IAU Symposium 221	UNSW
	Star Formation at High Angular Resolution

Talk Abstracts

IAU00052
OUTFLOW-CIRCUMSTELLAR ENVELOPE INTERACTIONS IN PROTOSTARS
Arce Hector G
California Institute of Technology
We present the results of a high angular resolution (< 5'') survey of protostars with outflows, at different evolutionary stages, using the Owens Valley Radio Observatory Millimeter Array. This survey aims to understand the evolution of the interaction between stellar outflows and the infalling dense circumstellar envelope. Our new data enable us to probe the structure and kinematics of the molecular outflow and the circumstellar envelope, as well as the outflow-envelope interaction at scales of less than 0.02 pc, for every source in our sample. Our results indicate that outflows from the youngest sources are more collimated and more energetic than those of more evolved protostars. The nature of the outflow-envelope interaction also appears to be different at different evolutionary stages. For example, outflow-envelope interactions are more dramatic and easier to detect for younger protostars, as their more powerful outflows are able to entrain the dense envelope gas to high velocities. In addition, the wide outflow lobes of the more evolved sources constrain the infalling material to a limited volume around the protostar. Our study shows how the resolving power of millimeter interferometers is crucial in order to understand the mass assembling process in nascent stars.

IAU00086
ADAPTIVE OPTICS IN SF
Brandner Wolfgang
Max-Planck-Institut fŸr Astronomie
Over the past ten years, the concept of adaptive optics has evolved from early experimental stages to a standard observing tool now available at almost all major optical and near-infrared telescope facilities. Adaptive optics will also be essential in exploiting the full potential of the large optical/infrared nterferometers currently under construction. Both observations with high-angular resolution and at high contrast, and with a high point source sensitivity are facilitated by adaptive optics. Among the areas which benefit most from the use of adaptive optics are studies of the circumstellar environment (envelopes, disks, outflows), substellar companions and multiple systems, and dense young stellar populations. In this talks I'll highlight some of the recent advances in star formation studies facilitated by adaptive optics, and give a brief tutorial on optimized observing and data reduction strategies.

IAU00196
HERBIG AE/BE STAR DISKS AT HIGH ANGULAR RESOLUTION
Dullemond Cornelis P
Max Planck Institut fuer Astrophysik, Garching
Herbig Ae/Be stars are ideal objects for testing theoretical models of protostellar disks. Due to their high stellar luminosity their disks are predicted to have an inner hole devoid of dust. The dusty part of the disk therefore has a bright puffed-up inner rim emitting at near-infrared and mid-infrared wavelengths. This striking geometry, predicted from first principles, can be well observed using near- and mid-infrared interferometry. The inner rim, appearing as an ellipse or half-ellipse on the sky, has a diameter of about 1 AU. For typical nearby Herbig Ae/Be stars (d=100-150 pc) this can be fully resolved in the K band, and partially resolved in the N band on baselines between 10 and 200 meters. We present typical signatures expected from these models, and various other aspects of 2-D axisymmetric disk models that can be tested using infrared interferometry. Dominik Carsten , Van boekel Roy , Natta Antonella , Waters Rens

IAU00728
CHEMICAL SIGNATURES OF THE EVOLUTIONARY STATE OF CORES
Aikawa Yuri
Dept. of Earth and Planetary Sciences, Kobe University
Recent observations with high angular resolution revealed chemical fractionation in several prestellar cores; while N2H+ emission peaks at the core center, CO and CCS emission peaks are offset from the center. Molecular abundances also vary among cores; some cores have high CCS abundance and low N2H+ abundance, but others have less CCS and more N2H+. Numerical calculations of a chemical-reaction network in collapsing cores show that these fractionations and variations can be diagnostics of physical evolution of cores, because molecular abundances and distributions are determined by the balance between the dynamical and chemical timescales. In prestellar cores, low temperature and increasing density cause adsorption of molecules onto grains. Depletion timescale varies with species; early-phase species deplete first, because of destruction via gas-phase reactions in addition to the adsorption. N2H+ is the last to deplete because of the low adsorption energy of its parent molecule N2 and depletion of main reactants such as CO. Molecular D/H ratio is another probe of core evolution, since it increases as the adsorption proceeds. When a central star is born, it heats the envelope and desorbs the grain-surface species accumulated in the prestellar stage. The reset chemical network can be diagnostics of protostellar core evolution.

IAU00776
OBSERVING MASSIVE STAR FORMATION - THE STORY OF G5.89-0.39
Feldt Markus
Max Planck Institute for Astronomy
The formation of massive stars M > 8Msun is a major open problem in stellar astrophysics. In contrast to the formation of low--mass stars, the time scales for these objects are so short, they reach the zero-age main sequence (ZAMS) while still being embedded in their natal molecular clouds. Testing the various suggested models explaining their formation mechanisms requires observational access at very high resolution and sensitivity to these generally far away, deeply embedded, and complex objects. Historically, observations were first carried out at MIR and cm wavelengths and targeted the ultracompact HII regions accompanying the young massive stars, where hot dust and the free-free emission of ionized gas is visible in spite of very high optical depths, and interferometers provide sufficient spatial resolution. During the last decade, adaptive optics systems (AO) enhanced the spatial resolution available to NIR observers to levels comparable to or even better than that of radio interferometers. I will present the history of the peculiar object G5.89-0.39 from the first detections by IRAS and the VLA, the progress made and the mis-interpretations suffered with each new gain in resolution, to the very latest detection of its central object by ESO's new AO system NACO. Henning Thomas , Stecklum Bringfried , Puga Elena

IAU00809
ADAPTIVE OPTICS IMAGING OF CIRCUMSTELLAR DISKS
Apai Daniel
Max Planck Institute for Astronomy, Heidelberg
Circumstellar material - often in the form of disks - accompanies young stars. The evolution of circumstellar disks and envelopes is intimately bounded to the formation of planetary systems, one of the most exciting questions of astronomy. To probe the structure of the circumstellar material around several young stars, we carried out high resolution, high constrast near-infrared imaging using the adaptive optics systems NACO and ALFA. To enhance the contrast PSF-subtraction and polarimetric differential imaging technique were applied. We detect scattered light and trace back the extended emission, sometimes as close as ~10 AU to the stars. Our observations represent the first results from polarimetric differential imaging with NACO and demonstrate its capability to observe faint emission 5 times closer to the stars than previous HST studies. Pascucci Ilaria , Brandner Wolfgang , Wang Hongchi , Henning Thomas

IAU01023
WATCHING THE FORMATION OF SUPER STAR CLUSTERS
Turner Jean L
UCLA
Subarcsecond radio and infrared images show that star formation in starburst galaxies is often remarkably spatially confined, apparently dominated by the formation of super star clusters. How do such large clusters form? High spatial and spectral resolution spectroscopy can shed light on the dynamical processes in the nebulae surrounding these embedded young SSCs. Early results indicate that the large masses of these clusters may have significant effects on their evolution and that of the surrounding gas, and that the star formation in these clusters is extraordinarily efficient. We present high resolution VLA Pietown and OVRO CO images and Brackett line echelle spectra of gas around several ÒsupernebulaeÓ, including those in NGC5253 and IIZw40.Beck Sara C

IAU01172
MASSIVE STAR FORMATION AT HIGH ANGULAR RESOLUTION
Garay Guido
Universidad de Chile
The understanding of the formation process of massive stars requires a detailed knowledge of the physical conditions of the cloud environment which is thought to play a critical role in determining the formation mechanism. In this contribution I review recent results concerning the physical characteristics of the environment prior to and after the formation of massive stars. Particular emphasis is given to high angular resolution observations of molecular line emission in high density tracers, dust continuum emission, and radio continuum emission, which are providing key evidence concerning the physical processes that take place during the formation and early evolution of massive stars. Briefly summarized is the current status of theoretical models.

