Dipping Our Toes in the Water: First Models of GD-1 as a Stream

Abstract

We present a model for producing tidal streams from disrupting progenitors in arbitrary potentials, utilizing the idea that the majority of stars escape from the progenitor's two Lagrange points. The method involves releasing test particles at the Lagrange points as the satellite orbits the host and dynamically evolving them in the potential of both host and progenitor. The method is sufficiently fast to allow large-dimensional parameter exploration using Monte Carlo methods. We provide the first direct modelling of 6-D stream observations -- assuming a stream rather than an orbit -- by applying our methods to GD-1. This is a kinematically cold stream spanning $60^{\circ }$ of the sky and residing in the outer Galaxy $\approx 15$ kpc distant from the centre. We assume the stream moves in a flattened logarithmic potential characterised by an asymptotic circular velocity $v_0$ and a flattening $q$. We recover values of normalisation $v_0$ = $227.2_{-18.2}^{+15.6}$ kms${}^{-1}$ and flattening $q$ = $0.91_{-0.1}^{+0.04}$, if the stream is assumed to leading, and $v_0$ = $226.5_{-17.0}^{+17.9}$ kms${}^{-1}$, $q$ = $0.90_{-0.09}^{+0.05}$, if it is assumed to be trailing. This can be compared to the values $v_0=224\pm 13$ kms${}^{-1}$ and $q=0.87_{-0.04}^{+0.07}$ obtained by Koposov et al (2010) using the simpler technique of orbit fitting. Although there are differences between stream and orbit fitting, we conclude that orbit fitting can provide accurate results given the current quality of the data, at least for this kinematically cold stream in this logarithmic model of the Galaxy.

10 pages, 6 figures, MNRAS, submitted

References in corpus (11)

• Detection of a 63 Degree Cold Stellar Stream in the Sloan Digital Sky Survey
• An Orphan in the "Field of Streams"
• "Skinny Milky Way, Please", says Sagittarius
• The Origin of the Bifurcation in the Sagittarius Stream
• The mechanics of tidal streams
• Milky Way Mass and Potential Recovery Using Tidal Streams in a Realistic Halo
• An Orbit Fit for the Grillmair Dionatos Cold Stellar Stream
• Inferring the gravitational potential of the Milky Way with a few precisely measured stars
• Fitting orbits to tidal streams
• Hamiltonians of Spherically Symmetric, Scale-Free Galaxies in Action-Angle Coordinates
• Extremely Flat Haloes and the Shape of the Galaxy

Cited by in corpus (7)

• The mass distribution and gravitational potential of the Milky Way
• The shape of the inner Milky Way halo from observations of the Pal 5 and GD-1 stellar streams
• Gaps in globular cluster streams: giant molecular clouds can cause them too
• The discovery of tidal tails around the globular cluster NGC 7492 with Pan-STARRS1
• The Dynamical Response of Dark Matter to Galaxy Evolution Affects Direct-Detection Experiments
• The Doubloon Models of Dark Haloes
• The influence of dark matter halo on the stellar stream asymmetry via dynamical friction