An off-centred bulge or a satellite? Hydrodynamical N-body simulations of the disc galaxy NGC 5474. Issue 2 (27th November 2020)

• Record Type: Journal Article
• Authors: Pascale, R; Bellazzini, M; Tosi, M; Annibali, F; Marinacci, F; Nipoti, C
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 501:Issue 2(2021)
• Page Start: 2091
• Page End: 2111
• Publication Date: 2020-11-27
• Subjects: galaxies: individual: NGC 5474 -- galaxies: interactions -- galaxies: kinematics and dynamics -- galaxies: peculiar -- galaxies: stellar content -- galaxies: structure; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa3699
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We present dynamical models of the star-forming galaxy NGC 5474 based on N -body hydrodynamical numerical simulations. We investigate the possible origin of the compact round stellar structure, generally interpreted as the bulge of the galaxy, but unusually off-set by ${\simeq} 1\, {\rm kpc}$ in projection from the visual and the kinematic centres of both the star and the gas discs. We argue that it is very unlikely that the putative bulge is in a coplanar orbit in the disc plane, showing that such a configuration would be hardly compatible with its smooth and regular spatial distribution, and, in case its mass is above $10^8\, \mathrm{ M}_{\odot }$, also with the regular ${\rm H\, {\small I}}$ velocity field of NGC 5474. Instead, if the putative bulge is in fact an early-type satellite galaxy orbiting around NGC 5474, not only the off-set can be easily produced by projection effects, but our simulations suggest that the gravitational interaction between the two systems can explain also the warped ${\rm H\, {\small I}}$ distribution of NGC 5474 and the formation of its loose spiral arms. As a by-product of the simulations, we find that the peculiar overdensity of old stars detected in the south-west region of NGC 5474 may be explained with the interaction between NGC 5474 and a smaller stellar system, unrelated to the putative bulge, accreted in the disc plane.