IAU01184
TESTING THE PARADIGM FOR LOW MASS STAR FORMATION
Hartmann Lee
Smithsonian Astrophysical Observatory
The standard model of low-mass staf formation invokes the slow contraction of a molecular cloud core until sufficient magnetic flux has diffused outward that rapid gravitational collapse can ensue. Recent bservational and theoretical studies strongly suggest that cloud core and star formation does not follow this scenario but is rapid and dynamic at all stages. I shall review these new results, show how the older equilibrium models can be used to derive physical insight but not detailed constraints, and indicate the implications of the new paradigm for the stellar initial mass function

IAU01213
THEORIES OF STAR FORMATION
Shu Frank H
National Tsing Hua University
I will review current problems in the formation of sunlike stars, especially those aspects which require the use of high-resolution observations to discriminate against competing theories and ideas. I will focus on contemporary issues concerning protoplanetary disks: their accretion flows onto and interactions with a central, possibly strongly magnetized, star; the winds and jets that might be driven magnetocentrifugally from their surfaces; the mechanisms by which planetesimals and planets might form in them; and the gravitational interactions between the disks and embedded or external bodies. A general conclusion is that the processes of star and planet formation are much more dynamic and violent than they were generally thought to be two decades ago.

IAU01216
THE TRANSITION FROM COLLAPSING ENVELOPE TO ROTATING DISK
Hogerheijde Michiel R
Steward Observatory
Many low mass young stars have circumstellar disks out of which we think planetary systems may form. These disks result from the angular momentum present in the parental molecular cloud core. I will review our understanding of the angular momentum distribution in cloud cores, and continue on to sketch how rotationally supported structures arise from the collapsing material. I will briefly discuss theoretical results and present detailed observations on a number of objects that illustrate the transition from collapsing envelope to rotating disk. These include decoupling of the collapsing and rotating envelope around IRAM 04191+1522 from its surrounding cloud; an accretion shock around the disk of L1157; and a contracting disk around L1489 IRS. High-angular resolution observations at millimeter an mid-infrared wavelengths are key in our understanding of these sources. An important question I will attempt to answer is how angular momentum determines the mass and size of a disk -- and hence the disk's planet-forming potential. I will conclude with a summary of lessons learned and a roadmap for further work including upcoming observational facilities.

IAU01252
THE FORMATION OF MASSIVE STARS VIA ACCRETION
Yorke Harold w. W
Jet Propulsion Laboratory / Caltech
The collapse of massive molecular clumps can produce high mass stars, but the evolution is not simply a scaled-up version of low mass star formation. Radiative effects strongly influence the evolution. A necessary condition for accretion growth of a hydrostatic object up to and in excess of 20 solar masses (rather than coalescence of optically thick objects) is the formation of and accretion through a circumstellar disk. The massive central hydrostatic objects themselves do not follow pre-main sequence tracks but rather quickly evolve to hydrogen-burning central densities and temperatures even as they accrete material. The circumstellar disks will be photoevaporated on a timescale of ~100,000 yr and be observed as highly obscured Ultra Compact HII regions. This places strong constraints on the accretion rate necessary to produce high mass stars and offers an opportunity to test the accretion hypothesis.

IAU01314
MASERS - HIGH RESOLUTION PROBES OF MASSIVE STAR FORMATION
Ellingsen Simon
University of Tasmania
Astrophysical masers are one of the most readily detected signposts of high-mass star formation. Their presence indicates special coinditions, probably indicative of a specific evolutionary phase. Masers also represent the ultimate high-resolution probe of star formation with the potential to reveal information on the kinematics and physical conditions within the region at milliarcsecond resolution. To date this potential has largely remained unfulfilled, however, recent advances suggest that this will soon change. The key to unlocking the potential of masers lies in identifying where they fit within the star formation jigsaw puzzle. I will review recent high resolution observations of OH, water and methanol maser transitions and what they reveal. I will also discuss how multi-transition observations of OH and methanol masers are being used to constrain maser pumping models and through this estimate the physical conditions in the masing region.

IAU01320
INFRARED STUDIES OF PROTOSTELLAR BINARIES
Greene Thomas P
NASA's Ames Research Center
Much progress has been made in studying the multiplicity properties of pre-main-sequence T Tauri stars over the past decade. Near-infrared speckle imaging, lunar occultation, and recent adaptive optics observations have yielded much information about the binary fractions and distributions of separations of multiple systems in several nearby star forming regions. The binary fractions of these young stars are generally found to be several times higher than the field population in the local solar neighborhood, so it appears that multiplicity properties change as stars evolve. It is important to determine the multiplicity characteristics of even younger, more embedded protostars (with Class I and flat-spectrum spectral energy distributions). Analyzing the differences between these objects and pre-main sequence stars can provide further clues to the star / planet formation process, including the evolution of angular momentum, coevality of components, and the frequency of ejections or disintegrations during protostellar phases. Some recent infrared imaging and spectroscopic observations of protostars are examined. Among other results, these studies indicate that protostars have multiplicity characteristics which are similar to T Tauri stars, suggesting that disintegration of multiple protostellar systems is not common.

IAU01364
X-RAYS FROM CLASS 0/I PROTOSTARS
Tsuboi Yohko
Department of Science and Engineering, Chuo University
In the last decade, our interest moved significantly to the youngest phase, ``protostars''. Protostars are often embedded deeply in star forming clouds, shrouded by dense circumstellar gas and dust and hence generally invisible in the optical, near infrared and even soft X-ray bands. The breakthrough was achieved in hard X-ray wavelength. Using the high transparency of the band, hard X-ray emissions from a few Class I sources in Rho Oph region were discovered with ASCA in 1994, and then the successive observations with ASCA and ROSAT further revealed that some other Class I protostars are X-ray emitters. However, not having enough spatial resolution nor sensitivity, previous X-ray satellites did not resolve the large percentage of protostars deep inside crowded cloud cores. Chandra, with the superior spatial resolution and sensitivity, enabled us to peer such obscured region and we now have a new tool to examine the youngest phase in protostars, which have been impossible to gain access to in any other wavelength. In this talk, I will review the most recent results on Class I and 0 sources with Chandra.

