Properties of galaxies at the faint end of the Hαluminosity function atz~ 0.62

Context. Studies measuring the star formation rate density, luminosity function, and properties of star-forming galaxies are numerous. However, it exists a gap at 0.5 z α -based studies. Aims. Our main goal is to study the properties of a sample of faint H α emitters at z ~ 0.62. We focus on their contribution to the faint end of the luminosity function and derived star formation rate density, characterising their morphologies and basic photometric and spectroscopic properties. Methods. We use a narrow-band technique in the near-infrared, with a filter centred at 1.06 μ m. The data come from ultra-deep VLT/HAWK-I observations in the GOODS-S field with a total of 31.9 h in the narrow-band filter. In addition to our survey, we mainly make use of ancillary data coming from the CANDELS and Rainbow Cosmological Surveys Database, from the 3D-HST for comparison, and also spectra from the literature. We perform a visual classification of the sample and study their morphologies from structural parameters available in CANDELS. In order to obtain the luminosity function, we apply a traditional V / V max method and perform individual extinction corrections for each object to accurately trace the shape of the function. Results. Our 28 H α -selected sample of faint star-forming galaxies reveals a robust faint-end slope of the luminosity function α = - 1.46 -0.08 +0.16 . The derived star formation rate density at z ~ 0.62 is ρ SFR = 0.036 -0.008 +0.012 M ⊙ yr -1 Mpc -3 . The sample is mainly composed of disks, but an important contribution of compact galaxies with Sersic indexes n ~ 2 display the highest specific star formation rates. Conclusions. The luminosity function at z ~ 0.62 from our ultra-deep data points towards a steeper α when an individual extinction correction for each object is applied. Compact galaxies are low-mass, low-luminosity, and starburst-dominated objects with a light profile in an intermediate stage from early to late types.