Astron. Astrophys. 329, 14-20 (1998)
Biasing and large-scale structure
in a standard CDM N-body simulation
Andrei G. Doroshkevich 1, 3,
Richard Fong 2 and
Olga Makarova 3
1 Theoretical Astrophysics Center, Juliane Maries Vej 30,
DK-2100 Copenhagen O, Denmark
2 Department of Physics, University of Durham, South Road,
Durham DH1 3LE, England
3 Keldysh Institute of Applied Mathemathics, Russian
Academy of Science, Miusskaya Sq. 4, Moscow, 125047, Russia
Received 21 August 1996 / Accepted 25 July 1997
We apply 'core sampling' analysis to a standard CDM N-body
simulation, in which 'galaxies' are identified as high density peaks
in the initial density field. The main concern of this paper is in the
general insight the model provides into the possible
relationship between dark matter (DM) and 'galaxy' large-scale
structures at the present epoch.
The analysis finds the dark matter (DM) distribution to be
dominated by a hierarchical distribution in richness of
sheet-like structures, i.e. of Zel'dovich DM pancakes, over scales of
-100 Mpc. On the other
hand, the 'galaxy' large-scale structure is found to be bimodal, with
the poorer structure dominated by filaments and the richer structure
dominated by sheet-like elements.
The analysis also estimates a mean separation or characteristic
scale for 'galaxy' filaments of
Mpc. With such a modest scale size we identify
them as elements of 'Large-Scale Structure' or LSS. A natural
interpretation of this difference in the 'morphology' of DM LSS from
that of 'galaxy' LSS is that galaxy filaments may be expected to trace
the high density ridges of DM Zel'dovich pancakes. The rich 'galaxy'
sheet-like structures are found to have a mean separation of
-80 Mpc. We call this
'Superlarge-Scale Structure' or SLSS. Also, as large a fraction as
% of the 'galaxies' are in SLSS. These are all
in good agreement with the corresponding observational results.
However, this particular simulation was not found to possess the
stable rich filamentary population seen in the observations.
Nevertheless, the above results show that the form of the 'galaxy'
spatial distribution has, on the whole, many similarities with that of
the observed population, yet that of the DM distribution is distinctly
different. The simulation thus provides an example of the profound
effect biasing could have on the form of the observed large-scale
structure in the Universe.
Key words: cosmology:
large-scale structure of universe: formation and evolution:
N-body simulations: dark
© European Southern Observatory (ESO) 1998
Online publication: November 24, 1997