Travel support for two observers to conduct astronomical observations at the LBT during November 2019

• Applicant: Privatdozent Dr. Dominik Bomans
• Subject Area: Astrophysics and Astronomy
• Term: Funded in 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 438825671

A) Unevolved galaxies should have low-masses, low-metallicities, and a strong, hard radiation fields due to many massive stars. Therefore, they should emit strong UV continuum and extremely strong emission lines. At high redshifts these dwarfish galaxies are extremely hard to study, so we need good proxies for a more detailed looks at the involved processes. Such extreme emission line galaxies and extremely blue galaxies exist even at low redhift and are prone to show lines He II emission, requiring a hard radiation fields as could be provided by very massive, low metallicity, rotating stars. The discovery of nebular CIII] and CIV emission lines in z~7 galaxies further emphasized the question for the nature of the hard radiation field needed for this emission lines to occur. Since not only very massive, low metallicity stars, but also massive X-ray binaries, accreting supermassive black hole, and even shocks may be possible sources of the hard continuum photons, the definition of a set of very local proxies is imperative, where spatial resolution and sensitivity allow a detailed study of the gas and individual ionization sources. Another intriguing class of extreme emission line galaxies are green peas, emission line galaxies with extremely strong [OIII] lines. These galaxies appear to provide good conditions for the escape of Lyman continuum radiation. We study all 3 classes of promising proxies for high redshift (proto-)galaxies in 3 observing programs at the LBT. B) The ionization process of outflows and diffuse ionized gas halos in disk galaxies is still a puzzle. While a connection to star formation activity seems to be well established (but not fully understood), the ionization mechanism of the observed ionized gas is still unclear: while photo-ionization certainly contributes, the observed line ratios and their change with distance from the disk require changes in the photon field and the presence of an additional currently unknown heating mechanism. C) Spitzer and also HERSCHEL revealed a number of small bubbles in the Milky Way. In a couple of cases, it was possible to take optical spectra of the apparent central stars, which surprisingly often turned out to be evolved massive stars (Wolf-Rayet stars, candidates for Luminous Blue Variables, and OB supergiants). We target the bubbles and their central stars with LUCI NIR spectroscopy to classify the highly absorbed part of the bubbles and investigate their evolutionary state and their central stars in a more unbiased way.

• DFG Programme: Research Grants