Regular time & place: Fridays in GBII, R524.
13:00-14:00 Lunch
Please prepare 1min summary of your research interest, and one casual question to the speaker.
Please order lunch following Kevin's instruction by 19:30 on Thurs.
14:00-15:00 talk
Please take a look at speaker's past publications.
Prepare at least one question.
- Colloquium has moved to General Building II, R524. Please find the direction here, Direction to GBII
- Direction to NTHU Physics. GBII is in front of physics building.
- NTHU campus map
- NCTS colloquium schedule
- ASIAA colloquium schedule (we can connect via polycon)
- NCU colloquium schedule
6/2 Valerie Wong, 12:20-
6/3 No colloq.
6/17
Prof. Dipak Debnath
Title : Two-Component Advective Flow Solution : A Generalized Model to Understand Accretion Flow Dynamics Around Black Holes
Abstract: It has been more than two decades of the classic work by Chakrabarti and his collaborators on the two component advective flow (TCAF) model. Recently, we successfully been able to include it in HEASARC's spectral analysis software package XSPEC as an additive local model to fit energy spectra from different black hole candidates (BHCs) and obtain physical accretion flow parameters, such as, two component (Keplerian disk and sub-Keplerian halo) accretion rates, shock (location, i.e., the size of the Compton cloud, and the compression ratio) parameters. Evolutions of spectral and timing properties are transparent from the TCAF model fitted/derived physical parameters. Reason of different spectral states and their transitions during an outburst of a transient BHC are also clear. One can also predict frequency of the dominating quasi-periodic oscillation (QPO) from TCAF model fitted shock parameters and even predict most preferable mass range of an unknown BHC from TCAF fits. To our knowledge this gives us the most physical tool to investigate the accretion flow dynamics around black hole candidates.
Past colloquium
5/27 樋口祐一(ASIAA)
The standard cosmological model called LCDM which assumes dark matter and dark energy has been tested with many observations. Those observations revealed that phenomena predicted from LCDM are almost consistent with observations. However, the origin of dark energy is still unknown and this energy cannot be explained by known physics. Therefore, the theory explaining the cosmic acceleration of the Universe is needed.
One solution for the problem is called as f(R) gravity which modifies the gravitational theory. Since the effects from f(R) gravity are imprinted in matter distribution in the Universe, weak lensing analysis with Subaru/Hyper Suprime-Cam (HSC) would be a powerful tool to constrain the theory. In order to investigate the possibilities to constrain it with HSC, we carried out weak lensing simulations and investigated the possibilities. Through the analysis of the weak lensing simulation, we found that weak lensing analysis with HSC could provide ten times stronger constraint on f(R) gravity model. (Reference: arXiv 1603.01325)
5/20 Jimmy (NTHU)
Pulsar detection of GRX in Low Earth Orbit
In this thesis, we try to estimate the pulsar detection of Gamma Ray
Explorer (GRX). GRX is a soft gamma-ray telescope, which is expected
on satellite mission in 2020, with 3 times successful balloon launch
in past decade. GRX has good spatial and energy resolution, which can
do well Compton event re- construction, to help us explore soft
gamma-ray astrophysics objects. For data analysis, GRX use Maximum
Likelihood Expectation Maximization (MLEM) algorithm to improve
imaging property. We conclude that GRX has 12.7 sigma detection at
(l,b)=(0,135) with a 5 minute exposure and > 10 sigma detection at
(l,b)=(0,180) with < 1 minute for Crab nebula in MeV range. We also
present Vela pulsar has 7.9 sigma detection at (l,b)=(0,180) in 1-day
observation, and 8.7 sigma detection for 0.005 Crab flux at
(l,b)=(0,180) in a 2-day observation. The results are much better than
prototype balloon flight of GRX in 2009 with 6 sigma detection in 6
hours exposure time.
5/6 Kevin, Henry
Kevin: A UV to Mid-IR Study of AGN Selection http://arxiv.org/abs/1402.5420
Henry:
Title:Space-Time Approach to Non-Relativistic Quantum Mechanics.
Abstract:
Non-relativistic quantum mechanics is formulated here in a different way. It is, however, mathematically equivalent to the familiar formulation. In quantum mechanics the probability of an event which can happen in several different ways is the absolute square of a sum of complex contributions, one from each alternative way. The probability that a particle will be found to have a path x(t) lying somewhere within a region of space time is the square of a sum of contributions, one from each path in the region. The contribution from a single path is postulated to be an exponential whose (imaginary) phase is the classical action (in units of ℏ) for the path in question. The total contribution from all paths reaching x, t from the past is the wave function ψ(x, t). This is shown to satisfy Schrodinger's equation. The relation to matrix and operator algebra is discussed. Applications are indicated, in particular to eliminate the coordinates of the field oscillators from the equations of quantum electrodynamics.
