The haloes and environments of nearby galaxies (HERON) - II. The outer structure of edge-on galaxies


The HERON project is aimed at studying haloes and low surface brightness details near galaxies. In this second HERON paper we consider in detail deep imaging (down to surface brightness of ∼28 mag/arcsec2 in the r band) for 35 galaxies, viewed edge-on. We confirm a range of low surface brightness features previously described in the literature but also report new ones. We classify the observed outer shapes of the galaxies into three main types (and their prototypes): disc/diamond-like (NGC 891), oval (NGC 4302), and boxy (NGC 3628). We show that the shape of the outer disc in galaxies does not often follow the general 3D model of an exponential disc: 17 galaxies in our sample exhibit oval or even boxy isophotes at the periphery. Also, we show that the less flattened the outer disc is, the more oval or boxy its structure. Many galaxies in our sample have an asymmetric outer structure. We propose that the observed diversity of the galaxy outer shapes is defined by the merger history and its intensity: if no recent multiple minor or single major merging took place, the outer shape is diamond-like or discy. On the contrary, interacting galaxies show oval outer shapes, whereas recent merging appears to transform the outer shape to boxy.© 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical SocietyWe thank the anonymous reviewer for helpful comments on the paper. This research has made use of the NASA/IPAC Infrared Science Archive (IRSA; http://irsa.ipac.caltech.edu/frontpage/), and the NASA/IPAC Extragalactic Data base (NED; https://ned.ipac .caltech.edu/), both of which are operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This research has made use of the HyperLeda data base (http://leda.univ-lyon1.fr/; Makarov et al. 2014). This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. RMR acknowledges financial support from his late father Jay Baum Rich. JR acknowledges financial support from the State Agency for Research of the Spanish MCIU through the ‘Center of Excellence Severo Ochoa’ award to the Instituto de Astrof´ısica de Andaluc´ıa (SEV-2017-0709) and support from the grant RTI2018-096228-B-C31 (MICIU/FEDER, EU). PU acknowledges financial support from the Russian Science Foundation (grant no. 19-12-00145)Peer reviewe

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oai:digital.csic.es:10261/211500Last time updated on 5/24/2020

This paper was published in Digital.CSIC.

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