cosentino, Giuliana, 1990, et al.
(författare)
-
Negative and positive feedback from a supernova remnant with SHREC. a detailed study of the shocked gas in IC443
- 2022
-
Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 511:1, s. 953-963
-
Tidskriftsartikel (refereegranskat)abstract
- Supernova remnants (SNRs) contribute to regulate the star formation efficiency and evolution of galaxies. As they expand into the interstellar medium (ISM), they transfer vast amounts of energy and momentum that displace, compress, and heat the surrounding material. Despite the extensive work in galaxy evolution models, it remains to be observationally validated to what extent the molecular ISM is affected by the interaction with SNRs. We use the first results of the ESO-ARO Public Spectroscopic Survey SHREC to investigate the shock interaction between the SNR IC443 and the nearby molecular clump G. We use high-sensitivity SiO(2-1) and (HCO+)-C-13 (1-0) maps obtained by SHREC together with SiO(1-0) observations obtained with the 40-m telescope at the Yebes Observatory. We find that the bulk of the SiO emission is arising from the ongoing shock interaction between IC443 and clump G. The shocked gas shows a well-ordered kinematic structure, with velocities blue-shifted with respect to the central velocity of the SNR, similar to what observed towards other SNR-cloud interaction sites. The shock compression enhances the molecular gas density, n(H-2), up to >10(5) cm(-3), a factor of >10 higher than the ambient gas density and similar to values required to ignite star formation. Finally, we estimate that up to 50 per cent of the momentum injected by IC443 is transferred to the interacting molecular material. Therefore, the molecular ISM may represent an important momentum carrier in sites of SNR-cloud interactions.
|
|
| 2. |
- Costa Silva, A. R., et al.
(författare)
-
NIR jets from a clustered region of massive star formation: Morphology and composition in the IRAS 18264-1152 region
- 2022
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 659
-
Tidskriftsartikel (refereegranskat)abstract
- Context. Massive stars play crucial roles in determining the physical and chemical evolution of galaxies. However, they form deeply embedded in their parental clouds, making it challenging to directly observe these stars and their immediate environments. It is known that accretion and ejection processes are intrinsically related, thus observing the massive protostellar outflows can provide crucial information about the processes governing massive star formation very close to the central engine. Aims. We aim to probe the IRAS 18264-1152 (also known as G19.88-0.53) high-mass star-forming complex in the near infrared (NIR) through its molecular hydrogen (H2) jets to analyse the morphology and composition of the line emitting regions and to compare with other outflow tracers. Methods. We observed the H2 NIR jets via K-band (1.9 2.5 μm) observations obtained with the integral field units VLT/SINFONI and VLT/KMOS. VLT/SINFONI provides the highest NIR angular resolution achieved so far for the central region of IRAS 18264-1152 (∼0.2). We compared the geometry of the NIR outflows with that of the associated molecular outflow, probed by CO (2-1) emission mapped with the Submillimeter Array. Results. We identify nine point sources in the SINFONI and KMOS fields of view. Four of these display a rising continuum in the K-band and are Brγ emitters, revealing that they are young, potentially jet-driving sources. The spectro-imaging analysis focusses on the H2 jets, for which we derived visual extinction, temperature, column density, area, and mass. The intensity, velocity, and excitation maps based on H2 emission strongly support the existence of a protostellar cluster in this region, with at least two (and up to four) different large-scale outflows, found through the NIR and radio observations. We compare our results with those found in the literature and find good agreement in the outflow morphology. This multi-wavelength comparison also allows us to derive a stellar density of ∼4000 stars pc-3. Conclusions. Our study reveals the presence of several outflows driven by young sources from a forming cluster of young, massive stars, demonstrating the utility of such NIR observations for characterising massive star-forming regions. Moreover, the derived stellar number density together with the geometry of the outflows suggest that stars can form in a relatively ordered manner in this cluster.
|
|
| 3. |
- Law, Chi Yan, 1990, et al.
(författare)
-
Isolated Massive Star Formation in G28.20-0.05
- 2022
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 939:2
-
Tidskriftsartikel (refereegranskat)abstract
- We report high-resolution 1.3 mm continuum and molecular line observations of the massive protostar G28.20-0.05 with Atacama Large Millimeter/submillimeter Array. The continuum image reveals a ring-like structure with 2000 au radius, similar to morphology seen in archival 1.3 cm Very Large Array observations. Based on its spectral index and associated H30α emission, this structure mainly traces ionized gas. However, there is evidence for ∼30 M ⊙ of dusty gas near the main millimeter continuum peak on one side of the ring, as well as in adjacent regions within 3000 au. A virial analysis on scales of ∼2000 au from hot core line emission yields a dynamical mass of ∼80 M ⊙. A strong velocity gradient in the H30α emission is evidence for a rotating, ionized disk wind, which drives a larger-scale molecular outflow. An infrared spectral energy distribution (SED) analysis indicates a current protostellar mass of m * ∼ 40 M ⊙ forming from a core with initial mass M c ∼ 300 M ⊙ in a clump with mass surface density of Σcl ∼ 0.8 g cm−2. Thus the SED and other properties of the system can be understood in the context of core accretion models. A structure-finding analysis on the larger-scale continuum image indicates G28.20-0.05 is forming in a relatively isolated environment, with no other concentrated sources, i.e., protostellar cores, above ∼1 M ⊙ found from ∼0.1 to 0.4 pc around the source. This implies that a massive star can form in relative isolation, and the dearth of other protostellar companions within the ∼1 pc environs is a strong constraint on massive star formation theories that predict the presence of a surrounding protocluster.
|
|
| 4. |
- Bhat, Bratati, et al.
