Update on the Cetus Polar Stream and its Progenitor

Abstract

We trace the Cetus Polar Stream (CPS) with blue horizontal branch (BHB) and red giant stars (RGBs) from Data Release 8 of the Sloan Digital Sky Survey (SDSS DR8). Using a larger dataset than was available previously, we are able to refine the measured distance and velocity to this tidal debris star stream in the south Galactic cap. Assuming the tidal debris traces the progenitor's orbit, we fit an orbit to the CPS and find that the stream is confined between ~24-36 kpc on a rather polar orbit inclined 87 degrees to the Galactic plane. The eccentricity of the orbit is 0.20, and the period ~700 Myr. If we instead matched N-body simulations to the observed tidal debris, these orbital parameters would change by 10% or less. The CPS stars travel in the opposite direction to those from the Sagittarius tidal stream in the same region of the sky. Through N-body models of satellites on the best-fitting orbit, and assuming that mass follows light, we show that the stream width, line-of-sight depth, and velocity dispersion imply a progenitor of at least 10^8 solar masses. However, the density of stars along the stream requires either a disruption time on the order of one orbit, or a stellar population that is more centrally concentrated than the dark matter. We suggest that an ultra-faint dwarf galaxy progenitor could reproduce a large stream width and velocity dispersion without requiring a very recent deflection of the progenitor into its current orbit. We find that most Cetus stars have metallicities of -2.5 < [Fe/H] < -2.0, similar to the observed metallicities of the ultra-faint dwarfs. Our simulations suggest that the parameters of the dwarf galaxy progenitors, including their dark matter content, could be constrained by observations of their tidal tails through comparison of the debris with N-body simulations.

36 pages, 18 figure, 3 tables (preprint format); Figure 18 at reduced resolution -- full-resolution version at http://rpi.edu/~newbeh/yam_etal_CetusPolarStream_arXiv.pdf; accepted to Astrophysical Journal

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• Detection of a 60 Degree-Long Dwarf Galaxy Debris Stream
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• The case for OH suppression at near-infrared wavelengths
• An Orbit Fit for the Grillmair Dionatos Cold Stellar Stream
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Cited by in corpus (18)

• The Global Dynamical Atlas of the Milky Way mergers: Constraints from Gaia EDR3 based orbits of globular clusters, stellar streams and satellite galaxies
• Stellar Streams and Clouds in the Galactic Halo
• galstreams: A Library of Milky Way Stellar Stream Footprints and Tracks
• $S^5$: The Orbital and Chemical Properties of One Dozen Stellar Streams
• Evidence of a dwarf galaxy stream populating the inner Milky Way Halo
• The age structure of the Milky Way's halo
• The Milky Way's stellar streams and globular clusters do not align in a Vast Polar Structure
• Revealing the Complicated Story of the Cetus Stream with StarGO
• Is NGC 5824 the Core of the Progenitor of the Cetus Stream?
• Stellar chemo-kinematics of the Cetus dwarf spheroidal galaxy
• The Cetus-Palca stream: A disrupted small dwarf galaxy. A prequel to the science possible with WEAVE with precise spectro-photometric distances
• The southern leading and trailing wraps of the Sagittarius tidal stream around the globular cluster Whiting1
• On The Nature of ultra-faint Dwarf Galaxy Candidates II: The case of Cetus II
• LMC-driven anisotropic boosts in stream--subhalo interactions
• Candidate members of the Pal 5, GD-1, Cetus Polar, and Orphan tidal stellar halo streams from Sdss DR9, Lamost DR3 and APOGEE catalogues
• An Orbit Fit to Likely Hermus Stream Stars
• A fork in the Sagittarius trailing debris
• Segue 2 Recently Collided with the Cetus-Palca Stream: New Opportunities to Constrain Dark Matter in an Ultra-Faint Dwarf