January 13, 16:30 hr: Dr. Gerard DAIGNE
Abstract The actual situation with celestial reference frames in the optical range will be recalled. Basic principles of future space astrometry missions will be described and strengthened in a comparison of all-sky surveys and dual-(or multiple-)field optical interferometers. In the perspective of narrow-angle measurements with the VLTI, a post-Hipparcos mission is shown to be needed for boosting the impact of such improvements in ground-based, near-IR astrometry.
January 16, 16:30 hr: Dr. Andrew COLLIER-CAMERON
Abstract Since late 1995, more than 100 giant planets have been discovered orbiting stars other than the Sun. Among the most puzzling of these objects are the "hot Jupiters" , whose 3 to 7-day orbits appear to have resulted from orbital migration early in their formation history. In this talk I review the current state of exoplanet studies, with particular emphasis on theoretical models of their interior structure and atmospheric composition. I then discuss progress and prospects for the direct study of these planets' atmospheres using optical and infrared spectroscopy.
January 22, 16:30 hr: Dr. Bruno ALTIERI
Abstract ESA's Infrared Space Observatory (ISO) was used to perform a deep survey with ISOCAM through three massive gravitationally lensing clusters of galaxies. A total of 145 mid-infrared sources were detected and I present associated source counts. At 15 micron these counts reach the faintest level yet recorded. Almost all of the sources have been identified with counterparts in the optical and/or near-infrared. Detailed models of the three clusters have been used to correct for the effects of gravitational lensing on the background source population. Lensing by the clusters increases the sensitivity of the survey, and the weakest sources have lensing corrected fluxes of 5 and 18 microJy at 7 and 15 micron, respectively. Roughly 70% of the 15 micron sources are lensed background galaxies. We resolve 2.7 � 0.6 nW/m-2sr-1 of the 15 micron infrared background into discrete sources by integrating over our source counts, concatenated to those from other extensive ISOCAM surveys, in the flux range from 30 microJy to 50 mJy. These results confirms that abundant star formation occured in very dusty environments at z~1, at a much larger rate than today, and a factor 5 higher than in non-extincted regions at z=1, as deduced from UV studies.
January 28, 16:30 hr: Dr. Javier LICANDRO
Abstract Near infrared spectroscopy is a useful tool to study the surface properties of minor bodies. In particular is very important to detect ices (water ice, methanol, etc) in the surface of icy minor planets. Making use of the the low-resolution high throughput spectroscopic mode of the Near Infrared Camera Spectrograph (NICS) installed in the 3.5m Telescopio Nazionale Galileo (TNG) at El Roque de los Muchachos Observatory, early 2000, we started a program to study the surface properties of trans-neptunian objects (TNOs), Centaurs and comet nuclei. In particular we obtained the first ever published near infrared spectra of TNOs taken with a 4m class telescope. In this talk I present the characteristics of the instrument and the results already obtained.
February 5, 16:30 hr: Dr. Renato FALOMO
Abstract I will first review the methods to evaluate the black hole mass in normal and active galaxies. These are then used to evaluate and compare the black hole masses of active galaxies of different power: radiogalaxies, BL Lac objects and radio loud quasars.Finally the relation between BH properties and radio emission is discussed.
February 12, 16:30 hr: Dr. Gian-Luca ISRAEL
Abstract I will present the results obtained during the 2001 and 2002 observational campaigns of RXJ0806.4+1527 carried out with the VLT and the Chandra and NewtonXMM X-ray telescopes. RXJ0806.4+1527 is a recently identified binary system, the detected 5min modulations of which have been interpreted as the orbital period of a system containing two white dwarfs. The observational findings will be discussed on the light of the proposed scenarios to account for the nature of this unique binary system.
February 19, 16:30 hr: Dr. Elisabetta DOTTO
Abstract Ten years since the discovery of the first Trans-Neptunian Object, 1992 QB1, our knowledge of the population of these bodies is greatly improved thanks to the big telescopes now available. About 700 TNOs have been discovered so far. They are supposed to be remnants of the protoplanetary disc and to contain information useful in understanding the origin and the evolution of the Solar System and other planetary systems. A summary of the dynamical structure and the present knowledge of the physico-chemical nature of this population will be presented.
February 28, 16:30 hr: Dr. Didier QUELOZ
Abstract The HARPS spectrograph has been successfully commissioned at La Silla. I will present an overview about the instrument and its use in the context of the planet search as well as for asteroseismology measurements.
