Study of low mass stars and brown dwarfs in star forming regions of diverse environments

Abstract

The formation and evolution of low-mass stars and brown dwarfs is an intricate process orchestrated by the environmental conditions in which they form. As a natural byproduct of this process, circumstellar disks are formed, whose dynamic relationship with the environment plays a pivotal role in determining the fate of the star and the timescale for planet formation. While low-mass stars are a dominant product of the star formation process, brown dwarfs occupy a unique position, bridging the gap between newlinelow-mass stars and planets. In this thesis, we have examined the low-mass stars and brown dwarfs in young clusters located at different distances with diverse UV radiation felds and stellar densities to decode the role of environment in shaping the IMF, its inand#64258;uence on disk evolution and to understand the formation of brown dwarfs. We have targeted three young star forming regions for the newlinestudy namely and#963; Orionis, twin clusters IC 1848-East and West, and IC 1396 using deep multi-wavelength photometry as well as near-IR spectroscopy with 4m and 10m class facilities. For the and#963; Orionis cluster we used deep CFHT-WIRCAM near-IR data and the novel water-band photometry technique along with Gaia DR3 to identify the candidate low-mass members. Spectroscopic follow-up observations conducted with IRTF-SpeX validated the selection of the candidates by this technique with a 100% effcacy. We then compiled a comprehensive membership catalog for a mass range and#8764;19-0.004 Mand#8857;. The form of the stellar-substellar IMF was found to be consistent with other nearby star forming regions suggesting a lack of signifcant environmental inand#64258;uence. Further, we analysed the evolutionary class of the members based on the mid-IR slope of the SED to study their disk properties. We estimated the disk fraction of the low-mass sources to be consistent with other star form ing regions considering the age of the cluster. This showed that in this region, external photoevaporation does not play a major role in the inner disk evolution.