Subaru Seminars

JELT is a 30m optical/infrared telescope under phase-A study. On Dec.1, NAOJ decided to setup JELT Project Office. The outline of the concept and some R&Ds undertaken, e.g. optical design, zero-expansion ceramic mirror, high-precision grinding of mirror, expected performance etc. will be shown.

We have made mid-infrared and H2 emission surveys of Orion proplyds in order to study behavior of gaseous and solid components within their circumstellar disks using COMICS and IRCS on Subaru. We found an clear anti correlation between the MIR flux density and the H2 emission, i.e. proplyds strong in H2 mission had weak MIR emission. This anti correlation is naturally understood as an evolutional sequence of evaporation for proplyds in which gaseous and solid components are separated along the z direction within the circumstellar disk. We argue that the separation is likely to be caused by settlement of dust grains onto the disk equator.

Nearby young clusters have distinct advantages for the study of star formation and stellar evolution issues. These issues include the origin of the initial mass function (IMF), binarity, the evolution of proto-planetary discs and the fundamental properties of pre-main sequence (PMS) stars. Such clusters provide for study a population　of stars across a wide range of stellar masses at essentially uniform age, distance and metallicity, that are sufficiently bright owing to their youth and proximity for a multitude of precise astrophysical studies that would be difficult for older and/or more-distant cluster　populations. In addition, young clusters usefully contribute to　the study of cluster formation because their current physical state might a consequence of earlier, and possibly on-going, dynamical or evaporative processes. The nearby (d~97pc) young (t = 9 +- 1 Myr) Eta Chamaeleontis cluster is a good laboratory for these issues.

It is a remarkable feature that properties of galaxies (color, morphology, and luminosity) vary according to their environments. However, little has been known on the physical origin of this variety in galaxies. We take two approaches to tackle this problem:(i)detailed investigation on the galaxy environment using the unprecedentedly large sample of nearby galaxies from the Sloan Digital Sky Survey (SDSS)(ii) revealing the evolution of the morphology-density relation since z=1 using the Hubble Space Telescope Advanced Camera for Surveys (HST/ACS) high-z cluster survey. Using the SDSS data, we investigate the morphology-density relation to find two characteristic environment where the morphology-density relation abruptly changes (at 0.3 and 2 Rvir). The result has significant implication for the underlying physical mechanism since it suggests that two different mechanisms might be responsible for the morphology-density relation. In addition, we study the environment of unusual spiral galaxies with no [OII] or Halpha emission lines (passive spirals), and find that passive spiral galaxies preferentially live in cluster infalling regions (at 1-10 Rvir) Thus, a cluster related physical mechanism is likely to be responsible for the creation of the passive spiral galaxies. We extend these studies in the local universe to z=1 using the data from the HST/ACS high-z cluster survey. The observed evolution of the morphology-density relation between z=0 and 1 suggests that cluster specific physical process is needed to explain the evolution, i.e., we found the evidence for "nurture" scenario although this does not exclude "nature" scenario.

In the latter half of the talk, we move focus to the E+A (post-starburst) galaxies, which have been historically believed to be the transition objects in the cluster galaxy evolution due to their post-starburst nature (strong Balmer absorption lines and the lack of emission lines). In the literature, there have been three possible explanations for E+A galaxies; (i) cluster-related physics (e.g., ram-pressure stripping)(ii) galaxy-galaxy merger/interaction (iii) dusty-starbursts. By constructing the largest samples of 266 E+A galaxies from the SDSS, we observationally test these three scenarios to reveal the physical origin of E+A galaxies.

I will discuss several new techniques for asteroseismological analysis as applied to the three classes of pulsating white dwarf stars.

Astronomical polarimetry is a powerful technique that can potentially provide physical information sometimes difficult or impossible to obtain by any other type of observation. Almost every type of binary star can benefit from polarimetric observations: pre-main-sequence objects, close or contact binaries, mass-transfer systems, cataclysmic variables, eclipsing binaries, etc. In these systems, polarimetry can help determine the geometry of the circumstellar or circumbinary matter distribution, yield information on asymmetries and anisotropies in these systems, detect magnetic fields, map starspots, establish orbital parameters or stars' sizes. The orbital inclination is a very important piece of information for a binary system because it can lead to the determination of the components' masses, a fundamental parameter that determines a star's structure and evolution. This presentation will illustrate the usefulness of polarimetric techniques for the study of binary stars.

