Kinematic study of the molecular gas associated with two cometary globules in Sh2-236
arXiv:1911.06604 · doi:10.1051/0004-6361/201935021
Abstract
Cometary globules, dense molecular gas structures exposed to the UV radiation, are found inside HII regions. Understanding the nature and origin of these structures through a kinematic study of the molecular gas is useful to advance in our knowledge of the interplay between radiation and molecular gas. Using ASTE we carried out molecular observations towards two cometary globules (Sim129 and Sim130) in the HII region Sh2-236. We mapped two regions with the 12CO J=3-2 and HCO+ J=4-3 lines. Additionally, two single pointings of C2H (N=4-3), HNC and HCN J=4-3 were observed. We combined our observations with public infrared and optical data to analyse the distribution and kinematics of the gas. We found kinematic signatures of infalling gas in the 12CO J=3-2 and C2H J=4-3 spectra towards Sim129 . We detected HCO+, HCN, and HNC J=4-3 only towards Sim130. The HCN/HNC integrated ratio of about 3 found in Sim130 suggests that the possible star formation activity within the globule has not yet ionized the gas. The location of NVSS 052255+33315, which peaks towards the brightest border of the globule, supports this scenario. The non-detection of these molecules towards Sim129 could be due to the radiation arising from the star formation activity inside this globule. The ubiquitous presence of the C2H molecule towards both globules shows the action of nearby O-B stars irradiating their external layers. Based on mid-infrared emission, we identified two new structures: a region of diffuse emission (R1) located, in projection, in front of the head of Sim129, and a pillar-like feature (P1) placed besides Sim130. Based on 12CO J=3-2, we found molecular gas associated with Sim129, Sim130, R1 and P1 at radial velocities of -1.5, -11, +10, and +4 km/s, respectively. Therefore, while Sim129 and P1 are located at the far side of the shell, Sim130 is placed at the near side, consistent with earlier results.
arXiv commentAccepted for publication in A&A
References in corpus (20)
- The Milky Way in Molecular Clouds: A New Complete CO Survey
- GLIMPSE: I. A SIRTF Legacy Project to Map the Inner Galaxy
- The Galactic O-Star Spectroscopic Survey (GOSSS). II. Bright Southern Stars
- The SCUBA Legacy Catalogue: Continuum Objects Detected by SCUBA
- Chemistry in Infrared Dark Cloud Clumps: a Molecular Line Survey at 3 mm
- Radiation driven implosion and triggered star formation
- Detailed Numerical Simulations on the Formation of Pillars around HII-regions
- The HNC/HCN Ratio in Star-Forming Regions
- Chemical Evolution in High-Mass Star-Forming Regions: Results from the MALT90 Survey
- Clumps and triggered star formation in ionised molecular clouds
- A Survey For Infall Motions Toward Starless Cores. III. CS (3-2) and DCO+(2-1) Observations
- Dynamical Models for the Formation of Elephant Trunks in H II Regions
- 3D simulations of globules and pillars formation around HII regions: turbulence and shock curvature
- The ionization fraction gradient across the Horsehead edge: An archetype for molecular clouds
- CH observations toward the Orion Bar
- 3D simulations of pillars formation around HII regions: the importance of shock curvature
- Molecular line profiles as diagnostics of protostellar collapse: modelling the `blue asymmetry' in inside-out infall
- Pre-main-sequence stars in the young open cluster NGC 1893: II. Evidence for triggered massive star formation
- Kinematic evidence for feedback-driven star formation in NGC 1893
- Molecular Line Profiles from Contracting Dense Cores