The first Herschel view of the mass-SFR link in high-z galaxies

Aims: We exploit deep observations of the GOODS-N field taken with PACS, the Photodetector Array Camera and Spectrometer, onboard of Herschel, as part of the PACS evolutionary probe guaranteed time (PEP), to study the link between star formation and stellar mass in galaxies to z ~ 2. Methods: Starting from a stellar mass - selected sample of ~4500 galaxies with mag4.5 \ub5m < 23.0 (AB), we identify ~350 objects with a PACS detection at 100 or 160 \u3bcm and ~1500 with only Spitzer 24 \u3bcm counterpart. Stellar masses and total IR luminosities (LIR) are estimated by fitting the spectral energy distributions (SEDs). Results: Consistently with other Herschel results, we find that LIR based only on 24 \u3bcm data is overestimated by a median factor ~1.8 at z ~ 2, whereas it is underestimated (with our approach) up to a factor ~1.6 at 0.5 1011 Msun galaxies from z = 0 to z = 2, and seems to flatten at z > 1.5 in this mass range. Moreover, the most massive galaxies have the lowest SSFR at any z, implying that they have formed their stars earlier and more rapidly than their low mass counterparts (downsizing). Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Appendices are only available in electronic form at http://www.aanda.or