A Candidate for the Most Luminous OB Association in the Galaxy
  The Milky Way harbors giant H II regions which may be powered by star
complexes more luminous than any Galactic OB association known. Being across
the disk of the Galaxy, however, these brightest associations are severely
extinguished and confused. We present a search for one such association toward
the most luminous H II region in the recent catalog by Murray and Rahman,
which, at ~9.7 kpc, has recombination rate of ~7x10^{51} sec$^{-1}$. Prior
searches have identified only small scale clustering around the rim of this
shell-like region, but the primary association has not previously been
identified. We apply a near-infrared color selection and find an overdensity of
point sources toward its southern central part. The colors and magnitudes of
these excess sources are consistent with O- and early B-type stars at
extinctions $0.96 < A_{K} < 1.2$, and they are sufficiently numerous (406 +/-
102 after subtraction of field sources) to ionize the surrounding H II region,
making this a candidate for the most luminous OB association in the Galaxy. We
reject an alternate theory, in which the apparent excess is caused by localized
extinction, as inconsistent with source demographics.