Professor Tetsuo Nishimura just retired from NAOJ at the end of March, 2004, and we have a special lecture honoring his distinguished service to the Subaru Project.

After working at University of Arizona, Prof. Nishimura joined the National Astronomical Observatory of Japan, Subaru Telescope Project on April 1, 1993. He moved to Hilo on April 1, 1997 (on the day we started our Hilo office). Since then, he worked as an Associate Director of the Subaru Telescope. He was responsible for the instrumentation division as well as the most of the Subaru's external affairs and local community relationships. During his time with Subaru Telescope, he successfully constructed and commissioned one of the Suaru's first-light instrument, MIRTOS. Also, he is about to complete one of the 2-nd generation instrument, MOIRCS.

We would like to express our thanks to Prof. Nishimura for his contribution to the Subaru project by asking him to talk about his experience with Subaru Telescope and astronomical instrumentation. After his talk, we will hold a reception where we could meet and chat with him. For those of you who are interested in participating in the reception, please make a contribution as follows.

RSVP is requested by Tuesday, April 13, 2004, please send to Kaz Sekiguchi (kaz@subaru.naoj.org).

While the evolutionary status of low-mass young stars is distinguished by the spectral energy distributions, such classification scheme has not been established for intermediate-mass young stellar objects. Near-infrared spectroscopy can be a powerful tool to study details about the YSO photospheres and the circumstellar environments, which cannot be probed by the SED alone. To examine the NIR spectral lines of the intermediate-mass YSOs, we observed the K band spectra of Herbig Ae/Be stars and Class I YSOs which are considered to be the precursors of Herbig Ae/Be stars. I'll present the results with a focus on the relation between the spectral lines and the SEDs, spectral types, ages. I'll also report preliminary results of the H band spectroscopy of Class I YSOs.

We have a Preliminary Design Review meeting of the Subaru Laser Guide Star Adaptive Optics system on Dec. 2 and 3 at the Hilo office of Subaru Telescope. The system is an upgrade of the existing 36 element curvature sensor based AO system. The system will be equipped at the Nasmyth focus with a 188 element curvature sensor, and a bimorph deformable mirror. We plan to have the first light as a natural guide star system in 2005 and the laser first light in 2006.

Suprime33 is weak lensing survey which exploits the unique capability of Suprime-Cam. Its primary purpose is to construct, for the first time, a mass selected cluster catalog containing more than 200 massive, intermediate to high-z clusters. I will present the following topics: (1) a brief review of clusters of galaxies and their role in cosmology. (2) an ability of weak lensing cluster surveys and properties of clusters detected in weak lensing surveys. I will show that weak lensing survey with Suprime-Cam provides an efficient way to search for clusters of galaxiess. The expected number counts of weak lensing clusters is 7 per 1sq deg for a high significant detection signal of S/N>4, which is comparable to a deep X-ray selected cluster counts of 5 per 1sq deg for fx>2e-14erg/cm^2/s. More importantly, weak lensing survey has the potential to detect massive but X-ray faint clusters, which X-ray surveys have missed. (3) results from a pilot survey in GTO 2sq deg field. (4) the outline of Suprime33, its current status and preliminary results from 2003 run.

The Subaru/XMM-Newton Deep Survey (SXDS) is a new deep Optical/X-ray survey which aim to take full advantage of the capabilities of the Subaru Telescope and the XMM-Newton. The SXDS is part of an ambitius project to obtain extensive multi-wavelength data across a $\sim1.3$\,deg$^2$ region of sky. Other wavelength data (infrared, mid-infrared, submillimeter, and radio) are being pursued through various facilities. Combined with suitably deep images at other wavelengths the SXDS would provide an accurate census of the contents of the Universe without suffering from the biasing effects of large-scale structures. This presentation describes the location, size and depth of this survey, as well as the current status of the multiwavelength coverage of the survey field.

New Horizons is a funded NASA mission to make the first reconnaissance of bodies in the Kuiper Belt. New Horizons is being built to launch in January 2006. It willl use a Jupiter gravity assist flyby to reach the Pluto-Charon system in July 2015; following this New Horizons will go on to make one or more flybys of Kuiper Belt Objects. We will describe the science and scientific payload that this mission carries, and then go on to describe the search for suitable Kuiper Belt Object candidates that we are planning.

