Evidence for universal structure in galactic halos

Abstract

The late infall of dark matter onto a galaxy produces structure (such as caustics) in the distribution of dark matter in the halo. We argue that such structure is likely to occur generically on length scales proportional to $l\sim t_0{v}_{rot}$, where $t_0$ is the age of the universe and $v_{rot}$ is the rotation velocity of the galaxy. A set of 32 extended galactic rotation curves is analyzed. For each curve, the radial coordinate is rescaled according to $r\to \tilde{r}\equiv r(v_0/v_{rot})$, where we choose $v_0=220km/s$. A linear fit to each rescaled rotation curve is subtracted, and the residuals are binned and averaged. The sample shows significant features near $\tilde{r}=40kpc$ and $\tilde{r}=20kpc$. This is consistent with the predictions of the self-similar caustic ring model of galactic halos.

4 pages, LaTeX, 1 epsf figure

References in corpus (1)

• Directional Sensitivity, WIMP Detection, and the Galactic Halo

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