January 8, 16:30 hr: Dr. Andreas JAUNSEN
Abstract The average mass and mass distribution of galaxy halos can in principal be estimated by measuring their weak lensing effects on the background population of galaxies. I present results arguing that this lens signal is detected in a modest sized (13'x13') dataset obtained at the Nordic Optical Telescope (NOT) in multi-colour (UBVRI) centered on the Canada-France Redshift Survey (CFRS) 14-h field. The multi-colour data is used to estimate photometric redshifts for distinguish foreground- and background galaxies in the weak lensing analysis. The correction for systematic effects such as PSF anisotropy and field distortion are also discussed.
January 11, 13:45 hr: Dr. Will VAN BREUGEL
Abstract Distant radio galaxies are beacons for the first forming massive galaxies and black holes. I will discuss the present status of an ongoing search of these systems using near-IR identification and follow-up studies using deep imaging and spectroscopy and sub-mm observations.
January 16, 16:00 hr: Prof. Dr. Ewine F. VAN DISHOECK
Abstract The star-formation process is accompanied by orders of magnitude changes in the physical conditions of the collapsing material. The chemistry responds to these changes by creating different species in the gas and solid-state, part of which will eventually be incorporated into new solar systems. The Infrared Space Observatory (ISO), operational from November 1995 -- April 1998, has provided the first opportunity for spectroscopic observations over the complete 2.4--200 $\mu$m wavelength range above the atmosphere. This wavelength range is very rich in atomic and molecular lines, and a wide variety of phases of star-formation have been probed. In this colloquium, an overview will be presented of the some of the exciting new results obtained with the Short-Wavelength-Spectrometer (SWS), which covers the 2.4--45 $\mu$m range. These include direct observations of the rotational transitions of the dominant interstellar molecule, H$_2$, which are readily detected in warm molecular gas found in photon-dominated regions, shocks, and the envelopes and circumstellar disks around young stellar objects. Other topics include the inventory of interstellar ices, unexpected new features due to crystalline silicates and the wealth of data on gas-phase H$_2$O in a variety of sources. The observations will be discussed in the context of the physical and chemical evolution of low- and high-mass young stellar objects.
January 24, 16:30 hr: Dr. Gian-Luca ISRAEL
Abstract Though the nature of the AXPs is still unknown, after more than 20 years since the discovery of the prototype of this class (1E2259+586), it is clear that these objects represent an important manifestation of the neutron star class. After the presentation of the class, the main properties of the AXPs will be reviewed on the light of the recent multi-wavelength observations and of the several theoretical models proposed so far to explain their origin.
January 25, 11:30 hr: Dr. Oleg KOCHUKHOV
Abstract Main sequence chemically peculiar stars exhibit a variety of phenomena related to the presence of well ordered magnetic fields on their surfaces. These fields are believed to be responsible for creating and supporting abundance patches as well as driving non-radial pulsations in cooler CP stars. I will describe recent advances in the techniques of deducing the relation between magnetic fields, abundance patches and oscillations. In particular I will present new magnetic Doppler imaging code capable of accurate simultaneous and self-consistent reconstruction of vector magnetic field and abundance surface maps using rotational variability of line profiles in Stokes parameters. I will also present new results on the high resolution spectroscopy of rapidly oscillating CP star. These observations open possibility to extract main characteristics of the pulsation mode, thus adding map of the surface velocity fields to the modelling (and subsequent congruent theoretical interpretation) of all stellar surface structures observed in CP stars.
January 31, 16:30 hr: Dr. Dante MINNITI
Abstract I will give a brief tutorial of gravitational microlensing, discussing: History of microlensing, Basic concepts, Photometric and astrometric effects, Resolved sources, Binary lenses and sources, Parallax and xallarap. I will also describe the legacy of the MACHO Project, including: History of the project, The observations and reductions, The MACHO database, Microlensing towards the LMC and SMC, Contrains on the halo Nature of the halo lenses, Microlensing towards the Milky Way bulge, Nature of the lenses towards the bulge, Search for planets, Some special cases. Finally, I will speculate about future prospects.
February 14, 16:30 hr: Dr. Gian-Luigi GRANATO
Abstract I will summarize our spectrophotometric models of galaxies from the UV to the radio region, including dust reprocessing of stellar radiation. I will also anticipate extensions to the X-ray region which are at present under development. Then I will present applications to interpret the observed properties of galaxies locally and at high redshift in different theoretical framework.
February 23, 16:30 hr: Dr. Joao ALVES
Abstract Stars and planets form within dark molecular clouds. However, despite 30 years of study little is understood about the internal structure of these clouds, and consequently about the initial conditions that give rise to star and planet formation. The clouds are primarily composed of molecular hydrogen, which is virtually inaccessible to direct observation. But the clouds also contain dust, which is well mixed with the gas and which has well understood effects on the transmission of light. In this talk I will present sensitive near-infrared measurements of the light from background stars as it is absorbed and scattered by trace amounts of dust to probe the internal structure of the dark cloud Barnard 68 with unprecedented detail. We find the cloud's density structure to be very well described by the equations for a pressure-confined, self-gravitating isothermal sphere that is critically stable according to the Bonnor-Ebert criteria. As a result we can precisely specify the physical conditions inside a dark cloud on the verge of collapse to form a star.
February 28, 16:30 hr: Dr. Gian-Luca ISRAEL
Abstract Over the last three years we carried out several photometric and spectroscopic observations aimed at looking for the optical/IR counterpart of many transient X-ray pulsars either on the Galactic plane and in the MCs. The strategies of the search as well as the results obtained so far (about 10 new counterparts of Be/X-ray binary systems) will be discussed and compared with the already known counterparts (about 20). A number of peculiar cases will be also shown.
