Issue |
A&A
Volume 690, October 2024
|
|
---|---|---|
Article Number | A208 | |
Number of page(s) | 15 | |
Section | Galactic structure, stellar clusters and populations | |
DOI | https://doi.org/10.1051/0004-6361/202450754 | |
Published online | 08 October 2024 |
(Re)mind the gap: A hiatus in star formation history unveiled by APOGEE DR17
1
I.N.A.F. Osservatorio Astronomico di Trieste,
via G.B. Tiepolo 11,
34131
Trieste,
Italy
2
Dipartimento di Fisica, Sezione di Astronomia, Università di Trieste,
Via G. B. Tiepolo 11,
34143
Trieste,
Italy
3
I.N.F.N. Sezione di Trieste,
via Valerio 2,
34134
Trieste,
Italy
4
I.N.A.F. Osservatorio Astronomico di Padova,
Vicolo dell’Osservatorio 5,
35122
Padova,
Italy
5
Leibniz-Institut für Astrophysik Potsdam,
An der Sternwarte 16,
14482
Potsdam,
Germany
★ Corresponding author; emanuele.spitoni@inaf.it
Received:
17
May
2024
Accepted:
27
August
2024
Context. Analysis of several spectroscopic surveys indicates the presence of a bimodality between the disc stars in the abundance ratio space of [α/Fe] versus [Fe/H]. The two stellar groups are commonly referred to as the high-α and low-α sequences. Some models capable of reproducing such a bimodality invoke the presence of a hiatus in the star formation history in our Galaxy, whereas other models explain the two sequences by means of stellar migration.
Aims. Our aim is to show that the existence of the gap in the star formation rate between high-α and low-α is evident in the stars of APOGEE DR17, if one plots [Fe/α] versus [α/H], confirming previous suggestions. We then try to interpret the data by means of detailed chemical models.
Methods. We compare the APOGEE DR17 red giant stars with the predictions of a detailed chemical evolution model based on the two-infall paradigm, taking into account also the possible accretion of dwarf satellites.
Results. The APOGEE DR17 abundance ratios [Fe/α] versus [α/H] exhibit a sharp increase in [Fe/α] at a nearly constant [α/H] (where α elements considered are Mg, Si, O) during the transition between the two disc phases. This observation strongly supports the hypothesis that a hiatus in star formation occurred during this evolutionary phase. Notably, the most pronounced growth in the [Fe/α] versus [α/H] relation is observed for oxygen, as this element is exclusively synthesised in core-collapse supernovae. The revised version of the two-infall chemical evolution model proposed in this study reproduces the APOGEE DR17 abundance ratios better than before. Particularly noteworthy is the model’s ability to predict the hiatus in the star formation between the two infalls of gas, which form the thick and thin disc, respectively, and thus generate abundance ratios compatible with APOGEE DR17 data.
Conclusions. We show that the signature of a hiatus in the star formation is imprinted in the APOGEE DR17 abundance ratios. A chemical model predicting a pause in the star formation of a duration of roughly 3.5 Gyr, and in which the high-α disc starts forming from pre-enriched gas by a previous encounter with a dwarf galaxy, could well explain the observations
Key words: ISM: abundances / Galaxy: abundances / Galaxy: disk / Galaxy: evolution / Galaxy: formation
© The Authors 2024
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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