Issue |
A&A
Volume 441, Number 1, October I 2005
|
|
---|---|---|
Page(s) | 55 - 67 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20042473 | |
Published online | 13 September 2005 |
New multi-zoom method for N-body simulations: application to galaxy growth by accretion
Observatoire de Paris, LERMA, 61 Av. de l'Observatoire, 75014 Paris, France e-mail: benoit.semelin@obspm.fr
Received:
2
December
2004
Accepted:
3
June
2005
The growth of galaxies is driven by two processes: mergers with
other galaxies and smooth accretion of intergalactic gas. The relative share
of this two processes depends on the environment (rich cluster or field),
and determines the morphological evolution of the galaxy. In this work we focus
on the properties of accretion onto galaxies. Through numerical simulations we
investigate the geometrical properties of accretion. To span the scale range
required in these simulations we have developed a new numerical technique:
the multi-zoom method. We run a series of Tree-SPH simulations in smaller
and smaller boxes at higher and higher mass resolution, using data recorded
at the previous level to account for the matter inflow and the tidal field from
outside matter. The code is parallelized using OpenMP. We present a validation test
to evaluate the robustness of the method: the pancake collapse.
We apply this new multizoom method to study the accretion properties.
Zooming in onto galaxies from a cosmological simulation, we select a sample of 10 well resolved galaxies (5000 baryonic particles or more). We sum up their basic
properties and plot a Tully-Fisher relation. We find that smooth accretion
of intergalactic cold gas dominates mergers for the mass growth of galaxies at . Next we study the baryonic
accretion rate which shows different behaviours depending on the galaxy mass. The
bias is also computed at different radii and epochs. Then we present
galactocentric angular maps for the accretion integrated
between
and
, which reveal that accretion is highly anisotropic.
Average accretion rates plotted against galactocentric latitude show a variety
of behaviours. In general, accretion in the galactic plane is favored,
even more for baryonic matter than for dark matter. Our results form a basis for
prescribing realistic
accretion in simulations of isolated galaxies.
Key words: galaxies: formation / galaxies: evolution / galaxies: intergalactic medium / galaxies: spiral / cosmology: large-scale structure of Universe
© ESO, 2005
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