English

Properties of the Lower Segment of M31's North West Stream

Astrophysics of Galaxies 2025-06-23 v2

Abstract

We present a kinematic and spectroscopic analysis of 40 red giant branch stars, in 9 fields, exquisitely delineating the lower segment of the North West Stream (NW-K2), which extends for \sim80 kpc from the centre of the Andromeda galaxy. We measure the stream's systemic velocity as -439.33.8+4.1^{+4.1}_{-3.8} km/s with a velocity dispersion = 16.43.8+5.6^{+5.6}_{-3.8} km/s that is in keeping with its progenitor being a dwarf galaxy. We find no detectable velocity gradient along the stream. We determine -1.3±\pm0.1 \le <[Fe/H]spec_{\rm spec}> \le -1.2±\pm0.8 but find no metallicity gradient along the stream. We are able to plausibly associate NW-K2 with the globular clusters PandAS-04, PandAS-09, PAndAS-10, PAndAS-11, PandAS-12 but not with PandAS-13 or PandAS-15 which we find to be superimposed on the stream but not kinematically associated with it.

Keywords

Cite

@article{arxiv.2409.07410,
  title  = {Properties of the Lower Segment of M31's North West Stream},
  author = {Janet Preston and Denis Erkal and Michelle L. M. Collins and Rodrigo Ibata and R. Michael Rich},
  journal= {arXiv preprint arXiv:2409.07410},
  year   = {2025}
}

Comments

14 pages, 8 figures