The Hα Luminosity Function and Star Formation Rate at z ≈ 0.24 Based on Subaru Deep Imaging Data

We have carried out a deep imaging survey for Hα-emitting galaxies at z ≈ 0.24 using a narrowband filter tuned with the redshifted line. The total sky area covered is 706 arcmin2 within a redshift range from 0.234 to 0.252 (δz = 0.018). This corresponds to a volume of 3.9 × 103 Mpc3 when Ωmatter = 0.3, ΩΛ = 0.7, and H0 = 70 km s-1 Mpc-1 are adopted. We obtain a sample of 348 Hα-emitting galaxies whose observed emission-line equivalent widths are greater than 12 Å. We find an extinction-corrected Hα luminosity density of 10 ergs s-1 Mpc-3. Using the Kennicutt relation between the Hα luminosity and the star formation rate, the star formation rate density in the covered volume is estimated to be 0.036 M☉ yr-1 Mpc-3. This value is higher by a factor of 3 than the local star formation rate density.