The multi-age stellar populations of Terzan 5 as revealed by JWST

Abstract

The James Webb Space Telescope provides an exciting opportunity to investigate stellar systems located in heavily obscured regions like the Galactic bulge. Possibly, the most enigmatic among them is Terzan 5: long classified as a globular cluster, it is now known to host distinct stellar populations with different iron abundances (ranging approximately from [Fe/H]=-$0.8$ to [Fe/H]=$+0.3$ dex). Indeed the chemical and structural properties collected so far suggest that it is the remnant of one of the primordial clumps that contributed to the early assembly of the bulge, a so-called "Bulge Fossil Fragment". Here we present a new photometric analysis of Terzan 5 based on JWST/NIRCam observations in the F115W and F200W filters, as well as archival HST/ACS optical (F606W and F814W) data. The dataset overcomes the severe and spatially variable extinction along the line of sight and yields the deepest color-magnitude diagram ever obtained for Terzan 5. Proper motion selections and high-resolution differential reddening corrections allow us to isolate bona fide cluster members and to provide an unprecedented view of the main-sequence turn-off region. We clearly identify two main components and determine their respective ages: the old, sub-solar component has an age of 12.5 $\pm$ 0.5 Gyr, while the super-solar component is significantly younger with an age of 4.7 $\pm$ 0.5 Gyr. Interestingly, we also find hints of an even younger main sequence turn-off and sub-giant branch, consistent with the presence of a further stellar component with an age of 3.8 $\pm$ 0.5 Gyr. There is also evidence of a blue plume populated by stars as bright as $m_{F115W}\sim 17.4$, suggesting a prolonged period of star formation extending up to 2.5 Gyr ago.

Accepted for publication in A&A

References in corpus (26)

• Gaia Data Release 3: Summary of the content and survey properties
• New PARSEC evolutionary tracks of massive stars at low metallicity: testing canonical stellar evolution in nearby star forming dwarf galaxies
• Streams, substructures and the early history of the Milky Way
• Accurate distances to Galactic globular clusters through a combination of Gaia EDR3, HST and literature data
• Bulge Formation by the Coalescence of Giant Clumps in Primordial Disk Galaxies
• Unstable disks at high redshift: Evidence for smooth accretion in galaxy formation
• Ceci n'est pas a globular cluster: the metallicity distribution of the stellar system Terzan 5
• Extinction ratios in the inner Galaxy as revealed by the VVV survey
• The age of the young bulge-like population in the stellar system Terzan5: linking the Galactic bulge to the high-z Universe
• Blue Straggler Stars in the Unusual Globular Cluster NGC 6388
• A new class of fossil fragments from the hierarchical assembly of the Galactic bulge
• High resolution reddening map in the direction of the stellar system Terzan 5
• Discovery and timing of ten new millisecond pulsars in the globular cluster Terzan 5
• JWST-TST Proper Motions: I. High-Precision NIRISS Calibration and Large Magellanic Cloud Kinematics
• Digging for relics of the past: the ancient and obscured bulge globular cluster NGC6256
• A new identity card for the bulge globular cluster NGC 6440 from resolved star counts
• First evidence of multi-iron sub-populations in the Bulge Fossil Fragment candidate Liller 1
• 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
• JWST uncovers helium and water abundance variations in the bulge globular cluster NGC 6440
• Modeling the chemical enrichment history of the Bulge Fossil Fragment Terzan 5
• A binary-related origin mediated by environmental conditions for blue straggler stars
• 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
• 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
• Bulge Fossil Fragments as a new population of factories of gravitational wave sources in the Galaxy