Rotational excitation of highly excited H2O by H2

2021 ◽  
Vol 502 (4) ◽  
pp. 5356-5361
Author(s):  
Michal Żóltowski ◽  
François Lique ◽  
Agata Karska ◽  
Piotr S Żuchowski
Keyword(s):  
Energy Levels ◽  
Radiative Properties ◽  
Rate Coefficients ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Excitation Rate ◽  
Physical Conditions ◽  
James Webb Space Telescope ◽  
Non Local ◽  
Insight Into

ABSTRACT Water is a key molecule for interstellar chemistry. Observations with Herschel telescope show significant population of very high rotational transitions (j ≳ 8) in young stellar objects, indicating significant amounts of water in hot (T ≳ 1500 K) and dense (n ≳ 106 cm−3) gas. Non-local thermodynamic equilibrium (LTE) modelling of these observations requires the knowledge of the collisional and radiative properties of highly excited water at high temperature. The aim of this work is to calculate a new set of excitation rate coefficients for both para- and ortho-H2O induced by collisions with H2 for energy levels up to j = 17. Quantum scattering calculations were performed using a reduced dimensional approach and the coupled states approximation. Rate coefficients were obtained for 97 pure rotational energy levels of both para- and ortho-H2O and for temperatures up to 2000 K. With the forthcoming launch of the James Webb Space Telescope, these new collisional data will allow us to gain more insight into the physical conditions in star- and planet-forming regions.

Laboratory investigations aimed at building a database for the interpretation of JWST spectra

2019 ◽  
Vol 15 (S350) ◽  
pp. 77-80
Author(s):  
Maria Elisabetta Palumbo ◽  
Giuseppe A. Baratta ◽  
Gleb Fedoseev ◽  
Daniele Fulvio ◽  
Carlotta Scirè ◽  
...  
Keyword(s):  
Thermal Processing ◽  
Laboratory Data ◽  
Cosmic Ray ◽  
Peak Position ◽  
Young Stellar Objects ◽  
Line Of Sight ◽  
High Quality ◽  
Stellar Objects ◽  
James Webb Space Telescope ◽  
Laboratory Investigations

AbstractThe James Webb Space Telescope (JWST) is expected to be launched in 2021. The JWST’s science instruments will provide high quality spectra acquired in the line of sight to young stellar objects whose interpretation will require a robust database of laboratory data. With this in mind, an experimental work is in progress in the Laboratory for Experimental Astrophysics in Catania to study the profile (shape, width, and peak position) of the main infrared bands of molecular species expected to be present in icy grain mantles. Our study also takes into account the modifications induced on icy samples by low-energy cosmic ray bombardment and by thermal processing. Here we present some recent results on deuterium hydrogen monoxide (HDO), N-bearing species, and carbon dioxide (CO2).

scholarly journals 3D Gray Radiative Properties of Accretion Shocks in Young Stellar Objects

2014 ◽  
Vol 64 ◽  
pp. 04005
Author(s):  
L. Ibgui ◽  
S. Orlando ◽  
C. Stehlé ◽  
J.-P. Chièze ◽  
I. Hubeny ◽  
...  
Keyword(s):  
Radiative Properties ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Accretion Shocks

scholarly journals Young stellar objects close to Sgr A*

2013 ◽  
Vol 9 (S303) ◽  
pp. 144-146
Author(s):  
B. Jalali ◽  
F. I. Pelupessy ◽  
A. Eckart ◽  
S. Portegies Zwart ◽  
N. Sabha ◽  
...  
Keyword(s):  
Black Hole ◽  
Star Formation ◽  
Radius Vector ◽  
Young Stellar Objects ◽  
Infrared Excess ◽  
Stellar Objects ◽  
Physical Conditions ◽  
Strong Compression ◽  
Sgr A ◽  
Hydrodynamical Simulations

