Young Local Universe
La Thuile, 21-28 March 2004


Lise DEHARVENG or Annie ZAVAGNO Laboratoire d'Astrophysique de Marseille, or
ORAL Title:
Sequential formation of massive stars or clusters at the periphery of HII regions
to be sent later on
ORAL Title:
X-ray irradiation effects on molecular clouds
Jonathan BRAINE Observatoire de Bordeaux,
Oral Title:
Tidal Dwarf Galaxies: Todays (very) Young Galaxies
Tidal Dwarf Galaxies (TDGs) are the galaxies being formed today. They form from the contraction of gas and stars tidally ejected from the outer parts of spiral disks. Our recent observations of the molecular gas in TDGs, published and unpublished, show that the H2 forms from the condensation of the atomic gas (H2), apparently without needing Dark Matter. The star formation observed then proceeds naturally from the molecular gas and with an efficiency (traced by the Halpha/CO ratio) equivalent to what is observed in spiral galaxies! In the proposed ORAL presentation, we present both new and recent results and discuss the formation and evolution of these objects, including some new observations of molecular gas in the outer parts of spiral galaxies, which is what TDGs form from.
Jose M. DIEGO UPenn,
Oral Title:
The Hybrid power spectrum
We present a new approach to combine several observables into a new derived quantity the hybrid power spectrum which is less sensitive to the cosmoloical model than to the intracluster physics. This makes the hybrid power spectrum an interesting tool to study the evolution of the physics in the plasma as a function of redshift. Our approach will be useful with data from X-ray and SZ surveys.
Martino ROMANIELLO European Southern Observatory,
Oral Title:
Low-mass Star Formation at Low Metallicity
The processes at play during star formation determine much of the appearance of the visible Universe. Yet, our theoretical understanding of the processes that lead from diffuse molecular clouds to stars is still very tentative, as many complex physical phenomena simultaneously concur in producing the final results. From an observational standpoint, most of the effort has traditionally been devoted to nearby Galactic star-forming regions, such as theTaurus-Auriga complex, Orion, etc. If this, on the one hand, permits one to observe very faint stars at the best possible angular resolution, on the other it is achieved at the expense of probing only a very limited set of initial conditions for star formation, as all these clouds have essentially solar metallicity. The Magellanic Clouds, with their sub-solar mean metallicity (and proximity to the Sun), offer the ideal environment to overcome this limitation. I will present the current status and future perspectives of an ongoing observational effort to discover and characterize solar-type Pre-Main Sequence stars in the Magellanic Clouds, based on multi-wavelength broad and narrow-band imaging with the WFPC2 on board the HST. In particular, I will discuss the discovery strategy based on Halpha emission, the systematic uncertainties on the derived stellar Initial Mass Function and star formation rate due to the inherent incompleteness of the sample, and the time scale for accretion and disk dissipation, which seems to be much longer in the Large Magellanic Cloud than in the solar neighborhood.
Jonathan TAN Princeton University,
Oral Title:
Star and Star Cluster Formation: Insights from Orion
As one of the nearest and youngest clusters with a health complement of massive stars, the Orion Nebula Cluster (ONC) presents a unique opportunity for constraining disparate theories of formation. I review what we can learn about the birth of massive stars from the BN-KL region, which harbours both an accreting massive protostar and a dynamically ejected runaway. I discuss what Orion tells us about global models of cluster formation.
Rolf CHINI Astronomisches Institut Ruhr-Univ. Bochum,
Oral Title:
Formation and Progenitors of massive Stars
The observational evidence for massive star formation is briefly reviewed.Special emphasize is given to a recently discovered huge disk around an object of about 15 solar masses that supports the accretion scenario. The disk is orientated almost edge-on with a diameter of at least 20.000 AU. Interferometric molecular line observations show a rotating disk of at least 100 solar masses. At optical wavelengths, a bipolar, bowl-shaped reflection nebular perpendicular to plane of the disk delineates the walls of a huge cavity. From the innermost part of the disk an obviously precessing outflow can directly be seen which interacts with the ambient medium. Optical spectra provide clear evidence for both an ongoing accretion process and a strong mass loss.
