Colloquium 2007.4-2008.3, Dept Astronomy, Kyoto Univ

413
ځFGAMMA-RAY EMISSION FROM THE GALACTIC CENTER
iP.N.Lebedev Institute of Physicsj
F321() ߌ4  5
(March 21 (Fri), 2008, @16:00 - 17:00)

T v:
Both diffuse high energy gamma-rays and an electron-positron annihilation
line emission have been observed in the Galactic Center (GC) region.
Although X-ray observations indicate that the galactic black hole Sgr A is
inactive now, we suggest that the Sgr A was in active phase long time ago.
Consequently a  galactic nuclear is activated when a captured star is
tidally disrupted and matter is accreted into the black hole. We argue that
the galactic black hole could be a powerful source of relativistic protons
when it captures a star. In this paper we assume that relativistic protons
are injected into the ambient material from the galactic black hole.  We are
able to explain the current observed diffuse gamma-rays and the very
detailed annihilation line spectrum by p-p collisions of these protons. The
required injected amount of energy is consistent with the
estimation of the tidal capture of stars. Our model calculated GeV and
511keV gamma-ray intensities are consistent with the observed  results of
EGRET and INTEGRAL.
We estimated also  the flux of de-ecitation lines from the Galactic center
protducd by acclerated protons hich may be a good tool for for testing of
our model.

412
ځFHigh energy emission from Galactic sources observed with INTEGRAL
iINAF-IASF Milano,Italy@JSPS PostDoctoral Fellowshipj
F321() ߌ2  3
(March 21 (Fri), 2008, @14:00 - 15:00)

T v:
The physical processes at the origin of the high energy spectral evolution of LMXBs are
still a matter of debate. This is particularly true for the origin of the so-called
transient "hard X-ray tails" that dominate above 30 keV the spectra of persistenly bright
LMXBs hosting a neutron star. Up to now such hard tails have mainly been described in terms
of phenomenological models such as a simple power-law on top of a thermal Comptonisation
spectrum. Even if statistically satisfactory, no physical information can be driven by such
a description.
In the attempt to overcome simple phenomenological models, we propose a physical scenario
that can explain the transient nature of the hard tails as well as the different spectral
states of NS LMXBs. In this seminar, I will show our scenario as derived from the study of
a sample of twelve persistent NS LMXBs, using INTEGRAL data. Based on our encouraging
results, we have developed a new Comptonisation model (CompBT in XSPEC terminology) that I
will discuss together with its application to high energy spectra of NS LMXBs.
Parallel to this main-stream research, I will briefly show the results of our multi-
wavelength campaigns aimed to study the nature of new INTEGRAL sources (Chandra/RXTE/ESO-
NTT follow-up data). Both the sources we have studied up to now have been identified as
LMXBs and in particular the fastest accreting msec pulsar IGR J00291+5934, and the Black
Hole candidate IGR J17497-2821.The study of the latter source, IGR J17497-2821, with the
Suzakumission is the topic of my JSPS PostDoctoral fellowship in Japan.

411
ځF Galaxy Zoo
u tFDr. Anze Slosar@
(Berkeley Center for Cosmological Physics)
F37() ߌ4  5
(March 7 (Fri), 2008, @16:00 - 17:00)

T v:
Galaxy Zoo is a project that attempts to harness the power of Internet
public to classify morphologies of about one million galaxies from the
SDSS catalogue. It is composed of a website, forum and blog, creating a
unique online community. In a couple of months the project has achieved
over 35 million classifications from about 100 thousand users. The
detector is highly non-linear and the noise highly non-Gaussian which
makes the challenge of reducing this dataset unique. However, the shear
amount of data allows us to calibrate the morphological classifications
and extract useful science. I will discuss the project, the expected and
the strange effects that we are seeing in the data and some preliminary
science results.

410
ځFNulling Interferometry at the Keck and Palomar Observatories
u tFDr. Gene Serabyn@
iJet Propulsion Laboratory, California Institute of Technologyj
F24() ߑO11  12
(February 4 (Mon), 2007, @11:00 - 12:00)

T v:
Detection of faint emission from faint brown dwarfs, exo-planets and exozodiacal dust very
close to bright stars requires very high-contrast, high-resolution observational
techniques. One promising approach is nulling interferometry, which can be used to cancel
the stellar signal collected by multiple telescope apertures or subapertures, while
transmitting the light from off-axis emission sources. Over the past decade, nulling has
moved from the concept phase to implementation on several telescopes, including at the Keck
Observatory, where on-sky stellar rejections of order 100:1 are now regularly achieved.
Shared-risk observations have been underway for the past couple of years at Keck, while the
performance has been improving, and in Feb. 2008, NASA's exozodiacal dust key-science
project on the Keck Interferometer Nuller is slated to begin. The goal of this program is
to search for faint dust within about 1 Astronomical Unit of nearby stars, i.e., in their
habitable zones, in order to begin to determine if dust will pose a hindrance to future
direct observations of exoplanets. This talk will cover the basics of nulling
interferometry, and then move on to the results achieved in the laboratory at JPL, and
conclude with a description of the nulling interferometers implemented at the Keck and
Palomar Observatories.

