DIISC-V: Variations in H$α$-to-FUV Star Formation Rate Ratios Across Star-forming Regions in Nearby Galaxies
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2024
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| author | Padave, Mansi Borthakur, Sanchayeeta Jansen, Rolf A. Thilker, David Monkiewicz, Jacqueline Windhorst, Rogier A. |
| author_facet | Padave, Mansi Borthakur, Sanchayeeta Jansen, Rolf A. Thilker, David Monkiewicz, Jacqueline Windhorst, Rogier A. |
| contents | We present the variations in far-ultraviolet (FUV) and H$α$ star formation rates (SFR), SFR$_{UV}$ and SFR$_{Hα}$, respectively, at sub-kpc scales in 11 galaxies as part of the Deciphering the Interplay between the Interstellar Medium, Stars, and the Circumgalactic medium (DIISC) survey. Using archival GALEX FUV imagery and H$α$+[NII] narrowband images obtained with the Vatican Advanced Technology Telescope, we detect a total of 1335 (FUV-selected) and 1474 (H$α$-selected) regions of recent high-mass star formation, respectively. We find the H$α$-to-FUV SFR ratios tend to be lower primarily for FUV-selected regions, where SFR$_{Hα}$ generally underestimates the SFR by an average factor of 2-3, for SFR $<$ 10$^{-4}$ M$_{\odot}$ yr$^{-1}$. In contrast, the SFRs are generally observed to be consistent for H$α$-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 HII regions with $R/R_{25}$ suggest that stochastic sampling of the initial mass function may be more pronounced in the outer regions of galaxies. Our observed H$α$-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 SFR$_{Hα}$ and SFR$_{UV}$. This suggests that the observed low H$α$-to-FUV SFR ratios in galaxies are likely caused by diffuse FUV emission, which can contribute $\sim$60-90\% to the total FUV flux. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2407_16690 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | DIISC-V: Variations in H$α$-to-FUV Star Formation Rate Ratios Across Star-forming Regions in Nearby Galaxies Padave, Mansi Borthakur, Sanchayeeta Jansen, Rolf A. Thilker, David Monkiewicz, Jacqueline Windhorst, Rogier A. Astrophysics of Galaxies We present the variations in far-ultraviolet (FUV) and H$α$ star formation rates (SFR), SFR$_{UV}$ and SFR$_{Hα}$, respectively, at sub-kpc scales in 11 galaxies as part of the Deciphering the Interplay between the Interstellar Medium, Stars, and the Circumgalactic medium (DIISC) survey. Using archival GALEX FUV imagery and H$α$+[NII] narrowband images obtained with the Vatican Advanced Technology Telescope, we detect a total of 1335 (FUV-selected) and 1474 (H$α$-selected) regions of recent high-mass star formation, respectively. We find the H$α$-to-FUV SFR ratios tend to be lower primarily for FUV-selected regions, where SFR$_{Hα}$ generally underestimates the SFR by an average factor of 2-3, for SFR $<$ 10$^{-4}$ M$_{\odot}$ yr$^{-1}$. In contrast, the SFRs are generally observed to be consistent for H$α$-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 HII regions with $R/R_{25}$ suggest that stochastic sampling of the initial mass function may be more pronounced in the outer regions of galaxies. Our observed H$α$-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 SFR$_{Hα}$ and SFR$_{UV}$. This suggests that the observed low H$α$-to-FUV SFR ratios in galaxies are likely caused by diffuse FUV emission, which can contribute $\sim$60-90\% to the total FUV flux. |
| title | DIISC-V: Variations in H$α$-to-FUV Star Formation Rate Ratios Across Star-forming Regions in Nearby Galaxies |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2407.16690 |