Astronomical data analysis software and systems

We present the fifth release of the UMIST Database for Astrochemistry (UDfA). The new reaction network contains 6173 gas-phase reactions, involving 467 species, 47 of which are new to this release. We have updated rate coefficients across all reaction types. We have included 1171 new anion reactions and updated and reviewed all photorates. In addition to the usual reaction network, we also now include, for download, state-specific deuterated rate coefficients, deuterium exchange reactions and a list of surface binding energies for many neutral species. Where possible, we have referenced the original source of all new and existing data. We have tested the main reaction network using a dark cloud model and a carbon-rich circumstellar envelope model. We present and briefly discuss the results of these models.

The UMIST database for astrochemistry 2012

ABSTRACT CLOUDY is a large‐scale spectral synthesis code designed to simulate fully physical conditions within an astronomical plasma and then predict the emitted spectrum. Here we describe version 90 (C90) of the code, paying particular attention to changes in the atomic database and numerical methods that have affected predictions since the last publicly available version, C84. The computational methods and uncertainties are outlined together with the direction future development will take. The code is freely available and is widely used in the analysis and interpretation of emission‐line spectra. Web access to the Fortran source for CLOUDY, its documentation Hazy, and an independent electronic form of the atomic database is also described.

Cloudy: Numerical simulation of plasmas and their spectra

After hydrogen, oxygen, and carbon, nitrogen is one of the most chemically active species in the interstellar medium (ISM). Nitrogen bearing molecules have great importance as they are actively involved in the formation of biomolecules. Therefore, it is essential to look for nitrogen-bearing species in various astrophysical sources, specifically around high-mass star-forming regions where the evolutionary history is comparatively poorly understood. In this paper, we report the observation of three potential pre-biotic molecules, namely, isocyanic acid (HNCO), formamide (NH2CHO), and methyl isocyanate (CH3NCO), which contain peptide-like bonds (-NH-C(=O)-) in a hot molecular core, G10.47+0.03 (hereafter, G10). Along with the identification of these three complex nitrogen-bearing species, we speculate their spatial distribution in the source and discuss their possible formation pathways under such conditions. The rotational diagram method under the LTE condition has been employed to estimate the excitation temperature and the column density of the observed species. Markov Chain Monte Carlo method was used to obtain the best suited physical parameters of G10 as well as line properties of some species. We also determined the hydrogen column density and the optical depth for different continuum observed in various frequency ranges. Finally, based on these observational results, we have constructed a chemical model to explain the observational findings. We found that HNCO, NH2CHO, and CH3NCO are chemically linked with each other.

Identification of pre-biotic molecules containing Peptide-like bond in a hot molecular core, G10.47+0.03

Identification of Prebiotic Molecules Containing Peptide-like Bonds in a Hot Molecular Core, G10.47+0.03

We consider six isomeric groups (CH3N, CH5N, C2H5N, C2H7N, C3H7N and C3H9N) to review the presence of amines and aldimines within the interstellar medium (ISM). Each of these groups contains at least one aldimine or amine. Methanimine (CH2NH) from CH3N and methylamine (CH3NH2) from CH 5 N isomeric group were detected a few decades ago. Recently, the presence of ethanimine (CH3CHNH) from C2H5N isomeric group has been discovered in the ISM. This prompted us to investigate the possibility of detecting any aldimine or amine from the very next three isomeric groups in this sequence: C2H7N, C3H7N and C3H9N. We employ high-level quantum chemical calculations to estimate accurate energies of all the species. According to enthalpies of formation, optimized energies, and expected intensity ratio, we found that ethylamine (precursor of glycine) from C2H7N isomeric group, (1Z)-1-propanimine from C3H7N isomeric group, and trimethylamine from C3H9N isomeric group are the most viable candidates for the future astronomical detection. Based on our quantum chemical calculations and from other approximations (from prevailing similar types of reactions), a complete set of reaction pathways to the synthesis of ethylamine and (1Z)-1-propanimine is prepared. Moreover, a large gas-grain chemical model is employed to study the presence of these species in the ISM. Our modeling results suggest that ethylamine and (1Z)-1-propanimine could efficiently be formed in hot-core regions and could be observed with present astronomical facilities. Radiative transfer modeling is also implemented to additionally aid their discovery in interstellar space.

Chemical Modeling for Predicting the Abundances of Certain Aldimines and Amines in Hot Cores

G3141+031 is a well known chemically rich hot molecular core (HMC) Using Band 3 observations from the Atacama Large Millimeter Array (ALMA), we have analyzed the chemical and physical properties of the source We have identified methyl isocyanate (CH3NCO), a precursor of prebiotic molecules, toward the source In addition to this, we have reported the presence of complex organic molecules (COMs) like methanol (CH3OH), methanethiol (CH3SH), and methyl formate (CH3OCHO) Additionally, we have used transitions from molecules like HCN, (HCO+)-C-13, and SiO to trace the presence of infall and outflow signatures around the star-forming region For the COMs, we have estimated the column densities and kinetic temperatures, assuming molecular excitation under local thermodynamic equilibrium (LTE) conditions From the estimated kinetic temperatures of certain COMs, we found that multiple temperature components may be present in the HMC environment Comparing the obtained molecular column densities between the existing observational results around other HMCs, it seems that the COMs are favorably produced in the hot core environment (similar to 100 K or higher) Though the spectral emissions toward G3141+031 are not fully resolved, we find that CH3NCO and other COMs are possibly formed on grain/ice phase and populate the gas environment similar to other hot cores like Sgr B2, Orion KL, and G1047+003

Bratati Bhat

Papers

Identification of pre-biotic molecules containing Peptide-like bond in a hot molecular core, G10.47+0.03

Chemical Modeling for Predicting the Abundances of Certain Aldimines and Amines in Hot Cores

Identification of Prebiotic Molecules Containing Peptide-like Bonds in a Hot Molecular Core, G10.47+0.03

Identification of Methyl Isocyanate and Other Complex Organic Molecules in a Hot Molecular Core, G31.41+0.31

Chemical modeling for predicting the abundances of certain aldimines and amines in hot cores