Daniel KUNTH Institut d'Astrophysique de Paris,
Oral Title:
From local to distant Starburst: the fate of Lyman photons
I will review the impact of a starburst event to the interstellar medium as deduced from the observational UV properties of local starburst galaxies taken from their Lyalpha line and Ly continuum. HST and FUSE data will be discussed. The fate Ly alpha photons critically depends on the properties of the ISM (kinematics, dust, porosity) and the evolution of the starburst embedded into the HI surrounding gas. These properties have some bearings on the way Ly alpha emitters at large distance must be searched for and the use of Ly alpha to derive the cosmic star formation.The presence of an extended HI halo not onl;y explain the various line observed profiles but may act efficiently to retain metals into the host galaxies, even for dwarfs.
Gwendolyn MEEUS AIP,
Oral Title:
Will be given later
Paolo PADOAN University of California, San Diego,
Oral Title:
Not decided yet
Jerome BOUVIER Laboratoire Astrophysique Observatoire de Grenoble,
Oral Title:
Young brown dwarfs and the substellar IMF
Authors : J. Bouvier, E. Moraux We will review recent determinations of the substellar mass function in several nearby young open clusters. Implications for the brown dwarf formation process and for their early dynamical evolution in clusters will be discussed.
Thibaut PAUMARD Max Planck Institut für Extraterrestrische Physik,
Oral Title:
Census of the Galactic Center early type stars using spectro-imagery
The few central parsecs of the Galaxy are known to contain a surprising population of early type stars, among which at least 30 Wolf-Rayets and LBVs, identified thanks to their strong emission lines. Despite the presence of emission from ionized interstellar material in the same lines, the latest advances in spectro-imaging have made it possible to use the absorption lines of the OB stars to characterize them as well. This stellar population is particularly intriguing in the deep potential well of the 4 million solar masses black hole SgrA*. I will review the properties of these early type stars known from spectro-imagery, and discuss possible formation scenarios.
Richard ALEXANDER IoA, Cambridge,
Oral Title:
Photoionization of circumstellar discs
To be given later.
Eduardo MARTIN Instituto de Astrofisica de Canarias,
Oral Title:
Sori 70: Cluster planet or brown dwarf interloper ?
The status of the coolest candidate member of the Sigma Orionis open cluster will be reviewed. If the Tdwarf SOri70 is a cluster member, it would have a mass of only 3 Jupiters, and it would be a benchmark for a new class of giant planets, but if it is not a member, it would simply be yet another (boring?) brown dwarf.The membership of SOri70 in the cluster has recently been questioned by Burgasser et al. 2004. We assess Burgasser's claims and we discuss how to solve the controversy. We will also present the discovery of more cluster planet candidates in Sigma Orionis.
Paul CLARK University of St Andrews,
Oral Title:
The onset of collapse in turbulent clouds
Several theories have appeared over the years, attempting to explain the characteristic mass distribution represented by the IMF. These studies tend to work from two different viewpoints and can thus be bundled loosely into two extreme catagories: those governed by fragmentation and those governed by accretion. The models based on fragmentation suggest that stars form out of clumps of gas that have mass spectrum closely related to the final IMF, as has been shown by the observations of Motte, Andre \& Neri (1998). The opposing scenario whereby accretion shapes the stellar mass distribution also has its observational motivation, since it is now well known that most stars are formed in clusters. In the early gas dominated phase of a cluster's life, accretion is likely to be important since the gas densities will be high during the collaspe of the natal cloud. We have addressed this problem via SPH simulations of small turbulent cores. Our findings indicate that both fragmentation and accretion are important factors in determining the final mass of a star. Contrary to the findings of recent papers, we find that it is the initial average Jeans mass that controls the fragmentation and not the effects of turbulent compression. Subfragmentation is however important, and the Jeans mass sized regions are the sites of binary and multiple system formation, where mass has to be gained by competitive accretion. Although our results are gained from simulations of decaying turbulence, we will discuss the implications for clouds where the turbulence may be driven.
