The amount of mass contained in low-mass objects is investigated anew. Instead of using a mass–luminosity relation to convert a luminosity function to a mass function, I predict the mass-luminosity relation from assumed mass functions and the luminosity functions of Jahreiss &Wielen (1997) and Gould, Bahcall & Flynn (1997). Comparison of the resulting mass–luminosity relations with data for bin...

We present improved visual and near-infrared empirical mass-luminosity relations for very low mass stars (M<0.6 M). These relations make use of all stellar masses in this range known with better than 10% accuracy, most of which are new determinations with 0.2 to 5% accuracy from our own programme, presented in a companion paper. As predicted by stellar structure models, the metallicity dispersi...

Using the empirical relations between the central galaxy luminosity and the halo mass, and between the total luminosity of galaxies in a halo and the halo mass, we construct the galaxy luminosity function (LF). To the luminosity of the central galaxy in a halo of a given mass we assign log-normal scatter with the mean and the dispersion of the luminosity directly calibrated against the observat...

SCORCH (Simulations and Constructions of the Reionization of Cosmic Hydrogen) is a new project to study the Epoch of Reionization (EoR). In this first paper, we probe the connection between observed high-redshift galaxies and simulated dark matter halos to better understand the primary source of ionizing radiation. High-resolution N-body simulations are run to quantify the abundance of dark mat...

We study a sample of about 1400 disk M dwarfs that are found in 148 fields observed with the Wide Field Camera 2 (WFC2) on the Hubble Space Telescope and 162 fields observed with pre-repair Planetary Camera 1 (PC1), of which 95 of the WFC2 fields are newly analyzed. The method of maximum likelihood is applied to derive the luminosity function and the Galactic disk parameters. At first, we use a...

We examine the X-ray luminosity scaling relations of 31 nearby galaxy clusters from the Representative XMM-Newton Cluster Structure Survey (REXCESS). The objects are selected only in X-ray luminosity, optimally sampling the cluster luminosity function. Temperatures range from 2 to 9 keV, and there is no bias toward any particular morphological type. To reduce measurement scatter we extract pert...

Recently, a very large clustering length has been measured for quasars at a redshift of z ∼ 4. In combination with the observed quasar luminosity function we assess the implications of this clustering for the relationship between quasar luminosity and dark matter halo mass. Our analysis allows for non-linearity and finite scatter in the relation between quasar luminosity and halo mass, as well ...