Dynamical studies of the centers of galaxies have received a tremendous push forward with the launch of the Hubble Space Telescope. Thanks to its superb resolution power, HST has made it possible not only to convincingly demonstrate the existence of supermassive black holes (SBHs) in galactic nuclei, but also to investigate how SBHs relate to the overall structure of the host galaxy. In spite of this, many questions remain unanswered, for instance, how do scaling relations for SBHs evolve with cosmic time? What is the exact characterization of the local SBH mass function? Are there upper and lower limits to the mass a SBH can attain? The next generation of 30m telescopes will provide the leap in resolution capabilities and collective power which is necessary to address the above questions. I will discuss some of the main science drivers in the field of galaxy dynamics, and the instrument requirements needed to achieve them.

The combination of the collecting power of an ELT with an ultra-stable high resolution spectrograph opens up the possibility to measure for the first time directly the dynamical effect of the acceleration of the Universe. CODEX will also provide unique opportunities for advance in many other branches of astrophysics. The CODEX design is based on an array of several identical spectrographs. It is highly modular and can be easily adapted to a large range of sky apertures and telescope diameters. CODEX is designed to work as a seeing limited instrument. The requirements for the telescope are moderate and clearly identified.

Cosmological variations in the fine structure constant, $\alpha$, can be probed through precise velocity measurements of metallic absorption lines from intervening gas clouds seen in spectra of distant quasars. Data from the Keck/HIRES instrument support a variation in $\alpha$ of 6 parts per million. Such a variation would have profound implications, possibly providing a window into the extra spatial dimensions required by unified theories such as string/M-theory. However, recent results from VLT/UVES suggest no variation in $\alpha$. The COsmic Dynamics EXperiment (CODEX) spectrograph currently being designed for the ESO OWL telescope (Pasquini et al. 2005) with a resolution high enough to properly resolve even the narrowest of metallic absorption lines, $R \gt 150000$, will achieve a 2-to-3 order-of-magnitude precision increase in $\Delta\alpha/\alpha$. This will rival the precision available from the Oklo natural fission reactor and upcoming satellite-borne atomic clock experiments. Given the vital constraints on fundamental physics possible, the ELT community must consider such a high-resolution optical spectrograph like CODEX.

Wide-field spectroscopy, in its various forms, has much to contribute to ELT science, so care is needed in trade-offs between telescope size and field of view. Integral field spectroscopy over large areas at high spatial resolution, and especially multiple integral fields, will be essential tools. For wide-field surveys, next-generation multi-object spectrographs (MOS) on 8m-class telescopes will likely out-perform similar instruments on ELTs, due to the smaller fields of view of the current ELT designs. However, there may be $D^4$ gains for medium-resolution MOS if adaptive optics can provide enhanced ‘seeing’ of $\sim0.1''$ over wide fields. New technologies such as OH-suppression fibres offer revolutionary gains, so there is a difficult balance to be achieved in applying the latest technology and having instruments ready for ELT first light.

The requirements on ELTs from the perspective of X-ray astronomy are explored. These requirements will be driven largely by deep X-ray surveys, like those conducted with XMM-Newton and the Chandra X-ray Observatory. Up to the present time, ground-based telescopes have largely kept abreast of the needs arising from deep X-ray surveys, i.e. the current generation of 10m-class telescopes is able to (barely) match the required spectroscopic needs for optical identifications in most cases (up to 70%). There are two X-ray astronomy facilities currently proposed and under study: the European-led X-ray Early Universe Spectroscopic mission (XEUS) and the NASA proposal Constellation-X. The emphasis of both these missions, like XMM-Newton, is X-ray spectroscopy, but they will both perform deep surveys which will need optical follow-up spectroscopy towards the middle or end of the next decade.

A key pursuit of 10-meter-class optical-infrared telescopes is to use deep imaging and spectroscopic surveys to track the evolution of galaxy structure. Future telescopes will continue this quest back to the epoch of the first galaxies, reaching ever fainter structures at ever higher redshifts. Apertures of 20, 30, 50, and 100 meters equipped with the latest in adaptive optics will look out from the world's foremost observing sites, and incrementally improve on point-source sensitivity. But how will they compare for studying extended structures? Scientific avenues that can be pursued with poorer spatial resolution, but require low backgrounds - for example, tracing the formation history of bulges - might allow for tradeoffs between aperture, site, and cost. To explore this parameter space I use a published model of average seeing at any site, develop a simple telescope performance and cost model, and simulate resultant galaxy images over a wide range of absolute brightness, size, bulge fraction, inclination, and redshift. I present a graphical interface to the model which allows side-by-side visual comparison of a given galaxy for any two observatories. This approach is intuitive and flexible, although probably not well suited for detailed analysis of a particular telescope. I compare observatory cost against the relative accuracy of measured galaxy bulge-to-total ratio, and comment on telescope and site requirements.

Recent spectroscopic observation of $z=6.3$ GRB 050904 is reported with an emphasis on the importance of making similar prompt spectroscopy for long burst GRB events yet to come. A preliminary result of a survey for $z\sim7.0$ Lyman $\alpha$ emitters (LAEs) using a narrow band filter NBF973 is also presented.