David ELBAZ CEA Saclay - Service d'Astrophysique,
Oral Title:
Dust enshrouded starbursts and the origin of present-day stars
The combination of deep extragalactic surveys in the mid to far infrared with the existence of a strong cosmic infrared background have strong implications on the origin of present-day stars. In combination with ground-based follow-ups in the optical to near infrared, these observations imply that most present-day stars were formed during starburst events mainly below z=2. These strong and extreme events of star formation are rare in the local universe but they make the bulk of stars in the distant one. They are the natural result of the growth of large-scale structures and as a consequence we will argue that star formation events at the scale of molecular clouds are sensitive to their large-scale environment. Rare and extreme events in the local universe might therefore be more relevant to the issue of star and galaxy formation than more quiescent events which dominate in the local universe.
Dieter BREITSCHWERDT Institut fuer Astronomie, University of Vienna,
Oral Title:
KEYNOTE Lecture: Galactic and extragalactic bubbles
Jan PALOUS Astronomical Institute, Academy of Sciences of the Czech Republic,
Oral Title:
Supershells and triggered star formation
We show supershells in the Milky Way, as they have been indentified in an authomatic search of HI shells in 3D data cubes. They are compared to shells and supershells in LMC, SMC and other galaxies. We discuss their shapes, expansion velocities, energies and other properties connected to star formation, stellar winds and supernova explosions driving the turbulent ISM. We explore when they fragment and produce gravitationally bounded clumps. Parameters of the galaxy disks such as z-stratification, rotation and shear are important: the expanding supershells collapse and trigger subsequent star formation, when is the disk gas surface density high enough, when is the disk rotation slow enough, and when is the gas cooling fast enough. The mass spectrum of fragments is derived and approximated by a power law with spectral index near to -2.3 close to the slope of the stellar IMF. References: Ehlerov\' a S. \& Palou\v s J., 2004, A\&A submitted \\ Palou\v s J., W\" unsch R. \& Ehlerov\' a S., 2004, MNRAS submitted \\
Simon HODGKIN Institute of Astronomy,
Oral Title:
CIRPASS multi object spectroscopy of young stellar objects
No abstract yet. This can be oral or poster contribution as you prefer.
Sebastien MULLER Institute of Astronomy and Astrophysics ASIAA,
Oral Title:
Molecular clouds and their structure in M31
Hans ZINNECKER Astrophysikalisches Institut Potsdam,
Oral Title:
Keynote address day2: star formation and the IMF
I will wake you up with a discussion on the origin of stellar mass and the stellar IMF, highlighting the aims of the new EC network "CONSTELLATION". Models of the star formation both at the high mass end (massive stars) and at the low mass end (brown dwarfs) will be critically examined and the issue of a characteristic mass and its dependence on various parameters (metallicity, Mach number, gas pressure, etc) will be raised. Major unsolved problems in star formation will be briefly addressed and future directions will be indicated.
Patrick HENNEBELLE Observatoire de Paris / Ecole normale superieure,
Oral Title:
Impulsively triggered collapse of prestellar cores
We have investigated the collapse of low-mass, isothermal, molecular cores which are subjected to an increase in external pressure. If the external pressure increases very slowly, the core approaches instability quite quasi-statically. However, for fast compressions, a compression wave is driven into the core (Hennebelle P., Whitworth A., Gladwin P., Andre A. 2003 MNRAS) and the collapse occurs dynamically. Quantitative comparisons with observational velocity and density profiles will be presented for one very young protostellar core belonging to Taurus (IRAM04191) and for one protostellar core belonging to Perseus (IRAS4A). It has been found that slow compression is required in order to match the first one whereas very rapid compression appears necessary to reproduce the second one. The consequences of this compression for the fragmentation of the cloud have been investigated and will be presented and discussed (Hennebelle P., Whitworth A., Cha S.-H., Goodwin S. 2004 MNRAS).
