Program: GN-2015A-Q-402

We request time with GNIRS on Gemini North to continue/complete our search for bright objects with featureless infrared spectra on sightlines to the Galactic center. Such objects are needed in order to more thoroughly study the interstellar environment toward and within the GC. We have used high resolution spectroscopy of H3+ and CO toward known sources in the central few tens of parsecs of the Galaxy to identify a previously unknown but apparently extensive component of the interstellar environment there, warm and diffuse gas. Evidence to date suggests that this component pervades the central molecular zone (CMZ), which extends ~200 pc from the center. However, it is necessary to identify additional smooth-spectrum sources further from the center to use as probes to determine its true extent and better characterize the gas. By using Gemini N and S and other telescopes in previous semesters to observe candidate sources identified from 2MASS and GLIMPSE photometry, we have already found several such sources and obtained striking high-resolution spectra. The requested time would allow us to survey the remaining 55 candidate objects. The program will be continued in future semesters if not completed in 2014A. Because the targets are very bright the program can be done in poor sky conditions. A similar proposal with the same targets is being submitted to Gemini South (using F-2).