LAMOST sky survey for the structure of the Milky Way galaxy
Main Colloquium
Prof. Licai Deng
ORATED
National Asyronomical Observatories, Beijing
The Chinese key scientific project, LAMOST, has concluded its
construction phase, and is now under going technical commissioning. This
is a dedicated survey facility which will carry out a full sky spectral
survey of stellar and galactic source. Scientific program of LAMOST will
be started in 1 year or 2 from now. LAMOST is a reflecting telescope
with a horizontal layout, aperture diameter 3.6-4.8 m, field of view of
20 square degrees and 4000 fibers evenly distributed on the focal plane
of 1.75m, with each fiber driven by 2 independent motors. In this talk,
I will cover instrument specifications, site conditions, scientific
potential in Galactic structure studies, as well as the latest status of
the project.
High Resolution Studies of AGN - A radio flare in CTA 102 as test of shock-in-jet model
Special Colloquium
Christian M. Fromm
ORATED
MPIfR
We test the shock-in-jet model and the hypothesis of an over-pressured
jet on the historical 2006 radio flare in CTA 102. For our analysis we
used single-dish observations as well as three multi-frequency VLBI
observations. From the light curve analysis we can identify the three
different radiation loss stages, where the synchrotron stages shows a
unexpected double peak structure. The evolution of the spectral
parameters along the jet during the flaring event are extracted from
VLBI observations and confirm our assumed model. The double peak
structure can be explained by a change in the viewing angle and leads to
a Doppler boosting of the flux densities around 2006.1.
Dust polarization and magnetic field in high mass star formation - arcsecond view
Special Colloquium
Dr. Ya-Wen Tang
ORATED
Academia Sinica, Astronomy and Astrophysics, Taiwan
Magnetic fields in star formation process are always been invoked to
explain the slow process of star formation, to explain the low formation
rate, and to transfer the angular momentum outward in the accretion
disk. However, it is difficult to trace the B field strength and
geometries of field lines due to its weak signal. Polarized emission
from dust grains can be used to study the B field in the plane of sky.
The emission at mm and submm wavelengths is optically thin and
therefore, is good to trace the dense regions. With the capabilities of
current functioning interferometers SMA, we have studied the B field
geometries in several massive star formation regions. High angular
resolution B field maps are important when studying the role of the B
field in the star forming cores. To analyze the role of B field, we also
need to know the knematics of the molecularcloud and to link the field
geometry with larger scale field. The role of B field varies with the
evolutionary stages of the cetral stars and also with size scales of
interest. In this talk, I will present our case studies toward three
massive star forming regions.
Chemical modelling of dark cores and its application to star formation
Main Colloquium
Dr. Julia Roberts
ORATED
Centro de Astrobiologia, Madrid
The early stages of star formation are extremely difficult to observe
because they occur hidden inside dense, dark molecular cores. Chemical
models are useful tools for probing the physical conditions and
processes occurring inside such cores. A full understanding of the
chemical network can allow us to predict time dependent chemical
abundance profiles of dark cores, as well as predicting molecules which
can act as tracers for various physical processes. In this talk I will
give an introduction to the chemistry of dark cores, and show the
results of a recent project investigating the possibility of using
chemistry to diagnose different models of core collapse.
Formaldehyde Masers in the Galaxy
Main Colloquium
Prof. Peter Hofner
ORATED
New Mexico Tech & NRAO, Socorro, NM, USA
Formaldehyde (H2CO) is one of the most abundant insterstellar molecules
and is easily detected across the Galaxy in absorption against galactic
and extragalactic continuum sources. Maser action in this molecule was
detected in 1974 with the 100m Effelsberg telescope, and despite a
number of dedicated searches in subsequent decades only 2 more sources
were discovered until recently. In this talk I will describe our search
campaigns for new H2CO masers which lead to the discovery of 6 new
sources since 2004. In the second part of the talk I will focus on the
source IRAS18566+0408 in which we have discovered periodic bursts of the
H2CO maser.
Puzzles of the microwave sky
Main Colloquium
Dr. Dominik Schwarz
ORATED
Universität Bielefeld
While observations of the cosmic microwave sky confirm the so-called
concordance model of cosmology on small and intermediate angular scales,
there seems to be disagreement at the largest scales. The microwave sky
is uncorrelated at scales above 60 deg, contrary to expectations for a
dark energy dominated universe. On top of that, the quadrupole and
octopole seem to be aligned with the orientation and motion of the solar
system. The origin of these anomalies remains a puzzle, some attempts to
resolve this puzzle are presented.
The space distribution of nearby star-formation
Special Colloquium
Prof. Laurent Loinard
ORATED
Using the excellent astrometry capabilities of the Very Long Baseline
Array, we have measured the trigonometric parallax (and the proper
motions) of a number of young stars in several nearby star-forming
regions with an accuracy better than a few percents. This represents an
improvement by one or two orders of magnitude over previous
determinations. In particular, we have found that the distance to the
core of Ophiuchus is 120pm4.5 pc, and we have confirmed that the mean
distance to Taurus is 140 pc. Our data also allows us to obtain a rough
determination of the 3D structure of the regions under study. In the
case of Taurus, we have shown that the total extent of the complex along
the line of sight is about 30 pc, the eastern portion being on the far
side and the region around L1495 on the near side. In this talk, after
presenting the results themselves, I will describe several new
constraints for the formation and early evolution of stars that these
data provide, focusing in particular on pre-main sequence evolutionary
models. I will end my talk by mentioning preliminary results in other
regions (particularly Serpens and Cepheus), as well as longer-term
prospects.
Galactic dynamos and magnetic helicity fluxes.
Special Colloquium
Dr. Sharanya Sur
ORATED
ITA, Heidelberg University
Conservation of magnetic helciity is regarded as a key constraint in the
evolution of large-scale magnetic fields. One of the consequences of
helicity conservation is that, it leads to a suppression of large-scale
dynamo action due to the current helicity of the growing small-scale
field. The suppression is catastrophic in the sense that the large-scale
field is quenched to negligible values well before it can be amplified
to observable strengths. Helicity fluxes across the boundaries of the
disc has been identified as a possible mechanism to shed small-scale
magnetic helciity and prevent such a quenching. The speaker will discuss
a simple semi-analytical model of nonlinear mean-field galactic dynamos
incorporating magnetic helciity fluxes. The simplicity of the model
allows for a deeper insight into the role and interaction of various
mechanisms and also helps to extensively explore the parameter space.
The efficiency of the galactic dynamo action facilitated by helicity
fluxes will be demonstrated.
The Expanded Very Large Array
Special Colloquium
Dr. Rick Perley
ORATED
NRAO, Socorro
The EVLA project is a $90M upgrade of the Very Large Array which will
multiply its scientific capabilities tenfold or more. Begun in 2000, the
project is now nearing completion – on time, on spec, and on budget. All
antennas will be upgraded to modern standards by mid-2010, the new WIDAR
correlator will replace the old correlator in early 2010, and all
receiver installations will be completed by the end of 2012. These
upgrades will provide scientists with complete frequency coverage from 1
to 50 GHz, combined with unprecedented sensitivity and flexibility. In
this talk I will review the status of the project and the unique
observational capabilities that the EVLA will soon offer. A subset of
these new capabilities will be available to all observers, beginning
early in 2010 via the nascent OSRO and RSRO programs, which I will
describe in detail. The array’s capabilities will rapidly rise over the
following two years, following a growth path that is now being defined,
and which depends to some extent on user-defined priorities.
Inefficient accretion: The hidden power in our universe?
Main Colloquium
Elmar Koerding
ORATED
MPIfR
Accretion can be the most efficient source of energy in the universe,
powering Quasars as well as X-ray binaires (XRBs) and also Gamma-ray
bursts. While the bright representatives can be highly spectacular, the
vast majority of accreting sources show very low accretion rates. In
theses sources one assumes that the accretion is happening
inefficiently, making their accretion flow dim and hard to detect.
However, most of those sources do show strong jets. I will discuss the
evidence we have for such inefficient accretion first in XRBs and then
in Active Galactic Nuclei. I will show that the kinetic power
originating in the jet dominates the total power output in most cases
and the cumulative power may exceed those of the strongly accreting
objects. Scaling relations between sources of different mass will be
discussed as well as their applications.