Shantanu BASU University of Western Ontario,
Oral Title:
Magnetic Field Effects on the Formation and Evolution of Dense Cores
We present new numerical MHD simulations which model the nonlinear processes of core formation and/or turbulence. Several of our models are characterized by the inclusion of the effects of ion-neutral friction. We demonstrate that gravitationally driven modes in a system in which nonaxisymmetric modes are allowed, inevitably lead to cores which are mildly elongated; their three-dimensional structure is somewhat triaxial. The initial mass-to-flux ratio of a molecular cloud plays a critical role in determining the magnitude of infall motions, as well as whether envelopes can be "held up" against the pull of gravity. Cores in our model naturally have an "edge" beyond which the density merges into a background value, reminiscent of some recent observations. The effect of turbulent motions in a stratified magnetized cloud that is bounded by a hot and tenuous external medium is also modeled. Clouds naturally achieve a steady state in which the observed correlation between velocity dispersion and mean Alfven speed is maintained. This is despite the fact that motions may locally be very sub-Alfvenic.
Philippe ANDRÉ CEA Saclay - Service d'Astrophysique,
Oral Title:
Submillimeter observations of prestellar cores and protostars: Probing the initial conditions for the Initial Mass Function
Improving our understanding of the earliest stages of star formation is crucial to gain insight into the origin of stellar masses. In particular, there is a major controversy at the moment between two schools of thought for the formation and evolution of prestellar cores in molecular clouds: The classical picture based on magnetic support has been seriously challenged by a new, more dynamic picture which emphasizes the role of supersonic turbulence. We will discuss the results of recent observations that set constraints on these two scenarios. The initial formation of dense cores is probably driven by turbulence as ambipolar diffusion appears to be too slow to play the leading role at low densities. There is, however, good evidence that the evolution and gravitational collapse of isolated protostellar cores is strongly magnetically controlled and that stellar masses are are least partly determined by magnetic decoupling effects.
Vincent MINIER CEA Saclay - Service d'Astrophysique,
Oral Title:
High-mass star formation seen through methanol masers
Recent radio and millimetre surveys in the Milky Way have revealed a close relationship between methanol masers and the early stages of high-mass (> 8 Msolar) star formation. Interestingly, methanol masers are not detected in regions forming less massive stars such as rho-Ophiuchi. About 550 methanol maser sites have been detected in the Galactic plane, which give an insight of the Galactic distribution of the high-mass star-forming regions. These masers are also excellent tools to probe the star-forming cores at scales of 1-100 AU. They are bright (10-1000 Jy) radio molecular lines with narrow linewidths (0.5 km/s), require high gas density (>10^5 cm^-3) and temperature (>100 K) conditions and arise from small (1-100 AU) masing clouds. Millimetre and IR observations have shown that methanol masers trace hot (>100 K), dense (>10^5 cm^-3) molecular cores within complexes of high-mass star formation. They trace disk-like structures and are also seen in outflows associated with high-mass young stellar objects. I shall review recent results on methanol masers and star formation, including their Galactic distribution and detailed studies of star-forming clusters associated with masers.
Pierre-Alain DUC CEA-Saclay,
Oral Title:
Extreme conditions for star formation in galaxy collisions
Frederic SCHULLER Max Planck Institut fuer Radioastronomie,
Oral Title:
The recent massive star formation activity in the Galactic Center region
The Galactic star formation activity is mainly concentrated in the inner Disk, and in particular in the Central Molecular Zone (CMZ, |l| < 1.5 deg, |b| < 0.5 deg), where giant very active star forming complexes (Sgr B2, Sgr C) and exceptional massive young clusters that formed a few Myr ago (the Arches, the Quintuplet and the central helium star clusters) are present. In addition, massive stars are currently being formed outside of these peculiar regions, as clearly indicated by the emission of warm dust in the mid-infrared. In this talk, I will show how it is possible to extract the young stellar population from large scale mid-infrared surveys, such as ISOGAL and MSX. A sample of 300 massive YSO candidates was selected from these surveys over the entire CMZ. This provides a rough estimate of the average star formation rate in this extreme environment over the last few Myr. I will also mention planned and ongoing follow-up observations, aimed at confirming the young stellar nature of these candidates, and at deriving their physical properties.
