Abstracts

Name Title of contribution Type
Richard Allison Dynamical mass segregation on a short timescale oral
I will present N-body simulations of the collapse of initially sub-virial clumpy clusters. From these initial conditions dynamical mass segregation occurs on a very short timescale. The evolution of the clusters also leads to other interesting phenomena, including the formation of Trapezium systems and the violent ejection of massive stars.
Robi Banerjee Star Formation in Numerical Simulations oral
Galactic star formation proceeds through a complex interplay between various physical and chemical processes. This complexity and the intrinsic non-linear interaction of gravity makes it almost inevitable to tackle this problem with three dimensional numerical calculations. In this talk, I will summarise our progress in studying present day star formation based on numerical simulations performed with the FLASH code.

Present day star formation takes place in molecular clouds (MCs) and giant molecular cloud complexes (GMCs). But how do these cold molecular clouds condense out of the warm atomic interstellar medium? Here, I will present our model of MC formation in the magnetised interstellar medium (ISM) by colliding streams. In this model, triggered thermal instabilities result in condensates of turbulent, self-gravitating, molecular clumps which eventually collapse to form stars. The global contraction of the molecular cloud result in an enhancement of the column density at the center of the cloud leading to the typical environment where massive stars can be born. Such proto-stars, as well as their low mass counterparts, supply energy into their environment through radiation and mechanical feedback. I will present recent results from simulations on feedback from massive stars and low mass stars addressing questions on the origin of turbulence in the ISM.
Maite Beltran The stellar population and complex structure of the bright-rimmed cloud IC 1396N oral
Bright-rimmed clouds (BRCs) found in HII regions are potential sites of triggered star formation due to compression by ionization/shock fronts. IC 1396N is a good example of BRC with ongoing star-formation activity, where a number of Herbig-Haro objects, H2 jet-like features, CO molecular outflows, and millimeter compact sources have been observed. We will discuss the new results of the deep near-infrared survey of this globule carried out with NICS at the TNG telescope. We have found only few objects exhibiting a near-infrared excess and no clear signs of clustering of sources towards the southern rim, which questions the possibility that star formation in the globule has been triggered. Star formation is ongoing in the northern part as well. We will also discuss on the new possible flows that have been discovered in the globule.
Thomas Bisbas SPH simulations of star formation triggered by expanding HII regions oral
We present three dimensional SPH simulations of stable Bonnor-Ebert spheres ionized by an external source (Radiation Driven Compression) and we examine under which conditions the ionizing radiation can trigger star formation. We discuss about the morphological structure of each clump during their evolution, where star formation takes place (at the periphery or at the core), when it occurs (during the maximum compression phase or earlier), and what is the mass of stars formed. We propose a flux-mass diagram where we map the evolution of these spheres.
Ian Bonnell TBD oral

Sylvain Bontemps The earliest phases of high-mass star formation oral
I will summarize the recent observational results concerning the coldest, youngest stages of high-mass star formation. Since a few years, it was realized that a cold phase for the formation of high-mass star exist and can be observed. Since these cold, young objects are the best candidates to still contain informations on the initial conditions of the formation, these objects are to be surveyed for and studied in details for direct comparisons with theoretical predictions and models.
Andrew Burgess Young Methane Candidates in IC 348 poster
The determination of the lower-end of the initial mass function (IMF) provides strong constraints on star formation theories. We report here on a search for isolated planetary-mass objects in the 3 Myr-old star forming region IC 348.

Deep, narrowband CH4off and CH4on images were obtained with CFHT/WIRCam over 0.11 sq.deg. in the central part of IC 348 to identify young T-dwarfs from their 1.6 μm methane absorption bands.

We report three faint T-dwarf candidates with CH4on−CH4off colours >0.4 mag. Extinction was estimated for each candidate and lies in the range AV ∼ 5−12 mag. Comparisons with T-dwarf spectral models, and colour/colour and colour/magnitude diagrams, reject two of the three candidates due to their extreme z−J blueness. The one remaining object is not thought to be a foreground field dwarf from a number density argument, and also from its strong extinction AV ∼ 12 mag, nor a background field T-dwarf which would be expected to be much fainter. Models and diagrams give this object a preliminary T6 spectral type.