Chemical Evolution from Pre-Stellar Cores to Circumstellar Disks
Special Colloquium
Dr. Ruud Visser
ORATED
Leiden Observatory
The chemical composition of a molecular cloud changes dramatically as it
collapses to form a low-mass protostar and circumstellar disk. Spherical
models have always been used to model this chemical evolution, but they
cannot describe the disk. I will present the first model that follows
the entire chemical evolution from a pre-stellar core to a circumstellar
disk in two dimensions. The model enables us to compute where the
material accretes onto the disk (close to the star or far out) and how
this affects the abundances of various key species. I will compare the
model results to observational data. I will also discuss several
applications of the model, such as the chemical origin of cometary
material and the crystalline fraction of circumstellar silicate dust.
Status of the Sardinia Radio Telescope Project
Special Colloquium
Dr. Alessandro Navarrini
ORATED
Cagliari Astronomy Observatory, Italy
The Sardinia Radio Telescope (SRT) is a new general purpose, fully
steerable 64 m diameter radiotelescope which will be capable to operate
with high efficiency in the 0.3-116 GHz frequency range. The telescope
is being built in the Sardinia island, Italy, and its completion is only
few months away. The instrument is the result of a scientific and
technical collaboration among three Structures of the Italian National
Institute for Astrophysics (INAF). The radio telescope has a shaped
Gregorian configuration with a 7.9 m diameter secondary mirror and
supplementary Beam-WaveGuide (BWG) mirrors. With four possible focal
positions (primary, Gregorian, and two BWGs), SRT will be able to
allocate up to 20 remotely controllable wideband receivers. One of the
most advanced technical features of the SRT is the active surface: the
primary mirror will be composed by 1008 panels supported by digitally
controlled electromechanical actuators to compensate for gravitational
and thermal deformations. The status of the project will be presented.
Massive Star Formation in the Central Molecular Zone
Special Colloquium
Katharina Immer
ORATED
MIPfR Bonn
Since the centre of the Milky Way has a distance of only 8.5 kpc, it is
one of the nearest locations to study massive star formation under the
extreme conditions of galactic nuclei. The temperatures as well as the
densities in the molecular clouds in the central molecular zone (CMZ)
are very high. Furthermore, the clouds are exposed to strong tidal
fields that can overcome the self-gravitation of the clouds. This raises
the question if star formation in the CMZ is enhanced or hindered. I
will present results of a multi-wavelengths study of massive star
formation in the CMZ. The study is based on data from the
Spitzer/GLIMPSE, MSX, and ATLASGAL programmes and a VLA survey at 1.4
GHz and results in a classification of the detected star forming regions
according to their evolutionary stages. Furthermore, I will focus on a
particular region of the CMZ, the so called Galactic Centre Dust Ridge.
This region is located at a projected distance of 70 pc from the
Galactic Centre and contains very massive dust clouds. I will discuss
the star formation activity in this region.
Massive Galaxy and Black Hole Formation back to within 1 Billion Years after the Big Bang
Main Colloquium
Dominik Riechers
ORATED
MPIfR
I will present a study of the kinematics, star formation and cold gas
properties of the highest redshift, most intensely star-forming galaxies
with the (Expanded) Very Large Array, the Plateau de Bure
Interferometer, and CARMA. Such detailed investigations are vital for
our understanding of the formation and evolution of massive galaxies in
the early universe. Molecular gas is the prerequisite material for star
formation to occur. Also, gas dynamics can be used to trace the
gravitational potential of galaxies, and thus, to obtain an independent
estimate of the total mass in their central few kiloparsecs. Measuring
the gas fraction is important to determine the evolutionary state of a
galaxy, and to constrain gas depletion timescales and starburst
lifetimes. The morphology and kinematics of the cold gas can also
provide direct insight on the dominant mechanism responsible for the
stellar buildup of these systems (i.e., major mergers vs. secular
evolution). Determining the stellar and total mass of distant galaxies
is important to investigate whether or not the (in the nearby universe)
linear relation between stellar mass and black hole mass in early-type
galaxies evolves with cosmic time and/or toward the high mass end. Such
studies thus set the pace for future investigations of star formation
and galaxy assembly out to the first galaxies that form in the universe,
which will facilitate the capabilities of the upcoming Atacama Large
(sub-)Millimeter Array (ALMA).
Properties of prestellar cores: cosmic ray ionization and non-LTE effects
Special Colloquium
Marco Padovani
ORATED
Arcetri
This talk is in two parts. In the first, I will present the results of a
calculation of the cosmic-ray ionization rate and heating rate in a
cloud of molecular hydrogen as function of the depth inside the cloud
for different assumption on the incident cosmic-ray electron and proton
spectra. In the second part I will show the results of a study of the
abundance of C2H in prestellar cores, addressing in particular the
non-LTE behaviour of the N=1-0 and N=2-1 transitions of this molecule.
Based on these results, we compute improved rest frequencies and
spectroscopic constants for C2H and its potential as a magnetic field
probe.
MOND + 11eV sterile neutrinos: two wrongs do make a right`
Main Colloquium
Dr. Garry Angus
ORATED
University of Turino
For more than 25 years Milgrom’s Modified Newtonian Dynamics (MOND) has
provided a stubborn alternative to dark matter in galaxies. However,
even the fondest supporter must acknowledge how badly MOND fails to
explain the dark matter in clusters of galaxies, and how much easier it
is to explain the acoustic peaks of the cosmic microwave background with
dark matter (as well as forming cosmic structure). Here I show that the
simplest solution to all these problems comes in the form of an 11eV
sterile neutrino, which was chosen to fit the CMB, but leads to some
remarkable coincidences in the dark halos of galaxy clusters.
Additionally I show the results from the Jeans analysis of the dwarf
spheroidals of the Milky Way, which given their correlated positions
around the Galaxy (possible tidal dwarf galaxies Kroupa, Theis & Boily
2005), make them one of the strongest motivations for MOND.
Magnetic fields in the post-recombination universe
Main Colloquium
Dr. Dominik Schleicher
ORATED
ALMA center Leiden
Magnetic fields appear ubiquitous in the local universe, and even normal
galaxies at z=4 appear to have magnetic fields similar to the Milky Way.
>From the epoch of recombination, an upper limit of 3 nG (comoving)
exists from CMB measurements, but no direct measurement. The evolution
between z=1100 and z=4 is therefore unclear. I will discuss the main
scenarios concerning the generation of primordial fields and their
further evolution, as well as their implications on the
post-recombination era, the epoch of reionization and the formation of
the first stars. As most of the gas is neutral at these early times, a
non-ideal MHD treatment is required that takes into account the
implications of magnetic energy dissipation via ambipolar diffusion,
which may have profound implications for the chemical and thermal
evolution of the gas. The increased thermal and magnetic pressure may
delay the onset of reionization. Future radio telescopes like LOFAR or
SKA can probe such scenarios in more detail by measuring the 21 cm power
spectrum during the reionization epoch.
Studying Milky Way Galaxy with VLBI - from VERA to sub-mm VLBI
Main Colloquium
Dr. Mareki Honma
ORATED
NAOJ, Tokyo
I review our current activities at NAOJ to study Milky Way Galaxy with
VLBI observations. First I will summarize the current status of VERA
(VLBI Exploration of Radio Astrometry), which is a dedicated VLBI array
to conduct high precision astrometry of Galactic maser sources such as
star-forming regions and late-type stars. So far we have measured
parallaxes and proper motions of about 20 maser sources and I will
present some high lights of recent VERA’s outputs. In the second part of
my talk, I will introduce our plan toward sub-mm VLBI observations using
ASTE (Atacama Submillimeter Telescope Experiment) to directly image a
black hole shadow of Sgr A*, the super-massive black hole at the Galaxy
center, in collaboration with an international sub-mm VLBI array.
Black holes in the universe and the quest for microquasars
Main Colloquium
Dr. Felix Mirabel
ORATED
ESO, Chile
I will review the three astrophysical manifestations of black holes:
AGN/quasars, microquasars, and gamma-ray burst of long duration. Then, I
shall discuss the physical analogies among black holes of all mass
scales, the observed coupling between accretion-disk-instabilities and
relativistic ejections, and the open questions in this area of research.
The formation of massive stars
Main Colloquium
Dr. Francesco Fontani
ORATED
University of Geneva
High-mass stars (M>8Msun) play a fundamental role in the morphology and
evolution of galaxies. Despite this, the processes that lead to the
formation of massive stars are still poorly understood: large distances,
short evolutionary timescales and clustered formation make observations
of these processes challenging. In this talk, I will present some
observational studies aimed at understanding the initial conditions
required to form massive stars. I will also show the recent results of
an extensive search for massive protostellar objects in our Galaxy, and
how the new generation of instruments, specifically ALMA and Herschel,
will improve this study.
