We present preliminary results of 3-D hydro simulations of the interstellar medium evolution in dwarf spheroidal galaxies undergoing star formation for the first time. The star formation is assumed to occur in a sequence of instantaneus bursts separated by quiescent periods. Different models are made changing the number and the intensity of the bursts in such a way that the final mass of the formed stars remains the same. We followed the enrichment of the ISM taking into account the contribution of both type Ia and II supernovae. The aim of our models is to find a star formation history compatible with the observed spread of stellar age and metallicity in such galaxies and to reproduce the observed mass-metallicity relation.

HE0512–3329 is a gravitationally-lensed double QSO with damped Ly$\alpha$ systems observed at $z=0.931$ in front of both QSO images (DLA A and B). We have obtained spatially resolved HST STIS and optical VLT UVES spectra of both QSOs in order to study differences in the metal abundances across the lines of sight. We detect substantial differences, of roughly 0.5 dex, in both [Mn/H] and [Fe/H], on a transverse scale of 5 $h^{-1}$ kpc. Differential dust depletion appears as the most plausible explanation.

We consider the feedback effects of the early reionization on the formation of small galaxies. For this purpose, we perform 3D radiation hydrodynamic simulations with incorporating the radiative transfer for ionizing photons. As a result, it is found that the early reionization is so devastating for low mass systems with $M_{\rm vir} \lesssim 10^8 M_\odot$ or $v_{\rm circ} \lesssim 20 {\rm km/s}$, and almost all gas is photo-evaporated in more than 95% of low mass systems. These results indicate that the low mass dwarf galaxies are not formed directly from isolated CDM density perturbations.

Radio-selected samples of quasars with complete optical identifications offer an ideal dataset with which to investigate dust bias associated with intervening absorption systems. Here, we review our work on the Complete Optical and Radio Absorption Line System (CORALS) survey whose aim is to quantify this bias and assess the impact of dust on absorber statistics. First, we review previously published results on the number density and gas content of high column density absorbers over the redshift range $0.6<z<3.5$. We then present the latest results from CORALS which focus on measuring the metal content of our unbiased absorber sample and an investigation of their optical–IR colours. Overall we find that although dust is unarguably present in absorption galaxies, the level appears to be low enough that the statistics of previous magnitude limited samples have not been severely affected and that the subsequent reddening of background QSOs is small.

We present preliminary results from the Hamburg/ESO survey for damped Ly-$\alpha$ (hereafter, DLA) systems. This survey is characterised by (i) good knowledge of the biases affecting the parent QSO survey, and (ii) the brightness and (iii) relatively wide magnitude distribution of the background QSOs. Therefore, it is well–suited to study possible magnitude–dependent biases in DLA surveys, such as the one expected from dust obscuration.

We have systematically searched for damped Lyman-$\alpha$ line candidates in 5 Å, resolution spectra of the 188 QSOs that constitute our statistical sample. These candidates have later been re-observed with UVES at the ESO–Very Large Telescope (VLT) for confirmation and accurate $N(HI)$ measurements. In the redshift range covered by the survey, 19 DLA systems have been discovered. Over the whole survey, we find that the number density $n(z)$ and cosmological density of gas $\Omega_\mathrm{gas}$ have comparable values to the ones obtained by CORALS (Ellison et al. 2001).

However, the number densities of DLA systems $n(z)$ in two sub–samples of equal absorption distance path defined by the magnitude of the background QSOs differ by a factor of $\approx 5$. We estimate that the probability that $n(z)$ is equal in the two sub–samples is $<0.003$. A similar, only slightly less significant difference is found for $\Omega_\mathrm{gas}$.

This article reviews the popular reasons for the belief that dwarf elliptical galaxies and (ordinary) elliptical galaxies are distinct and separate species. They include: light–profile shape (or similarly image concentration); the magnitude–central surface brightness diagram; the magnitude–effective surface brightness diagram (or similarly the magnitude–effective radius diagram); and the Fundamental Plane. It is shown how a continuous trend between luminosity and a) light–profile shape, and b) central surface brightness (until the onest of core formation at $M_B \sim -20.5$ mag), results in a unification of the dwarf elliptical and (ordinary) elliptical galaxies. Neither the above four reasons, nor the luminosity function (at least in the Virgo cluster) provide evidence for a division at $M_B=-18$ mag between the dwarf elliptical and (ordinary) elliptical galaxies. Instead, they appear to be continuous extensions of each other.

