::: 網站導覽 English 友善列印

# 學術演講及專題研討 (2014)

No. 時間地點 講者 題目/摘要
: 下載 PDF
12014-12-23 Tue
14:20~15:20
R1203
Chi-Ting Chiang
[MPA]

Position-dependent power spectrum and the application to the BOSS DR10 CMASS sample

The influence of large-scale density fluctuations on structure formation on small scales is described by the three-point correlation function (bispectrum) in the so-called “squeezed configurations.” This bispectrum is generated by non-linear gravitational evolution and possibly also by inflationary physics. We show that the sqeezed-limit bispectrum can be measured without employing three-point function estimators. Specifically, we use the “position-dependent power spectrum,” i.e., the power spectrum measured in smaller subvolumes of the survey (or simulation box), and correlate it with the mean overdensity of the corresponding subvolume. This correlation directly measures an integral of the bispectrum dominated by the squeezed configurations. Measuring this correlation is only slightly more complex than measuring the power spectrum itself, and sidesteps the considerable complexity of the full bispectrum estimation. We apply this technique to the BOSS DR10 CMASS sample. Combining the two- and three-point correlation functions, we break the degeneracies between the linear bias, growth rate, and sigma8, and put constraints on these parameters.

22014-12-17 Wed
14:20~15:20
R1203
Sebastien Muller
[Onsala Observatory]

PKS1830-211: the molecular absorption at z=0.89 and the background blazar

The line of sight to the lensed blazar PKS1830-211 intercepts the disk of a foreground spiral galaxy at z=0.89, yielding absorption detected in 40+ molecular species. These molecules can be used as cosmological probes at a look-back time of more than half the present age of the Universe. We can determine their excitation and measure the temperature of the cosmic microwave background, compare their kinematics and set constraints on the variations of the fundamental constants, measure the isotopic ratios from different isotopologues and investigate the elemental enrichment from stellar processes, and, of course, investigate the chemistry in the disk of the absorber. Regarding the background blazar, we will discuss ALMA observations obtained serendipitously at the time of a gamma-ray flare, allowing us to investigate the submm to gamma-ray connection. Last we will present the first ALMA polarimetry results, with the highest Faraday rotation ever measured, revealing a strong magnetic field at the base of the jet in PKS1830-211. In short, one line of sight, but many and diverse science results !

32014-12-16 Tue
14:20~15:20
R1203
Kartik Sheth
[NRAO]

Constraining the Assembly of Galaxy Disks over the last 12 Billion Years with ALMA, HST and Spitzer

Bars are a key signpost in the evolutionary history of a disk galaxy. When a disk is sufficiently massive, dynamically cold and rotationally supported, and sufficient time has elapsed for the baryonic matter to exchange energy and angular momentum with the dark matter halo or the outer disk, the formation of a bar is inevitable. Therefore understanding the evolution of the bar fraction as a function of the host galaxy properties and as a function of redshift provides important clues to the evolutionary history of galaxies. I will present the latest results on local bars from the Spitzer Survey of Stellar Structure in Galaxies (S4G) and discuss the observations for the declining bar fraction with redshift from the COSMOS survey. A plausible reason for the decline in the bar fraction may be that galaxy disks were too dynamically hot to host bars at higher redshift which we have investigated using the DEEP2 / AEGIS data. Together these data are beginning to provide a coherent and consistent picture for the assembly history of disks on the Hubble sequence. The star formation in these disks is also now being understood with the latest results from ALMA. I will show the latest results on the cosmological evolution of the molecular gas content in a mass-selected sample of galaxies at three epochs, z=2.2, z=1, and z=0.3 and discuss planned Cycle 1 observations of the molecular gas environment in the prototypical barred spiral NGC 1097.

42014-12-10 Wed
14:20~15:20
R1203
David Jewitt
[UCLA]

Sunlight Torques and Amorphous Ice

This talk will consist of two parts. First, I will discuss the latest findings concerning the Active Asteroids, nearby objects which continue to amaze with their unexpectedly varied properties. I will present evidence that some Active Asteroids are being rotationally disrupted by torques imposed by sunlight. Second, I will discuss the central importance of, evidence for, and puzzles concerning, amorphous ice in the Solar system.

52014-12-09 Tue
14:20~15:20
physics 104
David Jewitt
[UCLA]

Comet Science

Most comets are ice-containing bodies that have been stored in one of two distant reservoirs (the Kuiper belt and the Oort cloud) since the formation of the Solar system. I will provide an accessible, sweeping and scientifically up-to-date overview of the current understanding of comets, of their storage reservoirs, and of their importance for understanding the formation and evolution of the Solar system.

62014-12-03 Wed
14:20~15:20
R1203
Kate Su
[University of Arizona]

What Debris Disks Tell Us About Terrestrial Planet Formation

The critical stages of terrestrial planet formation have until now only been amenable to study in the realm of computer simulations. The newly discovered variable emission from extreme debris disks provides a unique opportunity to learn about asteroid-sized bodies in young exoplanetary systems and to explore planetesimal collisions and their aftermaths during the era of terrestrial-planet-building, putting the study of terrestrial planet formation on a better observational footing. I will highlight recent results from time-series monitoring of a 35 Myr-old disk around ID8 in NGC 2547, and discuss future directions for the study of the detailed process of large impacts in the era of terrestrial planet formation using space facilities.

72014-12-02 Tue
14:20~15:20
physics 104
Doug Lin
[UC Santa Cruz]

Ubiquity of planets and diversity of planetary systems: Origin and Destiny of multiple super Earths and gas giants.

Planetary astrophysics is the most rapidly advancing field in the astronomical community today. Planetary census suggest they are common and their mass- period distribution is a function of the mass and metallicity of their host stars. The diverse and intriguing kinematic properties of multiple planetary systems are likely to be the direct consequence of both the boundary condition of their natal disks and the long-term evolution of nonlinear dynamical systems. I will show how the emergence of super-Earth is a robust process whereas the formation of gas giant planets is a threshold phenomena. The topics to be discussed include physical barriers in the planet building process, the role of migration in their evolving natal disks, planets' interaction with each other and with their host stars. I will also discuss some key observations which may provide quantitative tests for planet formation theories and new clues on the dynamical evolution and internal structure of planets.

82014-11-26 Wed
14:20~15:20
R1203
Jay Farihi
[UCL]

Archaeology of Extrasolar Terrestrial Planetary Systems

We now stand firmly in the era of solid exoplanet detection via Kepler and other state of the art facilities. Yet the empirical characterization of these most intriguing planets is extremely challenging. Transit plus radial velocity information can yield planet mass and radius, and hence planet density, but the bulk composition remains degenerate and completely model−dependent. Currently, the abundances of a handful of exoplanet atmospheres can be estimated from transit spectroscopy, or observed directly via spectroscopy, but probing only the most tenuous outer layers of those planets. Fortunately, as demonstrated by Spitzer, and complementary ground−based observations, debris disk−polluted white dwarfs can yield highly accurate information on the chemical structure of rocky minor planets (i.e. exo−asteroids), the building blocks of solid exoplanets. The white dwarf distills the planetary fragments, and provides powerful insight into the mass and chemical structure of the parent body. This archaeological method provides empirical data on the assembly and chemistry of exo-terrestrial planets that is unavailable for any planetary system orbiting a main−sequence star. In the Solar System, the asteroids (or minor planets) are leftover building blocks of the terrestrial planets, and we obtain their compositions -- and hence that of the terrestrial planets -- by studying meteorites. Similarly, one can infer the composition of exo-terrestrial planets by studying tidally destroyed and accreted asteroids at polluted white dwarfs. I will present ongoing, state of the art results using this unconventional technique, including the recent detection of terrestrial-like debris in the Hyades star cluster, as well as the detection of water-rich planetesimals that may represent the building blocks of habitable exoplanets.

92014-11-20 Thu
14:20~15:20
R1203
I-Ting Ho
[University of Hawaii]

Dissecting galaxies with integral field spectroscopy: current large surveys, near future and beyond

Large integral field spectroscopy (IFS) surveys in the past 5 years have drastically improved our understanding of how galaxies evolve over cosmic time. Building on top of the large fibre spectroscopy surveys such as SDSS, DEEP2, and 2dF surveys, new IFS surveys have started to change the way we observe galaxies, from 1D to 3D. In this talk, I will first give an overview of the current, major integral field spectroscopy surveys in the local Universe (z<0.05). I will then focus on the SAMI Galaxy Survey, an on-going IFS survey on the 4-m Anglo-Australian Telescope. The SAMI Galaxy survey will deliver a final sample of 3,000 galaxies, and we have observed ~1,000 galaxies so far. I will present an array of exciting science results published by the SAMI Galaxy Survey team in the past 1-2 years. I will end the talk by presenting results from my on-going thesis dissertation on chemical evolution, inflows, and outflows using IFS data.

