Stars beyond galaxies: the origin of extended luminous haloes around galaxies

By M. Abadi, J. Navarro, Matthias Steinmetz. 2005

231 citations recorded by the source corpus.

We use numerical simulations to investigate the origin and structure of the luminous haloes that surround isolated galaxies. These stellar structures extend out to several hundred kpc away from a galaxy, and consist of stars shed by merging subunits during the many accretion events that characterize the hierarchical assembly of galaxies. Such an origin suggests that outer luminous haloes are ubiquitous and that they should appear as an excess of light over extrapolations of the galaxy's inner profile beyond its traditional luminous radius. The mass profile of the accreted stellar component is well approximated by a model where the logarithmic slope steepens monotonically with radius; from p r -3 at the luminous edge of the galaxy to r -4 or steeper near the virial radius of the system. Such spatial distribution is consistent with that of Galactic and M31 globular clusters, suggesting that many of the globulars were brought in by accretion events, in a manner akin to the classic Searle-Zinn scenario. Luminous haloes are similar in shape to their dark matter counterparts, which are only mildly triaxial and much rounder than dark haloes formed in simulations that do not include a dissipative luminous component. The outer stellar spheroid is supported by a velocity dispersion tensor with a substantial and radially increasing radial anisotropy: from σ 2 1 /σ 2 1 ∼ 2 at the edge of the central galaxy to t5 at the virial radius. These properties distinguish the stellar halo from the dark matter component, which is more isotropic in velocity space, as well as from some tracers of the outer spheroid such'as satellite galaxies. Most stars in the outer halo formed in progenitors that have since merged with the central galaxy or have been substantially disrupted in its immediate surroundings; very few stars in the halo are contributed by satellites that survive as self-bound entities at the present. Although the stellar spheroid in the simulations is more prominent than in disc-dominated galaxies, many of these features are in reasonable agreement with recent observations of the outer halo of the Milky Way, of M31, and of other isolated spirals, and suggest that all of these systems underwent an early period of active merging, as envisioned in hierarchical models of galaxy formation.

Subfields: Astronomy and Astrophysics, Electrical and Electronic Engineering, Instrumentation

View Paper: https://www.semanticscholar.org/paper/00bcc77c05b9d1e40974569e6b23b73af6eddce4

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Citations in the corpus

Globular clusters, satellite galaxies and stellar haloes from early dark matter peaks (2005, background): “Journal compilation C© 2006 RAS, MNRAS 368, 563–570 Cosmological hydrodynamical simulations are also beginning to attain the resolution to resolve the formation of the old stellar haloes of galaxies (Abadi et al. 2006).”
Accreted versus in situ Milky Way globular clusters (2010, background): “They will then add to any pre-existing globular cluster population (Searle & Zinn 1978; Abadi et al. 2006).”
The RAVE Survey: Constraining the Local Galactic Escape Speed (2006, methodology): “The issue of the outer parts of the haloes of these simulated galaxies are discussed in Abadi et al. (2006).”
Galactic star formation and accretion histories from matching galaxies to dark matter haloes (2012, background): “In lower-mass disk-like galaxies the accreted stars contribute to the build-up of the outer stellar halo and can also directly contribute on the order of 10 percent to the stel- lar mass of the disk (e.g. Abadi et al. 2006; Font et al. 2011; Tissera et al. 2012).”
THE DUAL ORIGIN OF STELLAR HALOS (2009, methodology): “Abadi et al. (2006), using a set of fully cosmological simulations, find that in situ stars dominate the inner 20 kpc of their galaxies, while accreted stars make up the majority of the outer regions.”
Kinematic properties of early-type galaxy haloes using planetary nebulae (2008, unknown): “The kinematics of the luminous haloes of isolated galaxies are investigated by Abadi et al. (2006).”
Globular Cluster System and Milky Way Properties Revisited (2005, background): “This kind of collapse would produce flatter radial density profiles (Abadi et al. 2006, and references therein).”