Stars on the edge: Galactic tides and the outskirts of the Sculptor dwarf spheroidal

Abstract

The formation of "stellar halos" in dwarf galaxies have been discussed in terms of early mergers or Galactic tides, although fluctuations in the gravitational potential due to stellar feedback is also a possible candidate mechanism. A Bayesian algorithm is used to find new candidate members in the extreme outskirts of the Sculptor dwarf galaxy. Precise metallicities and radial velocities for two distant stars are measured from their spectra taken with the Gemini South GMOS spectrograph. The radial velocity, proper motion and metallicity of these targets are consistent with Sculptor membership. As a result, the known boundary of the Sculptor dwarf extends now out to an elliptical distance of $\sim 10$ half-light radii, which corresponds to a projected physical distance of $\sim 3$ kpc. As reported in earlier work, the overall distribution of radial velocities and metallicities indicate the presence of a more spatially and kinematically dispersed metal-poor population that surrounds the more concentrated and colder metal-rich stars. Sculptor's density profile shows a "kink" in its logarithmic slope at a projected distance of $\sim 25$ arcmin (620 pc), which we interpret as evidence that Galactic tides have helped to populate the distant outskirts of the dwarf. We discuss further ways to test and validate this tidal interpretation for the origin of these distant stars.

Accepted for publication on MNRAS. Figure 1 now displays all the candidate members. arXiv admin note: text overlap with arXiv:2301.13214

References in corpus (19)

• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• A new implementation of the infrared flux method using the 2MASS catalogue
• The Tidal Evolution of Local Group Dwarf Spheroidals
• The kinematic status and mass content of the Sculptor dwarf spheroidal galaxy
• The NIR Ca II triplet at low metallicity - Searching for extremely low-metallicity stars in classical dwarf galaxies
• The growth of dark matter halos: evidence for significant smooth accretion
• Satellite Dwarf Galaxies in a Hierarchical Universe: The Prevalence of Dwarf-Dwarf Major Mergers
• Exploiting the Gaia EDR3 photometry to derive stellar temperatures
• Revised and new proper motions for confirmed and candidate Milky Way dwarf galaxies
• linemake: An Atomic and Molecular Line List Generator
• An extended halo around an ancient dwarf galaxy
• Kinematics of the local disk from the RAVE survey and the Gaia first data release
• Chemical Signatures of the First Supernovae in the Sculptor Dwarf Spheroidal Galaxy
• Zero-metallicity hypernova uncovered by an ultra metal-poor star in the Sculptor dwarf spheroidal galaxy
• Cosmological implications of dwarf spheroidal chemical evolution
• Solo dwarfs II: The stellar structure of isolated Local Group dwarf galaxies
• Machine learning detects multiplicity of the first stars in stellar archaeology data
• An extended stellar halo discovered in the Fornax dwarf spheroidal using Gaia EDR3
• The Pristine survey XIV: chemical analysis of two ultra-metal-poor stars

Cited by in corpus (1)

• The Pristine Inner Galaxy Survey (PIGS) IX. The largest detailed chemical analysis of very metal-poor stars in the Sagittarius dwarf galaxy