Feeling the pull, a study of natural Galactic accelerometers. II: kinematics and mass of the delicate stellar stream of the Palomar 5 globular cluster

Abstract

We present two spectroscopic surveys of the tidal stellar stream of the Palomar 5 globular cluster, undertaken with the VLT/FLAMES and AAT/AAOmega instruments. We use these data in conjunction with photometric data presented in the previous contribution in this series to classify the survey stars in terms of their probability of belonging to the Palomar 5 stellar stream. We find that high-probability candidates are only found in a very narrow spatial interval surrounding the locus of the stream on the sky. PanSTARRS RRLyrae stars in this region of sky are also distributed in a similar manner. The absence of significant "fanning" of this stellar stream confirms that Palomar 5 does not follow a chaotic orbit. Previous studies have found that Palomar 5 is largely devoid of low-mass stars, and we show that this is true also of the stellar populations along the trailing arm out to $6°$. Within this region, which contains 73\% of the detected stars, the population is statistically identical to the core, implying that the ejection of the low-mass stars occurred before the formation of the stream. We also present an updated structural model fit to the bound remnant, which yields a total mass of $4297\pm 98{\mathrm{M}}_{\odot }$ and a tidal radius $0.145\pm 0.009$ kpc. We estimate the mass of the observed system including the stream to be $12200\pm 400{\mathrm{M}}_{\odot }$, and the initial mass to have been $\sim 47000\pm 1500{\mathrm{M}}_{\odot }$. These observational constraints will be employed in our next study to model the dynamics of the system in detail.

13 pages, 13 figures, ApJ in print

References in corpus (5)

• The Dartmouth Stellar Evolution Database
• Globular Cluster Streams as Galactic High-Precision Scales - The Poster Child Palomar 5
• A Synoptic Map of Halo Substructures from the Pan-STARRS1 3π Survey
• Gaps in globular cluster streams: giant molecular clouds can cause them too
• Palomar 5 and its Tidal Tails: A Search for New Members in the Tidal Stream

Cited by in corpus (12)

• Variations in the width, density, and direction of the Palomar 5 tidal tails
• Stellar streams as gravitational experiments II. Asymmetric tails of globular cluster streams
• Kinematics of the Palomar 5 stellar stream from RR Lyrae stars
• The e-TidalGCs Project: Modeling the extra-tidal features generated by Galactic globular clusters
• APOGEE Detection of N-rich stars in the tidal tails of Palomar 5
• Forward and Back: Kinematics of the Palomar 5 Tidal Tails
• New Determination of Fundamental Properties of Palomar 5 Using Deep DESI Imaging Data
• Asymmetry of the tidal tails of open star clusters in direct N-body integrations in Milgrom-law dynamics
• A Search for Extra-Tidal RR Lyrae in the Globular Cluster NGC 5024 and NGC 5053
• Multi-wavelength observations of the Galactic X-ray binaries IGR J20155+3827 and Swift J1713.4-4219
• Mock Observations of Multiple Stellar Populations in Tidal Streams of Palomar 5 for the Chinese Space Station Survey Telescope
• Evidence for the First Globular Cluster Stellar Stream beyond the Milky Way