5/13 no colloquium (ASROC)
4/29 校慶日
5/4
Chao-Ling Hung
Title:
Connecting dusty starburst galaxies and proto galaxy clusters: a case study at z=2
Abstract:
The most prodigious starburst galaxies are absent in massive galaxy clusters today, but their connection with large scale environments is less clear at z>2. I present our search of dusty star-forming galaxies (DSFGs; SFR>100 Msun/yr) within and around a protocluster at z~2.1 in the COSMOS field. Both DSFGs and color-selected SFGs show significant overdensities around the protocluster, and this structure spans across several tens of cMpc, considerably larger than previously observed. The cluster core and the extended DSFG- and SFG-rich structure together demonstrate an active cluster formation phase, in which the cluster is accreting a significant amount of material from large scale structure while the more mature core may begin to virialize. The finding of this DSFG-rich structure, along with a number of other protoclusters with excess DSFGs and AGNs found to date, suggest that the overdensities of these rare galaxies indeed trace significant mass overdensities. However, it remains puzzling how these intense star formers are triggered concurrently. Although an increased probability of galaxy interactions and/or enhanced gas supply can trigger the excess of DSFGs, our stacking analysis based on 850 micron images and morphological analysis based on rest-frame optical imaging do not show such enhancements of merger fraction and gas content in this structure.
Andrew Mann
Talk title:
Zodiacal Exoplanets in Time: how planetary systems evolve from infancy to maturity
Abstract:
Planets and their host stars evolve with time, and the first few hundred million years are thought to be the most critical. During this time a variety of mechanisms (e.g., accretion, atmospheric escape, migration) alter the properties of young planets. By comparing planet characteristics from a range of ages we can constrain the timescales and importance of these processes. However, the vast majority of known planetary systems, including those discovered by the Kepler mission, are much older (billions of years) than the timescales of interest (millions to hundreds of millions of years) and more often have poorly or completely unconstrained ages. The repurposed Kepler (K2) spacecraft offers a unique opportunity to study planetary evolution as it observes star-forming regions and young stellar clusters aged 1-850 million years. I will present our effort to identify and characterize young transiting exoplanets from K2 light curves. Early results show a change in planet occurrence between 125 and 850 Myr, suggesting even small planets form at orbital periods greater than 25 days and migrate inward on timescales of 0.1-1 Gyr.
4/22 Yoshiki Toba(ASIAA)
Title:
Statistical properties of Dust Obscured Galaxies revealed by HSC-SSP data with infrared data
Abstract:
Dust Obscured Galaxies (DOGs) are a subset of high-redshift (z~2) optically-faint ultra-luminous infrared galaxies (ULIRGs). Recently, some works have reported that the brighter mid-infrared DOGs are more AGN-dominated, and indicated that black holes in the IR-bright DOGs are expected to show the highest accretion rate during a major merger event. In addition, some works reported that IR-bright DOGs tend to reside in richer environments than fainter ones, and the most luminous DOGs may evolve into brightest cluster galaxies. Therefore, particularly IR-bright DOGs are expected to be a crucial population in terms not only of the co-evolution of galaxies and supermassive black holes (SMBHs) but also of structure formation.
Combining the early data of the deep and wide optical data from Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP), VIKING DR2 near-IR, and WISE (ALLWISE) mid-IR data, we are searching the IR-bright DOGs.
In this presentation, we will report the statistical properties of DOGs such as luminosity function, luminosity density, and clustering properties (Toba et al. 2015, 2016 in prep.).
4/15 Rieko Momose (NTHU)
Title: Diffuse Lyman-alpha halos around star forming galaxies ~ as a tracer
of galaxy evolution
Abstract:
Theoretical studies have suggested that Lyman-alpha emission of high-z
star-forming galaxies extends than their UV continuum emission which
reflects star-forming regions in galaxies (e.g., Laursen &
Sommer-Larsen 2007, Zheng et al. 2011, Dijkstra & Kramer 2012,
Verhamme et al. 2012). This extended Lyman-alpha emission feature
around galaxies is so called Lyman-alpha halos (LAHs). Because LAHs
are too diffuse to detect from a single galaxy, the stacking analysis
is often used to find the evidence of LAHs from observational data
(e.g., Steidel et al. 2011, Matsuda et al. 2012). However, there is a
argument that artifacts by the analysis are possible to produce
artificial LAHs. Thus, the existence of LAHs is still under debate. In
order to investigate the presence of LAHs, we use large star-forming
galaxy samples at z = 2-7 found by Subaru telescope, and also
carefully examine potential artifacts mimicking LAHs. In this talk, we
show our analysis and results of LAHs over wide redshift range.
Additionally, we also discuss the dependences between physical
properties of LAEs and the sizes of LAHs based on my recent paper
(Momose et al. 2016).
4/8
Speaker: Paul
Title: Studying the SGR 1806-20/Cl* 1806-20 region using the Fermi
Large Area Telescope
Abstract: The region around SGR 1806-20 and its host stellar cluster
Cl* 1806-20 is a potentially important site of particle acceleration.
