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arXiv · 2106.07060

Two interacting galaxies hiding as one, revealed by MaNGA

Barbara Mazzilli Ciraulo·Anne-Laure Melchior·Daniel Maschmann·Ivan Yu. Katkov·Anaëlle Halle·Françoise Combes·Joseph. D. Gelfand·Aisha Al Yazeedi
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Abstract

Given their prominent role in galaxy evolution, it is of paramount importance to unveil galaxy interactions and merger events and to investigate the underlying mechanisms. The use of high-resolution data makes it easier to identify merging systems, but it can still be challenging when the morphology does not show any clear galaxy-pair or gas bridge. Characterising the origin of puzzling kinematic features can help to reveal complicated systems. Here, we present a merging galaxy, MaNGA 1-114955, in which we highlighted the superimposition of two distinct rotating discs along the line of sight. These counter-rotating objects both lie on the star-forming main sequence but display perturbed stellar velocity dispersions. The main galaxy presents off-centred star formation as well as off-centred high-metallicity regions supporting the scenario of recent starbursts, while the secondary galaxy hosts a central starburst which coincides with an extended radio emission, in excess with respect to star formation expectations. Stellar mass as well as dynamical mass estimates agree towards a mass ratio within the visible radius of 9:1 for these interacting galaxies. We suggest we are observing a pre-coalescence stage of a merger. The primary galaxy has accreted gas through a past first pericentre passage about 1 Gyr ago, and more recently from the secondary gas-rich galaxy, which exhibits an underlying active galactic nucleus (AGN). Our results demonstrate how a galaxy can hide another one and the relevance of a multi-component approach to study ambiguous systems. We anticipate our method to be efficient at unveiling the mechanisms taking place in a sub-sample of galaxies observed by the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, all exhibiting kinematic features of puzzling origin in their gas emission lines.

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Barbara Mazzilli Ciraulo, Anne-Laure Melchior, Daniel Maschmann, Ivan Yu. Katkov, Anaëlle Halle, Françoise Combes, Joseph. D. Gelfand, Aisha Al Yazeedi. 2021-06-13. Two interacting galaxies hiding as one, revealed by MaNGA. https://doi.org/10.1051/0004-6361%2F202141319

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