Toshikazu ONISHI Department of Astrophysics, Nagoya University,
Oral Title:
Evolution from dense cores to protostars in low-mass star forming regions
A study of star formation has been largely progressed by detections of protostars accompanying outflow phenomenon. However, there still remain a number of unresolved problems in a study of dense molecular cores before protostar formation. This is mainly because surveys of dense cores have been biased toward known optical and/or infrared features. We thus have carried out a molecular-line survey for starless condensations in an unbiased way toward ~10 low-mass star forming regions in the lines mainly of C18O and H13CO+(J=1-0). The observed regions include Taurus, Ohiuchus, Chamaeleon, Lupus, and so on. All the data were taken purely based on molecular data; all the observations have been made based on 13CO observations that reveal entire distribution of gas of an intermediate density. With these observations, we have obtained a uniform and almost complete sample of dense cores with a density n(H2) from 104 to 106cm-3 in the observed star forming regions. This enables us to study the evolution of dense cores to protostars statistically for the first time. It is to be noted that a big advantage of the molecular line observations over continuum observations is that the velocity dispersion of a core can be measured to determine the dynamical status. This information is crucial to find gravitationally bound structures that directly lead to a star formation. We identified about 200 C18O cores in total, and found that the intensity of C18O emission is a nice tracer of the star formation activity. Especially the column density of the C18O has a positive correlation with the probability of star formation and has a threshold value for star formation. We also found that turbulent decay is indicated by diminishing dV from the starless to the star-forming cores. The mass spectrum of the C18O cores can not be fitted by a single power-law function, and the index of high-mass end resembles the stellar IMF. Based on the C18O data above, we have carried out H13CO+(J=1-0) observations. The observed regions include Taurus, Opiuchus, Chamaeleon, Pipe Nebula, and Lupus. These starless condensations are compact (R<~0.1 pc) and of high density (>~105 cm-3) and thus are highly probable candidates for protostellar condensations just before star formation. A comparison of masses between starless condensations and those with stars indicates that most of the starless condensations will not experience a fragmentation except for a binary formation, i.e, these condensations are fundamental unit of star formation. The mass spectrum of the condensations is very steep and similar to that of stellar IMF. The subsequent higher transition study found the densest starless condensation, which is very close to a moment of protostar formation of less than 10^4yr.
Hiroaki YAMAMOTO Nagoya University,
Poster Title:
The detection of molecular gas with peculiar velocity toward the Galactic Center
We have carried out 12CO (J=1-0) observations toward the Galactic Center by using the NANTEN 4-m mm-submm telescope of Nagoya University. The observations cover -10 < L < 10 and -5 < B < 5 (unit: degree) with a grid spacing of 4 arc-minutes. The wide coverage along the Galactic latitude succeeded to obtain a distinctive result from the previous studies; a detection of many features of gas perpendicular to the Galactic plane. These features well demonstrate the existence of energetic events at the galactic center in the past. One of the peculiar features is the existence of molecular clouds with forbidden velocities out of a galactic rotation model that is located far from the galactic center of ~ 1 kpc. In order to derive the accurate physical properties, we made deep 12CO and 13CO (J=1-0) observations toward the corresponding HI features distributed above the galactic plane at negative longitude and below it at positive longitude revealed by van der Kruit (1970). We detected 12CO emission whose total luminosity is about 3.6×10^5 (K km s^-1 pc^-2). The 13CO (J=1-0) observation was made toward the 5 points of and around each peak position of 24 of 42 molecular clouds identified by the 12CO emission. We detected the significant emissions toward 8 of them. The optical depth of 12CO of molecular clouds with 13CO emission is &#65374;4, grater than that toward Galactic Center, &#65374;2. We assumed that molecular clouds are in virial equilibrium with the external pressure, and the total molecular mass is estimated to be 2.9×10^5 Mo. We estimated that the external pressure is 1.0×10^5 [cm^-3 K] which is 5 times higher than that in the 2nd quadrant (Heyer et al. 2001) and 3 times lower than that of the Galactic Center (Oka et al. 1998). The X-factor derived is 0.6×10^20 (cm^-2 [K km s^-1]^-1). Most of these molecular clouds distributed over the forbidden velocity region of the Galactic rotation model. It may suggest that these molecular clouds are the remnant of the past phenomena in the Galactic Center.
