We present preliminary results of an on going program to study Lyman Alpha Emitters, Lyman Break Galaxies, and Quasars at high redshift with the OSIRIS...
Large SDSS Quasar Groups and their Statistical Significance
We use a volume-limited sample of quasars in the Sloan Digital Sky Survey (SDSS) DR7 quasar catalog to identify quasar groups and address their statistical...
Large-scale environments of z < 0.4 active galaxies
Context. Properties of galaxies depend on their large-scale environment. As the influence of active galactic nuclei (AGN) in galaxy evolution is becoming more...
Long-term multiwavelength monitoring and reverberation mapping of NGC 2617 during a changing-look event
We present the results of photometric and spectroscopic monitoring campaigns of the changing look AGN NGC 2617 carried out from 2016 until 2022 and covering the...
Long-term optical spectral monitoring of a changing-look active galactic nucleus NGC 3516. II. Broad-line profile variability
Context. We analyze the broad Hβ line profile variability of a "changing look" active galactic nucleus (CL-AGN) NGC 3516 over an extensive period of 25 years...
Low deuterium abundance in the z_abs=3.514 absorber towards APM 08279+5255
{A high-resolution, high signal-to-noise HIRES-Keck spectrum of APM 08279+5255 reveals a feature in the HI Lyalpha profile of the z_abs=3.514 absorber at the...
Low-redshift quasars in the SDSS Stripe 82 - II. Associated companion galaxies and signature of star formation
We present optical spectroscopy of the close companions of 22 low-redshift (z < 0.5) quasars (QSO) selected from a larger sample of QSO in the SDSS Stripe82...
Low-resolution spectroscopy and spectral energy distributions of selected sources towards σ Orionis
Aims: We study in detail nine sources in the direction of the young σ Orionis cluster, which is considered to be a unique site for studying stellar and...