Motomi Ishii

Kyoto tridimensional spectrograph II: progress

We are building the Kyoto tridimensional spectrograph II and are planning to mount it on Subaru telescope. The spectrograph has four observational modes: Fabry-Perot imager, integral field spectrograph (IFS) with a microlens array, long-slit spectrograph, and filter-imaging modes. The optics is designed to be used in wide wavelength range from 360 nm to 900 nm. The design well matches with high spatial resolution of Subaru: 0 inch .06 pixel-1 in Fabry- Perot mode, for which we actually will use binning before adaptive optics at optical wavelengths becomes available, and 0 inch .1 lens-1 in microlens array mode. These well sample image sizes obtained by Subaru, which are about 0 inch .4 in relatively good conditions. We have evaluated a point spread function of our cylindrical microlens array and found that it consists of a diffraction pattern and more extended component which probably comes from border regions between microlenses. With a suitable mask at the micro pupil position, the crosstalk between spectra will be limited down to a few percent. With a suitable mask at the micro pupil position, the crosstalk between spectra will be limited down to a few percent. We have succeeded in synchronizing frequency switching of Fabry-Perot etalons with the movement of charge on the CCD. This technique enables to average out all temporal variations between each passband.

SUBARCSECOND STRUCTURE AND VELOCITY FIELD OF OPTICAL LINE-EMITTING GAS IN NGC 1052

We have obtained integral field spectra of the low-ionization emission-line region in the galaxy NGC 1052 by using the Kyoto Tridimensional Spectrograph II mounted on the Subaru Telescope. Our high signal-to-noise ratio data with precise template subtraction have revealed weaker features at the nucleus, including the [Fe III] and He II emission lines, as well as a broad component of the Hβ emission. The broad Hβ component suggests the existence of a broad-line region. The spatial structure and velocity field derived from the data cube suggest the existence of three main components: a high-velocity bipolar outflow, low-velocity disk rotation, and a spatially unresolved nuclear component. The outflow axis does not coincide with the disk rotation axis. The opening angle of the outflow decreases with velocity shift from the systemic velocity both in bluer and redder velocity channels. This is explained only if the outflow has intrinsically higher velocity components inside, i.e., in regions closer to the outflow axis. At both sides of the bipolar outflow, we find that the highest velocity components are detached from the nucleus. This gap can be explained by an acceleration of at least a part of the flow or the surrounding matter, or by bow shocks that may be produced by even higher velocity outflow components that are not yet detected. Along the edges of the outflow and extending east-northeast and west-southwest, there exist strong [O III] emission ridges. These are closely related to the radio jet-counterjet structure. The abrupt change in the velocity field of the ionized gas and a large [O ]/Hβ line flux ratio in this region suggest a strong interaction of the jets, and possibly also of some ridge components of the line-emitting gas, with the interstellar matter.

Rapid large-scale metal enrichment in the starbursts of an interacting Galaxy system

By obtaining integral field spectra of the interacting galaxy system NGC 6090, we have found a kiloparsec-scale region where active star formation is currently increasing the fraction of heavy elements. Young massive starbursts are occurring in regions offset from the galactic centers, highlighting the present epoch of metal enrichment over the previous ones usually seen at galactic centers. The short timescale of ~107 yr for the starbursts, inferred from the galactic rotation, provides a strong constraint on the origins of the metallicity/abundance enhancements. While oxygen is considered to originate in supernovae, the observed nitrogen enhancement is likely to be caused by winds/mass loss from massive stars rather than being a product of intermediate-mass stars.