A giant galaxy in the young Universe with a massive ring

Abstract

In the local (redshift z~0) Universe, collisional ring galaxies make up only ~0.01% of galaxies and are formed by head-on galactic collisions that trigger radially propagating density waves. These striking systems provide key snapshots for dissecting galactic disks and are studied extensively in the local Universe. However, not much is known about distant (z>0.1) collisional rings. Here we present a detailed study of a ring galaxy at a look-back time of 10.8 Gyr (z=2.19). Compared with our Milky Way, this galaxy has a similar stellar mass, but has a stellar half-light radius that is 1.5-2.2 times larger and is forming stars 50 times faster. The large, diffuse stellar light outside the star-forming ring, combined with a radial velocity on the ring and an intruder galaxy nearby, provides evidence for this galaxy hosting a collisional ring. If the ring is secularly evolved, the implied large bar in a giant disk would be inconsistent with the current understanding of the earliest formation of barred spirals. Contrary to previous predictions, this work suggests that massive collisional rings were as rare 11 Gyr ago as they are today. Our discovery offers a unique pathway for studying density waves in young galaxies, as well as constraining the cosmic evolution of spiral disks and galaxy groups.

Author's version for the main article (10 pages). The Supplementary Information (22 pages) and a combined pdf are provided here http://astronomy.swin.edu.au/~tyuan/paper Published version available online http://dx.doi.org/10.1038/s41550-020-1102-7

References in corpus (14)

• EAZY: A Fast, Public Photometric Redshift Code
• 3D-HST+CANDELS: The Evolution of the Galaxy Size-Mass Distribution since $z=3$
• An ultra-deep near-infrared spectrum of a compact quiescent galaxy at z=2.2
• 3D-HST WFC3-selected Photometric Catalogs in the Five CANDELS/3D-HST Fields: Photometry, Photometric Redshifts and Stellar Masses
• Strong Nebular Line Ratios in the Spectra of z~2-3 Star-forming Galaxies: First Results from KBSS-MOSFIRE
• The Structure of the Milky Way's Bar Outside the Bulge
• The FourStar Galaxy Evolution Survey (ZFOURGE): ultraviolet to far-infrared catalogs, medium-bandwidth photometric redshifts with improved accuracy, stellar masses, and confirmation of quiescent galaxies to z~3.5
• Atlas and Catalog of Collisional Ring Galaxies
• Rings and Bent Chain Galaxies in the GEMS and GOOD Fields
• A New View of the Size-Mass Distribution of Galaxies: Using $r_{20}$ and $r_{80}$ instead of $r_{50}$
• Stellar disks of Collisional Ring Galaxies I. New multiband images, Radial intensity and color profiles, and confrontation with N-body simulations
• The most ancient spiral galaxy: a 2.6-Gyr-old disk with a tranquil velocity field
• Merger and Ring Galaxy Formation Rates at z<=2
• Evolution of Cold Streams and Emergence of the Hubble Sequence

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