Star-forming galaxies at z ≈ 0.24 in the Subaru deep field and the Sloan digital sky survey

We made a search for Ha emitting galaxies at z ≈ 0.24 in the Subaru Deep Field (SDF) using an archival data set obtained with the Subaru telescope. We carefully selected Ha emitters in the narrow-band filter NB816, using B, V, R_C, i′, and z′ broad-band colors. We obtained a sample of 258 emitting galaxies with observed equivalent widths of (Hα + [N II]6548,6584) greater than 12 Å. We also analyzed a sample of Ha emitters taken from the Sloan Digital Sky Survey (SDSS) to constrain the luminous end of the Ha luminosity function. Using the same selection criteria as those for the SDF, and after excluding AGNs, we obtained 317 Hα emitting star-forming galaxies. Combining these two samples of Ha emitters found in both SDF and SDSS, we derived an Ha luminosity function with best-fit Schechter function parameters of α = -1.31_-0.17^+0.17, logφ* = -2.46_-0.40^+0.34 Mpc^-3, and log L* = 41.99_-0.07^+0.08 ergs s^-1. The extinction-corrected Ha luminosity density is 4.45_-1.75 ^+2.96 10³⁹ × 10³⁹ ergs s^-1 Mpc^-3. Using the Kennicutt relation between the Ha luminosity and star-formation rate, the star-formation rate density in the survey volume was estimated at 0.035_-0.014^+0.024 M_⊙ yr ^-1 Mpc^-3. The angular two-point correlation function of Ha emitters over 875 arcmin² at z = 0.24 was well-fitted by a power-law form with w(9) = 0.047_-0.013^+0.017 θ ^-0.66±0.08, corresponding to the correlation function ξ(r) = [r/(2.6_-0.8^+1.0 Mpc)]^-1.66±0.08. The small correlation length of Hα emitters may imply a weak clustering of active star-forming galaxies.