102014-11-19 Wed
14:20~15:20
R1203
Toshifumi Futamase
[Tohoku University]

Lens Statistics with Gravitationally Lensed Yet Morphologically Regular Images

GRAMORs are strongly magnified lensed images with small distortion. One example is discovered in a cluster MACS J1149.5+2223 in 2009. We investigate the lens statistics of GRAMORs in detail. Assuming NFW profile for our sample of clusters, we calculate the expected number and redshift distribution of GRAMORs using parameters given by COSMOS data for the number density of the background galaxy. Our model of the cluster placed at z=0.544 and the background galaxies with WMAP 5 cosmology predicts the redshift of GRAMOR at z~1.49 which is close to the observed z=1.4906. It is found that the probability distribution function of GRAMORs depends strongly on the existence of the dark energy and maybe useful for constraining the nature of dark energy.

112014-11-18 Tue
14:20~15:20
R1203
Aravind Natarajan
[University of Pittsburgh]

The End of the Dark Ages

The study of reionization is crucial to our understanding of the nature of the earliest luminous objects, and the formation of the first galaxies. In the coming years, experiments measuring the 21 cm radiation background and the cosmic microwave background will provide data that can probe reionization, and shed light on theories of structure formation. We describe a new radio experiment that attempts to measure the redshifted 21cm brightness temperature in the frequency range 50-120 MHz, i.e. at redshifts 10

122014-11-11 Tue
14:20~15:20
R1203
Claudio Grillo
[University of Copenhagen]

The dark-matter haloes of massive galaxies and clusters of galaxies

The physics of gravitational light deflection, or gravitational lensing, offers a great variety of applications in several fields of astrophysics. In particular, in the strong lensing regime, observations of multiple images of background sources created by intervening mass concentrations provide a unique opportunity of measuring very precisely the total mass of these intervening lenses. The combination of strong gravitational lensing and stellar population models has turned out to be an invaluable tool to disentangle the luminous and dark-matter components in the inner regions of distant galaxies and clusters of galaxies. I will show how, by using these techniques on unprecedented data obtained with the Hubble Space Telescope and the Very Large Telescope, we have been able to investigate the properties of the dark-matter haloes and subhaloes of massive lens early-type galaxies and galaxy clusters in the CASSOWARY and CLASH surveys.

132014-11-07 Fri
14:20~15:20
R1203
Alina Kiessling
[JPL]

Measuring Dark Energy to 1% Accuracy Using Cosmological Simulations

The nature of Dark Energy, thought to be driving the accelerating expansion of the Universe, is one of the most compelling mysteries in all of science. Determining the equation-of-state of Dark Energy to 1% accuracy is currently a leading goal for many planned cosmological surveys, such as NASA's Wide-Field Infrared Survey Telescope (WFIRST), ESA's Euclid and the Large Synoptic Survey Telescope (LSST). Numerical simulations of structure formation are required to make predictions for these surveys and to help mitigate systematics. My SUNGLASS pipeline (Simulated UNiverses for Gravitational Lensing Analysis and Shear Surveys) is able to produce Monte Carlo suites of numerical simulations and rapidly generates mock weak lensing galaxy shear catalogues. These catalogues are being used to investigate astrophysical systematics, to generate accurate covariance matrices that account for the non-linear nature of the Universe and as an integral part of end-to-end simulation pipelines - each element being essential to the measurement of the Dark Energy equation-of-state to 1% in future telescope missions. In this talk, I will discuss SUNGLASS and its vital role in Dark Energy telescope mission development and analysis.

142014-11-06 Thu
14:20~15:20
R1203
Jason Rhodes
[JPL]

WFIRST and Euclid

Dark energy, the name given to the cause of the accelerating expansion of the Universe, is one of the most profound mysteries in modern science. Current cosmological models hold that dark energy is currently the dominant component of the Universe, but the exact nature of dark energy remains poorly understood. There are ambitious ground-based surveys underway that seek to understand dark energy and NASA is participating in the development of significantly more ambitious space-based surveys planned for the next decade. NASA is providing mission-enabling technology to the European Space Agency‘s (ESA) Euclid mission in exchange for US scientists to participate in the Euclid mission. NASA is also developing the Wide Field Infrared Survey Telescope-Astrophysics Focused Telescope Asset (WFIRST-AFTA) mission for possible launch in ˜2023. WFIRST was the highest ranked space mission in the Astro2010 Decadal Survey and the AFTA incarnation of the WFIRST design uses a 2.4m space telescope to go beyond what the Decadal Survey envisioned for WFIRST. Understanding dark energy is one of the primary science goals of WFIRST-AFTA. I’ll discuss the status of Euclid and WFIRST and comment on the complementarity of the two missions. I’ll also briefly discuss other, exciting science goals for WFIRST, including a search for exoplanets using both microlensing and a dedicated coronagraph.

152014-11-05 Wed
14:20~15:20
R1203
Gregg Hallinan
[Caltech]

Space Weather Beyond Our Solar System

Magnetic activity has played a key role in the formation and angular momentum evolution of our Sun and continues to power its radio and high energy output. The associated radiative output and magnetized plasma outflow (solar wind) dominates the local space environment of solar system planets, including Earth, particularly during flares and CMEs. Radio observations are a powerful trace of these phenomena, both through the radio bursts produced during flares and CMEs and the low frequency auroral radio emission produced by magnetized planets experiencing magnetic storms, the latter a key diagnostic for the presence and strength of planetary magnetic fields. I will talk about new experiments at Caltech's Owens Valley Radio Observatory (OVRO), dedicated to the detection of such space weather on nearby stellar and planetary systems. These includes the Starburst program, dedicated to the detection and imaging of coronal mass ejections on nearby stars, and the Owens Valley Long Wavelength Array, which aims to detect the auroral radio emissions from nearby exoplanets. The latter is particularly innovative, consisting of 288 antennas, combined to image the entire viewable sky every second from 25-85 MHz. This facility recently saw first light and is currently aiming to provide the first measurement of magnetic fields on extrasolar planets. Finally, I will also discuss the recent detection of similar aurorae, both optical and radio, from brown dwarfs, which has allowed us to place the strongest constraints yet achieved on dynamo theory in the substellar regime.

162014-10-30 Thu
14:20~15:20
R1203
Kiyo Masui
[University of British Columbia]

Large-scale structure with the Canadian Hydrogen Intensity Mapping Experiment (CHIME)

The Canadian Hydrogen Intensity Mapping Experiment (CHIME) proposes to map the large-scale structure of the Universe in three dimensions by detecting the redshifted 21 cm emission from neutral hydrogen. I will introduce the CHIME instrument, its science goals, and some of the challenges it faces going forward with a focus on data analysis.

172014-10-29 Wed
14:20~15:20
R1203
Xiangzhong Zheng
[Purple Mountain Observatory]

Evolution of star-forming galaxies across cosmic time

I will discuss recent observational progress in understanding of the assembly history of galaxies, with particular focus on these actively forming stars. Star-forming galaxies (SFGs) are the dominant population at the cosmic noon z~2-3, and show a rapid decline in SFR and a mild evolution in mass density to the present day. In contrast quiescent galaxies increases in mass density by more than one order of magnitude over the same cosmic epoch, fed by SFGs that quickly turn off their star formation. The feeding and quenching of star formation tend to be dependent on galaxy mass and structure. The corresponding physical mechanisms remain to be understood.

182014-10-22 Wed
14:20~15:20
R1203
Larry Denneau
[University of Hawaii]

Observational constraints on the catastrophic disruption rate of main belt asteroids using data from the Pan-STARRS all-sky survey

The current rate of catastrophic disruptions in the Solar System can be used to constrain models of its formation and evolution. Employing a simple model for an observed catastrophic disruption of an asteroid, we present the results of a search for catastrophic disruptions in the Pan-STARRS all-sky survey. We find that the size of objects disrupting at a rate of once per year in the main belt due to impact is no larger than ~7 m diameter, much smaller (and therefore less frequent) than predicted by contemporary models such as Bottke et al. (2005), who predicted one impact-generated disruption per year at 100 m diameter. We suggest that this discrepancy can be accounted for by rotational disruption of asteroids, found by Jacobson et al. (2014) to be much more frequent that impact-generated disruptions. We estimate that in the near-future, Pan-STARRS and other all-sky surveys may detect as many as 10 disruption events per year. We characterize the efficacy of the PS1 survey in detecting moving objects and other transients, and briefly summarize the capability of current and upcoming surveys to detect similar phenomena. We expand our discussion of future surveys to present an overview of the challenges for data processing of transient events in the era of Pan-STARRS, ATLAS, ZTF and LSST.

192014-10-15 Wed
14:20~15:20
R1203
Albert Kong
[NTHU]

Spider-man vs Transformers: Hunting for the missing black widows

Six years of observations with the Fermi Gamma-ray Space Telescope have revolutionized our knowledge of the gamma-ray pulsar population, leading to the discovery of over 40 millisecond pulsars (MSPs) by combining with deep radio observations. With this growing number of gamma-ray emitting MSPs and by combining multi-wavelength observing facilities, it is now possible to study their properties as a population. In this talk, I will review recent discoveries of "transformer" MSPs that switch between low-mass X-ray binaries and radio MSPs. I will also discuss how multi-wavelength observations reveal a new population of black widow/redback MSPs that provide new insights into MSP's emission mechanisms.

