Astronomy and Astrophysics – Astrophysics – Galaxy Astrophysics
Scientific paper
2010-02-02
Astronomy and Astrophysics
Astrophysics
Galaxy Astrophysics
15 pages, 9 figures, accepted to ApJ
Scientific paper
We examine two extreme models for the build-up of the stellar component of luminous elliptical galaxies. In one case, we assume the build-up of stars is dissipational, with centrally accreted gas radiating away its orbital and thermal energy; the dark matter halo will undergo adiabatic contraction and the central dark matter density profile will steepen. For the second model, we assume the central galaxy is assembled by a series of dissipationless mergers of stellar clumps that have formed far from the nascent galaxy. In order to be accreted, these clumps lose their orbital energy to the dark matter halo via dynamical friction, thereby heating the central dark matter and smoothing the dark matter density cusp. The central dark matter density profiles differ drastically between these models. For the isolated elliptical galaxy, NGC 4494, the central dark matter densities follow the power-laws r^(-0.2) and r^(-1.7) for the dissipational and dissipationless models, respectively. By matching the dissipational and dissipationless models to observations of the stellar component of elliptical galaxies, we examine the relative contributions of dissipational and dissipationless mergers to the formation of elliptical galaxies and look for observational tests that will distinguish between these models. Comparisons to strong lensing brightest cluster galaxies yield median M*/L_B ratios of 2.1+/-0.8 and 5.2+/-1.7 at z=0.39 for the dissipational and dissipationless models, respectively. For NGC 4494, the best-fit dissipational and dissipationless models have M*/L_B=2.97 and 3.96. Comparisons to expected stellar mass-to-light ratios from passive evolution and population syntheses appear to rule out a purely dissipational formation mechanism for the central stellar regions of giant elliptical galaxies.
Lackner Claire N.
Ostriker Jeremiah P.
No associations
LandOfFree
Dissipational versus Dissipationless Galaxy Formation and the Dark Matter Content of Galaxies does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Dissipational versus Dissipationless Galaxy Formation and the Dark Matter Content of Galaxies, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Dissipational versus Dissipationless Galaxy Formation and the Dark Matter Content of Galaxies will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-600679