We present results from an ongoing program to map the spatial distribution of ices in dark cloud cores with the Spitzer Space Telescope and VLT-ISAAC. The ice maps are used to directly trace the freeze-out of CO and the formation of H2O, CH3OH and CO2.

This paper describes a novel concept for the direct detection of exoplanets involving two spacecraft. One spacecraft is an occulter, designed to provide adequate starlight suppression within its shadow. The second spacecraft, a conventional telescope of standard quality, is flown into the shadow of the first and used to collect the light from the target planet. The design of the occulter and its expected performance are discussed. It is shown that is possible to simultaneously achieve the necessary contrast ratios and inner working angles necessary to have a scientifically meaningful mission. A brief discussion of the estimated tolerances indicate that such a mission is feasible in the near term.

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.

I review the formation of massive stars in the context of a forming stellar cluster. High-mass stars form in the centre of stellar clusters and thus must be understood in the context of low-mass star formation. Furthermore, they are predominantly in binary systems making further constraints on the formation mechanism. The fragmentation of a turbulent molecular cloud produces a large number of stars with initial masses close to the Jeans mass of the cloud. These stars fall together to form small-N clusters that grow through the infall of gas and stars into the cluster's potential well. Competitive accretion in clusters produces high-mass stars in the cluster centre and a full initial mass function of lower-mass stars. Massive star formation is a process that occurs in the cores of stellar clusters and commonly produces close binary systems. Accretion also forces the cluster to contract, increasing the stellar densities to the point where stellar collisions may occur. Furthermore, accretion in clusters reproduces the high binary frequency of massive stars. Systems evolve from low-mass wide binaries to high-mass close binaries due to gas accretion. This evolution can produce very tight binaries that are expected to merge to form the most massive stars. Binary mergers require stellar densities of order 106 stars pc−3, 100 times smaller than is required for single-star collisions.

This report, like its predecessors, focuses on areas which have been especially active since the last General Assembly. Two major developments have been the unification of the T-dwarf standards and the new general catalogue of stellar spectral classifications.

ELT's, interferometers and their multi-aperture direct-imaging form called hypertelescopes are expected to provide images of exo-Earths, and even resolved images in the latter case. Both terrestrial and space versions are potentially usable, although high-performance adaptive optics will be needed on Earth. Current advances in the way of hypertelescopes on Earth and in space are briefly described.

The Very Energy Radiation Imaging Telescope Array System (VERITAS) in its first phase of operation will consist of an array of 4 Imaging Atmospheric Cherenkov Telescopes (IACTs) arranged in a ‘Mercedes’ star configuration. To be located at a high, dark site in Southern Arizona the full array is expected to see first light in October 2006. In February of 2005 the first VERITAS telescope achieved first light at a temporary location near to the final site. This poster summarises the status of the VERITAS instruments as of summer 2005.

This report covers the activity period 2002–2005 of the IAU Working Group on Massive Stars

The early results on astrochemistry from the Cores to Disks (c2d) Legacy program are summarized. The c2d program focuses on the formation of low-mass stars in nearby (within about 300 pc) clouds. Spectroscopy with IRS includes the following topics: ices seen against background stars, in protostellar envelopes, and in disks; grain growth and mineralogy, PAHs, and gas in circumstellar disks.

If the CDM paradigm is correct, then dwarf galaxies are far rarer than dark matter haloes of comparable circular velocity at the present day. Some process or processes must suppress galaxy formation almost completely on these small scales. Several plausible mechanisms may explain the scarcity of dwarf galaxies in the local universe, but it has been hard to distinguish between the different models observationally. The spatial distribution and kinematics of dwarf galaxies contain additional information about the age and formation history of these systems. Interpreted in the CDM framework, they provide powerful new constraints on the physics of dwarf suppression, ruling out at high significance the simplest models, in which the halo occupation probability is constant above some fixed mass or velocity threshold. We describe recent tests of small-scale galaxy formation models using the satellites of the local group and other nearby groups, and discuss the implications of these results for studies of the stellar halo, sub-galactic dark matter and the reionization of the universe at high redshift.

Massive protostars are generally enshrouded in dust, so that most of their radiation emerges in the far infrared. For protostars embedded in opaque, spherical cores, the spectral energy distribution (SED) is determined by two distance-independent parameters, the luminosity-to-mass ratio, $L/M_c$, and the surface density of the core, $\Sigma=M_c/(\pi R_c^2)$, where $R_c$ is the radius of the core. Chakrabarti & McKee (2005a) have derived an approximate analytic expression for the SED that agrees well with numerical results. It is generally not possible to infer the power-law of the density from the SED of a massive protostar. Masses and accretion rates are inferred for several well-studied sources.

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.

We show that rotation plays a major role for very low metallicity stars, even if the distribution of angular velocities $\Omega$ with respect to critical values is the same as at solar $Z$. The internal gradients of $\Omega$ are much larger at lower metallicity $Z$, which enhance internal mixing and give rise to N-enrichments. Low $Z$ stars easily reach break–up during MS evolution and lose mass. They also lose mass as red giants or supergiants due to their surface enrichments in heavy elements. The winds of low $Z$ stars make peculiar contributions to the chemical yields. We suggest that the helium rich blue Main Sequence (bMS) of $\omega$ Centauri bears the signature of such enrichments by the stellar winds of rotating stars in the first stellar generations.