202014-10-14 Tue
14:20~15:20
R1203
Bi-Qing For
[Univ. of Western Australia]

The gaseous features of the Magellanic System

In this talk, I will present the results of a study of high velocity clouds in the Magellanic Stream and the Leading Arm. The study uses the Galactic All-Sky Survey (GASS) and a newly conducted survey data of the Australia Telescope Compact Array (ATCA). The properties of HVCs in the two regions are compared and contrasted in order to study the different mechanisms shaping their structure and evolution. I will also present new discoveries from the study and report ongoing/future surveys on the Magellanic Clouds with state-of-the-art telescopes.

212014-10-08 Wed
14:20~15:20
R1203
Colette Salyk
[NOAO]

Observing the Formation of Planetary Diversity

Planets and planetary systems are incredibly diverse, as evidenced by the unique planets of our solar system, and the large variety of exoplanetary systems. How did this diversity develop? I will discuss our current understanding of how a unified planet formation scenario can explain such an array of planets, and describe the protoplanetary disk observations I have been performing to test these ideas. I will focus in particular on observations of disk chemistry, including its challenges, exciting advances, and future prospects.

222014-10-01 Wed
14:20~15:20
R1203
Min-Su Shin
[University of Oxford]

Applications of machine learning algorithms for reliable detection of groups in astronomical data

Due to increasing size of astronomical data and expected boom of survey projects, it becomes important to detect interesting objects reliably in the large amount of data. I explain the importance of applying machine learning algorithms in future astronomical research. Focusing on application of clustering algorithms to detect groups in data, I introduce a non-parametric Bayesian clustering method and a consensus clustering method which improve reliability of detecting genuine variable sources in time-series astronomical data. I also present a new strategy of time-series data analysis to identify variable sources quickly by using ensemble of clustering methods as the data size grows. Possible applications of the non-parametric Bayesian method are presented for theoretical and observational astronomical research, emphasizing the role of data-driven models.

232014-09-24 Wed
14:20~15:20
R1203
Eva Grebel
[Heidelberg University]

Dwarf Galaxies and Their Role as Building Blocks

Dwarf galaxies are the most common type of galaxy in the Universe and include the most dark-matter-dominated objects known. They offer intriguing insights into evolutionary processes at low halo masses and low metallicities. Moreover, as survivors of a once much more numerous population of building blocks of larger galaxies, they are key to understanding very early star formation processes. The Local Group and particularly the Milky Way's dwarf galaxy entourage offer us the unique possibility to compare in detail dwarf and Galactic populations. This is an important step towards quantifying the magnitude and time scales of dwarf contributions to the build-up of the Milky Way and allows us to test predictions of cosmological theories and hierarchical structure formation.

242014-09-17 Wed
14:20~15:20
R1203
Wei-Ling Tseng
[NTNU]

Exploring Our Solar System with Mass Spectrometry

I would like to introduce my research work, which focuses on exploring 1) the Saturnian system (Cassini mission), 2) Mercury’s exosphere (Bepi-Colombo mission) and 3) Earth’s upper atmosphere (AirCore). 1) The Saturnian system is immersed in the extended clouds of O2, H2O and their fragments 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. Once ionized, these neutrals will be fed into the thermal plasma disk in the magnetosphere. Most of my work is focused on the simulations of the structures and compositions of the neutral clouds of different origins with a plasma chemistry model based on the latest measurements from the Cassini INMS (Ion and Neutral Mass Spectrometer), CAPS (Cassini Plasma Spectrometer) and MIMI (Magnetospheric Imaging Instrument) instruments. 2) Strofio is a neutral mass spectrometer utilizing with electron-impact ionization, part of the SERENA neutral and ionizing particle suite onboard BepiColombo mission, to explore Mercury’s exosphere. Strofio can measure the in-situ composition of exosphere yielding the spatial distribution and temporal variability of neutral particles. The structure and composition of Mercury’s exosphere is bounded to its surface interaction (i.e., ion sputtering and photo desorption) and magnetospheric processes (i.e., plasma precipitation profile on surface). Leading by Dr. S. Livi (PI of Strofio) in SwRI, we vary the ion extraction efficiency with voltage change inside the ionization source of Strofio which can help us retrieve the energy distribution of parent molecules and their fragments. 3) AirCore (developed by Dr. P. Tans in NOAA) is an air collection device that has been used for measuring the vertical profiles of trace gas, such as CO2 and CH4, in Earth’s atmosphere. Molecular diffusion in the tube is slow enough that the collected gas remains ordered, and AirCore can provide a continuous vertical profile of the high-altitude measurements. In SwRI, Dr. M. Mandt’s research group has designed a sample-collection package of the AirCore for high altitude measurements on a variety of platforms (i.e., balloons and sounding rockets etc.), focusing on the possible mass fractionation in the tube due to low air pressure and flight velocity.

252014-09-10 Wed
14:20~15:20
R1203
Chan-Kao Chang
[NCU]

The intermediate Palomar Transient Factory (iPTF) & the 10k Asteroid Rotation Period (10kARP) Project

The Palomar Transient Factory (PTF) is a synoptic survey designed to explore the transient and variable sky. The PTF camera, the former CFHT 12k mosaic camera, mounted on Palomar Observatory’s 1.2-m f/2.44 Oschin Schmidt Telescope, uses 11 CCDs (4096 × 2048 each) to observe 7.26 deg2 of the sky at a time with a resolution of 1.01 arcsec/pixel. The project started its operation in 2009 and stepped into its second phase, iPTF, in 2013. The nominal survey is at R-band, but additional observations are also made at g-band and H alpha band. The standard exposure time per frame is 60 seconds, yielding a 3-sigma limiting magnitude of 20.5 and 21 for R- and g-band respectively. The iPTF has carried out various experiments with different cadences, from a 5-day cadence to 90 seconds. The 10k Asteroid Rotation Period (10kARP) Project is trying to use PTF data to collect 10,000 asteroid rotation periods, from which we try to understand the spin rate distributions for different size asteroids and see whether their distributions are different from their NEA counterparts. In addition, we also try to search super-fast rotator (SFR), which has diameter of several hundreds meter and rotates faster than the “spin barrier” at ∼ 2 hours. Such SFR is very critical to understand the interior structure of asteroid with D>150 m.

262014-09-09 Tue
14:20~15:20
R1203
Yu-Yen Chang
[MPIA]

Stellar Masses and Star Formation Rates for 1M Galaxies from SDSS and WISE

We assemble multi-wavelength photometry for the full SDSS spectroscopic galaxy sample, drawing from the SDSS and WISE surveys, covering the wavelength range 0.4-22 micron. We use the latest modeling techniques to estimate stellar masses and star formation rates. The addition of photometry at > 1 micron improves these measurements as compared to previous SDSS-based estimates. The newly measured star formation rates allow us to test methods to separate early-type (passive) from late-type galaxies (star-forming) galaxies.

272014-09-05 Fri
14:20~15:20
R1203
Chihway Chang
[ETH]

Mapping the Universe — Weak Lensing Maps with the Dark Energy Survey and beyond

Our view of the Universe is distorted due to gravitational lensing. These distortions help us understand the content and history of the Universe. In this talk I will describe some of the early work that is being done with the DES Science Verification data to make the largest contiguous weak lensing maps of the sky to date. I then discuss a variety of exciting topics that can be explored with these maps as we look forward to several large optical surveys coming up in the next decade.

282014-09-03 Wed
14:20~15:20
R1203
Melody Wolk
[University of Hawaii]

Statistical properties of the matter density field

In our current paradigm of the Universe, gravitational instabilities give rise to the large scale structures observed today by hierarchical clustering. Two-point statistics are known to fail at providing a complete description as the actual galaxy distribution is non-Gaussian. Moreover, it has been shown that, beyond the linear regime, high order moments no longer capture all the information encoded in the matter density field. In this talk, I will introduce an optimal "sufficient statistics" in the case of discrete density fields such as the galaxy distribution. This new observable was specially designed to capture all the useful cosmological information. I will describe how it could be applied to one of the current "state of the art" photometric redshift surveys, the CFHTLS Wide, and discuss its efficiency compared to previous method focusing mainly on the power spectrum measurement. I will also present some forecasts of this method for the upcoming large scale structure surveys.

292014-08-26 Tue
14:20~15:20
R1203
Ronin Wu
[University of Tokyo]

Spatially resolved physical conditions of molecular gas and potential star-forming tracers in M83, revealed by the Herschel SPIRE FTS

Since the launch of the Herschel Space Observatory, our understanding about the photo-dissociation regions (PDR) has taken a step forward. In the bandwidth of the Fourier Transform Spectrometer (FTS) of the Spectral and Photometric Imaging REceiver (SPIRE) on board Herschel, ten CO rotational transitions, including J=4-3 to J=13-12, and three fine structure lines, including [CI] 609, [CI] 370, and [NII] 250 micron, are covered. In this talk, I present our findings from the FTS observations at the nuclear region of M83, based on the spatially resolved physical parameters derived from the CO spectral line energy distribution (SLED) map and the comparisons with the dust properties and star-formation tracers. I will discuss (1) the potential of using [NII] 250 and [CI] 370 micron as star-formation tracers; (2) the reliability of tracing molecular gas with CO; (3) the excitation mechanisms of warm CO; (4) the possibility of studying stellar feedback by tracing the thermal pressure of molecular gas in the nuclear region of M83.

