Disk-halo interaction in nearby galaxies – New SFRs and the bright (but low surface brightness) future of UV space astronomy

I present current efforts and future ultraviolet (UV) space missions aimed at determining the nature of disk-halo interactions and star formation in the nearby universe. I discuss new narrow-band H-alpha imaging for 24 nearby edge-on galaxies in the Continuum Halos in Nearby Galaxies – an EVLA Survey (CHANG-ES). I use the images in conjunction with the Wide-field Infrared Survey Explorer 22 micron imaging of the sample to estimate improved star formation rates (SFRs) using the updated recipe from Vargas et al. (2018). I will discuss new observational evidence for the use of a mid-IR extinction correction applied to SFR calibrations when used in edge-on or extremely dusty galaxies. The revised SFR estimates produce a newly-measured correlation between SFR and radio scale height, and further relationships between star formation and radio halo properties are explored. I identify a region of star formation located at extreme distance from the disk of NGC 4157, possibly ionized by a single O5.5 V star. The released H-alpha images from this work can be found at the CHANG-ES data release website, In the second part of this talk, I will discuss future UV space mission concepts currently being developed at the University of Arizona. The Hyperion Small Explorer mission (P.I., E. Hamden) will directly measure molecular hydrogen through its fluorescent line transitions in the UV. The main goals of Hyperion are to understand the behavior of molecular clouds at their surfaces, test cloud lifecycle theories, and understand the impact of cloud surface conditions on their interiors. Lastly, I will discuss a SmallSat concept (P.I., C. Vargas) that will map the elusive coronal gas phase in nearby galaxy halos via the O VI transition in the Far-UV. Both of these missions are enabled by major recent advancements in UV coatings and detector technology.

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