March 13, 16:30 hr: Prof. Michel MAYOR
Abstract The number of detected exoplanets is large enough to search for statistical properties of planetary systems. Despite the still existing detection bias we already have a few emerging statistical properties giving some hints (or new questions) on formation scenarios. This seminar will also give us the opportunity to discuss the main trends in the search for exoplanets.
March 10, 11:30 hr: Dr. Henry LEE
Abstract The Virgo Cluster is one of the nearest laboratories where the effects of the cluster environment (i.e., intracluster medium) can be examined. Owing to their lower gravitational potentials, dwarf galaxies should be very sensitive to alterations in their gas content. Dwarf irregular galaxies (dIs) can be used as test bodies to evaluate their current "gaseous" health with respect to their living conditions. A comparison of the Virgo Cluster sample of dIs with a nearby control dI sample shows that: (1) differential evolution is not strongly manifested in the metallicity-luminosity diagram; (2) a number of Virgo dwarfs are extremely gas-deficient for their oxygen abundance; and (3) these gas-poor dwarfs have likely passed through the intracluster medium in recent times.
March 19, 16:30 hr: Dr. Giovanna TEMPORIN
Abstract The high density and low velocity dispersion that characterize compact galaxy groups (CGs) make interaction-induced galaxy evolution particularly effective in these environments. In particular, especially favoured are merging phenomena and all the related processes, not last the only example of present-day galaxy formation, the so-called tidal dwarf galaxies (TDGs) formed out of interaction debris in tidal tails. CG evolution is thought to lead to the final coalescence into field elliptical galaxies, possibly surrounded by a dwarf galaxy population. I will present recent results about two previously uncatalogued CGs, representing different phases in CG evolution: (1) the low Galactic latitude compact group CG J0247+44.9 encompasses a wide range of activity types and is probably already dynamically old; (2) the soon-to-merge ultracompact group CG J1720-67.8 shows a widespread star formation activity and hosts several candidate TDGs.
March 24, 16:30 hr: Dr. Andre MAEDER
Abstract The physics of stellar rotation was currently not included in massive star models. However, rotation deeply affects evolution by processes of internal mixing, as well as by enhancing mass loss. All the current model outputs are changed:lifetimes, tracks, chemical abundances, WR formation, remnants and yields, etc...
We show that lower metallicity Z models are more affected by rotation, and the question is relevant for Z=0 models. Among highlights, models with rotation allow at last to account for the large number of red supergiants, which contribute to the IR flux of low Z galaxies. The origin of primary Nitrogen is discussed, as well as the N/O and C/O ratios in low Z galaxies and DLA.
March 26, 16:30 hr: Dr. Alfonso ARAGON-SALAMANCA
Abstract In this talk I will review some aspects of what is known about the evolution of elliptical galaxies in rich clusters and present some new results on the evolution of disk galaxies. Using VLT/FORS2 data we have found evidence that Spiral galaxies falling onto rich galaxy clusters transform into S0s when their star formation declines after an initial period of star-formation enhancement.
April 1, 16:30 hr: Dr. Shri KULKARNI
Abstract A few times a day the sky is lit up by brilliant flashes of gamma-rays. We now know that these bursts are located at cosmological distances and perhaps even at the edge of the Universe. These bursts are then the most brilliant astronomical objects. There are good reasons to suspect that the bursts may well be responsible for the highest energy cosmic rays in the Universe and are attractive targets for novel telescopes of the future (gravitational wave interferometers, Terra Electron Volt telescopes and neutrino telescopes). There is evidence that GRBs result from the death of massive stars and perhaps may signal the formation of rapidly spinning black holes.
April 3, 16:30 hr: Dr Andre MAEDER
Abstract There are basically 3 scenarios for the formation of massive stars: 1.- The classical pre-MS evolution at constant mass, (Iben; Ezer & Cameron). 2.- The collision of protostars of intermediate masses (Bonnel, Zinnecker). 3.- The formation by accretion. We discuss their properties and show in particular the many attractive features of the accretion scenario also for massive stars, in relation with the problem of lifetimes and of the occurence of bi-polar outflows.
April 8, 11:30 hr: Dale KOCEVSKI
Abstract The Clusters in the Zone of Avoidance (CIZA) project is producing the first statistically complete catalogue of X-ray selected galaxy clusters behind the Galactic plane. Current optically selected cluster catalogues have excluded a wide band of sky centered on the Milky Way ( | b | < 20° ) due to the high extinction and stellar obscuration at low Galactic latitudes. An X-ray search for cluster candidates overcomes the problems faced by optically selected catalogues, hence providing the first opportunity to explore the sky in the traditional Zone of Avoidance; principally, the Great Attractor region. When added to other X-ray selected cluster surveys such as the BCS and REFLEX, CIZA will complete the first unbiased, all-sky cluster catalogue. I will report on the progress of the CIZA survey as well as preliminary results of a dipole analysis which utilizes the current CIZA sample.
