4.6 Article

HOW TO MAKE AN ULTRA-FAINT DWARF SPHEROIDAL GALAXY: TIDAL STIRRING OF DISKY DWARFS WITH SHALLOW DARK MATTER DENSITY PROFILES

Journal

ASTROPHYSICAL JOURNAL LETTERS
Volume 751, Issue 1, Pages -

Publisher

IOP PUBLISHING LTD
DOI: 10.1088/2041-8205/751/1/L15

Keywords

galaxies: dwarf; galaxies: fundamental parameters; galaxies: kinematics and dynamics; galaxies: structure; Local Group

Funding

  1. Polish National Science Centre [NN203580940]
  2. Center for Cosmology and Astro-Particle Physics at The Ohio State University

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In recent years the Sloan Digital Sky Survey has unraveled a new population of ultra-faint dwarf galaxies (UFDs) whose origin remains a puzzle in the vicinity of the Milky Way (MW). Using a suite of collisionless N-body simulations, we investigate the formation of UFDs in the context of the tidal stirring model for the formation of dwarf spheroidal galaxies in the Local Group (LG). Our simulations are designed to reproduce the tidal interactions between MW-sized host galaxies and rotationally supported dwarfs embedded in 10(9) M-circle dot dark matter (DM) halos. We explore a variety of inner density slopes rho proportional to r (alpha) for the dwarf DM halos, ranging from core-like (alpha = 0.2) to cuspy (alpha = 1), and different dwarf orbital configurations. Our experiments demonstrate that UFDs can be produced via tidal stirring of disky dwarfs on relatively tight orbits, consistent with a redshift of accretion by the host galaxy of z similar to 1, and with intermediate values for the halo inner density slopes (rho proportional to r(-0.6)). The inferred slopes are in excellent agreement with those resulting from both the modeling of the rotation curves of dwarf galaxies and recent cosmological simulations of dwarf galaxy formation. Comparing the properties of observed UFDs with those of their simulated counterparts, we find remarkable similarities in terms of basic observational parameters. We conclude that tidal stirring of rotationally supported dwarfs represents a viable mechanism for the formation of UFDs in the LG environment.

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