IAU01380
MAGNETIC FIELDS IN STAR FORMATION
Goodman Alyssa A
Harvard University
This talk will assess the role of magnetic fields in the star formation process on scales from 100 pc to a few A.U. On the largest scales, comparisons of molecular spectral-line mapping and simulations show that molecular clouds are well-represented by a magnetized turbulent flow, but the magnetic energy in the flow may be less than the kinetic energy. On smaller scales, magnetic fields apparently play a key role in the energetics and collimation of outflows from young stars. Questions about how the smaller scale fields, associated with individual star-disk systems, originate and connect to larger fields, and what role fields play at intermediate scales (~0.1 pc, e.g. dense cores) remain unanswered and will be highlighted in the talk. The talk will conclude with a discussion of the future of magnetic field observations and simulations, focusing on what can be done with interferometers and faster computers.

IAU01392
HIGH ANGULAR RESOLUTION STUDIES OF DISKS-- THE MM
Wilner David J
Harvard-Smithsonian Center for Astrophysics
I will review recent high angular resolution millimeter-wave studies of disks around young stars. In this wavelength regime, interferometry at several facilities allows for imaging observations at Solar System size scales (70 AU) in nearby dark clouds, in some cases reaching to Jovian orbit size scales (5 AU). I will focus on results obtained from observations of thermal dust continuum emission, including (1) direct determinations of disk structure that take advantage of the fact that millimeter emission is almost entirely optically thin and can be directly related to mass, and (2) indications of grain growth, an important step toward the formation of planets, as inferred from spectral index measurements that reveal the wavelength dependence of the dust opacity.

IAU01393
STUDYING STAR FORMATION WITH THE KECK INTERFEROMETER
Akeson Rachel
Michelson Science Center
The Keck Interferometer utilizes the two 10-meter Keck telescopes as a direct detection interferometer in the infrared. The 85-meter baseline produces a fringe spacing of 5 milliarcseconds at 2 microns, resulting in spatial resolution of 0.7 AU for sources in the Taurus star forming region. I will present the first results from the Keck Interferometer on observations of young stellar objects. The Keck Interferometer is a joint effort of the Jet Propulsion Laboratory, the W.M. Keck Observatory and the Michelson Science Center, Caltech and is funded by the National Aeronautics and Space Administration.

IAU01433
SUBARU AO CORONAGRAPHIC AND DIRECT IMAGING OF YSOS
Tamura Motohide
National Astronomical Observatory of Japan
Near-IR high resolution images of T Tauri stars and Herbig Ae/Be stars have been obtained with the Subaru 8.2m Telescope and the IR coronagraph, CIAO, combined with the adaptive optics (AO). The resolution of these images is about 0.1 arcsec. Because of usage of small occulting masks (down to 0.4 arcsec), the circumstellar structure and companions in the close vicinity of the central bright YSOs can be studied. Several projects have been conducted with this Subaru/CIAO, which include IR coronagraph surveys of low-mass YSOs in nearby dark clouds, IR coronagraph surveys of Herbig Ae/Be stars, and IR imaging polarimetry of YSOs. In this presentation, we will describe the instrument, report the status of these projects, emphasizing the results of HL Tau and MWC 137. Hayashi Masahiko , Itoh Yoichi , Fukagawa Misato

IAU01537
OBSERVATIONS OF BINARY PROTOSTELLAR SYSTEMS
Launhardt Ralf
Max-Planck-Institute for Astronomy
A major gap in our understanding of star formation concerns the origins of binary stars, although there is growing evidence that the majority of stars form in binary and multiple systems. While some theoretical predictions of fragmentation models are indirectly supported by statistical studies of evolved binary systems at shorter wavelenghts, direct observations of the formation phase itself became only possible with the advance of large and sensitive millimeter interferometers. I will show how molecular line spectroscopy and dust continuum observations at high angular (sub-arcsecond) resolution can address some of the key questions in star formation theories and provide an observational link between the initial properties of a molecular cloud core and the outcome of a star formation event. I will review recent studies of binary protostellar systems and work out which constraints these observations put on current binary formation models. I will also show how the particular conditions in binary protostellar cores and our current observing techniques put serious limitations on our efforts to study the gas kinemtics in such sytems. Despite our recent successes in studying and understanding binary star formation, only the next-generation interferometers will allow a more systematic approach to this problem. Sargent Anneila , Zinnecker Hans

IAU01538
HOT MOLECULAR CORES
van der Tak Floris
Max-Planck-Institut fuer Radioastronomie
In hot molecular cores, evaporation of ice mantles off dust grains is followed by complex gas-phase chemistry. Objects may qualify as hot cores either by their physical properties (mass, temperature) or their chemistry (molecular abundances). The heating source of hot cores is radiation from high-mass stars at early stages of formation, although shocks may also contribute to their chemistry, not all hot cores may contain high-mass stars, and low-mass objects may go though a hot core phase too. The lifetime of the hot core phase has been estimated from submillimeter observations and from chemical models. Hot cores are usually surrounded by cooler envelopes, a good description of which is critical for interpreting their spectra.

IAU01539
HIGH RESOLUTION X-RAY STUDIES OF STARFORMATION IN GALAXIES
Ward Martin J
Dept. of Physics, University of Leicester, UK
X-rays have not tranditionally been a frequency regime associated with high resolution imaging. However, this situation has now changed dramatically with the advent of the Chandra Observatory, and its ability to provide sub-arcsecond images. Regions of starformation in other galaxies, have been imaged with Chandra over the energy band 0.5-10keV. For example, spectacular results have been obtained for the Antenna interacting system, M83 and M51. We are undertaking a Chandra study of the X-ray populations in a sample of nearby spirals, and have detected large numbers of high/low mass binaries, as well as SNRs. In the course of studying the local galactic environment of the X-ray sources optically and in the near infrared, we have discovered some highly ionised nebulae, stellar superclusters and possibly individual stellar counterparts. X-rays provide a unique time sequence insight into starformation past and present, ranging from its fossil record via low mass binaries, to current energetic starformation via high mass binaries, X-ray bright SNRs/possible hypernovae, and superwind outflows. I will report on recent progress in understanding the starforming properties and history of spiral and starburst galaxies, by means of their X-ray populations. Roberts Timothy P, Kilgard Roy , Prestwich Andrea H, Zezas Andreas , Jenkins Leigh