If dwarf-elliptical galaxies formed their stars very rapdily (on timescales of less than 1 Gyr), they may in principle be detectable out to high redshift. Prior to the discovery of cosmic acceleration, it appeared that rapid and late formation dwarf elliptical galaxies might be required to explain the number counts of faint galaxies. A plausible hypothesis emerged: that photoionization by the UV background prevents gas cooling in low-mass halos until $z \lesssim 1.5$. The discovery of cosmic acceleration eased the tension between predicted galaxy number counts and galaxy-evolution models. Nevertheless, there is some evidence for relatively late star formation in nearby dE's, and the photoionization delay mechanism still appears to have some merit. It is thus of interest to look back in time to see if we can find starbursting dwarf galaxies at moderate redshift. We review the connection between faint-blue galaxies and bursting-dwarf galaxies and discuss some attempts to identify progenitors to dE galaxies in the Hubble Ultra Deep Field (HUDF) observations. We find roughly 85 galaxies in the HUDF with redshifts $0.6<z<1.1$ that appear to have formed most of their stars at $z<1.5$. Of these, 70% have half-light radii less than 1.5 kpc. These are thus “smoking gun” candidates for dwarf galaxies that are either collapsing for the first time at moderate redshifts or have otherwise been unable to form stars for more than 1/3$ of a Hubble time.

We present the observed metallicity distribution for 437 red giants in the Carina dwarf spheroidal (dSph) galaxy that was derived from FLAMES medium-resolution spectroscopy of the near-infrared Ca triplet (CaT). We find a mean [Fe/H] of −1.7, dex and a full spread in metallicities of at least one dex. Most of this width is due to the occurrence of three populations at different [Fe/H], which are likely to be related to the three star forming (SF) episodes that governed Carina's evolution and also correlate with peaks in the age-distribution. Both the lack of any correlation between stellar colour and metallicity and a comparison of the metallicities with chemical evolution models, which suggest a major role of infalling gas, contribute to the detailed understanding of Carina's evolutionary history. Moreover, we find a mild dependence of metallicity on radial location, reflected in a shift of the distribution's peak towards the metal poor end in the outer regions.

Deep galaxy redshift surveys in the field around sight lines that probe OVI absorbers is a powerful method to investigate the nature of these absorbers and their correlation with galaxies. Here we present preliminary results of a study of fields observed with the Gemini/GMOS spectrograph centred on three low redshift QSOs known to probe a variety of OVI systems. Notably, some OVI absorbers appear to be associated with isolated, individual galaxies. Others are clearly found within large-scale structures but at substantial distances from any individual galaxy.

The evolution of dwarf galaxies, particularly any potential morphological evolution among the different types of dwarf galaxies, remains poorly understood. The interstellar medium (ISM) in dwarf galaxies is thought to be more strongly disturbed by star formation episodes in these low mass galaxies, including supernovae-driven winds during starbursts and star formation induced by galaxy-galaxy interactions. Loss of the ISM has been postulated to result in the evolution of dIrrs to dE/dSphs. However, disentangling the relative importance of environmental (galaxy harassment) versus local stocastic processes on star formation, and their effects on subsequent morphological evolution is still a very active area of research. So-called “transition dwarf” galaxies are galaxies that have properties that fall somewhere between gas-rich dIrrs and gas-poor dE/dSphs, and may provide clues to the overall evolutionary history of dwarf galaxies. We report on some recent work on a sample of vigorously star-forming dwarf “transition” galaxies, and suggest that they may be examples of the bridge between dIrrs and dEs/dSphs.

We investigate the chemical abundances of local star-forming galaxies which cause damped Lyman alpha lines. A metallicity versus redshift diagram was constructed, on which the chemical abundances of low-redshift star-forming galaxy populations are compared with those of high-redshift damped Lyman alpha systems. We discuss two types of experiments on individual star-forming galaxies. In the first, the damped Lyman alpha line is created against an internal ultraviolet light source generated by a star-forming cluster or a supernova explosion. In the second, the damped Lyman alpha line is seen against a background quasar. The metallicities measured from ionised gas in the star-forming regions, and neutral gas in the damped Lyman alpha systems, are compared with one another on a case-by-case basis. We highlight the occurrence of the star-forming galaxy/quasar pair SBS 1543+593/HS 1543+5921, where the emission- and absorption-line derived abundances give the same result. We argue that we therefore can in principle interpret damped Lyman alpha system metallicities as an extension of star-forming galaxy metallicities to higher redshifts, supporting the idea that gas-rich galaxies had lower chemical abundances when they were younger.

