Colloquium (2003)

A brief overview on past, present status ofastronomical research in R.O.U. and future plans will be presented. Uzbekistan has the ancient, milennial traditions in science, particularly in astronomy. Acting Ulugh Beg Astronomical Institute (UBAI) was founded in 1873. Now UBAI contains Mt.Maidanak observatory with excellent astroclimate and seeing in subarcsecond level, which makes the place as one of the best sites worldwide. Even a suit of small telescopes (1.5 m,1.0 m, etc.) might be effective enough in such sky conditions and geographic or longitudinal position. Since 2001 Uzbek-Taiwan collaboration is active subjecting on study of young stars, SF regions and open clusters(OC). We have studied young star cluster NGC 6823 with surrounding HII nebula NGC6820 and discovered a sample of TTS and HAeBe stars. We also have carried out the monitoring/patrolling of selected PMS stars and OC to explore their variability properties. The BVI photometetric observations of 47 OC have been already made to construct the CMD and determine their ages, distances as well as other parameters. The most important direction of our joint efforts is to automate Maidanak 1 m Carl Zeiss telescope. Nowadays the collaboration grows into the UBAI-NCU-ITPA/VU (Lithuania)-LU(Latvia)-YunnanObs scientific consortium, which includes the Tai-Bal open cluster project too and welcomes new partners. Another prominent astronomical project in R.O.U. is International Radio-astronomical Observatory on plateau Suffa with abuilding 70 m adaptive radiotelescope for cm-submm range. Hopefully creating IRAOS and establishing international O/IR observatory on Mt.Maidanak will constitute an unique astronomical ensemble in the near future.

We present here the first calculation that describes the self-similar collapse of a relativistic singular isothermal sphere, which leads to the formation and growth of a black hole. Like its Newtonian counterpart, the collapse proceeds in an inside-out fashion. The collapse front takes the form of an expansion wave that propagates out at the speed of sound. Once the fluid enters the expansion wave, it is accelerated from rest to speed of light as it crosses the event horizon without ever passing through a mathematical critical point. I will then speculate the possibility of black holes possessing magnetic field structure of a split monopole. If this possibility can be realized, the no hair theorem of black holes will need to be augmented.

Astronomy and information technology (IT) share certain common attributes: heavy reliance on the use of computer technology; application of information and knowledge integrated from many disciplines; and easy captivation of the attention of the general public. Developments in astronomical research and applications of IT are also closely related. In the past decade, rapid advances in IT and easy access to the Internet are changing the way people around the world work, play, learn and do business. In higher education, the unique characteristics of the World Wide Web as a communication medium (e.g., use of hypermedia, connectivity, interactivity and flexibility) are causing a paradigm shift toward Web-centric teaching and learning, leading to new educational structures that require new institutional processes, new support services, as well as new skills and pedagogy. By drawing parallels between concepts and skills in astronomical research and those in management and IT development (e.g., from stellar classification to personality types in enneagram; from multi-wavelength observations to multimedia communications; from order-of-magnitude estimates to decision-making; from serendipity to human networking; from solving scientific problems to resolving people conflicts, etc), I will demonstrate how the professional training in astronomy can indirectly prepare one for a career change, from research/teaching in astronomy to implementing IT infrastructure in higher education. As an example, I will briefly describe how I led the implementation of a comprehensive 3-year plan to develop an IT infrastructure at the Open University of Hong Kong to meet the needs for learning in a networked multimedia environment with online support services.

HCN (1-0) contains 3 hyper-fine transitions with different optical depths and they can be used to probe different regions of the cores. The inward motions can be implied by the presence of the spectral "infall asymmetry" in each of those transitions. The velocity structures of the inward motions can be investigated by using all three hyper-fine transitions. In order to study the infall motions in starless cores, we have made a systematic survey toward the central regions of 86 sources with HCN (1-0) lines using TRAO 14-m radio telescope. Among 86 sources, 52 were detected. Thirty sources show typical infall asymmetry in at least one of the three hyperfine components. Degree of infall asymmetry and infall incidence in HCN are found to be usually more pronounced than those in CS(2-1) by Lee et al.

