A search for Hα emission in high-metallicity damped Lyman α systems at z ~ 2.4

Abstract

We report on a sensitive search for redshifted Ha line-emission from three high-metallicity damped Lyα absorbers (DLAs) at z ≈ 2.4 with the Near-infrared Integral Field Spectrometer (NIFS) on the Gemini-North telescope, assisted by the ALTtitude conjugate Adaptive optics for the InfraRed (ALTAIR) system with a laser guide star. Within the NIFS field-of-view, ≈3.22 arcsec × 2.92 arcsec corresponding to ≈25 kpc × 23 kpc at z = 2.4, we detect no statistically significant line-emission at the expected redshifted Hα wavelengths. The measured root-mean-square noise fluctuations in 0.4 arcsec apertures are 1-3 × 10-18 erg s-1 cm-2. Our analysis of simulated, compact, line-emitting sources yields stringent limits on the star formation rates (SFRs) of the three DLAs, < 2.2M⊙ yr-1 (3σ) for two absorbers, and < 11M⊙ yr-1 (3σ) for the third, at all impact parameters within ≈12.5 kpc to the quasar sightline at the DLA redshift. For the third absorber, the SFR limit is < 4.4 M⊙ yr-1 for locations away from the quasar sightline. These results demonstrate the potential of adaptive optics-assisted, integral field unit searches for galaxies associated with high-z DLAs.