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A simple and accurate approximation for the Q stability parameter in multicomponent and realistically thick discs

Alessandro Romeo (Institutionen för rymd- och geovetenskap, Radioastronomi och astrofysik) ; Niklas Falstad (Institutionen för rymd- och geovetenskap, Radioastronomi och astrofysik)
Monthly notices of the Royal Astronomical Society (0035-8711). Vol. 433 (2013), 2, p. 1389-1397.
[Artikel, refereegranskad vetenskaplig]

In this paper, we propose a Q stability parameter that is more realistic than those commonly used, and is easy to evaluate (see equation 19). Using our QN parameter, you can take into account several stellar and/or gaseous components as well as the stabilizing effect of disc thickness, you can predict which component dominates the local stability level, and you can do all that simply and accurately. To illustrate the strength of QN, we analyse the stability of a large sample of spirals from The H i Nearby Galaxy Survey (THINGS), treating stars, H i and H2 as three distinct components. Our analysis shows that H2 plays a significant role in disc (in)stability even at distances as large as half the optical radius. This is an important aspect of the problem, which was missed by previous (two-component) analyses of THINGS spirals. We also show that H i plays a negligible role up to the edge of the optical disc and that the stability level of THINGS spirals is, on average, remarkably flat and well above unity.



Denna post skapades 2013-07-04. Senast ändrad 2016-06-27.
CPL Pubid: 179849

 

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