Clues to the formation of Liller 1 from modeling its complex star formation history

Abstract

Liller 1 and Terzan 5 are two massive systems in the Milky-Way bulge hosting populations characterized by significantly different ages ($\Delta t>7-8$ Gyr) and metallicities ($\Delta$[Fe/H]$\sim 1$ 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 (SFHs) 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 SF episodes are clearly detected: 1) a dominant one, occurred some 12-13 Gyr ago with a tail extending for up to $\sim 3$ Gyr, 2) an intermediate burst, between 6 and 9 Gyr ago, 3) and a recent one, occurred 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 a 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.

arXiv comment23 pages, 14 figures; accepted for publication in ApJ

References in corpus (53)

• Galactic Stellar and Substellar Initial Mass Function
• On the variation of the Initial Mass Function
• PARSEC: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code
• Star Formation Histories, Abundances and Kinematics of Dwarf Galaxies in the Local Group
• A new generation of PARSEC-COLIBRI stellar isochrones including the TP-AGB phase
• Formation of Massive Galaxies at High Redshift: Cold Streams, Clumpy Disks and Compact Spheroids
• VISTA Variables in the Via Lactea (VVV): The public ESO near-IR variability survey of the Milky Way
• The SINS survey of z~2 galaxy kinematics: properties of the giant star forming clumps
• Gaia EDR3 view on Galactic globular clusters
• Origin of the system of globular clusters in the Milky Way
• Nuclear Star Clusters
• Multiple Stellar Populations in the Globular Cluster omega Centauri as Tracers of a Merger Event
• Chemical Abundances for 855 Giants in the Globular Cluster Omega Centauri (NGC 5139)
• Bulge Formation by the Coalescence of Giant Clumps in Primordial Disk Galaxies
• ARGOS III: Stellar Populations in the Galactic Bulge of the Milky Way
• Evidence for Mature Bulges and an Inside-out Quenching Phase 3 Billion Years After the Big Bang
• A Morphological Catalog of Galaxies in the Hubble Deep Field
• The cluster Terzan 5 as a remnant of a primordial building block of the Galactic bulge
• Gas Physics, Disk Fragmentation, and Bulge Formation in Young Galaxies
• Hubble Space Telescope Imaging of Star-Forming Galaxies at Redshifts z>3
• An Empirical Pixel-Based Correction for Imperfect CTE. I. HST's Advanced Camera for Surveys
• Faintest Galaxy Morphologies from $HST$ WFPC2 Imaging of the Hawaii Survey Fields
• New evidence for the complex struscture of the RGB of Omega Cen
• From the bulge to the outer disc: StarHorse stellar parameters, distances, and extinctions for stars in APOGEE DR16 and other spectroscopic surveys
• Discovery of Face-On Counterparts of Chain Galaxies in the Tadpole ACS Field
• Morphologies of ~190,000 Galaxies at z=0-10 Revealed with HST Legacy Data II. Evolution of Clumpy Galaxies
• The Gaia-ESO Survey: Exploring the complex nature and origins of the Galactic bulge populations
• Metallicities, relative ages and kinematics of stellar populations in omega Centauri
• Spectroscopy Unveils the Complex Nature of Terzan 5
• Gemini multi-conjugate adaptive optics system review II: Commissioning, operation and overall performance
• Double Blue Straggler sequences in GCs: the case of NGC 362
• Ceci n'est pas a globular cluster: the metallicity distribution of the stellar system Terzan 5
• High resolution infrared spectra of bulge globular clusters: Liller~1 and NGC 6553
• Discovery of an anomalous Sub Giant Branch in the Color Magnitude Diagram of omega Centauri
• Stochastic self-enrichment, pre-enrichment, and the formation of globular clusters
• Hubble Tarantula Treasury Project: Unraveling Tarantula's Web. II. Optical and Near Infrared Star Formation History of the Starburst Cluster NGC 2070 in 30 Doradus
• The Accreted Nuclear Clusters of the Milky Way
• Old and young bulges in late-type disk galaxies
• Metallicity Distribution Functions, Radial Velocities, and Alpha Element Abundances in Three Off-Axis Bulge Fields
• The Giraffe Inner Bulge Survey (GIBS) II. Metallicity distributions and alpha element abundances at fixed Galactic latitude
• Clusters of Small Clumps Can Explain The Peculiar Properties of Giant Clumps in High-Redshift Galaxies
• A new class of fossil fragments from the hierarchical assembly of the Galactic bulge
• No evidence of mass segregation in the low mass Galactic globular cluster NGC 6101
• A panchromatic view of the bulge globular cluster NGC 6569
• Central Blue Clumps in Elliptical Galaxies of the Hubble Ultra Deep Field
• Star Formation Histories of the LEGUS Dwarf Galaxies (I): recent History of NGC1705, NGC4449 and Holmberg II
• A new model for the multiple stellar populations within Terzan 5
• Proper motions in Terzan 5: membership of the multi-iron sub-populations and first constrain to the orbit
• Hubble Tarantula Treasury Project V. The star cluster Hodge 301: the old face of 30 Doradus
• High-resolution extinction map in the direction of the strongly obscured bulge fossil fragment Liller 1
• GeMS/GSAOI photometric and astrometric performance in dense stellar fields
• The Proper Motion of Pyxis: the first use of Adaptive Optics in tandem with HST on a faint halo object
• Three candidate double clusters in the LMC: truth or dare?

Cited by in corpus (13)

• First evidence of multi-iron sub-populations in the Bulge Fossil Fragment candidate Liller 1
• Modeling the chemical enrichment history of the Bulge Fossil Fragment Terzan 5
• Internal kinematics and structure of the bulge globular cluster NGC 6569
• The Bulge Cluster Origin (BulCO) survey at the ESO-VLT: probing the early history of the Milky Way assembling. Design and first results in Liller1
• The $Hubble$ Missing Globular Cluster Survey. I. Survey overview and the first precise age estimate for ESO452-11 and 2MASS-GC01
• A Photometric in-depth look at the core-collapsed globular cluster NGC 6284
• On the manifest link between Terzan 5 and the Galactic bulge
• The bulge globular cluster Terzan 6 as seen from multi-conjugate adaptive optics and HST
• Extended Main-Sequence Turnoff and Red Clump in intermediate-age star clusters: A study of NGC 419
• Bulge Fossil Fragments as a new population of factories of gravitational wave sources in the Galaxy
• The multi-age stellar populations of Terzan 5 as revealed by JWST
• Revealing the stellar population of the ultra-obscured Galactic globular cluster Glimpse-C02
• A candidate to the long sought optical counterpart to the Rapid Burster in the bulge fossil fragment Liller 1