302014-08-22 Fri
14:20~15:20
R1203
Jungyeon Cho
[Chungnam National University]

Origin of Cosmic Magnetism: Primordial or Astrophysical?

In usual astrophysical circumstances, magnetic diffusivity is very low and, as a result, magnetic fields lines are tied to fluid elements. Therefore random turbulence motions can efficiently stretch magnetic field lines, which results in amplification of magnetic field. This turbulence dynamo is believed to play important roles in the origin of cosmic magnetism. For turbulence dynamo, a weak seed magnetic field is required. If the seed field has cosmological origin, it could be regarded as uniform (or homogeneous) at the scale of galaxy clusters. On the other hand, if the seed field is ejected from astrophysical bodies, it could be highly localized in space at the beginning. In this talk I'll discuss growth of uniform and localized seed magnetic fields in turbulence. I will demonstrate that growth of both uniform and localized seed magnetic fields in clusters of galaxies is very similar. Therefore, it is difficult to tell whether or not the seed magnetic field has cosmological or astrophysical origin in clusters of galaxies. However, I'll show that it is possible to tell the difference between them in filaments.

312014-08-20 Wed
14:20~15:20
R1203
Masamune Oguri
[University of Tokyo/Kavli IPMU]

Gravitationally lensed supernovae

Gravitationally lensed supernovae are rare but very interesting phenomena. I'll discuss why gravitationally lensed supernovae are unique and useful, and then show that the unusual supernova PS1-10afx found in Pan-STARRS1 was in fact a normal type Ia supernova magnified 30 times by a foreground galaxy, representing the first discovery of strongly lensed supernovae.

322014-08-13 Wed
14:20~15:20
R1203
Shan Huang
[ASIAA]

HIghMass - High HI Mass, HI rich Galaxies at z~0

We present the first results of the study of a set of exceptional HI sources identified in the 40% ALFALFA extragalactic HI survey catalog as being both HI massive and having high gas fractions for their stellar masses: the HIghMass galaxy sample. We analyze multiwavelength data to understand the nature of their relatively underluminous disks in optical and to test whether their high gas fractions can be tracked to higher dark matter halo spin parameters or late gas accretion.

332014-07-30 Wed
14:20~15:20
R1203
Seong Jin Kim
[Seoul University]

Infrared point source catalogue of the AKARI NEP-Wide Survey

This talk introduces a photometric catalog of infrared (IR) sources based on the North Ecliptic Pole Wide field (NEP-Wide) survey carried out by AKARI, which is an infrared space telescope. The NEP-Wide survey covered 5.4 sq-deg circular area, using nine photometric filter-bands continuously covering the wavelength range from 2 to 25 μm. During the data reduction, extensive efforts were made to reduce possible false/artificial objects. The number of detected sources varied depending on the filter band: with about 109 000 sources cataloged in the near-infrared bands, up to 18 500 sources in the mid-infrard (MIR) bands. The estimated 5σ detection limits are approximately 21 mag (mag) in the 2μm bands, 19.5 mag in the 7μm, and 18.8 mag in the 15 μm bands in the AB magnitude. To construct a reliable source catalog, all of the detected sources were examined by matching with those in other wavelength data, including optical and ground-based NIR bands. The final catalog contains about 114 800 sources detected in the IRC filter bands. At the end of this talk, the properties of the sources are presented and following studies base on this catalogue are briefly introduced.

342014-07-16 Wed
14:20~15:20
R1203
Geoffrey Bower
[ASIAA]

Two Serendipitous Probes of Sagittarius A*: The Galactic Center Pulsar and The G2 Gas Cloud

High resolution very long baseline interferometry (VLBI) images of nearby massive black holes have the power to address fundamental questions about the physics of black holes. This includes the most accurate constraints on the mass density of the black hole, detection of the black hole spin, and exploration of extensions to general relativity (GR). In particular, Event Horizon Telescope (EHT) observations will probe Sgr A* and M87, the two sources with the largest angular diameter black holes on the sky, over the coming years with increasing sensitivity and accuracy in imaging. Unfortunately, we do not fully understand the physical processes that are driving accretion and outflow in these sources. To address the fundamental black hole physics questions, we need to develop a deeper knowledge of the astrophysics of these sources. The periastron passage of the G2 gas cloud with Sgr A* at ~1000 Schwarzschild in Spring of 2014 gives us an unprecedented opportunity to study a wide range of astrophysical models for accretion and outflow. I describe here observations from millimeter to X-ray wavelengths that enable us to create the necessary context for understanding physics at a few Schwarzschild radii. These include centimeter wavelength VLBI, millimeter polarimetry, and light curve analysis. The serendipitous discovery of the Galactic Center magnetar, SGR 1745-29, has provided a powerful new probe of the Galactic Center environment, including the gas density, magnetic field strength, and nature of the interstellar scattering screen. The discovery also raises important questions about the detectability of pulsars in close orbit to Sgr A* and the pulsar population in the Galactic Center overall.

352014-07-11 Fri
14:20~15:20
R1108
Yi-Kuan Chiang
[UT Austin]

Ancient Light from Young Cosmic Cities: Proto-clusters of Galaxies

Proto-clusters are progenitor large-scale structures of galaxy clusters in the epoch of their active formation (z>~2). They potentially provide direct probes of the interplay between dark matter structure formation, cluster formation, and galaxy evolution. However, a systematic study is difficult due to the small and heterogeneous sample observed to date, and the lack of guidance from detailed theoretical studies. To facilitate a statistical understanding, I will present two aspects of proto-cluster studies in simulations and observations. First, by tracking the evolution of a large set of simulated clusters, we parameterize and extract the physical properties and observational signatures of proto-clusters predicted in LCDM models. We show that cluster progenitors can already be identiﬁed at very high redshifts by mapping large-scale (~5-30 cMpc) galaxy distributions. Second, to demonstrate the potential of current and future galaxy redshift surveys and provide targets for follow-up studies, we perform a proto-cluster search in the COSMOS field at 2~2 in the next decade as the requiring observing facilities/surveys are coming online.

362014-07-10 Thu
14:20~15:20
R1203
Garrett Karto Keating
[Berkeley]

The Undiscovered CO: Charting the Molecular Gas of the Universe at High Redshift

Molecular gas is a vital component of galactic evolution and star formation; however, its distribution among average galaxies at high redshift is so poorly understood that models of the mean abundance of CO for z≥2 span orders of magnitude. Direct detection methods (i.e. imaging techniques) at these redshifts have only found molecular gas in the most massive and luminous of systems (Mgas=1010 M ⊙ ; SFR=100 M⊙ yr-1), whereas the bulk of the molecular gas is expected to be in the unseen masses of smaller galaxies (Mgas~108 M ⊙; SFR~1 M⊙ yr-1). Theory predicts these smaller galaxies are detectable as an integrated ensemble with the technique of “intensity mapping”. This technique utilizes measurements of the power in different Fourier (or wave) modes in a volume of space, which are combined to construct a 3D power spectrum. The Sunyaev-Zel'dovich Array (SZA), a subset of CARMA, offers an opportunity to explore molecular gas at high redshift through intensity mapping. The SZA, an 8-element closely packed array, is capable of observing CO (J=1⇒0) at z=2.3-3.3. We present results from of our current search for CO at z≈3, a survey of 44 fields with 880 hours of integration time. Additionally, we will present preliminary results from recent and ongoing observations of GOODS-North, a field ripe with opportunities for cross-correlation. Combined, these two datasets offer complementary perspectives (wide and shallow versus deep and narrow) to explore systematics and fidelity. With these results, we will present our current constraints on the CO luminosity function at high redshift.

372014-07-09 Wed
14:20~15:20
R1203
Luc Simard
[HIA]

The Thirty-Meter Telescope: Science and Instrumentation for a Next Generation Observatory
382014-07-08 Tue
14:20~15:20
R1203
Luc Simard
[HIA]

ANUENUE: A 4D Superconducting MKID Camera for CFHT
392014-06-18 Wed
14:20~15:20
R1203
Patrice Theule
[Aix-Marseille Universite]

Formation of Complex Molecules in Interstellar Medium

Complex molecules could be formed in ice on interstellar grains. The presence of interstellar ices of common molecules (CH3OH, H2O, CO2, CO, CH4, NH3, H2CO,,,) are observed unumbiguously as infrared bands, and are well documented. These volatile, relatively simple molecules likely react to form more complex organic molecules (such as amino acids) that are difficult to explain by gas-phase theory. Laboratory astronomy attempts to replicate the formation of the complex molecules through experiments under the interstellar conditions from the detected interstellar ice conpounds. Complex molecules such as NH2CH2COOH (glycine), C6H15N3 (formaldehyde methylamine trimer), NH2COOH (carbamic acid) are formed in the laboratory experiments. These experiments do not use special trigger such as illumination of X-ray or cosmic ray (high energy particles). The most abundant interstellar ice is H2O (water) by order of magnitude. The reactants are expected to be trapped in water ice. The reactions need to happen in the water ice at temperatures 100 - 200 K expected near protostars.