Yasuo FUKUI Nagoya University,
Oral Title:
GMCs and star formation therein in the Milky Way and the Magellanic system
Recent CO results obtained with NANTEN will be presented for giant molecular clouds (=GMCs) in the Milky Way and the Magellanic system. The aim of this talk includes a comparison of the physical properties of GMCs (e.g.,mass spectrum, X factor, star-forming activities etc.) under different environments in metallicity and gravitational field. The Milky Way covers the regions from the galactic center, the spiral arms, and the warp and the Magellanic system covers LMC, SMC, and the Bridge. These datasets will also be compared with those of M33 and M31 to obtain an improved insight into the evolution and star formation in GMCs of the Local group.
Frederique MOTTE Service d'Astrophysique, Centre d'Etudes de Saclay,
Oral Title:
Identifying and characterizing the earliest phases of massive star formation
Authors: Motte, Bontemps, Schilke, Lis, Schneider, Menten I will present the (sub-)millimeter continuum and line studies we started in several high-mass star-forming complexes. First, a complete MAMBO survey of the Cygnus X (3 deg^2) and NGC7538 (1 deg^2) complexes reveal a large population of massive protostar candidates overlooked by IRAS, i.e. high-mass analogues of Class 0s. Molecular lines, masers, and radio continuum follow-ups were started to confirm their nature. Preliminar results suggest that the massive Class 0 phase may last as long as the infrared protostellar phase. Second, a kinematic survey of several protoclusters in W43 and Cygnus X suggest that the gas undergoes a fast contraction. These large-scale motions may allow the formation of a massive star via acrretion only, i.e. a scaled-up version of thr low-mass star formation process.
Estelle MORAUX IoA,
Oral Title:
Fabrizio MASSI Osservatorio Astrofisico di Arcetri, INAF,
Oral Title:
Intermediate-luminosity YSOs in the S235A-B region
High resolution mm observations in molecular transitions of HCO+, C34S, CH3CN, H2CS and SO2, and in the 1.2- and 3.3-mm continuum, unveiled an intermediate-mass (> 6 Msun) YSO in the star forming region S235A-B. These were complemented with SCUBA maps at 450 and 850 microns, and allowed to trace the molecular core where the protostar is embedded. Multiple outflows and the signature of a possible circumstellar disc were also detected. This YSO is a rare example of an intermediate luminosity protostar (~ 1000 Lsun), hence it represents a link between the earliest evolutionary phases of massive stars and low-mass protostars (Class 0-I sources).
Maite BELTRAN Osservatorio Astrofisico di Arcetri, INAF,
Oral Title:
Rotating Disks in High-Mass Young Stellar Objects
We report on the detection of four rotating massive disks in two regions of high-mass star formation: G24.78+0.08 and G31.41+0.31. The identification of such disks is confirmed by the fact that their rotation axis is parallel to the axis of previously known bipolar outflows. Such disks turn out to be unstable but long-lived. We infer that accretion onto the embedded (proto)stars must proceed through the disks with rates of ~0.01 Msun/yr. This result strongly suggests that nonspherical accretion is a viable mechanism to form high-mass stars.
Willem-Jan DE WIT Osservatorio Astrofisico di Arcetri, INAF,
Oral Title:
Star clusters near intermediate and high mass young stars
We review the situation of young compact star clusters near Herbig Ae/Be stars (e.g. Hillenbrand et al. 1995, Testi et al. 1999) and report the absence of such clusters near the more massive but similarly aged massive field O-type stars. We show that the latter observation is predominantly due to the phenomenon of runaway OB stars. From this we argue that the census of massive stars in the Galaxy is compatible with all massive stars being formed in clusters/associations.
Francesco PALLA INAF-Osservatorio Astrofisico di Arcetri,
Oral Title:
The star formarion history of the local neighborhood
Simon GOODWIN Cardiff University,
Oral Title:
The origin of the unusual IMF in Taurus
The IMF of Taurus is unusual, it peaks at 0.8 M_\odot and as far fewer brown dwarfs per star than the field or Orion. It also has an unusual core mass function. We show that the IMF is a direct consequence of the core mass function in Taurus.
David HUBBER Cardiff University,
Oral Title:
Binary Star Formation from Rotational Fragmentation
We investigate the statistics of binary formation assuming that the dominant mechanism is rotational fragmentation. Using a simple prescription which sets the scale at which a core fragments into protostars, we evolve the system dynamically using an N-body code until it has relaxed into multiple systems and ejected singles. The overall binary statistics compare well in some aspects with the observations, but do not account for the large range in periods observed for solar-mass binaries.