IAU01552
CLOUD FORMATION AND CONTROL OF STAR FORMATION EFFICIENCY
Vazquez-Semadeni Enrique C
Instituto de Astronomia, UNAM, Morelia
Recent observational and numerical work suggest a holistic scenario in which molecular cloud formation,
the inherent turbulence to all molecular clouds, the efficiency of star formation, and the destruction of the cloud are all parts of the same process, which involves the accumulation of gas from the diffuse medium, either via dynamical compressions or various kinds of instabilities, which trigger the internal turbulence of the clouds via dynamical instabilities, and persists for the duration of the accumulation process. The internal turbulence thus generated has the dual role of contributing to the support of the cloud as a whole, while producing local compressions which can induce localized collapse sites. The small- scale compressions have only a small probability of becoming gravitationally bound, naturally causing a low efficiency of star formation. Finally, the remainder of the gas, that is not incorporated into the local collapsing sites, acquires a lower density and column density, becoming easier to disperse both because of its reduced self-gravity (assuming the collapsed objects do not form a contracted cluster) and its poorer shielding against dissociating radiation. We present numerical experiments supporting various stages of the scanario, and simulations of the global process. Ballesteros-Paredes Javier , Klessen Ralf S, Gazol Adriana , Burkert Andreas

IAU01562
DETECTING PLANETS WITHIN DISKS
Wolf Sebastian
California Institute of Technology
Observations, theoretical investigations and laboratory experiments strongly support the model of planet formation in circumstellar disks. Besides the discovery of numerous planets around stars with little or no detected circumstellar dust, there exist several further indications, such as the dust grain growth in young, T Tauri-like circumstellar disks and characteristic spatial dust density distributions in some debris disks which are in agreement with the existing picture of planet evolutionary scenarios. So far, the period between the earliest and the final stage of planetary evolution is subject of profound theoretical predictions but little observational constraints. However, new observing techniques that will be available in the near future will allow to investigate the link between submillimeter grains and planets. In particular, interferometric observations will provide the necessary basis to verify the existence of protoplanets in circumstellar disks.

IAU01605
MOLECULAR GAS AND STAR FORMATION IN NEARBY GALAXIES
Wong Tony
CSIRO ATNF
I review current knowledge of the molecular gas distributions in nearby galaxies, with special emphasis on the information provided by millimetre arrays. Observations indicate a close association between the presence of molecular gas and star formation, but quantitative comparison is difficult because of uncertainties in the CO-to-H_2 conversion factor and the susceptibility of most star formation indicators to dust. Nonetheless, it appears that star formation on large scales is largely determined by the amount of molecular gas available, which in turn is related to the HI content and the interstellar pressure. On smaller scales, as in the LMC, evidence for triggered star formation is also seen. An important objective for high resolution imaging is to identify the progenitors of young compact star clusters.

IAU01629
THE VARIATION OF THE IMF IN CLUSTERS
Luhman Kevin L
Smithsonian Astrophysical Observatory
I present measurements of the initial mass function of stars and brown dwarfs in star-forming clusters and use data to test theoretical predictions for the formation of these objects.

IAU01668
OPTICAL/IR INTERFEROMETRY: STAR FORMATION AT SUB-AU SCALES
Tuthill Peter G
Sydney University
Intermediate to late stages of star formation are characterized by rising infrared and visible luminosities, with much of the most interesting physics concentrated in the inner regions within the immediate vicinity of the central protostar(s). Long-baseline optical and infrared interferometry is ideally suited to study of such bright, compact structures. Contributions from presently operational arrays, which are capable of resolving the brightest few dozen, will be reviewed. These results presage the potential for further dramatic advances in our understanding of star formation with observations from more advanced instruments now being built.

IAU01739
PROBING AU-SCALE STRUCTURE USING SPECTRO-ASTROMETRY
Takami Michihiro
Department of Physical Sciences, University of Hertfordshire
The circumstellar environment within 10 AU of young stars is of particular interest for studies of star and planet formation. In this region, the star accretes the material from the circumstellar disk, and drives an energetic jet/wind. In the circumstellar disk, planets may be growing and tidally interacting with the circumstellar environment. In a significant number of objects, this region also contains a stellar companion. The population, mass distribution, and orbital parameters of these companions could give useful constraints on the understanding of binary formation. However, even the Hubble Space Telescope or adaptive optics on 10-m telescopes cannot resolve this scale in the nearest star-forming regions. To obtain spatial information at such high resolutions, we use the technique of ``spectro-astrometry''. By use of a standard long-slit spectrograph, the seeing position relative to the continuum is measured in emission/absorption features with an extremely high accuracy (~1 mas). We have proved that this method is capable of discovering pre-main sequence binaries, determining kinematics of outflows and providing evidence for gaps in circumstellar disks --- all down to AU scales. In the symposium, we summarise our progress to date, and present some recent results obtained at the SUBARU 8.2-m telescope. Bailey Jeremy , Chrysostomou Antonio , Tamura Motohide , Terada Hiroshi

IAU01806
STAR FORMATION AT HIGH ANGULAR RESOLUTION SUMMARY & OUTLOOK
Zinnecker Hans
Astrophysikalisches Institut Potsdam
I will attempt to summarise the highlights of the IAU Symposium 221: what we have learnt so far from high spatial resolution radio and infrared observations of star formation and what the interferometric future has in store. The successes and prospects of the new generation of numerical simulations (SPH etc) will also be discussed.

IAU01838
A PLANETARY ORIGIN FOR THE GAP IN GM AURIGAE'S DISC
Rice William K
University of St Andrews
The spectral energy distribution (SED) of the classical T Tauri star GM Aurigae provides evidence for the presence of an inner disc hole extending to several au. We combine hydrodynamical simulations and Monte Carlo radiative transport to investigate if the observed SED is consistent with the inner hole being created and maintained by an orbiting planet. We find that an ~ 2 Jupiter mass planet, orbiting at 2.5 au, produces a disc profile with an SED that matches both the SED observations and the CO observations which constrain the velocity field in the disc. A range of planet masses is allowed by the current data, but this could in principle be constrained with further observations between 3 and ~ 20 microns. Future high precision astrometric instruments should also be able to detect the motion of the central star due to an orbiting Jupiter mass planet. The small number of T Tauri stars with SEDs resembling that of GM Aur is broadly consistent with the expected statistics of embedded migrating planets. Wood Kenneth , Armitage Philip J, Whitney Barbara A, Bjorkman Jon E

IAU01599
FIRST RESULTS FROM ATCA AT MILLIMETRE WAVELENGTHS
Vincent Minier
UNSW
The newly upgraded Australia Telescope Compact Array (ATCA) at millimetre wavelengths is the first millimetre interferometer to be built in the Southern Hemisphere. The full array will be operational in 2004 and will provide arcsec angular resolution at 3 mm and 12 mm. This will be a unique instrument to study at high angular resolution the interstellar chemistry and more generally the star formation process, especially in the bulk of the galactic plane and in the Magellanic Clouds. The upgraded ATCA will also be an excellent tool to detect dust emission from nearby protoplanetary disks. In this paper, I will present the first results from the upgraded ATCA at 3 mm and 12 mm. The result review will cover the topics of massive star formation and hot molecular cores, dust emission from star-forming regions and detection of protoplanetary disks.

