2017/06/13 by S. Paron, S. Parón, M. Celis Peña +6
Chemistry · Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Galaxy #H II region #Implosion #Interstellar medium #Molecular Spectroscopy and Structure #Molecular cloud #Outflow #Physics #Pillar #Plasma #Star formation #Stars #Stellar, planetary, and galactic studies #Telescope #Young stellar object #astro-ph.GA
paper · pdf · doi:10.1093/mnras/stx1486
Accepted in MNRAS (2017 June 13)
arxiv created 2017/06/13 · openalex publication_date 2017/06/14 · arxiv updated 2017/08/02 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
At the interface of H ii regions and molecular gas, peculiar structures appear, some of them with pillar-like shapes. Understanding their origin is important for characterizing triggered star formation and the impact of massive stars on the interstellar medium. In order to study the molecular environment and influence of radiation on two pillar-like features related to the H ii region G46.5–0.2, we performed molecular line observations with the Atacama Submillimeter Telescope Experiment and spectroscopic optical observations with the Isaac Newton Telescope. From the optical observations, we identified the star that is exciting the H ii region as spectral type O4–6. The molecular data allowed us to study the structure of the pillars and an HCO+ cloud lying between them. In this HCO+ cloud, which has no well-defined 12CO counterpart, we found direct evidence of star formation: two molecular outflows and two associated near-IR nebulosities. The outflow axis orientation is perpendicular to the direction of the radiation flow from the H ii region. Several Class I sources are also embedded in this HCO+ cloud, showing that it is usual that young stellar objects (YSOs) form large associations occupying a cavity bounded by pillars. On the other hand, it was confirmed that the radiation-driven implosion (RDI) process is not occurring in one of the pillar tips.