ATLASGAL-selected massive clumps in the inner Galaxy, II: Characterisation of different evolutionary stages and their SiO emission

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.
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Astronomy and Astrophysics - A&A, EDP Sciences, 2016, 586, pp.id.A149. <10.1051/0004-6361/201425404>
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https://hal.archives-ouvertes.fr/hal-01238870
Contributeur : Marie-Paule Pomies <>
Soumis le : lundi 7 décembre 2015 - 11:34:56
Dernière modification le : jeudi 8 septembre 2016 - 15:20:49

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T., Csengeri, S., Leurini, F., Wyrowski, J. S., Urquhart, K. M., Menten, et al.. ATLASGAL-selected massive clumps in the inner Galaxy, II: Characterisation of different evolutionary stages and their SiO emission. Astronomy and Astrophysics - A&A, EDP Sciences, 2016, 586, pp.id.A149. <10.1051/0004-6361/201425404>. <hal-01238870>

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