The SAMI Galaxy Survey: shocks and outflows in a normal star-forming galaxy

Abstract

We demonstrate the feasibility and potential of using large integral field spectroscopic surveys to investigate the prevalence of galactic-scale outflows in the local Universe. Using integral field data from the Sydney-AAO Multi-object Integral field spectrograph (SAMI) and the Wide Field Spectrograph, we study the nature of an isolated disk galaxy, SDSS J090005.05+000446.7 (z = 0.05386). In the integral field datasets, the galaxy presents skewed line profiles changing with position in the galaxy. The skewed line profiles are caused by different kinematic components overlapping in the line-of-sight direction. We perform spectral decomposition to separate the line profiles in each spatial pixel as combinations of (1) a narrow kinematic component consistent with HII regions, (2) a broad kinematic component consistent with shock excitation, and (3) an intermediate component consistent with shock excitation and photoionisation mixing. The three kinematic components have distinctly different velocity fields, velocity dispersions, line ratios, and electron densities. We model the line ratios, velocity dispersions, and electron densities with our MAPPINGS IV shock and photoionisation models, and we reach remarkable agreement between the data and the models. The models demonstrate that the different emission line properties are caused by major galactic outflows that introduce shock excitation in addition to photoionisation by star-forming activities. Interstellar shocks embedded in the outflows shock-excite and compress the gas, causing the elevated line ratios, velocity dispersions, and electron densities observed in the broad kinematic component. We argue from energy considerations that, with the lack of a powerful active galactic nucleus, the outflows are likely to be driven by starburst activities. Our results set a benchmark of the type of analysis that can be achieved by the SAMI Galaxy Survey on large numbers of galaxies.

Shocked gas in IRAS F17207-0014: ISM collisions and outflows

“…Rich et al 2010Rich et al , 2011Ho et al 2014), but we see no such trend here. It is possible that the lack of a correlation simply means that the shock velocity is not related to the turbulent velocity of the gas.…”

“…Mixing between AGN and star formation can also exist (Davies et al 2014b), but such mixing increases the [O III]/Hβ ratio more strongly, shifting points towards the Seyfert region of the diagnostic diagrams. By comparing these ionization line ratios in spatially-resolved spectroscopy to photoionization and shock models, it is thus possible to map out the shocked regions and identify the relative contribution to the luminosity from shocks, star formation, and AGN (Monreal-Ibero et al 2006, 2010Sharp & Bland-Hawthorn 2010;Rich et al 2010Rich et al , 2011Westmoquette et al 2011;Freeland et al 2011;Davis et al 2012;Fogarty et al 2012;Yuan et al 2012;Vogt et al 2013;Ho et al 2014).…”

The SAMI Galaxy Survey: spatially resolving the environmental quenching of star formation in GAMA galaxies

“…Fluxes were extracted from each annular Voronoi bin using a modified version of lzifu, a pipeline designed by Ho et al (2014) and described in detail by Ho et al (2016b). lzifu incorporates stellar template fitting to the continuum using Penalized Pixel Fitting (pPXF; Cappellari & Emsellem 2004) and returns a multiple component Gaussian fit to the emission lines using the mpfit algorithm (Markwardt 2009).…”

The SAMI Galaxy Survey: early data release and first science

“…Recently Ho et al (2014) demonstrated this, using SAMI to discover and analyse a star-burst driven wind in an isolated disk galaxy. There are multiple kinematics components within this galaxy, which shows (1) a narrow kinematic component consistent with HII regions, (2) a broad kinematic component consistent with shock excitation, and (3) an intermediate component consistent with shock and photoionisation mixing.…”

“…Early science investigations have included studies such as detailed diagnostics of galactic winds (Fogarty et al 2012;Ho et al 2014), study of the kinematic morphology-density relation in clusters , star formation in dwarf galaxies (Richards et al 2014) and new analysis of galaxy scaling relations (Cortese et al 2014). Other ongoing work includes studies of spatially resolved star formation and how it is modulated with environment, dynamical mass estimates and the fundamental plane, radial age gradients and much more.…”