No evidence for large-scale outflows in the extended ionized halo of ULIRG Mrk273

• Published in: Monthly notices of the Royal Astronomical Society. Letters 2016-06, Vol.459 (1), p.L16-L20
• Main Authors: Spence, R. A. W., Zaurín, J. Rodríguez, Tadhunter, C. N., Rose, M., Cabrera-Lavers, A., Spoon, H., Muñoz-Tuñón, C.
• Format: Article
• Language: English
• ISSN: 1745-3925; 1745-3933
• DOI: 10.1093/mnrasl/slw033

We present deep new Gran Telescopio Canarias (GTC) narrow-band images and William Herschel Telescope (WHT) long-slit spectroscopy of the merging system Mrk273 that show a spectacular extended halo of warm ionized gas out to a radius of ∼45 kpc from the system nucleus. Outside of the immediate nuclear regions (r > 6 kpc), there is no evidence for kinematic disturbance in the ionized gas: in the extended regions covered by our spectroscopic slits the emission lines are relatively narrow (full width at half-maximum, FWHM ≲ 350 km s−1) and velocity shifts small (|ΔV| ≲ 250 km s−1). This is despite the presence of powerful near-nuclear outflows (FWHM > 1000 km s−1; |ΔV| > 400 km s−1; r < 6 kpc). Diagnostic ratio plots are fully consistent with Seyfert 2 photoionization to the NE of the nuclear region, however to the SW the plots are more consistent with low-velocity radiative shock models. The kinematics of the ionized gas, combined with the fact that the main structures are aligned with low-surface-brightness tidal continuum features, are consistent with the idea that the ionized halo represents tidal debris left over from a possible triple-merger event, rather than a reservoir of outflowing gas.