March 2, 16:30 hr: Dr. Ezio PIGNATELLI
Abstract I present a self-consistent Jeans model for the stellar and gas kinematics of axisymmetric disc galaxies, adopting the light distribution of bulge and disc derived by means of a parametric photometric decomposition. The model allow to detect the presence of anisotropy in the stellar velocity distribution, to investigate the presence of non-circular gas motion and to infer the mass distribution and mass-to-light ratio of the different components of the galaxy.
Finally, I show the application of the model to the photometry and kinematics of: (a) An S0 galaxy for which kinematics is available along many different axis; (b) Three spiral galaxy with different kinematical behaviour of the gas; (c) An S0 galaxy, possibily hosting a central massive dark object.
March 5, 11:30 hr: Dr. Andrew J. BAKER
Abstract Using the Owens Valley Radio Observatory millimeter array, I have mapped the molecular gas in seven nearby Seyfert and LINER galaxies at 1" (~100 pc) resolution. Each system shows a massive nuclear gas concentration, and most show strong evidence for noncircular or noncoplanar gas motions. I will present detailed kinematic models of three examples-- NGC 1068, NGC 5005, and NGC 7479-- in which warps and/or bars will drive steady or episodic flows of material to smaller radii. I will also discuss the constraints which the systems' unusually high CO(2-1)/CO(1-0) intensity ratios place on their prevailing physical conditions.
March 9, 16:30 hr: Dr. Hans ZINNECKER
Abstract Stellar evolution theory is considered a triumph of astrophysics achieved over the last 5 decades in the old millenium, yet it is incomplete, because we lack a theory of protostellar and pre-Main Sequence evolution. Models exist but they are as yet untested and need to be improved before we can derive masses and ages of young stars from their location in the HR-diagramme. In this lecture, we explain the classical convective-radiative pre-Main Sequence evolutionary tracks (e.g.the Hayashi line, the Henyey track, and the onset of the Main Sequence) in simple terms. We also explain their dependence on various parameters (metallicity, mixing length, rotation, magnetic fields, etc) and describe the possible role of initial conditions (memory effects from protostellar collapse).
We present recent HST/FGS observations where for the first time we managed to spatially resolve the orbit of a young long-period (7 yr) double-lined spectroscopic binary, a weak-line T Tauri system with a semi-major axis of about 30 mas. The combination of the known spectroscopic elements with the resolved orbit enabled us to derive the orbital parallax and allowed us to test pre-Main Sequence tracks in a more stringent and convincing manner than ever before. Comparing the observed dynamical masses with the theoretical model predictions that follow from the observed colors and luminosities of the components we could exclude most of the current model tracks. Only one set of tracks gives acceptable results. All this leads the way into the interferometric future (VLTI, LBTI) when similar high-spatial resolution measurements of double-lined spectroscopic binaries will be the rule rather than the exception.
March 14, 16:30 hr: Dr.Ezio PIGNATELLI
Abstract We present GASPHOT, a tool for automated surface photometry and morphological classification of galaxies in deep and wide fields. For each galaxy in an image, the program retrieve the total magnitude, the half-luminosity radius, the Sersic index n (which is taken as a morphological index), and the flattening b/a. The whole ellipticity, surface brightness and aperture magnitude profiles are also available for visual inspection of the results.
From the tests performed on Hubble Deep Field-like images, for galaxies having a B magnitude ranging from 24 to 27.5, the uncertainties on the photometric parameters derived from GASPHOT are respectively DM =0.02-0.1, Dlg(Re)=0.03, Dn = 0.02-0.5. (so that morphological classification is completely possible up to M=27.5)
March 21, 16:30 hr: Dr.Sebastian WOLF
Abstract For the interpretation of spectra, images, and polarization maps of many astrophysical objects, such as embedded young stellar objects and AGNs, radiative transfer simulations provide the necessary basis. I will present a technique which allows a three-dimensional, self-consistent solution of the radiative transfer problem.
In the first part of the talk, the main concept, features of the radiative transfer code (e.g., polarization, anisotropic scattering by spherical and spheroidal grains), and numerical aspects will be outlined. In the second part, applications, such as the radiative transfer in a circumstellar disk harbouring a proto-planet will be discussed.
March 28, 16:30 hr: Dr.Roberto MAIOLINO
Abstract Most of the Active Galactic Nuclei (AGNs) in the local universe are obscured by a large amount of gas located in their circumnuclear region and various pieces of evidence suggest that at high redshift most of the active nuclei are also heavily obscured. I will review the properties of the medium obscuring these objects by focusing on those features which are peculiar of the circumnuclear gas of these systems, such as the huge gaseous column densities, the anomalous properties of the associated dust, and the geometrical distribution. I will emphasize the effect of these peculiar properties on the appearance of the obscured AGNs at various wavelenghts and, specifically, in the optical, in the X-rays and in the infrared. Within this context I will discuss the implications of these issues on the unified model of AGNs. I will also discuss the long standing issue of the sparseness of obscured AGNs at high luminosities (the "type 2 QSO" problem). Finally, I will review the models which assess the contribution of the obscured AGNs to the X-ray and to the IR cosmic backgrounds, at the light of the constraints discussed above.
April 6, 16:30 hr: Dr. Chris TINNEY
Abstract The AAO's instrumentation developments continue to develop apace, with 4 new instruments being commissioned this year (Prime Focus Upgrade, Wide Field Imager, 6dF and IRIS2) as well as the OzPoz positioner being constructed for VLT.