The soft gamma-ray repeater and Cl* 1806-20, which also contains
several very massive stars including a luminous blue variable
hypergiant LBV 1806-20, are capable of depositing a large amount of
energy to the surroundings. Using the data taken with the Fermi Large
Area Telescope (LAT), we identi ed an extended LAT source to the
south-west of Cl* 1806-20. The centroid of the 1-50 GeV emission is
consistent with that of HESS J1808-204 (by now unidentified). The LAT
spectrum is best-fi t by a broken power-law with the break energy E_b
= 297 +/- 15 MeV. The index above Eb is 2.60 +/- 0.04, and is
consistent with the flux and spectral index above 100 GeV for HESS
J1808-204, suggesting an association between the two sources.
Meanwhile, the interacting supernova remnant SNR G9.7-0.0 is also a
potential contributor to the LAT flux. A tentative flux enhancement at
the MeV band during a 45-day period in the year 2011 is also reported.
We discuss the origin(s) of the extended LAT source using both
leptonic and hadronic scenarios.
4/1 校際活動週(停課一日)
3/25 Kiyoto Yabe
Title: The chemical evolution of galaxies at high redshift revealed by
Subaru/FMOS
Abstract: Revealing the history of the chemical enrichment of galaxies
is important to understand the past star-formation history of galaxies
in an independent way. In recent years, many efforts have been made
aiming to measure the metallicity of galaxies at high redshift. The
sample size, however, is still limited for statistical studies at z>1.
Here, we present some results from our recent near-infrared
spectroscopic surveys conducted with Subaru/FMOS, consisting of >4,000
galaxies with significant Ha detection at z~1.4, where galaxies in the
most active phase of the cosmic history. In this study, we measure the
gas metallicity by using the [NII]6583/Ha emission line ratio of the
composite spectra in various stellar mass and star-formation rate
bins. The resulting mass-metallicity relations of our sample are
generally in agreement with previous studies in a similar redshift
range. Although no clear dependence of the mass-metallicity relation
with star-formation rate is found in our sample at z~1.4, our results
at z~1.4 are close to the fundamental metallicity relation at z~0.1
that is extrapolated to the high-SFR regime. We detect significant
[SII]6716,6731 emission lines from the composite spectra. The electron
density estimated from the [SII]6716,6731 line ratio ranges from 10 -
500 cm^-3, which generally agrees with that of local galaxies. On the
other hand, the distribution of our sample on [NII]6583/Ha vs.
[SII]6716,6731/Ha is different from that found locally. We estimate
the nitrogen-to-oxygen abundance ratio (N/O) from the N2S2 index, and
find that the N/O in galaxies at z~1.4 is significantly higher than
the local values at a fixed metallicity and stellar mass. The
metallicity at z~1.4 recalculated with this N/O enhancement taken into
account decreases by 0.1 - 0.2 dex, which is lower than the local
fundamental metallicity relation. These surveys are excellent test
cases for the future surveys with a next-generation very wide-field
instrument on the Subaru Telescope, Prime Focus spectrograph (PFS).
3/11 Li-Ting Hsu (ASIAA)
Photometric redshifts for X-ray selected AGNs: paving the way towards
the study of AGN/galaxy coevolution
To better investigate the AGN and galaxies coevolution, we need to
have a complete characterisation and census of AGNs with accurate
redshifts. Spectroscopic redshifts are relatively reliable, however,
it is time-consuming and difficult to be obtained for faint sources at
high redshifts. Therefore we have to rely on photometric redshifts
(photo-z) which need to be tuned specifically for AGNs. In our work,
we studied on the X-ray selected AGNs in the Chandra deep filed-south
(CDFS) region, mainly using de-blending Subaru intermediate bands and
HST optical/near-infrared data to compute photo-z. We first matched
the multi-wavelength counterparts for the X-ray sources, then applied
proper magnitude priors and appropriate AGN-galaxy hybrid templates
for SED fitting. We achieved a photo-z accuracy of 0.013 with an
outliers fraction of 5.3% for X-ray sources. With the SED fitting
results of our well-trained AGN-galaxy hybrids, we further studied the
AGN host properties via the rest-frame color-magnitude diagram (CMD)
which is an useful probe to trace the stellar populations. We made
corrections for dust extinction and AGN contamination for the AGN host
colors, and found that the AGN host colors also present a bimodality
in the CMD up to z~2.5 as found in normal galaxies. In this talk, I
will present the CMD result of AGN host colors, and compare with the
result of normal galaxies.