When do you think it will all become clear?: Tracing the evolution of high-mass star formation regions with masers
Main Colloquium
Dr. Simon Ellingsen
ORATED
University of Tasmania, Australia
The formation of high-mass stars is an important, yet poorly understood
aspect of modern astrophysics. High-mass stars play a pivotal role in
Galaxy evolution through their energy input and feedback mechanisms;
however critical aspects of their evolutionary development remain a
mystery, as they occur while they are enshrouded in dust and
gas.Interstellar masers from a number of different molecular species and
transitions are common in the vicinity of young high-mass stars. They
are widely used as signposts of high-mass star formation and sometimes
to trace the kinematics.
The combination of large-scale maser searches (e.g. Methanol Multibeam
survey, HOPS) with Galactic plane surveys in the mid-infrared -
submillimetre (e.g. GLIMPSE, ATLASGAL) is producing exciting new
results. We are for the first time able to investigate the relationship
between the physical properties of the high-mass star formation regions
and the associated masers for large samples of sources. A qualitative
evolutionary timeline for the major maser transitions was first put
forward several years ago. I will outline recent progress towards
testing and quantifying this timeline and how it fits within the broader
picture of high-mass star formation.
HOPS: The H2O Southern Galactic Plane Survey
Main Colloquium
Dr. Andrew Walsh
ORATED
Department of Physics and Astronomy, Curtin University, Perth
Recent upgrades to the Mopra radiotelescope in Australia allow us to
conduct large-scale surveys in many spectral lines simultaneously. I
will describe an ongoing major project, HOPS, which is a survey of the
southern Galactic plane at 12mm. We have so far covered nearly 60 square
degrees of the Galactic plane and have detected 368 water masers, most
of which are new. I will also report on detected emission in ammonia,
methanol, cyanoacetylene and radio recombination lines.
Universality of galactic surface densities within dark halo cores: clues to the nature of dark matter?
Main Colloquium
Dr. Benoit Famaey
ORATED
Universite libre de Bruxelles
The universality of the mean dark matter surface density within one dark
halo core radius is known to hold for galaxies spanning a luminosity
range of 14 magnitudes and the whole Hubble sequence. We show that a
similar relation exists for the baryonic matter, namely that the mean
baryonic surface density is also universal within the halo core radius.
This means that the gravitational acceleration generated by the baryonic
component in galaxies is always the same at this radius. While the total
baryonic-to-dark matter ratio is not universal in galaxies, our result,
together with the universality of the dark matter surface density,
implies that the baryonic-to-dark matter ratio is universal inside the
halo core radius. We show that our finding can be interpreted as a close
correlation between the enclosed surface densities of - and thus the
gravitational accelerations generated by - baryonic and dark matter in
galaxies. This argues in favor of a key and mysterious role played by
the interactions between baryonic and dark matter in the process of
galaxy formation and evolution, or even in favor of modified gravity.
The first 20 Myrs of young dense clusters
Main Colloquium
Prof. Dr. Susanne Pfalzner
ORATED
MPIfR
Most stars are not born in isolation but as part of a cluster. It will
be shown that during the first 20 Myr the cluster environment influences
fundamentally star and planet formation. It will be demonstrated that
massive clusters do not exist in a multitude of sizes and densities, but
only in two distinct types - starburst and leaky clusters.These cluster
types develop along well defined tracks in the density-radius plane.
This means that most stars develop in well defined specific cluster
environments.
Compact Star Cluster Survey in M31 Disk
Main Colloquium
Prof. Keiichi Kodaira
ORATED
JSPS
The 8m Telescope “SUBARU” on Mauna Kea, Hawaii, has a special feature
among the telescopes of this class, namely, the prime-focus camera,
“Suprime-Cam”, which can cover a field of almost the moon-size with
an instrumental seeing of 0.2 arcsec. During the verification period of
this camera we obtained high-resolution images of the south-west part of
the M31 disk (500 square-arcminutes). Using these images, a full-field
search for compact non-stellar objects with apparent size less than
3arcsec (corresponding to about 10pc) was carried out, to identify about
300 candidates for compact star clusters. They looked similar to
globular star clusters but some with little irregularities, and included
many blue objects of B-V<0.5. After closer inspections we selected 238
highly-probable candidates for compact star clusters (V<20.5mag) and
performed an accurate surface-photometric study. The calibrated UBVRI
data were applied to derive cluster parameters related to structure,
age, mass, metallicity, and interstellar extinction. The outcome of
this study indicates that there are abundant star clusters which have
the intermediate properties between the open clusters and the globular
clusters well known in our Galaxy, bridging between the two populations.
Their spatial distribution on the M31 disk shows loose connection to
24micron hot cloud arms/rings. Whether this new population of clusters
identified in M31 disk does also exist or not in our Galaxy disk, is
still an open question. These clusters might be a powerful tool to
elucidate the evolution history of galaxy disks.
Detection of Gravitational Waves with Pulsar Timing
Main Colloquium
Dr. Dick Manchester
ORATED
ATNF, CSIRO, Sydney, Australia
One of the major goals of current astrophysics is the detection and
study of gravitational waves (GW). Millisecond pulsars are very precise
clocks and the tiny period perturbations resulting from GW passing over
the Earth can in principle be detected. Such a detection requires
precision timing over several years of many pulsars spread across the
celestial sphere, a so-called “Pulsar Timing Array” (PTA). PTAs are
sensitive to GW with frequencies in the nHz range and hence are
complementary to ground- and space-based laser-interferometer systems
which are sensitive to much higher frequencies. The Parkes Pulsar Timing
Array (PPTA) is a collaborative project with principal partners
Swinburne University, the University of Texas (Brownsville) and the
ATNF. The project commenced in 2004 and is making regular timing
observations of 20 millisecond pulsars using the Parkes 64-m radio
telescope at three frequencies, 680 MHz, 1400 MHz and 3100 MHz. To
achieve our goals, a data span of at least five years with timing
precisions of order 100 ns for a majority of the sample is required. We
have attained this level of precision or better for several pulsars, but
further improvements are required and considerable effort is going into
improving instrumentation and data analysis procedures. International
collaborations, particularly with the US NANOGrav project and the
European Pulsar Timing Array project, are being established to help us
reach our goals. Future prospects for PTA projects, especially in the
SKA era, are described.
Finding the Gas that makes Galaxies
Special Colloquium
Prof. Art Wolfe
ORATED
University of California, San Diego
Damped Lyman-alpha absorption systems (DLAs) are a population of gas
layers that dominates the neutral-gas content of the Universe in the
redshift interval z=[0,5] and serves as neutral-gas reservoirs for star
formation in early galaxies. In the redshift interval z=[2.5,3.5] the
DLAs cover 1/3 the sky and determine the comoving mass density that
decreases by a factor of 2 with decreasing redshift. However, our recent
measurement of the column-density distribution function and a our search
for low surface-brightness galaxies in the Hubble Ultra Deep field
reveal little evidence for in situ star formation in the DLA gas. I
discuss possible solutions to this paradox. Finally, I discuss results
of a recent study of a DLA exhibiting 21 cm absorption.
Optical polarimetry toward the Pipe nebula: Revealing the importance of the magnetic field
Special Colloquium
Dr. Felipe de Oliveira Alves
ORATED
Institut de Ciencies de l'Espai, Barcelona
Magnetic Fields are proposed to play an important role in the formation
and support of self-gravitating clouds and the formation and evolution
of protostars in such clouds. We attempt to understand more precisely
how the Pipe nebula is affected by the magnetic field. We use R-band
linear polarimetry toward the Pipe nebula to investigate the properties
of the polarization accross this dark cloud complex. Mean polarization
vectors show that the magnetic field is locally perpendicular to the
large filamentary structure of the Pipe nebula (the “stem”), indicating
that the global collapse may have been driven along field lines.
Locally, the northwestern end of the nebula (B59 region) is found to
have a low degree of polarization and high dispersion in polarization
angle, while at the other extreme of the cloud (the bowl) we found mean
degrees of polarization as high as 15plane-of-sky field strength was
estimated to vary from about 17 to 65 micro gauss across the cloud. We
propose that three distinct regions exist, which may be related to
different evolutionary stages of the cloud. This idea is supported by
both the polarization properties across the Pipe and the estimated
mass-to-flux ration that varies between approximately super-critical
toward the B59 region and sub-critical inside the bowl.
