The stellar initial mass function at 0.9 < z < 1.5



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Pérez González, Pablo Guillermo and Esquej Alonso, María del Pilar and Domínguez Sánchez, Helena and Espino, Néstor (2015) The stellar initial mass function at 0.9 < z < 1.5. Astrophysical journal letters, 798 (1). ISSN 2041-8205

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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.

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© 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.

Uncontrolled Keywords:Early-type galaxies; Extragalactic legacy survey; Near-infrared spectroscopy; To-fir analysis; Quiescent galaxies; Population synthesis; Spitzer/IRAC sources; Systematic variation; Line indexes; Absorption
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
Sciences > Physics > Atmospheric physics
ID Code:28465
Deposited On:02 Mar 2015 12:53
Last Modified:10 Dec 2018 15:05

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