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Abstract The Sloan Digital Sky Survey MaNGA program has now obtained integral field spectroscopy for over 10,000 galaxies in the nearby universe. We use the final MaNGA data release DR17 to study the correlation between ionized gas velocity dispersion and galactic star formation rate, finding a tight correlation in whichσHαfrom galactic Hiiregions increases significantly from ∼18–30 km s−1, broadly in keeping with previous studies. In contrast,σHαfrom diffuse ionized gas increases more rapidly from 20–60 km s−1. Using the statistical power of MaNGA, we investigate these correlations in greater detail using multiple emission lines and determine that the observed correlation ofσHαwith local star formation rate surface density is driven primarily by the global relation of increasing velocity dispersion at higher total star formation rate, as are apparent correlations with stellar mass. Assuming Hiiregion models consistent with our finding thatσ[OIII]<σHα<σ[O I], we estimate the velocity dispersion of the molecular gas in which the individual Hiiregions are embedded, finding valuesσMol= 5–30 km s−1consistent with ALMA observations in a similar mass range. Finally, we use variations in the relation with inclination and disk azimuthal angle to constrain the velocity dispersion ellipsoid of the ionized gasσz/σr= 0.84 ± 0.03 andσϕ/σr= 0.91 ± 0.03, similar to that of young stars in the Galactic disk. Our results are most consistent with the theoretical models in which turbulence in modern galactic disks is driven primarily by star formation feedback.
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This content will become publicly available on June 12, 2026
DIISC-V: Variations in H α -to-FUV Star Formation Rate Ratios Across Star-forming Regions in Nearby Galaxies
Abstract We present the variations in far-ultraviolet (FUV) and Hαstar formation rates (SFR), SFRUVand SFRHα, respectively, at subkiloparsec scales in 11 galaxies as part of the Deciphering the Interplay between the Interstellar Medium, Stars, and the Circumgalactic medium survey. Using archival GALEX FUV imagery and Hα+[Nii] narrowband images obtained with the Vatican Advanced Technology Telescope, we detect a total of 1335 (FUV-selected) and 1474 (Hα-selected) regions of recent high-mass star formation, respectively. We find the Hα-to-FUV SFR ratios tend to be lower primarily for FUV-selected regions, where SFRHαgenerally underestimates the SFR by an average factor of 2–3, for SFR < 10−4M⊙yr−1. In contrast, the SFRs are generally observed to be consistent for Hα-selected regions. This discrepancy arises from morphological differences between the two indicators. Extended FUV morphologies and larger areas covered by FUV-only regions, along with decreasing overlap between FUV clumps and compact Hiiregions withR/R25suggest that stochastic sampling of the initial mass function may be more pronounced in the outer regions of galaxies. Our observed Hα-to-FUV SFR ratios are also consistent with stochastic star formation model predictions. However, using larger apertures that include diffuse FUV emission results in an offset of 1 dex between SFRHαand SFRUV, suggesting that the observed low Hα-to-FUV SFR ratios in galaxies are likely caused by diffuse FUV emission, which can contribute ∼60%–90% to the total FUV flux.
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- Award ID(s):
- 2108159
- PAR ID:
- 10629206
- Publisher / Repository:
- The Astrophysical Journal
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 986
- Issue:
- 2
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 145
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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