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

  • Action space (normalized to the sum of the three actions of motion, Jtot) of Gaia RVS stars
    Research news
    The Metal-Poor Edge of the Milky Way’s Thin Disk
    The formation and evolution of the disk of our Galaxy, the Milky Way, remains an enigma in astronomy. In particular, the relationship between the thick disk and the thin disk —two key components of the Milky Way— is still unclear. Understanding the chemical and dynamical properties of the stars within these disks is crucial, especially in the parameter spaces where their characteristics overlap, such the metallicity regime around [Fe/H] ~ -0.7, which marks the metal-poor end of the thin disk, higher than that of the thick disk. This is often interpreted as an indication that the thin disk
    Advertised on
  • 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
  • Research news
    On the magnetic nature of quiet-Sun chromospheric grains
    CaII Kgrains, i.e., intermittent, short-lived (about 1 minute), periodic (2-4 minutes), pointlike chromospheric brightenings, are considered to be the manifestations of acoustic waves propagating upward from the solar surface and developing into shocks in the chromosphere. After the simulations of Carlsson and Stein, we know that hot shocked gas moving upward interacting with the downflowing chromospheric gas (falling down after having been displaced upward by a previous shock) nicely reproduces the spectral features of the CaII K profiles observed in such grains, i.e., a narrowband emission
    Advertised on