409
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u tFߎiww@wnȁj(Itsuki Sakon)
F125() ߌ45
(January 25 (Fri), 2008, @16:00 - 17:00)

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F124() ߌ3
(January 24 (Thu), 2008, @15:30 - )

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(December 21 (Fri), 2007, @14:00 - )

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406
ځF21-cm Cosmology
u tFRennan Barkana @(Tel Aviv University)
F125() ߌ4
(December 5 (Wed), 2007, 16:00 - )

T v:
Cosmologists have studied on the one hand the cosmic microwave
background from the early universe, and on the other hand, galaxies
and quasars that formed much more recently. This leaves an unknown
frontier, from redshift 6 up to 1000, during which the first galaxies
formed and subsequently heated and ionized the cosmic gas. Several
international efforts are underway to measure fluctuations in the
redshifted 21-cm emission from neutral hydrogen at redshifts 6-15.
This new observational probe promises to reveal much about cosmic
reionization, and to allow the detection and study of some of the
earliest galaxies that formed in the universe.

405
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F124() ߌ3
(December 4 (Tue), 2007, @15:30 - )

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404
ځFMorphological Studies of Proto-Planetary Nebulae
u tFAc @@(fo[w)
F104() ߌ12
(October 4 (Thu), 2007, @13:00 - 14:00)

T v:
High spatial resolution imaging of proto-planetary nebulae (PPNs) has
been the workhorse to investigate the detailed structures of these
circumstellar shells of post-asymptotic giant branch (post-AGB) stars.
Because the history of mass loss during the late AGB phase is
imprinted in the density distribution of these PPN shells, understanding
the PPN structure (hopefully) direcly translates to understanding mass
loss processes themselves.  In this talk I will review PPN morphological
studies for the past 10 years or so and summarize what we have learnt.

403
ځFThe Case for a Significant Population of Sub-Luminous Star Forming
Galaxies at Redshift 10
u tFRichard Ellis  (Professor, Caltech)
F914() ߌ23
(September 14 (Fri), 2007, @14:00 - 15:00)

T v:
Locating and characterizing the sources responsible for
cosmic reionization and ending the so-called "Dark Ages"
is a new frontier in theoretical and observational astronomy.
A popular view is that, a few hundred million years after
the Big Bang, a high density of low mass star forming galaxies
were produced. Finding and studying such faint sources is
a major driver for future facilities such as the James
Webb Space Telescope and the proposed Thiry Meter Telescope.
Meanwhile, by harnessing the strong gravitational lensing
power of massive clusters, the first candidate sources beyond
z=7 are being found and studied. I will describe the progress
(and limitations) of the work we are doing with Keck, Spitzer
and Hubble in this area which provides a first tentative glimpse
of the Universe at redshift 10.

402
ځFIRSF/SIRIUS study of the heart of the Great Attractor, and the NIR
evolution of a unique helium nova
u tFPatrick Alan Woudt
(Department of Astronomy, University of Cape Town)
F820() ߌ23
(August 20 (Mon), 2007, @14:00 - 15:00)

T v:
We have used IRSF/SIRIUS to study the Norma cluster, the most massive
cluster in the Great Attractor, in detail. I will present a overview of
the dynamical status of the Norma cluster, a deep Ks-band luminosity
function, the ongoing determination of the near-infrared (NIR)
fundamental plane of the Norma cluster, and a prime example of strong
galaxy transformation at the core of the Norma cluster.
Aside from this extragalactic work, we have been involved in the NIR
monitoring of the evolution of a unique helium nova (V445 Puppis = Nova
Puppis 2000) with the IRSF/SIRIUS. I will present our recent results on
V445 Puppis, including high-angular resolution imaging of the nova shell
with adaptive optics on the VLT, integral field unit spectroscopy, and
discuss possible scenarios regarding the nature of the underlying binary.

