We present a tally of Milky Way late-type dwarf stars in 68 WFC3 pure-parallel fields ( 227 arcmin ^ { 2 } ) from the Brightest of Reionizing Galaxies ( BoRG ) survey for high-redshift galaxies .
Using spectroscopically identified M-dwarfs in two public surveys , the CANDELS and the ERS mosaics , we identify a morphological selection criterion using the half-light radius ( r _ { 50 } ) , a near-infrared J-H , G-J color region where M-dwarfs are found , and a V-J relation with M-dwarf subtype .

We apply this morphological selection of stellar objects , color-color selection of M-dwarfs and optical-near-infrared color subtyping to compile a catalog of 274 M-dwarfs belonging to the disk of the Milky Way with a limiting magnitude of m _ { F 125 W } < 24 ( AB ) .
Based on the M-dwarfs statistics , we conclude that ( a ) the previously identified North/South discrepancy in M-dwarf numbers persists in our sample ; there are more M-dwarfs in the Northern fields on average than in Southern ones , ( b ) the Milky Way ’ s single disk scale-height for M-dwarfs is 0.3-4 kpc , depending on sub-type , ( c ) the scale-height depends on M-dwarf subtype with early type ( M0-4 ) high scale-height ( z _ { 0 } = 3 - 4 kpc ) and later types M5 and above in the thin disk ( z _ { 0 } = 0.3 - 0.5 kpc ) .
( d ) a second component is visible in the vertical distribution , with a different , much higher scale-height in the Southern Fields compared to the Northern ones .
We report the M-dwarf component of the Sagittarius stream in one of our fields with 11 confirmed M-dwarfs , 7 of which are at the stream ’ s distance In addition to the M-dwarf catalog , we report the discovery of 1 T-dwarf and 30 L-dwarfs from their near-infrared colors .
The dwarf scale-height and the relative low incidence in our fields of L- and T-dwarfs in these fields makes it unlikely that these stars will be interlopers in great numbers in color-selected samples go high-redshift galaxies .
The relative ubiquity of M-dwarfs however will make them ideal tracers of Galactic Halo substructure with EUCLID and reference stars for JWST observations .