With a mass of a few Jupiter masses, the young T-dwarf candidate reported here is potentially the youngest, lowest mass object detected in a star forming region so far. Its frequency is consistent with the lognormal extrapolation of current IMF estimates down to the planetary mass domain.
Cátia Cardoso Dynamical masses for the nearest brown dwarf binary: Eps Indi Ba, Bb poster
We present new preliminary astrometric results for the closest known brown dwarf binary to Earth, Epsilon Indi Ba, Bb at a distance of 3.6224 pc. The relative orbital motion of the brown dwarfs (spectral types T1 and T6) has been monitored since June 2004 with the VLT NACO near-IR adaptive optics system. With data for more than half the orbit now, we obtain an accurate total dynamical system mass (<1%), considerably in excess of earlier determinations based on evolutionary models. We have also been monitoring the absolute astrometric motion of the system since August 2005 against a network of field stars using the VLT FORS2 optical imager with the aim of determining the individual masses. Our current orbit solution predicts periastron passage in early 2010, and shortly thereafter, we should be able to determine the absolute masses to better than 5% in a model independent way.
Riccardo Cesaroni Kinematics of high-mass star formation: The case of G31.41+0.31 oral
The debate on the formation of high-mass (O-B) stars can benefit from
knowledge of the velocity field of the molecular gas of the parental
cores. Interferometric studies at (sub)mm wavelengths are attaining sub-arcsec
resolutions which make it possible to analyse regions as small as a few
1000 AU, where the mass of the gas becomes comparable to that of the newly
formed star(s). In this region the velocity field may be an important hint
to shed light on the star formation process. For this purpose it is important
to discriminate between expansion (in outflows), collapse (onto the star),
and rotation (about the star). We will present the case of the hot molecular
core G31.41+0.31, which has been investigated in great detail with
observations ranging from centimeter to mid-IR wavelengths and appears to be
an excellent candidate of a rotating/infalling core, possibly containing a
loose binary system.
Paul Clark Discs around massive stars and their companions oral
Numerical simulations are now able to follow the basic properties of the discs that form around young stars in clusters. In this contribution, we discuss the formation of these discs, emphasising the differences between the discs that form around low-mass, isolated objects and those which form around the high-mass stars that tend to form in the centres of clusters.
Cathie Clarke The collisional formation of massive stars oral
Following Bonnell et al 1998, collisions in dense proto-cluster cores are often discussed as an alternative mode of massive star formation that avoids the problems of the effect of radiation pressure in conventional accretion scenarios.
I describe recent work that attempts to define the parameters of clusters that
could in principle host the required collisional runaway, discussing both
analytic arguments (Clarke \\& Bonnell 2008) and the results of Monte Carlo dynamical simulations of accreting protoclusters (Davies \\& Clarke in prep.).
I will also discuss what further simulations are required in order to further
clarify this issue.
Claudio Codella Extremely high velocity outflows from the high-mass YSOs in IRAS17233-3606 oral
Molecular outflows from high-mass YSOs provide an excellent way to study the star forming process and investigate if they are scaled-up versions of their low-mass counterparts. We observed the nearby massive star forming region IRAS17233-3606 in the CO(2-1) and (6-5) lines by using the SMA and APEX telescopes, respectively. Our data show multiple outflow components characterised by extremely high velocities (up to 200 km/s) and by high collimation factors. The estimate of the kinematical outflow parameters points to massive objects that still did not reach the main sequence.
Timea Csengeri Origin of high-mass stars and clusters in Cygnus-X oral
We study six IR-quiet massive dense core in the Cygnus-X star forming region - one of the closest site hosting high-mass star formation.  With the Plateau de Bure Interferometer we obtained high-resolution observations at 1 and 3 mm continuum and molecular line tracers, like H13CO+. We aim to study the (1) level of fragmentation, (2) properties of massive protostars from the dust continuum observations, (3) the dynamics of gas using molecular line tracers.
Reaching the size-scale of individual protostars (0.01 pc) we confront our observations to the current theories for massive star-formation.
Joerg Dabringhausen Top-heavy IMFs in ultra-compact dwarf galaxies? oral
Ultra compact dwarf galaxies (UCDs) are dense stellar systems at the border between massive star-clusters and small galaxies. The perhaps most remarkable finding about them is that their average optical mass-to-light (M/L) ratio cannot be explained by stellar populations with the canonical stellar initial mass function (IMF). It is doubtful that non-baryonic dark matter can accumulate enough on the scales of UCDs for influencing their dynamics significantly, which makes non-canonical IMFs a very attractive alternative explanation for the high M/L ratios of UCDs. This can be understood if young UCDs represent a case of rapid star-formation in an extremely dense environment, leading to a top-heavy IMF and thereby to a high number of dark remnants in an aged stellar system. While top-heavy IMFs imply a much heavier mass-loss shortly after the formation of a stellar system, the UCDs are not necessarily dissolved by this process. Their formation with a top-heavy IMF would therefore not contradict their existence.
Jim Dale Mass functions from the fragmentation of expanding shells oral
I will present results from an ongoing study of the gravitational fragmentation of expanding shells, discuss the mass function produced by this process and explore the implications for the important question of the importance of self-triggering in star formation.
Arabela de la Nuez Cruz poster