3/8 (Tue) 12:20pm- Michal Michalowski (Edinburgh)
Massive stars formed in atomic hydrogen reservoirs"
Abstract:
I will discuss the process of gas inflow on galaxies and subsequent
fueling of star-formation. Using recent ATCA HI observations I will
show that galaxies showing anomalous local metallicity decrements
(gamma-ray burst host galaxies) have substantial atomic gas
reservoirs, and are deficient in molecular gas. This suggest that star
formation in these galaxies may be fuelled by recent inflow of
metal-poor atomic gas. This is controversial, but can happen in
low-metallicity gas near the onset of star formation because cooling
of gas (necessary for star formation) is faster than the HI-to-H2
conversion.
2/19 (Fri)
Ming-Hsu Yang(NTHU)
"Measurements of the Scattering Matrix for
the Interaction Between Solar Acoustic Waves and Sunspots".
Abstract:
* Using helioseimic waves to probe subsurface structure of sunspots is
one of the goals in helioseismology.
* The wave-sunspot interaction can be regarded as a scattering problem.
* This work measures the process of an organized incident wave-packet
traveling through a sunspot. From the measured scattered waves, the
scattering matrix is computed.
* The scattered wave and scattering matrix contain information about
3D structure of sunspot, to be investigated in future study.
1/8 Yu-Yen Chang (CEA)
Title: Infrared AGNs in Galaxy Evolution
Abstract: I will present a study of the connection between activity of nuclear accretion, star formation, and galaxy morphology. In our work, we focus on infrared selected AGNs, which are complementary samples of X-ray selected objects. We fit optical to far-infrared photometry by the latest SED techniques to derive stellar masses, star formation rates, dust properties, and AGN contribution in the COSMOS field. We explore galaxy morphologies through HST/ACS images, which provide structural properties of galaxy stellar component at high redshift. We discover the differences between obscured AGN host galaxies and star-forming galaxies. We discuss the influence of compaction scenario and the role of AGNs in galaxy evolution.
1/11 Paul Price (Princeton)
下午五點半 地點: 綜二館 Room 501
Title: The Hyper Suprime-Cam Pipeline
The Hyper Suprime-Cam Strategic Survey Program aims to image 1400 square degrees with HSC on Subaru to study galaxy formation and cosmology using weak lensing. We currently have collected over 5000 science-grade exposures towards this goal, with more to come over the next few years. To reduce this data, we have constructed a pipeline based on that being developed for the Large Synoptic Survey Telescope. I will introduce the HSC pipeline, outline its features and the quality of the reduced data, and demonstrate how the pipeline can be used to reduce open-use HSC data or form the basis for other astronomical image operations.
1/15 No class suggested by school.
*Abby away for 11/27, 12/4, 12/14.
12/25, GBII R521
Regina Barber DeGraaff (WWU)
1-2pm
Scientists are People Too! How to be an effective science communicator
Abstract:
Many scientists are passionate about communicating science clearly to the public to accomplish the following goals.
• To make Science, Engineering, Technology and Math (STEM) accessible to ALL.
• To increase science literacy
• To take away the misconception that scientists have no emotions, are all “geniuses”, work alone, and can not to relate or talk to “real" people.
But how do we do this? Come listen to Astrophysicist & Spark Science Host Dr. Barber DeGraaff share experiences in public outreach and
learn some tips to becoming a better science communicator.
2-3pm
"Globular Cluster Survey of the Shapley Supercluster”
Globular cluster populations were instrumental in helping humans find their place in the universe. Now they are studied to find possible clues to galaxy formation. Recent evidence shows that number of globular clusters (GC), Ntot, scales with dark matter halo mass of the host galaxy, Mhalo. The correlation between Ntot and Mhalo gives us a window into GC formation efficiency. We are probing the high mass end of this relation by investigating the globular cluster systems of 11 giant elliptical galaxies in clusters associated with the Shapley Supercluster, the largest mass concentration in the local universe and possibly a major source of the Local Group's 630 kms motion with respect to the cosmic microwave background. The sample galaxies were imaged with the Advanced Camera for Surveys Wide Field Channel in the F814W bandpass and are in the redshift range z=0.035-0.048.
We find a nonlinear relationship between the host galaxy luminosity LV and number of globular clusters Ntot , with Ntot scaling as LV to the power of 1.6; thus, the GC specific frequency SN increases with LV for these high-mass galaxies. Our data show good consistency with the U-shape relationship between SN and host galaxy magnitude MV found in other recent GC studies. Galaxies at intermediate luminosities near the low-point of the U have both the lowest SN values and highest stellar mass ratios, indicating that Ntot scales more closely with the dark halo mass than with stellar mass. For one galaxy in our sample, ES0325-G004, additional multi-band imaging was obtained, and we find a bimodal globular cluster color distribution with characteristics typical of most giant ellipticals.
12/18, 1pm, R521
Sperello di Serego Alighieri (Arcetori),
The rich Interstellar Medium of Early Type Galaxies
Sperello di Serego Alighieri, INAF - Arcetri Astrophysical Observatory, Firenze, Italy
Abstract: Early type galaxies (ETG) were once thought to be devoid of interstellar medium (ISM), just red and dead.
