A new class of fossil fragments from the hierarchical assembly of the Galactic bulge

Abstract

The formation and evolutionary processes of galaxy bulges are still unclear, and the presence of young stars in the bulge of the Milky Way is largely debated. We recently demonstrated that Terzan 5, in the Galactic bulge, is a complex stellar system hosting stars with very different ages and a striking chemical similarity to the field population. This indicates that its progenitor was likely one of the giant structures that are thought to generate bulges through coalescence. Here we show that another globular cluster-like system in the bulge (Liller 1) hosts two distinct stellar populations with remarkably different ages: only 1-3 Gyr for the youngest, 12 Gyr for the oldest, which is impressively similar to the old component of Terzan 5. This discovery classifies Liller 1 and Terzan 5 as sites of recent star formation in the Galactic bulge and provides clear observational proof that the hierarchical assembly of primordial massive structures contributed to the formation of the Milky Way spheroid.

29 pages, 10 figures, typo in author affiliation fixed, published in Nature Astronomy

References in corpus (13)

• Dynamical modelling of the Galactic bulge and bar: the Milky Way's bar pattern speed, stellar, and dark matter mass distribution
• Bulge Formation by the Coalescence of Giant Clumps in Primordial Disk Galaxies
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• Ceci n'est pas a globular cluster: the metallicity distribution of the stellar system Terzan 5
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• The surface density profile of NGC 6388: a good candidate for harboring an intermediate-mass black hole
• Old and young bulges in late-type disk galaxies
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• Star density profiles of six old star clusters in the Large Magellanic Cloud
• Spectral Energy Distribution of Blue Stragglers in the core of 47 Tucanae
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Cited by in corpus (10)

• Accurate distances to Galactic globular clusters through a combination of Gaia EDR3, HST and literature data
• High-resolution extinction map in the direction of the strongly obscured bulge fossil fragment Liller 1
• Clues to the formation of Liller 1 from modeling its complex star formation history
• Hidden in the Haystack: Low-luminosity globular clusters towards the Milky Way bulge
• Abundance analysis of APOGEE spectra for 58 metal-poor stars from the bulge spheroid
• HST observations of the globular cluster NGC 6402 (M14) and its peculiar multiple populations
• Intrinsic Metallicity Variation in the Intermediate Mass Type II Globular Cluster NGC 1261
• Is Terzan 5 the remnant of a building block of the Galactic bulge? Evidence from APOGEE
• Blanco DECam Bulge Survey (BDBS) IV: Metallicity Distributions and Bulge Structure from 2.6 Million Red Clump Stars
• Star Cluster Ecology: Revisiting the Origin of Iron and Age Complex Clusters