The Stellar Initial Mass Function at 0.9 < z < 1.5

Martín-Navarro, I.; Pérez-González, P. G.; Trujillo, I.; Esquej, Pilar; Vazdekis, A.; Domínguez Sánchez, Helena; Barro, Guillermo; Bruzual, Gustavo; Charlot, Stéphane; Cava, Antonio; Ferreras, Ignacio; Espino, Néstor; La Barbera, Francesco; Koekemoer, Anton M.; Cenarro, A. Javier
Bibliographical reference

The Astrophysical Journal Letters, Volume 798, Issue 1, article id. L4, 6 pp. (2015).

Advertised on:
1
2015
Number of authors
15
IAC number of authors
4
Citations
32
Refereed citations
31
Description
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 ~ 1 MQGs (M > 1011 M ☉), we find an average age of 1.7 ± 0.3 Gyr and a bottom-heavy IMF (Γ b = 3.2 ± 0.2). Lighter MQGs (2 × 1010 < M < 1011 M ☉) at the same redshift are younger on average (1.0 ± 0.2 Gyr) and present a shallower IMF slope (Γ _b=2.7+0.3-0.4). 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 ~8 Gyr.
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Traces of Galaxy Formation: Stellar populations, Dynamics and Morphology
We are a large, diverse, and very active research group aiming to provide a comprehensive picture for the formation of galaxies in the Universe. Rooted in detailed stellar population analysis, we are constantly exploring and developing new tools and ideas to understand how galaxies came to be what we now observe.
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Martín Navarro