(författare)
-
Radiative transfer modeling of the observed line profiles in G31.41+0.31
- 2022
-
Ingår i: Advances in Space Research. - : Elsevier BV. - 1879-1948 .- 0273-1177. ; 69:1, s. 415-437
-
Tidskriftsartikel (refereegranskat)abstract
- An inverse P-Cygni profile of H13CO+ (1 → 0) in G31.41+0.31 was recently observed, which indicates the presence of an infalling gas envelope. Also, an outflow tracer, SiO, was observed. Here, exclusive radiative transfer modelings have been implemented to generate synthetic spectra of some key species (H13CO+, HCN, SiO, NH3, CH3CN, CH3OH, CH3SH, and CH3NCO) and extract the physical features to infer the excitation conditions of the surroundings where they observed. The gas envelope is assumed to be accreting in a spherically symmetric system towards the central hot core region. Our principal intention was to reproduce the observed line profiles toward G31.41+0.31 and extract various physical parameters. The LTE calculation with CASSIS and non-LTE analysis with the RATRAN radiative transfer codes are considered for the modeling purpose. The best-fitted line parameters are derived, which represents the prevailing physical condition of the gas envelope. Our results suggest that an infalling gas could explain the observed line profiles of all the species mentioned above except SiO. An additional outflow component is required to confer the SiO line profile. Additionally, an astrochemical model is implemented to explain the observed abundances of various species in this source.
|
|
| 5. |
- Ghosh, Rana, et al.
(författare)
-
Phenol in High-mass Star-forming Regions
- 2022
-
Ingår i: Research in Astronomy and Astrophysics. - : IOP Publishing. - 1674-4527. ; 22:6
-
Tidskriftsartikel (refereegranskat)abstract
- Phenol, which belongs to the C6H6O isomeric group, is the simplest molecule in the family of alcohol of the aromatic series. Although phenol has yet to be detected in the interstellar medium, a tentative identification was reported toward the Orion KL hot core using the IRAM-30 m line survey. To explore some more species of this isomeric group, we consider ten species to study the fate of their astronomical detection. It is noticed that phenol is the most energetically favorable isomer of this group. In contrast, propargyl ether is the least favorable (having relative energy similar to 103 kcal mol(-1) compared to phenol) species of this group. So far, the studies associated with the formation of phenol are heavily concentrated on combustion chemistry. Here, we suggest a few key reactions (C6H6 + OH -> C6H5 + H2O, C6H6 + O -> C6H5OH, C6H6 + H -> C6H5 + H-2, and C6H5 + OH -> C6H5OH + h nu) for the formation of phenol. All these pathways are included in a large gas-grain chemical network to study its formation in high mass star-forming regions and dark cloud environments. It is noticed that the phenyl (-C6H5) formation by the ice-phase hydrogen abstraction reaction of benzene (i.e., C6H6 + OH -> C6H5 + H2O if allowed at similar to 10 K) could serve as the starting point for the formation of phenol in the gas phase by radiative association reaction C6H5 + OH -> C6H5OH + h nu. The gas-phase reaction C6H6 + O -> C6H5OH significantly contributes to the formation of phenol, when the ice-phase reaction C6H6 + OH -> C6H5 + H2O is not considered at low temperature. Band 4 ALMA archival data of a hot molecular core, G10.47+0.03, are analyzed. It yields an upper limit on phenol abundance of 5.19 x 10(-9). Our astrochemical model delivers an upper limit on phenol abundance of similar to 2.20 x 10(-9) in the hot molecular core, whereas its production in the dark cloud is not satisfactory.
|
|
| 6. |
- Srivastav, Satyam, et al.
(författare)
-
Astrochemical model to study the abundances of branched carbon-chain molecules in a hot molecular core with realistic binding energies
- 2022
-
Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 515:3, s. 3524-3538
-
Tidskriftsartikel (refereegranskat)abstract
- Straight-chain (normal-propyl cyanide, n - C3H7CN) and branched-chain (iso-propyl cyanide, i - C3H7CN) alkyl cyanides are recently identified in the massive star-forming regions (Sgr B2(N) and Orion). These branched-chain molecules indicate that the key amino acids (side-chain structures) may also be present in a similar region. The process by which this branching could propagate towards the higher order (butyl cyanide, C4H9CN) is an active field of research. Since the grain catalysis process could have formed a major portion of these species, considering a realistic set of binding energies are indeed essential. We employ quantum chemical calculations to estimate the binding energy of these species considering water as a substrate because water is the principal constituent of this interstellar ice. We find significantly lower binding energy values for these species than were previously used. It is noticed that the use of realistic binding energy values can significantly change the abundance of these species. The branching is more favourable for the higher order alkyl cyanides with the new binding energies. With the inclusion of our new binding energy values and one essential destruction reaction (i - C3H7CN + H -> CH3C(CH3)CN + H-2 , having an activation barrier of 947 K), abundances of t - C4H9CN dramatically increased.
|
|