Ian BONNELL University of St Andrews, iab1
Oral Title:
Competitive accretion and the Initial Mass Function
Mark MCCAUGHREAN Astrophysikalisches Institut Potsdam,
Oral Title:
Poster Title:
Triggered Star Formation in the Trifid Nebula
Oral Title:
Low mass substellar candidates in NGC2264
Using CFHT/12K, we have performed deep (I=23-24) imaging of approximately 0.6 sq. deg. in the star-forming region NGC2264 (760 pc, 3Myr) in the I- and z-bands. By comparison to the DUSTY models of Baraffe, we have selected >200 candidates, with masses between the substellar limit and 15 Mjup, from the optical data. Surprisingly, over half of these candidates have counterparts in the 2MASS survey (within 2"). Following similar methods to those used by Briceno et al. (2002) and Luhman et al. (2003) in Taurus, we have been able to select 19 candidates by comparison to 1 and 5 Myr isochrones plotted in red/near infrared colour-colour diagrams, most importantly (I-K vs J-H) and (I-J vs I-K). The candidates have typical I-J colours >4.5; by comparison field L-dwarfs typically have 3<I-J<4. Their I-K colours are as red as 7. 12 of 19 candidates are selected by all combinations of colours, namely I-J, J-H, I-K and H-K. Follow-up spectroscopy has been requested at AAT/IRIS2 to obtain spectral types in the J-band for four candidate brown dwarfs which possess small K-band excesses.
Anthony WHITWORTH School of Physics & Astronomy, Cardiff University,
Oral Title:
Protostellar collapse and accretion in the context of triggered star formation
I will review various possible mechanisms of triggered star formation, and present numerical simulations and/or semi-analytic results for some of them, viz.: (i) star formation triggered by cloud/cloud collisions; (ii) star formation in shells swept up by expanding nebulae; (iii) star and brown dwarf formation in cores overrun by shock waves and ionization fronts; (iv) star formation in interacting protostellar discs; (v) the minimum mass for star formation in dynamically triggered events.
Dimitris STAMATELLOS Cardiff University,
Oral Title:
Dust temperatures in asymetric prestellar cores
We present radiative transfer models of asymmetric prestellar cores, using a 3D Monte Carlo code that calculates the dust temperature, and produces SEDs and isophotal maps at different viewing angles. We find that the temperature of the dust in a prestellar core is dependent on the core environment (ambient molecular cloud and ambient radiation field), and that it is probably lower than what previous studies have assumed. We also discuss the importance of observing cores near the peak of their emission spectra, and we point out observable characteristic features on isophotal maps at FIR wavelengths that are indicative of the cores' density and temperature structure. [Day 1: Initial conditions for star formation and environmental effects]
Oral Title:
Jürgen KNÖDLSEDER Centre d'Etude Spatiale des Rayonnements,
Oral Title:
The Cygnus X region - a multi wavelength view
Miguel DE AVILLEZ University of Evora,
Oral Title:
Global evolution of the ISM and its Effect on star formation on small and large scales
Lise DEHARVENG Laboratoire d'Astrophysique de Marseille,
Oral Title:
Star formation triggered by HII regions
I will consider the physical processes by which HII regions can trigger star formation. Various observations will be presented and discussed to illustrate these processes.
