Dynamics of Starbursting Dwarf Galaxies: I Zw 18
Federico Lelli (1), Marc Verheijen (1), Filippo Fraternali (1, 2), and Renzo Sancisi (1, 3) ((1) University of Groningen, (2) University of, Bologna, (3) INAF - Observatory of Bologna)

TL;DR
This study reveals that I Zw 18, a prototypical blue compact dwarf galaxy, hosts a compact, fast-rotating HI disk with high column densities, suggesting it resembles a miniature high-surface-brightness disk galaxy and likely results from a dwarf-dwarf merger.
Contribution
The paper provides detailed dynamical analysis of I Zw 18's HI gas, showing it differs from typical dwarf irregulars and may be a high-surface-brightness disk galaxy formed by a merger.
Findings
HI forms a compact, fast-rotating disk with high column densities.
Mass models indicate baryons may dominate inner gravitational potential.
Extended HI emission suggests recent dwarf-dwarf interaction.
Abstract
I Zw 18 is a prototype Blue Compact Dwarf (BCD), characterized by a strong starburst and extremely low metallicity (Z ~ 0.02 Zsun). It has long been considered a candidate young galaxy in the Local Universe, but recent studies indicate the presence of old stars. We analysed archival VLA observations of the 21 cm line and found that the HI associated to the starburst region forms a compact fast-rotating disk. The HI column densities are very high, up to ~50-100 Msun/pc^2 (~0.6-1.2 x 10^22 atoms/cm^2). The rotation curve is flat with a steep rise in the inner parts, indicating the presence of a strong central concentration of mass. Mass models with a dark matter halo show that baryons may dominate the gravitational potential in the inner regions. A radial inflow/outflow motion of ~15 km/s is also present. I Zw 18 appears structurally different from typical dwarf irregulars in terms of gas…
Peer Reviews
No public reviews on file for this paper yet. If you reviewed it on a platform where reviews are public (OpenReview, ICLR, NeurIPS, ICML), you can paste yours below so the community can read it here.
Videos
No videos yet. Explain this paper in a talk, walkthrough, or lecture? Add one.
Taxonomy
TopicsAstronomy and Astrophysical Research · Stellar, planetary, and galactic studies · Galaxies: Formation, Evolution, Phenomena