April 14, 16:30 hr: Dr. Rolf CHINI
Abstract First results of a SIMBA survey of southern Bok globules at 1.2 mm are presented. The source selection was concentrated on 80 small objects ( 10') from the Bourke-Hyland-Robinson survey in order to examine single low-mass star-formation events in an isolated environment. The largest objects have a size of less than 0.7 pc at a distance of 500 pc which is not much larger than the typical core size in large dark cloud complexes. The present talk reports on those globules that are associated with IRAS sources. About 50% of the globules have been detected and exhibit a dust emission morphology that ranges from compact unresolved objects to extended and multiple sources. MIR imaging with TIMMI at 10 and 20 microns resolves some of the IRAS sources and gives some insight into the internal structure of the MIR/FIR emission. In comparison with our data and NIR data from the literature we will address the following questions: i) How well does the 10/20 micron ratio constrain the evolutionary stage of a YSO? ii) Is there a relation between the total mass of the globule and the luminosity of the embedded YSOs and/or protostars? iii) Is there evidence for the formation of single stars?
April 16, 16:30 hr: Dr. Gautier MATHYS
Abstract Main-sequence chemically peculiar stars of spectral types A and B, which are characterised by photospheric abundance anomalies resulting from element segregation in the stellar outer layers, rotate slower than normal stars of similar temperatures. The mechanisms by which such slow rotation is achieved are not well understood yet; different processes may be involved for different types of chemical peculiarities, including stellar magnetic fields and multiplicity. Relevant existing observational data are reviewed.
April 21, 11:30 hr: Dr. Bertrand GOLDMAN
Abstract EROS 2 stopped its observations on March 1st of this year, after seven years of continuous presence in La Silla. We studied the Galactic structure by means of the microlensing effect towards the Magellanic Clouds, Galactic bulge and disk, and also made use of our bicolour wide field imager to perform a large proper motion survey for faint, halo objects, both brown dwarfs and old white dwarfs, mostly during the first five years of the project. I will present our results, the constraints that we can put on the contribution of brown and white dwarfs to the Galactic halo, independently of the microlensing constraints. Other proper motion surveys and deep colour surveys have brought information on this question and I will discuss how our results fit with each other.
April 24, 17:00 hr: Dr. Hans ZINNECKER
Abstract In my talk I will address the following open issues in the field of star formation, including the basic motivations and ideas behind them: 1) origin and universality of the IMF 2) origin of massive stars 3) origin of brown dwarfs 4) origin of the Sun and the solar system 5) origin of close binary systems 6) pre-Main Sequence evolutionary tracks 7) origin of protostellar jets 8) solution of the angular momentum problem 9) role of magnetic fields in star formation 10) role of supersonic turbulence 11) role of metallicity and dust-to-gas ratio in star and planet formation 12) formation of globular clusters Some of these topics were debated at the recent star formation conference in Ouro Preto,and I will try to summarize a few conclusions.
April 30, 16:30 hr: Dr. William TOBIN
Abstract L�on Foucault (1819-1868) is best remembered for his eponymous pendulum experiment which in 1851 provided the first dynamical evidence for the rotation of the Earth. However as physicist at the Paris Observatory he also discovered how to make optically-perfect silvered-glass mirrors which enabled him to build reflecting telescopes in essentially their modern form. His largest telescope had an 80-cm mirror which in order to escape Parisian murk was installed under clearer skies in Marseilles. It probably incorporated an early form of active optics and certainly tracked thanks to an improved governor designed by Foucault. A friend made the prescient remark that with Foucault's procedures "one could construct mirrors... as big as the dome of the Panth�on or the Butte Montmartre... one could even make mirrors of several pieces of glass."
May 7, 16:30 hr: Dr. Bruno LEIBUNDGUT
Abstract There is life after WMAP. With the dramatic changes in our picture of the cosmos over the past five years, the questions have changed as well. The new paradigm, often referred to as the 'concordance model,' provides for a universe dominated by dark energy and dark matter. This talk will present the mounting evidence for the accelerated expansion. It will then present the future prospects of supernovae. Contrary to the cosmic microwave background measurements, which provide an integral view of the expansion, the supernovae can actually sample the expansion history for about half the current age of the universe.