Variability studies of a sample of intraday variable sources
Special Colloquium
Nicola Marchili
ORATED
MPIfR Bonn
A large number of compact flat-spectrum radio sources shows variability
on time scales from hours to a few days. Several models, both
source-intrinsic and source-extrinsic, have been proposed for explaining
this so-called intraday variability. In case it is caused by
interstellar scintillation (the most popular among the source-extrinsic
interpretations) the characteristic variability time scales are expected
to show an annual modulation. In 2005 a dedicated program for the
systematic monitoring of a sample of intraday variable sources was
started at the Urumqi radio telescope, complemented by occasional
Effelsberg observations. Aim of the project is to investigate the
changes in the variability characteristics of a number of prominent
intraday variable sources, in order to test the predictions of the
interstellar scintillation models. Strong evidence of source-extrinsic
variability is found in 3 out of the 4 best monitored sources of the
sample. However, there are indications that a non-negligible fraction of
the variability may have a local origin, from a medium which is much
closer to us than generally hypothesized - the Earth atmosphere and/or
the interplanetary medium.
Dust evolution in interstellar shocks
Special Colloquium
Dr. Vincent Guillet
ORATED
Institut d'Astrophysique Spatiale, Orsay, France
Shocks in the interstellar medium have a fundamental impact on the dust
that they encounter. The processing of dust by shocks can lead to
changes in the dust-to-gas mass ratio through sputtering and
vaporization, and also to an evolution of the dust size distribution
through the competition between coagulation and shattering in
grain-grain collisions. The presence of dust, and its processing, can
also alter the shock structure and the gas composition.
I will present the results of numerical models that simulate dust
destruction and processing - and the effect of the dust on - shocks in
molecular clouds, for both mono-fluid (J-type) and multi-fluid (C-type)
shocks. I will emphasize the necessity of a detailed modeling of grain
charging and dynamics through the shock in order to determine the impact
of shocks on the dust size distribution, and its feedback on the shock
structure and the evolution of the shocked gas.
The Growth of Astrophysical Understanding
Special Colloquium
Prof. Martin Harwit
ORATED
Auswärtiges wissenschaftliches Mitglied MPIfR (Cornell University)
I investigate the way that way in which our advances in astrophysical
thinking take place. These advances involve a consensus of the community
if they are to become genuinely accepted, and therefore are a product of
how closely that community is knit. They also depend on outside
influences that often determine new directions that further
investigations will take, the rate at which the community may grow, and
other factors. I assemble these features into a portrayal of the
astrophysical community and its workings, to assess the extent to which
our understanding of the Universe may significantly be a social
construct rather than a representation of the Universe that flows
directly, or even uniquely, from the actual structure and evolution of
the Cosmos.
Galaxy Mergers, Ultraluminous Infrared Galaxies, and Quasar Activity
Main Colloquium
Dr. Sylvain Veilleux
ORATED
U. Maryland
Galaxy merging is a key driving force of galaxy evolution. In
hierarchical CDM models of galaxy formation and evolution, merging leads
to the formation of some elliptical galaxies, triggers major starbursts,
and may account for the growth of supermassive black holes and the
formation of quasars. In order to assess quantitatively the physics of
the merger process and its link to elliptical galaxy formation and QSO
activity, we must first understand the details of galaxy merging and its
relationship to starbursts and AGNs in the local universe. Here I
present the recent results from a comprehensive multiwavelength
investigation of the most luminous mergers in the local universe, the
ultraluminous infrared galaxies (ULIRGs) and the quasars. The issues of
the occurrence, importance, and duty cycle of black hole driven nuclear
activity in these objects will be covered along with their host galaxy
properties and the evidence for massive gas flows in and out (past and
present) of their central cores. The implications of these results on
our understanding of ULIRGs and quasars in a cosmological context will
also be addressed.
21-cm absorbers as probe of the physical conditions in the ISM of high-z galaxies
Special Colloquium
Dr. Neeraj Gupta
ORATED
CSIRO, Australia
In this talk I will be presenting the results from our systematic survey
to search for 21-cm absorption in an unbiased sample of strong MgII
systems at intermediate redshifts. This survey has allowed us to
constrain the number per unit redshift of 21-cm absorbers (n21) at
z<1.5. We show that n21 has fallen by a factor 4 from =0.5 to =1.3
and the decrease is most likely due to the evolution of cold neutral
medium filling factor of the galaxies. Based on these results I will
show that a blind search of 21-cm absorbers with upcoming SKA
pathfinders will unearth a large number of 21-cm absorbers at z<1. Such
unbiased surveys will be crucial for probing the physical state of the
interstellar medium of galaxies at intermediate redshifts where most of
the evolution in star-formation rate density takes place.
Neutron Star Dynamics
Main Colloquium
Prof. K. Kokkotas
ORATED
Universität Tuebingen
Neutron stars are promising gravitational waves sources. We will review
the prospects of detecting gravitational waves from newly born and older
neutron stars, we will present some recent results concerning the
rotational instabilities and finally we will show our recent analysis of
the dynamics of magnetars.
A close relation between AGN gamma-ray emission as measured by Fermi and properties of parsec-scale radio jets
Main Colloquium
Dr. Yuri Kovalev
ORATED
NRAO Green Bank and Lebedev Physical Institute, Moscow
A list of 205 bright gamma-ray objects was recently reported using data
from the Large Area Telescope (LAT) on board the Fermi Gamma-Ray Space
Telescope. Comparison of the LAT positions with accurate radio positions
of a VLBI-selected sample of extragalactic jets finds a total of 112
radio – gamma-ray counterparts including six new associations. Further
comparison of VLBA observations of AGN parsec-scale radio emission with
their associated gamma-ray properties shows that they are closely
related. Fermi-detected radio jets are found to have faster flow
velocities than the non gamma-ray jets, they also appear brighter and
more compact. This suggests that gamma-ray bright AGN have
preferentially higher Doppler boosting factors than other blazar jets.
The correlations found between the temporal radio and gamma-ray
variability suggest that the prominent flares in both bands are produced
in the parsec-scale cores, typically within an apparent time separation
of up to a few months. These results indicate that relativistic beaming
of the jet emission is important in both the radio and gamma-ray bands.
Massive Stars: Evolution and Nucleosynthesis
Special Colloquium
Dr. Raphael Hirschi
ORATED
Keele University, UK
TBA
Early stages of massive star formation: a challenge for observations
Main Colloquium
Silvia Leurini
ORATED
MPIfR Bonn
Despite their importance, our current understanding of the formation of
high mass stars remains very schematic. In this talk, I will briefly
review our knowledge of the process of massive star formation. I will
discuss a few observational tests that may help discriminate between
different models of massive star formation with emphasis to the
importance of studies of very early evolutionary phases. As a case
study, I will present observations of the southern region G351.78-0.54,
which we intensively studied at mm and IR wavelengths in the last years.
The region shows signs of on-going massive star formation towards a
bright IRAS source, and evidence of earlier evolutionary phases of star
formation in several clumps along a dust filament. I will also discuss
interferometric observations towards the most evolved source in the
filament, which nicely outline the complexity of massive star forming
regions and the limitation of current facilities to properly investigate
them.
Current Activities at the NRAO
Special Colloquium
Prof. Fred Lo
ORATED
NRAO
I will give a status report on the science, construction and operations
activities at the NRAO, including an update on the Megamaser Cosmology
Project.
Cosmic-Ray driven dynamo in galactic disks
Main Colloquium
Dr. Michal Hanasz
ORATED
Nicolaus Copernicus University, Torun, Poland
I am going to present recent developments of local and global,
galactic-scale numerical models, of the Cosmic-Ray driven dynamo, which
was originally proposed by Parker (1992). We conduct a series of direct
CR-MHD numerical simulations of the dynamics of interstellar medium,
composed of gas, magnetic-field, and cosmic-ray components. We take into
account cosmic rays, accelerated in randomly distributed supernova
remnants, and assume that supernovae deposit small-scale, randomly
oriented, dipolar magnetic-fields into the ISM. We find that, the
magnetization of galactic disks by exploding magnetized stars forms a
favourable initial condition for the galactic dynamo process. The
amplification timescale of the large-scale magnetic field, resulting
from the CR-driven dynamo, is comparable to the galactic rotation
period. The process converts efficiently small-scale magnetic fields of
SN-remnants into the galactic-scale magnetic fields. The resulting
magnetic-field structure resembles the observed X-shaped magnetic fields
in edge-on galaxies.