Isabelle GRENIER Université Paris VII & CEA Saclay,
Oral Title:
The Gould belt, local star formation, and the local interstellar medium
The history of the interstellar medium on a kpc scale is dominated by the evolution of the Gould Belt. The event that triggered this starburst region and molded the cloud distribution is still unknown. The Belt flatness and its tilt, some 20 degrees to the Galactic plane, remains very difficult to interpret. Various scenarii involve the impact of a high-velocity cloud, a cascade of supernovae, or the braking of a supercloud entering the spiral arm. The Belt orientation and its extent are reasonably well determined. Its expansion has been modelled in 3D and fitted to the space and velocity distributions of all HI and H2 clouds within a kpc. The present rim coincides in space and velocity with most of the nearby H2 clouds, and in space with the nearby OB associations. Their velocity field do not seem to be related to the Belt expansion. The Belt age is uncertain by a factor of 2 because of the discrepancy found between the dynamical ages (20-30 Myr) and the stellar ages derived from photometry (30-80 Myr). The Belt stellar content is derived from kinematic studies for massive stars and X-ray observations for young solar-mass stars. Whether star formation is active along the Belt rim or spread over a large fraction of the Belt disc is debated. The Belt exhibits new facets at high energy because of its enhanced supernova rate which has been estimated to be 3 to 5 times larger than the local Galactic rate. A population of stable gamma-ray sources that could be powered by neutron star activity, Myr-old pulsars for instance, has indeed been associated with the Belt. Nearby isolated neutron stars found in X rays could also be relics from Belt supernovae. This supernova activity would significantly impact the local cosmic-ray production, in particular the local cosmic-ray electron spectrum at high energy.
Inti PELUPESSY Sterrewacht Leiden,
Oral Title:
Bursts of starformation in dwarf irregulars
Andrew BAKER MPI fuer extraterr. Physik,
Oral Title:
Extreme Conditions for Star Formation in Starburst Galaxies
Ralf LAUNHARDT Max Planck Institute for Astronomy ,
Oral Title:
Direct observational constraints on the formation of binary stars
A major gap in our understanding of star formation concerns the origins of binary stars although there is growing evidence that most stars form in binary and multiple systems. While some theoretical predictions of fragmentation models are indirectly supported by statistical studies of evolved binary stars at shorter wavelengths, direct observations of the formation phase became only possible with the advance of large millimeter interferometers. Molecular line spectroscopy and dust continuum observations at high angular resolution can address some of the key questions in binary star formation theories. I will rewiev observing methods and results of recent studies of binary protostellar s ystems under special consideration of the evolution of angular momentum from pre-stellar cores, through binary protostars, to single and binary MS stars.
Denis BURGARELLA Observatoire Astronomique Marseille Provence - LAM,
Oral Title:
The Local Universe and GALEX
GALEX is a 50-cm telescope dedicated to the observation of the sky at UV wavelengths in two bands centered about 150 and 230 nm. Several photometric and spectroscopic surveys are building up, among which the first All-Sky Survey is the first ever in this wavelength range. I will present GALEX and presents some of the first scientific results related to the local universe. A Guest Investigator Program is planned with a deadline on 16 April 2004.
Daniel SCHAERER Geneva Observatory,
Oral Title:
PopIII and very metal-poor starbursts near and far
I will summarise the expected properties of PopIII and very metal-poor stars and starburst galaxies and discuss searches for such "primordial" galaxies mostly in the distant Universe.
Miguel AVILLEZ University of Evora, Department of Mathematics,
Poster Title:
OVI Distribution in the Local and Loop I Bubbles
The Local Bubble (LB), hosting the Local Cloud surrounding the solar system, is an X-ray emitting region extending 100 pc in radius in the Galactic plane and 200 pc perpendicular to it,and it is embedded in a somewhat larger H{\sc i} deficient cavity. Its origin and spectral properties in UV, EUV and X-rays are still poorly understood. We have performed 3D high resolution (down to 1.25 pc) hydrodynamic superbubble simulations of the LB jointly with the dynamical evolution of the neighbouring Loop I superbubble in a realistic inhomogeneous background ISM, disturbed by supernova (SN) explosions at the Galactic rate. We can reproduce (i) the size of the bubbles (in contrast to similarity solutions), (ii) the interaction shell with Loop I, discovered with ROSAT, (iii) predict the merging of the two bubbles in about 3 Myr, when the interaction shell starts to fragment, and, (iv) the generation of blobs like the Local Cloud as a consequence of a dynamical instability. The resulting temperature distribution is monitored in Oviii, Ovii, and Ovi. The latter is found to be in excellent agreement with Copernicus absorption line data, showing LB column densities of $<1.7 \times 10^{13} \, {\rm cm}^{-2}$ (Jenkins 1978, Shelton \& Cox 1994), in contrast to other existing models.