402014-06-12 Thu
14:20~15:20
R1203
Soko Matsumura
[Univ. of Dundee]

Effects of Dynamical Evolution of Giant Planets on Survival of Terrestrial Planets

The orbital distributions of currently observed extrasolar giant planets allow marginally stable orbits for hypothetical, terrestrial planets. However, many of these giant planets have eccentric orbits that indicate dynamical instability in the past. If this is the case, many such systems may not have additional planets on the "stable" orbits, since past dynamical evolution could have removed them. We numerically test this hypothesis by simulating the effects of early evolution of multiple giant planets on the orbital stability of the inner, sub-Neptune-like planets. We find that secular perturbations from giant planets can remove test particles at least down to 10 times smaller than their minimum pericenter distance. Our results indicate that, unless the dynamical instability among giant planets is either absent or quiet like planet-planet collisions, most test particles down to ~0.1 AU within the orbits of giant planets at a few AU may be gone. We find a good agreement between our numerical results and the secular theory as well as with the observations.

412014-06-11 Wed
14:20~15:20
R1203
Tomotsugu Goto
[NTHU]

Probing cosmic re-ionization with gamma ray burst 130606A at z~5.91

Understanding the cosmic re-ionization is one of the key goals of the modern observational cosmology. The bright UV continuum of high-redshift QSOs have been used as a background light source to probe the cosmic re-ionization since it is absorbed by neutral hydrogen. However, the original QSO continuum were difficult to be fit, and thus have been the largest source of uncertainty. We present the first gamma ray burst used for Gunn-Peterson re-ionization test. With one of the quickest follow-up observation using VLT/X-shooter, we obtained high S/N spectrum of a gamma ray burst 130606A. Our measurements have much smaller uncertainty than QSOs because of relatively flat, and simple synchrotron emission continuum of GRB afterglows.

422014-06-04 Wed
14:20~15:20
R1203
Chao-Lin Kuo
[Stanford]

Stage-4 CMB experiment: An all-sky survey of B-mode polarization at arcminute resolution

With the measurements of B-mode polarization by BICEP2, SPTpol, and POLARBEAR, the field of CMB is entering an exciting "B-mode cosmology" era. I will describe an ambitious program to survey the whole sky at 1'-2' resolution with a depth of 1-uK-arcminute at multiple frequency. The main science goals are inflationary physics, cosmic neutrinos, dark energy, and a high-fidelity lensing deflection map that can be cross correlated with other astronomical tracers. This program, known as the stage-IV CMB experiment ("CMB-S4") has received strong endorsements by the US particle physics project prioritization panel in May 2014.

432014-05-28 Wed
14:20~15:20
R1203
Neal Evans
[U. Texas at Austin]

Star Formation: From Far to Near

I will discuss developments in what controls star formation, zooming in from extragalactic perspectives to studies within galaxies, within the Milky Way, and finally to nearby molecular clouds. Relations between gas and star formation (e.g., Kennicutt-Schmidt laws) will be considered, along with the role of dense gas and threshold effects.

442014-05-26 Mon
14:20~15:20
R1203
Sze-leung Cheung
[International Outreach Coordinator, IAU Office for Astronomy Outreach]

International Year of Light 2015, Public Naming of Exoplanets and IAU Office for Astronomy Outreach

The International Astronomical Union (IAU) Office for Astronomy Outreach (OAO) is an IAU new office hosted at National Astronomical Observatory of Japan (NAOJ) at Tokyo. After the International Year of Astronomy 2009, IAU decided to establish the OAO to coordinate the international astronomical outreach efforts. Two major campaigns that OAO are running are the International Year of Light 2015 and the Public Naming of Exoplanets. IAU is one of the supporting organization of the International Year of Light 2015 (IYL2015), and one of the IYL2015 cornerstone project is “Cosmic Light”, which connect astronomy to light. OAO is the central hub of coordination for the Cosmic Light cornerstone. On the other hand, IAU has also decided to name exoplanets, however, using a different approach than the naming of solar system bodies like asteroids or comets, the naming of exoplanet will involve public voting and proposal nominations from public organizations including planetariums.

452014-05-22 Thu
14:20~15:20
R1203
Debra Fischer
[Yale University]

The Search For 100 Earths

The search for planets orbiting nearby stars has been one of the greatest success stories of the past decade, with hundreds of discoveries being made using Doppler, transit, microlensing, and direct imaging techniques and thousands of candidates detected with NASA’s Kepler mission. Exoplanet detections have launched a subfield of astronomy that includes host star characterizations, measurements of planet radii and density, studies of atmospheres, interior structure, formation theory, and orbital evolution. The search for exoplanets is motivated by the question of whether life exists elsewhere. This drives our interest in the detection of planets that are similar to our own world: rocky planets with the potential for liquid surface water and plate tectonics; worlds that might harbor life that we can recognize. Importantly, we will need to discover not just a few, but hundreds of these worlds to eventually gain a statistical understanding of whether life is rare, common, or ubiquitous and ground-based telescopes offer an ideal platform for carrying out decade-long surveys. It is critical for follow-up studies (imaging, atmospheric studies) that these planets orbit nearby stars. In this talk, I will discuss how we plan to take what we've learned and push on to the next frontier: our plans for a next generation spectrograph, EXPRES, to carry out a search 100 Earths with the Discovery Channel Telescope.

462014-05-21 Wed
14:20~15:20
R1203
Phil Armitage

Simulating and observing turbulence in protoplanetary disks

The strength and nature of turbulence in astrophysical disks is one of the main uncertainties in both accretion disk theory and planet formation. I will present numerical simulations of protoplanetary disk turbulence, which include the non-ideal magnetohydrodynamic effects that damp turbulence in cool poorly-ionized disks. The results hint at a critical role for large-scale magnetic fields, which may be remnants of the star formation process. Sub-mm observations with the SMA and ALMA now approach the acuity needed to measure the turbulent broadening of molecular lines in protoplanetary disks, and I will show predictions for what we may expect to see.

472014-05-20 Tue
14:20~15:20
Physics 104
Phil Armitage

Formation and Discovery of Extrasolar Planetary Systems

The discovery of several thousand extrasolar planets allows us to assess, for the first time, whether the Solar System is a typical outcome of the planet formation process. I will review the current status of exoplanet observations, and their implications for the theoretical understanding of how terrestrial and gas giant planets form. Observations suggest that the early evolution of many planetary systems is surprisingly violent, and I will argue that this implies the existence of a new, as yet unidentified, class of terrestrial planets. At earlier times the formation mechanism of the first asteroid-sized bodies remains unknown, and I will discuss recent progress toward resolving this mystery.

482014-05-14 Wed
14:20~15:20
R1203
Naoki Yoshida
[University of Tokyo]

Matter distribution around galaxies and the nature of dark matter

Gravitational lensing is a powerful method to probe matter distribution in the universe. We combine large observational data from SDSS and CFHTLens and cosmological simulations to study the distribution of dark matter around galaxies. Our method can be used to "measure" the mass of dark matter halos that host SDSS main galaxies, to derive cosmological parameters such as Omega_matter, and to place constraints on the annihilation cross-section of dark matter. For the latter study, we also use data from the Fermi all-sky gamma-ray map. Ongoing wide-field surveys, most notably Subaru-HSC, will significantly improve the above estimates and constraints. I discuss theoretical challenges to use the large set of data in the coming few years.

492014-05-13 Tue
14:20~15:20
Physics 104
Naoki Yoshida
[University of Tokyo]

The dark ages of the universe

One of the milestones in the cosmic history is the formation of the first generation of stars and hydrogen reionization. The standard theory of cosmic structure formation predicts that the first stars were born about a few hundred million years after the Big Bang. The dark Universe was then lit up once again, and eventually filled with ultraviolet photons emitted from stars and galaxies. Recent astronomical observations discovered distant galaxies and super-massive blackholes that were in place when the age of the universe was less than one billion years old. How were the galaxies formed, and what are the origin of the massive blackholes? The key to these interesting question lies probably in the formation of the first stars. I present the results from super-computer simulations that follow self-consistently the formation of protostars through to the early stages of a main-sequence star with thermonuclear burning. The characteristic mass of the first stars is estimated from such simulations. I discuss implications for the formation of early blackholes and Galactic metal-poor stars. Finally I propose to use future wide-field infrared surveys to detect the supernova explosions of the first stars.

502014-04-30 Wed
14:20~15:20
R1203
Yosuke Mizuno
[NTHU]

Magnetic field amplification and saturation in turbulence behind a relativistic shock

Afterglows of gamma-ray bursts (GRBs) are believed to require magnetic fields much stronger than that of the compressed preshock medium. As an alternative to microscopic plasma instabilities, amplification of the field by macroscopic turbulence has been proposed. We have investigated via 2D relativistic magnetohydrodynamic simulations the long-term evolution of turbulence created by a relativistic shock propagating through an inhomogeneous medium. In the post-shock region, magnetic field is strongly amplified by turbulent motions triggered by pre-shock density inhomogeneities. The amplified magnetic field evolved into a filamentary structure. The magnetic energy spectrum was flatter than the Kolmogorov spectrum and indicated that the so-called small-scale dynamo was occurring in the postshock region. Using a long-simulation box we have followed the magnetic field amplification until it is fully developed and saturated. The turbulent velocity is sub-relativistic even for a strong shock. Magnetic field amplification is controlled by the turbulent motion and saturation occurs when the magnetic energy is comparable to the turbulent kinetic energy. We found that magnetic field amplification and saturation depend on the initial strength and direction of the magnetic field in the pre-shock medium, and on the shock strength.

