Machado de Assis

Abstract

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Late-type galaxies observed with SAURON: two-dimensional stellar and emission-line kinematics of 18 spirals

“…The presence of bulges is not ubiquitous and their nature can be ambiguous. Evidence has accumulated in the past years showing that many bulges have a disc-like, sometimes exponential radial fall-off of the stellar density (Andredakis & Sanders 1994;Andredakis, Peletier & Balcells 1995;de Jong 1995;Courteau, de Jong & Broeils 1996;Seigar et al 2002;MacArthur, Courteau & Holtzmann 2003). Numerical simulations seem to suggest that the dissolution of bars inside the discs may trigger the formation of three-dimensional stellar structures with roughly exponential profiles (Combes et al 1990;Pfenniger & Norman 1990;Raha et al 1991;Norman, Sellwood & Hasan 1996); this could mean that some bulges form through the evolution of dynamical instabilities in the disc.…”

Simulating galaxy evolution

“…For example, secular evolution can form small bulges but not the massive objects of early type galaxies. Observational evidence that bulge and disk scale lengths are correlated favors a secular evolution origin of bulges for late-type spirals [23]. The ubiquity of bars, which are efficient at torquing accreting gas and driving the gas inwards to form a central bulge, also suggests that secular evolution must have played a significant role in bulge formation.…”