May 15, 16:30 hr:Dr. Linda J. TACCONI
Abstract Galaxy merging is a key driving force of galaxy evolution. The most violent mergers in the local universe, and the probable analogs to luminous, high redshift mergers are the ultraluminous infrared galaxies (ULIRGs). In this talk I will present results from our ongoing comprehensive investigation of the dynamical evolution of ULIRGs. From high quality NIR spectra with ISAAC we determine the stellar kinematics of ULIRGs in a wide range of merger state to answer the following questions: 1) Do ULIRG mergers form massive elliptical galaxies? 2) Do ULIRGs evolve into optically bright QSOs? 3) What are the masses and mass ratios of the progenitor galaxies?
May 23, 16:30 hr:Dr. Paul BUTLER
Abstract All one hundred extrasolar planets found to date have been discovered from precision Doppler surveys. The substellar companion mass function derived from these surveys is strongly peaked at less than 3 Jupiter-masses. About 13% of late F and G dwarf stars have easily detectable Jupiter-mass companions within 4 AU, while fewer than 0.5% of these stars have brown dwarf companions within 4 AU. A number of new initiatives are planned over the next 15 years, including ground-based interferomic astrometry at VLT and Keck, the Space Interferometry Mission, GAIA, and TPF/DARWIN, will with the goal detection and analysis of extrasolar planets. All of these missions are distance limited, concentrating on stars within 50 parsecs. As first reconnaissance for these missions we are surveying nearly all Sun-like stars out to 50 parsecs, and most M dwarfs out to 14 parsecs. This program is being carried out using telescopes in the north (Lick 3-m & Keck) and south (AAT 3.9-m & Magellan). With demonstrated long-term measurement precision of 3 m/s, these are the only active surveys capable of detecting 'Solar System' analogs. We are working to improve our measurement precision to 2 m/s. Recent discoveries from our group include all 8 published systems of multiple planets, the only known transit planet, and the five of the six known sub-Saturn mass companions. Solar System analogs, Jupiter and Saturn-like planets orbiting beyond 4 AU, have not yet been discovered. Detecting these elusive planets will require precision of 3 m/s maintained for more than a decade. By 2010 our surveys will provide a first planetary census of nearby stars, allowing us to estimate the ubiquity of planetary systems and of 'Solar System' analogs. The central question is what percentage of Jupiters at 5 AU will be found in circular orbits.
May 26, 11:30 hr:Dr. Marcus NIELBOCK
Abstract Two years ago, a group of motivated young astronomers from the "Public Observatory Recklinghausen" and the "Astronomical Institute of the Ruhr-University Bochum" (Germany) initiated a project to erect an observatory which revives ancient observing techniques with the naked eye. Prehistoric sites like Stonehenge served as an inspiration for the design of this installation. In order to foster public scientific education, this institution will be accessible for everyone to conduct his own naked-eye observations. This "Horizon Observatory" will be placed on a coal mining heap in the Eastern part of the Ruhr region close to Bochum/Dortmund (Germany). With a final height of 160 m, it will be the highest point in that area, and therefore ideally suited to carry out observations close to the mathematical horizon like a) annual change of the rising and setting azimuths of the sun and the moon, and b) earth precession within 10 years. The observer will be located in a lowered terrain, similar to an amphitheatre which is embedded in a circular plateau of 100 m in diameter. High-elevation observations will be supported by large (50 m in diameter) arcs that represent the local celestial equator and meridian. The first funding has been released recently. I will report on the different details of observing possiblities and the current progess of the project.
May 29, 16:30 hr:Dr. Myfanwy BRYCE
Abstract MyCn 18, the Engraved Hourglass Planetary Nebula, is famous as a result of the beautiful WFPC2 image which can be seen everywhere from conference posters to stamps to album covers. In this talk I will begin with an introduction to PNe, taking a brief look at the history of their study and some of the current theories and outstanding questions. I will then look at MyCn 18 and we will see how it fits in with our current understanding, and how it poses questions still to be answered. Finally, I hope to be able to present preliminary results from our infra-red imaging program on the VLT.
June 6, 15:30 hr:Dr. Vera C. RUBIN
Abstract As early as 1784, discussions of dark stars were in the literature, although attempts to evaluate the density of these non-luminous objects were rare before the early part of 20th Century. In the second half of the 20th Century, observations with large optical and radio telescopes and spectrographs led to the conclusion that most of the matter in the universe is dark. I will discuss the early history and the observations that led to this conclusion. I will also mention the curious history of detecting gravitational lenses.
