The stellar initial mass function at 0.9 < z < 1.5.

Advertised on
References
2015ApJ,798L,4M

We explore the stellar initial mass function (IMF) of a sample of 49massive quiescent galaxies (MQGs) at 0.9<z<1.5. We base our analysis on intermediate resolution spectro-photometric data in theGOODS-N field taken in the near-infrared and optical with the HST/WFC3 G141 grism and the Survey for High-z Absorption Red andDead Sources (SHARDS). To constrain the slope of the IMF, we havemeasured the TiO2 spectral feature, whose strength depends strongly on the content of low-mass stars, as well as on stellar age. Usingultraviolet to near-infrared individual and stacked spectral energydistributions, we have independently estimated the stellar ages of ourgalaxies. Knowing the age of the stellar population, we interpret thestrong differences in the TiO2 feature as an IMF variation. In particular,for the heaviest z~1 MQGs (M>10^11.0 Msun) we find an average age of1.7+/-0.3 Gyr and a bottom-heavy IMF (Gamma=3.2+/-0.2). LighterMQGs (10^10.3<M<10^11.0 Msun) at the same redshift are younger onaverage (1.0+/-0.2 Gyr) and present a shallower IMF slopeGamma=2.7+/-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.


News type
Research news

It may interest you

  • Black Hole Swift J1727.8-162
    Research news
    Evidence for inflows and outflows in the nearby black hole transient Swift J1727.8-162
    The transient Swift J1727.8-162 is the latest member of the X-ray binary black hole family to be discovered. They are formed by a black hole and a low-mass star whose gas is stripped off and accreted to the black hole via an accretion disc. The high temperature of the accretion disc makes it shine in all energy bands up to X-rays, and is particularly bright during epochs known as outbursts. In this novel study, published just a few months after the discovery of the system, we present 20 epochs of optical spectroscopy obtained with the GTC-10.4m telescope. The spectra cover the main accretion
    Advertised on
  • Hertzsprung–Russel diagram blue supergiants
    Research news
    Challenging the theoretically predicted mass-loss rate increase of blue supergiants in the bi-stability region of the stellar winds
    The properties of blue supergiants are key for constraining the end of the main sequence phase, a phase during which massive stars spend most of their lifetimes. The lack of fast-rotating stars below 21.000K, a temperature around which stellar winds change in behaviour, has been proposed to be caused by enhanced mass-loss rates, which would spin down the star. Alternatively, the lack of fast-rotating stars may be the result of stars reaching the end of the main sequence. Here, we combine newly derived estimates of photospheric and wind parameters, wind terminal velocities from the literature
    Advertised on
  • Planetary Nebula M57
    Research news
    Hydrogenated amorphous carbon grains as a carrier of unidentified IR bands in planetary nebulae
    It is well known that fullerenes – big, complex, and highly resistant carbon molecules with potential applications in nanotechnology – are mostly seen in planetary nebulae (PNe); old dying stars with progenitor masses similar to our Sun. Fullerenes, like C60 and C70, have been detected in PNe whose infrared (IR) spectra are dominated by broad unidentified IR (UIR) plateau emissions. The identification of the chemical species (structure and composition) responsible for such UIR emission widely present in the Universe is a mystery in astrochemistry; although they are believed to be carbon-rich
    Advertised on