219 research outputs found
Dense and Warm Molecular Gas between Double Nuclei of the Luminous Infrared Galaxy NGC 6240
High spatial resolution observations of the 12CO(1-0), HCN(1-0), HCO+(1-0),
and 13CO(1-0) molecular lines toward the luminous infrared merger NGC 6240 have
been performed using the Nobeyama Millimeter Array and the RAINBOW
Interferometer. All of the observed molecular emission lines are concentrated
in the region between the double nuclei of the galaxy. However, the
distributions of both HCN and HCO+ emissions are more compact compared with
that of 12CO, and they are not coincident with the star-forming regions. The
HCN/12CO line intensity ratio is 0.25; this suggests that most of the molecular
gas between the double nuclei is dense. A comparison of the observed high
HCN/13CO intensity ratio, 5.9, with large velocity gradient calculations
suggests that the molecular gas is dense [n(H_2)=10^{4-6} cm^-3] and warm
(T_kin>50 K). The observed structure in NGC 6240 may be explained by time
evolution of the molecular gas and star formation, which was induced by an
almost head-on collision or very close encounter of the two galactic nuclei
accompanied with the dense gas and star-forming regions.Comment: 25 pages, 8 figures, To be appeared in PASJ 57, No.4 (August 25,
2005) issu
Millimeter Interferometric Investigations of the Energy Sources of Three Ultraluminous Infrared Galaxies, UGC 5101, Mrk 273, and IRAS 17208-0014, based on HCN to HCO+ Ratios
We present interferometric observations of three ultraluminous infrared
galaxies (ULIRGs; UGC 5101, Mrk 273, and IRAS 17208-0014) in the 3-mm
wavelength range, using the Nobeyama Millimeter Array. Both the HCN (J=1-0) and
HCO+ (J=1-0) molecular lines were observed simultaneously. HCN emission was
clearly detected at the nuclear positions of these ULIRGs, and HCO+ emission
was detected at the nuclear positions of UGC 5101 and IRAS 17208-0014. The HCN
to HCO+ brightness-temperature ratios toward the nuclei of the three ULIRGs
were derived and compared with those of lower luminosity galaxies known to be
dominated by active galactic nuclei (AGNs) or starbursts. In UGC 5101 and Mrk
273, where there is evidence for obscured AGNs from previous observations at
other wavelengths, we found high HCN/HCO+ ratios (>1.8) that are in the range
found for AGN-dominated galaxies. In IRAS 17208-0014, where the presence of a
powerful obscured AGN has been unclear, the ratio (1.7) is in between the
observed values for starburst- and AGN-dominated galaxies. The high HCN/HCO+
brightness-temperature ratios in UGC 5101 and Mrk 273 could be the consequence
of an HCN abundance enhancement, which is expected from chemical effects of the
central X-ray emitting AGN on the surrounding dense molecular gas. Our proposed
millimeter interferometric method based on HCN/HCO+ ratios may be an effective
tool for unveiling elusive buried AGNs at the cores of ULIRGs, especially
because of the negligible dust extinction at these wavelengths.Comment: 15 pages (emulateapj.sty), 8 figures (figures 1-5 resolution
reduced), Accepted for publication in Astronomical Journal, A PDF file with
high resolution is availble at
http://optik2.mtk.nao.ac.jp/~imanishi/Paper/HCN/HCN.pd
The Virgo High-Resolution CO Survey I. CO Atlas
We present the results of the Virgo high-resolution CO survey (ViCS) obtained
with the Nobeyama Millimeter-wave Array (NMA). This survey was made in the
course of a long-term project at Nobeyama from 1999 December through 2002
April. The objects were selected from Virgo cluster members, considering CO
richness from single dish flux, mild inclination, and lack of strong tidal
perturbations. The central 1 arc min regions (4.7 kpc) of 15 spiral galaxies
were observed with resolutions of 2 to 5 arcsec and 10 to 20 km/s, and
sensitivities of 20 mJy/ beam for a 10 km/s channel. The objects lie at the
same distance of the Virgo cluster (16.1 Mpc), which is advantageous for
comparisons among individual galaxies. We describe the details of observations
and data reduction, and present an atlas of integrated CO intensity maps,
velocity fields and position-velocity diagrams along the major axes. The
molecular gas morphology in the Virgo galaxies shows a wealth of variety, not
specifically depending on the Hubble types.Comment: PASJ 2003 in press, Latex 16 pages, 7 figures (Bigger size ps/gif
figures available at http://www.ioa.s.u-tokyo.ac.jp/radio/virgo
Arc-like distribution of high CO(J=3-2)/CO(J=1-0) ratio gas surrounding the central star cluster of the supergiant HII region NGC 604
We report the discovery of a high CO(J=3-2)/CO(J=1-0) ratio gas with an