The Atacama Submillimeter Telescope Experiment (ASTE) is the Japanese project of a 10-meter submillimeter antenna in the Atacama desert of northern Chile. It was built in March, 2002 in Pampa la Bola, at 4840m altitude. The location is very close to Chajnantor area, known as the ALMA site. The project is managed by National Astronomical Observatory of Japan (NAOJ) in collaboration with Japanese universities and Universidad de Chile. The high precision submillimeter antenna and high performance submillimeter receivers are built, then installed for developments of engineering and observational techniques in the submillimeter wavelengths. The telescope is operated on-site and from the nearest village of San Pedro de Atacama (2850m) currently and, from Universidad de Chile and from NAOJ in Japan in the near future. We here, report on the current status of the project and the development of the 3 colours bolometer. The effective observable wavelengths of the bolometer are in the atmospheric windows of 850, 450 and 350 micron bands (350, 650 and 850 GHz). The continuum onservations in the high frequency bands (submillimeter wavelength) allows us to observe thermal emissions from cold objects and dusts such as TNOs and debris disks. We discuss on the observation plans to derive the size and effective temperature of TNOs, and to estimate of dust mass in extra Kuiper disks using ASTE and ALMA in the future. This study aims to obtain the size distribution of TNOs for our solar system, and the fraction of existence of debris disks for solar analogue stars, and the disk kinematics, disk mass, gas-to-dust ratio of the disk and mass of the central star for the near-by young star region. Such physical quantities allow us to verify the standard theory of planetary system formation.

A superconducting tunnel junction (STJ) is a candedate detector of next generation astronomy. A STJ detector can observe single photon with energy resolution at energy range of optical to X-ray with high quantum efficiency. Comparing to conventional devices, such as semiconductors and gas propotonal counters, the expected energy resolving power is more than 30 times higher and the spectral coverage is 1000 times wide. The objective of my study is to realize real-time multi-color imaging in optical wavelengths with STJ detector. STJ detectors have some advantages like (1) free from photon loss caused by filter (2) free from backgournd cosmic-ray (3) no dead time of filter exchange. The advantages result high efficency and fast sampling rate, so that a STJ detector is suitable for fast varing objects or dark objects, such as asteroids, Keuper belt objects, near earth asteroid, gamma-ray bursts, supernova and accretion disk systems. The STJ device is not in commerical use, so the fabrication of STJ devices are studied. In this talk, I will introduce about an environment of my research, and the development of fabrication and current status are reviewd.

The recently discovered Eta Chamaeleontis cluster has the potential of clarifying some of the observational issues. It is a nearby (~ 97pc), compact (extent ~1pc) and coeval (t = 9 +- 1 Myr) system of Pre-main sequence stars with a small (17 known primaries) population of stars spanning a relatively large range in mass (M = 0.15 - 3.40 Solar mass). The cluster includes Eta Cha (spectral type B8), HD 75505 (A5), the A7+A8 binary and delta Scuti system RS Cha, 13 Weak-lined T Tauri stars (K5-M5.5) and 1 Classical T Tauri star (M3). Importantly, this census is known to be virtually complete in the inner region from a combination of a deep ROSAT exposure, optical photometry and proper motion study of the field. Unlike most other PMS populations, these membership criteria are independent of the presence or absence of circumstellar disks. We can thus use the Eta Cha population as an unbiased laboratory to investigate the fraction of IR excess and accretion at a critical intermediate-age phase of disk evolution. And also this cluster provides an excellent laboratory for study of the properties, like population and dynamical state of ~ 10 Myr-old intermediate-aged PMS stars because of their proximity to the Sun, compactness in the sky, and distance from obscuring clouds.

M82 is one of the nearest starburst galaxies, and therefore well suited for a case study about starburst. We present high spatial resolution (2.3" x 1.9" or 36pc x 30pc) 100GHz continuum emission observations with the Nobeyama Millimeter Array toward an expanding molecular superbubble in the central region of M82. The 100GHz continuum image, which is dominated by free-free emission, revealed that the strongest peaks are concentrated at the inner edge of the superbubble along the galactic disk. The production rates of Lyman continuum photons calculated from the 100GHz continuum flux are an order of magnitude higher than those from the most massive star forming regions in our Galaxy. Based on our data and previously published data, self-propagating starburst around this region is also discussed.

