The low-mass IMF in the ρ Ophiuchi cluster

We compare the methods for estimating the masses of young, embedded stars developed by Comerón et al. (1993) and by Strom et al. (1995) and show them to be in good agreement. Spectra in the 2 μm region of six low-mass objects are also in agreement with the mass estimates using these methods. The spectrum of a brown dwarf candidate can be used to place an upper limit on its mass of 60% of the minimum required for hydrogen burning. This limit is independent of the photometric analysis, which we update in this paper to make use of new calculations of brown dwarf evolution. This new analysis indicates a mass for this object of roughly 40% of the minimum hydrogen-burning mass, supporting the possibility that it is a young brown dwarf. The initial mass functions (IMFs) obtained for low-mass stars in the ρ Ophiuchi cloud cores by Comerón et al. (1993) and by Strom et al. (1995) also agree well. The data have been combined to increase the statistical weight of the determination of the IMF. The IMF between 0.03 and 1 M_⊙ can be fitted satisfactorily by a power law with index in linear mass units of ∼ -1.1, or in logarithmic mass units of ∼ -0.1.