Nitrogen-enriched, Highly Pressurized Nebular Clouds Surrounding a Super Star Cluster at Cosmic Noon
Abstract
Strong lensing offers a precious opportunity for studying the formation and early evolution of super star clusters that are rare in our cosmic backyard. The Sunburst Arc, a lensed Cosmic Noon galaxy, hosts a young super star cluster with escaping Lyman continuum radiation. Analyzing archival Hubble Space Telescope images and emission line data from Very Large Telescope/MUSE and X-shooter, we construct a physical model for the cluster and its surrounding photoionized nebula. We confirm that the cluster is ≲4 Myr old, is extremely massive M ⋆ ~ 107 M ⊙, and yet has a central component as compact as several parsecs, and we find a gas-phase metallicity Z = (0.22 ± 0.03)Z ⊙. The cluster is surrounded by ≳105 M ⊙ of dense clouds that have been pressurized to P ~ 109 K cm-3 by perhaps stellar radiation at within 10 pc. These should have large neutral columns N HI > 1022.8 cm-2 to survive rapid ejection by radiation pressure. The clouds are likely dusty as they show gas-phase depletion of silicon, and may be conducive to secondary star formation if N HI > 1024 cm-2 or if they sink farther toward the cluster center. Detecting strong [N III]λ λ 1750,1752, we infer heavy nitrogen enrichment $\mathrm{log}({\rm{N}}/{\rm{O}})=-{0.21}_{-0.11}^{+0.10}$ . This requires efficiently retaining ≳500 M ⊙ of nitrogen in the high-pressure clouds from massive stars heavier than 60 M ⊙ up to 4 Myr. We suggest a physical origin of the high-pressure clouds from partial or complete condensation of slow massive star ejecta, which may have an important implication for the puzzle of multiple stellar populations in globular clusters.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 2023
- DOI:
- 10.3847/1538-4357/acf75c
- arXiv:
- arXiv:2301.10790
- Bibcode:
- 2023ApJ...957...77P
- Keywords:
-
- Stellar populations;
- Star clusters;
- Galaxies;
- 1622;
- 1567;
- 573;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 27 pages, 11 figures, Published in ApJ