Action-space clustering on stellar stream data

University of Groningen research database (University of Groningen / Centre for Information Technology)

Abstract

Stream stars removed by tides from their progenitor satellite galaxy or globular cluster act as a group of test particles on neighbouring orbits, probing the gravitational field of the Milky Way. While constraints from individual streams have been shown to be susceptible to biases, combining several streams from orbits with various distances reduces these biases. We fit a common gravitational potential to multiple stellar streams simultaneously by maximizing the clustering of the stream stars in action space. We apply this technique to members of the GD-1, Palomar 5 (Pal 5), Orphan, and Helmi streams, exploiting both the individual and combined data sets. We describe the Galactic potential with a Stackel model, and vary up to five parameters simultaneously. We find that we can only constrain the enclosed mass, and that the strongest constraints come from the GD-1, Pal 5, and Orphan streams whose combined data set yields M(<20kpc)=2.96^+0.25^_-0.26_x10^11^M_{sun}_. When including the Helmi stream in the data set, the mass uncertainty increases to M(<20kpc)=3.12^+3.21^_-0.46_x10^11^M_{sun}_.

Authors 7

1. Stella Reino Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, Niels Bohrweg 2, NL-2333 CA Leiden, the Netherlands

2. Rossi E.M Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, Niels Bohrweg 2, NL-2333 CA Leiden, the Netherlands

3. Robyn E. Sanderson

   Flatiron Institute · University of Pennsylvania

   Affiliation as printed

   Department of Physics and Astronomy, University of Pennsylvania, 209 S 33rd St, Philadelphia, PA 19104, USA

   Center for Computational Astrophysics, Flatiron Institute, 162 5th Ave., New York, NY 10010, USA

4. Sellentin E Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, Niels Bohrweg 2, NL-2333 CA Leiden, the Netherlands

5. Amina Helmi

   University of Groningen

   Affiliation as printed

   Kapteyn Astronomical Institute, University of Groningen, PO Box 800, NL-9700 AV Groningen, the Netherlands

6. Koppelman H.H.

   University of Groningen

   Affiliation as printed

   Kapteyn Astronomical Institute, University of Groningen, PO Box 800, NL-9700 AV Groningen, the Netherlands

7. Sanjib Sharma

   The University of Sydney

   Affiliation as printed

   Sydney Institute for Astronomy, School of Physics, The University of Sydney, Sydney, NSW 2006, Australia