Testing the role of environmental effects on the initial mass function of low-mass stars.

In the star-formation process, the vital impact of environmental factors such as feedback from massive stars and stellar density on the form of the initial mass function (IMF) at the low-mass end is yet to be understood. Hence a systematic highly sensitive observational analysis of a sample of regions under diverse environmental conditions is essential. We analyse the IMF of eight young clusters (<5 Myr), namely IC 1848-West, IC 1848-East, NGC 1893, NGC 2244, NGC 2362, NGC 6611, Stock 8, and Cygnus OB2, which are located at the Galactocentric distance (R g) range ∼6–12 kpc along with the nearby cluster IC 348 using deep near-IR photometry and Gaia DR2. These clusters are embedded in massive stellar environments of radiation strength |$\log(L_\mathrm{FUV}/\mathrm{L}_{\odot })\, \sim 2.6$| –6.8, |$\log(L_\mathrm{EUV})\, \sim$|  42.2–50.85 photon s−1, with stellar density in the range of ∼170–1220 star pc−2. After structural analysis and field decontamination we obtain an unbiased uniformly sensitive sample of pre-main-sequence members of the clusters down to the brown-dwarf regime. The lognormal fit to the IMF of nine clusters gives the mean characteristic mass (m c) and σ of 0.32 ± 0.02 M⊙ and 0.47 ± 0.02, respectively. We compare the IMF with that of low- and high-mass clusters across the Milky Way. We also check for any systematic variation with respect to the radiation field strength and the stellar density as well with R g. We conclude that there is no strong evidence for an environmental effect in the underlying form of the IMF of these clusters. [ABSTRACT FROM AUTHOR]