Investigating the need for a robust ultraviolet filter set aboard the Habitable Worlds Observatory

High-resolution, ultraviolet imaging is often unavailable across the sky, even in heavily studied fields such as the Chandra Deep Field - South. The Habitable Worlds Observatory is one of two upcoming missions with the possibility of significant ultraviolet (UV) capabilities and the only one early enough in development to consider suggestions to its design. We conduct an initial study of how current common UV filter sets affect the results of spectral energy distribution fitting for the estimation of galaxy parameters. This initial look is intended to motivate the need for future, more robust spectral energy distribution fitting of mock galaxies. We compare the broad near UV and far UV filters used by the GALEX mission to the three narrower Swift Ultraviolet Optical Telescope (UVOT) filters. We find that the GALEX filters result in larger errors when calculating the UV β parameter compared with UVOT and provide little constraint on the star formation age of a galaxy. We further note the ability of the UVOT filters to investigate the 2175-Å attenuation bump; GALEX has a reduced capacity to trace this same feature. Ultimately, we recommend that to optimize the effectiveness of Habitable Worlds Observatory’s ultraviolet capacity for transformative astrophysics, a minimum of a Far-UV (FUV) filter with three medium band Near-UV (NUV) filters should be adopted. This will combine the power of GALEX’s wavelength range with the finer sampling of UVOT around an important dust feature.