Testing the role of external factors on the universal nature of Initial Mass Function Jessy Jose IISER Tirupati, Tirupati, IN
Star formation is by the process of dense molecular clouds collapsing under their own gravity forming stellar clusters ranging from low-mass stars to massive, luminous stars. In this process, the vital role of environmental factors such as feedback from massive stars, stellar density, metallicity etc. on the form of Luminosity Function (LF) and Initial Mass Function (IMF) at the very low mass end is yet to be understood. A systematic, high sensitive observational analysis of a large sample of young clusters under diverse environmental conditions across the Galaxy is an absolute essential to understand the role of external factors on the form of IMF. With this aim, we analyse the LF and IMF down to the brown dwarf regime for 9 young, rich, massive stellar clusters (age < 5Myr), located at 1-4 kpc distance (Galactocentric distance Rg ~ 6-12 kpc). We use the deep near-IR data from 4 - 8 m class Telescopes in J, H and K pass-bands along with the GAIA DR2 data for the analysis. These clusters are embedded in massive stellar environments of radiation field strength LEUV ~ 1047 to 1049 photons/sec and molecular cloud mass of 104 - 105 Msun. After a careful structural analysis, field star decontamination and completeness correction, we obtain a uniform sample of pre-main sequence members of the clusters down to brown-dwarf regime and obtain their form of LF and IMF. We compare the peak mass of IMF as well as its low-mass end with the nearby low-mass star-forming regions as well as with various super-massive clusters across Milkyway to test the role of environmental factors. This work is the first of its kind to obtain the very low mass end of the IMF of these distant clusters and to verify the role of external factors on its universality.
Caption: J vs (J-H) color-magnitude diagram of a) sample massive young cluster b) nearby control field c) after field star decontamination. The dashed curve is the peak locus of the candidate pre-main sequence (PMS) sources and the 3 σ boundaries of the sequence are shown by solid curves. The candidate PMS sources are highlighted in green color. d) IMF derived for various clusters in our list with the log-normal fit shown in solid curves. The bottom most IMF is that for the nearby low-mass cluster IC348.
Collaborators: B. Damian, IISER Tirupati, IN M.R. Samal, PRL, IN	Suggested Session: Galactic Dynamics