More recently it has been established that they have a rich ISM, from the hot gas emitting in X-rays to the very cold molecular gas and dust.
I will review the ISM of ETG, show how the various gas phases can survive together, and discuss what we can learn about the evolution of ETG from their ISM.
12/17, 2pm, R524
Wing-Kit Lee (ASIAA)
Spiral Structure in Disks
I will review some mechanisms for generating spiral structures in astrophysical disk systems such as galaxies and protoplanetary disks. In particular, I will talk about my research on instabilities of the galactic spiral arms, namely feathering instability. Feathering instability may be responsible for the regular density structures commonly found near the spiral arms. In the second part of my talk, I will introduce some of my attempts to understand the three-dimensional spiral shocks in a protoplanetary disk.
12/11 NTCS annual theory meeting. No colloquim
12/14(Mon,12:20-13:10) GBII R521
Regina Barber DeGraaff (WWU)
"Globular Cluster Survey of the Shapley Supercluster”
Globular cluster populations were instrumental in helping humans find their place in the universe. Now they are studied to find possible clues to galaxy formation. Recent evidence shows that number of globular clusters (GC), Ntot, scales with dark matter halo mass of the host galaxy, Mhalo. The correlation between Ntot and Mhalo gives us a window into GC formation efficiency. We are probing the high mass end of this relation by investigating the globular cluster systems of 11 giant elliptical galaxies in clusters associated with the Shapley Supercluster, the largest mass concentration in the local universe and possibly a major source of the Local Group's 630 kms motion with respect to the cosmic microwave background. The sample galaxies were imaged with the Advanced Camera for Surveys Wide Field Channel in the F814W bandpass and are in the redshift range z=0.035-0.048.
We find a nonlinear relationship between the host galaxy luminosity LV and number of globular clusters Ntot , with Ntot scaling as LV to the power of 1.6; thus, the GC specific frequency SN increases with LV for these high-mass galaxies. Our data show good consistency with the U-shape relationship between SN and host galaxy magnitude MV found in other recent GC studies. Galaxies at intermediate luminosities near the low-point of the U have both the lowest SN values and highest stellar mass ratios, indicating that Ntot scales more closely with the dark halo mass than with stellar mass. For one galaxy in our sample, ES0325-G004, additional multi-band imaging was obtained, and we find a bimodal globular cluster color distribution with characteristics typical of most giant ellipticals.
12/4 Howard Yee (Tronto)
Title: The Evolution of Galaxies in Clusters at z~1 and Beyond
Galaxy clusters provide a large range of environments for the study of
how environment affects galaxy evolution. I will present some recent
results on the evolution of galaxies in clusters at z~1 and beyond from two
large cluster surveys. SpARCS is an imaging survey to look for galaxy clusters
up to z~2 using the cluster red-sequence technique based on a combination
of Spitzer Space Telescope’s IRAC 3.6um and ground-based z’-band images; GLASS
is a multi-object spectroscopic survey of 10 of the richest SpARCS clusters
at z~1 using the Gemini 8.2m telescopes. Analysis of GCLASS data show that
galaxies in-falling into clusters at z~1 have their star formation quenched
in a relatively short time scale of less than 500 Myr at an average location
close to 0.5 r_200 (the cluster-centric radius within which the cluster is
largely virialized). Using far-IR/submm data from the Herschel Space
telescope, we will look at the change in star-formation in detail
via dust emission in 3 clusters at z~1.2 as galaxies infall
into clusters. Time permitting, I will also show some results on star
formation in BGCs (brightest cluster galaxies) at high redshift
and the growth of stellar mass in these galaxies.
11/27 Meg Schwamb (ASIAA)
Probing the Inner Oort Cloud
Meg Schwamb (ASIAA)
The discovery of Sedna, nearly a decade ago, on a highly eccentric orbit beyond the Kuiper belt challenged our understanding of the Solar System. With a perihelion of 76 AU, Sedna is well beyond the reach of the gas-giants and could not be scattered onto its highly eccentric orbit from interactions with Neptune alone. Sedna’s aphelion at ~1000 AU is too far from the edge of the Solar System to feel the perturbing effects of passing stars or galactic tides in the present-day solar neighborhood. Some other mechanism no longer active in the Solar System today is required to emplace Sedna on its orbit. Sedna's origin remains an outstanding question in planetary astronomy.
Sedna's presence predicts a population of icy bodies on similar orbits residing past the Kuiper belt detached from the Solar System in what has been called the Inner Oort Cloud. The recent discovery of 2012 VP113 confirms the presence of the Inner Oort Cloud. The orbits of these distant planetoids are dynamically frozen in place providing a fossilized record of their formation. Finding just a handful of these bodies, we can begin to read this dynamical record. I will present the results of a wide-field survey aimed to to find the largest and brightest members of this population. In particular, I will focus on the constraints that can be placed on the proposed formation scenario where stellar encounters, early on in an embedded cluster phase of the Solar System, created Sedna-like orbits. I will also present new dynamical modeling to probe the location of the inner edge of the Inner Oort cloud and its implications for future observational campaigns searching for new members of this population.
