Toward the fabric of the Milky Way I. The density of disk streams from a local $250^3$ pc$^3$ volume
Sebastian Ratzenböck, João Alves, Emily L. Hunt, N úria Miret-Roig, Stefan Meingast, Torsten Möller
公開日: 2025/9/8
Abstract
We studied 12 disk streams found in a 250$^3$ pc$^3$ volume in the solar neighborhood, which we define as coeval and comoving stellar structures with aspect ratios greater than 3:1. Using \emph{Gaia} Data Release 3 data and the advanced clustering algorithms \texttt{SigMA} and \texttt{Uncover}, we identified and characterized these streams beyond the search volume, doubling, on average, their known populations. We estimate the number density of disk streams to be $\approx 820$ objects\,/\,kpc$^3$ (for $|Z| < 100$\,pc), or surface densities of $\approx 160$ objects\,/\,kpc$^2$. These estimates surpass N-body estimates by one to two orders of magnitude and challenge the prevailing understanding of their destruction mechanisms. Our analysis reveals that these 12 disk streams are dynamically cold with 3D velocity dispersions between 2 and 5\,km\,s$^{-1}$, exhibit narrow sequences in the Hertzsprung-Russell diagram, and are highly elongated with average aspect ratios of 7:1, extending up to several hundred parsecs. We find evidence suggesting that one of the disk streams, currently embedded in the Scorpius-Centaurus association, is experiencing disruption, likely due to the primordial gas mass of the association.