2021A&A...645L..13C -
Astronomy and Astrophysics, volume 645, L13-13 (2021/1-1)
A prediction about the age of thick discs as a function of the stellar mass of the host galaxy.
COMERON S.
Abstract (from CDS):
One of the suggested thick disc formation mechanisms is that they were born quickly and in situ from a turbulent clumpy disc. Subsequently, thin discs formed slowly within them from leftovers of the turbulent phase and from material accreted through cold flows and minor mergers. In this Letter, I propose an observational test to verify this hypothesis. By combining thick disc and total stellar masses of edge-on galaxies with galaxy stellar mass functions calculated in the redshift range of z≤3.0, I derived a positive correlation between the age of the youngest stars in thick discs and the stellar mass of the host galaxy; galaxies with a present-day stellar mass of M*(z=0)<1010M☉ have thick disc stars as young as 4-6Gyr, whereas the youngest stars in the thick discs of Milky-Way-like galaxies are ∼10Gyr old. I tested this prediction against the scarcely available thick disc age estimates, all of them are from galaxies with M*(z=0)≥1010M☉, and I find that field spiral galaxies seem to follow the expectation. On the other hand, my derivation predicts ages that are too low for the thick discs in lenticular galaxies, indicating a fast early evolution for S0 galaxies. I propose the idea of conclusively testing whether thick discs formed quickly and in situ by obtaining the ages of thick discs in field galaxies with masses of M*(z=0)∼109.5M☉ and by checking whether they contain ∼5Gyr-old stars.
Abstract Copyright:
© ESO 2021
Journal keyword(s):
galaxies: evolution - galaxies: spiral - galaxies: structure
Simbad objects:
10
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