IAU01877
EARLY RESULTS FROM THE SMA
Zhang Qizhou
Harvard-Smithsonian Center for Astrophysics
The Submillimeter Array (SMA) is a collaborative project of the Smithsonian Astrophysical Observatory (SAO) and the Academia Sinica Institute of Astronomy & Astrophysics of Taiwan (ASIAA). The SMA in its full capability will operate at 230, 345, 490, 690 GHz and 850 GHz, with 2 GHz bandwidth and 8 antennas. Provisions to include the JCMT and CSO instruments as additional elements of the Array are underway. As of this writing (2003/02/28), five antennas have been fully deployed at the summit, Mauna Kea, equipped with 230 and 345 GHz receivers, and a correlator bandwidth of 656 MHz. In addition, four 690 GHz receivers are installed. Scientific programs are being undertaken as an integral part of the commissioning process of the SMA. Seven science projects are selected, ranging from studying solar system objects to galaxies. In this talk, I will present the up-to-date status of the Array, the results from scientific programs with an emphasis on star formation, and the future prospect of the Array.

IAU01917
A HIGH-RESOLUTION SEARCH FOR DISKS AROUND MASSIVE YSOS
Gibb Andy G
University of Maryland
We have used the BIMA millimetre array to observe a sample of massive young stellar objects at 2.7 and 1.4 mm. Our angular resolution varies from about 3 arcsec to as high as 0.7 arcsec, corresponding to scales of 3000 to 700 AU at a distance of 1 kpc. We find that the majority of our sources, the 2.7-mm continuum emission on scales of order 1 arcsec or less is dominated by emission from the stellar wind, contributing 30 to 50 per cent of the total flux. However, it is clear that dust is indeed present around these massive YSOs. Combining these results with the 1.4-mm data suggests that typically of order a few (3 to 10) solar masses of dust and gas surround these massive YSOs on scales of a few thousand AU. These mass estimates are similar to or lower than the central stellar mass. In our sample, NGC7538-IRS1 shows the strongest dust emission at 1.4 mm, and GL490 may be resolved. We also show for the first time that the radio source Cep A is not the dominant source of dust emission in that core. Hoare Melvin G, Wyrowski Friedrich , Mundy Lee G

IAU01932
STAR-FORMING REGIONS: X-RAY MICROSCOPY
Montmerle Thierry
Laboratoire d'Astrophysique de Grenoble
With subarcsecond imaging capability in X-rays, Chandra rivals ground-based telescopes to observe the sky. Star-forming regions have been known to be associated with X-ray emission for nearly three decades, in terms of active stellar sources, both massive and low-mass. High angular resolution X-ray studies of star forming regions with Chandra are however original in that, in addition to resolving the "classical" problem of source confusion, it brings a definitive answer to the old problem of the nature of the extended X-ray emission in giant HII regions. This "X-ray microscopy" reveals hundreds of low-mass stars, and a truly diffuse, 10^7 K component likely due to stellar winds from massive stars, challenging the traditional approach to the structure and evolution of HII regions.

IAU01940
INTERMEDIATE MASS STAR FORMATION
Testi Leonardo
INAF - Osservatorio Astrofisico di Arcetri
I will discuss our current understanding of the formation mechanisms and evolution of the circumstellar material around intermediate mass stars. I will review the evidence for and properties of circumstellar disks around Herbig Ae stars, as well as recent observational evidence for dust evolution within these disks. The status of the search for the more elusive disks around Herbig Be stars will also be discussed. Finally I will review the clustering properties of young stars around Herbig Ae/Be stars, and the possible link between clusters and the formation of the more massive stars.

IAU01995
THE EMBEDDED POPULATION IN HMPO CORES
De Buizer James M
Gemini Observatory
A high-mass proto-stellar object (HMPO) is considered to be a proto-star in the earliest observable stage of formation with a mass greater than about 8 solar masses. Young stars this massive are eventually capable of producing copious amounts of UV flux that will ionize the gas around them and form ultracompact HII (UCHII) regions that are detectable via free-free radio continuum emission. The HMPO phase precedes even this youthful UCHII phase, but because massive stars form in dense clusters, HMPOs typically form very close to other stars with UCHII regions. Thus high-resolution observations are needed to resolve HMPOs from other young nearby sources. Furthermore, a massive star in the HMPO stage of formation is highly embedded in its natal envelope, and thus obscured. Consequently, besides not having radio continuum emission, no radiation less than about 2 microns in wavelength can escape from a HMPO. Therefore, we are very limited in wavelength coverage when observing these sources. I will summarize the properties and observations of HMPOs and discuss how high angular resolution observations in this limited spectral window, especially in the mid-infrared, can be used to learn more about this little known and earliest phase of massive stellar birth.

IAU02042
THE MOST DETAILED PICTURE YET OF AN EMBEDDED HIGH-MASS YSO
Greenhill Lincoln J
Harvard-Smithsonian Center for Astrophysics
The formation of massive stars via accretion faces a fundamental problem: radiation pressure from the forming star must be overcome for accretion to proceed. A unique clue to the solution of this problem is provided by observations of Orion BN/KL. Radio Source-I therein is believed to have a luminosity of a few tens of thousands of solar luminosities, but it is undetected even at infrared wavelengths because it is deeply embedded. Source-I is interesting because it is nearby and it excites maser emission from vibrationally excited SiO at radii of 20 to 100 AU, ground state SiO at radii of about 200 AU, and water at radii of about 500 AU. We have mapped this emission with a spatial resolution as fine as 0.1 AU, thus tracing the dense molecular structures around Source-I and detecting pr oper motions that provide 3-D space velocities. This work has provided the most detailed picture yet of an embedded high-mass YSO and its immediate surroundings. The ultimate goal of this work is creation of a movie that shows the bulk mass motions within 20 AU of a high-mass YSO with resolution of about 1 km/s, over about half of a dynamical crossing time. Chandler Claire J, Reid Mark J, Diamond Philip J, Moran James M

IAU02078
TECHNIQUES OF MM/SUB-MM INTERFEROMETRY IN STAR FORMATION
Sargent Anneila I
California Institute of Technology
In astronomy, unexpected discoveries and insights often result when new instruments become operational, when new wavelengths become accessible to observation, or when new measuring techniques are introduced. Over the last few decades, increased observing capabilities at infrared and millimeter wavelengths have enabled us to penetrate the veils of dust that hide much of the universe from optical view. It has become possible to make observational studies of the processes involved in the birth of stars deep in clouds of obscuring dust and gas. In particular, mm-wave interferometers are filling in the details with high resolution images of the molecular gas and dust continuum radiation in star-forming clouds. Results from current arrays will be presented to demonstrate the importance of interferometers for improving our understanding of how stars and planetary systems form. Advances to be expected from future mm and sub-arrays and from those now coming on line will also be discussed briefly.