June 18, 16:30 hr: Dr. Remon CORNELISSE
Abstract In most neutron star X-ray binaries the matter accreted on the surface will fuse in an unstable fashion, giving rise to thermonuclear flashes. They are observed in X-rays as short flares and are called X-ray bursts. Recently, a handful of X-ray bursts were observed that lasted two orders of magnitude longer (hours instead of seconds). These superbursts can not be understood in the context of the standard nuclear fusion picture. Hence, it is thought that they probe a new regime of nuclear burning in the deeper layers of the neutron star. I will give an overview of the observations and discuss the model to explain these superbursts.
July 1, 16:00 hr: Andreas LUNDGREN
Abstract M83 is a relatively nearby (4.5 Mpc), barred, grand-design, spiral galaxy which is viewed almost face-on. Color images show clumpy, well-defined spiral arms, evidently rich in young blue stars. It is also fairly symmetrical and has no nearby massive optical companions and no immediate vidence of interaction or outflows. I have mapped this galaxy in molecular lines CO(J=1-0) and CO(J=2-1) using the IRAM receiver on SEST. The map extends 10'x10' and it covers the entire optical disk. From the CO data it is possible to derive how the molecular gas is distributed in the disk. I will compare this distribution to that of HI, radio continuum and star formation tracers (such as e.g. Halpha and ISO-images). I will also present data on how the ratio R_21= CO(J=2-1)/CO(J=1-0) varies over the disk of the galaxy. I have also extracted the velocity field in the disk from the CO molecular line data. The velocity resolution is of the order km/s and it allows investigation of the non-circular velocities. I will also present data on disk stability.
July 3, 16:30 hr: Dr. Annette FERGUSON
Abstract Current galaxy formation theories predict disk formation to proceed from the inside-out, with the outermost regions of disks being the youngest and most metal-poor. I will discuss observational constraints on the nature of the stellar populations and history of star formation in these outermost parts, as derived from HII region abundances, past and present star formation rates and resolved stars. I will also discuss the nature and origin of the stellar `ring-like' feature recently discovered in the outer parts of the Milky Way disk.
July 10, 16:30 hr: Dr. Dave SILVA
Abstract Extensive efforts over the last 20 years to determine mean stellar age and metallicity in nearby ellipticals have been frustrated by the inherent age-metallicity degeneracy in most optical colors and line indices. In principle, near-IR colors and line indices, although harder to determine, are nearly age independent, making them more robust metallicity indicators. To better quantify this assertion, we are measuring JHK color gradients and K-band spectral index gradients in Fornax ellipticals, using SOFI at the ESO NTT 3.5m and ISAAC at the ESO UT1/Antu 8.2m telescopes, respectively. In my talk, I will discuss the context of this problem in greater detail and present our first results on both central index measurements and radial index measurements.
July 16, 16:30 hr: Dr. Paolo TOZZI
Abstract We present a study of the integrated physical properties of ~20 clusters of galaxies with redshift 0.3 z 1.3 observed with Chandra. We derive the Fe abundance in the ICM at the highest redshifts probed to date. Using a combined spectral fit of cluster subsamples in different redshift bins, we investigate the evolution of the mean ICM metallicity with cosmic epoch. We find that the mean Fe abundance at =0.8 is Z = 0.23 +-0.06 Zo, and at = 1.2 is Z = 0.22 +-0.12 Zo, consistent with no evolution with respect to the local value Z ~ 0.30 Zo. These studies can put significant contraints on the past star formation occurred in the cluster galaxies.
July 25, 16:30 hr: Dr. Jacco VAN LOON
Abstract The majority of stars become luminous cool red giants before they end their lives. Their death is accelerated by their prolific mass loss, at rates of up to 10^-4 solar mass a year. This mass loss also makes them important contributors to the chemical evolution of their parent galaxy. The two key physical ingredients in the mass-loss process are stellar pulsation and circumstellar dust formation. I will discuss some evidence for the (in)dependence of these mechanisms on stellar luminosity, temperature, mass and metallicity, and the implications for stellar and galactic evolution.
August 5, 14:30 hr:Dr. Paul L. SCHECHTER
Abstract The 0th, 1st and 2nd derivatives of a "Fermat potential" give the three D's of gravitational lensing: delay, deflection and distortion. Observations of these delays, deflections and distortions make it possible to model the gravitational potentials of the intervening galaxies which produce multiple images of distant quasars. Simple models for lensing potentials that successfully reproduce image positions to high accuracy fail ABYSMALLY in reproducing the flux ratios of the multiple images, suggesting the presence of small scale structure within the lensing galaxies. It has been argued that the flux ratio anomalies observed at radio wavelengths signal the presence of CDM mini-halos. We argue that the yet larger anomalies observed at optical wavelengths can result from microlensing by stars, but ONLY if a substantial fraction of the projected mass is in a smooth, dark component.
