Aims. We estimate stellar masses of galaxies in the high redshift universe with the intention of determining the influence of newly available Spitzer/IRAC infrared data on the analysis. Based on the results we probe the mass assembly history of the universe. Methods. We use the GOODS–MUSIC catalog which provides multiband photometry from the U–filter to the 8 μm Spitzer band for almost 15.000 g...

Age derivation techniques for unresolved stellar populations at high redshifts are explored using the NUV spectrum of LBDS 53W091 (z = 1.55) and LBDS 53W069 (z = 1.43). The photometry and morphology of these galaxies – which are weak radio sources – suggest they are early-type systems, a feature that makes them ideal test beds for the analysis of their ages and metallicities with the use of pop...

We present surface photometry and stellar kinematics of NGC 2950, which is a nearby and undisturbed SB0 galaxy hosting two nested stellar bars. We use the Tremaine-Weinberg method to measure the pattern speed of the primary bar. This also permits us to establish directly and for the first time that the two nested bars are rotating with different pattern speeds, and in particular that the rotati...

We have conducted an optical long-term monitoring survey of the majority of dwarf galaxies in the Local Group, with the Isaac Newton Telescope (INT), to identify the long period variable (LPV) stars. LPV stars vary on timescales of months to years, and reach the largest amplitudes of their brightness variations at optical wavelengths, due to the changing temperature. They trace stellar populati...

Aims. Using the CoRoT space based photometry of the O-type binary HD 46149, stellar atmospheric effects related to rotation can be separated from pulsations, because they leave distinct signatures in the light curve. This offers the possibility of characterising and exploiting any pulsations seismologically. Methods. Combining high-quality space based photometry, multi-wavelength photometry, sp...

We have constrained the age of the globular cluster S312 in the Andromeda galaxy (M31) by comparing its multicolor photometry with theoretical stellar population synthesis models. This is both a check on the age of this globular cluster, as well a check on our methodology. Main-sequence photometry has been the most direct method for determining the age of a star cluster. S312 was observed as pa...

Saturated stellar images on digitised photographic plates are many times greater in area than the ‘seeing disk’ seen in unsaturated CCD images. Indeed the flux profile of a bright star can be traced out for several degrees from the star’s centre. The radius of the saturated stellar image can often be directly related to the magnitude of the star, a fact well known and exploited in iris photomet...