We present deep BVI observations of the core of M35 and a nearby comparison field obtained at the WIYN 3.5m telescope under excellent seeing conditions .
These observations probe to V > 26 , and display the lower main sequence in BV and VI CMDs down to V = 23.3 and 24.6 , respectively .
At these faint magnitudes the background Galactic field stars are far more numerous than the cluster stars , yet by using a smoothing technique and CMD density distribution subtraction we are able to recover the cluster fiducial main sequence and luminosity function to V = 24.6 .
We find the location of the M35 main sequence in these CMDs to be consistent with earlier work on other open clusters , specifically NGC 188 , NGC 2420 , and NGC 2477 .
We compare these open cluster fiducial sequences to stellar models by Baraffe et al .
( 1998 ) , Siess et al .
( 2000 ) , Girardi et al .
( 2000 ) , and Yi et al .
( 2001 ) and find that the models are too blue in both B - V and V - I for stars less massive than \sim 0.4 M _ { \odot } .
At least part of the problem appears to be underestimated opacity in the bluer bandpasses , with the amount of missing opacity increasing toward the blue .
M35 contains stars to the limit of the extracted main sequence , at M \approx 0.10–0.15 M _ { \odot } , suggesting that M35 may harbor a large number of brown dwarfs , which should be easy targets for sensitive near-IR instrumentation on 8–10m telescopes .
We also identify a new candidate white dwarf in M35 at V = 21.36 \pm 0.01 .
Depending on which WD models are used in interpreting this cluster candidate , it is either a very high mass WD ( 1.05 \pm 0.05 M _ { \odot } ) somewhat older ( 0.19–0.26 Gyr , 3– 4 \sigma ) than our best isochrone age ( 150 Myr ) , or it is a modestly massive WD ( 0.67–0.78 M _ { \odot } ) much too old ( 0.42–0.83 Gyr ) to belong to the cluster .
Follow-up spectroscopy is required to resolve this issue .