| Issue |
A&A
Volume 668, December 2022
|
|
|---|---|---|
| Article Number | A179 | |
| Number of page(s) | 13 | |
| Section | Extragalactic astronomy | |
| DOI | https://doi.org/10.1051/0004-6361/202243944 | |
| Published online | 19 December 2022 | |
Unveiling the formation of NGC 2915 with MUSE: A counter-rotating stellar disk embedded in a disordered gaseous environment⋆
1
Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei 230026, PR China
e-mail: hzhang18@ustc.edu.cn
2
School of Astronomy and Space Science, University of Science and Technology of China, Hefei 230026, PR China
3
Department of Astronomy and Astrophysics, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA
e-mail: ymtang@ucsc.edu
4
School of Astronomy and Space Science, Nanjing University, Nanjing 210093, PR China
5
Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education, Nanjing 210093, PR China
Received:
4
May
2022
Accepted:
12
October
2022
NGC 2915 is a unique nearby galaxy that is classified as an isolated blue compact dwarf based on its optical appearance but has an extremely extended H I gas disk with prominent Sd-type spiral arms. To unveil the starburst-triggering mystery of NGC 2915, we performed a comprehensive analysis of deep VLT/MUSE integral field spectroscopic observations that cover the star-forming region in the central kiloparsec of the galaxy. We find that episodes of bursty star formation have recurred in different locations throughout the central region, and the most recent one peaked around 50 Myr ago. The bursty star formation has significantly disturbed the kinematics of the ionized gas but not the neutral atomic gas, which implies that the two gas phases are largely spatially decoupled along the line of sight. No evidence for an active galactic nucleus is found based on the classical line-ratio diagnostic diagrams. The ionized gas metallicities have a positive radial gradient, which confirms the previous study based on several individual H II regions and may be attributed to both the stellar feedback-driven outflows and metal-poor gas inflow. Evidence for metal-poor gas infall or inflow includes discoveries of high-speed collisions between gas clouds of different metallicities, localized gas metallicity drops and unusually small metallicity differences between gas and stars. The central stellar disk appears to be counter-rotating with respect to the extended H I disk, implying that the recent episodes of bursty star formation have been sustained by externally accreted gas.
Key words: galaxies: individual: NGC 2915 / galaxies: dwarf / galaxies: kinematics and dynamics / galaxies: star clusters: general
© The Authors 2022
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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