IAU02113
INFALL IN PROTOSTELLAR ENVELOPES
Ohashi Nagayoshi
Academia Sinica Institute of Astronomy & Astrophysics
It is widely accepted that stars form by accretion of matter caused by the dynamical collapse of molecular envelopes in the central parts of molecular cloud cores. Dynamical infall plays an essential role in the course of star formation, and it is therefore very important for us to understand physical properties of the dynamical infall in detail. The ability of interferometers to image with a high angular resolution helps us to observe infall in detail. In particular, interferometers can resolve the kinematic structure of molecular envelopes, which enables us to distinguish infall from rotation or outflow, motions sometimes confused with single-dish observations. Interferometric observations have demonstrated that infalling envelopes tend to be characterized by elongated, flattened structures having kinematics explained by dynamical infall and slow rotation. I will review recent observations of infalling envelopes using mm and sub-mm interferometers.

IAU02145
CORONAGRAPHIC OBSERVATIONS OF OPTICALLY THIN DEBRIS DISKS
Clampin Mark
NASA Goddard Space flight Center
We present the first observations of the debris disks around HD141569A and HD100546 made with the Advanced Camera for Surveys (ACS) Coronagraph. Both HD141569A and HD100546 are known to possess circumstellar disks with complex structures. HD141569A's disk was shown to exhibit a a gap from NICMOS observations (Weinberger et al. 1999), while HD100546 has been shown to exhibit a disk with spiral strucure (Grady et al. 2001). The ACS observations were made as part of the GTO program to study the formation of planetary systems. The performance of the ACS Coronagraph meets pre-launch expectations, and allows us to achieve images with both unparalleled contrast and, a fully-sampled point spread function. We will present new, multi-color images of each object obtained with the F435W, F606W and F814W filters. These images present a significant improvement over the previous observations with NICMOS and STIS. We fully resolve the complex spiral structures observed within these disks and determine the true angular extent of the disks. Disk properties including color variations, disk asymmetries and morphology are determined. We discuss the formation history of these disks in the light of our new observations and review the evidence for the possibility that the systems harbor planets. Krist John , Ardila David , Golimowski David A, Ford Holland C, Illingworth Garth D, ACS IDT

IAU02165
EXTRAGALACTIC STAR FORMATION REVEALED
Eva Schinnerer
National Radio Astronomy Observatory
In this review presentation, I will present an overview of how multi-wavelength high-resolution observations have advanced our knowledge of obscured star formation in galaxies both in the nearby universe and at
high redshift. The focus will be on recent results of star forming complexes in a variety of environments, such as galaxy centers, the dusty regions of starbursts, and luminous mergers. These findings will be related to the starburst phenomena observed at high redshift. The emphasis will be on how high resolution observations at especially IR and (sub-)mm wavelengths have helped to reveal sites of star formation in these sources that could not be observed otherwise.

IAU02167
MOLECULAR CLOUDS TO PROTOSTELLAR CORES
Saito Masao
National Astronomical Observatory of Japan
High resolution imaging is key to understanding the evolution of cores into protostellar envelopes and studying their detailed structure and kinematics. The initial condition of star formation such as density structure of dense cores can be derived from high resolution continuum images at millimeter/submillimeter wavelengths. The chemical composition of dense cores enables us to figure out their stage of evolution. Some starless cores show evidence of infal followed by ignition of a star in the center. Eventually, the central star becomes prominent over surrounding infalling dense envelope as in the case of NGC1333 IRAS 4, which shows an inverse P Cygni profile. Furthermore, magnetic fields play an important role in star formation, such as formation of a disk-like envelope and driving jets. The direction of the magnetic field in a core or protostellar envelope can be studied by polarimetric mm/submm continuum observations. Most low-mass stars are formed in clusters although the study of protoclusters is still rudimentary because of lack of observations with sufficiently high resolution to resolve individual cores/envelopes. High resolution observations with the coming SMA and ALMA will be crucial to testing and improving theoretical models of low-mass star formation.

IAU02179
KINEMATICS OF PROTOCLUSTERS
Di Francesco James
National Research Council of Canada
In the last several years, compelling evidence has accrued that suggest the bulk of star formation in the Galaxy occurs within clusters embedded deeply within molecular clouds (Lada & Lada 2003). A satisfactory theoretical framework for star formation within clusters, however, remains elusive, in part due to a lack of observational constraints. For example, the environments out of which clusters are forming are best probed by millimeter line or continuum observations, but these data can have poor resolutions relative to optical or IR data. As a result, it can be difficult to associate the observed motions or derived physical conditions to specific objects in crowded cluster fields. Current interferometer arrays, however, can improve dramatically resolutions at millimeter wavelengths, yielding far more detailed data of cluster forming environments. We present here the results of recent wide-field interferometer observations of clusters in the nearby Serpens, Perseus, and Ophiuchus molecular clouds. We compare the kinematics of gas associated with specific cluster members and the groups themselves to the predictions of recent cluster formation models.

IAU02180
T TAURI MULTIPLE SYSTEMS
Brandeker Alexis
Stockholm Observatory
New high-resolution adaptive optics systems provide an unprecedented detailed view of nearby star forming regions. In particular, young nearby T Tauri stars can be probed at much smaller physical scales (a few AU) than possible just a decade ago (several tens of AU). Resolving potential companions at this resolution has several implications that I will discuss in this talk, among them the possibility to determine an accurate dynamical mass of the system as well as placing it correctly in the H-R diagram, two key parameters in star formation theories. Furthermore, I will discuss benefits and pitfalls of post-processing techniques, and shortly review recent results from adaptive optics imaging of nearby T Tauri systems.

IAU02237
MODELLING OF JETS AND OUTFLOWS FROM YSOS
Shang Hsien
Institute of Astronomy and Astrophysics, Academia Sinica, Taiwan
We have constructed the foundations to a series of theoretical diagnostic methods to probe the jet phenomenon in young stars as observed at various optical forbidden lines and radio wavelengths. We calculate and model in a self-consistent manner the physical and radiative processes which arise within an inner disk-wind driven magnetocentrifugally from the circumstellar accretion disk of a young sun-like star. Comparing with real data taken at high angular resolution, our approach will provide the basis of systematic diagnostics for jets and their related young stellar objects, to attest the emission mechanisms of such phenomena. This work can help bring first-principle theoretical predictions to confront actual multi-wavelength observations, and will bridge the link between many very sophiscated numerical simulations and observational data. Analysis methods discussed here are immediately applicable to new high-resolution data obtained with HST, Adaptic Optics, and radio interferometry.

