A marked correlation function analysis of halo formation times in the Millennium Simulation

We study the environmental dependence of the formation epoch of dark matter haloes in the Millennium Simulation: a ten billion particle N-body simulation of standard Lambda cold dark matter cosmology. A sensitive test of this dependence – the marked correlation function – reveals highly significant evidence that haloes of a given mass form earlier in denser regions. We define a marked cross-correlation function, which helps quantify how this effect depends upon the choice of the halo population used to define the environment. The mean halo formation redshift as a function of the local overdensity in dark matter is also well determined, and we see an especially clear dependence for galaxy-sized haloes. This contradicts one of the basic predictions of the excursion set model of structure formation, even though we see that this theory predicts other features of the distribution of halo formation epochs rather well. It also invalidates an assumption usually employed in the popular halo, or halo occupation distribution, models of galaxy clustering, namely that the distribution of halo properties is a function of halo mass but not of halo environment.

[1]  G. Kauffmann,et al.  The many lives of active galactic nuclei: cooling flows, black holes and the luminosities and colour , 2005, astro-ph/0508046.

[2]  R. Sheth.  The halo‐model description of marked statistics , 2005, astro-ph/0511772.

[3]  S. White,et al.  The age dependence of halo clustering , 2005, astro-ph/0506510.

[4]  J. Peacock,et al.  Simulations of the formation, evolution and clustering of galaxies and quasars , 2005, Nature.

[5]  V. Springel.  The Cosmological simulation code GADGET-2 , 2005, astro-ph/0505010.

[6]  C. Baugh,et al.  Where are the stars , 2004, astro-ph/0412049.

[7]  J. Frieman,et al.  Cosmology and the Halo Occupation Distribution from Small-Scale Galaxy Clustering in the Sloan Digital Sky Survey , 2004, astro-ph/0408003.

[8]  Padova,et al.  On the environmental dependence of halo formation , 2004, astro-ph/0402237.

[9]  R. Nichol,et al.  Galaxy ecology: groups and low-density environments in the SDSS and 2dFGRS , 2003, astro-ph/0311379.

[10]  Rien van de Weygaert,et al.  A hierarchy of voids: much ado about nothing , 2003, astro-ph/0311260.

[11]  H. Mo,et al.  The dependence of the galaxy luminosity function on large-scale environment , 2003, astro-ph/0310147.

[12]  Stefan Gottloeber,et al.  The structure of voids , 2003, astro-ph/0305393.

[13]  C. Baugh,et al.  The Halo Occupation Distribution and the Physics of Galaxy Formation , 2002, astro-ph/0212357.

[14]  Christopher J. Miller,et al.  Galaxy Star Formation as a Function of Environment in the Early Data Release of the Sloan Digital Sky Survey , 2002, astro-ph/0210193.

[15]  C. Baugh,et al.  Galaxy formation using halo merger histories taken from N‐body simulations , 2002, astro-ph/0210141.

[16]  M. Kerscher,et al.  Correlations in the orientations of galaxy clusters , 2002, astro-ph/0209029.

[17]  R. Sheth,et al.  Halo Models of Large Scale Structure , 2002, astro-ph/0206508.

[18]  Nmsu,et al.  Spatial distribution of galactic halos and their merger histories , 2002, astro-ph/0203148.

[19]  C. Baugh,et al.  A comparison of gas dynamics in smooth particle hydrodynamics and semi-analytic models of galaxy formation , 2002, astro-ph/0202485.

[20]  D. Weinberg,et al.  The Halo Occupation Distribution: Toward an Empirical Determination of the Relation between Galaxies and Mass , 2001, astro-ph/0109001.

[21]  V. Springel,et al.  GADGET: a code for collisionless and gasdynamical cosmological simulations , 2000, astro-ph/0003162.

[22]  H. Mo,et al.  Ellipsoidal collapse and an improved model for the number and spatial distribution of dark matter haloes , 1999, astro-ph/9907024.

[23]  Padova,et al.  Populating a cluster of galaxies - I. Results at z=0 , 2000, astro-ph/0012055.

[24]  C. Baugh,et al.  Hierarchical galaxy formation , 2000, astro-ph/0007281.

[25]  M. Kerscher,et al.  Luminosity- and Morphology-dependent Clustering of Galaxies , 2000, astro-ph/0003358.

[26]  U. Seljak.  Analytic model for galaxy and dark matter clustering , 2000, astro-ph/0001493.

[27]  S. White,et al.  The structure and clustering of Lyman-break galaxies , 1998, astro-ph/9807341.

[28]  G. Kauffmann,et al.  Clustering of galaxies in a hierarchical universe - I. Methods and results at z=0 , 1998, astro-ph/9805283.

[29]  U. California,et al.  Semi-analytic modelling of galaxy formation: The local Universe , 1998, astro-ph/9802268.

[30]  G. Kauffmann,et al.  Environmental influences on dark matter haloes and consequences for the galaxies within them , 1997, astro-ph/9710125.

[31]  H. M. P. Couchman,et al.  Evolution of Structure in Cold Dark Matter Universes , 1997, astro-ph/9709010.

[32]  U. Seljak,et al.  A Line of sight integration approach to cosmic microwave background anisotropies , 1996, astro-ph/9603033.

[33]  C. Frenk,et al.  A recipe for galaxy formation , 1994, astro-ph/9402001.

[34]  G. Kauffmann,et al.  The formation and evolution of galaxies within merging dark matter haloes , 1993 .

[35]  S. Cole,et al.  Merger rates in hierarchical models of galaxy formation – II. Comparison with N-body simulations , 1994, astro-ph/9402069.

[36]  J. R. Bond,et al.  Excursion set mass functions for hierarchical Gaussian fluctuations , 1991 .

[37]  R. Bower.  The evolution of groups of galaxies in the Press-Schechter formalism , 1991 .

[38]  S. Cole,et al.  Biased clustering in the cold dark matter cosmogony , 1989 .

[39]  G. Efstathiou,et al.  The formation of dark halos in a universe dominated by cold dark matter , 1988 .

[40]  A. Szalay,et al.  The statistics of peaks of Gaussian random fields , 1986 .

[41]  G. Efstathiou,et al.  The evolution of large-scale structure in a universe dominated by cold dark matter , 1985 .

[42]  M. Postman,et al.  The morphology-density relation - The group connection , 1984 .

[43]  A. Dressler.  Galaxy morphology in rich clusters: Implications for the formation and evolution of galaxies , 1980 .

[44]  M. Rees,et al.  Core condensation in heavy halos: a two-stage theory for galaxy formation and clustering , 1978 .