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Clues to the Formation of Liller 1 from Modeling Its Complex Star Formation History

Dalessandro, E, Crociati, C, Cignoni, M, Ferraro, FR, Lanzoni, B, Origlia, L, Pallanca, C, Rich, RM, Saracino, S and Valenti, E (2022) Clues to the Formation of Liller 1 from Modeling Its Complex Star Formation History. Astrophysical Journal, 940 (2). ISSN 0004-637X

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Liller 1 and Terzan 5 are two massive systems in the Milky Way bulge hosting populations characterized by significantly different ages (Δt > 7-8 Gyr) and metallicities (Δ[Fe/H] ∼ 1 dex). Their origin is still strongly debated in the literature and all formation scenarios proposed so far require some level of fine-tuning. The detailed star formation histories of these systems may represent an important piece of information to assess their origin. Here we present the first attempt to perform such an analysis for Liller 1. The first key result we find is that Liller 1 has been forming stars over its entire lifetime. More specifically, three broad star formation episodes are clearly detected: (1) a dominant one, occurring some 12-13 Gyr ago with a tail extending for up to ∼3 Gyr; (2) an intermediate burst, between 6 and 9 Gyr ago; and (3) a recent one, occurring between 1 and 3 Gyr ago. The old population contributes to about 70% of the total stellar mass, and the remaining fraction is almost equally split between the intermediate and young populations. If we take these results at face value, they would suggest that this system unlikely formed through the merger between an old globular cluster and a giant molecular cloud, as recently proposed. On the contrary, our findings provide further support to the idea that Liller 1 is the surviving relic of a massive primordial structure that contributed to the Galactic bulge formation, similarly to the giant clumps observed in star-forming high-redshift galaxies.

Item Type: Article
Uncontrolled Keywords: 0201 Astronomical and Space Sciences; 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics; 0306 Physical Chemistry (incl. Structural); Astronomy & Astrophysics
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: American Astronomical Society; IOP Publishing
SWORD Depositor: A Symplectic
Date Deposited: 13 Jun 2023 15:20
Last Modified: 13 Jun 2023 15:30
DOI or ID number: 10.3847/1538-4357/ac9907
URI: https://researchonline.ljmu.ac.uk/id/eprint/19791
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