# Self-consistent nonspherical isothermal halos embedding zero-thickness disks - Astrophysics > Cosmology and Nongalactic Astrophysics

Self-consistent nonspherical isothermal halos embedding zero-thickness disks - Astrophysics > Cosmology and Nongalactic Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: Disk-halo decompositions of galaxy rotation curves are generally performed ina parametric way. We construct self-consistent models of nonsphericalisothermal halos embedding a zero-thickness disk, by assuming that the halodistribution function is a Maxwellian. The method developed here can be used tostudy other physically-based choices for the halo distribution function and thecase of a disk accompanied by a bulge. In a preliminary investigation we notethe existence of a fine tuning between the scalelengths R {\Omega} and h,respectively characterizing the rise of the rotation curve and the luminosityprofile of the disk, which surprisingly applies to both high surface brightnessand low surface brightness galaxies. This empirical correlation identifies amuch stronger conspiracy than the one required by the smoothness and flatnessof the rotation curve disk-halo conspiracy. The self-consistent models arecharacterized by smooth and flat rotation curves for very differentdisk-to-halo mass ratios, hence suggesting that conspiracy is not as dramaticas often imagined. For a typical rotation curve, with asymptotically flatrotation curve at V {\infty} the precise value of which can also be treated asa free parameter, and a typical density profile of the disk, self-consistentmodels are characterized by two dimensionless parameters, which correspond tothe dimensional scales the disk mass-to-light ratio M-L and the halo centraldensity of standard disk-halo decompositions. We show that if the rotationcurve is decomposed by means of our self-consistent models, the disk-halodegeneracy is removed and typical rotation curves are fitted by models that arebelow the maximum-disk prescription. Similar results are obtained from a studyof NGC 3198. Finally, we quantify the flattening of the spheroidal halo, whichis significant, especially on the scale of the visible disk.

Author: ** N. C. Amorisco, G. Bertin**

Source: https://arxiv.org/