IAU02298
HIGH ANGULAR RESOLUTION IR IMAGING OF YOUNG STELLAR DISKS
Padgett Deborah L
California Institute of Technology
In recent years, the Hubble Space Telescope (HST) and groundbased adaptive optics (AO) systems have resolved the optical and near-infrared scattered light from nearly twenty young circumstellar disks, each of which have a radial size larger than the Kuiper Belt of our solar system. Around the youngest stars, researchers have discovered a small, but growing, number of disks oriented edge-on to our line of sight, occulting the direct light of the central star. When imaged at subarcsecond resolution, these edge-on disks offer unique insight into the vertical structure of young stellar disks. High resolution multiwavelength imaging of color gradients in protoplanetary disks when combined with accurate model density distributions hold the promise of constraining disk dust properties. Resolved infrared disk images also have revealed internal disk structures, some of which might plausibly arise from the dynamical influences of unseen substellar companions interior to the disks.A handful of disks have also been imaged in the mid-IR, resolving disk emission first detected photometrically by IRAS. Ultra-high resolution near-infrared interferometry of accretion disks has begun to place limits on structures within the innermost 1 AU of young accretion disks. I will review these recent studies and discuss future disk imaging techniques. Stapelfeldt Karl R

IAU02299
DISK AND PLANET IMAGING WITH NULLING INTERFEROMETRY
Kuchner Marc J
Smithsonian Astrophysical Observatory
Nulling interferometers can collect light from circumstellar material while blocking contaminating light from the central star. This technique promises to detect super-faint debris disks, hot jupiters, and one day extrasolar Earth-like planets. I'll outline how a nulling interferometer works, suggest what a star-formation wonk might do with one, and tell you where to find one in the near future.

IAU02301
HIGH RESOLUTION OBSERVATIONS OF HERBIG-HARO JETS
Reipurth Bo
Institute for Astronomy, University of Hawaii
Herbig-Haro flows are astrophysical laboratories for the analysis of shock structures, of hydrodynamics in collimated flows, and of their interaction with the surrounding environment. The structure and evolution of highly collimated HH jets are discussed based on multi-epoch Hubble Space Telescope and groundbased adaptive optics observations through interference filters. Analysis of highly collimated HH jets provide indirect but important insights into the nature of the accretion and mass loss processes which govern the formation of stars. The recognition that HH flows may attain parsec scale dimensions opens the possibility to partially reconstruct the mass ejection history of the newly born driving sources and therefore their mass accretion history. Such an analysis leads to an interpretation of HH flows in terms of the formation and orbital evolution of binary stars.

IAU02348
OBSERVATIONS OF THE CHEMISTRY IN DISKS
Dutrey Anne
LAOG
Since the 90's, new observational facilities have allowed us to image protoplanetary disks surrounding TTauri and Herbig Ae stars located in nearby star-forming regions. In particular, mm arrays can routinely provide images with angular resolution of 150 AU or 1'' at the Taurus distance. 12CO and 13CO J=1-0 and J=2-1 mappings of disks not only reveal that these objects are in Keplerian rotation but also allow us to derive physical parameters such as the temperature, density or turbulence in outer disks (R > 30-50 AU). Observing optically thinner molecular lines is however sensitivity limited to the more abundant molecules encountered in cold molecular clouds. Hence, our knowledge of the disk chemistry is still poor. In this talk, I will review first the physical properties of disks as derived from CO interferometric maps, in particular, I will show how the vertical kinetic temperature gradient can be estimated from CO interferometric maps. Then, I will present recent advances in observations of chemistry in disks at mm waves.

IAU02423
STAR FORMATION WITH FUTURE MM- AND RADIO-INTERFEROMETERS
Knee Lewis
Herzberg Institute of Astrophysics
The Atacama Large Millimetre Array (ALMA) and the Square Kilometre Array (SKA) will be the two largest and most capable aperture synthesis facilities of the next few decades. The advances in our knowledge of star formation that ALMA will permit are well known to the participants of IAU Symposium 221, but the potential of the SKA has so far attracted less attention. I will contrast the capabilities of ALMA and the SKA in order to highlight the complementary roles they can play in high angular resolution studies of star formation. Areas of star formation research in which the SKA will excel include searches for non-thermal radio emission from embedded young stellar objects, detailed study of thermal emission from jets, and high resolution surveys of HII regions and compact HII regions in our own and other galaxies. The SKA may be very useful in determining magnetic field strengths in dense molecular cores through Zeeman splitting of centimetre wave molecular lines. The very densest cores and disks may be optically thick at millimetre wavelengths: the SKA may be needed in order to probe into these regions.

IAU02448
MODELS OF ACCRETION DISKS AROUND YOUNG STARS
D'Alessio Paola
Instituto de Astronomia Universidad Nacional Autonoma de Mexico
We present models of alpha-accretion disks irradiated by low mass central stars, considering parameters corresponding to Classical T Tauri Stars. These are self-consistent physical models, calculated for different dust grain abundances and size distributions. We find that the fraction of stellar radiation absorbed and scattered by the disk depends on the optical properties, sizes and dust to gas mass ratio of the grains at the disk atmosphere. On the other hand, the emission for $\lambda >$ 1 mm depends on the properties of grains closer to the disk midplane. We illustrate how spectral energy distributions and high angular resolution images in a wide range of wavelengths can be used to study quantitatively the growth of dust and the settling of the bigger grains towards midplane in disks.

IAU02464
STRUCTURE OF COLD CORES
Ward-Thompson Derek
Cardiff University
Cold molecular cloud cores are important as the sites of star formation. Starless cores are molecular cloud cores that do not contain any sign of protostellar activity, such as infrared sources or bipolar outflows. Pre-stellar cores are the most centrally condensed starless cores and are believed to represent the stage of star formation that precedes the formation of a protostar. Consequently, they represent the initial conditions of star formation. Furthermore, recent evidence appears to show that the stellar IMF is actually determined at the pre-stellar core stage. If that is the case, then we need to understand the physics of these cores. The physical parameters of the cores, such as density and temperature, are discussed. The detailed structure of bright cores can be mapped. Radial flux density profiles typically show flattened inner regions and sharp boundaries. These have recently been compared to Bonnor-Ebert (B-E) spheres. Hence it has been deduced that the cores are in approximate equilibrium. However, two recent papers have questioned this interpretation. One shows the results of modelling highly turbulent non-equilibrium cores and showing that they can appear to emulate B-E spheres. The other takes data of one core and shows that the radial profile is consistent with several different forms of profile including Plummer spheres, power-laws and B-E profiles. This seems to indicate that radial profiles alone do not uniquely define core structure. A combination of polarimetry data and turbulent MHD modelling indicate that both magnetic fields and turbulence are important in the evolution of cores. Other recent data suggest that cores collapse to form protostars only after turbulence has dissipated, but that they do not collapse from the inside out.
Kirk Jason, Andre Philippe

IAU02474
VLTI - EARLY RESULTS
Leinert Christoph
Max-Plack-Insitut fŸr Astronomie
VLTI - the infrared interferometer at the VLT - is approaching operation as part of the scientific instrumentation of the VLTI. First fringes with test siderostats and with the test instrument VINCI were seen in the K band already on March 17, 2001, followed by successful pairwise beam combination between the 8 m VLT telescopes and by a round of scientific observations with those 40 cm diameter siderostats. O fhte two first- generation interferometric instruments, the 10 micron instrument MIDI has seen first fringes on December 15, 2002 and now is being commissioned for regular observations. The near-infrared instrument AMBER is scheduled to see first fringes and have commissioning later this year. - The talk will describe typical contributions expected from the VLTI for the field of young star formation and exoplaets, as well as the very first observational results.

