THE STELLAR INITIAL MASS FUNCTION AT 0.9 < z < 1.5
- Instituto de Astrofísica de Canarias, c/Vía Láctea s/n, E38205 - La Laguna, Tenerife (Spain)
- Departamento de Astrofísica, Facultad de CC. Físicas, Universidad Complutense de Madrid, E-28040 Madrid (Spain)
- UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)
- Centro de Radioastronomía y Astrofísica, UNAM, Campus Morelia, México (Mexico)
- UPMC-CNRS, UMR7095, Institut d'Astrophysique de Paris, F-75014 Paris (France)
- Observatoire de Genève, Université de Genève, 51 Ch. des Maillettes, 1290 Versoix (Switzerland)
- Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT (United Kingdom)
- INAF-Osservatorio Astronomico di Capodimonte, Napoli (Italy)
- Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
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 TiO{sub 2} 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 TiO{sub 2} feature as an IMF variation. In particular, for the heaviest z ∼ 1 MQGs (M > 10{sup 11} M {sub ☉}), we find an average age of 1.7 ± 0.3 Gyr and a bottom-heavy IMF (Γ {sub b} = 3.2 ± 0.2). Lighter MQGs (2 × 10{sup 10} < M < 10{sup 11} M {sub ☉}) at the same redshift are younger on average (1.0 ± 0.2 Gyr) and present a shallower IMF slope (Γ{sub b}=2.7{sub −0.4}{sup +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 ∼8 Gyr.
- OSTI ID:
- 22364765
- Journal Information:
- Astrophysical Journal Letters, Vol. 798, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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