Developments in the world of brown dwarfs and extra-solar planets are also proceeding with the AAT announcing the detection of the first three planets from its extra-solar planet search (the most precise in the Southern Hemisphere), and photometric periods being detected for rapidly spinning brown dwarfs.
April 12, 16:30 hr: Dr. Chris STERKEN
Abstract The variability of the hypergiant star P Cygni was discovered exactly 400 years ago by a Dutch cartographer. A similar explosive behaviour was seen in Eta Carinae by John Herschel in the middle of the 19th century. Such stars are called S Doradus stars and are massive stars that undergo eruptions and semi-cyclic variations on time scales of decades or centuries.
The lecture starts with a historical introduction covering 400 years of recorded information. Then follows a description of how the speaker got involved in this area of research while embarking on an ESO staff position in 1971, with an overview of the importance of the La Silla-based data collected over the last 30 years.
April 25, 16:30 hr: Dr. Eric PANTIN
Abstract In 1983, the infrared satellite IRAS unexpectedly discovered that a significant fraction of main-sequence stars are surrounded by cold dust geometrically arranged in thin disks; it was the discovery of the so-called "Vega Phenomenon" after one of its members, the Vega system. These disks are probably the denser precursors to our solar system zodiacal disk. The best studied member of this family is the disk around Beta Pictoris, one of the dustyest among this class, which is observationnally favourable because of a combination of distance (20 pc) and orientation (edge-on)factors. These stars are old enough to have had time to form planets which presence may be revealed thanks to the tracks left in the disks through gravitational structuring by resonances. I will review the "Vega phenomenon", and present multi-wavelength observations of Beta pic and of precursors to main-sequence disks around HAEBE stars. Various scenarii proposed to explain the formation of these disks and the possible link to planetary formation will be shown. Finally, I will present the VLT/VISIR mid-infrared instrument for which these disks will constitute a key-program of observations.
May 7, 15:00 hr: Tomohiko SEKIGUCHI
Abstract Transneptunian Objects, Centaurs, comets and asteroids are minor components of our solar system. Nevertheless, they attract the great interests of most planetary scientists since these objects might be (at least, a part of them must be) remnants of pristine objects in the early solar system. On this talk, I will report the main results of my Ph.D work on icy minor bodies in the outer solar system during my stay at ESO: composition and classification studies with VLT+FORS in optical and with Subaru+IRCS in near-IR, size and albedo determinations with 3.6m+TIMMI2 in mid-IR and gas production and activity measurements with NRO45m in millimeter.
May 10, 16:30 hr: Dr. Tim BEDDING
Abstract The amazing success of heliosesimology in probing the inside of the Sun has led to many attempts to do the same for other stars. Solar-like oscillations are excited by convection and we expect a rich set of eigenfrequencies to compare with theoretical models. The difficulty is the tiny amplitudes of the oscillations (maximum 25 cm/s in the Sun). We have used precision Doppler measurements at the AAT and VLT to search for oscillations in solar-type stars. I will describe our recent successes, and also introduce a Danish-led project which involves a small space telescope (MONS) dedicated to asteroseismology.
May 16, 16:30 hr: Dr. Gabriela MALLEN-ORNELAS
Abstract It is known from the luminosity function of field galaxies that there is an increase in the numbers of luminous starforming galaxies at z > 0.5 as compared to z=0. Studies of internal kinematics can help constrain the nature of these "excess" galaxies at z > 0.5 by giving an indication of their dynamical masses. I will present the results of a survey of internal kinematics of galaxies from the Canada-France Redshift Survey, and show evidence that the luminous blue galaxies responsible for the largest changes in the luminosity function are physically small, and have [OII] 3727 velocity widths comparable to those inferred for local Irregular galaxies.
May 17, 16:30 hr: Dr. Yannick MELLIER
Abstract Cosmological weak lensing (or cosmic shear) is produced by cumulative deflections of light rays by large-scale structures of the Universe. Though this is an extremely small effect, statistical properties of weak lensing signal enable to recover typical signatures of Universe models. By using wide field surveys and weak distortion maps one can recover the power spectrum of dark matter fluctuation, the biasing factor as function of angular scale and redshift as well as the cosmological parameters Omega_m and Omega_lambda. During the past year, cosmic shear surveys have revealed for the first time the feasibility of this technique and its fantastic potential for cosmology. In this talk, I will present the first results of cosmic shear and their implications for cosmological scenarios. I will address most technical and cosmological issues in order to show the strength of the method and its future with the next generation of wide field imagers.
May 23, 16:30 hr: Dr. Sara ELLISON
Abstract Damped Lyman Alpha systems (DLAs) are the highest column density absorbers seen in the lines of sight towards high redshift quasars and are believed to represent the progenitors of present day galaxies. Studying the gas content, metallicity and number density of these systems is therefore a powerful probe in the field of galaxy evolution. However, until now, there has been a fundamental limitation to ALL studies of DLAs, namely that they are identified by virtue of absorption against bright, optically selected QSOs. Therefore, there has been great concern that metal rich, dusty DLAs may have been omitted, rendering our current view of high redshift galaxies a highly biased one. Here I present the results from a new survey that has overcome this bias, so that for the first time we can compile a homogenous and unbiased census of high redshift galaxies.
