PROBING THE PHYSICAL CONDITIONS AND STAR FORMATION PROCESSES IN GALACTIC H II REGION S305
Date & Time :
To probe physical processes, we present a multi-scale and multi-wavelength observations of a Galactic H II region S305, which is excited by massive O8.5V (VM4) and O9.5V (VM2) stars. Infrared images display an extended sphere-like shell (extension ~7.5pc; at Td = 17.5 -27 K) enclosing the S305 region (size ~5.5 pc; age ~1.5 Myr). Regularly spaced molecular condensations and dust clumps are investigated toward the edges of the infrared shell, where the PAH and H2 emission is also observed. The molecular line data show a signature of an expanding shell of molecular gas in S305. GMRT 610 and 1280 continuum maps reveal at least four ionized clumps powered by young B-type stars (age < 10^ 5 years) around O-type stars that are surrounded by a horseshoe envelope (extension ~2.3 pc). A molecular gas deficient region/cavity is identified toward the center of the horseshoe envelope, which is well traced with the PAH, H2, molecular, and dust emission. The edges of the infrared shell are found to be located in the front of the horseshoe envelope. The dynamical ages of the ionized clumps are shorter than that of the S305 H II region. All these outcomes show the observational evidence of positive feedback of O-type stars in S305. Non-thermal radio emission is detected in S305 with a spectral index ranging from -1 to 1. It is explained by a combination of soft synchrotron emission and either thermal contamination at high frequencies or a suppression of the low-frequency emission by the Razin-Tsytovich effect.
About Speaker :
Rakesh is a PhD student in ARIES. This is a talk for paper submission in paid journal.