Thanks to the comprehensive sets of elemental abundances in eleven damped Ly$\alpha$ systems (DLAs) at $z_{\rm abs}=1.7-2.5$, we were able for the first time to study in detail the abundance patterns of a wide range of elements, the chemical variations in the interstellar medium, the star formation, and the age of galaxies outside the Local Group. Comparing the gas-phase abundance ratios of these high redshift galaxies, we found that they are very uniform, showing low RMS dispersions up to only 2–3 times higher than the statistical errors, for the majority of elements. The gas-phase abundance patterns of interstellar medium clouds within the DLA galaxies detected along the velocity profiles show on the other hand a high dispersion in several abundance ratios, indicating that variations in the gas phase, whatever their origin, are more confined to clouds within the DLA galaxies than to integrated profiles. The analysis of the cloud-to-cloud chemical variations within seven individual DLAs revealed that five of them show statistically significant variations, higher than 0.2 dex at more than 3 $\sigma$. The sources of these variations are both differential dust depletion and ionisation effects, however no evidence for variations due to different star formation histories was highlighted. These results place important constraints on scenarios of galaxy formation within the CDM hierarchical theory. The DLA abundance pattern comparison with chemical evolution models indicate that the DLAs may either be associated with the outer regions of spiral galaxies or with dwarf irregular galaxies both characterised by star formation histories with low star formation efficiencies. They may be very young galaxies with ages between 20–250 Myr, but also galaxies with ages longer than 1 Gyr. Their star formation rates per unit area are moderate, between $-3.2<\log {\rm SFR}<-1.4$ M$_{\odot}$ yr$^{-1}$ kpc$^{-2}$.

The joint U.S. and German SOFIA project to develop and operate a 2.5-meter infrared airborne telescope in a Boeing 747-SP is now in the final stages of development. First science flights will begin in 2008. The observatory is expected to operate for over 20 years. The sensitivity, characteristics, science instrument complement, and examples of 1-st light spectroscopic astrochemistry science are discussed.

Any predictive theory of star formation must explain observed variations (or lack thereof) in the initial mass function. Recent work suggests that we might expect quantitative variations in the IMF as a function of metallicity (Larson 2005) or magnetic field strength (Shu et al. 2004). We summarize results from several on-going studies attempting to constrain the ratio of high to low mass stars, as well as stars to sub- stellar objects, in a variety of different environments, all containing high mass stars.

First, we examine the ratio of stars to sub–stellar objects in the nearby Mon R2 region utilizing NICMOS/HST data. We compare our results to the IMF by Kroupa (2002) and to the observed ratios for IC 348 and Orion. Second, we present preliminary results for the ratio of high to low mass stars in W51, the most luminous HII region in the galaxy. Based on ground–based multi–colour images of the cluster obtained with the MMT adaptive optics system, we derive a lower limit to the ratio of high-mass to low-mass stars and compare it to the ratios for nearby clusters. Finally, we present the derived IMF for the R136 region in the LMC where the metallicity is 1/4 solar using HST/NICMOS data. We find that the IMF is consistent with that characterizing the field (Chabrier 2003), as well as nearby star–forming regions, down to 1.0 M$_\odot$ outside 2 pc. Whereas the results for both Mon R2 and R136 are consistent with the nearby clusters, the ratio of high to low mass stars in W51 tentatively indicates a lack of low–mass objects.

Determining and understanding the abundances seen in red-giant stars has taken a central role in our understanding of many branches of modern astrophysics. Activity in the area continues apace, both in terms of the fundamental physics of the stellar nucleosynthesis as well as its implications for wider fields. A major role of the Working Group has been to facilitate meetings where the fundamental role of these stars can be further understood and exploited by other researchers.

In order to study the effects of fast rotation on primordial stars, we present the evolution and the chemical yields of zero metallicity models with masses between 15 to 200 M[odot ].

Many past attempts to kill MOND have only strengthened the theory. Better data on galaxy velocity curves clearly favor MOND (without fine-tuning) over cold dark matter. The usual critism on the incompleteness of classical MOND has spurred a Modified Relativity (MR) by Bekenstein. After outlining cosmology and lensing in MOND, we review MOND on small scales. We point out some potential problems of MOND in two-body relaxation and tidal truncation. We argue that the tidal field in any MOND-like gravity theory predicts that the Roche lobe sizes of a binary system are simply proportional to the binary baryonic mass ratio to the power 1/3. An immediate application of this result is that the tidal field and tidal truncation radii of million-star globular clusters and million-star dwarf galaxies (e.g., the Milky Way satellites NGC2419 and Carina) would be very similar because of the one-to-one relation between gravity and baryon distribution. This prediction appears, however, inconsistent with the fact that all globulars are truncated to much smaller sizes than all dwarf galaxies. Whether tide is uniquely determined by baryons can also be used to falsify any MOND-like gravity theory, whether classical or relativistic.

Direct detection of a planet around a star by a nulling interferometer, requires to minimize as far as possible the stellar leaks due to the resolved angular size of the star. The original Bracewell configuration features a nulling function in $\theta^{2}$ which is insufficient in many cases. Several interferometric configurations have been proposed in order to improve the quality of the rejection with a nulling function $\theta^{n}$ with $2 \leq n \leq 6$. I proposed recently a method to build linear configurations of telescopes that achieve nulling function $\theta^{n}$ for any even value of n, using the Prouhet-Thué-Morse sequence to select those telescopes where a π phase shift is applied. In a first part, I recall the basis of this method and its generalization to 2D configurations and 1D arrays of non-identical telescopes, or even to configurations where the phase shift is not π. In a next step, I evaluate the efficiency of deep nulling interferometers in real world, i.e. when nulling is not perfect because of variations of distances or of phase shift between telescopes. I conclude that there is a clear advantage given by the highest order systems that keep a better nulling capability than conventional interferometers, even in severe conditions where parameters driving the nulling performance are highly fluctuating.