Pérez González, Pablo GuillermoEsquej Alonso, María del PilarDomínguez Sánchez, HelenaEspino, Néstor2023-06-192023-06-192015-01-012041-820510.1088/2041-8205/798/1/L4https://hdl.handle.net/20.500.14352/33793© 2015. The American Astronomical Society. We acknowledge support from the Spanish Government grants AYA2010-21322-C03-02 and AYA2012-31277, and the ERC Advanced Grant 321323-NEOGAL. This work is based on SHARDS observations made with the Gran Telescopio Canarias (GTC), and the Rainbow Cosmological Surveys Database, operated by UCM partnered with UCO/Lick, UCSC. I.M.N. thanks Carsten Weidner, Jesús Falcón Barroso, and Mike Beasley for their careful reading and comments on the manuscript.We explore the stellar initial mass function (IMF) of a sample of 49 massive quiescent galaxies (MQGs) at 0.9 < z < 1.5. We base our analysis on intermediate resolution spectro-photometric data in the GOODS-N field taken in the near-infrared and optical with the Hubble Space Telescope Wide Field Camera 3 G141 grism and the Survey for High-z Absorption Red and Dead Sources. To constrain the slope of the IMF, we have measured the TiO2 spectral feature, whose strength depends strongly on the content of low-mass stars, as well as on stellar age. Using ultraviolet to near-infrared individual and stacked spectral energy distributions, we have independently estimated the stellar ages of our galaxies. Knowing the age of the stellar population, we interpret the strong differences in the TiO2 feature as an IMF variation. In particular, for the heaviest z similar to 1 MQGs (M > 10(11) M-circle dot), we find an average age of 1.7 +/- 0.3 Gyr and a bottom-heavy IMF (Gamma(b) = 3.2 +/- 0.2). Lighter MQGs (2 x 10(10) < M < 10(11) M-circle dot) at the same redshift are younger on average (1.0 +/- 0.2 Gyr) and present a shallower IMF slope (Gamma(b) = 2.7(-0.4)(+0.3)). Our results are in good agreement with the findings about the IMF slope in early-type galaxies of similar mass in the present-day universe. This suggests that the IMF, a key characteristic of the stellar populations in galaxies, is bottom-heavier for more massive galaxies and has remained unchanged in the last similar to 8 Gyr.engThe stellar initial mass function at 0.9 < z < 1.5journal articlehttp://dx.doi.org/10.1088/2041-8205/798/1/L4http://iopscience.iop.org/open access52Early-type galaxiesExtragalactic legacy surveyNear-infrared spectroscopyTo-fir analysisQuiescent galaxiesPopulation synthesisSpitzer/IRAC sourcesSystematic variationLine indexesAbsorptionAstrofísicaAstronomía (Física)Física atmosférica2501 Ciencias de la Atmósfera