# # Program information file # PROGRAM_ID 2023B041 PROGRAM_TITLE Spectroscopic-Based Substellar Initial Mass Function of 25 Ori PROGRAM_INV1 Genaro Suarez PROGRAM_INV2 Juan J. Downes PROGRAM_INV3 Carlos G. Roman-Zuniga PROGRAM_INV4 Stanimir Metchev PROGRAM_INV5 Jacqueline K. Faherty PROGRAM_SCICAT stellar PROGRAM_ABSTRACT_BEG We propose to use SpeX to obtain low-resolution near-infrared spectra of 38 brown dwarf [BD] candidates in the 25 Orionis stellar group [25 Ori; radius=0.7deg] with expected masses between 20 and 70 MJup [spectral types M6-L0]. The requested observations will allow us to: i] complete a spectroscopic survey of BD candidates in the association [could not be completed during 2021B and 2023A due to bad weather conditions], ii] assign group memberships 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 MJup, v] compare the resulting 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, and vi] validate diverse BD formation mechanisms. 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 15 h [3 half nights] of telescope time to obtain spectra with a wavelength coverage 0.8--2.5 micron, resolution R~100, and median SNR>50 for all the targets. PROGRAM_ABSTRACT_END