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Title: A ROBUST MEASURE OF DARK MATTER HALO ELLIPTICITIES

Abstract

In simulations of the standard cosmological model (ΛCDM), dark matter halos are aspherical. However, so far the asphericity of an individual galaxy’s halo has never been robustly established. We use the Jeans equations to define a quantity that robustly characterizes a deviation from rotational symmetry. This quantity is essentially the gravitational torque and it roughly provides the ellipticity projected along the line of sight. We show that the Thirty Meter Telescope (TMT), with a single epoch of observations combined with those of the Gaia Space Telescope , can distinguish the ΛCDM value of the torque from zero for each Sculptor-like dwarf galaxy with a confidence between 0 and 5 σ , depending on the orientation of each halo. With two epochs of observations, TMT will achieve a 5 σ discovery of torque and thus asphericity for most such galaxies, thus providing a new and powerful test of the ΛCDM model.

Authors:
 [1]
  1. Institute of Modern Physics, CAS, NanChangLu 509, Lanzhou 730000 (China)
Publication Date:
OSTI Identifier:
22654266
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 826; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COSMOLOGICAL MODELS; EQUATIONS; GALAXIES; NONLUMINOUS MATTER; ORIENTATION; SIMULATION; SPACE; SYMMETRY; TELESCOPES; TORQUE

Citation Formats

Evslin, Jarah. A ROBUST MEASURE OF DARK MATTER HALO ELLIPTICITIES. United States: N. p., 2016. Web. doi:10.3847/2041-8205/826/2/L23.
Evslin, Jarah. A ROBUST MEASURE OF DARK MATTER HALO ELLIPTICITIES. United States. doi:10.3847/2041-8205/826/2/L23.
Evslin, Jarah. 2016. "A ROBUST MEASURE OF DARK MATTER HALO ELLIPTICITIES". United States. doi:10.3847/2041-8205/826/2/L23.
@article{osti_22654266,
title = {A ROBUST MEASURE OF DARK MATTER HALO ELLIPTICITIES},
author = {Evslin, Jarah},
abstractNote = {In simulations of the standard cosmological model (ΛCDM), dark matter halos are aspherical. However, so far the asphericity of an individual galaxy’s halo has never been robustly established. We use the Jeans equations to define a quantity that robustly characterizes a deviation from rotational symmetry. This quantity is essentially the gravitational torque and it roughly provides the ellipticity projected along the line of sight. We show that the Thirty Meter Telescope (TMT), with a single epoch of observations combined with those of the Gaia Space Telescope , can distinguish the ΛCDM value of the torque from zero for each Sculptor-like dwarf galaxy with a confidence between 0 and 5 σ , depending on the orientation of each halo. With two epochs of observations, TMT will achieve a 5 σ discovery of torque and thus asphericity for most such galaxies, thus providing a new and powerful test of the ΛCDM model.},
doi = {10.3847/2041-8205/826/2/L23},
journal = {Astrophysical Journal Letters},
number = 2,
volume = 826,
place = {United States},
year = 2016,
month = 8
}
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