May 28, 11:30 hr: Dr. Luigi GUZZO
Abstract X-ray clusters of galaxies are a powerful tracer of the large-scale structure of the Universe. Their X-ray emission is a direct probe of the depth of their potential wells, and as such their abundance (mean density) and clustering can be directly computed from the models. I will discuss the basis for this and then concentrate on the latest results from the REFLEX survey, which is the largest statistically complete sample of X-ray selected clusters currently available. This sample was selected from the ROSAT All-Sky Survey and includes 452 clusters with measured distances and X-ray luminosities which probe scales as large as 1000/h Mpc. I will elaborate on the first clustering results obtained so far from the REFLEX survey: the power spectrum shows significant clustering power around k~0.01 h/Mpc, strongly indicating a low value for the matted density parameter. At the same time, I will show how the correlation function shows in a beautiful way the consistency of the biasing paradigm, with a shape which perfectly matches a scaled version of the galaxy-galaxy correlation function. Finally, if time permits, I will show some early results from the BMW X-ray cluster survey, a new deep survey which aims at improving our knowledge of the evolution of the cluster abundance out to z~1.
May 31, 16:30 hr: Dr. Anthony BROWN
Abstract I motivate and describe a project aimed at characterising the binary population in the nearby OB Associations. The goal is to obtain an accurate picture of the `primordial' binary population, thus allowing firm constraints to be set on our understanding of the process of star and cluster formation. One component of this project is an adaptive optics survey of all the Hipparcos members of the Scorpio-Centaurus association. The first results from this survey, carried out with ADONIS, will be presented
June 25, 16:30 hr: Prof. D.W. KURTZ
Abstract HR 1217 is a rapidly oscillating Ap (roAp) star with a set of alternating even and odd degree pulsation modes. It is the star that most resembles the sun in its pulsation spectrum, making it the best non-degenerate star on which to apply the techniques of asteroseismology. The presence of a strong, global, approximately dipolar magnetic field, the knowledge that the pulsation modes are oblique to the rotation axis and aligned with the magnetic field, the presence of a strongly abnormal and peculiar atmosphere all make this a star from which a wealth of physical understanding can be extracted. Results will be shown from the November-December 2000 Whole Earth Telescope Extended Coverage Campaign on HR 1217 which provided a successful test of new theories of the interaction of global magnetic fields and pulsation. This talk will introduce Ap stars, the roAp stars, the oblique rotator and oblique pulsator models and radiative diffusion in Ap and other stars. A comparison of roAp star asteroseismic luminosities and HIPPARCOS luminosities, and new spectroscopic results which are providing three-dimensional resolution of pulsation modes will also be shown.
June 26, 15:00 hr: Dr.John HUCHRA
Abstract Cosmology has recently become the search for three numbers, H_0, q_0 and Lambda. Recent observations with HST, including the H_0 Key Project, have helped remove major uncertainties in two of these numbers, and new surveys of galaxies and clusters of galaxies are homing in on the mean mass density of the Universe. Combined, these results are providing a fairly clear view of the age and fate of our Universe.
June 28, 16:30 hr: Dr. David SILVA
Abstract More than half of the VLT observing time is devoted to service observing. Using this time efficiently requires a new approach to building the Long-Term Schedule (LTS), i.e.the schedule of which programmes ESO will try to execute over a 6 month Period. This talk presents a brief overview of current LTS construction concepts, lessons learned so far, and possible future directions. Understanding these concepts will allow VLT Service Mode users to design programmes which have an increased probability of being executed. Plenty of time will be allowed for discussion - audience participation is welcome!
July 5, 16:30 hr: Dr. Jerome RODRIGUEZ
Abstract I will present observations of GRS 1915+105 and GRO J1655-40 taken with the Rossi X ray Timing Experiment, which permit both spectral and temporal studies of the sources. X ray Binaries are well represented by a cold geometrically thick accretion disk (feeding the central compact object) surrounded by a hot coronal medium; the spectra being modeled by a "multicolor blackbody" (kT~0.5 KeV) plus a power law which is thought to represent an inverse compton scattering of the soft photons in the corona. In addition, those sources are known to present Quasi Periodic Oscillations (QPO), which are rapid modulations of the X ray flux, ranging from mHz to few hundred Hz, which power in terms of %rms can be as high as 20%. I will focus here only on the 1-20 Hz QPO often refered as the ubiquitous, and will study in a first part the correlations that exist in both sources between the disk radius and the QPO frequency, and will show that they might be interpreted as the manifestation of the Accretion Ejection Instability (Tagger and Pellat, 1999; Tagger 1999). Then I will turn to other observations of GRS 1915+105 taken on April 2000, and will study how the ubiquitous QPO evolves with the energy, and how this can constrain any modeling of the phenomena.
July 6, 15:30 hr: Dr. Gordon GARMIRE
Abstract We have performed a very deep X-ray survey (~Ms) of the region of the Hubble Deep Field North using the ACIS-I instrument on the Chandra X-ray Observatoty (hereafter Chandra). This is one of the deepest X-ray surveys to date, the other being the Chandra Deep Field South survey (e.g., Tozzi > et al 2001). Near the aim point the limiting fluxes attained are ~3*10e-17 erg cm**-2 s**-1 in the 0.5-2.0 keV band and ~2*10e-16 erg cm**-2 s**-1 in the 2.0-10.0 keV band, fluxes that are ~40 and ~400 times lower than previously achieved by other observatories. At these flux levels a total of 370 X-ray sources have been found in all energy bands. The aggregate spectrum of the sources has a photon index very close to that determined for the X-ray background of -1.4 and the total intensity from the resolved sources is within the range of values measured for the background. The mean luminosity of the sources that have measured redshifts increases by over four orders of magnitude from the local value of ~10e+39 erg/s to 5*10e+43 erg/s at a redshift of 3. The positional accuracy of the sources range from ~0.6" near the aim point to ~2.5" for sources ~10 arc minutes off-axis. At this time ~110 sources have measured redshifts. For these sources, assuming a Hubble constant of 75 km/s/Mpc and a decelaration parameter of 0.1, the luminosities range from 10e+39 erg/s for the nearest sources to 9*10e+43 for a source at a redshift 0.9096. The redshifts range from 0.069 to 5.186. In addition to the 370 point sources detected, two clear examples of diffuse emission are apparent which may be associated with groups of galaxies. Several other weaker regions of extended emission may also be present. Some of the source spectra and the general properties of the X-ray emission from the sources observed in the CDF-N will be discused.