Lise Deharveng Massive stars - observation of the feedback oral
I shall focus on observations of star formation triggered by classical
HII regions. Among the main points discussed are the distribution of
molecular material in the vicinity of HII regions (existence of collected
material?) and the distribution and nature of young stellar objects
associated with these regions (evolutionary stage, location and mass).
I shall also present the first results pertaining to this subject from the
ATLASGAL survey of the Galactic plane at 870 microns.
Daniele Galli oral

Philipp Girichidis Influence of the initial conditions on massive star formation poster
The formation of massive stars in dense molecular clouds is strongly influenced by the initial conditions of the gas. Especially the choice of a turbulent velocity field and the initial density distribution play an important role in the fragmentation of the cloud, the resulting formation of the stars and their accretion history. With the help of three dimensional simulations a comparison of various initial setups will be presented.
Simon Glover The high-mass slope of the IMF at sub-solar metallicities oral
The observed slope of the high-mass end of the initial mass function (IMF) displays a remarkable universality in a wide variety of physical environments. In this talk, I discuss a model for the IMF that we have recently developed that argues that competitive accretion provides a natural explanation for this universality, and that shows that the conditions that lead to competitive accretion occur for a very wide range of metallicities and environmental conditions.
Simon Goodwin The Formation of Clusters oral
Star clusters do not form as nice, spherical, virialised objects - they form clumpy and cold. From clumpy and cold initial conditions many properties of star clusters such as their binary properties, mass segregation, the formation of Trapezium-like systems and early cluster destruction might be explained quite simply.
Matthias Gritschneder The impact of ionization on turbulent molecular clouds oral
We perform a set of high resolution simulations on the impact of the
UV-radiation of massive stars on the turbulent interstellar medium (ISM).
This parameter study includes different levels and driving scales of the turbulence, different ionizing flux as well as different temperatures and
densities of the cold gas. We find a clear correlation between the
initial state of the turbulent cold cloud and the final morphology and
physical properties of the structures adjacent to the HII region. From
the simulations we are able to derive a criterion for the formation
of pillar-like structures and thus the formation of cores and
stars. Gravitational collapse occurs regularly on the
tips of the structures. We also derive column densities and velocity
profiles of our simulations and find these to be in very good
agreement with the observations of trunks and cores. The line-of-sight
velocity profiles of the simulations resemble the observed rotational
patterns in some projections, although the true velocity fields are
turbulent.
Mario Giuseppe Guarcello Effects of massive star radiation on circumstellar disks evolution in the Eagle Nebula oral
The Eagle Nebula is a region where several episodes of recent or even ongoing star formation are present. Moreover, more than 50 OB stars are not homogeneously distributed in NGC6611, in the central region of the nebula; whereas no massive stars are present in the outer regions. Therefore, the Eagle Nebula offers the opportunity to study different environments where stars form and their circumstellar disks evolve. In NGC6611 we selected more than 1000 diskless and disk-bearing members by their X-ray emission and infrared excesses, respectively. Our analysis shows that the UV radiation emitted by massive stars affects significantly the evolution of nearby circumstellar disks, with disk frequency declining at small distances from massive stars.

To extend our results and to test disks evolution in the different environments of the Eagle Nebula, we have also identified, using the same diagnostics, pre main sequence stars associated with different star formation episods in the outer regions of the nebula where no massive stars formed.
Patrick Hennebelle An analytical theory for the initial mass function: CO clumps and Prestellar cores oral
Star formation is one of the important challenge of the modern astrophysics. Amongst many questions, understanding the initial mass function of stars (IMF), that is the number of stars of a given mass, is tremendously important. Several theories have been proposed to explain the IMF without great success. More recently, numerical simulations of supersonic turbulence including self-gravity have obtained IMF which resemble the observed one. In the talk, I will present an analytical theory, inspired from the approach used in cosmology to predict the galaxy mass spectrum, which use the statistical properties of the supersonic turbulence inferred from numerical simulations. The theory predicts an IMF which seems to be in good agreement with the observations. Within the same formalism, I will show that the mass spectrum of the molecular clumps can also be predicted and linked to the powerspectrum of the density fluctuations.

