# # Program information file # PROGRAM_ID 2023A034 PROGRAM_TITLE Spectroscopic-Based Substellar Initial Mass Function of 25 Ori PROGRAM_INV1 Genaro Suarez PROGRAM_INV2 Stanimir Metchev PROGRAM_INV3 Juan J. Downes PROGRAM_INV4 Carlos G. Roman-Zuniga PROGRAM_INV5 Jacqueline K. Faherty PROGRAM_SCICAT stellar PROGRAM_ABSTRACT_BEG We propose to use SpeX to obtain low-resolution near-infrared spectra of 20 brown dwarf [BD] candidates in the 25 Orionis stellar group [25 Ori] overdensity [radius=0.5 deg] with expected masses between 20 and 70 M_jup [spectral types M6--L0]. The requested observations will allow us to: i] complete a spectroscopic survey of BD candidates in the 25 Ori overdensity, ii] assign memberships to 25 Ori by comparing the data to low-resolution spectra of young and old field dwarfs with similar spectral types, iii] derive fundamental parameters [spectral type, radius, effective temperature, bolometric luminosity, and mass] of the targets by comparing the data to atmospheric and evolutionary models, iv] construct one of the very few substellar initial mass functions [IMFs] of a stellar association based on a statistically complete sample of spectroscopically confirmed BDs with m>20 M_jup, v] constrain BD formation mechanisms by assessing how well they reproduce the resulting substellar IMF, and vi] compare the parameterization of the substellar IMF to those in other stellar associations and the Galactic Disk to study the dependence on environmental conditions of the low-mass end of the IMF. 25 Ori is an ideal laboratory for the proposed study on BDs because it is relatively close, presents a very low interstellar extinction, and is one of the most populous ~10 Myr stellar groups within 500 pc. For the observations we request 9 hrs [1 night] of telescope time to obtain spectra with a wavelength coverage 0.8-2.5 microns, resolution R~100, and median SNR>50 for all the targets. PROGRAM_ABSTRACT_END