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 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.
Description
[1407.2411] The SAMI Galaxy Survey: Shocks and Outflows in a normal star-forming galaxy
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