Pathways to quiescence: SHARDS view on the star formation histories of massive quiescent galaxies at 1.0 < z < 1.5

Helena Domínguez Sánchez, Pablo G. Pérez-González, Pilar Esquej, M. Carmen Eliche-Moral, Guillermo Barro, Antonio Cava, Anton M. Koekemoer, Belén Alcalde Pampliega, Almudena Alonso Herrero, Gustavo Bruzual, Nicolás Cardiel, Javier Cenarro, Daniel Ceverino, Stéphane Charlot, Antonio Hernán Caballero. 2016. Pathways to quiescence: SHARDS view on the star formation histories of massive quiescent galaxies at 1.0 < z < 1.5. Monthly Notices of the Royal Astronomical Society 457, 4, 3743-3768 DOI: 10.1093/mnras/stw201

We present star formation histories (SFHs) for a sample of 104 massive (stellar mass M > 10(10) M-circle dot) quiescent galaxies (MQGs) at z = 1.0-1.5 from the analysis of spectrophotometric data from the Survey for High-z Absorption Red and Dead Sources (SHARDS) and HST/WFC3 G102 and G141 surveys of the GOODS-North field, jointly with broad-band observations from ultraviolet (UV) to far-infrared (far-IR). The sample is constructed on the basis of rest-frame UVJ colours and specific star formation rates (sSFRs = SFR/Mass). The spectral energy distributions (SEDs) of each galaxy are compared to models assuming a delayed exponentially declining SFH. A Monte Carlo algorithm characterizes the degeneracies, which we are able to break taking advantage of the SHARDS data resolution, by measuring indices such as MgUV and D4000. The population of MQGs shows a duality in their properties. The sample is dominated (85 per cent) by galaxies with young mass-weighted ages, (t(M)) over bar < 2 Gyr, short star formation time-scales, <tau > similar to 60-200 Myr, and masses log(M/M-circle dot) similar to 10.5. There is an older population (15 per cent) with <(t(M))over bar> = 2-4 Gyr, longer star formation time-scales, <tau > similar to 400 Myr, and larger masses, log(M/M-circle dot) similar to 10.7. The SFHs of our MQGs are consistent with the slope and the location of the main sequence of star-forming galaxies at z > 1.0, when our galaxies were 0.5-1.0 Gyr old. According to these SFHs, all the MQGs experienced a luminous infrared galaxy phase that lasts for similar to 500 Myr, and half of them an ultraluminous infrared galaxy phase for similar to 100 Myr. We find that the MQG population is almost assembled at z similar to 1, and continues evolving passively with few additions to the population.

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