72 research outputs found
The Central Gas Systems of Early-Type Galaxies Traced by Dust Feature: Based on the HST WFPC2 Archival Images
We investigated the central gas systems of E/S0 galaxies by making use of the
WFPC2 images of the Hubble Space Telescope archive. We searched the gas systems
that were traced by the dust with a new method of making color excess images in
F555W - F814W (V-I). Out of 25 sample galaxies, we detected gas system in 14
galaxies. The dust was newly detected in two galaxies that were thought to
contain no dust based on single band, pre-refurbishment data. The full extents
of the gas systems are 0.1 to 3.5 kpc, and the masses of the gas, log M(gas)
[M(solar)], are 4.2 to 7.2. The AGN activity is well correlated with existence
of the gas systems. None of galaxies without the gas systems show the AGN
activity. On the other hand, some galaxies with the gas systems show the AGN
activity; optical AGN activities are shown in 5 out of 11 galaxies of which
AGNs are optically studied, and radio activities are shown in 6 out of 14
galaxies. This shows that the AGN activity is driven with the gas system.Comment: gzipped tarred file containing 7 files: Tomita.tex (main text, needs
aaspp4.sty), Tomita.tab[1,2].tex (tables, need aj_pt4.sty), Tomita.fig
[1a,1b,1c,2].ps (PS figures). To be appeared in AJ, Vol.120, No.1 (July 2000
Early Science Result from the Japanese Virtual Observatory: AGN and Galaxy Clustering at z = 0.3 to 3.0
We present the result of projected cross correlation analysis of AGNs and
galaxies at redshifts from 0.3 to 3.0. The Japanese Virtual Observatory (JVO)
was used to obtain the Subaru Suprime-Cam images and UKIDSS catalog data around
AGNs. We investigated 1,809 AGNs, which is about ten times larger a sample than
that used in previous studies on AGN-galaxy clustering at redshifts larger than
0.6. 90% of the AGN samples are optically-selected AGN from the SDSS and 2dF
catalogs. The galaxy samples at low redshift includes many redder objects from
UKIDSS survey, while at higher redshift they are mainly blue galaxies from
Suprime-Cam. We found significant excess of galaxies around the AGNs at
redshifts from 0.3 to 1.8. For the low redshift samples (), we obtained
correlation length of 5--6 Mpc (), which
indicates that the AGNs at this redshift range reside in a similar environment
around typical local galaxies. We also found that AGNs at higher redshift
ranges reside in a denser environment than lower redshift AGNs; For AGNs, the cross correlation length was measured as 11
Mpc (). Considering that our galaxies sample is based on
optical observations with Suprime-Cam at the redshift range, it is expected
that blue star-forming galaxies comprise the majority of objects that are
observed to be clustered around the AGNs. It is successfully demonstrated that
the use of the archive through the Virtual Observatory system can provide a
powerful tool for investigating the small scale environment of the intermediate
redshift AGNs.Comment: accepted to PASJ, 36 pages, 21 figures, this is an accepted versio
Superwind-driven Intense H Emission in NGC 6240 II: Detailed Comparison of Kinematical and Morphological Structures of the Warm and Cold Molecular Gas
We report on our new analysis of the spatial and kinematical distribution of
warm and cold molecular gas in NGC 6240, which was undertaken to explore the
origin of its unusually luminous H emission. By comparing three-dimensional
emission-line data (in space and velocity) of CO (J=2-1) in the radio and H
in the near infrared, we are able to study the H emitting efficiency,
defined in terms of the intensity ratio of H to CO [(H)/(CO)], as
a function of velocity. The integrated H emitting efficiency is calculated
by integrating the velocity profile of H emitting efficiency in blue, red,
and total (blue + red) velocity regions of the profile. We find that (1) both
the total H emitting efficiency and the blue-to-red ratio of the efficiency
are larger in regions surrounding the CO and H intensity peaks, and (2) the
H emitting efficiency and the kinematical conditions in the warm molecular
gas are closely related to each other. A collision between the molecular gas
concentration and the external superwind outflow from the southern nucleus
seems plausible to explain these characteristics, since it can reproduce the
enhanced emitting efficiency of blueshifted H around the molecular gas
concentration, if we assume that the superwind blows from the southern nucleus
toward us, hitting the entire gas concentration from behind. In this model,
internal cloud-cloud collisions within the molecular gas concentration are
enhanced by the interaction with the superwind outflow, and efficient and
intense shock-excited H emission is expected as a result of the
cloud-crushing mechanism.Comment: 12 pages, 6 figures, accepted for publication in A
Nature of a Strongly-Lensed Submillimeter Galaxy SMM J14011+0252
We have carried out near-infrared JHK spectroscopy of a gravitationally
lensed submillimeter galaxy SMM J14011+0252 at z=2.565, using OHS and CISCO on
the Subaru telescope. This object consists of two optical components, J1 and
J2, which are lensed by the cluster Abell 1835. J1 suffers additional strong
lensing by a foreground galaxy at z=0.25 in the cluster. The rest-optical
H-alpha, H-beta, and [O II]3727 lines are detected in both J1 and J2, and [N
II]6548,6583 lines are also detected in J1. A diagnosis of emission-line ratios
shows that the excitation source of J1 is stellar origin, consistent with
previous X-ray observations. The continua of J1 and J2 show breaks at rest
4000A, indicating relatively young age. Combined with optical photometry, we
have carried out model spectrum fitting of J2 and find that it is a very young
(~50 Myr) galaxy of rather small mass (~10e8 M_sol) which suffers some amount
of dust extinction. A new gravitational lensing model is constructed to assess
both magnification factor and contamination from the lensing galaxy of the
component J1, using HST-F702W image. We have found that J1 suffers strong
lensing with magnification of ~30, and its stellar mass is estimated to be <
10e9 M_sol. These results suggest that SMM J14011+0252 is a major merger system
at high redshift that undergoes intense star formation, but not a formation
site of a giant elliptical. Still having plenty of gas, it will transform most
of the gas into stars and will evolve into a galaxy of < 10e10 M_sol.