Radio Properties of Brightest Cluster Members (BCMs)
Special Colloquium
Prof. Heinz Andernach
ORATED
University of Guanajuato
From the Abell catalog of rich clusters of galaxies we selected a
subsample of 1207 clusters likely to have a dominant galaxy, namely
those with Bautz-Morgan type I and I-II, with Rood-Sastry type “cD”, and
those with textual notes in the Abell catalog hinting at the presence of
galaxies with “coronae”. Our visual inspection of this cluster sample on
DSS images (Coziol et al. 2009) yielded 1423 candidates for brightest
cluster members (BCMs) towards 1169 different Abell clusters. We used
the source catalogs and images of existing radio surveys (VLSS, WENSS,
SUMSS, NVSS, FIRST, etc.) as well as the literature to collect radio
fluxes and radio morphologies for these BCMs. Of the 1424 BCMs 590 (41at
more than one frequency, allowing to estimate their radio spectral
index. I present preliminary results of this work in progress, showing
the large variety of radio morphologies including several FR II type
sources rarely found in rich clusters, as well as a few examples of very
radio-quiet BCMs. The intended statistical analysis of the data include
a search for relations between various radio and optical characteristics
of the BCM, like radio luminosity, radio morphology and spectral index,
optical morphology and ellipticity, peculiar velocity within their host
cluster, as well as the radio-optical alignment angle.
Radio interferometry of maser sources in high-mass star forming regions
Special Colloquium
Birgit Ritter
ORATED
MPIfR, Bonn
Still, little is known about the real structure of our Milky Way. It is
known to possess spiral structure, but the number of spiral arms is
still under debate. The main problem is that distance determinations are
difficult since we are located within the plane of the Galaxy. The most
reliable way to determine a distance is the trigonometric parallax,
which is unbiased by any intrinsic source properties. VLBI techniques
enable to measure parallaxes up to distances of several kpc in each
direction. Interstellar maser sources in high-mass star forming regions
(HMSFRs) have proven to be useful targets as they are compact and bright
objects. Currently large projects are undertaken in order to map the
Milky Way by VLBI parallax measurements of such sources. I will present
VLA observations of 6.7 GHz methanol and 22 GHz water maser sources in
HMSFRs that were conducted in order to define accurate phase center
positions for follow-up VLBI parallax measurements. Furthermore I will
describe the VLBA observations of 12.2 GHz methanol masers in the
high-mass star forming region G25.71+0.04 and discuss its location and
proper motion within our Galaxy.
Studying the magnetised ISM with radio polarimetry
Special Colloquium
Dr. Andre Waelkens
ORATED
MPE Graching
The structure and statistics of magnetic fields in the ISM are still
unknown, despite their importance for the regulation of star formation,
cosmic ray propagation, and CMB forground synchrotron emission. Advances
in our knowledge have to come from the interpretation of multi-frequency
data. To this end, I will present a number of probes for properties of
the magnetised ISM on all scales. To study turbulence in the ISM, we
develop an estimator for the magnetic tension-force spectrum. It is
based on polarised synchrotron emission data in the
Faraday-rotation-free frequency regime. The tension force is the
dynamically most important magnetic force in subsonic magnetic
turbulence. The method is applied to mock observations based on MHD
simulations as a prelude to an application to real observations. To
investigate the global Galactic ISM properties we developed the
hammurabi code, capable of producing mock synchrotron, RM, DM and UHECR
deflection observations. Therefore it permits to confront models of the
Galactic magnetised plasma with a broad range of real observations. I
will report on a number of works based on this code, and give an outlook
on future projects I believe hammurabi is suited for.
Quantifying Dark Energy with Cosmic Shear
Main Colloquium
Dr. Sarah Bridle
ORATED
University Colloge London
I will summarise the evidence for dark energy and the basics of cosmic
shear. My talk will then focus on how to obtain the maximum constraining
power from the upcoming experiments to measure dark energy using cosmic
shear. I will introduce the GRavitational lEnsing Accuracy Testing 2008
(GREAT08) Challenge, which is an image analysis competition to improve
shear measurements. I will also describe the potentially confusing
signal from intrinsic galaxy alignments and how it can be addressed.
The Planet-Disc connection
Special Colloquium
Prof. Cathie Clarke
ORATED
Cambridge
TBA
The DiFX software correlator in Bonn
Special Colloquium
John Morgan
ORATED
Bologna
Software correlators allow correlation to be done on standard computer
clusters rather than custom hardware. Progress has been rapid in recent
years and many VLBI “hardware correlators” are being switched off to
make way for more flexible software correlators. DiFX [1] is one such
software correlator whose use is being investigated by several
institutes including MPIfR.
In this talk I will give a brief introduction of software correlators,
followed by an overview of the work being carried out here with
particular focus on using DiFX for widefield VLBI and adapting DiFX for
geodetic use. I will conclude by discussing new possibilities that
software correlation offers astronomers.
[1] Deller, Tingay, Bailes & West 2006, PASP, 119, 318
Principal Component Analysis of Molecular Line Observations of Massive Star-Forming Clumps
Special Colloquium
Adam Fallon
ORATED
MPIfR, Bonn
Principal component analysis (PCA) is a tool from multivariate
statistics used to find the directions which account for the most
variance in a data set. Such tools are of interest in astronomy due to
the availability of increasingly large data sets. In this work PCA was
applied to three main data types derived from molecular spectra of
massive star-forming regions: integrated intensities, spatial maps of
integrated intensities, and molecular line velocities, with the goal of
assessing the usefulness of PCA in finding a simplified description of
the data, and to learn if any physical insights were possible from this
process. In the integrated intensity sample it was found that PCA does
separate the sources into groups with distinct characteristics, and
therefore has potential as a source classification aid. The results from
the map and molecular line velocity samples were less notable, however
some technical observations regarding the influence of noise and
artifacts were made.
Science with the Austrailan Square Kilometre Array Pathfinder
Main Colloquium
Dr. Simon Johnston
ORATED
ATNF, CSIRO, Sydney, Australia
The future of cm and m-wave astronomy lies with the Square Kilometre
Array (SKA), a telescope under development by a consortium of 17
countries that will be 50 times more sensitive than any existing radio
facility. Most of the key science for the SKA will be addressed through
large-area imaging of the Universe at frequencies from a few hundred MHz
to a few GHz. The Australian SKA Pathfinder is a technology demonstrator
aimed in the mid-frequency range, and achieves instantaneous wide-area
imaging through the development and deployment of phased-array feed
systems on parabolic reflectors. The large field-of-view makes ASKAP an
unprecedented synoptic telescope that will make substantial advances in
SKA key science. ASKAP will be located at the Murchison Radio
Observatory in inland Western Australia, one of the most radio-quiet
locations on the Earth and one of two sites selected by the
international community as a potential location for the SKA. In this
talk, I will outline the ASKAP project and summarise its headline
science goals as defined by the community at large.
An In-depth Study of the Interstellar Medium in the Barred Spiral Galaxy NGC3627
Special Colloquium
Christof Buchbender
ORATED
MPIfR, Bonn
I will present a study of the cold, dense, star forming ISM in the
barred spiral galaxy NGC3627, with the final goal to obtain a spatially
resolved Schmidt-Kennicutt law, which is a power law relation between
the star formation rate (SFR) and the gas mass surface density. NGC3627
is located in the nearby Leo Triplet with a distance of about 9 Mpc. It
is strongly interacting with its nearest neighbor NGC3628 and as such it
is representative for a large number of galaxies where gravitational
interaction has triggered the formation of a bar and the associated SF
activity along the bar and in the nuclear region. To investigate the
molecular gas in NGC3627 measurements of the CO(1-0) line as well as 1.2
dust continuum emission were used. With these two tracers of molecular
mass at hand it is possible to study local variations of the X-factor,
which relates CO(1-0) intensity to H_2 column density, across the disk
of the galaxy. These observations are complemented by HI, Halpha, and
24,70 and 160 micron Spitzer observations, allowing to determine dust
temperatures, SFRs, and atomic gas masses across the disk of NGC3627.
This comprehensive wavelength coverage provides a good view into the
structure of the different components of the cold ISM in this galaxy.
Apertif, upgrading the WSRT and pathfinder for SKA
Main Colloquium
Dr. Thomas A. Oosterloo
ORATED
ASTRON (Netherlands)
Apertif is a programme aimed to upgrade all dishes of the Westerbork
Synthesis Radio Telescope (WSRT) with focal plane arrays. This will lead
to an improvement of the field of view with a factor 25 and the survey
speed of the WSRT will increase with a similar factor. This will turn
the WSRT into a powerful survey instrument. The technology is also
relevant for SKA. I will discuss the technical aspects of Apertif and
show first results obtained with a prototype focal plane array currently
mounted in one of the WSRT dishes. I will also discuss the science case
for Apertif that is very diverse, including the search for the smallest
galaxies, the evolution of the gas content of galaxies with redshift,
cosmic magnetism as well as pulsars and transients.
