2024/07/23 by Mansi Padave, Padave, Mansi, Sanchayeeta Borthakur +9
Physics and Astronomy · #Astrophysics and Star Formation Studies #Astronomy and Astrophysical Research #Scientific Research and Discoveries
paper · pdf · doi:10.48550/arxiv.2407.16690
We present the variations in far-ultraviolet (FUV) and Hα star formation rates (SFR), SFRUV and SFRHα, 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 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 SFRHα 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 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 HII regions with R/R25 suggest 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 SFRHα and SFRUV. This suggests 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.