July 11, 16:30 hr: Dr. Valentin IVANOV
Abstract We use the CO band at 2.3 micron to constrain the populations of young stars in the central regions of Seyfert galaxies. We report new CO band spectroscopy of 46 Seyfert galaxies. In most cases, the observed CO indices appear diluted by the presence of a nonstellar component (most likely, warm dust surrounding the active nucleus). We used JHKL aperture photometry to estimate the nonstellar contribution at 2.3 micron. We successfully corrected the CO band for the dilution for 16 galaxies which were not dominated by the nonstellar component. Comparing with CO indices measured in elliptical and purely starbursting galaxies, we find no evidence for strong starbursts in the majority of these galaxies. We assembled a library of over 200 HK band stellar spectra spanning a range of Teff, log g, [Fe/H], and used them to model the total spectra of starburst galaxies. We demonstrated that the MgI absorption feature at 1.50 micron is a good indicator of metallicity of the stellar population, allowing an empirical calibration. This calibration was applied to a set of local starburst galaxies to measure directly, for the first time, the chemical abundances of highly obscured stellar populations.
July 18, 16:30 hr: Dr.Markus SCHOELLER
Abstract The Very Large Telescope (VLT) on Paranal was completed last year when the fourth of the 8-m Unit Telescopes saw first light. Meanwhile, the VLT Interferometer (VLTI) advanced rapidly and first fringes with two siderostats were achieved in March 2001. I describe the status of the VLTI and its subsystems, show first results obtained with the interferometer and discuss the further planning for the different telescopes and instruments.
August 10, 16:30 hr: Dr. Luis BARRERA
Abstract Monturaqui is a meteorite crater with an average diameter of about 370 m. and 30 m. deep. During 1962 the chilean geologist Joaquin Sanchez (Instituto de Investigaciones Geologicas, Santiago, Chile) found the previously undescribed Monturaqui Crater. The Crater located south-west of the "Salar de Atacama" in the II Region of Chile, was discovered by Sanchez using an aerial photographs of the area. During our several visits to the crater we have collected some iron shale pieces on the rim. The analysis of such pieces as well as the analysis of some meteorites found in the last decades in the Atacama Desert will be discussed.
August 14, 16:30 hr: Dr. Michael BURTON
Abstract Photodissociation Regions (PDRs, sometimes known as Photon Dominated Regions) are the surface regions of molecular clouds, where far-UV radiation (ie with wavelength longer than 912A, the hydrogen ionization cut-off) heat the gas and drive the chemistry. Typically the temperature is a few hundred K at the surface and drops in the interior. Heating is generally through the photoelectric effect, electrons ejected from dust grains collisionally exciting the gas, and cooling occurs through a variety of atomic and molecular lines, depending on the depth within the PDR. At the HII region interface the gas is initially neutral (ie predominantly HI) but by an optical depth of unity is mostly molecular. However, in dense PDRs self-shielding of gas can bring the neutral / molecular interface close to the surface (ie optical depths 1) where it can be heated to high temperatures (T > 1000K), allowing the PDR molecular emission to mimic the thermal emission from shocks. The effects of the FUV radiation field extend to optical depths of 4-8, so that in fact the majority of molecular gas in the Galaxy, that outside the dense cores, is in fact PDR. PDRs envelop all regions of star formation, can be rich in organic molecules such as PAHs, and cocoon the forming stars and any UCHII regions around massive protostars. Energy and matter passes through these interface regions as part of the Galactic star formation cycle, and their behaviour is an important element in understanding how the Galactic ecology is self-regulated. This talk will provide an introduction to PDRs and some of the relevant physics.
August 17, 16:30 hr: Dr. Michael BURTON
Abstract The high, dry and tenuous air of the Antarctic plateau provides the best conditions on Earth for observation of the infrared and sub-millimetre part of the spectrum. Thermal background radiation from the atmosphere is reduced, emissivity from aerosols is lowered, and atmospheric windows to observe through opened up. This talk will describe the site testing experiments conducted at the South Pole in order to reach these conclusions, including the AASTO (Automated Astrophysical Site Testing Observatory), as well as the SPIREX/Abu 60-cm prototype thermal infrared telescope. I will finish by discussing plans for locating infrared telescopes at the US Amundsen-Scott South Pole Station and at the French/Italian Concordia Station at Dome C. The talk will be lavishly illustrated with slides of Antarctica.
August 22, 16:30 hr: Dr. Michael BURTON
Abstract Hot Molecular Cores (HMCs) are regions of warm (T~100K), dense (n~10^7 cm-3) gas, rich in saturated and organic molecules. They have been found nearby to UCHII regions, part of the massive star formation process. However there exist earlier stages of star formation than the UCHII region phase, and recent observational evidence suggests that these may be signposted by methanol maser emission. We report on millimetre observations with the Mopra telescope of CH3CN (methyl cyanide), mid-IR observations using the MANIAC camera and sub-mm observations with the JCMT, of isolated methanol maser sites (ie away from any other obvious sign of star formation). Invariably a deeply embedded continuum source is found, and often there is evidence of a hot molecular core, as evidenced through CH3CN mm-lines. We may be witnessing the very earliest stages of massive star formation, as a warming protostellar source begins to evaporate organic molecules from the surface of dust grains, where they formed. These 'hot molecular cores' will be prime sites for future observations using mm-interferometers, and for thermal infrared imaging cameras, in order to determine the evolutionary stages a collapsing cloud goes through to produce a star.
