1705.03888
Beyond assembly bias: exploring secondary halo biases for cluster-size halos
Mao, Zentner, Wechsler
Secondary halo bias, commonly known as "assembly bias," is the dependence of halo clustering on halo property other than mass. This prediction of the LCDM cosmology is essential to modeling the galaxy distribution to high precision and interpreting clustering measurements. As the name suggests, different manifestations of secondary halo bias have been thought to originate from halo assembly histories. Show conclusively that this is incorrect for cluster-size halos. Present an up-to-date summary of secondary halo biases of high-mass haloes due to various halo properties including concentration, spin, several proxies of assembly history, and sub halo properties. While concentration, spin and the abundance and radial distribution of sub haloes exhibit significant secondary biases, properties that directly quantify halo assembly history do not. In fact, the entire assembly histories of haloes in pairs are nearly identical to those of isolated haloes. In general, a global correlation between two halo properties does not predict whether or not these two properties exhibit similar secondary biases. For example, assembly history and concentration (or sub halo abundance) are correlated for both paired and isolated haloes, but follow slightly different conditional distribution in these two cases. This results in a secondary halo bias due to concentration (or sub halo abundance), despite the lack of assembly bias in the strict sense for cluster-size haloes. Due to this complexity, caution must be exercised in using any one halo property as a proxy to study the secondary bias due to another property.
1705.04074
Galaxy and Mass Assembly (GAMA): The galaxy stellar mass function to $z=0.1$ from the r-band selected equatorial regions
Wright, Robotham, Driver, et al
Derive the low redshift galaxy stellar mass function (GSMF), inclusive of dust corrections, for the equatorial GAMA dataset covering 180 deg^2. Construct the mass function using a density-corrects maximum volume method, using masses corrected for the impact of optically thick and thin dust. Explore the galactic bivariate brightness plane (M*-mu), demonstrating that surface brightness effects do not systematically bias the mass function measurement above 1e7.5 Msun. The galaxy distribution in the M-mu-plane appears well bounded, indicating that no substantial population of massive but diffuse or highly compact galaxies are systematically missed due to the GAMA selection criteria. The GSMF is {fit with} a double Schechter function, with M*=1e10.78 Msun, phi1*=2.93e-3 h^3/Mpc^3, alpha1=-0.62, phi2*=0.63e-3 h^3/Mpc^3, and alpha2=-1.50. Find the equivalent faint end slope as previously estimated using the GAMA-I sample, although find a higher value of M*. Using the full GAMA-II sample, able to fit the mass function to masses as low as 1e7.5Msun, and assess limits to 1e6.5 Msun. Combining GAMA-II with data from G10-COSMOS, able to comment qualitatively on the shape of the GSMF down to masses as low as 1e6 Msun. Beyond the well known upturn seen in the GSMF at 1e9.5 the distribution appears to maintain a single power-law slope from 1e9 to 1e6.5. Calculate the stellar mass density parameter given the best-estimate GSMF, finding Omega*=1.66e-3/h, inclusive of random and systematic uncertainties. [h == h_70, errorbars omitted]
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