arXiv subjects

Victor P. Debattista

Publications and source records attributed to Victor P. Debattista.

168 records · Page 10Linked to original sources

arXiv2000

Constraints from Dynamical Friction on the Dark Matter Content of Barred Galaxies

We show that bars in galaxy models having halos of moderate density and a variety of velocity distributions all experience a strong drag from dynamical friction unless the halo has large angular momentum in the same sense as the disk. The frictional drag decreases the bar pattern speed, driving the corotation point out to distances well in excess of those estimated in barred galaxies. The halo angular momentum required to avoid strong braking is unrealistically large, even when rotation is confined to the inner halo only. We conclude, therefore, that bars are able to maintain their observed high pattern speeds only if the halo has a central density low enough for the disk to provide most of the central attraction in the inner galaxy. We present evidence that this conclusion holds for all bright galaxies.

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arXiv1999

Fabry-Perot Absorption-Line Spectroscopy of NGC 7079

We report on absorption-line Fabry-Perot spectroscopy of the SB0 galaxy NGC 7079. Our data allow us to determine velocity and dispersion maps, which compare well with the results of slit observations. Our goals are to obtain a bar pattern speed and to determine the velocity ellipsoid as a function of radius; this is work in progress.

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arXiv1999

Warped Galaxies From Misaligned Angular Momenta

A galaxy disk embedded in a rotating halo experiences a dynamical friction force which causes it to warp when the angular momentum axes of the disk and halo are misaligned. Our fully self-consistent simulations of this process induce long-lived warps in the disk which mimic Briggs's rules of warp behavior. They also demonstrate that random motion within the disk adds significantly to its stiffness. Moreover, warps generated in this way have no winding problem and are more pronounced in the extended \h1 disk. As emphasized by Binney and his co-workers, angular momentum misalignments, which are expected in hierarchical models of galaxy formation, can account for the high fraction of warped galaxies. Our simulations exemplify the role of misaligned spins in warp formation even when the halo density is not significantly flattened.

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arXiv1997

Dynamical Friction and the Distribution of Dark Matter in Barred Galaxies

We use fully self-consistent N-body simulations of barred galaxies to show that dynamical friction from a dense dark matter halo dramatically slows the rotation rate of bars. Our result supports previous theoretical predictions for a bar rotating within a massive halo. On the other hand, low density halos, such as those required for maximum disks, allow the bar to continue to rotate at a high rate. There is somewhat meager observational evidence indicating that bars in real galaxies do rotate rapidly and we use our result to argue that dark matter halos must have a low central density in all high surface brightness disk galaxies, including the Milky Way. Bars in galaxies that have larger fractions of dark matter should rotate slowly, and we suggest that a promising place to look for such candidate objects is among galaxies of intermediate surface brightness.

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arXiv1996

The Bar-Halo Interaction in SB Galaxies

We describe fully self-consistent N-body experiments of barred galaxies with massive halos. A rotating bar is braked through dynamical friction with the halo, which occurs on a short time scale when the central density of the halo is high. On the other hand, friction is weak in a model with a central halo density low enough that the disk dominates the rotation curve in the inner parts; this model supports a fast bar for a Hubble time. We conclude that real barred galaxies in which the bar rotates rapidly, which is believed to be the rule, must have close to maximum disks.

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arXiv1996

Secular Evolution in Barred Galaxies

A strong bar rotating within a massive halo should lose angular momentum to the halo through dynamical friction, as predicted by Weinberg. We have conducted fully self-consistent, numerical simulations of barred galaxy models with a live halo population and find that bars are indeed braked very rapidly. Specifically, we find that the bar slows sufficiently within a few rotation periods that the distance from the centre to co-rotation is more than twice the semi-major axis of the bar. Observational evidence (meagre) for bar pattern speeds seems to suggest that this ratio typically lies between 1.2 to 1.5 in real galaxies. We consider, a number of possible explanations for this discrepancy between theoretical prediction and observation, and conclude that no conventional alternative seems able to account for it.

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