Verification of theoretical predictions of an oscillating behavior of the fine-structure constant, $\alpha$, with cosmic time requires high precision measurements at individual redshifts, while in earlier studies the mean $\Delta\alpha/\alpha$ values averaged over wide redshift intervals were usually reported. This requirement can be met via the Single Ion Differential $\alpha$ Measurement (SIDAM) procedure. We apply SIDAM to the FeII lines associated with the damped Ly$\alpha$ system observed at $z = 1.15$ in the spectrum of HE0515–4414. The weighted mean calculated on the base of carefully selected 34 FeII pairs is $\langle \Delta\alpha/\alpha \rangle = (-0.07\,{\pm}\,0.84)\times10^{-6}$. The precision of this estimate represents a large improvement over previous measurements of $\Delta\alpha/\alpha$.

When falling into a galaxy cluster, the spiral - rich field galaxy population gets transformed into the characteristic E/S0/dE/dSph - rich cluster galaxy population and this already happens at surprisingly large galactocentric radii around $\sim$3R$_{virial}$. A variety of transformation processes are discussed, their respective importance and timescales. Their relations to the cluster properties, however, remain to be explored. Galaxy transformation processes, transition stages, and timescales can very well be explored by a comparison of deep multi-band imaging for a large fraction of the cluster galaxy population (down to M$^{\ast} + 3$ mag out to redshifts ${z \sim 0.5}$) and of spectroscopy of the brighter members with evolutionary synthesis models. SALT's large collecting area and field of view together with its unique $U$-band sensitivity are ideal in this respect.

Current models for dark energy include a cosmological constant and scalar field models such as quintessence and k–essence. By measuring the dark energy sound speed, $c_{\hbox{\scriptsize\it eff}}$, and its equation of state parameter, $w$, one can distinguish between these. Here we investigate the possibility of measuring $c_{\hbox{\scriptsize\it eff}}$ and $w$ using combined observations from the SKA and CMB experiments. We present theoretical predictions for the cross–power spectrum of ISW fluctuations in the CMB and the expected field of HI galaxies detectable with the SKA.

Black hole (BH) theories predict the existence of an “intermediate” mass BH at the centers of dwarf elliptical (dE) galaxies. These intermediate mass black holes (IMBHs) are believed to bridge the observational gap between stellar-mass BHs ($M_{\rm BH} \lesssim 10^3{\rm M_\odot}$) and supermassive BHs ($M_{\rm BH} \gae 10^6{\rm M_\odot}$). Our project aims at finding tighter empirical constrains on the existence, location, and mass range of these hypothetical objects. For this purpose, we are conducting a deep IMBH search in a sample of $\sim$30 Local Volume dwarf galaxies. Using the Robert Stobie Spectograph (RSS) on the newly constructed Southern African Large Telescope (SALT), long-slit spectroscopic observations along the major-axis will be acquired for each galaxy to determine their kinematic and dynamical properties, particularly at their centers.

A tiny fraction (<1%) of very metal-deficient (12+log(O/H)≤7.6) blue compact dwarf (BCD) galaxies exhibits a nearly galaxy-wide starburst activity and no signatures of an old stellar host galaxy. The evolutionary status and formation history of these most metal-deficient BCDs are still a subject of debate. Various lines of evidence suggest, however, that these systems do not contain a substantial population of stars older than $\sim$1 Gyr and hence qualify as nearby young-galaxy candidates. Elaborated multiwavelength studies of these rare, most metal-deficient BCDs may therefore provide crucial insights into the formation and starburst-driven evolution of low-mass galaxies in the early universe.

Using the Lyman break technique (e.g., Steidel et al. 1995), large samples of star-forming galaxies at $2 \lt z \lt 5$ have been identified and studied. These Lyman break galaxies (LBGs) are UV-luminous and thought to be similar to local starburst galaxies; they are relatively small (r$_{h}$=1-3 kpc), have relatively low mass (10$^{9.5-11}$M$_\odot$) and low extinction. However, their role in galaxy evolution is still debatable. Do all galaxies go through a Lyman Break phase? How biased is our view of galaxy evolution due to the Lyman break technique? Are LBGs the building blocks of larger systems or just small galaxies having their first burst of star-formation? Therefore, a census of the star-forming galaxy population as a function of time is needed in order to help us better understand how galaxies acquired their present morphology. In this contribution, I discuss the physical properties of a sample of UV-selected galaxies at intermediate redshifts. I conclude by showing that galaxies of all types, sizes and shapes are forming stars at intermediate-z. However, deep image and spectroscopy with large telescopes are needed in order to properly address their nature.

Neutron stars, containing typically 1.4 solar masses within a diameter of about 15km, are among the smallest astronomical sources and the densest known form of directly observable matter in the Universe. Many aspects of the neutron star remain poorly understood. Most theoretical models for neutron stars cannot, so far, account for many of the observations, which have been largely made at radio wavelengths. This paper discusses the importance of multiwavelength studies, using large telescopes, to better understand the properties and behaviour of these objects.

