Is the Slope of the Hyades IMF Rising Below $M \sim 0.1 M_{\sun}$?
Session 103 -- Open and Globular Clusters
Display presentation, Thursday, 12, 1995, 9:20am - 6:30pm

## [103.03] Is the Slope of the Hyades IMF Rising Below $M \sim 0.1 M_{\sun}$?

C. Bryja (Mankato State U.)

We have used the Minnesota Automated Plate Scanner to compare Palomar Schmidt plates of the Hyades region from three different epochs--- generating a list of candidate members of the Hyades cluster selected by color and proper motion which includes stars complete to more than a magnitude fainter than previous work. Adopting the most conservative possible value for the number of true Hyads found, and combining our results with the survey of Reid (1992, MNRAS , 257, 257), we derive the form of the cluster luminosity function (LF) down to luminosities corresponding to masses of $M \sim 0.1 M_{\sun}$. We find that the LF matches best to a moderately increasing mass function with a power law index of $\alpha < 1.0$ in the mass range $0.3 \mathrel{\hbox{\rlap{\hbox{\lower4pt\hbox{$\sim$}}} \hbox{$>$}}} M/M_{\sun} \mathrel{\hbox{\rlap{\hbox{\lower4pt\hbox{$\sim$}}} \hbox{$>$}}} 0.2$ increasing to $\alpha \approx 1.5$ below $M \sim 0.2 M_{\sun}$. Within the statistical uncertainties, this increase may be even more dramatic below $M \sim 0.15 M_{\sun}$. We note that if lower mass stars were preferentially evaporated from the cluster, our observed mass function would have a lesser slope than the original IMF. If $\alpha > 2$ for the IMF below the hydrogen burning limit ($M \approx 0.08 M_{\sun}$), then brown dwarfs would have initially been (and may still be) a significant contributer to the Hyades' total mass.