A Narrowband Imaging Search for [O III] Emission from Galaxies at z > 3

March 1999 • 1999ApJ...514...33T

Authors • Teplitz, Harry I. • Malkan, Matthew A. • McLean, Ian S.

Abstract • We present the results of a narrowband survey of quasi-stellar-object (QSO) fields at redshifts that place the [O III] (5007 Å) emission line in the Δλ/λ~1% 2.16 μm filter. We have observed 3 arcmin² and detected one emission-line candidate object in the field around PC 1109+4642. We discuss the possibilities that this object is a star-forming galaxy at the QSO redshift, z_em=3.313, or a Seyfert galaxy. In the former case, we infer a star formation rate of 170 M_solar yr^-1 for this K^'=21.3 object. The galaxy has a compact but resolved morphology, with an FWHM=0.6" or 4.2 kpc at z=3.313 (H₀=50 km s^-1 Mpc^-1 and q₀=0.5). The comoving density of such objects in QSO environments appears to be 0.0033 Mpc^-3, marginally lower (<=3 σ) than the density observed for Hα-emitters in absorption-line fields at z~2.5 but similar to the density of Lyman-break galaxies at z~3. If, on the other hand, most of the line emission is [O III] from a Seyfert 2 nucleus at z=3.31, then the high inferred volume density could imply a large evolution in the Seyfert 2 luminosity function from the current epoch. We find the field containing the object to also contain many faint extended objects in the K^' image but little significant excess over the expected number-magnitude relation. We discuss the implication of the emission line being a longer wavelength line at a lower redshift.

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Harry Teplitz

Senior Scientist