Using ROSAT seven isolated neutron stars have been discovered characterised by blackbody spectra at temperatures of 400-800 thousand K and the absence of radio and high energy emissions. Observations with Keck, HST and VLT show faint optical counterparts (m $\sim $ 24–29) with Rayleigh-Jeans-type spectra ($\sim\nu ^{2}$) and large proper motions. These objects are believed to be cooling neutron stars. They are of great interest from the point of view of neutron star astrophysics and nuclear physics. In particular, they allow us to measure neutron star radii and thus to constrain the equation of state at very high densities. We discuss the possibility of discovering larger samples of these objects with future sensitive X-ray sky surveys and follow-up optical observations with extremely large telescopes.

Conventionally, CMD analyses of nearby star clusters are based on observations in 2 passbands. They are plagued by considerable degeneracies between age, metallicity, distance (and extinction) that can largely be resolved by including additional passbands with $U$ being most appropriate for young star clusters and I or a NIR band for old globular clusters. For star clusters that cannot be resolved, integrated photometry in suitably selected passbands was shown to be as accurate as spectroscopy in independently revealing ages, metallicities, internal extinction, and photometric masses and their respective 1$\sigma$ uncertainties, when analysed with a dedicated analysis tool for their Spectral Energy Distributions (=SEDs) (cf. Anders et al. 2004a, b, de Grijs et al. 2003b). For external galaxies, rich star cluster populations can thus be efficiently analysed using deep exposures in 4 suitable filters. Again, the inclusion of the $U$-band significantly reduces the uncertainties in the cluster parameters. The age and metallicity distributions of star cluster systems yield valuable information about the formation history of their parent galaxies (Fritze – v. Alvensleben 2004). Here, we present our GALEV evolutionary synthesis models for star clusters of various metallicities (Anders & Fritze - v. Alvensleben 2003), recently extended to include the time evolution of CMDs, the dedicated SED Analysis Tool AnalySED we developed, show results on the basis of HST data, and first results from our SALT PVP project on young star clusters in starburst and interacting galaxies.

Spectropolarimetry has a broad spectrum of applications, for which there are mostly no substitute observing techniques. They range from the measurement of the strength and structure of magnetic fields via the detection of scattered light from sources obscured by high-density matter or lost in the glare of a nearby bright object to the possibility of individual corrections to the intrinsic luminosities of far-away Type Ia supernovae - and many more. First reconnaissance projects have succeeded with 10m-class telescopes. But the application and extension of the insights gained require substantially larger telescopes. An ELT would in particular enable studies of the formation of structure (AGNs, $\gamma$-ray bursts) in early phases of the universe. At the large distances an ELT will reach, the spatial resolution of point sources, even though only at a very low level, will eventually beat any interferometer. Low cost, the possibility to exploit also not perfectly photometric nights, and the $D^4$ sensitivity of background-limited observations of point sources to telescope diameter are other strong assets.

The capability of extremely large telescopes (ELTs) to resolve stellar populations in distant galaxies has been investigated through simulation. With real stellar clusters as templates, images were created using a realistic point spread function model. Through variation of parameters such as aperture, Strehl ratio and exposure, as well as use of various stellar populations and densities, we study ELT capability to probe galaxy formation and evolution history. We conclude that a 50m ELT should allow study of these processes in the Virgo galaxy cluster.

The stellar Initial Mass Function (IMF) is a quantity which accounts for the distribution of the masses of stars, when they are formed. All the information available on the IMF in the low-mass regime comes from studies of our galaxy alone. Investigations on the content of low-mass stars in other neighbouring galaxies are limited by observational constraints, which do not allow the detection of the fainter stars with statistical significance. Only recently results from observations with the Hubble Space Telescope (HST) of stellar populations in the Large Magellanic Cloud (LMC) down to $\sim$ 0.7 M$_\odot$ confirm systematic variations in the low-mass IMF expected from theoretical considerations (Gouliermis et al. 2005). Direct imaging of resolved stellar populations in massive young clusters throughout the Local Group would be possible with Extremely Large Telescopes (ELTs). Hence, a sizeable sample of young clusters for which IMF variations can be detected would become available. We present our method for testing the efficiency of observations with ELTs in detecting low-mass stars in compact clusters of the Local Group galaxies. We plan to simulate imaging with ELTs and use the results of their photometry in order to investigate the effect on the derived low-mass IMF. This method demonstrates the advantages that will be introduced to crowded field photometry in close-by galaxies with ELTs.

Modelling and simulation, based on observational data, were used to examine the potential of ELT photometry for studies of the evolution of distant galaxies. An open cluster, a globular cluster and two mixed field populations were employed. Colour-magnitude and metallicity diagrams were examined. For younger populations, excellent turn-off-point age data and abundance data can be obtained even beyond 20Mpc. Higher population age weakens data if not improved with longer exposures. Still, the great potential of ELT photometry for studies of the evolution of galaxies is confirmed. Comments are given on adaptive optics and photometry.