August 24, 11:30 hr: Luca RIZZI
Abstract Dwarf galaxies of the Local Group play a fundamental role in the study of galactic evolution, dark matter, galaxy interactions, stellar populations and inter-stellar medium. They provide a well-studied sample of low-luminosity objects, known to be the dominant (in number) population of the present day Universe. The best candidates for this type of studies are the Milky Way companions, but their large extent(>1 deg diameter) has long prevented a detailed study with usual ccd imagers.With the advent of large format ccd's and, in particular, of mosaic ccd's, it is now possibile to collect images of a significant part of these galaxies with a single exposure, thus allowing a careful investigation of the most elusive features of their stellar population. Our group has started an observative effort to obtain WFI images of a sample of Local Group dwarf galaxies. Up to now, this sample contains Sextans, Leo I, Sculptor, Carina, Fornax and NGC6822. In this talk, I will present the results of the analysis we performed on Sextans. The color-magnitude diagram based on WFI data allowed a clear and first detection of the RGB tip and a metallicity determination by comparison with fiducial globular clusters (which was impossible with the previously published poorly-populated diagrams). I will show our results regarding a number of open questions: 1) the claimed discrepancy between photometric and spectroscopic determinations of the metallicity of this galaxy; 2)the large number of ``blue stragglers'', very high compared to the observed BSS population in Galactic globular clusters. Identification as real BSS is questionable in view of the possible presence of a small population of young stars in Sextans. 3)there is evidence of a second "bump" in the RGB luminosity function above the RGB bump. The nature of this feature is not clear but based on the very high quantity of measured stars, we suggest that we are looking at the very elusive AGB bump.
August 27, 16:30 hr: Dr. Massimo DELLA VALLE
Abstract Nova outbursts are the result of strong thermonuclear runaways on the surface of a white dwarf accreting H-rich material from a low mass sequence star companion. Despite their scientific interest, surveys of novae in extragalactic systems have not been popular among astronomers (although remarkable exceptions do exist....Hubble (1929) Arp (1956), Rosino (1964)....). The major reason for this is probably the unpredictable nature of these events, which make nova surveys considerably (telescope) time consuming. As a consequence, very little is known about the nova populations in extragalactic systems. In particular, almost nothing is known about the properties of nova explosions in different metallicity environments. This is an uncomfortable situation if one wishes to use novae as standard candles aimed at providing a valuable alternative to Cepheids calibrations of the absolute magnitude at maximum of type Ia Supernovae. The recent discovery of five novae in one galaxy in the Fornax cluster (NGC 1316) with only 2.5 hours of observing time, has clearly shown that the VLT + FORS are able to improve the efficiency of nova searches in extragalactic systems by a factor ~ 10, as compared to previous searches. This will help transforming the use of novae as distance indicators from a curiosity to a mature field of research.
September 4, 11:30: Dr. Kate BROOKS
Abstract To conclude with the beautiful series of talks on PDRs by Michael Burton, Kate Brooks will give a short report on the Conference "Early phases of massive star formation", held in Boulder Colorado on August 6-8, 2001. (In the Hot Stars Workshop series, this was #3)
September 6, 11:30:Emanuel GALLIANO
Abstract Results about the distribution and kinematics of the molecular material within 100 pc around the central engine of the Seyfert2 galaxy NGC1068 are reported. Long slit spectroscopic data were obtained using VLT/ISAAC at ESO/Paranal. Molecular and ionized gas were observed simultaneously from the H2 and Brackett gamma emission lines at high spatial (0.5") and spectral (35 km/s) resolutions. An appropriate field coverage allows to reconstruct line emission images in the central 3"x3" (200 pc x 200 pc) region. Spatial distribution and kinematics of the molecular and ionized material are presented, and interpreted in terms of a rotating molecular disk together with a radial outflow.
September 12, 12:00 hr: Dr. Heath JONES
Abstract Tunable imaging filters have been used on 4 m-class telescopes for more than a dozen different science programmes (both stellar and extragalactic) during the past five years. I will show examples of this work and discuss how a tunable filter could be implemeted on the VLT. No such capability currently exists on 8 - 10 m-class telescopes elsewhere. This 15 minute talk was presented at the "Scientific Drivers for Future VLT/VLTI Instrumentation" conference, held at ESO Garching in June.
September 21, 16:00 hr: Pierre COX
Abstract The structural changes occuring in circumstellar envelopes of stars evolving from the AGB to the planetary nebula phase will be the main topic of this colloquium. These changes, as well as the related physical and chemical properties, are described on the basis of recent infrared and millimeter results obtained on well-known sources: the AGB star IRC+10216, the proto-planetary nebulae AFGL~2688 and CRL~618, the young planetary nebula NGC~7027 and the Helix, a fully developed planetary nebula. The changes which the dust grains undergo along this stellar evolution are also discussed. Future (sub)millimeter and infrared facilities (including ALMA) which will open entirely new observational possibilities in the field of evolved stars will be summarized at the end of the presentation.
