I will describe recent results on constructing samples of candidate active galactic nuclei (AGN) at or beyond redshift 7, probing several orders of magnitude fainter than the top end of the quasar luminosity function at redshift 6. These advances have been made possible by the advent of deep, wide multi-waveband surveys that enable the selection of samples of sources that are detected at radio or X-ray wavelengths but completely undetected at optical wavelengths to very deep limits. A variety of multi-band selection criteria are used to identify the high-redshift candidates and eliminate lower-redshift interlopers by means of extensive spectral energy distribution modelling. The resulting constraints on the numbers of high-redshift AGN at or above redshift 7 are used to examine the evolution of the AGN luminosity function at high redshift, and help understand the properties of the first supermassive black holes in the universe.

We use a semi-analytical approach to simulate absorption spectra of QSOs at high redshifts with the aim of constraining the cosmic reionization history. More details are given in Gallerani et al. (2006) and references therein.

We investigate the possibility of constraining the ionization state of the Intergalactic Medium (IGM) close to the end of re-ionization (z≈6) by measuring the size of the H II regions in high-z quasars spectra, via a combination of SPH and 3D radiative transfer (RT) simulations and a statistical analysis of mock quasar spectra through the simulated cosmological volume.

I discuss the constraints that can be derived on the abundance of high redshift (z>6) (mini)quasars from the unresolved soft X-Ray background. Furthermore, I will show how existing Lyα surveys can be used to probe the very faint MB≳-21 mag (i.e., ≳7–8 mag fainter than the SDSS quasars) end of the z≥,4.5 quasar luminosity function.

I shortly review the investigation of dust in the early universe. I discuss the possible evolution of the dust properties, as well as the possible dust production mechanisms at z>6.

Observations of the most distant (z≃6) QSOs in the centimetre and millimetre regime currently serve as the only direct probe of the host galaxies of these extreme systems in the Epoch of Re-ionization. Such observations reveal that about 1'3 of the hosts contain massive reservoirs of dust (>108M⊙) and molecular gas (>1010M⊙) – the fuel for galaxy formation, and also indicate coeval starbursts at a rate >103M⊙yr−1 adequate to form a large elliptical galaxy in a dynamical timescale. These data imply that a highly metal enriched, molecular ISM, can be generated in galaxies within 870 Myr of the Big Bang. High-resolution imaging of the gas also provide an estimate of the host galaxy dynamical mass. However, current observations are restricted to rare, hyper-luminous IR galaxies. I will close by considering the prospects of observing the gas, dust, and star formation in the first ‘normal’ galaxies (e.g., the Ly-α galaxies) into cosmic reionization (z>6), using ALMA and the EVLA.

We present the optical/NIR spectrum of the afterglow of GRB 050904 obtained with the Faint Object Camera And Spectrograph on the Subaru 8.2m telescope taken 3.4 days after the burst. It is, as of June 2006, the only GRB with a known redshift larger than 6. The spectrum shows a clear continuum at the long wavelength end of the spectrum with a sharp cutoff at around 900nm due to Lyα absorption at a redshift of 6.3 with a damping wing. Little flux is present in the waveband shortward of the Lyα break. A system of absorption lines of heavy elements at redshift z = 6.295±0.002 were also detected, yielding a precise measurement of the largest known redshift of a GRB. Analysis of the silicon and sulphur absorption lines suggests a dense environment around the GRB with the metallicity larger than 0.1 solar, providing unique information on the galaxy and star forming region at z>6. This observation has shown that GRB is a powerful probe of the early universe.

We discuss the implications for the cosmic re-ionization from the optical afterglow spectrum of GRB050904 at z = 6.3

We discuss anisotropies in the near-IR background between 1 to a few microns. This background is expected to contain a signature of primordial galaxies. We have measured fluctuations of resolved galaxies with Spitzer imaging data and we are developing a rocket-borne instrument (the Cosmic Infrared Background ExpeRiment, or CIBER) to search for signatures of primordial galaxy formation in the cosmic near-infrared extra-galactic background.

We consider the influence of decaying dark matter particles and ultra-high energy cosmic rays (UHECRs) on the ability of neutral gas at redshifts z = 10-50 to emit and absorb in the 21cm line. We show that the signal in 21 cm is sensitive to properties of decaying particles and UHECRs, and conclude that future radio telescopes (LOFAR, LWA and SKA) are able not only to detect 21cm signal originated from decaying particles and UHECRs, but discriminate between them as well.

In cold dark matter cosmological models, the first stars to form are believed to do so within small protogalaxies. We study the influence of low levels of metal enrichment on the cooling and collapse of ionized gas in these protogalactic halos using three-dimensional, smoothed particle hydrodynamics simulations.

We discuss the UV radiative feedback on high-redshift proto-galaxies.

A high-accuracy method for the removal of point sources from maps of the cosmic microwave background

The solar magnetic field and its associated atmospheric activity exhibits periodic variations on a number of time scales. The 11-year sunspot cycle and its underlying 22-year magnetic cycle are, besides the 5-minute oscillation, the most widely known. Amplitudes and periods range from a few parts per million (ppm) and 2–3 minutes for p-modes in sunspots, a few 10 ppm and 10 minutes for the granulation turn around, a few 100 ppm and weeks for the lifetime of plages and faculae, 1000 ppm and 27 days for the rotational signal from spots, to the long-term cycles of 90 yr (Gleissberg cycle), 200 - 300 yr (Wolf, Spörer, Maunder minima), 2,400 yr from 14C tree-ring data, and possibly in excess of 100,000 yr.

The polar magnetic fields on the Sun have been an attractive subject for solar researches since Babcock measured them in solar cycle 19. One of the remarkable features of the polar magnetic fields is their reversal during the maxima of 11-year sunspot cycles. I have present results of the investigations of the polar magnetic field using SOHO-mdi data. It is found, that the polar magnetic field reversal is detected with mdi data for polar region within 78°–88°. The North Pole has changed polarity in CR1975 (April 2001). The South reversed later in CR1980 (September 2001). The total unsigned magnetic flux does not show the dramatic decreasing during the polar reversals due to omnipresent bi-polar small-scale magnetic elements. The observational and theoretical aspects of the polar magnetic field reversals are discussed.

We discuss flip-flop cycles in solar and stellar activity.

Typical latitude zones and longitude sectors with a dominant occurrence of newly emerging magnetic flux were systematically detected during three last activity cycles. Two long time persistent longitude sectors with the preferred occurrence of a new strong magnetic flux are characteristic for magnetic flux distribution and their rotation rate is latitude dependent in the relationship with differential rotation rate. Recent new information about the large-scale flows in convection zone relates to a concept of the expected giant cells and jets and show a new relationship with different scales of the large-scale circulation. Non-axially symmetric horizontal flow in upper part of convection zone gives a good motivation for an extension of the existing axially symmetric 2D models into new 3D concept.

We study solar irradiance variability. The current generation of models show that the irradiance since then has increased by between 0.9 and 1.5 W m−2.

Differential rotation is described in stellar dynamo models as one of the fundamental phenomena governing the amplification of magnetic fields in active stars.Using indirect imaging methods, the measurement of photospheric differential rotation is now achieved on a growing number of very active stars, a fraction of which exhibit temporal fluctuations of potentially large amplitude in their latitudinal shear, on a time-scale of a few years. I first describe the modeling tools on which such analysis is based, then discuss the implications of this observational work on our understanding of stellar dynamos and of the impact stellar magnetic fields may have on the dynamics of convective envelopes.

We discuss a recalibration of Ca II H&K measures in sun-like stars