AbstractWe aim at modeling small groups of young stars such as IRS 13N, 0.1 pc away from Sgr A*, which is suggested to contain a few embedded massive young stellar objects. We perform hydrodynamical simulations to follow the evolution of molecular clumps orbiting around a 4 × 106 M⊙ black hole, to constrain the formation and the physical conditions of such groups.We find that the strong compression due to the black hole along the orbital radius vector of clumps evolving on highly eccentric orbits causes the clumps densities to increase to higher than the tidal density of Sgr A* and required for star formation. This suggests that the tidal compression from the black hole could support star formation.Additionally, we speculate that the infrared excess source G2/DSO approaching Sgr A* on a highly eccentric orbit could be associated with a dust enshrouded star that may have been formed recently through the mechanism supported by our models.

scholarly journals Rotational relaxation of HCO+ and DCO+ by collision with H2

2020 ◽  
Vol 497 (4) ◽  
pp. 4276-4281 ◽  
Author(s):  
Otoniel Denis-Alpizar ◽  
Thierry Stoecklin ◽  
Anne Dutrey ◽  
Stéphane Guilloteau
Keyword(s):  
Cross Sections ◽  
Rate Coefficients ◽  
Local Thermal Equilibrium ◽  
Rotational Relaxation ◽  
Close Coupling ◽  
Excitation Rate ◽  
Rotational States ◽  
Non Local ◽  
The Difference ◽  
Isotopic Effects

ABSTRACT The HCO+ and DCO+ molecules are commonly used as tracers in the interstellar medium. Therefore, accurate rotational rate coefficients of these systems with He and H2 are crucial in non-local thermal equilibrium models. We determine in this work the rotational de-excitation rate coefficients of HCO+ in collision with both para- and ortho-H2, and also analyse the isotopic effects by studying the case of DCO+. A new four-dimensional potential energy surface from ab initio calculations was developed for the HCO+–H2 system, and adapted to the DCO+–H2 case. These surfaces are then employed in close-coupling calculations to determine the rotational de-excitation cross-sections and rate coefficients for the lower rotational states of HCO+ and DCO+. The new rate coefficients for HCO+ + para-H2 were compared with the available data, and a set of rate coefficients for HCO+ + ortho-H2 is also reported. The difference between the collision rates with ortho- and para-H2 is found to be small. These calculations confirm that the use of the rate coefficients for HCO+ + para-H2 for estimating those for HCO+ + ortho-H2 as well as for DCO+ + para-H2 is a good approximation.

scholarly journals Magnetic Fields in 7 Young Stellar Objects Observed with Nançay Radio Telescope

2013 ◽  
Vol 9 (S302) ◽  
pp. 38-39
Author(s):  
Olga Bayandina ◽  
Alexei Alakoz ◽  
Irina Val'tts
Keyword(s):  
Magnetic Fields ◽  
Energy Levels ◽  
Zeeman Splitting ◽  
Young Stellar Objects ◽  
Small Scale ◽  
Stellar Objects ◽  
Local Strength ◽  
Full Picture ◽  
Methanol Masers ◽  
The Moment

AbstractMagnetic fields (MF) can play an essential role in the evolution of the interstellar medium - especially at the early evolutionary stages. Small scale research related to the interaction of MF and pre-stellar condensations are unresolved issues. In quantitative terms, submissions about forming a full picture of gas-dust fragments evolution are far from complete, considering delay of their collapse caused by MF and the reverse effect of self-gravitating objects on the transformation of force lines and changing the values of local strength. The role of these interrelated processes is very important in the estimation of time of evolution of protostellar structures. In contrast to OH, in methanol molecule (most investigating at the moment) there is no unpaired electron, and the Zeeman splitting of the energy levels in CH3OH regards only the levels caused by the nuclear spin. Therefore, Zeeman spectrum in methanol is certainly not going to be as effective as in OH. However, since many methanol masers - Class I (MMI - formed at the earliest stage of the evolution of gas and dust condensations) and Class II (MMII - the area around very young stars and protoplanetary disks) - are associated with OH masers, then from spectra of OH masers the parameters of MF can be estimated, at least, near different methanol masers classes, i.e. in condensations which are at different evolutionary stages. This report presents the results of polarization observations 7 OH maser sources at the NRT (France). The main goal is comparing similarities and differences in MF strength and orientation in these masers, which essentially different according to the type of methanol masers associated with them, i.e. the evolutionary type.

scholarly journals Young Stellar Objects in the Magellanic Clouds: Herschel Spectroscopy First Results

