Early Evolutionary Stages of Sub-stellar Mass Objects

• Applicant: Basmah Riaz, Ph.D.
• Subject Area: Astrophysics and Astronomy
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 402837297

Over the last decade, extensive observational and theoretical effort has been invested to understand the early stages of evolution of Sun-like stars. Similar studies are still very sparse for stars at the very low-mass end, with masses less than one-tenth of the mass of the Sun. Often termed as the least massive known ‘stars’, brown dwarfs (BDs) are sub-stellar objects that have insufficient mass to burn hydrogen in their cores and shine like stars. Yet, these faint astronomical objects are found to be as numerous as Sun-like stars in various star-forming regions, thereby making them an equally vital constituent of our Galaxy. Any research on star formation in the Milky Way is thus incomplete without gaining a comprehensive knowledge on the early stages of evolution of the least massive but ubiquitous component of the Galaxy. My proposed DFG project is an extensive observational and theoretical investigation of the diverse properties of BDs during their early Class I stage of evolution. The objectives of the project are to combine high-quality multi-wavelength observations with newly developed state-of-the-art physical and chemical models in order to (a) conduct an in-depth study of the physical and chemical structure, kinematics, and chemical composition in Class I BDs, and (b) investigate the fundamental role played by accretion and outflow processes in shaping the evolution of a BD during its early evolutionary stages. With the advent of high-class telescopes and instruments of unparalleled sensitivities, it is now feasible to probe deep into the early evolutionary stages of such faint systems. To conduct this study, I have obtained several multi-wavelength observations for a statistically large sample of Class I BDs, and have access to new, state-of-the art models developed exclusively for early-stage BDs, which will allow a successful completion of the different tasks in the project. This unique survey will look into the analogies in the various characteristics of BDs and Sun-like stars during their early evolutionary stages. The fundamental questions that the project aims to answer are: Is the initial chemical composition and the internal physical and chemical structure of Class I BDs similar to Class I Sun-like stars? Are the accretion and outflow processes during the early evolutionary phases as intense for BDs as observed for Sun-like stars? Is there a continuity in the formation and early evolutionary processes across the stellar/sub-stellar boundary, or do the initial star-formation conditions in the Galaxy differ with the stellar mass?The proposed DFG project will deliver the first of its kind results on the fundamental properties of sub-stellar objects during their initial formation stages. It will provide the first detailed derivation of the physical and chemical composition of an early-stage BD, and will advance our understanding of molecular cloud fragmentation and star formation in the Galaxy towards the lowest mass end.

• DFG Programme: Research Grants