512014-04-24 Thu
14:20~15:20
R1203
James O. Chibueze
[NAOJ]

Outflow-associated Massive Young Stellar Objects: ALMA/VLA Comparative Study of G35.20–0.74N and G35.03+0.35

Mysterious issues of massive star formation can be unveiled in multi-wavelength comparative observational studies of MSFRs. In a comparative study of very large array (VLA) centimeter and ALMA millimeter observations of G35.20–0.74N and G35.03+0.35. In G35.20–0.74N, we detected a single 1.3 cm continuum (free-free) emission in B-north, coinciding in position with the 3.6 cm and 0.86 mm continuum, but neither 1.3 cm nor 0.86 mm continuum was found toward B-south. This implies that the driving source(s) of B core is within or near B-north, and B-south is not a YSO. The geometrical alignment of B-south with the north-south jet traced at 3.6 cm tends to suggest that B-south could be a newly ejected, flux-density enhanced clump in the jet. In G35.03+0.35, we detected multiple 0.86 mm cores and also prominent hot shocked gas traced by SiO around the southeast 44 GHz CH3OH, NH3 (3,3) and (6,6) maser strong peaks of Brogan et al. (2011). This could be a signature of the high-velocity gas outflow, associated with NE1 millimeter core, traced by 12CO.

522014-04-16 Wed
14:20~15:20
R1203
Chiranjib Konar
[ASIAA]

Jet and accretion physics in radio galaxies: theory vs. observations

Radio galaxies are the good laboratories to study the AGN accretion and jet physics. Hundred-kpc scale radio galaxies can be hosted by spirals too. They can be episodic in jet activity. In our recent work we have made progress in addressing some of the fundamental questions related to the jet physics and the cause of episodic jet formations in radio loud AGNs. All episodic radio galaxies in our sample show two episodes. I will discuss about what is the most consistent model for the particle acceleration at the jet shocks. I will emphasize how the application of jet dynamics and particle acceleration physics leads to various interesting and important conclusions related to extragalactic jets. I will also discuss the mode of accretion in the episodic radio galaxies and present our recent results extracted from X-ray (XMM), SDSS and WISE data.

532014-04-09 Wed
14:20~15:20
R1203
Tom Barclay
[NASA ames]

Exoplanet discoveries enabled by the precision photometry of Kepler

The Kepler spacecraft has reinvented the field of exoplanetary science. In this talk I will highlight what is possible with such high quality data. For large planets relativistic Doppler boosting can enable the determination of a planet’s mass purely from photometry. Kepler also has revealed planets smaller than any in our own Solar System, I how how planets that block just 20 in every million photons coming from the star. Finally, I will discuss progress made toward finding the first Earth-like exoplanet.

542014-04-03 Thu
14:20~15:20
R1203
Khee-Gan Lee
[MPIA]

3D Mapping of the IGM on 〜Mpc scales with Ly-a forest Tomography

The Lyman-alpha forest absorption at z>2 can, with a sufficient density of background sightlines, be used to create 3D tomographic maps of large-scale structure. The Cosmic Lyman-Alpha Program for the Tomographic Reconstruction of Absorption Probes (CLAPTRAP) will be the first survey to attempt this technique. We aim to obtain spectra for a background grid of faint quasars and bright LBGs at 22, on ~Mpc scales. In conjunction with the rich multi-wavelength data from the COSMOS survey, these maps will facilitate the study of galaxies in the context of their large-scale environment, reveal the topology of the universe at high-redshifts, and allow the direct detection of galaxy protoclusters at the intersections of the cosmic web. In the near-future, Subaru PFS will be able to map out large areas of the high-redshift universe using this technique.

552014-04-02 Wed
14:20~15:20
R1203
Denise Gabuzda
[University College Cork]

Using Faraday Rotation to Probe the Magnetic Field Structure of AGN Jets

562014-04-01 Tue
14:20~15:20
Physics 204
Chao-Lin Kuo
[Stanford]

BICEP2 results, implications, and future

The BICEP2 team has just announced the detection of degree-scale B-mode polarization of the CMB, consistent with the imprint of inflationary gravitational waves. r=0 model is ruled out at very high significance. BICEP2 is the second generation in the BICEP/Keck series of small refractor experiments. I will discuss the immediate prospect of confirming and expanding BICEP2's discovery by Keck Array and BICEP3. A dedicated program that covers more sky can significantly reduce the uncertainties on tensor amplitude, putting models of inflation to further test.

572014-04-01 Tue
10:30~11:30
R1203
Aglaé Kellerer
[Durham University]

Angular resolution in astronomy: present, future and beyond

This talk will be divided into two grand themes: the development of novel adaptive optical (AO) correction systems for the next generation of telescopes, and the application of quantum optical mechanisms to astronomy. Advanced adaptive optics systems have kept ground based telescopes at the forefront of astronomical research. However, as the telescopes further increase in size current AO systems begin to be inadequate. The future extremely large telescopes require new approaches, and I will discuss some of these during my talk. I will notably argue in favor of wavefront sensors that determine the phase directly. The aim of adaptive optical systems is to reach the diffraction limit. This limit is considered as the absolute boundary for the angular resolution of a telescope; it can, however, be overcome through non-linear processes, such as stimulated emission and quantum entanglement. I will examine the possibility of overcoming the diffraction limit of a telescope through heralded photon cloning processes (http://dx.doi.org/10.1051/0004-6361/201322665). The main message will be the possibility in principle to improve the angular resolution of a telescope beyond the diffraction limit, and thus to achieve high-angular resolutions even with moderately sized telescopes.

582014-03-31 Mon
14:20~15:20
R1203
Shane O'Sullivan
[THE UNIVERSITY OF SYDNEY]

New insights into AGN jet and lobe physics from radio spectropolarimetry

New and upgraded radio telescopes, with broadband radio receivers, are enabling high-precision multi-frequency polarization and Faraday rotation measurements across a wide range of jet scales. Spectropolarimetric techniques such as Faraday rotation measure synthesis and QU-fitting have been developed to take advantage of these new capabilities, providing key insights into the magnetic field structure, particle composition and environmental impact of AGN jets and lobes. I will describe some recent results from radio spectropolarimetric studies of AGN jets and lobes, before presenting future radio telescope projects that will revolutionise our view of the polarized sky and with it our understanding of AGN jets and lobes.

592014-03-26 Wed
13:20~14:20
R1203
Martin Bureau
[Oxford]

Molecular Gas in Early-type Galaxies. I. Kinematics

I will demonstrate that, contrary to expectations, early-types galaxies contain a significant amount of cold molecular gas, and that the spatially-resolved kinematics of this gas can be used to establish its origin. More importantly, the molecular gas turns out to be an excellent, arguably the best tracer of the circular velocity in early-type galaxies, thus allowing accurate total/dynamical mass measurements. I will exploit this principally in two ways. First, to show that an accurate CO Tully-Fisher (luminosity-circular velocity) relation can easily be derived for early-type galaxies. This opens the way to probe the mass growth of galaxies of all types to significant redshits, with a unique and simple method. Second, to show that CO can be used to accurately measure the mass of the supermassive black holes lurking at galaxy centres. This opens the way for literaly hundreds of measurements across the Hubble sequence, potentially revolutionising our understanding of the co-evolution of galaxies and black holes.

602014-03-21 Fri
14:20~15:20
R1203
Maarten Baes
[U. Ghent]

Dust radiative transfer: modelling the complex interplay between dust and starlight in galaxies

Dust grains play a special role in producing and processing radiation. They are efficient at absorbing and scattering UV through NIR photons and then reradiating the absorbed energy in the infrared and submm wavelength range. Understanding the intrinsic properties of these objects, including the dust itself, therefore requires 3D dust radiative transfer calculations. Unfortunately, the 3D dust radiative problem is nonlocal and nonlinear, which makes it one of the hardest challenges in computational astrophysics. To tackle this problem, we have developed SKIRT, an efficient Monte Carlo code designed to treat continuum radiative transfer problems in dusty systems. It handles any 3D geometry without limitation, and offers a full treatment of absorption, multiple anisotropic scattering and thermal dust emission. I present a number of recent applications of the SKIRT code on the different dusty galaxies. I will discuss the effects of dust attenuation on the apparent structural parameters, where we show that even a modest amount of dust attenuation can bias the derivation of bulge-to-disc ratio by a factor of two, even for face-on orientations. I will present the results of a detailed radiative transfer study of a sample of edge-on spiral galaxies selected, based on the FitSKIRT tool around SKIRT. We find that, on average, the dust disc in spiral galaxies is about 75% more radially extended but only half as thick as the stellar disc. The distribution of optical depths indicates that some spiral galaxies are relatively opaque even when seen face-on. Furthermore, we use our models as an input to construct the entire spectral energy distribution using fully panchromatic radiative transfer simulations. We compare the infrared/submm fluxes predicted by our models to the actual values observed with Herschel. The implications of these findings on the dust energy balance, obscured star formation and the dominant heating sources of dust in in spiral galaxies are discussed.