David Hubber oral

Katharine Johnston Ionized Gas Towards Molecular Clumps: Physical Properties of Massive Star Forming Regions oral
I will present results from our survey of ionized gas at 3.6 cm, using the Very Large Array, towards 31 intermediate- and high-mass clumps detected in previous millimeter continuum observations. With these observations, we have studied the relationship between the star forming gas, traced by millimeter continuum emission from dust, and the ionized gas created by massive stars. We will select the most promising objects from this study for follow up with higher resolution observations, to map any outflows or disks towards these sources, and to study how the formation of an HII region affects the material within several hundreds of AU of the star. Therefore, we selected sources that are within a declination range suitable for future study with Atacama Large Millimeter Array (ALMA) and the Expanded Very Large Array (EVLA).
Vera Konyves Triggered star formation and the large-scale structure of the interstellar medium poster
The large-scale structure of the cold interstellar matter in the Galaxy can be significantly affected by violent events. Massive stars can affect the nearby interstellar medium (ISM) not only at late stages when they become supernovae but during more stable states by their strong stellar winds. These processes can create large bubbles in galaxies, built up by shock waves sweeping up gas and dust in thin shells.
In the surroundings of the Galactic midplane the shells, compressed by supernova- and stellar shock waves, provide a nest for the next generation of stars. Then high-mass stars, forming here, are the next sources of various shock waves.
We performed an all-sky survey of loop-like intensity enhancements in the diffuse far-infrared emission. The Catalogue of Far-Infrared Loops in the Galaxy contains 462 of these features. Physical and statistical investigations of the objects in our database provide a great opportunity to study the large-scale structure of the ISM in the Galactic neighbourhood of the Sun.
Pavel Kroupa Star clusters and their stellar populations oral
tbd
Ana Lopez-Sepulcre Molecular outflows towards O-type young stellar objects oral
We have mapped a sample of 11 high-mass star forming regions in 13CO(2−1) and C18O(2−1) with the IRAM-30m telescope on Pico Veleta (Spain) with the aim to search for massive molecular outflows and characterise their properties. The sample is composed of very luminous molecular clumps, possibly containing O-type stars.
The whole sample shows high-velocity wings in the 13CO(2−1) spectra, indicative of outflowing motions. Thus, molecular outflows are found to be as common in massive star forming regions as in low-mass star forming regions. From a comparison between our results and those found by other authors at lower masses, it is clear that the outflow mechanical force increases with the bolometric luminosity of the clump and with the ionising photon rate of the associated UCHii regions, indicating that high-mass stars drive more powerful outflows.
With a sample composed largely of more luminous objects than previous ones, this work complements analogous surveys performed by other authors by adding the missing highest luminosity sources.
Thomas Maschberger Properties of hierachically forming star clusters oral
We show results of an analysis of the calculations by Bonnell et al. 2003 and 2008 where between a few hundred and about 2500 stars/sink particles are formed. Via identifying subclusters one can follow quantitatively the time-evolution of structure, mass segregation and the upper mass function. We find that the properties of the subclusters depend on their evolutionary stage, with evidence for primordial mass segregation and an upper truncation mass of the IMF that depends on the richness of the subclusters.
Fabrizio Massi High-mass end of the Initial Mass Function oral
I will present the first results of a JHK imaging survey of a sample of small embedded young stellar clusters, all located in a same region and associated with the Vela Molecular Ridge (d~700 pc). This sample is well suited to investigate the COMPOSITE Initial Mass Function of the region and to assess whether small clusters can produce high-mass stars, though with a lower probability with respect to large star clusters.
Andrew McLeod Simulations of colliding molecular clouds oral
I shall present SPH simulations of colliding molecular clouds leading to the formation of small-N star clusters.
Luca Olmi Candidate High-Mass Starless Cores from BLAST oral
I will discuss high-angular resolution observations of ammonia toward
four candidates high-mass starless cores (HMSCs). The cores were
identified by the Balloon-borne Large Aperture Submillimeter Telescope
(BLAST) during its 2005 survey of the Vulpecula region where 60
compact sources were detected simultaneously at 250, 350, and
500micron. During a pilot project, four of these cores, with no
IRAS-PSC or MSX counterparts, were observed with the NRAO Very Large
Array (VLA) in the NH3(1,1) and (2,2) spectral lines. Our observations
indicate that the four cores are cold (T <~16K) and show a filamentary
and/or clumpy structure. They also show a significant velocity
substructure within ~1km/s. The four BLAST cores appear to be even
colder and more quiescent than other previously observed HMSC
candidates, suggesting an even earlier stage of evolution.\"
Jan Palous The Dense Stellar Clusters oral
The observed emission line profiles emitted from Super Star clusters will be reviewed. Hydrodynamical models, including stellar feedback in young and dense stellar clusters, provide an interpretation for these profiles. They also suggest that second generation of stars may form in thermally unstable places inside of dense clusters explaining their chemical inhomogeneities. Another consequence is the concentration of the reinserted mass in the very center of the cluster forming a massive central object.

