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Colloquium: Self-consistent UV emission and absorption line diagnostics
May 3 @ 10:30 am - 5:00 pm
UV diagnostics are critical for the study of high-redshift galaxies, given that commonly-used optical emission line diagnostics become observationally unavailable as they redshift out of wavelength regimes accessible from the ground. UV emission in galaxies is dominated by flux produced by young massive stars, along with line and continuum emission from ionized gas in the ISM. In this work, I assess the diagnostic potential of both absorption and emission features in the UV, using models that simultaneously and self-consistently consider stellar and nebular emission. I measure the metallicity sensitivity of established UV stellar absorption indices, and identify those that include a significant contribution from nebular emission. I identify combinations of strong emission lines that constrain metallicity and ionization parameter, and develop UV versions of the canonical â€œBPTâ€ diagram. For nebular emission lines that overlap with known stellar wind features like C IV Î»Î»1548,1551, I quantify the relative contribution from nebular and stellar emission to line ratios. I evaluate the diagnostics against observations of local galaxies and galaxies at high redshift and summarize the best diagnostic choices and the associated redshift range for low-, mid-, and high-resolution rest-UV spectroscopy in preparation for the launch of JWST.