11/20 Tom, Henry
Tom:
High velocity stars from close interaction of a globular cluster and a super
massive black hole
Observations show the presence, in the halo of our Galaxy, of stars moving
at velocities so high to require an acceleration mechanism involving the
presence of a massive central black hole. Thus, in the frame of a galaxy
hosting a supermassive black hole (108 M⊙) we investigated a mechanism for
the production of high velocity stars, which was suggested by the results of
N-body simulations of the close interaction between a massive, orbitally
decayed, globular cluster and the super massive black hole.
The high velocity acquired by some stars of the cluster comes from the
transfer of gravitational binding energy into kinetic energy of the escaping
star originally orbiting around the
cluster. After the close interaction with the massive black hole, stars could
reach a velocity sufficient to travel in the halo and even overcome the
galactic gravitational well, while some of them are just stripped from the
globular cluster and start orbiting on precessing loops around the galactic
centre.
Henry
Quantum Hilbert Hotel
In 1924 David Hilbert conceived a paradoxical tale involving a hotel with an infinite number of rooms to illustrate some aspects of the mathematical notion of “infinity.” In continuous-variable quantum mechanics we routinely make use of infinite state spaces: here we show that such a theoretical apparatus can accommodate an analog of Hilbert’s hotel paradox. We devise a protocol that, mimicking what happens to the guests of the hotel, maps the amplitudes of an infinite eigenbasis to twice their original quantum number in a coherent and deterministic manner, producing infinitely many unoccupied levels in the process. We demonstrate the feasibility of the protocol by experimentally realizing it on the orbital angular momentum of a paraxial field. This new non-Gaussian operation may be exploited, for example, for enhancing the sensitivity of NOON states, for increasing the capacity of a channel, or for multiplexing multiple channels into a single one.
11/13 Joker, Jimmy
Jimmy:
Leptonic origin of the 100 MeV gamma-ray emission from the Galactic centre
Context. The Galactic centre is a bright γ-ray source with the GeV-TeV band spectrum composed of two distinct components in the 1-10 GeV and 1-10 TeV energy ranges. The nature of these two components is not clearly understood. Aims. We investigate the γ-ray properties of the Galactic centre to clarify the origin of the observed emission. Methods. We report imaging, spectral, and timing analysis of data from 74 months of observations of the Galactic centre by Fermi/LAT γ-ray telescope complemented by sub-MeV data from approximately ten years of INTEGRAL/ PICsIT observations. Results. We find that the Galactic centre is spatially consistent with the point source in the GeV band. The tightest 3σ upper limit on its radius is 0.13◦ in the 10 − 300 GeV energy band. The spectrum of the source in the 100 MeV energy range does not have a characteristic turnover that would point to the pion decay origin of the signal. Instead, the source spectrum is consistent with a model of inverse Compton scattering by high-energy electrons. In this a model, the GeV bump in the spectrum originates from an episode of injection of high-energy particles, which happened ∼ 300 years ago. This injection episode coincides with the known activity episode of the Galactic centre region, previously identified using X-ray observations. The hadronic model of source activity could be still compatible with the data if bremsstrahlung emission from high-energy electrons was present in addition to pion decay emission.
Joker:
Title :Ethyl alcohol and sugar in comet C/2014 Q2 (Lovejoy)
Abstract:The presence of numerous complex organic molecules (COMs; defined as those containing six or more atoms)around protostars shows that star formation is accompanied by an increase of molecular complexity. These
COMs may be part of the material from which planetesimals and, ultimately, planets formed. Comets representsome of the oldest and most primitive material in the solar system, including ices, and are thus our best windowinto the volatile composition of the solar protoplanetary disk. Molecules identified to be present in cometaryices include water, simple hydrocarbons, oxygen, sulfur, and nitrogen-bearing species, as well as a few COMs,such as ethylene glycol and glycine. We report the detection of 21 molecules in comet C/2014 Q2 (Lovejoy),including the first identification of ethyl alcohol (ethanol, C 2 H 5 OH) and the simplest monosaccharide sugar gly-colaldehyde (CH 2 OHCHO) in a comet. The abundances of ethanol and glycolaldehyde, respectively 5 and 0.8%relative to methanol (0.12 and 0.02% relative to water), are somewhat higher than the values measured in solar-type protostars. Overall, the high abundance of COMs in cometary ices supports the formation through grain-surface reactions in the solar system protoplanetary disk.