2015 ◽  
Vol 11 (S315) ◽  
Author(s):  
Joana M. Oliveira ◽  
Jacco Th. van Loon ◽  
Marta Sewiło
Keyword(s):  
Gas Phase ◽  
Magellanic Clouds ◽  
Young Stellar Objects ◽  
Space Observatory ◽  
Herschel Space Observatory ◽  
Stellar Objects ◽  
Preliminary Results ◽  
Physical Conditions ◽  
First Results

AbstractWe present preliminary results from spectroscopy obtained with PACS and SPIRE onboard the Herschel Space Observatory of a sample of massive Young Stellar Objects in the Magellanic Clouds. We analyse key gas-phase cooling species (Oi], [Cii], H2O, CO, OH), in order to characterise the physical conditions in these metal-poor environments.

scholarly journals Inelastic rate coefficients for collisions of N2H+ with H2

2020 ◽  
Vol 495 (2) ◽  
pp. 2524-2530 ◽  
Author(s):  
Christian Balança ◽  
Yohann Scribano ◽  
Jérôme Loreau ◽  
François Lique ◽  
Nicole Feautrier
Keyword(s):  
Channel Model ◽  
Molecular Ions ◽  
Rate Coefficients ◽  
Close Coupling ◽  
Excitation Rate ◽  
Hyperfine Transitions ◽  
Physical Conditions ◽  
Deep Well ◽  
State Rate ◽  
Highly Correlated

ABSTRACT N2H+ is one of the first molecular ions observed in the interstellar medium and it is of particular interest to probe the physical conditions of cold molecular clouds. Accurate modelling of the observed lines requires the knowledge of collisional excitation rate coefficients. Thus, we have calculated rate coefficients for the excitation of N2H+ by H2, the most abundant collisional partner. The calculations are based on a new potential energy surface obtained from highly correlated ab initio calculations. This 4D-interaction surface exhibits a very deep well of ≈2530 cm−1 making fully converged scattering calculations very difficult to carry out, when one takes into account the rotational structure of H2. To overcome this difficulty, two approximate approaches, the adiabatic hindered rotor approach (AHR) and the statistical adiabatic channel model, were tested by comparing the results with those obtained from full 4D close-coupling calculations. The AHR treatment, which reduces the scattering calculations to a 2D problem was found to give the best results at all temperatures and even for transitions involving high N2H+ rotational levels. State-to-state rate coefficients between the 26 first N2H+ rotational levels were calculated for temperatures ranging from 5 K up to 500 K. Using a recoupling technique, rate coefficients are obtained among hyperfine transitions.

scholarly journals Binary outflows from young stars: interaction of co-orbital jet and wind

2019 ◽  
Author(s):  
Chris J R Lynch ◽  
Michael D Smith ◽  
Simon C O Glover
Keyword(s):  
Young Stars ◽  
Young Stellar Objects ◽  
Molecular Flow ◽  
Stellar Objects ◽  
Star Forming ◽  
Molecular Outflows ◽  
Molecular Outflow ◽  
T Tauri ◽  
Molecular Lines ◽  
Insight Into

Abstract Jets from young stellar objects provide insight into the workings of the beating heart at the centre of star forming cores. In some cases, multiple pulsed outflows are detected such as the atomic and molecular jets from a proposed binary system in the T Tauri star HH 30. We investigate here the development and propagation of duelling atomic and molecular outflows stemming from the two stars in co-orbit. We perform a series of numerical experiments with the ZEUS-MP code with enhanced cooling and chemistry modules. The aim of this work is to identify signatures on scales of order 100 AU. The jet sources are off the grid domain and so it is the propagation and interaction from ∼ 20 AU out to 100 AU simulated here. We find that the molecular flow from the orbiting source significantly disturbs the atomic jet, deflecting and twisting the jet and disrupting the jet knots. Regions of high ionisation are generated as the atomic jet rams through the dense molecular outflow. Synthetic images in atomic and molecular lines are presented which demonstrate identifying signatures. In particular, the structure within the atomic jet is lost and Hα may trace the walls of the present CO cavity or where the walls have been recently. These results provide a framework for the interpretation of upcoming high resolution observations.

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