The Role of Accretion in Forming the Galactic Halo：（吸积的作用形成了银河晕）.pdfVIP

The Role of Accretion in Forming the Galactic Halo Kathryn V. Johnston Institute for Advanced Study, Princeton, NJ 08540 8 9 Abstract. If the Galaxy formed hierarchically through the accretion 9 1 of smaller satellite galaxies we might hope to find signatures of this in t the halo’s phase-space distribution. I review theoretical ideas about what c form these signatures should take, concentrating in particular on the char- O acteristics of debris from the tidal disruption of satellites less than the 6 size of the Large Magellanic Clouds and at distances greater than 10 kpc. 2 Under these circumstances, tidal debris can remain aligned in streams of stars close to the satellite’s original orbit for the lifetime of the Galaxy 1 and we can understand the evolution of its structure analytically. This v 1 understanding has many applications to observations and I will discuss a 2 few examples: reconstructing the properties of a long-dead satellite from 4 its debris; measuring the mass loss rate from Galactic satellites through 0 the density of extra-tidal stars; and using observations of motions of tidal 1 stream stars to measure the mass and size of the Milky Way. 8 9 / h p - 1. Introduction o r t