MIDI/VLTI-Infrared Interferometry of the young, massive star Allen's Source
Special Colloquium
Rebekka Grellmann
ORATED
MPIfR, Bonn
Allen’s Source is a young star with a mass of 9.5 solar masses,
therefore belonging to the intermediate to high-mass stars. Our
knowledge about the formation of high-mass stars is still very limited.
With a distance of 760 pc Allen’s Source provides the unique possibility
to investigate its circumstellar environment on scales of few AU. With
MIDI, the mid-infrared instrument of ESO’s Very Large Telescope
Interferometer (VLTI), spectral dispersed Michelson interferograms of
Allen’s Source were taken at wavelengths between 8 and 13 micron. For
the interpretation of the data the radiative transfer code DUSTY was
employed to extract physical parameters of a possible circumstellar
envelope. Furthermore, a temperature-gradient model for a possible disk
around the object was tested.
On the ortho-to-para ratio of H2 in dark clouds: from theory to observation
Special Colloquium
Dr. Nicolas Troscompt
ORATED
LAOG, Grenoble
The ortho-to-para ratio (OPR) of molecular hydrogen is a fundamental
parameter to understand the physics and chemistry of the interstellar
medium (ISM). In dark and cold clouds, however, H2 is not directly
observable and the OPR of H2 in these sources has remained so far
elusive. In this talk, I will show that the absorption line of H2CO at
6cm, with resolved hyperfine components, can be employed to estimate the
OPR of H2 in dark clouds. Indeed the excitation temperature of this line
is strongly sensitive to the collisional perturber. I will present 1)
new calculations of rate coefficients for the rotational excitation of
H2CO by both para- and ortho-H2 and 2) new GBT observations and
radiative transfer modelling of H2CO toward dark clouds.
Galaxy clusters, jets, and magnetic fields
Special Colloquium
Dr. Martin Krause
ORATED
MPE Garching
The magnetic field in present day clusters is dominated by a turbulent
component at sub-equipartition with respect to the thermal energy
density, consistent with (sub-)sonic turbulence. Not much is known about
higher redshifts. I will discuss a recent theoretical approach that
incorporates results from magnetohydrodynamic turbulence calculations
into a cosmological simulation, and present model predictions for
magnetic field measurements via Faraday rotation studies with the
upcoming LOFAR telescope and the Square Kilometre Array. An important
ingredient to the physics of galaxy clusters are radio jets. They are
important for the heat balance and possibly metal transport within the
clusters, they interact with cold gas especially at high redshift, which
might be important for galaxy formation, they tell about the central
engine and may enhance the magnetic field in the intra-cluster medium. I
will present magnetohydrodynamics simulations of the interaction of jets
with their environment, with realistic magnetic field configurations in
the jet and also in the ambient cluster gas.
Phenomenological approach to the multi-wavelength study of blazars
Special Colloquium
Dr. Andrea Tramacere
ORATED
SLAC Stanford, ASI-INAF Rome
I will present a phenomenological approach to the multi-wavelength study
of blazar emission. In the first part I will demonstrate how to use
UV/X-ray data to search for signatures of stochastic acceleration
processes in BL Lac (HBL) objects. It will be discussed how these
features can be linked to predict the GeV/TeV emission, and how the
intrinsic spectral curvature is relevant to understand the Extragalactic
Background Light (EBL) issue. In the second part I will discuss the
multi-wavelength emission from flat-spectrum radio quasars in the
framework of the external Compton scenario. I will show how changes in
different physical parameters can account for different patterns in the
spectral evolution. Finally, I will present recent (2008/2009) results
for PKS 1510-089, showing new radio (Effelsberg, F-Gamma project),
opt/UV, X-ray and gamma-ray (Fermi-LAT) observations.
Studying the Nature of Dark Energy with Galaxy Clusters
Special Colloquium
Dr. Thomas Reiprich
ORATED
AIfA
After an introduction how dark energy influences the growth of galaxy
clusters – the most massive collapsed structures in the Universe, I’ll
present the latest results from our X-ray follow-up of a complete local
sample of the 64 X-ray brightest clusters in the sky as well as a nearby
sample of 26 galaxy groups. Multiwavelength (radio, sub-/mm, optical)
properties of the samples as well as the effect of feedback from central
supermassive black holes on cluster atmospheres will also be mentioned.
Furthermore, I’ll report on the status of our optical weak gravitational
lensing follow-up of a complete high-z sample of 40 clusters. The
combination of the samples will be used for robust constraints on the
nature of dark energy through the evolution of the cluster mass function
and merger frequency. Moreover, the usefulness of these high quality
observations for future large X-ray surveys, like eROSITA, will be
discussed.
How much light was produced since the Universe was born? Finally, a way to measure it.
Special Colloquium
Dr. Markos Georganopoulos
ORATED
University of Maryland, Baltimore County, USA
The extragalactic background light (EBL) that permeates the Universe in
the optical-IR is essentially an integral of the light produced from the
time the first stars were formed in our Universe until now. As such, it
is a quantity that is very closely connected to the galaxy/ large scale
structure formation in our Universe. Unfortunately, measuring the EBL
has been proven very difficult, for very simple reasons that I will
discuss in the first part of my talk. Luckily, we found an unexpected,
parameter-free way to break the deadlock of measuring the EBL with
Fermi, NASA’s new Gamma-ray satellite. This will be the second part of
my talk. Fermi measurements are underway and the determination will take
about two years.
The Effect of dense clouds on the SED of disc like galaxies
Special Colloquium
Dr. Joerg Fischera
ORATED
Mt Stromlo Observatory, Australia
The effects of the in-homogeneous density structure of the dusty
interstellar medium (ISM) on the spectral energy distribution (SED) of
disc-like galaxies are analyzed in the approximation of an isothermal
self-gravitating infinite slab with typical scale heights of the ISM and
the stars.
The stellar distribution is divided into a ‘young’ stellar component of
hot stars in the dusty disc and an ‘old’ stellar component of colder
stars with larger scale height. The ISM is described by a two-phase
model of dense self-gravitating clouds which are embedded in an
otherwise homogeneous medium.
The radiative transfer problem is for given central pressure of the ISM,
chosen to be in agreement with the value in the Milky-Way, determined by
the amount of mass in dense clouds relative to the mass in the
inter-cloud medium. In its solution problems of multiple scattering,
non-isotropy of the scattered emission and re-heating of dust grains are
considered. The thermal dust emission is derived using a physical dust
model of stochastically heated grains.
Molecular gas content and star formation modes in high redshift massive galaxies
Main Colloquium
Dr. Emanuele Daddi
ORATED
CEA, Saclay, France
I will present results from our ongoing surveys probing the molecular
gas content of distant galaxies with the IRAM Plateau de Bure
Interferometer and the VLA. We recently discovered that ordinary near-IR
selected galaxies at z>1 are very luminous CO emitters and can be
routinely observed and studied already with existing facilities. We also
unveiled a substantial population of z>4 bright submm galaxies in the
GOODS-N field. Star formation modes in the distant Universe can be
understood in terms of the spiral/ULIRG duality that is well
characterized locally.
Westerbork observations of the Galaxy at 150 MHz: foregrounds for observations of the cosmological 21 cm line
Special Colloquium
Dr. Gianni Bernardi
ORATED
Kapteyn Astronomical Institute, University of Groningen
The detection of the cosmological 21 cm line is a very promising tool to
investigate the reionization epoch, when the first galaxies were born.
However its detection is plagued by strong Galactic and extragalactic
foreground emission. We present results from total intensity and
polarization observations of selected areas in the Galaxy, aimed at
characterizing the foreground properties and we discuss the implications
for the measurement of the cosmological signal.
The APEX southern sky survey of high mass star forming regions
Special Colloquium
Carolin Dedes
ORATED
MPIfR Bonn
In my dissertation, I characterized the physical and chemical properties
of a sample of 47 high mass star forming regions by observing it with
the new Atacama Pathfinder EXperiment (APEX) 12m telescope, and in parts
with the Australia Telescope Compact Array (ATCA). These observations
were done between 86 and 810 GHz in the mm and sub-mm regime, where most
of the high mass star forming activity can be observed. This is the
first study which combines a sub-mm dust continuum and molecular line
survey on a large number of sources, and it resulted in a database of
southern hemisphere sources well suited for follow-up studies with the
high resolution capabilities of the ALMA interferometer. In my talk, I
will give an overview of my dissertation work and discuss in more detail
the density profile fitting of the dust continuum, the derivation of
infall properties for the sample and the chemical analysis of eight hot
cores found in the molecular line data.
