2016/04/12 by Miho N. Ishigaki, M. N. Ishigaki, Narae Hwang +5 · 16 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Galaxies: Formation, Evolution, Phenomena #Globular cluster #Gravitational potential #Horizontal branch #Metallicity #Milky Way #Proper motion #Radial velocity #Spectral line #Spectrograph #Stars #Stellar, planetary, and galactic studies #astro-ph.GA #astro-ph.SR
paper · pdf · doi:10.3847/0004-637x/823/2/157
published in The Astrophysical Journal 823(2), 157 (IOP Publishing) · 14 pages, 13 figures. Accepted for publication in ApJ
arxiv created 2016/04/12 · openalex publication_date 2016/06/01 · arxiv updated 2016/06/08 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
ABSTRACT We present Subaru/Faint Object Camera and Spectrograph and Keck/Deep Imaging Multi-Object Spectrometer medium-resolution spectroscopy of a tidally disrupting Milky Way (MW) globular cluster Palomar 5 (Pal 5) and its tidal stream. The observed fields are located to cover an angular extent of ∼17° along the stream, providing an opportunity to investigate a trend in line-of-sight velocities ( V los ) along the stream, which is essential to constrain its orbit and underlying gravitational potential of the MW’s dark matter halo. A spectral fitting technique is applied to the observed spectra to obtain stellar parameters and metallicities ([Fe/H]) of the target stars. The 19 stars most likely belonging to the central Pal 5 cluster have a mean V los of −58.1 ± 0.7 km s −1 and metallicity [Fe/H] = −1.35 ± 0.06 dex, both of which are in good agreement with those derived in previous high-resolution spectroscopic studies. Assuming that the stream stars have the same [Fe/H] as the progenitor cluster, the derived [Fe/H] and values are used to estimate the possible V los range of the member stars at each location along the stream. Because of the heavy contamination of the field MW stars, the estimated V los range depends on prior assumptions about the stream’s , which highlights the importance of more definitely identifying the member stars using proper motion and chemical abundances to obtain unbiased information of V los in the outer part of the Pal 5 stream. The models for the gravitational potential of the MW’s dark matter halo that are compatible with the estimated V los range are discussed.