612014-03-20 Thu
14:20~15:20
R1203
Hitoshi Hanami
[Iwate University]

Unveiling Dusty Star Formation and AGN Activities in high-z LIRGs

A major issue in observational cosmology is to reconstruct growth history of galaxies and Active Galactic Nuclei (AGNs), which can be traced with {\sf Luminous InfraRed Galaxies (LIRGs)} detected by the infrared observing satellites as the ISO, the {\it Spitzer}, the AKARI, and the {\it Herschel}. In general, their IR emissions are also expected not only with Star Formation (SF) but also with AGN activities, which possibly regulate or quench the SF with their feedback mechanism in galaxy evolutions. Even though {\bf MIPS selected LIRGs} at $z\sim 2$ have been frequently \r\nstudied for checking the connection between the SF and AGN activities, their IR StarBurst(SB)-AGN distinction at $z\ sim 1$ is limited since the strongest Polycyclic Aromatic Hydrocarbon ( PAH) $7.7(\sim8)\mu$m emission enters in an MIR photometry gap between the IRAC and the MIPS on the {\it Spitzer}. With the Spectral Energy Distribution (SED) analysis of {\bf unique AKARI multi-MIR photometry covering this gap}, however, we could classify LIRGs up to $z\\simeq2$ into PAH luminous starburst-dominated {\sf (sb-LIRGs)}, starburst-AGN {\ sf (s/a-LIRGs)}, and AGN-dominated {\sf (agn-LIRGs)} populations with using a ratio of monochromatic luminosity at $8\mu$m of the PAH emissions from dusty starbursts to that at $5\mu$m of continuum emissions from AGN dusty tori; $\nu L_{\nu} (8\mu \mbox{m})/\nu L_{\nu} (5\mu \mbox{m})$ (Hanami+2012). The SF/AGN distinction of {\sf AKARI classified LIRGs} becomes also confirmed by using the {\it CXO} (Krumpe+ 2014) and the {\it Herschel} (PI: S.Serjeant). Alternative causes for the PAH weakness on $\nu L_{\nu} (8\mu \mbox{m})/\nu L_{\nu} (5\mu \mbox {m})$ are recently discussed with using {\it Spitzer}/Herschel IR spectra of LIRGs as a compact and intense radiation field induces the PAH deficit as mimic of [CII] defcit [m]. Thus, the MIR SED analysis is a unique technique for studying co-evolution of dusty star formation and AGN activities with dusty tori, which should be confirmed with using ALMA soon and be also applied with using MIRI/JWST in future multi- wavelength surveys. We will discuss the hidden connection between dusty starbursts and AGNs reported in Hanami+ (2012) and Krumpe+ (2014) adding resent results obtained with the PACS/Herschel and the CXO.

622014-03-18 Tue
14:20~15:20
physics 104
Phil Marshall
[KIPAC, Stanford University]

Measuring Distance in the Universe with Gravitational Lenses

Understanding the mysterious "Dark Energy" that appears to be driving the expansion of the Universe is one of the biggest challenges facing cosmologists today. While offering no new physical understanding, I will describe a method for at least quantifying the effect of the dark energy that is both new and old: the time delays between the multiple images of gravitationally lensed AGN have long been known to enable a measurement of the Hubble constant, but we have only recently shown how, with careful modeling of enough high quality data, we can achieve comparable accuracy to other, better known cosmographic probes. After introducing and describing this experiment in some detail, I will discuss how we plan to build on it in the next decade, using new lenses discovered using the Large Synoptic Survey Telescopes to find and measure large numbers of suitable systems.

632014-03-12 Wed
14:20~15:20
R1203
Phil Marshall
[KIPAC, Stanford University]

Space Warps: crowd-sourcing the discovery of gravitational lenses

Gravitational lenses are very useful astrophysical tools, providing direct mass measurements of galaxies and clusters, a magnified view of the distant universe, and experimental probes of both dark matter and dark energy. Key to extending the science made possible by gravitational lenses is the discovery of more systems in wide field imaging surveys, but their complex nature makes finding lenses a difficult process to automate. Space Warps is a citizen science project that enables new lenses to be detected by volunteers inspecting images displayed to them via a custom-built website. Over 10,000 volunteers took part in the first Space Warps project, a blind search of the CFHT Legacy Survey imaging. I will present premliminary results from this project, including the first new lens systems to be detected and analyzed by citizen scientists. The second Space Warps project, a smaller targeted search in the VICS82 survey launched in January of this year and was completed in 3 days, thanks to the efforts of nearly 60,000 volunteers inspired by the BBC Stargazing Live TV programmes. I will share results and conclusions from that project too, and speculate on how this approach in general might be extended into the LSST era.

642014-03-05 Wed
14:20~15:20
R1203
Karen Masters
[ICG, University of Portsmouth]

Title: Unwrapping Galaxies with MaNGA.

Mapping Nearby Galaxies at Apache Point Observatory (MaNGA, part of the fourth incarnation of the Sloan Digital Sky Surveys or SDSS-IV), is a new survey which will obtain spatially resolved spectral maps for 10,000 nearby galaxies selected from the SDSS Main Galaxy Sample. These data will unwrap the layers of local galaxies - revealing their stellar and gas dynamics, as well as the ages and chemical make-up of their constituent stars, and locations of current star formation. MaNGA uses the existing SDSS-III BOSS spectrograph, covering the wavelength range 3600--10,000A (with a velocity resolution of ~60 km/s), but grouping the individual 2" fibres into 17 hexagonal bundles of up to 127 fibres each. The bundles range in angular size from 12-33" diameter, with a typical spatial resolution of 1 kpc at the redshift of the MaNGA sample which is selected to provide a uniform sampling of galaxies with stellar masses 10^9 -10^12 Msun. MaNGA is due to start observations on the Sloan Telescope at APO in July 2014 and will observe ~1600 galaxies/year for the six year duration of the survey.

652014-02-27 Thu
14:20~15:20
R1203
Eiichiro Kokubo
[NAOJ]

Formation of Terrestrial Planets: The Basic Dynamical Model

In the standard scenario for solar system formation, planets forms from a protoplanetary disk that consists of gas and dust. The formation scenario can be divided into three stages: (1) formation of planetesimals from dust, (2) formation of protoplanets from planetesimals, and (3) formation of planets from protoplanets. In stage (1), planetesimals form from dust through gravitational instability of a dust layer or coagulation of dust grains. Planetesimals are small building blocks of solid planets. Planetesimals grow by mutual collisions to protoplanets or planetary embryos through runaway and oligarchic growth in stage (2). The final stage (3) depends on a type of planets. For terrestrial planets the final stage is giant impacts among protoplanets while sweeping residual planetesimals. In the present talk, I review the basic elementary processes of terrestrial planet formation, showing N-body simulations and discuss the origin of the diversity of terrestrial planets.

662014-02-26 Wed
14:20~15:20
R1203
Eswaraiah Chakali
[NCU]

Optical and NIR-polarimetry: a key tool to understand dust grain properties and the importance of magnetic fields in star-formation

Incoming light from a number of distant astronomical sources get polarized due to several astrophysical processes. Among them, differential extinction or dichroism, according to which un-polarized light get linearly polarized due to an ensemble of aligned, non-spherical and spinning dust grains with respect to the Galactic magnetic field, is a promising tool to understand the properties of dust grains and to map the line of sight averaged, plane of the sky magnetic field orientation. Polarimetry of reddened background stars of starless and star- forming regions will be useful to map the magnetic field geometry in and around these regions. Magnetic fields are one of the important constituents of the ISM, and are believed to play an important, perhaps even crucial, role in the formation and evolution of the molecular clouds, their collapse, star-formation in them, and the feed back processes (formation and evolution of outflows, mid-infrared bubbles, and bright rimmed clouds). Star-clusters/star-forming regions, and molecular clouds (that are distributed at different distances, reddened by different amount extinction values, characterized by different extinction laws, and having different levels of star- formation activity) were studied using optical and NIR-polarimetry. Field stars and the cluster members have been identified using both optical color-color ((U-B) versus (B-V)) and Stokes plane (Q versus U) diagrams. The distribution and properties of dust grains, distribution of the magnetic field orientation, and the polarization efficiency of the dust grains have been studied. In this colloquium, I will present important results on my past and ongoing research work.

672014-02-25 Tue
14:20~15:20
physics 104
Luis Ho
[KIAA]

Black Holes Big and Small: Impact on Galaxy Formation

Supermassive black holes (BHs) have been found in almost 100 galaxies by dynamical modeling of spatially resolved kinematics. The Hubble Space Telescope revolutionized BH research by advancing the subject from its proof-of-concept phase into quantitative studies of BH demographics. Most influential was the discovery of a tight correlation between BH mass and velocity dispersion of the bulge component of the host galaxy. Together with similar correlations with bulge luminosity and mass, this led to the widespread belief that BHs and bulges coevolve by regulating each other's growth. I present a major update to the status of this field. I will discuss (1) how BH mass correlates tightly only with classical bulges and ellipticals, (2) how the zero point and slopes of the fundamental correlations need to be revised, (3) BH mass estimates in quasars, (4) the discovery of intermediate-mass BHs in dwarf galaxies and implications for quasar seeds, (5) quasar-mode energy feedback at high redshifts, and (6) the evolution (or lack thereof) with time of the BH-host galaxy scaling relations.

