Project duration: 1 year; potential to grow into a thesis project.
PI: Alaina Henry; http://www.alainahenry.com
Project Abstract:
All galaxy formation models require feedback to reproduce the properties of galaxies and the IGM. However, the true model for this self-regulation is a matter of great debate. It is widely hoped that constraints can come from observations of galactic outflows. Yet, despite significant efforts, there is no agreement on the properties of outflows and their relationship to their host galaxies. This difficulty arises due to necessary, but crude, assumptions about outflow metallicity, ionization state, and geometry. Consequently, if outflows are to serve as an effective diagnostic for feedback models, more work is needed.
We propose a way forward: by post-processing radiation-hydrodynamic simulations of galaxies with resonant- line radiation transport, we are producing mock observations of Lyman Alpha (LyA) and UV metal absorption lines. Using these simulated spectra, we will test the variety of methods for characterizing outflows. From the conventional column- density-based approach, to Lyman Alpha and metal line profile fitting with idealized geometries, we will compare outflow velocities and mass-loss rates with known quantities from the simulations. In this way, we will determine if COS data can recover outflow properties, and if some analysis techniques are preferred. Likewise, by varying noise, spectral resolution, and spectroscopic aperture sizes, we will determine the best strategies for interpreting existing measurements and planning future observations. By combining LyA with metals, we will obtain powerful constraints on gas with a range of physical conditions. This analysis will lead to more stringent tests for galaxy formation simulations.
A cartoon sketch showing how line profiles from the same outflow can change with viewing angle.
Simulated line profiles of Si II (left) and LyA (right), created by post-processing the SPHINX simulation (Rosdahl et al. 2018) with the new Monte Carlo radiation transport code, RASCAS.