Molecular gas in the Andromeda Galaxy -- distribution, kinematics and properties of the molecular gas Both IRAM 30m and Plateau de Bure Interferometer have been used to study the CO(1-0) line emission of the molecular gas in the Andromeda galaxy (M31). The disk of the galaxy reveals thin molecular spiral arms decomposed in complexes and clouds. The kinematics of the molecular gas show interesting double peaked profiles, which are not due to a warp. I will finally present somephysical properties of the molecular clouds, especially their masses, as derived through dynamical considerations (virial theorem).

Sub-pc-scale Plasma Tori in Active Galactic Nuclei Seiji Kameno (NAOJ) Active galactic nuclei (AGNs) are the most powerful objects in the universe. Their energy source is considered to be accreting matter onto a supermassive black hole. While presence of the black hole was revealed by observations, accreting processes are less understood. Here I report about accreting matter in sub-pc-scale vicinity of AGNs, by using VLBI facilities such as the VSOP (VLBI Space Observatory Programme) and the VLBA (Very-Long-Baseline Array). We observed 18 GHz-Peaked Spectrum (GPS) radio sources, whose radio spectrum shows a cutoff below GHz frequencies, and found that free-free absorption (FFA) causes the cutoff. FFA is a thermal process in which background radio emission like synchrotron radiation from jets is attenuated through cold (~10^5 K) and dense (~10^4 cm^-3) plasma. One of our samples, NGC 1052, showed a plasma disk- or torus-like plasma distribution of ~1 pc in radius. This indicates that accreting matter is ionized by irradiation of the nucleus. We will mention comparison with water maser observations to discuss how to probe accretion processes.

NTU Physics Dept. / NTU CCMS / ASIAA Joint Colloquium

Determination of the Distance to S Per Yoshiharu Asaki (ISAS) S Per (Perseus) is an evolved star surrounded by an expanding shell, which is well observed in water maser emission. We have conducted a VLBI phase-referencing position measurement of S Per at three epochs with respect to the reference source KR143, which is 0.22 deg from S Per and has a flux density of only a few tens of milli-Jy at 1 cm. KR143 was successfully detected, and about 50 maser spots among more than 100 detected are identified in all epochs. Using a model of the annual parallax, proper motion of the central star, and simple expanding shells, we estimated the annual parallax of 0.396 0.040 mas. This leads to a distance to S Per of 2.55 0.26 kpc, which is the most accurate astrometric measurement of S Per. The median values of the proper motions in right ascension and declination are -0.51 and -1.59 mas/yr, respectively. This motion is consistent with the Hipparcos result within its accuracy of 2 mas/yr. Our VLBI observations allow us to investigate properties of the circumstellar envelope of the evolved star, as well as the distance, to study the period-luminosity relation of semi-regular super red giants.

Three-Millimeter Results from the Australia Telescope Tony Wong (CSIRO, ATNF) I review some of the current and future capabilities of the 3mm system on the Australia Telescope Compact Array (ATCA). I then present some recent results on dust disks around T Tauri stars, molecular gas around a carbon star, and a dense clump in an LMC molecular cloud.

CosPA / ASIAA Joint Seminar

NGC 4258 and Horizon Makato Miyoshi (National Astronomical Observatory of Japan) This talk has two parts. First, I will talk about the water mega maser in NGC 4258: from the detection of high velocity components around 1000 km/s with Nobeyama 45 m telescope to the 1995 VLBA observations and some follow-ups. Second, I will discuss the future prospect for investigating black holes with VLBI observations.

Informal Discussion

NTU Physics Dept. / ASIAA Joint Colloquium

The Synthesis of Inorganic and Organic Compounds in the Late Stages of Stellar Evolution Sun Kwok (University of Calgary) Recent observations by the Infrared Space Observatory (ISO) have found evidence of rapid synthesis of complex organic molecules in the late stages of stellar evolution. The chemical synthesis begins with the formation of acetylene, the first building block of benzene, in carbon stars. In a following proto-planetary nebulae stage, emission features corresponding to stretching and bending modes of aliphatic compounds are detected. When these objects evolve to become planetary nebulae, aromatic C-H and C-C stretching and bending modes become strong. These results show that complex carbonaceous compounds can be produced in a circumstellar environment over a period of only a few thousand years. In this talk, we will summarize the history of astronomical infrared spectroscopy in the last 30 years, discuss the formation of solid-state inorganic and organic compounds in stars, and speculate on the possible implications of these products on the formation of the solar system.