相关论文: Ionization of large-scale absorbing haloes and fee…

Observations suggest that CII was more abundant than CIV in the intergalactic medium towards the end of the hydrogen reionization epoch. This transition provides a unique opportunity to study the enrichment history of intergalactic gas and…

Massive stars at redshifts z > 6 are predicted to have played a pivotal role in cosmological reionization as luminous sources of ultra-violet (UV) photons. However, the remnants of these massive stars could be equally important as X-ray…

We report the results of a survey for HI 21-cm absorption at z < 0.4 in a new sample of radio sources with the Giant Metrewave Radio Telescope. Of the 11 sources for which there are good data, we obtain zero detections, where four are…

We present measurements of the large-scale (~40 comoving Mpc) effective optical depth of HeII Ly$\alpha$ absorption, $\tau_{\rm eff}$, at 2.54<z<3.86 toward 16 HeII-transparent quasars observed with the Cosmic Origins Spectrograph (COS) on…

High-redshift radio galaxies (HzRGs) are among the most massive galaxies in the Universe and sites of extreme active galactic nuclei (AGN) feedback processes, powering energetic radio jets. They are typically embedded in giant Ly$\alpha$…

We have performed RIJHK_S imaging of the field around the z=2.67 quasar Q0836+113, which presents several metal line and a damped Ly\alpha absorption systems in its spectrum. The images reveal the existence of a red K_S=18.9 object \approx…

Upon an expansion of all of the searches for redshifted HI 21-cm absorption (0.0021 < z 5.19), we update recent results regarding the detection of 21-cm in the non-local Universe. Specifically, we confirm that photo-ionisation of the gas is…

We present analyses of the physical conditions in the z=0.22496 and z=0.22638 multi-phase O VI absorption systems detected in the ultraviolet HST/STIS and FUSE spectra of the quasar H1821+643. Both absorbers are likely associated with the…

A numerical calculation of properties of finite absorbers and of intergalactic medium based on photoionization equilibrium is performed to confront alternative UV sources in addition to quasars. It is seen that a spectrum including a large…

In this letter, we investigate the nature of the dramatic `super-bubble' emission structures associated with the z=2.44 radio galaxy MRC 0406-244, using rest-frame optical spectroscopy and an archival HST NICMOS image. Based on the optical…

We report the discovery of an unambiguous, substantial low-energy cutoff in the broad band X-ray spectrum of the radio quasar RXJ1028.6-0844 at a redshift of 4.276 obtained with the ASCA satellite, which we preferably explained as…

Ne VIII absorbers seen in QSO spectra are useful tracers of warm ionized gas, when collisional ionization is the dominant ionization process. While photoionization by the ultraviolet background (UVB) is a viable option, it tends to predict…

We present the detection and analysis of a weak low-ionization absorber at $z = 0.12122$ along the blazar sightline PG~$1424+240$, using spectroscopic data from both $HST$/COS and STIS. The absorber is a weak Mg II analogue, with incidence…

We explore the effects of UV absorbing material on the shape of the EUV continuum radiation emitted by the active galactic nucleus, and on the relative strengths of emission lines, formed in the narrow line regions of Seyfert galaxies,…

Using a combination of radio and optical imaging at 0.1\arcs to 0.2\arcs resolution with the VLA/MERLIN and HST has led to a breakthrough in our understanding of radio emission from distant (0.1<z<3) starburst galaxies. We have recently…

Using the Karl G. Jansky Very Large Array (VLA), we have detected absorption lines due to carbon-monoxide, CO(J=0-1), and the cyano radical, CN(N=0-1), associated with radio galaxy B2 0902+34 at redshift z=3.4. The detection of…

We have compared the UV line ratios of a sample of very high redshift radio galaxies with shock and AGN photoionization models, with the goal of determining the balance between jet-induced shocks and AGN illumination in the extended…

Cool neutral gas provides the raw material for all star formation in the Universe, and yet, from a survey of the hosts of high redshift radio galaxies and quasars, we find a complete dearth of atomic (HI 21-cm) and molecular (OH, CO, HCO+ &…

We have analyzed the broad absorption line system of the bright (V=16.5) high-redshift (z=2.361) QSO SBS1542+541 using UV spectra from the HST FOS along with optical data from the MMT and the Steward Observatory 2.3m telescope. These…

From the first published z > 3 survey of 21-cm absorption within the hosts of radio galaxies and quasars, we found an apparent dearth of cool neutral gas at high redshift. From a detailed analysis of the photometry, each object is found to…