Related papers: Ab-initio computation of Karlsson's constant
We study the observational signatures of a potential population of low-luminosity quasars at high redshifts in a LambdaCDM cosmology. We derive the evolution of the quasar luminosity function at fainter luminosities and higher redshifts…
We study the prospects of finding the first quasars in the universe with ALMA and JWST. For this purpose, we derive a model for the high-redshift black hole population based on observed relations between the black hole mass and the host…
Studies of the formation and early history of galaxies have been hampered by the difficulties inherent in detecting faint galaxy populations at high redshift. As a consequence, observations at the highest redshifts (3.5 < z < 5) have been…
We review observable signatures of the first generation of stars and low-luminosity quasars, including the metal enrichment, radiation background, and dust opacity/emission that they produce. We compute the formation history of collapsed…
We have imaged 45 quasars from the Sloan Digital Sky Survey (SDSS) with redshifts 1.85 < z < 4.26 in JHKs with the KPNO SQIID imager. By combining these data with optical magnitudes from the SDSS we have computed the restframe optical…
Most of the successful physical theories rely on the constancy of few fundamental quantities (such as the speed of light, $c$, the fine-structure constant, \alpha, the proton to electron mass ratio, \mu, etc), and constraining the possible…
Recent measurements of the temperature of the sky in the radio band, combined with literature data, have convincingly shown the existence of a cosmic radio background with an amplitude of $\sim 1$ K at 1 GHz and a spectral energy…
We revisit the spectra observed by Ramos Almeida et al. (2013) from an homogeneous sample of galaxies at 0.27<z<1.28 with the aim of finding out the characteristics of the single objects by consistent modelling. In particular we investigate…
We present observations of 11 quasars, selected in the range z = 2.2-4.1, obtained with ESA's Superconducting Tunnel Junction (STJ) camera on the WHT. Using a single template quasar spectrum, we show that we can determine the redshifts of…
Stellar emission and absorption lines are routinely observed in galaxies at redshifts up to 5 with spectrographs on 8-10m class telescopes. While the overall spectra are well understood and have been successfully modeled using empirical and…
The emission spectrum has been calculated of a homogeneous pure hydrogen layer, which parameters are typical for a flare on a red dwarf. The ionization and excitation states were determined by the solution of steady-state equations taking…
We present evidence for variations in the fine-structure constant from Keck/HIRES spectra of 143 quasar absorption systems over the redshift range 0.2 < z_abs < 4.2. This includes 15 new systems, mostly at high-z (z_abs > 1.8). Our most…
Spacetime variations of physical constants can be associated with the existence of Higgs-like scalar field(s) that couple non-universally to the baryonic matter. Recent results of astronomical spectral measurements of the fractional changes…
Luminous high-redshift quasars can be used to probe of the intergalactic medium (IGM) in the early universe because their UV light is absorbed by the neutral hydrogen along the line of sight. They help us to measure the neutral hydrogen…
We construct eigenspectra from the DR1 quasars in the SDSS using the Karhunen-Lo\`eve (KL) transform (or Principal Component Analysis, PCA) in different redshift and luminosity bins. We find that the quasar spectra can be classified, by the…
High-redshift quasars are currently the only probes of the growth of supermassive black holes and potential tracers of structure evolution at early cosmic time. Here we present our candidate selection criteria from the Panoramic Survey…
Although about a dozen high redshift (z larger than 2) starburst galaxies have been recently detected in the CO lines, spectroscopic detections of molecular gas of very young galaxies are still very difficult. The CO lines are usually…
We examine rest-frame ultraviolet spectra of 70 high redshift quasars (z>3.5) to study the chemical enrichment history of the gas closely related to the quasars, and thereby estimate the epoch of first star formation. The fluxes of several…
We present the results of a survey of galaxies selected by their gas cross-section which give rise to MgII absorption lines in the spectra of background quasars. The sample comprises 11 galaxies covering the redshift range 0.7 < z < 1.2,…
Detection of high-redshift absorption in the optical spectra of quasars have provided a powerful tool to measure spatial and temporal variations of physical ``constants'' in the Universe. It is demonstrated that high sensitivity to the…