What we do not know about galactic magnetic fields and why
Special Colloquium
Dr. Anvar Shukurov
ORATED
University of Newcastle, UK
The focus of this review of galactic magnetic fields is on unresolved
problems. I will make an attempt to isolate the most physically
important problems (the choice, however, remains subjective), briefly
present earlier attempts to solve them, discuss why those attempts have
not been convincing, and suggest what can we gain from solving these
problems. The problems involved range from the dynamics of the
multi-phase interstellar medium, to the disc-halo connections in spiral
galaxies, and their connection to galactic magnetic fields.
The little bang in the laboratory: creating the quark-gluon plasma
Main Colloquium
Prof. Johanna Stachel
ORATED
Physikalisches Institut der Universität Heidelberg
The theory of strong interaction, Quantum Chromo Dynamics (QCD) predicts
that at high temperature and density a new state of matter is created in
which the confinement of quarks and gluons is lifted. This state which
must have existed in the early universe until about 10 microseconds
after the big bang is called the Quark-Gluon Plasma (QGP). Since about
20 years experiments are conducted in the laboratory to recreate this
state of matter. The understanding is that this is done by colliding
heavy atomic nuclei at as high energies as possible. Initially this was
done by bombarding stationary targets with beams at the BNL AGS and the
CERN SPS and in 2000 the evidence mounted that indeed a new state of
matter was created. Since then a dedicated colliding beam accelerator,
RHIC at BNL has come into operation. The results at RHIC give very
strong arguments in favor of the QGP creation but also indicate that the
properties of this state may be quite different from what was initially
expected. This talk will review the experimetal results and give an
outlook to the future experimetal program in this field starting at the
LHC in 2009.
Beaming and de-beaming of relativistic jets: translating observed quantities and appearances into intrinsic ones
Special Colloquium
Dr. Sebastian Jester
ORATED
Fermilab
Relativistic beaming and effects like apparent superluminal motion are
familiar concepts by now, but still hold surprises for our
non-relativistic intuition. In particular, angle aberration has entirely
unfamilar effects on how relativistic objects appear in pictures. I show
that there is a spatial corollary to apparent superluminal motion, which
makes relativistic objects appear longer than they are (in our frame).
As a consequence of this ”retardation magnification”, we cannot see (or
photograph) all parts of a relativistic jet simultaneously. Going from
visualising to quantitative work, there are contradictory de-beaming
formulae for minimum-energy magnetic fields. The contradiction is
resolved by making a clear distinction between varying beaming
parameters for fixed *source* and for fixed *projection*; the latter
corresponds to interpreting astronomical observations.
Radio Wave Propagation as a Probe of the Cosmos
Special Colloquium
Dr. Bryan Gaensler
ORATED
Sydney University
The Universe is largely transparent to radio waves, but this does not
mean that these signals are unaffected by their passage. Substantial
information about otherwise unobservable phenomena is imprinted on radio
waves as they propagate, in forms such as dispersive delays, Faraday
rotation and interstellar scintillation.
I will discuss two studies of these propagation effects, representative
of the incredible diversity of physical processes which can be revealed
by such measurements. First, I will present a new analysis of pulsar
dispersion measures, which demonstrates that the ionized gas layer of
the Milky Way is twice as thick as previously thought. I will then show
how spectropolarimetry of active galactic nuclei can probe deep within
the central engine, and will discuss plans to thus carry out an all-sky
census of merging supermassive black holes.
Funding by COST (European Cooperation in Science and Technology)
Informal Colloquium
Dr. Piotr Swiatek
ORATED
NCP, FZ Juelich
COST is an intergovernmental framework for European Cooperation in
Science and Technology, allowing the coordination of nationally-funded
research on a European level. Financial support is granted for joint
activities such as conferences, short-term scientific exchanges and
publications. COST therefore can be used as a strategic instrument for
preparing new research projects on a multinational level.
The talk is aiming at presenting the COST-Programme and at the same time
giving practical advice and support on how to apply for a COST Action.
The speaker Dr. Piotr Swiatek has long term experience with and insider
knowledge on the COST programme, as he has been working for four years
(2004-2008) as senior science officer in the ”Materials, Physical and
Nanosciences” domain at the COST Office in Brussels.
Funding Opportunities for Postdocs: The Marie Curie Programme of the European Commission
Informal Colloquium
Viola Tegethoff
ORATED
Scientific Officer, MPG Office in Brussels
Are you about to finish your doctorate and are your planning “the time
after”? Or are you already a postdoc seeking for a new challenge in your
early career as scientist?
The Marie Curie Programme of the European Commission is an interesting
alternative to personal funding schemes of e.g. the German Research
Foundation (DFG), as it enables you to move with your own salary and
some extrafunds to a research institute / university in Europe or abroad
(e.g. USA, Australia,...). The programme does not have age limits, so it
can be an interesting option both for young postdocs and experienced
postdocs.
The European Commission will publish the next Call for Proposals on
March 18, 2009 with a deadline on August 18, 2009.
The presentation will inform on the programme itself and especially on
how to prepare a (successful) proposal within the Marie Curie Programme.
The Dark Energy Survey
Special Colloquium
Dr. Brenna Flaugher
ORATED
Fermi National Accelerator Laboratory
The Dark Energy Survey (DES) is a next generation optical survey aimed
at understanding the expansion rate of the universe using four
complementary methods: weak gravitational lensing, galaxy cluster
counts, baryon acoustic oscillations, and Type IA supernovae. To perform
the survey, the DES Collaboration is building the Dark Energy Camera
(DECam), a 3 square degree, 520 Megapixel CCD camera which will be
mounted at the prime focus of the Blanco 4-meter telescope at the Cerro
Tololo Inter-American Observatory. The survey will cover 5000
square-degrees of the southern galactic cap with 5 filters (g, r, i, z,
Y). DECam will be comprised of 74 250 micron thick fully depleted CCDs:
62 2k x 4k CCDs for imaging and 12 2k x 2k CCDs for guiding and focus.
DECam will be used to perform the Dark Energy Survey with 30of the
telescope time over a 5 year period. During the remainder of the time,
DECam will be available as a community instrument. I will present an
overview of the DES science plans and the status of the instrument
construction.
Jets in X-ray binary systems
Main Colloquium
Dr. Valeriu Tudose
ORATED
Sterrenkundig Instituut Anton Pannekoek, University of Amsterdam
An X-ray binary (XRB) is a system comprising a compact object (neutron
star or stellar mass black hole) accreting matter from a companion star
via an accretion disk. In some particular states of this complex system,
matter is ejected from a region close to the compact object in the form
of two opposite, often relativistic jets. Although semi-empirical
qualitative models have recorded notable successes, at the moment it is
not entirely clear what is the exact connection between the accretion
process and the launching of the jets. This is a fundamental question,
going beyond the limits of the galactic studies, since evidence is
mounting that the accretion/ejection process in active galactic nuclei
(AGNs) presents to some degree similar features to XRBs. Equally notable
is that the timescales of the phenomena associated with the XRBs also
allow to study their surrounding environment via the interaction of the
jets with the interstellar medium. From the observational point of view
the best approach to study the XRBs is with quasi-simultaneous
multi-wavelength observations, however logistically speaking such
campaigns are not easy to set up. In the context outlined above, I will
exemplify with results obtained for some particular systems, among which
Cir X-1, Cyg X-3, Aql X-1, SS 433. The focus is primarily on the radio
observations of these objects (with e-EVN, ATCA, VLA), but in some cases
X-ray observations (RXTE, Chandra) and optical (SMARTS) are also
discussed.
Diffuse neutral ISM: temperature and turbulence
Special Colloquium
Dr. Nirupam Roy
ORATED
MPIfR
The thermal equilibrium model shows that different phases of the diffuse
neutral ISM can be in pressure equilibrium in one of the two stable
ranges of kinetic temperature, viz. 40 - 200 K for the CNM and 5000
- 8000 K for the WNM. But, recent observations indicate that a
significant fraction of the neutral ISM is in the thermally unstable
region. The classical method of determining the WNM temperature,
however, provides an upper limit to the temperature because turbulence
contribute to the observed line width. In this talk, I will discuss
about different issues with the classical method of estimating the WNM
temperature and about a possible way to quantify the contribution of
turbulence to the line width. This will allow us to correctly determine
the amount of neutral gas in the unstable state and to critically
re-examine the thermal equilibrium model of the ISM.
