Abstract
The processes leading to the birth of high-mass stars are poorly understood. We characterise here a sample of 430 massive clumps from the ATLASGAL survey, which are representative of different evolutionary stages. To establish a census of molecular tracers of their evolution we performed an unbiased spectral line survey covering the 3-mm atmospheric window between 84-117 GHz with the IRAM 30m. A smaller sample of 128 clumps has been observed in the SiO (5-4) transition with the APEX telescope to complement the SiO (2-1) line and probe the excitation conditions of the emitting gas, which is the main focus of the current study. We report a high detection rate of >75% of the SiO (2-1) line and a >90% detection rate from the dedicated follow-ups in the (5-4) transition. The SiO (2-1) line with broad line profiles and high detection rates, is a powerful probe of star formation activity, while the ubiquitous detection of SiO in all evolutionary stages suggests a continuous star formation process in massive clumps. We find a large fraction of infrared-quiet clumps to exhibit SiO emission, the majority of them only showing a low-velocity component (FWHM~5-6 km/s) centred at the rest velocity of the clump. In the current picture, where this is attributed to low-velocity shocks from cloud-cloud collisions, this can be used to pinpoint the youngest, thus, likely prestellar massive structures. Based on the line ratio of the (5-4) to the (2-1) line, our study reveals a trend of changing excitation conditions that lead to brighter emission in the (5-4) line towards more evolved sources. Our analysis delivers a more robust estimate of SiO column density and abundance than previous studies and questions the decrease of jet activity in massive clumps as a function of age.
Highlights
The origin of high-mass stars is still an enigma in modern astrophysics
We define a representative sample of massive clumps in different evolutionary stages selected from the Atacama Pathfinder EXperiment (APEX) Telescope Large Area Survey of the Galaxy (ATLASGAL), from which we aim to establish a census of molecular tracers of their evolution
Based on the ATLASGAL survey, we identified a representative sample of massive clumps located throughout the inner Galaxy
Summary
The origin of high-mass stars is still an enigma in modern astrophysics. To reveal the processes playing a major role in their formation, first the origin of their mass reservoir, and, the origin of massive clumps, needs to be studied. Deg area of the inner Galaxy (Schuller et al 2009; Csengeri et al 2014), provides unprecedented statistics of massive clumps hosting various evolutionary stages of embedded high-mass (proto-)stars. Larger samples covering a broad range of evolutionary stages are needed for statistical analysis of their molecular properties. Codella et al (1999), Miettinen et al (2006), Motte et al (2007), Sakai et al (2010), López-Sepulcre et al (2011), Sanhueza et al (2012), Gerner et al (2014) which cover and compare various evolutionary stages, with the largest sample of 159 clumps studied in 37 IRDCs by Sanhueza et al (2012) Examples of these studies are e.g. Codella et al (1999), Miettinen et al (2006), Motte et al (2007), Sakai et al (2010), López-Sepulcre et al (2011), Sanhueza et al (2012), Gerner et al (2014) which cover and compare various evolutionary stages, with the largest sample of 159 clumps studied in 37 IRDCs by Sanhueza et al (2012)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