August 13, 16:30 hr: Dr. Paolo TOZZI
Abstract The multiwavelength survey of the Chandra Deep Field South has now reached 1Msec of exposure in the X-ray band, showing that the hard X-ray background is resolved at the 80% level mainly by Type II AGNs at redshifts 1. Other minor but interesting contributors have been identified, like high-redshift TypeII quasars, and nearby galaxies with low-level nuclear activity. The spectroscopic follow-up, with 165 redshifts obtained so far, allows us to characterize the large majority of the population of extragalactic X-ray sources and to give a detailed picture of the evolution of AGN over a large range of redshifts.
August 20, 16:30 hr: Dr. Christian HUMMEL
Abstract A little over two weeks ago, I have taken up a position with the VLT Interferometer. In my talk I will review some work I and others have done in the field of long baseline interferometry. I will explain some fundamentals, advantages, limitations, and future challenges for this technique. Astrophysical applications covered by interferometry include stellar diameters, limb-darkening, and pulsations, stellar masses via double-lined spectroscopic binaries and triple systems, gravity darkening of rotating stars, Be-stars, and, with the advent of the VLTI and Keck interferometers, Active Galactic Nuclei.
August 29, 16:30 hr: Dr. Jean-Gabriel CUBY
Abstract In view of the approaching deadline for telescope time application, information about instruments on Paranal (current set as well as freshly arrived ones) will be reported on.
September 4, 11:30 hr: Dr. Paul VREESWIJK
Abstract To date, a handful of DLAs have been detected in GRB afterglows, but most have modest signal-to-noise ratios. Our detection of a DLA in the afterglow of GRB 030323 is unambiguous: its neutral hydrogen column density is log N(HI)=21.90+-0.07 cm^-2, higher than any (GRB- or quasar-) DLA HI column density inferred directly from Lyman alpha in absorption. In the Ly alpha trough, Ly alpha in emission is detected, which corresponds to an unobscured star-formation rate of roughly 1 Msun/yr. We discuss several other properties, such as the host-galaxy extinction, the metallicity, and our strong upper limit on the H2 content, and show that the environment of GRB 030323 consists of a low metallicity gas with a low dust content. Future high-resolution spectroscopy of a large sample of GRB afterglows will be an extremely valuable tool to study the internal properties such as metallicity, dust and H2 content, and kinematics of such dense regions inside GRB host galaxies as a function of redshift.
September 23, 16:30 hr: Dr. Richard de Grijs
Abstract Young, massive star clusters are the most notable and significant end products of violent star-forming episodes triggered by galaxy collisions, mergers, and close encounters. Their contribution to the total luminosity induced by such extreme conditions dominates, by far, the overall energy output due to the gravitationally-induced star formation. The general characteristics of these newly-formed clusters (such as their masses, luminosities, and sizes) suggest that at least a fraction may eventually evolve into equal, or perhaps slightly more massive, counterparts of the abundant old globular cluster systems in the local Universe. Establishing whether or not such an evolutionary connection exists requires our detailed knowledge of not only the physics underlying the evolution of "simple" stellar populations, but also that of cluster disruption in the time-dependent gravitational potentials of interacting galaxies. Initial results seem to indicate that proto-globular clusters do indeed continue to form today, which would support hierarchical galaxy formation scenarios.
September 29, 11:30 hr:Dr. Roberto DE PROPRIS
Abstract The 2dF galaxy redshift survey has provided important constraints on cosmological models and theories of structure formation. The 220000 redshifts and photometric data can also be used to study the evolution of galaxies and environmental effects. We present an analysis of the galaxy luminosity function and star formation rate in different environment and derive a picture of galaxy evolution. A model in which initial conditions dominate galaxy properties appears to be favoured.
October 1, 16:30 hr:Dr. Alessandro PIZZELLA
Abstract Central DM density cuspiness in galaxies is a prediction of CDM cosmological models. Recent results for low surface brightness galaxies (LSB) galaxies , all based on gaseous kinematics, seems to deviate from this prediction but the issue is still open. We present preliminary results of the spectroscopic observations of a sample of 11 LSB. We measured the stellar and gaseous kinematics along their major and minor axes. From the observational point of view, the derived stellar kinematics appears to be much more regular than the ionized gas one and preliminary constant M/L modeling of one object indicates the presence of dark matter at all radii. We are presently working to construct dynamical mass models and derive the DM density radial profiles in the nucleus.
October 7, 16:30 hr:Dr. Holland FORD
Abstract During the talk I will briefly review the performance of ACS, and discuss observations obtained by the ACS Instrument Definition Team. These include deep observations of strongly lensing clusters, clusters at z~1, high-z radio galaxies, and searches for i-band dropouts.