682014-02-18 Tue
14:20~15:20
R1203
Misato Fukagawa
[Osaka University]

Protoplanetary disks around intermediate-mass stars at high angular resolution

I present our recent results of imaging of circumstellar disks around Herbig Fe/Ae stars with Subaru and ALMA. Observations of such young disks are critically important to understand how disks evolve possibly under the mutual interaction with new-born planets. One of the observational approaches is direct imaging in scattered light. In our Subaru observations, the technique of polarization differential imaging enabled us to look into the inner region as close as 0.2 arcsec (30 AU) in radius with the typical angular resolution of 0.06 arcsec (8 AU). The imagery has newly uncovered rich structures such as spiral arms, inner holes, and gaps for (pre-)transitional disks while suggested the variably illuminated disks for primordial systems. On the other hand, submillimeter observations are powerful to constrain disk density structure. In our ALMA observations of a Herbig Fe star at 340 GHz, the outer disk was readily resolved in dust continuum and molecular lines of 13CO(3-2) and C18O(3-2), with an angular resolution of about 0.4 arcsec (60 AU). The dust continuum shows strong azimuthal asymmetry and the inferred surface density at the brightness peak suggests gravitational instability if a gas-to-dust mass ratio is 100. Alternatively, a lower gas-to-dust ratio is possible, and in this case, grain accumulation is expected, which may lead to efficient formation of rocky bodies.

692014-02-12 Wed
14:20~15:20
R1107
Chien-Ting Chen
[Dartmouth]

The links between AGNs and the star formation in their host galaxies

The connection between star formation in galaxies and the growth of their super-massive black holes (SMBHs) is an important and still uncertain aspect of galaxy evolution that has seen dramatic progress with the launch of Herschel. I will present our recent studies using Herschel and a range of multiwavelength data in the Boötes field, which have uncovered a global correlation between galactic SFR and the average SMBH growth in far-IR selected star-forming galaxies. These results are consistent with a simple picture that the growths of SMBHs and galaxies are closely linked over galaxy evolution time scale. Using the datasets from the same survey region, I will also present evidence for a link between nuclear obscuration and host galaxy star formation in powerful quasars, which supports a scenario in which obscuration in quasars might be associated with the star-forming dust in the host galaxies.

702014-02-07 Fri
14:20~15:20
R1203
James Lattimer
[Stony Brook University]

Constraining the Nuclear Equation of State with Neutron Stars

There are now about 30 precise neutron star mass measurements. Astronomical observations of X-ray bursts and thermal emissions from neutron stars have recently allowed estimates of their radii. These measurements can be used to constrain the equation of state of the neutron-rich dense matter found in these stars. At the same time, several nuclear experiments, and theories of pure neutron matter, are able to probe the properties of neutron-rich matter. A remarkable concordance of experiment, theory and observations regarding dense matter and neutron stars is emergng.

712014-01-17 Fri
14:20~15:20
R1203
[ETH Zurich]

The LCDM Model: Successes and Future Challenges

The LCDM model has had remarkable successes in explaining a wide array of observational evidence coming from recent cosmology experiments. Though the natures of many of the key ingredients are still largely unknown, the model is built on a small number of parameters (roughly six). In this talk, I will give a quick summary of recent progress. As part of this, I highlight some of the potentials for new discoveries in on-going surveys, with a focus on dark matter, gravitational lensing and the Dark Energy Survey (DES). One of the features of current and future surveys (such as the LSST) is that the large volume of data that these surveys will generate, combined with the stringent requirements that need to be met in order to reach our science goals, pose serious computational challenges. For these missions to be successful, these computational challenges need to be tackled.

722014-01-16 Thu
14:30~15:30
R1203
Yutaka Fujita
[Osaka University]

Stable Heating of Cluster Cool Cores by Cosmic-Rays and Non-thermal Emissions

We show that cosmic-rays (CRs) can stably heat the cool cores of galaxy clusters. The CRs are accelerated by the active galactic nuclei at the cluster centers. They stream in the intracluster medium (ICM) and excite Alfven waves through a streaming instability. The wave energy eventually heats the ICM. We find that this CR heating compensates the strong radiative cooling of the cluster cores. We perform a stability analysis of the heating and indicate that this heating mechanism is much more stable than conventional heating mechanisms such as shocks and sound waves. Moreover, predicted non-thermal emissions from the CRs are consistent with observations of radio mini-halos. I also talk about the next Japanese X-ray satellite Astro-H. Its superb energy resolution will enable us to directly detect turbulence in the ICM.

732014-01-15 Wed
14:20~15:20
R1203
Tohru Nagao
[Ehime Univ.]

Subaru Wide-Field AGN Survey with HSC

Searching for quasars at various redshifts is the most fundamental approach to investigate the cosmological evolution of supermassive black holes (SMBHs). Recent reports suggest a strong evolutionary link between SMBHs and galaxies, telling us that the understandings of SMBHs and their evolution are crucial to reveal the total picture of the formation and evolution of galaxies, not only of quasars. In addition, high-z quasars are quite useful to investigate the evolution of the IGM, by providing the light behind the inter-galactic absorbing materials. These topics have been extensively studied after the data release of the SDSS, that discovered a dozens of z~6 quasars and reported the significant evolution of the neutral fraction of the IGM at high-z. However due to the limited sensitivity and wavelength coverage, the SDSS quasar survey could reach only up to z~6.4 and study only very luminous population of quasars, that prevents us from understanding the whole evolutionary picture of SMBHs and quasars. Recent NIR surveys such as UKIDSS and VIKING is reporting a few z~7 quasars, but the resulting sample size is still insufficient for any statistical analysis. For breaking this problematic situation, we are now promoting a new quasar survey with the new prime-focus camera for the Subaru Telescope, Hyper Suprime Cam (HSC). This quasar survey is a part of the HSC legacy survey, that is an international collaborative project among Taiwan, Japan, and Princeton University. This HSC legacy survey has been already approved, and 300 nights will be dedicated in the coming 5 years. In this colloquium, I would like to review the background, motivation, and the expected outcomes of this HSC quasar survey. Especially I would focus on the potential contribution from the Taiwanese community, which has access to CFHT, SMA, and ALMA. I would also briefly mention on the possible importance of future ALMA Band 1 for follow-up observations of HSC-selected high-z low-luminosity quasars.

742014-01-09 Thu
14:20~15:20
R1203
Kazunori Akiyama
[NAOJ/Univ. of Tokyo]

millimeter VLBI observations of Sgr A* and M87 with VERA and EHT

Despite the universality of accretion and outflow processes in a wide variety of astrophysical systems, much remains unknown about the detailed structure of the innermost regions of the accretion flow and relativistic jet in the vicinity of a supermassive black hole (SMBH). The SMBHs in the center of our Galaxy (Sgr A*) and the nearby active galaxy M87 are excellent laboratories to study these processes because the angular resolution attainable with short-mm VLBI corresponds to a few Schwarzschild radii for these sources (r_Sch = 10 microarcseconds and 7 microarcseconds for Sgr A* and M87, respectively). For Sgr A*, we present the results of 7-mm VLBI observations with VERA, a VLBI instrument in Japan. We report the results of multi-epoch observations of Sgr A* in 2005-2008 as well as preliminary results from monitoring that resumed in January 2013 in order to trace the effects of the G2-cloud infall event. For M87 we show preliminary results of 1.3-mm VLBI observations with the Event Horizon Telescope in March 2012, during the middle of a period of enhancement in Very High Energy (VHE; > 200 GeV) emission. We briefly discuss implications for the structure of the M87 millimeter and VHE emission regions based on these results.

752014-01-08 Wed
14:20~15:20
R1203
Daniel Pfenniger
[University of Geneva]

The dynamics of barred spiral galaxies

Most spiral galaxies are strongly or weakly barred. The dynamics of barred galaxies is radically different from the dynamics of axisymmetric disks, as angular momentum and energy are no longer conserved quantities. Furthermore bar dynamics is fully 3-dimensional, as vertical resonances and chaotic motion play an important role in these systems. Understanding the dynamics of barred galaxies has turned out to be essential for today's Galactic astronomy, for which large-scale surveys, such as GAIA, are ongoing. Indeed the Milky Way has been found to be a spiral galaxy with a peanut-shaped bar, a signature of a strong and old bar. I will review the main characteristics of barred galaxies for an astronomer audience not necessarily familiar with galactic dynamics.

762014-01-02 Thu
14:20~15:20
R1203
Po-Feng Wu
[U. of Hawaii]

Tracing Star-formation Quenching in Cosmic Webs

Galaxy clusters and groups are recognized to play a pivot role on galaxy evolution. Galaxies in dense region of the Universe are believed to have experienced more rapid evolution, but how the environment drives the evolution remains unknown. Post-starburst galaxies, those galaxies just stopped their star-formation activity recently, are ideal tracers of star-formation quenching. They provide the physical condition of galaxies close the time that the quenching happened. Through post-starburst galaxies in large-scale structures, we are able to verify the responsible mechanisms for star-formation quenching, and their relation to environment. I will present results from a supercluster at z~1, approaching the time when the cosmic star formation rate density started to decline rapidly. I will show how the cluster formation affects the evolution of galaxies in the large-scale structure.