The WFC3 infrared spectroscopic parallel (WISP) survey

Creators: Atek, H.; Malkan, M.; McCarthy, P.; Teplitz, H. I.; Scarlata, C.; Siana, B.; Henry, A. L.; Colbert, J. W.; Ross, N. R.; Bridge, C.; Bunker, A. J.; Dressler, A.; Fosbury, R. A. E.; Martin, C.; Shim, H.

Abstract

We present the WFC3 Infrared Spectroscopic Parallel (WISP) Survey. WISP is obtaining slitless, near-infrared grism spectroscopy of ~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 ~250 orbits. Spectra are obtained with the G_(102) (λ = 0.8–1.17 μm, R ~ 210) and G_(141) grisms (λ = 1.11–1.67 μm, R ~ 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 (~6400 s in G_(102) and ~2700 s in G_(141)), we reach 5σ detection limits for emission lines of f ~ 5 × 10^(−17) erg s^(−1) cm^(−2) for compact objects. Typical direct imaging 5σ 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 Hα and [O_III]5007,4959 Å, with Hα predominating. The overall surface density of high-confidence emission-line objects in our sample is approximately 4 per arcmin^2. These first fields show high equivalent width sources, active galactic nucleus, and post-starburst galaxies. The median observed star formation rate (SFR) of our Hα-selected sample is 4M_⊙ yr^(−1). At intermediate redshifts, we detect emission lines in galaxies as faint as H_(140) ~ 25, or M_R < −19, and are sensitive to SFRs down to less than 1M_⊙ 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.

Additional Information

© 2010 The American Astronomical Society. Received 2010 May 21; accepted 2010 August 27; published 2010 October 7. Based on observations made with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program 11696. We gratefully acknowledge the dedicated efforts of several staff members at the Space Telescope Institute to make the new Grism Parallel observations as successful as possible. In particular, we thank Galina Soutchkova, Iain Neill Reid, Larry Petro, Karla Peterson, Denise Taylor, Kenneth Sembach, Bill Workman, Claus Leitherer, John MacKenty, Howard Bushouse, Ron Downes, and Alan Patterson. We thank the ST-ECF team of Martin Kümmel, Harald Kuntschner and Jeremy Walsh for their help with the data reduction and spectrum extraction processes and advice about theWFC3 calibration status.We also acknowledge the important contributions to supporting parallel observations by the late Roger Doxey.

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