A Fabry-Pérot Imaging Search for Lyα Emission in Quasar Absorbers at z ~ 2.4

We have carried out a deep narrowband imaging survey of six fields with heavy-element quasar absorption lines, using the Goddard Fabry-Pérot (FP) system at the Apache Point Observatory (APO) 3.5 m telescope. The aim of these observations was to search for redshifted Lyα emission from the galaxies underlying the absorbers at z = 2.3-2.5 and their companion galaxies. The 3 σ sensitivity levels ranged between 1.9 × 10-17 and 5.4 × 10-17 ergs s-1 cm-2 in observed-frame Lyα flux. No significant Lyα emitters were detected at a level >3 σ. The absence of significant Lyα emission implies limits on the star formation rate (SFR) of 0.9-2.7 M☉ yr-1 per 2 pixel × 2 pixel region, if no dust attenuation is assumed. We compare our results with those from other emission-line studies of absorber fields and with predictions for the global average SFR based on the models of cosmic chemical evolution. Our limits are among the tightest existing constraints on Lyα emission from galaxies in absorber fields, but they are consistent with many other studies. In the absence of dust attenuation, these studies suggest that SFRs in a large fraction of objects in the absorber fields may lie below the global mean SFR. However, it is possible that dust attenuation is responsible for the low emission-line fluxes in some objects. It is also possible that the star-forming regions are compact and at smaller angular separations from the quasar than the width of our point-spread function and get lost in the quasar emission. We outline future observations that could help to distinguish between the various possibilities.

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