Exploring the HII regions of NGC925 as observed by SITELLE

Damien Beaulieu ( Université Laval )

Ionized gas is a key component for understanding star formation within galaxies. As part of SIGNALS, a survey that focuses on the emission regions of 40 nearby star-forming galaxies, NGC925 was observed with SITELLE, an imaging Fourier transform spectrometer for the optical spectrum built in Québec City (U. Laval and ABB) and installed at the Canada-France-Hawaii Telescope. This work mainly focuses on HII regions, establishing the physical characteristics of these regions will yield reliable insight regarding the influence of local environments on star formation and the different star forming mechanisms throughout the galaxy. At a distance of 9.2 Mpc, NGC925 is a fine candidate in SIGNALS framework, due to SITELLE’s high spatial resolution of 0.32”/pixel and large field of view of 11’ x 11’, HII regions are differentiated from one another over the whole galaxy. Using Hα to locate emission regions, we compute BPT diagrams of these regions using the emission line ratios [OIII]/Hβ, [NII]/Hα and [SII]/Hα. A catalog of HII regions is compiled from these diagrams. These early results reveal that NGC925 presents an asymmetric distribution of HII regions with different physical properties, suggesting that different mechanisms may be responsible for driving its star formation.