# # Program information file # PROGRAM_ID 2021B025 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 Megan Tannock PROGRAM_SCICAT stellar PROGRAM_ABSTRACT_BEG We propose to use SpeX to obtain low-resolution near-infrared spectra of 36 brown dwarf [BD] candidates of the 7 Myr old 25 Orionis stellar group [25 Ori] with masses between 20 and 70 M_Jup [spectral types M6--L0] located within the group's central 0.5 degree-radius spatial overdensity. The requested observations will allow us to: [i] assign memberships to 25 Ori by comparing the data to low-resolution spectra of young and old field dwarfs with similar spectral types, [ii] derive fundamental parameters [spectral types, radius, effective temperature, bolometric luminosity, and mass] of the targets by comparing the data to atmospheric and evolutionary models, [iii] construct one of 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, [iv] compare the resulting substellar IMF with predictions from simulations of molecular cloud fragmentation to constrain the BD formation mechanism, and [v] compare the parameterization of the substellar IMF to those of other stellar associations and Galactic Disk to study the dependence on environmental conditions of the low-mass end of the IMF. 25 Ori is an ideal laboratory for such study of 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 12 h [1.5 nights] of telescope time to obtain spectra with a wavelength coverage 0.8--2.5 micron, resolution R~100, and median S/R>50 for all the targets. PROGRAM_ABSTRACT_END