September 28, 15:30 hr: Dr. Ansgar REINERS
Abstract Stellar differential rotation is believed to be the central ingredient of magnetic dynamo processes. Besides the sun only very few detections of differential rotation were successful because its subtle effects makes necessary either large time series or very good quality data. With the CES/VLC at the 3.6m telescope very high resolution spectra at high S/N ratio are available. The possibility of differential rotation detection using Fourier transforms of absorption line profiles is studied. We find that solar like differential rotation is detectable for stars having a projected rotational velocity of vsini > 5km/s. No calculations of the atmospheric structure are necessary and a recipe to detect differential rotation in Fourier transforms of absorption profiles is presented. The first successful detection using this method was made for the fast rotator psi Cap; solar like differential rotation of alpha = 0.15 +- 0.1 was found. That contradicts the picture that fast rotation implies rigid rotation.
October 4, 11:30 hr: Dr. Pierre COX
Abstract I will summarise the present status of the studies of dust continuum emission and molecular line emission in sources at redshifts greater than 2. In the second part of my talk, I will discuss the expected role of ALMA in the field of observational cosmology.
October 10, 16:30 hr: Dr. Maria-Victoria ALONSO
Abstract A brief review of recent developments in the study of the peculiar velocity field is given. Some recent results are coming from the completed all-sky redshift-distance survey of nearby early-type galaxies (ENEAR). This sample includes all early-type galaxies brighter than B(0)=14.5 mag with radial velocities smaller than 7000 km/s, supplemented by some fainter or more distant galaxies in selected clusters. The database contains photometric and spectroscopic parameters for about 1700 galaxies in a uniform system and is therefore an ideal tool for mapping the local peculiar velocity field. Using these data, measurements of the dipole, the Wiener filter reconstruction and the comparison of the peculiar velocity field with the PSCz gravity field are discussed. These results are in agreement with previous studies favoring low-amplitude bulk flows on scales of 100 h-1 Mpc.
October 18, 16:30 hr: Dr. Guenther WUCHTERL
Abstract The theoretical knowledge about young stars remained separated: on the one hand studies of cloud collapse investigated the early embedded phases of star formation but were unable to predict the stellar properties during the pre-main sequence phase, on the other hand stellar evolution calculations could provide young star properties when the question of star-formation was put aside. I will discuss the history and key elements of the theory of pre-main sequence evolution and show the properties of young stars as they result from calculations of the collapse of simple cloud fragments.
October 23, 16:30 hr: Dr. Matthew SHETRONE
Abstract Until recently only the most rudimentary chemical evolution information (metallicity) has been known for the nearby dwarf spheroidal galaxies (dSph). With the advent of high resolution spectrographs on very large telescopes abundance ratios, [el/Fe], in dSph giants can now be obtained. Abundance ratios from the lowest mass dSph obtained by Shetrone et al. (1998) and Shetrone et al. (2001) suggest a relatively simple chemical evolution, although the [$\alpha$/Fe] ratios are lower than those of the Milky Way halo at a given metallicity. Combined with the radial metallicity gradients a cartoon star formation picture can be presented. The literature abundance information for more massive dSph is too sparse to create even a simple cartoon picture of star formation or chemical evolution. Bonifacio et al. (2000) and Smecker-Hane et al. (1998) find solar and sub-solar [$\alpha$/Fe] ratios in the most metal-rich giants in the massive Sagittarius dSph, but nothing has been reported for the more metal-poor giants. New (yet to be published) VLT abundances spanning a wide range in metallicities in both low and high mass dSphs, and the implications for dSph galaxy formation and Milky Way galaxy formation are presented.
November 2, 16:30 hr: Dr. Doug CURRIE
Abstract Eta Carinae, the most massive and most luminous star in the galaxy, exploded 160 years ago, with energies rivaling a supernova. In the process it formed an expanding nebula (the homunculus), an expanding disk and a series of major �bullets� (NN and NS knots, and the South Bar). In addition it has produced spikes or jets, (i. e., linear strings of small bullets), moving as fast as 1% the speed of light. I shall review the various classes of debris from the recent and earlier eruptions, especially addressing the three-dimensional structure of the expelled material, that is, the homunculus, the bullets and the external debris. However, I will concentrate on the recent work on the spikes. These have a very large length-to-width ratios (up to 600), and have a variety of different morphologies. That is, some are straight, some bent, and some are knotty and others are smooth. I shall review the imaging and spectral astrometry used to determine their dynamical and three-dimensional properties, and briefly address their spectral properties. A review of the currently known properties of the spikes illustrates the great challenge in building theoretical models for the formation and for the propagation of the spikes.
November 7, 16:30 hr:Dr. Ray JAYAWARDHANA
Abstract The discovery of extrasolar planets has renewed interest in exploring the origin, nature and frequency of planetary systems. Since planets form in circumstellar disks out of dust and gas, their properties would depend critically on those of the disks. Thanks to recent technological developments --such as infrared and submillimeter detector arrays and adaptive optics-- we are now able to probe many of the key stages in the planet formation process. In particular, newly identified young stellar groups in the solar neighborhood provide valuable laboratories for testing our ideas about the origin and initial configurations of planetary systems. Disks around many 10 million-year-old stars appear to have central cavities, perhaps carved out by newborn planets. They may represent a missing link between the proto-planetary disks observed around even younger stars and the fully-grown planetary systems orbiting more mature stars. If planets have indeed formed in these disks, it may be possible to directly image them using adaptive optics on large ground-based telescopes.