October 14, 16:30 hr:Dr. Emmanuel DARTOIS
Abstract The presence of physisorbed ices covering the refractory interstellar grains in dense regions has been detected more than two decades ago. In the past years, medium resolution spectroscopic surveys in the infrared of the circumstellar dust around young stellar object have allowed to follow the chemical evolution of solid matter surrounding embedded young stellar objects (YSOs). I will present an introduction to the observation of these ices and briefly discuss the various energetic sources importance in the astrophysical context that can lead to their formation (UV, proton irradiation, surface reactions). Besides the grain mantles composition inventory obtained by comparing the solid state features with laboratory data, the analysis of band profiles can trace and highlight the solid structure and molecular interactions taking place in the mantles. I will present two studies of these profiles : The formation of an interstellar intermolecular complex CO$_2$:CH$_3$OH , and the formation of an ammonia hydrate. Finally I will present some aspect of the possible evolution of this organic matter in the laboratory. I will in particular discuss the possibility to follow in the laboratory the organic matter evolution from the elementary molecules found in protostellar environments to the more complex molecules incorporated in protoplanetary systems.
October 15, 11:30 hr:Dr. Chris TINNEY
Abstract The AAO's future is now assured through to at least 2010. Its instrument suite will see United Kingdom, Australian and (through the OPTICON program) EU astronomers positioned to carry out a range of innovative scientific programs using some unique facilities like AAOmega (the successor to 2dF), IRIS2 (an 8' near infrared imager and spectrograph) and UCLES (currently producing the world's most precise velocities for planet searching). I'll review some recent science results, and highlight the prospects for new science now available to European astronomers.
October 23, 16:30 hr: Dr. Boris DIRSCH
Abstract Several giant elliptical galaxies have been studied with wide-field images that encompass all or at least a considerable part of their whole cluster system. In this talk I will present our study of the GCS of NGC 1399 and NGC 4636 for which wide-field photometry in the metal sensitive Washington C and Kron-Cousins R filter combination has been employed. The first galaxy is the central galaxy of the Fornax cluster and latter a giant elliptical at the fringe of the Virgo cluster. The GCSs of both galaxies consist of several subpopulations that can be distinguished by mean color and radial distribution. However, while the red, metal-rich cluster population of NGC 1399 appears to be tightly connected to the field population, this is not true for NGC 4636. We discuss the complex connection between field and cluster populations in these two galaxies. Also the radial distribution of the GCSs at large radii (>9 arcmin) is remarkably different. In NGC 4636 we indeed might have reached the outer rim of the GCS with our observations where its distribution is consistent with a radially truncated power-law (at approximately 50 kpc). In NGC 1399, on the other hand, no indication for any radial limit in the GCS out to 120 kpc has been found. This finding might be explained by the fact that NGC 1399 is located in the center of the cluster dark matter halo. Finally, the results for these two galaxies are put into the larger context of the study of GCS in elliptical galaxies and are compared with a larger sample of galaxies.
October 29, 16:30 hr: Dr. Sebastian ELS
Abstract During the past few years the adaptive optics system NAOMI has been installed and commissioned on the William Herschel Telescope (WHT) located on top of La Palma island. NAOMI has seen several upgrades and environmental improvements bringing this system now into standard operation. The instrumentation feeded by NAOMI covers infrared imaging, integral field spectroscopy as well as coronography for both options. I will describe this instrument suite and review its current status. Also some observational experiences will be presented.
November 3, 16:30 hr:Dr. Antonella VALLENARI
Abstract The study of the kinematics of the stellar population in the Galaxy, together with their age, and age distribution can cast light on the formation process of the Galaxy itself. Recently the availability of databases of photometric data and proper motions as the GSC-II allow the study of large samples of stars. Current issues that might be addressed with those data concern the rotational character of the thick disk and halo; the presence, if any, of a vertical velocity gradient in the thick disk; the existence of a possible retrograde rotating component in the outer halo which might be considered as a relict of the formation process. To address the above issues, a program has been undertaken to analyze space motion and age distribution of stars in the Galaxy Here we discuss a field in the direction of the NGP for which astrometric and photometric data from the GSC-II catalog are available.We derive the scale heights, Star Formation Rate and Initial Mass Function of thin disk, thick disk and halo populations as well as kinematic properties using un updated version of the Padova Galaxy model. No significant velocity gradient in the thick disk is found suggesting a quick heating of the precursor disk. No significant retrograde velocity component is found in the halo.