IAU02479
THEORY OF YOUNG CLUSTERS
Bate Matthew
University of Exeter
I review recent theoretical work on the formation of stellar clusters with the aim of highlighting theoretical predictions that can be tested by observations at high angular resolution. Results will be presented from high-resolution numerical simulations of star clusters and predictions made about stellar properties, including multiplicity and the sizes of circumstellar discs. I will also discuss how these properties and the stellar initial mass function are expected to vary in different star-forming environments.

IAU02482
EARLY DISK EVOLUTION
Wardle Mark
Macquarie University
Protostellar disks are complex objects. A vast range of dynamical processes have been proposed to play a role in disk evolution -- convection, magnetic or non-magnetic turbulence, gravitational instabilities, disk-driven winds and X-winds, and layered accretion to name just a few examples. This rich world of possibility is further complicated by the coupling between dynamics and chemistry. Chemistry determines which species are available as coolants, what spectral lines are available to be observed, and the ionisation level which determines when and how magnetic fields play a significant role. The situation is further muddled by uncertainties in the evolution and agglomeration of dust grains within the disk. Finally, the range of dynamical time scales within a disk precludes global, steady models of their evolution. In this talk I review the processes that may play a role in disk dynamics and outline the implications of different scenarios for the evolution of protostellar disks. I will discuss modelling and observations that would test these ideas and illuminate early disk evolution.

IAU02489
MILLIMETER INTERFEROMETRY OF MASSIVE STAR FORMATION CORES
Henrik Beuther
Istituto di Fisica dello Spazio Interplanetario - CNR
Because high-mass stars form in a clustered mode and are on average relatively far away (a few kpc) high angular resolution is essential to disentangle the different phenomena taking place simultaneously. Furthermore, massive star-forming cores are strongly emitting in the (sub-)mm regime, which makes (sub-)mm interferometry the ideal tool to investigate the physical processes taking place in detail. This talk will focus on interferometric studies of massive molecular outflows and their implications on high-mass star formation. Additionally, I will present very recent SMA observations outlining the great capabilities of simultaneous observations of many molecular lines with the (sub-)mm bands..

IAU02491
OBSERVATIONS OF STAR FORMATION
Lada Elizabeth A
Department of Astronomy, The Univerisity of Florida
Star formation is a continuous, ongoing process, occurring over the lifetime of our Galaxy and the universe. However understanding how stars form from their prenatal clouds of gas and dust remains a mystery. During the last two decades, we have made remarkable progress toward unraveling this mystery, mainly due to advances in observational technology, especially at infrared and millimeter wavelengths, which allow direct observation of the sites of star birth. Such observations suggest that embedded clusters may be the fundamental units of star formation in molecular clouds. Low star formation efficiency and rapid gas dispersal make these clusters disperse to provide the field star population. Consequently, embedded clusters provide important laboratories for investigating fundamental issues of star formation such as the formation and early evolution of molecular clouds, binary stars, circumstellar disks, planets and the stellar initial mass function. In this talk, I will review the role that observations of embedded clusters play in understanding the general process of star formation. The promise of high angular resolution observations for advancing our understanding of stellar origins will be discussed.

IAU02492
MILLIMETER-INTERFEROMETRY STUDIES OF JETS AND OUTFLOWS
Gueth Frederic
IRAM (Institut de Radio Astronomie Millimetrique)
During the last years, centimeter and especially millimeter interferometry has proven to be a powerful tool to study the jets and outflows that are created by the youngest embedded protostars. The VLA and the current generation of millimeter-wave interferometers (IRAM, OVRO, BIMA, NMA) provide angular resolutions that allows us to disentangle these complex objects and investigate the properties of the protostellar envelopes, jets, outflows, and shocks. I will shortly review the main recent observational results and their consequences on our understanding of the outflow formation and evolution. The physical and chemical properties of the strong interaction taking place between the outflows and the interstellar medium will also be presented. Finally, the evolution of the outflows properties with the mass of the central exciting source will be discussed.

STAR FORMATION WITH FUTURE OPTICAL/IR TELESCOPES
Hillenbrand Lynne

This talk will summarize how some of the most pressing questions in the field of star and planet formation
will be addressed by the high angular resolution capabilities available in space and ground technology, in the optical and infrared, currently being planned for the 2005-2020 time frame

Is the Magnetic Field Preserved During Core Fragmentation?
Brenda C Matthews
Observational evidence exists which suggests that magnetic fields are capable of providing support to molecular clouds, thereby impeding their collapse long enough for fragmentation to occur. But is the field of the star-forming cloud preserved in the cores, and if not, how quickly does a core become distinct? Recent observations of the Barnard 1 cloud in Perseus from SCUBA at the James Clerk Maxwell Telescope (JCMT) reveal that each core exhibits a different mean magnetic field direction which in all cases but one is distinct from the field of the ambient cloud. On the contrary, observations in Orion using the JCMT and high-resolution polarimetry from the Berkeley-Illinois-Maryland Association (BIMA) interferometer reveal a core which has apparently preserved the magnetic field of the parent filamentary cloud to very small scales. We will discuss the implications of these data in terms of the ambipolar diffusion rate of low-mass cores and the strength of the core magnetic field as inferred from the dispersion of the polarization data.

Modelling of Jets and Outflows from YSOs
Hsien Shang
Institute of Astronomy and Astrophysics, Academia Sinica, Taiwan
We have constructed the foundations to a series of theoretical diagnostic methods to probe the jet phenomenon in young stars as observed at various optical forbidden lines and radio wavelengths. We calculate and model in a self-consistent manner the physical and radiative processes which arise within an inner disk-wind driven magnetocentrifugally from the circumstellar accretion disk of a young sun-like star. Comparing with real data taken at high angular resolution, our approach will provide the basis of systematic diagnostics for jets and their related young stellar objects, to attest the emission mechanisms of such phenomena. This work can help bring first-principle theoretical predictions to confront actual multi-wavelength observations, and will bridge the link between many very sophisticated numerical simulations and observational data. Analysis methods discussed here are immediately applicable to new high-resolution data obtained with HST, Adaptic Optics, and radio interferometry.

UNSW | School of Physics | Department of Astrophysics and Optics | Astronomy in Antarctica
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