THE WFC3 INFRARED SPECTROSCOPIC PARALLEL (WISP) SURVEY

We present the WFC3 Infrared Spectroscopic Parallel (WISP) Survey. WISP is obtaining slitless, near-infrared grism spectroscopy of similar to 90 independent, high-latitude fields by observing in the pure-parallel mode with the Wide Field Camera Three on the Hubble Space Telescope for a total of similar to 250 orbits. Spectra are obtained with the G(102) (lambda = 0.8-1.17 mu m, R similar to 210) and G(141) grisms (lambda = 1.11-1.67 mu m, R similar to 130), together with direct imaging in the J and H bands (F110W and F140W, respectively). In the present paper, we present the first results from 19 WISP fields, covering approximately 63 arcmin(2). For typical exposure times (similar to 6400 s in G(102) and similar to 2700 s in G(141)), we reach 5 sigma detection limits for emission lines of f similar to 5 x 10(-17) erg s(-1) cm(-2) for compact objects. Typical direct imaging 5 sigma limits are 26.3 and 26.1 mag. (AB) in F110W and F140W, respectively. Restricting ourselves to the lines measured with the highest confidence, we present a list of 328 emission lines, in 229 objects, in a redshift range 0.3 < z < 3. The single-line emitters are likely to be a mix of H alpha and [O III]5007,4959 angstrom, with H alpha predominating. The overall surface density of high-confidence emission-line objects in our sample is approximately 4 per arcmin2. These first fields show high equivalent width sources, active galactic nucleus, and post-starburst galaxies. The median observed star formation rate (SFR) of our H alpha-selected sample is 4 M-circle dot yr(-1). At intermediate redshifts, we detect emission lines in galaxies as faint as H-140 similar to 25, or M-R < -19, and are sensitive to SFRs down to less than 1 M-circle dot yr(-1). The slitless grisms on WFC3 provide a unique opportunity to study the spectral properties of galaxies much fainter than L* at the peak of the galaxy assembly epoch.