November 12, 16:30 hr: Dr. Carlos ABAD
Abstract A way of handling and interpreting stellar proper motions, in which the idea of representing them by great circles as proposed by Herschel in 1783, allow us to take the entire celestial sphere as a field of application, making possible the study of dense and extensive stellar zones. Three examples on the power of this new interpretation, making use of stars in the Hipparcos Catalogue, are shown. The procedure combines a variation of the Herschel's Method and a CIDA routine to detect systematic trends in sample data when parallaxes are known.The solar motion and two stellar stream-like motions are obtained from the systematic part of the stars' proper motions. The two stellar motions are on the galactic plane over the radial direction. One of them toward the galactic center and the other one toward the galactic anti-center. Both motions have been detected from two groups of approximately 4600 and 4000 stars respectively in the Hipparcos Catalogue.
Spectral type and luminosity class distributions for each group are not different from those obtained for the totality of the
November 17, 16:30 hr:Dr. Sofia FELTZING
Abstract The formation of disks in galaxies is fundamental to our understanding of how galaxies form and evolve (and to understand the Hubble sequence). By studying the solar neighbourhood stars as a function of kinematics, age, height above the galactic plane etc it is possible to obtain constraints on the various formation scenarios proposed for disk formation (in particular the formation of thick disks). In this talk I will present stellar abundances for a large number of stars with kinematics typical of either the thin or the thick galactic disk. These two kinematically defined stellar samples show distinct trends for many elements, eg oxygen, magnesium, aluminium. We also find the presence of chemical enrichment from SNIa in the thick disk sample. This implies that star formation went on for a rather long (but how long?) time in the thick disk in order for the SNIa rate to be sufficient. The results inferred from the abundances are further supported by studies of the ages of various sub-samples of stars (ie thin and thick disk, but also metal-poor vs solar metallicity stars). We find that the thick disk, at a given metallicity, is older than the thin disk and that it is very likely that the thick disk itself shows an age-metallicity relation. The implications of these results are discussed in terms of formation scenarios for the Milky Way disk system.
November 24, 11:30 hr: Dr. Jose-Maria TORRELLES
Abstract We present VLBA proper motion measurements of water masers toward two YSOs within the same W75N star-forming region. We find that these two objects are very remarkable for having a similar spectral type, being separated by only 0.7" (corresponding to 1400 AU), sharing the same environment, but with a strikingly different outflow ejection geometry. One source has a collimated, jet-like outflow at 2000 AU scale, while the other has a shell outflow at 160 AU scale expanding in multiple directions with respect to a central compact radio continuum source. This result reveals that outflow collimation is not only a consequence of ambient conditions, but something intrinsic to the individual evolution of stars, and brings to light the possibility of isotropic outflows in the earliest stages of YSOs.
November 27, 16:30 hr: Dr. Enrico V. HELD
Abstract The Phoenix dwarf galaxy is the prototype of the ``transition'' dwarf spheroidal/irregular galaxies, showing recent star formation superimposed onto predominantly old stellar populations. Unlike other dwarf spheroidals, this galaxy sits in a distant isolated location in the Local Group of galaxies and has a small cloud of hydrogen very close to it in projection. Radial velocity measurements of a few stars in Phoenix suggest that the gas is indeed associated to the system, but whether it is presently linked to the stellar body of the galaxy or it was lost in the recent past is still unclear. In order to understand the fate of the gas in dwarf spheroidal galaxies, and its role in the evolution of low-mass systems, we have studied the Phoenix dwarf galaxy from different aspects. In this talk, I will report on the first high-precision measurements of star motions in Phoenix obtained with UVES and FLAMES at the ESO VLT. Using these new data, not only have we gained definitive knowledge on the physical association of the H I gas cloud, but also we have got information on the internal dynamics and mass-to-light ratio of this distant, isolated Local Group companion.
December 10, 16:30 hr:Prof. Dainis DRAVINS
Abstract: Since 1868, radial velocities of astronomical objects have been determined from spectroscopy, applying the Doppler principle to displacements of spectral lines. However, recently reached astrometric accuracies permit the precise determination of stellar radial motion from also second-order effects in astrometry, without any use of spectroscopy. A comparison of such "astrometric radial velocities" with spectroscopic data reveals wavelength shifts due to causes other than stellar motion, e.g., gravitational redshifts and shifts due to stellar surface dynamics. Such shifts can be predicted from hydrodynamic model atmospheres and thus absolute lineshifts can be introduced as a novel diagnostic tool for stellar atmospheres, beyond the classical ones of line-strength, -width, -shape, and -asymmetry.
Further discussion: http://www.astro.lu.se/~dainis/HTML/ASTROMET.html