M Dwarfs fromHubble Space TelescopeStar Counts. III. The Groth Strip

We analyze the disk M dwarfs found in 31 new elds observed with the Wide Field Camera 2 (WFC2) on the Hubble Space T elescope, together with the sample previously analyzed from 22 WFC2 elds and 162 prerepair Planetary Camera 1 elds. The new observations, which include the 28 high-latitude elds comprising the Large Area Multi-Color Survey (Groth Strip), increase the total sample to 337 stars, and more than double the number of late M dwarfs from 23 to 47. The mass function changes (M V [ 13.5) slope at M D 0.6 from a near-Salpeter power-law index of a \ [1.21 to a \ 0.44. In both regimes, M _ , the mass function at the Galactic plane is given by