Multiwavelength study of the G345.5+1.5 region★
Aix-Marseille Université, CNRS, LAM, Laboratoire d’Astrophysique de Marseille, Marseille,
2 National Centre for Nuclear Research, ul. Hoża 69, 00-681 Warszawa, Poland
3 Joint ALMA Observatory (JAO), Alonso de Córdova 3107, Vitacura, Santiago, Chile
4 Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile
5 Jodrell Bank Centre for Astrophysics, School of Physics & Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
6 Instituto Argentino de Radioastronomía, CONICET, CCT-La Plata. C.C.5., 1894 Villa Elisa, Argentina
7 European Southern Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile
Accepted: 26 January 2019
Context. The star formation process requires the dust and gas present in the Milky Way to self-assemble into dense reservoirs of neutral material where the new generation of stars will emerge. Star-forming regions are usually studied in the context of Galactic surveys, but dedicated observations are sometimes needed when the study reaches beyond the survey area.
Aims. A better understanding of the star formation process in the Galaxy can be obtained by studying several regions. This allows increasing the sample of objects (clumps, cores, and stars) for further statistical works and deeper follow-up studies. Here, we studied the G345.5+1.5 region, which is located slightly above the Galactic plane, to understand its star formation properties.
Methods. We combined Large Apex BOlometer CAmera (LABOCA) and 12CO(4−3) transition line (NANTEN2) observations complemented with the Hi-GAL and Spitzer-GLIMPSE surveys to study the star formation toward this region. We used the Clumpfind algorithm to extract the clumps from the 870 μm and 12CO(4−3) data. Radio emission at 36 cm was used to estimate the number of H II regions and to remove the contamination from the free–free emission at 870 μm. We employed color–color diagrams and spectral energy distribution (SED) slopes to distinguish between prestellar and protostellar clumps. We studied the boundedness of the clumps through the virial parameter. Finally, we estimated the star formation efficiency (SFE) and star formation rate (SFR) of the region and used the Schmidt–Kennicutt diagram to compare its ability to form stars with other regions of the Galactic plane.
Results. Of the 13 radio sources that we found using the MGPS-2 catalog, 7 are found to be associated with H II regions corresponding to late-B or early-O stars. We found 45 870 μm clumps with diameters between 0.4 and 1.2 pc and masses between 43 M⊙ and 3923 M⊙, and 107 12CO clumps with diameters between 0.4 and 1.3 pc and masses between 28 M⊙ and 9433 M⊙. More than 50% of the clumps are protostellar and bounded and are able to host (massive) star formation. High SFR and SFR density (ΣSFR) values are associated with the region, with an SFE of a few percent.
Conclusions. With submillimeter, CO transition, and short-wavelength infrared observations, our study reveals a population of massive stars, protostellar and bound starless clumps, toward G345.5+1.5. This region is therefore actively forming stars, and its location in the starburst quadrant of the Schmidt–Kennicutt diagram is comparable to other star-forming regions found within the Galactic plane.
Key words: ISM: clouds / HII regions / ISM: general
The LABOCA and CO maps, and Tables A.1–A.3 are also available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (18.104.22.168) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/623/A141
© ESO 2019