Day 382

Thursday, JC day.

1303.0674
On the spin bias of satellite galaxies in the local group-like environment
Lee (Jounghun), Lemson

Use Millennium II sim to study the spin bias of dark subhaloes in Local Group-like environments.  Select group-size haloes with total mass comparable to that of LG from FoF halo catalog and locating their subhaloes from the substructure catalog, determine the most massive and second most massive ones among the subhaloes hosted by each selected halo.  When lambda (the dimensionless spin parameter) of each sub halo is derived from its specific angular momentum and circular velocity maximum, a clear signal of strong correlation is detected between the spin parameters of the subhaloes and the main-to-submain mass ratios of their host haloes at z=0.  The higher main-to-submain mass ratio a host halo has, the higher mean spin parameter its subhaloes have.  It is also found that the correlation becomes weaker at higher redshifts, diminishing to negligible level at z=1.  Interpretation of this result is that the strong anisotropic stress in the host halo with high main-to-submain mass ratio should be responsible for the bias of its subhaloes toward the high spin parameters and that the spin bias becomes stronger at lower redshifts when DE plays a role of enhancing the anisotropic stress.  A cosmological implication of the result also discussed.

1303.0816
Studying the emergence of the red sequence through galaxy clustering: host halo masses at z>2
Hartley, .. Conselice, .. et al

Use UKIDSS ultra-deep NIR survey to investigate the clustering of SF and passive galaxies to z~3.5.  New measurements include the first determination of the clustering for passive galaxies at z>2, which is achieved using a cross-correlation technique.  Find that passive galaxies are the most strongly clustered, typically hosted by massive DM haloes with M_halo > 5e12 Msun irrespective of redshift or stellar mass.  Findings consistent with models in which a critical halo mass determines the transition from SF to passive galaxies.  SF galaxies show no strong correlation between stellar mass and halo mass, but passive galaxies show evidence for an anti-correlation; low-mass passive galaxies appear, on average, to be located in the most massive haloes.  These results can be understood if the termination of SF is most efficient for galaxies of low stellar mass in very dense environments.