How Stochastic is the Bias between Galaxy Types?

Mike Blanton (Fermilab)

2.30 pm Monday February 21 in Curia II.

The relative clustering of galaxies of different types contains information on the nature of galaxy formation. For example, hydrodynamic models of galaxy formation predict a large scatter in the relationship between the density fields of early- and late-type galaxies, corresponding to a correlation coefficient r=0.5--0.8 (where unity corresponds to no scatter). Meanwhile, semi-analytic models predict correlation coefficients closer to r=0.9. I develop a maximum likelihood method of analyzinbg the joint counts-in-cells of early and late-type galaxies, and apply it to the Las Campanas Redshift Survey (LCRS), finding r=0.87. In addition, I detect errors in the selection function of LCRS galaxies, implying that the true value is closer to r=0.95. I discuss the consequences of this result for theories of galaxy formation.