3D Integral Field Observations of Ten Galactic Winds - I. Extended phase (>10 Myr) of mass/energy injection before the wind blows

摘要

We present 3D spectroscopic observations of a sample of 10 nearby galaxieswith the AAOmega-SPIRAL integral field spectrograph on the 3.9m AAT, thelargest survey of its kind to date. The double-beam spectrograph providesspatial maps in a range of spectral diagnostics: [OIII] 5007, H-beta, Mg-b,NaD, [OI] 6300, H-alpha, [NII] 6583, [SII] 6717, 6731. All of the objects inour survey show extensive wind-driven filamentation along the minor axis, inaddition to large-scale disk rotation. Our sample can be divided into eitherstarburst galaxies or active galactic nuclei (AGN), although some objectsappear to be a combination of these. The total ionizing photon budget availableto both classes of galaxies is sufficient to ionise all of the wind-blownfilamentation out to large radius. We find however that while AGNphotoionisation always dominates in the wind filaments, this is not the case instarburst galaxies where shock ionisation dominates. This clearly indicatesthat after the onset of star formation, there is a substantial delay (> 10 Myr)before a starburst wind develops. We show why this behavior is expected byderiving ``ionisation'' and dynamical timescales for both AGNs and starbursts.We establish a sequence of events that lead to the onset of a galactic wind.The clear signature provided by the ionisation timescale is arguably thestrongest evidence yet that the starburst phenomenon is an impulsive event. Awell-defined ionisation timescale is not expected in galaxies with a protractedhistory of circumnuclear star formation. Our 3D data provide importanttemplates for comparisons with high redshift galaxies.[Abridged]