We present new and archival atomic hydrogen (H i) observations of 15 of the most massive spiral galaxies in the local Universe (${M_{\star }}\gt 10^{11} \, {\rm M}_\odot$). From 3D kinematic modeling of the datacubes, we derive extended H i rotation curves, and from these, we estimate masses of the dark matter halos and specific angular momenta of the discs. We confirm that massive spiral galaxies lie at the upper ends of the Tully–Fisher relation (mass vs velocity, M ∝ V4) and Fall relation (specific angular momentum vs mass, j ∝ M0.6), in both stellar and baryonic forms, with no significant deviations from single power laws. We study the connections between baryons and dark matter through the stellar (and baryon)-to-halo ratios of mass fM ≡ M⋆/Mh and specific angular momentum fj, ⋆ ≡ j⋆/jh and fj, bar ≡ jbar/jh. Combining our sample with others from the literature for less massive disc-dominated galaxies, we find that fM rises monotonically with M⋆ and Mh (instead of the inverted-U shaped fM for spheroid-dominated galaxies), while fj, ⋆ and fj, bar are essentially constant near unity over four decades in mass. Our results indicate that disc galaxies constitute a self-similar population of objects closely linked to the self-similarity ofmore »
In our hierarchical structure-formation paradigm, the observed morphological evolution of massive galaxies – from rotationally supported discs to dispersion-dominated spheroids – is largely explained via galaxy merging. However, since mergers are likely to destroy discs, and the most massive galaxies have the richest merger histories, it is surprising that any discs exist at all at the highest stellar masses. Recent theoretical work by our group has used a cosmological, hydrodynamical simulation to suggest that extremely massive (M* > 1011.4 M⊙) discs form primarily via minor mergers between spheroids and gas-rich satellites, which create new rotational stellar components and leave discs as remnants. Here, we use UV-optical and H i data of massive galaxies, from the Sloan Digital Sky Survey, Galaxy Evolution Explorer, Dark Energy Camera Legacy Survey (DECaLS), and Arecibo Legacy Fast ALFA surveys, to test these theoretical predictions. Observed massive discs account for ∼13 per cent of massive galaxies, in good agreement with theory (∼11 per cent). ∼64 per cent of the observed massive discs exhibit tidal features, which are likely to indicate recent minor mergers, in the deep DECaLS images (compared to ∼60 per cent in their simulated counterparts). The incidence of these features is at least four times higher than in low-mass discs, suggesting that, more »
- Publication Date:
- NSF-PAR ID:
- 10362416
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 511
- Issue:
- 1
- Page Range or eLocation-ID:
- p. 607-615
- ISSN:
- 0035-8711
- Publisher:
- Oxford University Press
- Sponsoring Org:
- National Science Foundation
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