Rodrigo Cabral Fontes
A first estimation of the IMF in Orion OB1b from 0.05 Msun to 8 Msun using
public surveys
The initial mass function (IMF) is a fundamental result of the star formation process and a crucial quantity in nearly all areas of astrophysics. The nearby (~400 pc) Orion star-forming complex includes stars and brown dwarfs spanning wide ranges of mass and age (~1-10 Myr). Slightly evolved populations like 25 Ori (Orion OB1a), σ Ori (Orion OB1b), and Collinder 69 (λ Ori) have relatively low extinctions, making them ideal for accurate IMF determinations in the low-mass regime. In this work, we present the IMF determination of kinematically distinct stellar populations within Orion OB1b in the mass range 0.05 < M/Msun< 8. The groups were selected by employing astrometric and photometric data from Gaia DR3, while masses and ages were determined using stellar structure and evolution models from the literature. We corrected for the contamination by field stars and main observational biases using spectroscopically confirmed members as a control sample. We recovered the distance and age multi-modality towards OB1b reported in literature, which could suggest separate origins for the different groups. The resulting IMFs were fitted to a lognormal function in the subsolar range, a tapered power-law in the whole mass range, and a segmented power-law. The obtained parameters are consistent with findings for λ Ori, σ Ori, and 25 Ori, supporting the scenario of a common underlying IMF for most of Orion’s populations.
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A first estimation of the IMF in Orion OB1b from 0.05 Msun to 8 Msun using public surveys