Richard Parker Do massive stars form in isolation? oral
I will describe the observations that suggest some O- and B-type stars can form in modest (less than 100 Msun) clusters. I will demonstrate that they can be produced from randomly sampling the Cluster Mass Function (CMF) and then populating the clusters by randomly sampling the stellar IMF. This suggests that the relation between the most massive star in the cluster and the cluster mass is statistical, rather than fundamental.
Thomas Peters Ionization Feedback in Massive Star Formation oral
Massive stars strongly influence their natal environment by feedback
processes. Stellar winds, ionizing radiation and supernova explosions
contribute significantly to the matter and energy cycle in the galaxy.
Feedback processes have also been suggested to provide a natural
explanation for the upper limit to stellar masses. I will present the
first three-dimensional numerical simulations of massive star formation
with ionization feedback, providing the opportunity to directly compare
numerical models with observations. We will see that the H II region
gets trapped by filaments in the disk, fluctuates between confined and
extended states, drives a neutral bipolar outflow similar to those observed, and takes on all morphologies of ultracompact H II regions found in surveys
in a single run. These findings naturally resolve the UC H II lifetime problem
and explain their clustering.
Dieter Poelman Excitation of H2O in- and outside the planetforming region of young circumstellar disks poster
One of the most fundamental questions to date in modern astrophysics is how stars
and planets form. Circumstellar disks provide the material reservoir for the growth of young stars
and planet formation. Therefore, to understand disk and planet evolution, one first needs to
develop a comprehensive picture of the physical and chemical conditions in protoplanetary disks.
We present recent work in combining thermal-chemical models of protoplanetary disks around T
Tauri stars with a molecular non-LTE radiative transfer program to investigate the diagnostic
potential of the infrared lines of water.

Thomas Preibisch New observational constraints on the formation of massive stars from infrared interferometry oral
Long-baseline infrared interferometry can provide very high
angular resolution of up to 1 milli-arcsecond,
what translates to linear dimensions of less than 1 AU
for nearby young stellar objects. This allows to spatially resolve
the inner circumstellar regions of young stellar objects
and to directly study the regions where matter is accreted onto the star
and where jets and outflows are launched and collimated.
With spectrally dispersed interferometric observations
it is now possible to distinguish gas and dust, and thus to
derive important information about the spatial distribution
of each of the different constituents of the disks.

In this talk I will discuss recent results from infrared
interferometric observations of massive young stellar objects.
I will specifically address the issues of
the spatial distribution of inner circumstellar gas and dust.
I will also deal with the multiplicity
of young massive stars. Infrared interferometry is uniquely
well suited to fill the ``observational gap\'\' between
very close spectroscopic companions on the one side,
and the wide companions detectable by adaptive optics and
speckle observations on the other side.
This can provide a comprehensive picture of stellar multiplicity
which holds important information about the star formation process.

Javier A. Rodon The CMF of Massive Star-Forming Regions poster
When observing at spatial scales on the order of ~0.1 AU, it is found that the Core Mass Function of massive star-forming (MSF) regions is similar to the high-mass end of the Salpeter stellar IMF, strongly suggesting that the IMF is set at the moment of the fragmentation of the cloud.

We have observed at 1.4 mm with the PdBI and SMA several MSF regions at ~2 kpc with a spatial resolution of 0.01 pc (~2000 AU), and derived their CMF.
For one of the regions we indeed find a CMF with a slope of -2.3, comparable to the Salpeter value for the IMF, however for the other regions the slope of their CMF is -1.5, comparable to the Clump Mass Function derived for molecular clouds at larger scales.

