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Title

Mismatch and misalignment: dark haloes and satellites of disc galaxies

Author(s)

Deason, A. J.;  McCarthy, I. G.;  Font, A. S.;  Evans, N. W.;  Frenk, C. S.;  Belokurov, V.;  Libeskind, N. I.;  Crain, R. A.;  Theuns, T.

Abstract

We study the phase-space distribution of satellite galaxies associated with late-type galaxies in the gimic suite of simulations. gimic consists of resimulations of five cosmologically representative regions from the Millennium Simulation, which have higher resolution and incorporate baryonic physics. Whilst the disc of the galaxy is well aligned with the inner regions (r∼ 0.1r200) of the dark matter halo, both in shape and angular momentum, there can be substantial misalignments at larger radii (r∼r200). Misalignments of >45° are seen in ∼30 per cent of our sample. We find that the satellite population aligns with the shape (and angular momentum) of the outer dark matter halo. However, the alignment with the galaxy is weak owing to the mismatch between the disc and dark matter halo. Roughly 20 per cent of the satellite systems with 10 bright galaxies within r200 exhibit a polar spatial alignment with respect to the galaxy – an orientation reminiscent of the classical satellites of the Milky Way. We find that a small fraction (& 8764;10 per cent) of satellite systems show evidence for rotational support which we attribute to group infall. There is a bias towards satellites on prograde orbits relative to the spin of the dark matter halo (and to a lesser extent with the angular momentum of the disc). This preference towards co-rotation is stronger in the inner regions of the halo where the most massive satellites accreted at relatively early times are located. We attribute the anisotropic spatial distribution and angular momentum bias of the satellites at z= 0 to their directional accretion along the major axes of the dark matter halo. The satellite galaxies have been accreted relatively recently compared to the dark matter mass and have experienced less phase-mixing and relaxation – the memory of their accretion history can remain intact to z= 0. Understanding the phase-space distribution of the z= 0 satellite population is key for studies that estimate the host halo mass from the line-of-sight velocities and projected positions of satellite galaxies. We quantify the effects of such systematics in estimates of the host halo mass from the satellite population.

Publication type

Journal article

Research centre

Swinburne University of Technology. Faculty of Information and Communication Technologies. Centre for Astrophysics and Supercomputing

Source

Monthly Notices of the Royal Astronomical Society, Vol. 415, no. 3 (Aug 2011), pp. 2607-2625

Publication year

2011

FOR Code(s)

0201 Astronomical and Space Sciences

Keyword(s)

Cosmological simulations;  Cosmology theory;  Dark matter;  Disc galaxies;  Dynamics;  Galaxies;  Haloes;  Kinematics;  Satellites

Publisher

Wiley-Blackwell Publishing

ISSN

0035-8711

Publisher URL

http://dx.doi.org/10.1111/j.1365-2966.2011.18884.x

Copyright

Copyright © 2011 The Authors. Journal compilation copyright © 2011 Royal Astronomical Society. The accepted manuscript is reproduced in accordance with the copyright policy of the publisher. The definitive publication is available at www.interscience.wiley.com.

Additional information

The authors acknowledge support from the Technology Facilities Council (STFC), the Royal Society, a Kavli Institute Fellowship at the University of Cambridge, a Royal Society Wolfson Research Merit award and the Australian Research Council via a Discovery Project grant.

Full text

Peer reviewed