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A prediction on the age of thick discs as a function of the stellar mass of the host galaxy
- Source :
- A&A 645, L13 (2021)
- Publication Year :
- 2021
-
Abstract
- 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 $z\leq3.0$, 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 $\mathcal{M}_\star(z=0)<10^{10}\,\mathcal{M}_\odot$ have thick disc stars as young as $4-6\,{\rm Gyr}$, whereas the youngest stars in the thick discs of Milky-Way-like galaxies are $\sim10\,{\rm Gyr}$ old. I tested this prediction against the scarcely available thick disc age estimates, all of them are from galaxies with $\mathcal{M}_\star(z=0)\gtrsim10^{10}\,\mathcal{M}_\odot$, 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 $\mathcal{M}_\star(z=0)\sim10^{9.5}\,\mathcal{M}_\odot$ and by checking whether they contain $\sim5\,{\rm Gyr}$-old stars.<br />Comment: Letter accepted for publication in A&A
- Subjects :
- Astrophysics - Astrophysics of Galaxies
Subjects
Details
- Database :
- arXiv
- Journal :
- A&A 645, L13 (2021)
- Publication Type :
- Report
- Accession number :
- edsarx.2101.04478
- Document Type :
- Working Paper
- Full Text :
- https://doi.org/10.1051/0004-6361/202040175