11 research outputs found
Subaru Observations for the K-band Luminosity Distribution of Galaxies in Clusters near to 3C 324 at z1.2
We investigate the -band luminosity distribution of galaxies in the region
of clusters at near to the radio galaxy 3C 324. The imaging data
were obtained during the commissioning period of the Subaru telescope. There is
a significant excess of the surface number density of the galaxies with
17--20 mag in the region within 40'' from 3C 324. At this bright end,
the measured luminosity distribution shows a drop, which can be represented by
the exponential cut off of the Schechter-function formula; the best-fitted
value of the characteristic magnitude, , is . This
measurement follows the evolutionary trend of the of the rich clusters
observed at an intermediate redshift, which is consistent with passive
evolution models with a formation redshift z_f \gtsim 2. At K \gtsim 20
mag, however, the excess of the galaxy surface density in the region of the
clusters decreases abruptly, which may imply that the luminosity function of
the cluster galaxies has a negative slope at the faint end. This may imply
strong luminosity segregation between the inner and outer parts of the
clusters, or some deficit of faint galaxies in the cluster central region of
the cluster.Comment: 12 pages, 9 figures, accepted for publication in PAS
Superwind-Driven Intense H_2 Emission in NGC 6240
We have performed a long-slit K band spectroscopic observation of the
luminous infrared galaxy NGC 6240. The peak position of the H_2 v=1-0 S(1)
emission in the slit is located ~0.3" - 0.4" north of the southern nucleus. It
is almost the midpoint between the southern nucleus and the peak position of
the ^12CO J=1-0 emission. Based on the line-ratio analyses, we suggest the
excitation mechanism of H_2 is pure thermal at most positions. In the southern
region we find the following three velocity components in the H_2 emission: the
blueshifted shell component (~-250 km s^-1 with respect to V_sys) which is
recognized as a distinct C-shape distortion in the velocity field around the
southern nucleus, the high-velocity blueshifted ``wing'' component (~-1000 km
s^-1 with respect to V_sys), and the component indicating possible line
splitting of ~500 km s^-1. The latter two components are extended to the south
from the southern nucleus. We show that the kinematic properties of these three
components can be reproduced by expanding motion of a shell-like structure
around the southern nucleus. The offset peak position of the H_2 emission can
be understood if we assume that the shell expanding to the north interacts with
the extragalactic molecular gas. At the interface between the shell and the
molecular gas concentration the cloud-crushing mechanism proposed by Cowie et
al. (1981) may work efficiently, and the intense H_2 emission is thus expected
there. All these findings lead us to propose a model that the most H_2 emission
is attributed to the shock excitation driven by the superwind activity of the
southern nucleus.Comment: 33 pages, 9 figures, accepted for publication in PAS
High-Resolution Near-Infrared Imaging of the Powerful Radio Galaxy 3C 324 at z = 1.21 with the Subaru Telescope
We have obtained high-resolution K'-band images of the powerful z=1.206 radio
galaxy 3C 324 with the Subaru telescope under seeing conditions of 0.3--0.4
arcsec. We clearly resolved the galaxy and directly compared it to the optical
images obtained with the Hubble Space Telescope. The host galaxy of 3C 324 is
revealed to be a moderately luminous elliptical galaxy with a smooth light
profile. The effective radius of the galaxy, as determined by profile fitting,
is 1.3+-0.1 arcsec (1.2 kpc), which is significantly smaller than the value of
2.2 arcsec, published in Best et al. (1998, MNRAS, 292, 758). The peak of the
K'-band light coincides with the position of the radio core, which implies that
the powerful AGN lies at the nucleus of the host galaxy. The peak also
coincides with the gap in the optical knotty structures which may be a dust
lane hiding the UV-optical emission of the AGN from our line of sight; it is
very likely that we are seeing the obscuring structure almost edge-on. We
clearly detected the `aligned component' in the K'-band image by subtracting a
model elliptical galaxy from the observed image. The red R_F702W-K color of the
outer region of the galaxy avoiding the aligned component indicates that the
near infrared light of the host galaxy is dominated by an old stellar
population.Comment: 21 pages (10 figures), accepted for publication in PAS
Current Performance and On-Going Improvements of the 8.2 m Subaru Telescope
An overview of the current status of the 8.2 m Subaru Telescope constructed
and operated at Mauna Kea, Hawaii, by the National Astronomical Observatory of
Japan is presented. The basic design concept and the verified performance of
the telescope system are described. Also given are the status of the instrument
package offered to the astronomical community, the status of operation, and
some of the future plans. The status of the telescope reported in a number of
SPIE papers as of the summer of 2002 are incorporated with some updates
included as of 2004 February. However, readers are encouraged to check the most
updated status of the telescope through the home page,
http://subarutelescope.org/index.html, and/or the direct contact with the
observatory staff.Comment: 18 pages (17 pages in published version), 29 figures (GIF format),
This is the version before the galley proo
Performance highlights of the ALMA correlators
Two large correlators have been constructed to combine the signals captured by the ALMA antennas deployed on the Atacama Desert in Chile at an elevation of 5050 meters. The Baseline correlator was fabricated by a NRAO/European team to process up to 64 antennas for 16 GHz bandwidth in two polarizations and another correlator, the Atacama Compact Array (ACA) correlator, was fabricated by a Japanese team to process up to 16 antennas. Both correlators meet the same specifications except for the number of processed antennas. The main architectural differences between these two large machines will be underlined. Selected features of the Baseline and ACA correlators as well as the main technical challenges met by the designers will be briefly discussed. The Baseline correlator is the largest correlator ever built for radio astronomy. Its digital hybrid architecture provides a wide variety of observing modes including the ability to divide each input baseband into 32 frequency-mobile sub-bands for high spectral resolution and to be operated as a conventional 'lag' correlator for high time resolution. The various observing modes offered by the ALMA correlators to the science community for 'Early Science' are presented, as well as future observing modes. Coherently phasing the array to provide VLBI maps of extremely compact sources is another feature of the ALMA correlators. Finally, the status and availability of these large machines will be presented