Recent progress in our knowledge of stellar populations in local dwarf spheroidal galaxies is briefly discussed. A few results are summarized including wide field observations of stellar populations and their spatial variations, studies of AGB and variable stars, extension to near-infrared wavelengths, and the interpretation effort based on synthetic color-magnitude diagrams and chemical evolution models.

The spectra of the Sloan Digital Sky Survey (SDSS) are being used to construct a catalogue of QSO absorption lines, for use in studies of abundances, relevant radiation fields, number counts as a function of redshift, and other matters, including the evolution of these parameters. The catalogue includes intervening, associated, and BAL absorbers, in order to allow a clearer definition of the relationships between these three classes. We describe the motivation for and the data products of the project to build the SDSS QSO absorption line catalogue.

HI 21cm absorption spectroscopy provides an independent probe of the nature of damped Lyman-$\alpha$ systems (DLAs), yielding information on their ISM conditions, kinematics, and spatial extent. We find that the majority of DLAs have significantly higher spin temperatures than seen in the Milky Way and local spirals, indicating larger fractions of the warm phase of HI, especially at high redshifts. Present data suggests that the spin temperature might be used as a secondary indicator of the nature of the absorbing galaxy. We have succeeded in spatially resolving the 21cm absorption in two $z\sim 0.4$ DLAs, thus obtaining lower limits on the transverse extent of these absorbers.

We investigate the 3-D matter distribution at $z\sim 2$ with high resolution ($R\sim 40,000$) spectra of QSO pairs and groups obtained with the UVES spectrograph at ESO VLT. Our sample is unique for the number density of objects and the variety of separations, between $\sim 0.5$ and 7 proper Mpc. We compute the real space cross-correlation function of the Lyman-$\alpha$ forest transmitted fluxes. There is a significant clustering signal up to $\sim 2$ proper Mpc, which is still present when absorption lines with high column density ($\log N \ge 13.8$) are excluded.

We present Surface Brightness Fluctuation (SBF) distances of fifteen early-type dwarf galaxies and the S0 galaxy NGC 4150 in the Local Volume based on deep $B$- and $R$-band CCD images obtained with the 2.56 metre Nordic Optical Telescope (NOT). Distances have been determined from Fourier analysed fields selected from optimal locations on the galaxies. Distances were found to range from 3 to 16 Mpc.

The SBF method has been demonstrated to efficiently measure relatively accurate distances from the ground with mid-aperture telescopes. The SBF method to measure distances to dwarf elliptical (dE) galaxies has also been empirically calibrated using three dEs with known tip of the red giant branch (TRGB) distances.

The discovery of the first damped Lyman alpha (DLA) system in the early 1970s followed by the recognition that DLAs arise in intervening galaxies opened up a new field of galaxy evolution research. These highest HI column density absorption-line systems trace the bulk of the observed neutral gas in the Universe, and therefore, have been used as powerful probes of galaxy formation and evolution back to the redshifts of the most distant quasars. The history and progress of DLA research over the past several decades is reviewed here. Larger datasets and deeper surveys, particularly over the last couple of years, have improved our knowledge of the neutral gas content and distribution in the Universe at all observable redshifts, including the present epoch. New results on the statistics of DLAs at $z<1.65$ from our HST-UV surveys are presented and discussed in the context of recent results at $z=0$ and at high redshift. We find that $\Omega_{DLA}(z>0)$ remains roughly constant to within the uncertainties; the $z=0$ value of the neutral gas mass density, $\Omega_{g}$, is a factor of $\approx 2$ less than $\Omega_{DLA}$. The DLA incidence, $n(z)$, undergoes rapid evolution between redshifts 5 and 2, but is consistent with the no-evolution curve in the current concordance cosmology for $z\lesssim 2$. We also show that if the local Schmidt law relating surface density of gas and star formation rate (SFR) is valid at the DLA redshifts, then the DLA SFR density is too low for them to provide a significant contribution to the cosmic star formation history (SFH) at $z\gtrsim 1$. This implies that the DLAs are unlikely to be the same population as the star forming galaxies (i.e. the Lyman break and sub-millimetre galaxies) that dominate the SFH of the high redshift Universe. We suggest that this discrepancy and the DLA “missing metals” problem could be the result of missing very high column density gas due to its very small absorption cross-section.

