paper

Broad [CII] line wings as tracer of molecular and multi-phase outflows in infrared bright galaxies

arXiv:1604.00185 · doi:10.3847/0004-637X/822/1/43

Abstract

We report a tentative correlation between the outflow characteristics derived from OH absorption at and [CII] emission at in a sample of 22 local and bright ultraluminous infrared galaxies (ULIRGs). For this sample we investigate whether [CII] broad wings are a good tracer of molecular outflows, and how the two tracers are connected. Fourteen objects in our sample have a broad wing component as traced by [CII], and all of these also show OH119 absorption indicative of an outflow (in 1 case an inflow). The other eight cases, where no broad [CII] component was found, are predominantly objects with no OH outflow or a low-velocity () OH outflow. The full width at half maximum (FWHM) of the broad [CII] component shows a trend with the OH119 blue-shifted velocity, although with significant scatter. Moreover, and despite large uncertainties, the outflow masses derived from OH and broad [CII] show a 1:1 relation. The main conclusion is therefore that broad [CII] wings can be used to trace molecular outflows. This may be particularly relevant at high redshift, where the usual tracers of molecular gas (like low-J CO lines) become hard to observe. Additionally, observations of blue-shifted Na I D absorption are available for ten of our sources. Outflow velocities of Na I D show a trend with OH velocity and broad [CII] FWHM. These observations suggest that the atomic and molecular gas phases of the outflow are connected.

arXiv commentaccepted for publication in ApJ

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