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 ( H \alpha , [ O III ] , H \beta , or [ O II ] ) in the bandpass of the narrowband filter .
The area weighted line flux limit over the entire survey was 3.4 \times 10 ^ { -16 } erg cm ^ { -2 } s ^ { -1 } ( 3 \sigma ) , while the most sensitive limits reached 1.4 \times 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 \times 10 ^ { 5 } Mpc ^ { 3 } .
Considering only H \alpha 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 \times 10 ^ { 4 } Mpc ^ { 3 } to a volume-weighted average star formation rate of 112 M _ { \odot } yr ^ { -1 } ( for H _ { 0 } = 50 km s ^ { -1 } Mpc ^ { -1 } , \Omega _ { 0 } = 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 .