Short-term optical variability of high-redshift quasi-stellar objects

Short - term optical variability of high - redshift QSO ’ s

This paper presents results of a search for short-term variability in the optical band of selected high-luminosity, high-redshift radio-quiet quasars. Each quasar has been monitored typically for 2 – 4 hours with a time resolution of 2 – 5 minutes and a photometric accuracy of about 0. m 01 – 0. m 02. Due to the significant redshift (z > 2), the covered wavelength range falls into the UV region...

Microlensing of quasi-stellar objects (QSOs)

Very close pairs of quasi-stellar objects

It is pointed out that there are now known four very close pairs of QSOs with separations < 5 arcsec and very different redshifts. Several estimates indicates that the probability that they are accidental configurations are small; a conservative estimate of the probability to have four such pairs by random projection yields 3.5 × 10−3. We conclude either that this is further evidence that QSOs ...

Spectral dating of high-redshift stellar populations

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...

Stellar Masses of High–Redshift Galaxies

We present constraints on the stellar–mass distribution of distant galaxies. These stellar mass estimates derive from fitting population–synthesis models to the galaxies’ observed multi-band spectrophotometry. We discuss the complex uncertainties (both statistical and systematic) that are inherent to this method, and offer future prospects to improve the constraints. Typical uncertainties for g...