The regions are similar in luminosity and distance, and we detect a similar number of cores in each region. Why are the CMFs so different then? We discuss probable causes, among them a possible evolutionary effect, and what observations and/or numerical simulations would be needed to test our hypotheses.
Vojtěch Sidorin Dusty H I Shells oral
CONTEXT. The interstellar medium in galaxies is a turbulent environment with a plethora of holes, bubbles and shells. All these shell-like structures are thought to be closely related to the formation, evolution and death of stars. In most cases, they are likely created by the winds of OB stars and supernovae. The material collected along the borders of shells may fragment, become unstable under its own gravity and create a new generation of stars. This is a variant of triggered star formation referred to as the collect-and-collapse scenario.

TALK. I will briefly overview the current knowledge of shells, i.e. the observation of shells, the physical models describing them and numerical simulations of shells. Then I will describe our recent and ongoing research.
Rowan J Smith The Simultaneous Formation of Massive Stars and Stellar Clusters oral
We show that massive stars and stellar clusters are formed simultaneously, the global evolution of the forming cluster is what allows the central stars to become massive. We predict that massive star forming clumps, such as those observed in Motte et. al., contract and grow in mass leading to the formation of massive stars. This occurs as mass is continually channeled from large radii onto the central proto-stars, which can become massive through accretion. Using SPH simulations of massive star forming clumps in a Giant Molecular Cloud, we show that clumps are initially diffuse and filamentary, and become more concentrated as they collapse. Simulated interferometry observations of our data provide an explanation as to why young massive star forming regions show more substructure than older ones. The most massive stars in our model are found within the most bound cluster. Most of the mass accreted by the massive stars was originally distributed throughout the clump at low densities, and was later funneled to the star due to global in-fall. Even with radiative feedback no massive pre-stellar cores are formed. The original cores are of intermediate mass and gain their additional mass in the proto-stellar stage. We also find that cores which form low mass stars exist within the volume from which the high mass stars accrete, but are largely unaffected by this process.

Stefanie Walch Ionising fractal clouds oral
Newly born, massive stars significantly effect their surrounding via
winds and the emission of ionising radiation. As the molecular gas in
the vicinity of an O-star is ionised and dispersed, cold gas is also swept
up and compressed in shock layers. Therefore
star formation may be hindered in some places and triggered in others.
Previous work considered the impact of ionising radiation on the
evolution of initially turbulent molecular clouds.
In these simulations, pillar-like structures were carved out of the cloud and
compressional turbulent modes were powered in the cold gas.

As an alternative to turbulent molecular clouds,
we study the ionisation of fractal molecular clouds, and compare
the resulting properties of triggered star and structure formation.
The clouds are fractal down to the thermal Jeans length.
Larson\'s relations are fulfilled in all our setups.
The fully three-dimensional simulations are performed
with the SPH code SEREN and the ionisation is followed
with a HEALPix based method.
We discuss fundamental differences induced by the intrinsic structure
of the parental molecular cloud.

Carsten Weidner On the relation between the most-massive star and the star cluster mass oral
Whether or not massive stars can be born in isolation or only in star clusters is an important question in the research of star formation. Here we address this issue by studying the most-massive stars found in star clusters. We test if the distribution of these most-massive stars with the mass of their parental cluster is consistent with them being randomly drawn from the stellar initial mass function (IMF) or not as an observational relation which is in agreement with random sampling would be expected if the formation of massive stars is independent of their environment. As the observations seem to rule out random drawing from an universal IMF we conclude that massive star formation is inseparably linked to star cluster formation.
Anthony Peter Whitworth Fragmentation of discs around massive stars oral
I will review the circumstances under which discs around massive stars fragment to produce companions.
Elaine Winston Spitzer and Chandra Observations of RCW 38 oral
I will present preliminary results of Spitzer IRAC and Chandra ACIS-I observations of the RCW 38 starforming region, which lies at a distance of 1.7 kpc. We have identified ~650 YSOs, from Class 0/I to Class III in the extended cluster field, with ~220 of these young stars associated with a Chandra X-ray detection.
Richard Wunsch Pressure assisted gravitational instability of the Expanding Shell oral
We develop an analytical model of the gravitational
fragmentation of a thick expanding shell embedded in
gas with non-zero pressure. The new model is in very
good agreement with AMR and SPH hydrodynamic simulations,
which are in excellent agreement with each other.
However, the new model (and the simulations) do not agree
with a simpler model of the gravitational instability based
on the thin shell approximation. The new model of the thick
shell instability predicts growth of larger wavelengths in
the low pressure ambient medium and hence a top-heavy
clump mass function in such an environment.