arc-like distribution (``high-ratio gas arc'') surrounding the central star
cluster of the supergiant HII region NGC 604 in the nearby spiral galaxy M 33,
based on multi-J CO observations of a 5' 5' region of NGC 604
conducted using the ASTE 10-m and NRO 45-m telescopes. The discovered
``high-ratio gas arc'' extends to the south-east to north-west direction with a
size of 200 pc. The western part of the high-ratio gas arc closely
coincides well with the shells of the HII regions traced by H and radio
continuum peaks. The CO(J=3-2)/CO(J=1-0) ratio, R_{3-2/1-0}, ranges between 0.3
and 1.2 in the observed region, and the R_{3-2/1-0} values of the high-ratio
gas arc are around or higher than unity, indicating very warm (T_kin > 60 K)
and dense (n(H_2) > 10^{3-4} cm^{-3}) conditions of the high-ratio gas arc. We
suggest that the dense gas formation and second-generation star formation occur
in the surrounding gas compressed by the stellar wind and/or supernova of the
first-generation stars of NGC 604, i.e., the central star cluster of NGC 604.Comment: 4 pages, 4 figures. The Astrophysical Journal Letters, in pres
Near-infrared and Millimeter Constraints on the Nuclear Energy Source of the Infrared Luminous Galaxy NGC 4418
We present near-infrared and millimeter investigations of the nucleus of the
infrared luminous galaxy NGC 4418, which previous observations suggest
possesses a powerful buried AGN. We found the following main results: (1) The
infrared K-band spectrum shows CO absorption features at 2.3-2.4 micron owing
to stars and very strong H2 emission lines. The luminosity ratios of H2
emission lines are suggestive of a thermal origin, and the equivalent width of
the H2 1-0 S(1) line is the second largest observed to date in an external
galaxy, after the well-studied strong H2-emitting galaxy NGC 6240. (2) The
infrared L-band spectrum shows a clear polycyclic aromatic hydrocarbon (PAH)
emission feature at 3.3 micron, which is usually found in star-forming
galaxies. The estimated star-formation luminosity from the observed PAH
emission can account for only a small fraction of the infrared luminosity. (3)
Millimeter interferometric observations of the nucleus reveal a high HCN (1-0)
to HCO+ (1-0) luminosity ratio of 1.8, as has been previously found in pure
AGNs. (4) The measurements of HCN (1-0) luminosity using a single-dish
millimeter telescope show that the HCN (1-0) to infrared luminosity ratio is
slightly larger than the average, but within the scattered range, for other
infrared luminous galaxies. All of these results can be explained by the
scenario in which, in addition to energetically-insignificant, weakly-obscured
star-formation at the surface of the nucleus, a powerful X-ray emitting AGN
deeply buried in dust and high density molecular gas is present.Comment: 31 pages, 9 figures, Accepted for publication in Astronomical Journal
(2004 November issue
A novel variant fibrinogen, deletion of B beta 111Ser in coiled-coil region, affecting fibrin lateral aggregation
ArticleCLINICA CHIMICA ACTA. 365(1-2): 160-167 (2006)journal articl
Millimeter Interferometric HCN(1-0) and HCO+(1-0) Observations of Luminous Infrared Galaxies
We present the results on millimeter interferometric observations of four
luminous infrared galaxies (LIRGs), Arp 220, Mrk 231, IRAS 08572+3915, and VV
114, and one Wolf-Rayet galaxy, He 2-10, using the Nobeyama Millimeter Array
(NMA). Both the HCN(1-0) and HCO+(1-0) molecular lines were observed
simultaneously and their brightness-temperature ratios were derived.
High-quality infrared L-band (2.8-4.1 micron) spectra were also obtained for
the four LIRGs to better constrain their energy sources deeply buried in dust
and molecular gas. When combined with other LIRGs we have previously observed
with NMA, the final sample comprised nine LIRGs (12 LIRGs' nuclei) with
available interferometric HCN(1-0) and HCO+(1-0) data-sufficient to investigate
the overall trend in comparison with known AGNs and starburst galaxies. We
found that LIRGs with luminous buried AGN signatures at other wavelengths tend
to show high HCN(1-0)/HCO+(1-0) brightness-temperature ratios as seen in
AGN-dominated galaxies, while the Wolf-Rayet galaxy He 2-10 displays a small
ratio. An enhanced HCN abundance in the interstellar gas surrounding a strongly
X-ray-emitting AGN, as predicted by some chemical calculations, is a natural
explanation of our results.Comment: 43 pages, 11 figures, accepted for publication in Astronomical
Journal. Higher resolution version is available at
http://optik2.mtk.nao.ac.jp/~imanishi/Paper/HCN2/HCN2.pd
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