An off-centred bulge or a satellite? Hydrodynamical $N$-body simulations of the disc galaxy NGC 5474

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 $\simeq 1$ 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 co-planar 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 $10^8{M}_{\odot }$, also with the regular HI 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 HI distribution of NGC 5474 and the formation of its loose spiral arms. As a by-product of the simulations, we find that the peculiar over-density 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.

Accepted for publication on MNRAS. 22 pages, 19 figures. Comments are welcome

References in corpus (15)

• The Auriga Project: the properties and formation mechanisms of disc galaxies across cosmic time
• High-resolution mass models of dwarf galaxies from LITTLE THINGS
• The Structure of Classical Bulges And Pseudobulges: The Link Between Pseudobulges And Sersic Index
• High-resolution dark matter density profiles of THINGS dwarf galaxies: Correcting for non-circular motions
• Legacy ExtraGalactic UV Survey (LEGUS) with The Hubble Space Telescope. I. Survey Description
• The stellar mass-halo mass relation of isolated field dwarfs: a critical test of $\Lambda$CDM at the edge of galaxy formation
• CO-dark gas and molecular filaments in Milky Way type galaxies
• GHASP : An Halpha kinematic survey of spiral and irregular galaxies - VI. New Halpha data cubes for 108 galaxies
• N-body simulations of gravitational dynamics
• Powering galactic super-winds with small-scale AGN winds
• Stellar population synthesis models between 2.5 and 5 μm based on the empirical IRTF stellar library
• The SLUGGS Survey: stellar masses and effective radii of early-type galaxies from Spitzer Space Telescope 3.6$\mu$m imaging
• The effect of tides on the Sculptor dwarf spheroidal galaxy
• Bulgeless galaxies in the COSMOS field: environment and star formation evolution at $z<1$
• The strange case of the peculiar spiral galaxy NGC5474. New pieces of a galactic puzzle

Cited by in corpus (6)

• Galactic coronae in Milky Way-like galaxies: the role of stellar feedback in gas accretion
• Dancing in the void: hydrodynamical N-body simulations of the extremely metal poor galaxy DDO 68
• Spatial regularity of the young stellar population in spiral arms of late type galaxies NGC 895, NGC 5474, and NGC 6946
• The Smallest Scale of Hierarchy Survey (SSH) III. Dwarf-dwarf satellite merging phenomena in the low-mass regime
• A Deep Census of Outlying Star Formation in the M101 Group
• A Dynamical Model of the M101 / NGC 5474 Encounter