Publication Date:
2015-09-27
Description:
We investigate the spiral galaxy NGC 5394, which is strongly interacting with the larger spiral NGC 5395 (the pair is Arp 84), using optical integral-field spectroscopy from the CALIFA (Calar Alto Legacy Integral Field Area) survey. Spatially resolved equivalent widths, emission-line ratios and kinematics reveal many features related to the interaction, which has reshaped the galaxy. H α maps (with other diagnostic emission lines) show a concentrated central ( r 〈 1 kpc) starburst and three less luminous star-forming regions (one knot far out in the northern arm), and we estimate the dust-corrected total star-formation rate as 3.39 M yr – 1 . However, much of the galaxy, especially the outer tidal arms, has a post-starburst spectrum, evidence of a more extensive episode of star formation a few x 10 8 yr ago, triggered by the previous perigalacticon. The $\rm [N\,\small {II}]6584/H\,\alpha$ ratio is high in the nucleus, reaching 0.63 at the centre, which we interpret as related to high electron density ( n e ~= 750 cm – 3 from the $\rm [S\,\small {II}]{6717\over 6731}$ ratio). We find a central region of strong and blueshifted Na i (5890,5896) absorption, indicative of a starburst-driven outflow from the nucleus at an estimated velocity ~223 km s – 1 . The CALIFA data also show an annular region at radii 2.25–4 kpc from the nucleus, with elevated ratios of [N ii ], [O i ]6300 etc. to the Balmer lines – this is evidence of shock excitation, which might be the result of interaction-triggered gas inflow.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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