Emission-Line Galaxies from the NICMOS/HST GRISM Parallel Survey

P. J. McCarthy; L. Yan; W. Freudling; H. Teplitz; E. Malumuth; R. Weymann; M. Malkan; R. Fosbury; J. Gardner; L. Storrie-Lombardi; R. Thompson; R. Williams; S. Heap

doi:10.1086/307491

paper

Emission-Line Galaxies from the NICMOS/HST GRISM Parallel Survey

arXiv:astro-ph/9902347 · doi:10.1086/307491

Abstract

We present the first results of a survey of random fields with the slitless G141 ( $λ_{c} = 1.5 μ, Δ λ = 0.8 μ$ ) grism on NICMOS. Approximately 64 square arcminutes have been observed at intermediate and high galactic latitudes. The 3 $σ$ limiting line and continuum fluxes in each field vary from $7.5 \times 1 0^{- 17}$ to $1 \times 1 0^{- 17} er g / c m^{2} / sec$ and from H = 20 to 22, respectively. Our median and area weighted $3 σ$ limiting line fluxes within a 4 pixel aperture are nearly identical at $4.1 \times 1 0^{- 17} er g / c m^{2} / sec$ and are 60% deeper than the deepest narrow-band imaging surveys from the ground. We have identified 33 emission-line objects and derive their observed wavelengths, fluxes and equivalent widths. We argue that the most likely line identification is H $α$ and that the redshift range probed is from 0.75 to 1.9. The 2 $σ$ rest-frame equivalent width limits range from 9Åto 130Åwith an average of 40Å. The survey probes an effective co-moving volume of $1 0^{5} h_{50}^{- 3} M p c^{3}$ for $q_{0} = 0.5$ . Our derived co-moving number density of emission line galaxies in the range $0.7 < z < 1.9$ is $3.3 \times 1 0^{- 4} h_{50}^{3} M p c^{- 3}$ , very similar to that of the bright Lyman break objects at $z \sim 3$ . The objects with detected emission-lines have a median F160W magnitude of 20.4 (Vega scale) and a median H $α$ luminosity of $2.7 \times 1 0^{42} er g / sec$ . The implied star formation rates range from 1 to 324 M_{\odot}/yr, with an average [NII]6583,6548 corrected rate of 21 M_{\odot}/yr for H_0=50 km/s/Mpc and $q_{0} = 0.5$ (34 M_{\odot}/yr for $q_{0} = 0.1$ ).

32 pages, including 6 figures and 4 tables. Accepted for publication in the Astrophysical Journal

Emission-Line Galaxies from the NICMOS/HST GRISM Parallel Survey

Abstract

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