11/6 Sara Ellison (Victoria), 521 in General 2nd building
Galaxy mergers in the nearby universe
Galaxy mergers and interactions are a fundamental process in the life cycle of galaxies. In this talk, I will present results from a multi-wavelength analysis of galaxymergers in the SDSS, that provides a panoramic investigation of the role of mergers on star formation, gas consumption and ISM chemistry. By combining samples of wide and close galaxy pairs, and fully coalesced "post-mergers", we have assembled a complete picture of the evolution of a galaxy during its entire interaction cycle. I will show how the observational results can be interpreted with simulations of binary mergers, which show that gas flows within the mergers are responsible for many of the observed trends. I will also present new results on the connection between galaxy mergers and AGN triggering, and demonstrate that whilst mergers certainly can trigger an AGN, this appears to be depend strongly on how the AGN are selected. Finally, I will present several new detections of kpc binary black holes that have been found in our sample.
10/30 Kevin, Paul
Paul: Observing two dark accelerators around the Galactic Center with Fermi Large Area Telescope
Abstract:
We report the results from a detailed γ−ray investigation in the field of two “dark accelerators”, HESS J1745-303 and HESS J1741-302, with 6.9 years data obtained byFermi Large Area Telescope. For HESS J1745-303, we found that its MeV-GeV emission is mainly originated from the “Region A” of the TeV feature. It γ−ray spec- trum can be modeled with a single power-law with a photon index of Γ ∼ 2.5 from few hundreds MeV to TeV. Moreover, an elongated feature, which extends from “Re- gion A” toward northwest for ∼ 1.3◦, is discovered for the first time. The orientation of this feature is similar to that of a large scale atomic/molecular gas distribution. For HESS J1741-302, our analysis does not yield any MeV-GeV counterpart for this unidentified TeV source. On the other hand, we have detected a new point source, Fermi J1740.1-3013, serendipitously. Its spectrum is apparently curved which resem- bles that of a γ−ray pulsar. This makes it possibly associated with PSR B1737-20 or PSR J1739-3023.
Kevin:
Title: Infrared luminosity functions of AKARI Sloan Digital Sky Survey galaxies
abstract: By cross-correlating the AKARI all-sky survey in six
infrared (IR) bands (9, 18, 65, 90, 140 and 160 μm) with the Sloan
Digital Sky Survey (SDSS) galaxies, we identified 2357 IR galaxies
with a spectroscopic redshift. This is not just one of the largest
samples of local IR galaxies, but AKARI provides crucial far-IR (FIR)
bands for accurately measuring the galaxy spectral energy distribution
(SED) across the peak of the dust emission at > 100 μ m. By fitting
modern IR SED models to the AKARI photometry, we measured the total
infrared luminosity (LIR) of individual galaxies. Using this LIR, we
constructed the luminosity functions (LF) of IR galaxies at a median
redshift of z= 0.031. The LF agrees well with that at z= 0.0082 (the
Revised Bright Galaxy Sample), showing smooth and continuous evolution
towards higher redshift LFs measured in the AKARI North Ecliptic Pole
(NEP) deep field. By integrating the IR LF weighted by LIR, we
measured the local cosmic IR luminosity density of ΩIR= (3.8+5.8-1.2)
× 108 L⊙ Mpc-3. We separate galaxies into active galactic nuclei
(AGN), star-forming galaxies (SFG) and composite by using the [N
II]/Hα versus [O III]/Hβ line ratios. The fraction of AGN shows a
continuous increase with increasing LIR from 25 to 90 per cent at 9 <
log LIR< 12.5. The SFRHα and ? show good correlations with LIR for SFG
and AGN, respectively. The self-absorption-corrected Hα/Hβ ratio shows
a weak increase with LIR with a substantial scatter. When we separate
IR LFs into contributions from AGN and SFG, the AGN contribution
becomes dominant at LIR > 1011 L⊙, coinciding with the break of both
the SFG and AGN IR LFs. At LIR≤ 1011 L⊙, SFG dominates IR LFs. Only
1.1 ± 0.1 per cent of ΩIR is produced by luminous infrared galaxies
(LIR> 1011 L⊙), and only 0.03 ± 0.01 per cent by ultraluminous
infrared galaxies (LIR > 1012 L⊙) in the local Universe. Compared with
high-redshift results from the AKARI NEP deep survey, we observed a
strong evolution of ΩSFGIR∝ (1 +z)4.1±0.4 and ΩAGNIR∝ (1 +z)4.1±0.5.
Our results show that all of our measured quantities (IR LFs, L*,
ΩAGNIR, ΩSFGIR) show smooth and steady increase from lower redshift
(the Revised Bright Galaxy Sample) to higher redshift (the AKARI NEP
deep survey).
