G331.512-0.103:An Interstellar Laboratory for Molecular Synthesis. I. the Ortho-to-para Ratios for CH₃OH and CH₃CN

Spectral line surveys reveal rich molecular reservoirs in G331.512-0.103, a compact radio source in the center of an energetic molecular outflow. In this first work, we analyse the physical conditions of the source by means of CH$_3$OH and CH$_3$CN. The observations were performed with the APEX telescope. Six different system configurations were defined to cover most of the band within (292-356) GHz; as a consequence we detected a forest of lines towards the central core. A total of 70 lines of $A/E$-CH$_3$OH and $A/E$-CH$_3$CN were analysed, including torsionally excited transitions of CH$_3$OH ($\nu_t$=1). In a search for all the isotopologues, we identified transitions of $^{13}$CH$_3$OH. The physical conditions were derived considering collisional and radiative processes. We found common temperatures for each $A$ and $E$ symmetry of CH$_3$OH and CH$_3$CN; the derived column densities indicate an $A/E$ equilibrated ratio for both tracers. The results reveal that CH$_3$CN and CH$_3$OH trace a hot and cold component with $T_k \sim$ 141 K and $T_k \sim$ 74 K, respectively. In agreement with previous ALMA observations, the models show that the emission region is compact ($\lesssim$ 5.5 arcsec) with gas density $n$(H$_2$)=(0.7-1) $\times$ 10$^7$ cm$^{-3}$. The CH$_3$OH/CH$_3$CN abundance ratio and the evidences for pre-biotic and complex organic molecules suggest a rich and active chemistry towards G331.512-0.103.Comment: 15 pages, 7 figures, 7 tables. Accepted for publication in The Astrophysical Journa

Resolving the circumstellar environment of the galactic B[e] supergiant atar MWC 137 from large to small scales

The Galactic object MWC 137 has been suggested to belong to the group of B[e] supergiants. However, with its large-scale optical bipolar ring nebula and high-velocity jet and knots, it is a rather atypical representative of this class. We performed multiwavelength observations spreading from the optical to the radio regimes. Based on optical imaging and long-slit spectroscopic data, we found that the northern parts of the large-scale nebula are predominantly blueshifted, while the southern regions appear mostly redshifted. We developed a geometrical model consisting of two double cones. Although various observational features can be approximated with such a scenario, the observed velocity pattern is more complex. Using near-infrared integral-field unit spectroscopy, we studied the hot molecular gas in the vicinity of the star. The emission from the hot CO gas arises in a small-scale disk revolving around the star on Keplerian orbits. Although the disk itself cannot be spatially resolved, its emission is reflected by the dust arranged in arc-like structures and the clumps surrounding MWC 137 on small scales. In the radio regime, we mapped the cold molecular gas in the outskirts of the optical nebula. We found that large amounts of cool molecular gas and warm dust embrace the optical nebula in the east, south, and west. No cold gas or dust was detected in the north and northwestern regions. Despite the new insights into the nebula kinematics gained from our studies, the real formation scenario of the large-scale nebula remains an open issue.Fil: Kraus, Michaela. Astronomický Ústav, Akademie Véd Ceské Republiky;Fil: Liimets, Tiina. Tarty Observatory, Tartumaa, Estonia;Fil: Cappa, Cristina Elisabeth. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: Cidale, Lydia Sonia. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Nickeler , Dieter H.. Astronomický Ústav, Akademie Véd Ceské Republiky;Fil: Duronea, Nicolas Urbano. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: Arias, Maria L.. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica la Plata; ArgentinaFil: Gunawan, Diah S.. Universidad de Valparaíso; ChileFil: Oksala, Mary E.. California Lutheran University; Estados UnidosFil: Borges Fernandes, Marcelo. Ministério de Ciencia, Tecnologia e Innovacao. Observatorio Nacional; Brasi