Measuring interstellar temperature and ionization variations using observations of faint diffuse [OII] emission

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). The interstellar medium (ISM) plays a vital role in the ongoing cycle of stellar birth and death, and galactic evolution. However the role of interstellar matter, from how its properties are influenced by stars to how, in turn, its properties influence star formation is poorly understood. Dr. Edwin Mierkiewicz and his team will carry out a program of [OII] observations which will (1) provide the only opportunity to separate unambiguously variations in temperature from variations in ionization conditions in the warm ionized medium (WIM) of our Galaxy and (2) confirm whether H-alpha, [NII], and [SII] data can provide reliable temperature information about diffuse ionized gas in our own and other galaxies. This research uses innovative spectroscopic techniques to address outstanding questions of heating, and of temperature and ionization variations in the WIM raised by Wisconsin H-Alpha Mapper (WHAM) observations, but which WHAM and other available astronomical instruments are not suited to address. Beyond its intrinsic interest, a thorough understanding of the WIM is important for understanding the composition and nature of the interstellar medium, and the primary sources of ionization and heating within the disk and halo of our Galaxy.Dr. Mierkiewicz and his team have a long history of student training in astrophysics instrumentation and observational techniques. Graduate and undergraduate students will participate in all phases of this work. The graduate student involvement will lead to a Ph.D. thesis. Dr. Mierkiewicz is the director of the separately NSF-funded University of Wisconsin Astronomy Research Experiences for Undergraduates (REU) program. This program values diversity among its participants and works to involve students from underrepresented groups and small colleges in astrophysics research. Summer REU students will participate in this work.