The GUAPOS project

Astronomy and Astrophysics, vol. 677, pp. A15

Abstract

Context. The G31.41+0.31 Unbiased ALMA sPectral Observational Survey (GUAPOS) project targets the hot molecular core (HMC) G31.41+0.31 (G31) to reveal the complex chemistry of one of the most chemically rich high-mass star-forming regions outside the Galactic center (GC). Aims. In the third paper of the project we present a study of nine O-bearing (CH 3 OH, 13 CH 3 OH, CH 3 18 OH , CH 3 CHO, CH 3 OCH 3 , CH 3 COCH 3 , C 2 H 5 OH, aGg′-(CH 2 OH) 2 , and gGg′-(CH 2 OH) 2 ) and six N-bearing (CH 3 CN, 13 CH 3 CN, CH 3 13 CN, C 2 H 3 CN, C 2 H 5 CN, and C 2 H 5 13 CN) complex organic molecules toward G31. The aim of this work is to characterize the abundances in G31 and to compare them with the values estimated in other sources. Moreover, we searched for a possible chemical segregation between O-bearing and N-bearing species in G31, which hosts four compact sources as seen with higher angular resolution data. In the discussion we also include the three isomers of C 2 H 4 O 2 and the O- and N-bearing molecular species NH 2 CHO, CH 3 NCO, CH 3 C(O)CH 2 , and CH 3 NHCHO, which were analyzed in previous GUAPOS papers. Methods. Observations were carried out with the interferometer ALMA and cover the entire Band 3 from 84 to 116 GHz (~32 GHz bandwidth) with an angular resolution of 1.2″ × 1.2″ (~4400 au × 4400 au) and a spectral resolution of ~0.488 MHz (~1.3–1.7 km s −1 ). The transitions of the 14 molecular species were analyzed with the tool SLIM of MADCUBA to determine the physical parameters of the emitting gas. Moreover, we analyzed the morphology of the emission of the molecular species. Results. The values of abundances with respect to H 2 in G31 range from 10 −6 to 10 −10 for the different species. We compared the abundances with respect to methanol of O-bearing, N-bearing, and O- and N-bearing COMs in G31 with 27 other sources, including other hot molecular cores inside and outside the GC, hot corinos, shocked regions, envelopes around young stellar objects, and quiescent molecular clouds, and with chemical models. Conclusions. From the comparison with other sources there is not a unique template for the abundances in hot molecular cores, pointing toward the importance of the thermal history for the chemistry of the various sources. The abundances derived from the chemical models are in good agreement, within a factor of 10, with those of G31. From the analysis of the maps we derived the peak positions of all the molecular species toward G31. Different species peak at slightly different positions, and this, together with the different central velocities of the lines obtained from the spectral fitting, point to chemical differentiation of selected O-bearing species.

Authors 11

1. C. Mininni corresponding

   Institute for Space Astrophysics and Planetology · National Institute for Astrophysics

   Affiliation as printed

   INAF -IAPS , Via del Fosso del Cavaliere 100 , 00133 Roma , Italy

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2. M. T. Beltrán

   Arcetri Astrophysical Observatory · National Institute for Astrophysics

   Affiliation as printed

   INAF -Osservatorio Astrofisico di Arcetri , Largo E. Fermi 5 , 50125 Firenze , Italy

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3. Laura Colzi

   Centro de Astrobiología

   Affiliation as printed

   Centro de Astrobiología (CSIC , INTA) , Ctra. de Ajalvir , km. 4 , Torrejón de Ardoz , 28850 Madrid , Spain

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4. V. M. Rivilla

   Centro de Astrobiología

   Affiliation as printed

   Centro de Astrobiología (CSIC , INTA) , Ctra. de Ajalvir , km. 4 , Torrejón de Ardoz , 28850 Madrid , Spain

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5. F. Fontani

   Arcetri Astrophysical Observatory · National Institute for Astrophysics

   Affiliation as printed

   INAF -Osservatorio Astrofisico di Arcetri , Largo E. Fermi 5 , 50125 Firenze , Italy

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6. A. Lorenzani

   Arcetri Astrophysical Observatory · National Institute for Astrophysics

   Affiliation as printed

   INAF -Osservatorio Astrofisico di Arcetri , Largo E. Fermi 5 , 50125 Firenze , Italy

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7. Álvaro López-Gallifa

   Centro de Astrobiología

   Affiliation as printed

   Centro de Astrobiología (CSIC , INTA) , Ctra. de Ajalvir , km. 4 , Torrejón de Ardoz , 28850 Madrid , Spain

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8. S. Viti Aachen Leiden Observatory Huygens Laboratory

   Leiden University · Leiden Observatory · University College London

   Affiliation as printed

   Department of Physics and Astronomy , University College London , Gower Street , WC1E 6BT , London , UK

   Leiden Observatory , Leiden University , Huygens Laboratory , Niels Bohrweg 2 , 2333 CA Leiden , The Netherlands

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9. Á. Sánchez-Monge
10. P. Schilke

    University of Cologne

    Affiliation as printed

    I. Physikalisches Institut , Universität zu Köln , Zülpicher Str. 77 , 50937 Köln , Germany

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11. L. Testi

    University of Bologna

    Affiliation as printed

    Dipartimento di Fisica e Astronomia , Universitá di Bologna , Via Gobetti 93/2 , 40122 Bologna , Italy

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