We build a sample of O VI absorption systems in the redshift range 2.0 $\lesssim z \lesssim$ 2.6 using high spectral resolution data of ten quasars from the VLT-UVES Large Programme. We investigate the existence of a metal-rich O VI population and define observational criteria for this class of absorbers under the assumption of photoionisation. The low temperatures of nearly half of all O VI absorbers, implied by their line widths, are too low for collisional ionisation to be a dominant process. We estimate the oxygen abundance under the assumption of photoionisation; a striking result is the bimodal distribution of [O/H] with median values close to 0.01 and 0.5 Solar for the metal-poor and metal-rich populations, respectively. Using the line widths to fix the temperature or assuming a constant, low gas density does not drastically change the metallicities of the metal-rich population. We present the first estimate of the O VI column density distribution. Assuming a single power-law distribution, $f$(N) $\propto$ N$^{-\alpha}$, yields $\alpha \sim 1.7$ and a normalisation of $f$(N) $=2.3\times 10^{-13}$ at log N(O VI) $\sim$ 13.5, both with a $\sim$30% uncertainty. The value of $\alpha$ is similar to that found for C IV surveys, whereas the normalisation factor is about ten times higher. We use $f$(N) to derive the number density per unit $z$ and cosmic density $\Omega_{\rm b}$(O VI), selecting a limited column density range not strongly affected by incompleteness or sample variance. Comparing our results with those obtained at $z\sim0.1$ for a similar range of column densities implies some decline of $dn/dz$ with $z$. The cosmic O VI density derived from $f$(N), $\Omega_{\rm b}$(O VI)$\approx (3.5\pm ^{3.2}_{0.9}) \times 10^{-7}$, is 2.3 times higher than the value estimated using the observed O VI sample (of which the metal-rich population contributes $\sim$35%), easing the problem of missing metals at high $z$ ($\sim$ 1/4 of the produced metals) but not solving it. We find that the majority of the metal-rich absorbers are located within $\sim$ 450 km s$^{-1}$ of strong Ly-$\alpha$ lines and show that, contrary to the metal-poor absorbers, this population cannot be in hydrostatic equilibrium. All of the O VI absorber properties imply that there are two distinct populations: metal-poor absorbers tracing the intergalactic medium and metal-rich absorbers associated with active sites of star formation and most probably linked to galactic winds.

LOFAR, the Low Frequency Array, is a new low frequency telescope that is currently being built in the Netherlands. It will initially observe at frequencies from 30 to 240 MHz with baselines of up to 100 km. The aim for the second phase is to carry out sensitive observations below 30 MHz and to extend the maximum baselines up to 400 km. The design of LOFAR is driven by four fundamental astrophysical applications: (i) the epoch of reionisation; (ii) extragalactic surveys and their exploitation to study the formation and evolution of clusters, galaxies, and black holes; (iii) transient sources and their association with high energy objects such as gamma ray bursts; and (iv) cosmic ray showers and their exploitation to study the origin of ultra-high energy cosmic rays. Particularly relevant for this conference is LOFAR's ability to study the epoch of reionisation through observations of the redshifted 21 cm line. This will address several important issues including the source of reionisation and the reionisation history of the Universe. In addition to the science case, LOFAR's instrumental concepts and time line are briefly reviewed. The main technical challenges for LOFAR include rejection of man-made radio interference, dealing with the corrupting influence of the ionosphere on the observations, and minimising contaminations of the EOR signal by foreground discrete astrophysical sources.

Using integral field spectroscopy (IFS) we have observed QSOs which were previously known to have intervening DLAs, to search for emission lines in the field surrounding the QSOs. The sample consists of 13 DLAs plus 7 sub-DLAs at $z>2$, from which we find emission line candidates at the expected wavelengths for 8 systems, implying a detection frequency of 40%. Emission lines detected at the DLA redshifts are interpreted as being due to Ly$\alpha$ lines from galaxies associated with the DLA clouds. Candidates are detected at $3-4\sigma$ levels in both narrow-band images and spectra created from the data cubes. We find no preference for candidate detection associated with either high or low metallicity DLAs. In comparison with the properties of previously known DLA galaxies, the candidates show similar distributions of line fluxes and line widths, but their impact parameters are slightly different, suggesting H I cross sections larger than 10 kpc.