The Ellipticity and Orientation of Clusters of Galaxies from N-Body Experiments

Randall J. Splinter; Adrian L. Melott; Angela Linn; Charles Buck; Jeremy Tinker

doi:10.1086/303896

paper

The Ellipticity and Orientation of Clusters of Galaxies from N-Body Experiments

arXiv:astro-ph/9607144 · doi:10.1086/303896

Abstract

In this study we use simulations of 128 $^{3}$ particles to study the ellipticity and orientation of clusters of galaxies in N-body simulations of differing power-law initial spectra (P(k) \propto k^n ,n = +1, 0, -1, -2 $), an dd e n s i t y p a r am e t er s ($ Î©_0 = 0.2 $t o 1.0) . F u r t h er m or e, u n l ik e m os tt h eor e t i c a l s t u d i es w e mimi c m os t o b ser v er s b y r e m o v in g a l l p a r t i c l es w hi c h l i e a t d i s t an ces g r e a t er t han 21/ h M p c f r o m t h ec l u s t er ce n t er o f ma ss . W eco m p u t e d t h e a x ia l r a t i o an d t h e p r in c i p a l a x es u s in g t h e in er t ia t e n sor o f e a c h c l u s t er . T h e m e an e l l i pt i c i t y o f c l u s t er s in cr e a sess t r o n g l y w i t hin cr e a s in g$ n $. W e a l so f in d t ha t c l u s t er s t e n d t o b eco m e m or es p h er i c a l a t s ma l l er r a d ii . W eco m p a r e d t h eor i e n t a t i o n o f a c l u s t er t o t h eor i e n t a t i o n o f n e i g hb or in g c l u s t er s a s a f u n c t i o n o f d i s t an ce (cor r e l a t i o n) . I na dd i t i o n, w eco n s i d er e d w h e t h er a c l u s t e r^{'} s maj or a x i s t e n d s t o l i e a l o n g t h e l in eco nn ec t in g i tt o an e i g hb or in g c l u s t er, a s a f u n c t i o n o f d i s t an ce (a l i g nm e n t) . B o t ha l i g nm e n t s an d cor r e l a t i o n s w er eco m p u t e d in t h r ee d im e n s i o n s an d in p r o j ec t i o n t o mimi co b ser v a t i o na l s u r v ey s . O u r r es u l t ss h o w t ha t s i g ni f i c an t a l i g nm e n t se x i s t f or a l l s p ec t r aa t s ma l l se p a r a t i o n s ($ D < 15 h^{-1} $M p c) b u t d r o p so f f a tl a r g er d i s t an ce ina s t r o n g l y$ n-$dependent way.

22 pages, requires aaspp4.sty, flushrt.sty, and epsf.sty Revised manuscript, accepted for publication in ApJ