From Cold Atomic Gas to Star Formation in Outer Galaxy

by Dr Md. Rashid (DAA, TIFR)

Wednesday 7 Oct 2026, 14:30 → 15:30 Asia/Kolkata

A-269

The outer Galaxy filaments are in a relatively low-density, low-metallicity environment, providing an opportunity to investigate how the physical condition of interstellar medium and stellar feedback regulate the formation and evolution of molecular structures. In this talk, I present two complementary observational studies using uGMRT observations to investigate both the atomic gas surrounding molecular filaments and the ongoing star-formation activity within them. I first present our HI self-absorption study towards the outer-Galaxy molecular filament G260, aimed at detecting and characterising the cold neutral medium (CNM) and examining its connection to the HI-to-H2 transition. We have carried out deep uGMRT L-band observations and developed a calibration and imaging strategy to obtain a sensitive spectral-line cube. I will discuss key challenges of the ongoing work. I then present a radio-continuum study of the G222 and G224 filaments, where uGMRT Band 4 and Band 5 observations are used to characterise radio sources and identify thermal emission associated with star formation. In G224, we identify several unresolved candidate thermal sources, including a compact source showing evidence for optically thick free-free emission, while in G222 a bright radio source near the centre of an arc-like filamentary structure may be associated with an expanding bubble compressing gas towards the filament. Together , these studies aim to connect the atomic to molecular transition, filament evolution, stellar feedback, and star formation in the distinct  environment of the outer Galaxy.