PI: Charles Hoopes, Johns Hopkins University, firstname.lastname@example.org
Address: 3400 N. Charles St., Baltimore, MD 21218, USA
CoI: Rene Walterbos, New Mexico State University
Title: The Ionization of the Diffuse Ionized Gas in M33
Abstract: Diffuse Ionized Gas (DIG) is an important link in the energy balance of the ISM. Most of the DIG is photoionized, with both field OB stars and photons leaking out of \HII regions contributing. Mechanical energy from supernovae also contributes, and there are indications of an extra heat source. Determining the ionization source is a key step toward understanding the star-gas cycle which drives the evolution of the ISM. We propose to obtain spectroscopy of DIG in M33, to achieve the following goals: \beginitemize \item determine the ionization state of helium in the DIG, a strong discriminator between ionization sources, \item use the \NII 5755Atemperature diagnostic line to look for extra heating, \item investigate mechanical heating through emission line widths, and \item close the loop on the ionization process by comparing the observed DIG spectrum with the local ionizing sources, using the spectral types of OB stars determined in our previous HST project. \enditemize This project will illuminate the ionization sources for the DIG, the prevalence of leaky \HII regions, and the escape of ionizing photons into the IGM.
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