相关论文: Evidence for overdensity around z_em > 4 quasars f…
We present a method for studying the proximity effect and the density structure around redshift z=2-3 quasars. It is based on the probability distribution of Lyman-alpha pixel optical depths and its evolution with redshift. We validate the…
We have used spectra of 181 projected quasar pairs at separations $\le 1.5$ arcmins from the Sloan Digital Sky-Survey Data Release 12 in the redshift range of 2.5 to 3.5 to probe the proximity regions of the foreground quasars. We study the…
We present a detailed study of the longitudinal proximity effect using a sample of 85 quasars spanning an emission redshift range of $3.5 \leq z_{em} \leq 4.5$ and Lyman continuum luminosity ($L_{912}$) ranging from 1.06$\times 10^{31}$ to…
We analyse the proximity zone of the intergalactic matter around high-redshift quasars in a cosmological environment. In a box of 64 h-1 Mpc base length we employ dark matter only simulations. For estimating the hydrogen temperature and…
The intergalactic medium (IGM) around quasars is shaped by their dense environments and by their excess ionizing radiation, forming a "quasar proximity zone" whose size and anisotropy depend on the quasar's halo mass, luminosity, age, and…
We study quasar proximity zones in the redshift range $5.77 \leq z \leq 6.54$ by homogeneously analyzing $34$ medium resolution spectra, encompassing both archival and newly obtained data, and exploiting recently updated systemic redshift…
We publicly release a new sample of $34$ medium resolution quasar spectra at $5.77\leq z_{\rm em}\leq6.54$ observed with the Echellette Spectrograph and Imager (ESI) on the Keck telescope. This quasar sample represents an ideal laboratory…
Absorption spectra of high redshift quasars exhibit an increasingly thick Ly-alpha forest towards z~6. However, the interpretation of these spectra is complicated by the fact that the Ly-alpha optical depth is already large for neutral…
Measuring the density of the intergalactic medium using quasar sightlines in the epoch of reionization is challenging due to the saturation of Lyman-$\alpha$ absorption. Near a luminous quasar, however, the enhanced radiation creates a…
The introduction of low-frequency radio arrays is expected to revolutionize the study of the reionization epoch. Observation of the contrast in redshifted 21cm emission between a large HII region and the surrounding neutral inter-galactic…
The abundances of metals in the intergalactic medium (IGM) can be used to constrain the amount of star formation at high redshift and the spectral shape of the ionizing background radiation. For both purposes it is essential to measure the…
We investigate the high-redshift quasar luminosity function (QLF) down to an apparent magnitude of I(AB) = 25 in the Cosmic Evolution Survey (COSMOS). Careful analysis of the extensive COSMOS photometry and imaging data allows us to…
Proximity zones of high-redshift quasars are unique probes of their central supermassive black holes as well as the intergalactic medium in the last stages of reionization. We present 22 new measurements of proximity zones of quasars with…
Absorption due to HeII Ly-alpha has been detected at low resolution in the spectra of four quasars between redshifts z = 2.74-3.29. We assess these observations, giving particular attention to the radiative transfer of the ionizing…
The overionized regions surrounding high-redshift quasars, known as proximity zones, provide a window into the interaction between supermassive black holes (SMBHs) and the intergalactic medium (IGM) during the epoch of reionization (EoR).…
The impact of quasars on their galaxy neighbors is an important factor in the understanding of the galaxy evolution models. The aim of this work is to characterize the close environments of quasars at low redshift (z$<$0.2) with the most…
We present a comprehensive analysis of the relationship between galaxies and the intergalactic medium (IGM) during the late stages of cosmic reionization, based on the complete JWST EIGER dataset. Using deep NIRCam $3.5\,\mathrm{\mu m}$…
High-redshift quasars (z >~ 6) drive ionization fronts into the intergalactic medium (IGM). If the thickness of the front can be measured, it can provide a novel constraint on the ionizing spectral energy distribution (SED). Here we follow…
The impact of quasars on their galaxy neighbours is an important factor in the understanding of galaxy evolution models. The aim of this work is to characterize the intermediate-scale environments of quasars at low redshift (z $<$ 0.2) with…
We present our first results of the survey for high redshift quasars at $5 \lesssim {\rm z} \lesssim 5.7$. The search for quasars in this redshift range has been known to be challenging due to limitations of filter sets used in previous…