10/23 Abby, Tomo
Abby
Tilte: GAMMA-RAY POLARIZATION OF THE SYNCHROTRON SELF-COMPTON PROCESS FROM A HIGHLY RELATIVISTIC JET
Abstract:
The high polarization observed in the prompt phase of some gamma-ray bursts invites extensive study of the emission mechanism. In this paper, we investigate the polarization properties of the synchrotron self-Compton (SSC) process from a highly relativistic jet. A magnetic-dominated, baryon-loaded jet ejected from the central engine travels with a large Lorentz factor. Shells with slightly different velocities collide with each other and produce shocks. The shocks accelerate electrons to a power-law distribution and, at the same time, magnify the magnetic field. Electrons move in the magnetic field and produce synchrotron photons. Synchrotron photons suffer from the Compton scattering (CS) process and then are detected by an observer located slightly off-axis. We analytically derive the formulae of photon polarization in the SSC process in two magnetic configurations: a magnetic field in the shock plane and perpendicular to the shock plane. We show that photons induced by the SSC process can be highly polarized, with the maximum polarization Π ~ 24% in the energy band [0.5, 5] MeV. The polarization depends on the viewing angles, peaking in the plane perpendicular to the magnetic field. In the energy band [0.05, 0.5] MeV, in which most γ -ray polarimeters are active, the polarization is about twice that in the Thomson limit, reaching Π ~ 20%. This implies that the Klein–Nishina effect, which is often neglected in the literature, should be carefully considered.
link: http://iopscience.iop.org/0004-637X/795/1/36
Tomo
"How to make a good presentation I"
10/16 Nanase Harada (ASIAA)
Title: Molecules in nearby galaxies
Abstract: Molecular compositions are useful probes of stages of star formation or external environment surrounding the molecular clouds. Observations and chemical modeling have refined molecules as tracers in galactic star-forming regions. On the other hand, extreme conditions in starburst galaxies or AGN-containing galaxies can create molecular compositions that are unusual in the Galaxy. Due to the high sensitivity of ALMA, it became possible to resolve many molecular lines in GMC-scale in some of nearby extragalactic sources. Unexpected observational results have already started to be seen, and theoretical models are needed to explain these results. Among many mechanisms that may affect chemistry in these complicated regions, I will present how chemistry changes under the warm dust conditions which could represent local starburst or (ultra-) luminous infrared galaxies.
10/9 國慶日 No colloquium
10/2 Matt Lehner (ASIAA), TAOS
TAOS II: The Transneptunian Automated Occultation Survey
Abstract:
The Transneptunian Automated Occultation Survey (TAOS II) will aim to detect occultations of stars by small (~1 to 30 km diameter) objects in
the Solar System and beyond. Such events are very rare (< 0.001 events per star per year) and short in duration (< 200ms), so many stars must be monitored at a high readout cadence. TAOS II will operate three 1.3 meter telescopes at the Observatorio Astronomico Nacional at San Pedro Martir in Baja California, Mexico. With a 2.3 qquare degree field of view and a high speed camera comprising CMOS imagers, the survey will monitor 10,000 stars simultaneously with all three telescopes at a readout cadence of 20 Hz. Construction of the site began in the fall of 2013 and should be completed in the summer of 2016. In this talk I will present the scientific goals of the survey and describe the observing system in detail.
http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=1361167
9/25 Hwang Chorng-Yuan (NCU)
Host Galaxies of Active Galactic Nuclei
I will discuss on the morphology of host galaxies of active galactic nuclei (AGNs). AGNs are one of the most powerful sources in the universe, although the radiation of an AGN is only originated from a very small nucleus region in the host galaxies of the AGN. The unification model of AGNs proposes that different types of AGNs, such as Seyfert I and Seyfert II, might be similar objects but viewing with different inclination angles. Our study found that the host galaxies of AGNs and normal galaxies have very different morphology at the central regions of the galaxies, suggesting that the AGN host galaxies have different evolution paths from the normal galaxies. It was generally believed that the host galaxies of AGNs tends to be early type galaxies, which I will argue to be incorrect. Besides, I will show that several different types of AGNs, which were supposed to be intrinsic similar objects and could be explained by a unification model, such as Seyfert I and Seyfert II, have completely different galaxy morphology distributions, indicating that the AGN unification model is not correct.
9/18 Weiling Tseng (NTNU)
Title: The sources of neutrals and plasma in Saturn’s magnetosphere
Abstract:
The Saturnian system is immersed in an extended cloud of neutrals, such as oxygen
molecules, hydrogen molecules, water molecules and their photodissociative products
like OH, O and H. Although water vapor ejected from Enceladus’ south pole is the
dominant neutral source, photolysis and radiolysis of ices can release H2O, O2, and H2
from the icy ring particles and the icy satellites. In addition, Titan’s exosphere is another
major source contributing neutral gas like H2 and H, and probably also CH4 and N2. Once
ionized, these neutrals are the source of the observed magnetospheric plasma in the
Saturnian system. In this talk, I will describe our work about the structures and
compositions of the neutral gas clouds of different origins and the plasma environments
and their important implications to complement the Cassini sciences.
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