A Narrowband Imaging Survey for High Redshift Galaxies in the near Infrared

A narrowband imaging survey of 276 square minutes of arc was carried out at near infrared wavelengths to search for emission line objects at high redshifts. Most of the fields contained a known quasar or radio galaxy at a redshift that placed one of the strong, restframe optical emission lines (Hα, [O III], Hβ, or [O II]) in the bandpass of the narrowband filter. The area weighted line flux limit over the entire survey was 3.4 × 10−16 erg cm−2 s−1 (3σ), while the most sensitive limits reached 1.4×10−16 erg cm−2 s−1. Integrating the volume covered by all four optical emission lines in each image yields a total comoving volume surveyed of 1.4 × 105 Mpc3. Considering only Hα emission in the K band (2.05 < z < 2.65), where the survey is most sensitive, the survey covered a comoving volume of 3.0 × 104 Mpc3 to a volumeweighted average star formation rate of 112M⊙ yr −1 (for H0 = 50 km s −1 Mpc−1, Ω0 = 1). This is the most extensive near-infrared survey which is deep enough to have a reasonable chance at detecting strong line emission from an actively star-forming population of galaxies, when measured against simple models of galaxy formation. One emission line candidate was identified in this survey, and subsequently confirmed spectroscopically. Subject headings: cosmology: observations — early universe — galaxies: formation — infrared: galaxies This work is partially based on observations collected at the European Southern Observatory, La Silla, Chile.