2019A&A...623A.141F

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 870µm and ¹²CO(4-3) data. Radio emission at 36 cm was used to estimate the number of HII regions and to remove the contamination from the free-free emission at 870µm. 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 HII regions corresponding to late-B or early-O stars. We found 45 870µm clumps with diameters between 0.4 and 1.2pc and masses between 43M_☉ and 3923M_☉, and 107 ¹²CO clumps with diameters between 0.4 and 1.3pc and masses between 28M_☉ and 9433M_☉. More than 50% of the clumps are protostellar and bounded and are able to host (massive) star formation. High SFR and SFR density (Σ_SFR) 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.