Title: M87 Nucleus Observed with the Integral Field Spectrograph Mode of Kyoto3DII

Author(s): A. Nakajima, Y. Ishino, K. Matsubayashi, H. Sugai, A. Kawai, A. Shimono,
Y. Okita, T. Hattori, G. Kosugi

Abstract:
It is well known, through the imaging and long-slit spectroscopy, that in the nucleus
of the nearby elliptical galaxy M87 the ionized gas disk exists. For the detailed
two-dimensional spectroscopic investigation, we have observed the M87 nucleus with
the integral field spectrograph mode of Kyoto Tridimensional Spectrograph II (Kyoto3DII)
mounted on Subaru telescope. Its field of view has covered the M87 nuclear ionized
gas disk and the flaring knot HST-1 in the one-sided continuum jet. The emission-line
velocity fields show the evidence that the ionized gas disk rotates. In addition,
the [OIII] velocity field shows the existence of a blue shifted component in the
M87 nucleus. The [OIII] flux of this component is about 20% of the total [OIII]
flux. It is less prominent in the H_beta emission. The blue shifted component is
considered to be the outflow from the gas disk or the bright component on the disk.
We have obtained for the first time the optical spectrum of flaring knot HST-1.
The spectral index of knot HST-1 estimated from our data is nearly equal to 0.4.
This value is close to that derived from photometric data at the middle of the
flaring. On the other hand, the index from photometric data before the flaring
is approximately 0.7. It is likely that the spectral index became flatter through
the flaring. It is possible that particles with higher energy have increased in
knot HST-1 due to a shock.

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