The Dependence of Galaxy Type on Host Halo Mass

We examine the origins of the bimodality observed in the global properties of galaxies by comparing the environmental dependencies of star-formation for giant and dwarf galaxy populations. Using Sloan Digital Sky Survey (SDSS) DR4 spectroscopic data to create a volume-limited sample complete to M*+3, we find that the environmental dependences of giant and dwarf galaxies are quite different, implying fundamental differences in their evolution. Whereas the star-formation histor...

The relationship between galaxies and dark matter can be characterized by the halo mass of the central galaxy and the fraction of galaxies that are satellites. Here we present observational constraints from the SDSS on these quantities as a function of r-band luminosity and stellar mass using galaxy-galaxy weak lensing, with a total of 351,507 lenses. We use stellar masses derived from spectroscopy and virial halo masses derived from weak gravitational lensing to determine th...

It has been shown that galaxy properties depend strongly on their host environment. In order to understand the relevant physical processes driving galaxy evolution it is important to study the observed properties of galaxies in different environments. Mass segregation in bound galaxy structures is an important indicator of evolutionary history and dynamical friction timescales. Using group catalogues derived from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) we inves...

We study the influence of the environment on the evolution of galaxies by investigating the luminosity function (LF) of galaxies of different morphological types and colours at different environmental density levels. We construct the LFs separately for galaxies of different morphology (spiral and elliptical) and of different colours (red and blue) using data from the Sloan Digital Sky Survey (SDSS), correcting the luminosities for the intrinsic absorption. We use the global...

We use a complete sample of galaxies drawn from the SDSS to study how structure, star formation and nuclear activity depend on local density and on stellar mass. Local density is estimated by counting galaxies above a fixed absolute magnitude limit within cylinders 2 Mpc in projected radius and +-500 km/s in depth. The stellar mass distribution of galaxies shifts by nearly a factor of two towards higher masses between low and high density regions. At fixed stellar mass, both ...

Using a large sample of local galaxies (144,940) with -17.5< Mr <-22 and 0.025< z <0.107, selected from SDSS DR5, we compare AGN host galaxies with non-AGN galaxies at matched luminosity, velocity dispersion, color, color gradient, or concentration index, to investigate how AGN activity is related with galaxy properties. The AGN sample is composed of Type II AGNs identified with flux ratios of narrow-emission lines with S/N > 6. We find that the fraction of galaxies hosting a...

From the Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5), we extract a sample of 4594 galaxies at redshifts 0.02<z<0.03, complete down to a stellar mass of M=10^10 Msol. We quantify their structure (Sersic index), morphology (Sersic index + ``Bumpiness''), and local environment. We show that morphology and structure are intrinsically different galaxy properties, and we demonstrate that this is a physically relevant distinction by showing that these properties depend diff...

We study the properties of SDSS galaxies with and without AGN detection as a function of the local and global environment measured via the local density, the mass of the galaxy host group (parameterised by the group luminosity) and distance to massive clusters. Our results can be divided in two main subjects, the environments of galaxies and their relation to the assembly of their host haloes, and the environments of AGN. (i) For the full SDSS sample, we find indications that...

By providing homogeneous photometric and spectroscopic data of high quality for very large and objectively selected samples of galaxies, the Sloan Digital Sky Survey allows statistical studies of the physical properties of galaxies and AGN to be carried out at an unprecedented level of precision and detail. Here we publicly release catalogues of derived physical properties for 211,894 galaxies, including 33,589 narrow-line AGN. These are complete samples with well understood ...

We analyse how the properties of galaxies in groups identified in the Sloan Digital Sky Survey depend on the environment. In particular, we study the relationship between galaxy properties and group mass and group-centric distance. Among the galaxy properties we have considered here, we find that the $g-r$ colour is the most predictive parameter for group mass, while the most predictive pair of properties are $g-r$ colour and $r-$band absolute magnitude. Regarding the positio...