Therefore, this system is possibly an ancestor of a less massive galaxy such as
a mid-sized elliptical or a spiral at the present.Comment: 21 pages, 11 figures. Accepted for publication in Astronomical
Journa
Infrared Imaging of z=2.43 Radio Galaxy B3 0731+438 with the Subaru Telescope - Detection of H Ionization Cones of a Powerful Radio Galaxy
We report on infrared imaging observations of the z=2.429 radio galaxy B3
0731+438 with the Subaru telescope. The images were taken with the K'-band
filter and the 2.25 um narrow-band filter to examine the structure and
properties of the Ha+[N II] 6548,6583 emission-line components. The Ha+[N II]
emission-line image shows biconical lobes with an extent of 40 kpc, which are
aligned with the radio axis. The rest-frame equivalent widths of the emission
lines at these cones are as large as 1100 AA, and can be well explained by a
gas-cloud model photoionized by power-law continuum radiation. The isotropic
ionizing photon luminosity necessary to ionize the hydrogen gas in these cones
amounts to 1e57(photons/s), which is larger than that in the majority of
radio-loud QSOs. From these results, we propose that the Ha alignment effect in
this object is produced by biconical gas clouds, which are swept up by the
passage of radio jets, and are ionized by strong UV radiation from a hidden
AGN. The continuum image consists of two components, a stellar-like point
source and an extended diffuse galaxy. These are supposed to be a type-2 AGN
and its host galaxy. The SED is fitted by a combination of spectra of a
reddened dust-scattered AGN and an instantaneous starburst population of 500
Myr old. The stellar mass of the galaxy is estimated to be 3e11 M_solar, which
is as large as that of typical 3C radio galaxies at z=1.Comment: 12 pages, 4 Postscript figures, uses PASJ2.sty, PASJ95.sty,
PASJadd.sty. Accepted for publication in PASJ (2000
Dusty ERO Search behind Two Massive Clusters
We performed deep K'-band imaging observations of 2 massive clusters, MS
0451.6-0305 at z = 0.55 and MS 0440.5+0204 at z = 0.19, for searching
counterparts of the faint sub-mm sources behind these clusters, which would
provide one of the deepest extremely red object(ERO) samples. Comparing our
near-infrared images with optical images taken by the Hubble Space Telescope
and by the Subaru Telescope, we identified 13 EROs in these fields. The sky
distributions of EROs are consistent with the previous results, that there is a
sign of strong clustering among detected EROs. Also, the surface density with
corrected lensing amplification factors in both clusters are in good agreement
with that derived from previous surveys. We found 7 EROs and 3 additional very
red objects in a small area (\sim 0.6 arcmin^2) of the MS 0451.6-0305 field
around an extended SCUBA source. Many of their optical and near-infrared colors
are consistent with dusty star-forming galaxies at high redshifts(z \sim
1.0-4.0), and they may be constituting a cluster of dusty starburst galaxies
and/or lensed star-forming galaxies at high redshift. Their red J-K' colors and
faint optical magnitudes suggest they are relatively old massive stellar
systems with ages(>300 Mega years) suffering from dust obscuration. We also
found a surface-density enhancement of EROs around the SCUBA source in the MS
0440.5+0204 field.Comment: 19 pages, 11 figures, Latex(using pasj00.cls). To be published in
PASJ vol 55, No. 4(Aug 2003
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