%0 Journal Article
%A Pascual, S.
%A Gallego Maestro, Jesús
%A Aragón Salamanca, A.
%A Zamorano Calvo, Jaime
%T Hα emitting galaxies and the star formation rate density at z ≃ 0.24
%D 2001
%@ 0004-6361
%U https://hdl.handle.net/20.500.14352/59800
%X We have carried out a survey searching for Hα emitting galaxies at z ≃ 0.24 using a narrow band filter tuned with the redshifted line. The total sky area covered was 0.19 square degrees within the redshift range 0.228 to 0.255 in a set of four fields in the ELAIS-N1 zone. This corresponds to a volume of 9.8 x 10^3 Mpc^3 and a look-back time of 3.6 Gyr when H_0 = 50 km s^-1 Mpc^-1 and q_0 = 0.5 are assumed. A total of 52 objects are selected as candidates for a broad band limiting magnitude of I ~ 22.9, plus 16 detected only in the narrow band image for a narrow band limiting magnitude for object detection of 21.0. The threshold detection corresponds to about 20 Å equivalent width with an uncertainty of ~± 10 Å. Point-like objects (15) were excluded from our analysis using CLASS STAR parameter from SExtractor. The contamination from other emission lines such as [O II] λ  3727, H _ β and [O III] λ λ  4959, 5007 at redshifts 1.2, 0.66 and 0.61 respectively is estimated, and found to be negligible at the flux limits of our sample. We find an extinction-corrected H_ α luminosity density of (5.4 ± 1.1) x 10^39 erg s^-1 Mpc^-3. This uncertainty takes into account the photometric and Poissonian errors only. Assuming a constant relation between the H_α luminosity and star formation rate, the SFR density in the covered volume is (0.043 ± 0.009) M_⨀ yr^-1 Mpc^-3. This translates to (0.037 ± 0.009) M¬_⨀ yr^-1 Mpc^-3 when the total density is corrected for the AGN contribution as estimated in the local Universe. This value is a factor ~4 higher than the local SFR density. This result needs to be confirmed by future spectroscopic follow-up observations.
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