Probing the Star Formation Main Sequence Down to 10⁸ M at 1.0 < z < 3.0

We investigate the star formation main sequence (MS; SFR-M-star) down to 10(8-9) M-circle dot using a sample of 34,061 newly discovered ultrafaint (27 mag less than or similar to i less than or similar to 30 mag) galaxies at 1 < z < 3 detected in the GOODS-N field. Virtually none of these galaxies are contained in previous public catalogs, effectively doubling the number of known sources in the field. The sample was constructed by stacking the optical broadband observations taken by the HST/GOODS-CANDELS surveys, as well as the 25 ultradeep medium-band images gathered by the GTC/SHARDS project. Our sources are faint (average observed magnitudes i similar to 28.2 and < H > similar to 27.9 mag), blue (UV slope similar to -1.9), star-forming (rest-frame colors < U - V > similar to 0.10 and < V - J > similar to 0.17 mag) galaxies. These observational characteristics are identified with young (mass-weighted age < t(M-w)> similar to 0.014 Gyr) stellar populations subject to low attenuations (A(V) similar to 0.30 mag). Our sample allows us to probe the MS down to 10(8.0) M-circle dot at z = 1 and 10(8.5) M-circle dot at z = 3, around 0.6 dex deeper than previous analyses. In the low-mass galaxy regime, we find an average value for the slope of 0.97 at 1 < z < 2 and 1.12 at 2 < z < 3. Nearly 60% of our sample presents stellar masses in the range 10(6-8) M-circle dot at 1 < z 更多