J-PLUS: The star formation main sequence and rate density at d < 75 Mpc
  Our goal is to estimate the star formation main sequence (SFMS) and the star
formation rate density (SFRD) at z <= 0.017 (d < 75 Mpc) using the Javalambre
Photometric Local Universe Survey (J-PLUS) first data release, that probes
897.4 deg2 with twelve optical bands. We extract the Halpha emission flux of
805 local galaxies from the J-PLUS filter J0660, being the continuum level
estimated with the other eleven J-PLUS bands, and the dust attenuation and
nitrogen contamination corrected with empirical relations. Stellar masses (M),
Halpha luminosities (L), and star formation rates (SFRs) were estimated by
accounting for parameters covariances. Our sample comprises 689 blue galaxies
and 67 red galaxies, classified in the (u-g) vs (g-z) color-color diagram, plus
49 AGN. The SFMS is explored at log M > 8 and it is clearly defined by the blue
galaxies, with the red galaxies located below them. The SFMS is described as
log SFR = 0.83 log M - 8.44. We find a good agreement with previous estimations
of the SFMS, especially those based on integral field spectroscopy. The Halpha
luminosity function of the AGN-free sample is well described by a Schechter
function with log L* = 41.34, log phi* = -2.43, and alpha = -1.25. Our
measurements provide a lower characteristic luminosity than several previous
studies in the literature. The derived star formation rate density at d < 75
Mpc is log rho_SFR = -2.10 +- 0.11, with red galaxies accounting for 15% of the
SFRD. Our value is lower than previous estimations at similar redshift, and
provides a local reference for evolutionary studies regarding the star
formation history of the Universe.
