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How to make an ultra-faint dwarf spheroidal galaxy: Tidal stirring of disky dwarfs with shallow dark matter density profiles


Łokas, Ewa L; Kazantzidis, Stelios; Mayer, Lucio (2012). How to make an ultra-faint dwarf spheroidal galaxy: Tidal stirring of disky dwarfs with shallow dark matter density profiles. Astrophysical Journal Letters, 751(1):L15.

Abstract

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 109 M sun dark matter (DM) halos. We explore a variety of inner density slopes ρvpropr -α for the dwarf DM halos, ranging from core-like (α = 0.2) to cuspy (α = 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 ~ 1, and with intermediate values for the halo inner density slopes (ρvpropr -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.

Abstract

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 109 M sun dark matter (DM) halos. We explore a variety of inner density slopes ρvpropr -α for the dwarf DM halos, ranging from core-like (α = 0.2) to cuspy (α = 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 ~ 1, and with intermediate values for the halo inner density slopes (ρvpropr -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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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute for Computational Science
Dewey Decimal Classification:530 Physics
Language:English
Date:May 2012
Deposited On:22 Jan 2013 08:15
Last Modified:05 Apr 2016 16:18
Publisher:IOP Publishing
ISSN:2041-8205
Publisher DOI:https://doi.org/10.1088/2041-8205/751/1/L15

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