The Future of Astronomy from Antarctica
Special Colloquium
Prof. John Storey
ORATED
UNSW Sydney
As our understanding of the unique conditions on the Antarctic plateau
continues to grow, it is becoming clearer which areas of astronomy are
likley to benefit the most from new Antarctic observatories. In the
optical/IR, the combination of clear skies and very low levels of
optical turbulence create unprecedented opportunities for
high-resolution, wide-field imaging and spectrospcopy. In addition,
time-series observations can benefit from the long, uninterrupted
periods of darkness. At terahertz frequencies and into the sub-mm, the
stability of the sky and low precipitable water vapour should allow
routine observations at wavelengths that are difficult or even
unobservable at any other location on the earth’s surface. Concordia
Station at Dome C has now been operating for four years, and just
yesterday the offical opening took place of the new Chinese station,
Kunlun, at Dome A. This talk will review the current state of knowledge
of site conditions, and explore the opportunities presented by Dome C
and Dome A.
Current Status of the Delta Quadrant Survey
Special Colloquium
Dr. Maria Cunningham
ORATED
University of New South Wales, Sydney, Australia
The G333 Survey is a multi-molecular line survey of the G333.6-0.2 giant
molecular cloud complex, motivated by the idea of gaining a
comprehensive picture of massive star formation throughout an entire
GMC. We have used the new broadband capabilities of the Mopra telescope
to map the distribution of around 20 different molecules in this
approximately 1 degree square region of the southern Galactic plane.
In the analysis of this complex data set, we have used two analysis
techniques suitable for application to large data sets, both of which
have yielded interesting results: Spatial Power spectrum and Principal
Component analysis (PCA). We have investigated the spatial power
spectrum of a variety of molecules that trace different critical
densities. Surprisingly, all molecules show a similar power law slope,
suggesting a picture where turbulence is injected at large scales (at
least tens of parsecs), and passes through to smaller scales, and higher
densities, without significant dissipation. The large scale of energy
injection is supported by other analyses, which hint that the initial
wave of star formation in the complex may have been triggered by a
merger between two large-scale Galactic flows. However, the PCA analysis
has shown that, despite the apparently uniform distribution of turbulent
energy through the different molecular regions, different molecules are
well differentiated at smaller scales. The PCA and has yielded some
significant chemical correlations and anti-correlations, which we
compare with model predictions.
The Stromlo Missing Satellites Survey
Main Colloquium
Dr. Helmut Jerjen
ORATED
Research School of Astronomy and Astrophysics, Mt. Stromlo Observatory, Australia
The SMS program is a critical endeavor to investigate whether the
predictions of standard cold dark matter cosmology are consistent with
the observed matter distribution in the Milky Way halo. It is the
deepest, most extended search for optically elusive dwarf satellite
galaxies and tidal streams to date, covering the entire 20,000 square
degrees of the Southern hemisphere. The 150 TB of CCD images in six
photometric bands, 0.5-1.0 mag fainter than the Sloan Digital Sky
Survey, will be produced by the SkyMapper telescope of the Australian
National University over the next five years. The primary objective of
our program is to study the baryonic and dark matter components of the
newly detected stellar overdensities in unprecedented details providing
the best physical picture of the phenomenon ”dwarf satellites” and
stringent empirical constraints to test CDM theory.
The non-ballistic model for the superluminal motion in AGNs
Special Colloquium
Prof. B. Gong
ORATED
Huazhong University, Wuhan, China
The long-term multi-epoch observations of quasars, active galaxies,
tracing the structure further along the jets and following the motion of
individual features for longer time, rise questions that are difficult
to understand by the standard scenario of superluminal motion. I.e., the
ejecta are aligned with the local jet direction, instead of the core;
and within individual jets apparently inward-moving features are
observed. Here we show that these unexpected phenomena actually indicate
the existence of non-ballistic jet motion, in which a continuous jet
produces a discrete hot spot. And the precession of such a hot spot
leads to the superluminal motion in the plane of the sky. The new model
provides a simple and unified interpretation to the superluminal motion
of two AGN sources 0735+178 and 0119+041. And it is expected to apply to
more AGNs.
An Engineer's Astronomers' Guide to the Australian SKA Pathfinder
Main Colloquium
Dr. David DeBoer
ORATED
Seti Institute, USA
Great surveys at all wavelengths are charting our place in the cosmos.
The Australian SKA Pathfinder (ASKAP) will be one of the fastest and
best survey telescopes in the important 700-1800 MHz frequency range and
will trial technology for the SKA. ASKAP will comprise 36 12-meter
antennas, each with a phased array feed yielding a field-of-view of
about 30 square degrees. It is being built in the remote Western
Australia Outback at Australia’s candidate SKA site. This area is being
developed as the Murchison Radio Observatory and is arguably the world’s
best site for cm-wave astronomy. This talk will provide an overview and
status of ASKAP.
Fragmentation of massive star-forming clusters
Special Colloquium
Dr. Javier A. Rodon
ORATED
MPIA Heidelberg
TBA
What can we learn from synthetic emission maps for the jet of M87?
Special Colloquium
Dr. Jose Gracia
ORATED
Dublin Institute for Advanced Studies (DIAS)
We present a self-consistent MHD model for the jet of M87. The model
consist of two distinct zones: an inner relativistic outflow and an
outer cold disk-wind. While the former does not self-collimate
efficiently due to its high effective inertia, the latter fulfils all
the conditions for efficient collimation by the magneto-centrifugal
mechanism. The relativistic flow is thus magnetically confined into a
well collimated beam for a wide range of parameters.
Comparison of observed radiomaps and synthetic synchrotron emission
calculated from the MHD models are used to select a best fitting model
based on constraints on the opening angle and limb-brightening of the
jet. We argue, that the limb-brightening is not an apparent effect, i.e.
Doppler de-boosting into the line-of-sight, but due to an intrinsic
accumulation of magnetic flux at the outer edge of the jet.
Additionally, our model reproduces some of the properties of the
optically bright knot HST-1.
Finally, we line out how linear polarisation measurements in addition to
total intensity can further constrain the topology of the magnetic field
in the jet beam.
Rotational line emission from water in protoplanetary disks
Special Colloquium
Dr. Dieter Poelman
ORATED
University of St. Andrews
One of the most fundamental questions to date in modern astrophysics is
how stars and planets form. Protoplanetary disk evolution and planet
formation are closely entangled. Therefore, to understand their
formation mechanisms, one first needs to develop a comprehensive picture
of the physical and chemical conditions in protoplanetary disks. In this
talk, I will present recent work in combining a thermal-chemical model
of a typical T Tauri star disk with a molecular line radiative transfer
program to investigate the diagnostic potential of the far-infrared
lines of water. I discuss the observability of pure rotational water
lines with the Herschel Space Observatory.
Fast Radiation Transport for Hydrodynamical Simulations of Massive Star Formation
Special Colloquium
Rolf Kuiper
ORATED
MPIA Heidelberg
We investigate the radiation pressure feedback depending on the
morphology of the stellar environment in one-, two-, and
three-dimensional monolithic collapse calculations of massive
pre-stellar cores. In contrast to previous research, we (1) consider
frequency dependent radiation feedback,(2) use a newly developed hybrid
radiation transport scheme, including ray-tracing as well as flux
limited diffusion, (3) resolve the dust sublimation front in the
vicinity of the forming star down to 1.27 AU,(4) compute the whole
accretion phase of the new born star up to several 10^{5} yr, and (5)
perform a comprehensive survey of the parameter space (more than 40
simulations by now).
Our simulations in axial symmetry demonstrate in detail that not
resolving the dust sublimation front artificially terminates the disk
accretion epoch. Our most fundamental result is that the formation of
massive accretion disks enforces a strong anisotropy of the thermal
radiation field, enabling steady accretion through the shielded disk
region. In 3D the self-gravity of the disk drives a sufficiently high
accretion rate to overcome the residual radiation pressure.
Simultaneously, a stable large-scale bipolar outflow is launched due to
radiative forces. Summing up, the various simulation series draw a
consistent picture of the formation of the most massive stars via
classical disk accretion. For an initial pre-stellar core mass of 60,
120, 240, and 480 Msol these mechanisms allow the central star to grow
up to 27, 57, 93, and more than 137 M_odot respectively.