A Systematic Study of Velocity Differences between [OIII] and Hα in CALIFA Galaxies
Anika Beer, Jakob Walcher, Genoveva Micheva
Leibniz-Institut für Astrophysik Potsdam (AIP)
We aim to quantify possible systematic differences in the kinematics of optical emission lines from species with different ionization potential, with emphasis on [OIII]λ5007 and Hαλ6563. We use the IFU data from the CALIFA survey and our dataset contains around 9,000 HII regions in over 300 galaxies. We find that [OIII] is often blueshifted with respect to Hα by amounts between 5 and 100 km/s. In some cases this is a local effect (i.e. per HII region), but in others we detect galaxy-wide trends, such as systematically slower rotation in [OIII] than in Hα. The prevalence and sizes of these velocity differences seem to cor- relate with the metallicity and the star formation rate of the HII region. The outcome of this study could have, on the one hand, practical implications for precise kinematics of the ionized ISM, and, on the other hand, may provide a new avenue to understand the structure of the ionized ISM.