401
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u tF p @iV nCϑj(Hideki Takami)
F83() ߌ23
(August 3 (Fri), 2007, @14:00 - 15:00)

T v:
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400
ځFCOϑƒn㕪ϑi߂鐯kw
u tFĔ ps @ikwj(Hideyuki Saio)
F718() ߌ4
(July 18 (Wed), 2007, 16:00 - )

T v:
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399
ځFExploring Sites of Galaxy Formation:
Large Lyman-alpha Nebulae in the Bootes Field
u tFMoire Prescott @(University of Arizona)
F713() ߌ45
(July 13 (Fri), 2007, @16:00 - 17:00)

T v:
Large Lyman-alpha nebulae (>100 kpc) are thought
to be sites of ongoing massive galaxy formation, as suggested
by their copious Lyman-alpha emission and their association
with luminous, young, star-forming galaxies.  Very few such
systems are known, hence many fundamental questions about
their space density, excitation mechanisms, and environments
remain unanswered.  Most examples of Lyman-alpha nebulae have
been discovered via deep narrowband imaging surveys of known
galaxy overdensities.  In contrast, a large Lyman-alpha nebula
was recently discovered in the NOAO Deep Wide-Field Survey
Bootes field via its strong mid-infrared emission.  A detailed,
multiwavelength study has revealed a complex system that
contains a obscured AGN and several nearby young galaxies.  In
addition, diffuse continuum emission and diffuse HeII emission
suggest that this particular Lyman-alpha nebula may also be
excited by spatially-extended star formation.  Motivated by
these results we have also begun a number of other programs to
study the properties and space density of large Lyman-alpha
nebulae.  The answers to these questions will inform our
understanding of what processes dominate the formation of
massive galaxies.

398
ځFTesting Lambda CDM model with Cosmological Simulations:
massive galaxies and cosmic star formation history
u tF Y @(University of Nevada, Las Vegas)
(Kentaro Nagamine)
F713() ߌ23
(July 13 (Fri), 2007, @14:00 - 15:00)

T v:
Today, theorists are challenged by the overwhelming wealth of
observational data on galaxies, which must be analyzed and
interpreted in a cosmological context. The goal of our work is to
bridge the gap between the observation and theory of galaxy formation
using  cosmological hydrodynamic simulations.
The concordance Lambda cold dark matter (CDM) model, which has
been very successful in explaining various observations, is currently
challenged by two major issues in galaxy formation: one is the
existence of massive galaxies at z~6, and the other is the existence
of dead & red'' extremely red objects (EROs) at z=1-3.  Using two
different types of cosmological simulations (smoothed particle
hydrodynamics [SPH] and total variation diminishing [TVD]), I will
discuss our current understanding of these population of galaxies and
issues with simulations.  Turning to a purely analytic model of
cosmic SF history, we recently developed the two-component Fossil'
model based on the observed colors and luminosity densities of SDSS
galaxies at z~0.  This model exhibits roughly constant SFR density at
z=3-6. These two models (i.e. the hydro simulations and the Fossil
model) both predict that 60-70% of stellar masses in the Universe
were already in place by z=2, in contrast with current observational
constraints. The Fossil model also predicts that the bulge component
mostly formed at z>1.5.

397
ځFThe Rate of Type Ia SNe in a Variety of Astrophysical Roles
u tFDr. Laura Greggio
@@@@Associate Astronomer
@@@@National Institute for Astrophysics (INAF)
F615() ߌ23
(June 15 (Fri), 2007, 14:00 - 15:00)

T v:
@Type Ia Supernovae are spectacular events which allow us to probe the
@Universe in its farthest depths. The rate at which these events occur
@is a crucial ingredient for modelling of the chemical evolution of
@stellar systems, galaxy clusters, and of the universe as a whole, as
@well as of the energy input from SNe to the interstellar medium.
@Still, the progenitors of SNIa have not yet been identified among the
@different options offered by stellar evolution theory.  In particular,
@the distribution of the delay times (i.e. the time elapsed since the
@birth of a SNIa progenitor and its explosion) is poorly known.  In
@this seminar I will review and discuss the options for this crucial
@quantity which can be found in the current literature, and illustrate
@the impact of different delay times distributions on some broader
@astrophysical issues: the interpretation of the cosmic evolution of
@the SNIa rate, the formation timescales of systems with an $\alpha$
@elements overabundance, the Fe budget of clusters of galaxies.

396
ځFFormation of Primordial Stars
u tFgcI  (Éww@w)(NAOKI YOSHIDA)
F58() ߌ23
(May 8 (Tue), 2007,  14:00 - 15:00)

T v:
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395
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u tF㏺Y  (YƑwj(AKIO INOUE)
F427() ߌ23
(April 27 (Fri), 2007, 14:00 - 15:00)

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