Triggered massive star formation associated with the bubble Hii region Sh2-39 (N5)

BRONFMAN, L.; GROMADSKI, M; CAPPA, C. E.; BORISSOVA, J.; DURONEA, N. U.

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Año: 2017 vol. 606

0004-6361

Aims. Aiming at studying the physical properties of Galactic IR bubbles and to explore their impact in triggering massive starformation, we perform a multiwavelength analysis of the Hii region bubble Sh2-39 (N5) and its environs.Methods. To analyze the molecular gas we use CO(3-2) and HCO+(4-3) line data obtained with the on-the-fly technique from theASTE telescope. To study the distribution and physical characteristics of the dust, we make use of archival data from ATLASGAL,Herschel, and MSX, while the ionized gas was studied making use of NVSS an image. We use public WISE, Spitzer, and MSXpoint source catalogs to search for infrared candidate YSOs in the region. To analyse the stellar cluster [BDS2003]6 we use IRspectroscopic data obtained with the ARCoIRIS spectrograph, mounted on Blanco 4-m Telescope at CTIO, and new available IR Ksband observations.Results. The new ASTE observations allowed the molecular gas component in the velocity range from 30 km s−1 to 46 km s−1,associated to Sh2-39, to be studied in detail. The morphology of the molecular gas suggests that the ionized gas is expanding againstits parental cloud. We have identified four molecular clumps, that were likely formed by the expansion of the ionization front, anddetermined some of their physical and dynamical properties. Clumps having HCO+ and 870 μm counterparts show evidence ofgravitational collapse.We identified several candidate YSOs across the molecular component. Their spatial distribution, as well as thefragmentation time derived for the collected layers of molecular gas, suggest that massive star formation might have been triggeredby the expansion of the nebula via the collect and collapse mechanism. The spectroscopical distance obtained for the stellar cluster[BDS2003]6, placed over one of the collapsing clumps in the border of the Hii region, reveals that this cluster is physically associatedwith the neabula and gives more support to the triggered massive star formation scenario. A radio continuum data analysis indicatesthat the nebula is older and expands at lower velocity than typical IR Galactic bubbles.Key words. ISM: molecules, ISM: Hii regions, ISM:individual object: Sh2-39, stars: star formation.