Subaru Deep Field (SDF) is one of the blank fields where Subaru Telescope is conducting wide and deep blank-field survey projects. We study the evolution of B-band color-separated luminosity functions (LFs) of field galaxies up to z~1 in the SDF (~550arcmin^2), based on a photometric redshift technique using multi-band data (B,V,R,i,z bands; i=25.3) taken with the Subaru Prime Focus Camera (Suprime-Cam). The LFs obtained from the SDF data reveal very wide magnitude range from the bright end to the faint end. It is found that the blue population shows significant brightening against redshift while the red population indicates a strong decreases in the number density, which roughly supports the implication given in previous surveys. Remarkably, the LFs of both blue and red populations have very steep slopes at the faint ends, suggesting the existence of quite a number of field dwarf galaxies (MB>-17). We discuss properties of these dwarf galaxies found based on photo-z and future prospects as well.

The circumstellar environment within 10 AU of young stars is of particular interest for studies of star and planet formation. In this region, the star accretes the material from the circumstellar disk, and drives an energetic jet/wind. In the circumstellar disk, planets may be growing and tidally interacting with the circumstellar environment. In a significant number of objects, this region also contains a stellar companion. The population, mass distribution, and orbital parameters of these companions could give useful constraints on the understanding of binary formation. However, even the Hubble Space Telescope or adaptive optics on 10-m telescopes cannot resolve this scale in the nearest star-forming regions. To obtain spatial information at such high resolutions, we use the technique of ''spectro-astrometry''. By use of a standard long-slit spectrograph, the seeing position relative to the continuum is measured in emission/absorption features with an extremely high accuracy (~1 mas). We have proved that this method is capable of discovering pre-main sequence binaries, determining kinematics of outflows and providing evidence for gaps in circumstellar disks --- all down to AU scales. I summarise our progress to date, and present some recent results obtained at the SUBARU 8.2-m telescope.

The 'OHANA(Optical Hawaiian Array for Nanoradian Astronomy, means 'familiy' in Hawaiian) project consists in linking the large telescopes of the Mauna Kea summit with single-mode fiber optics to realize a large near-infrared interferometer. The project started in 2000 and now it is under development. I will review the main characteristics of 'OHANA. The status of development will also be discribed.

I will be presenting a combination of results from HST and UKIRT on the centers of spiral galaxies and giant elliptical galaxies. The HST data have revealed that bulges in early type spiral galaxies have similar properties to those of ellipttical galaxies, suggesting a common formation mechanism. However, bulges in late type spiral galaxies seem to have characteristics more common with their disks. I will also present some near-infrared imaging data of giant elliptical galaxies. These have revealed multiple nuclei structure never seen before, dur to the excellent seeing conditions in which they were taken. Their nuclear structure also suggests that they form via major mergers of large cluster galaxies.

Nearby elliptical galaxies are known to have radial gradients of color and metal absorption line strength; colors gradually become redder and metal absorption lines become stronger towards the center, suggesting that stellar population in an elliptical galaxy changes with radius. Such a spatial variation of stellar population is likely to reflect how the galaxy assembled. On the other hand, formation history of elliptical galaxy is likely to depend on its environment. Therefore, it is important to study the observational properties in various environments and compare one population with another. Radial gradients of color and metal absorption line strength gradient have been investigated so far in several tens of nearby elliptical galaxies. One of the shortcomings of these studies, however, is that almost all the galaxies reside not in rich clusters but in relatively sparse environments. Recently, we performed B and R band surface photometry for E/S0 galaxies in rich clusters (ABELL 2199 and Coma). Based on the results from our data and those from the literature, I will discuss formation process of elliptical galaxy and its environmental dependence.

Earth's atmosphere and ocean climmate shows variation in 10 to a few scores of years time scale. There is a transition in mid-70s in this system, and it is addressed as "Regime Shift". The correlation between this and the global climate change is now one of the hottest topic in the meteorology. The central area of the northern Pacific Ocean creates "Central Mode Water" that might contribute to the large scale weather change. The most recent Regime Shift occurred around 1998-99 and the expedition this time between Hilo and Honolulu is to study the Central Mode Water and any characteristics change in this area.