November 12, 19 and 26, 14:00-18:15 hr:ESO/Chile Staff
Abstract ESO/Chile astronomers talk about the research projects they are carrying on: "THE SCIENCE WE ARE DOING". Each speaker (staff/fellow/PhD student) will have 15 minutes (about 7 view-graphs), to speak about her/his research programs and will then enjoy listening to what her/his ESO/Chile colleagues are working on, as well. The ESO/Chile visiting scientists and our Chilean colleagues in Santiago are most welcome to attend the meetings and discover what we are doing. The meetings will take place in the Large Room in the Vitacura main building, and start at 14:00.
November 14, 16:30 hr:Dr. Mohammad HEYDARI-MALAYERI
Abstract High resolution observations with the Hubble Space Telescope have recently allowed us to resolve and study several very tight clusters of newly born massive stars in the Magellanic Clouds. Situated in an extremely rare category of HII regions (only 5 to 10 arcsecondes across and of high excitation and extinction), these stars are just hatching from their natal molecular clouds. Moreover, since the SMC is the most metal-poor galaxy observable with very high angular resolution, this work provides valuable templates for studying star formation in the very distant metal-poor galaxies which populate the early Universe.
November 21, 16:30 hr: Dr. Guy MONNET
Abstract SAURON is an end to end cooperative (Durham, Leiden, Lyon. ESO) effort to unravel the shape and stellar kinematics of Elliptical galaxies. In total 82 E, L and Sa galaxies are being observed at the WHT with a dedicated integral field spectrograph and the resulting ~150,000 spectra pipeline-reduced to get directly the internal stellar kinematics, the distribution function and abundance variations. About two-third of the sample has now been observed and reduced; strongly triaxal shapes appear as more the norm than the exception. These results will be presented and a few galaxies discussed in detail.
November 22, 11:30 hr:Genevieve PARMENTIER
Abstract We have developed a model of globular cluster (hereafter GC) self-enrichment based on the ability of the GC gaseous progenitors to retain the ejecta of a first generation of Type II Supernovae (hereafter SNeII). The model is able to explain the galactic halo GC metallicities and the Old Halo metallicity gradient. It also implies a trend between the mass and the metallicity of globulars which is indeed observed among the Old Halo subsystem. Finally, we look at the conditions under which the expanding supershell, created by the SNII explosions, can undergo a successful transverse collapse, leading thereby to the formation of the GC stars.
November 28, 16:30 hr:Dr. John WEBB
Abstract Although the extra-solar planets discovered so far are of the giant, gaseous, type, the increased sensitivity of future surveys will result in the discovery of lower mass planets. The detection of O2 in the atmosphere of a rocky extra-solar planet would be a potential indicator of a life. In this talk I discuss calculations which address the specific issue of whether we would be able to detect the O2 A-band absorption feature in the atmosphere of a planet similar to the Earth, if it were in orbit around a nearby star. It seems that a detection may be feasible using existing 8m telescopes but only for host stars with radii up to 0.3 R(Sun) and brighter than V=10. Larger telescopes and/or improved instrumentation efficiency would enable surveys of M stars down to V=13 and greatly improve the chances of discovering life elsewhere.
December 5, 16:30 hr:Dr. John WEBB
Abstract Theories unifying gravity with other interactions suggest there may be spatial and temporal variation of the fundamental "constants" in the Universe. Current interest is high because in superstring theories which have additional spatial dimensions, "compactified" on tiny scales, any cosmological change in the size of the extra dimensions results in changes of the 3-dimensional observed physical constants. Astronomical observations of distant quasars turn out to be a highly sensitive way of investigating this. In particular, a change in the "fine structure constant" could be detected using high precision spectroscopy of distant quasars. I will describe how this is done and show some very recent results which seem to suggest that indeed some variation is seen. If correct, this will inevitably lead to fundamental revision of our understanding of the universe.
December 12, 16:30 hr: Dr. Jeff KENNEY
Abstract The effects of the harsh cluster environment on the evolution of spiral galaxies in the Virgo cluster is examined, using optical R-band and H-alpha images of 100 galaxies in Virgo and a comparison sample of isolated galaxies. Truncated star-forming disks are common in Virgo, and are likely caused by ICM-ISM stripping. Many of these galaxies with truncated H-alpha disks are small bulge systems, yet are misleadingly classified as Sa galaxies, showing that the Hubble classification system for spirals doesn't work in the Virgo cluster. Using optical and VLA HI data, I also discuss examples of peculiar galaxies in Virgo which are victims of a variety of environmental processes, including ICM-ISM stripping, high and low velocity tidal encounters, mergers, and HI accretion. While many Virgo galaxies have significantly reduced star formation rates, some have enhanced rates due to tidal interactions, and in some cases gas accretion. A combination of ICM-ISM interactions and tidal effects appear responsible for the transformation of cluster spirals into lenticulars.
December 19, 16:30 hr: Dr. Meena SAHU
Abstract Variations of the deuterium-to-hydrogen (D/H) ratio on scales of 100 pc are important for two reasons: (1) they complicate the use of deuterium as a cosmological probe, and (2) they imply non-uniform deuterium production/destruction and an inefficient mixing of interstellar gas. The Local Interstellar Medium (LISM) is an ideal location to test whether the D/H abundance ratio varies or not, because the heating sources and radiation fields are well-studied and we have a detailed knowledge of the three-dimensional (3D) structure of the diffuse clouds in the LISM. This detailed knowledge of the number, structure and velocities of the absorbing clouds greatly helps in reducing errors in the derived D/H ratios. I lead a project that aims to obtain high-precision D/H abundance ratios in the interstellar gas within 100 pc. For this purpose, we primarily use HST-STIS data towards nearby hot, white dwarfs (WDs). We have also begun an HST archival research project to study about 20 WD sightlines. In this talk, I will present new HST-STIS observations and the results of our HST archival project.