279 research outputs found
13CO(J=1-0) On-the-fly Mapping of the Giant HII Region NGC 604: Variation in Molecular Gas Density and Temperature due to Sequential Star Formation
We present 13CO(J=1-0) line emission observations with the Nobeyama 45-m
telescope toward the giant HII region NGC 604 in the spiral galaxy M 33. We
detected 13CO(J=1-0) line emission in 3 major giant molecular clouds (GMCs)
labeled as GMC-A, B, and C beginning at the north. We derived two line
intensity ratios, 13CO(J=1-0)/12CO(J =1-0), R13/12, and 12CO(J=3-2)/12CO(J
=1-0), R31, for each GMC at an angular resolution of 25" (100 pc). Averaged
values of R13/12 and R31 are 0.06 and 0.31 within the whole GMC-A, 0.11 and
0.67 within the whole GMC-B, and 0.05 and 0.36 within the whole GMC-C,
respectively. In addition, we obtained R13/12=0.09\pm0.02 and R31=0.76\pm0.06
at the 12CO(J=1-0) peak position of the GMC-B. Under the Large Velocity
Gradient approximation, we determined gas density of 2.8 \times10^3 cm^-3 and
kinetic temperature of 33+9-5 K at the 12CO(J=1-0) peak position of the GMC-B.
Moreover, we determined 2.5 \times10^3 cm^-3 and 25\pm2 K as averaged values
within the whole GMC-B. We concluded that dense molecular gas is formed
everywhere in the GMC-B because derived gas density not only at the peak
position of the GMC but also averaged over the whole GMC exceeds 10^3 cm^-3. On
the other hand, kinetic temperature averaged over the whole GM-B, 25 K, is
significantly lower than that at the peak position, 33 K. This is because HII
regions are lopsided to the northern part of the GMC-B, thus OB stars can heat
only the northern part, including the 12CO(J=1-0) peak position, of this GMC.Comment: 16 pages, 7 figures, PASJ in pres
NRO M33 All Disk Survey of Giant Molecular Clouds (NRO MAGiC): I. HI to H_2 Transition
We present the results of the Nobeyama Radio Observatory (NRO) M33 All Disk
(30'x30' or 7.3 kpc x 7.3 kpc) Survey of Giant Molecular Clouds (NRO MAGiC)
based on 12CO (1-0) observations using the NRO 45-m telescope. The spatial
resolution of the resultant map is 19".3, corresponding to 81 pc, which is
sufficient to identify each Giant Molecular Cloud (GMC) in the disk. We found
clumpy structures with a typical spatial scale of ~100 pc, corresponding to
GMCs, and no diffuse, smoothly distributed component of molecular gas at this
sensitivity. Closer inspection of the CO and HI maps suggests that not every CO
emission is associated with local HI peaks, particularly in the inner portion
of the disk (r < 2 kpc), although most of CO emission is located at the local
HI peaks in the outer radii. We found that most uncovered GMCs are accompanied
by massive star-forming regions, although the star formation rates (SFRs) vary
widely from cloud to cloud. The azimuthally averaged H{\sc i} gas surface
density exhibits a flat radial distribution. However, the CO radial
distribution shows a significant enhancement within the central 1-2 kpc region,
which is very similar to that of the SFR. We obtained a map of the molecular
fraction, f_mol = Sigma_H_2/(Sigma_HI+Sigma_H_2, at a 100-pc resolution. This
is the first f_mol map covering an entire galaxy with a GMC-scale resolution.
We find that f_mol tends to be high near the center. The correlation between
f_mol and gas surface density shows two distinct sequences. The presence of two
correlation sequences can be explained by differences in metallicity, i.e.,
higher (~ 2-fold) metallicity in the central region (r< 1.5 kpc) than in the
outer parts. Alternatively, differences in scale height can also account for
the two sequences, i.e., increased scale height toward the outer disk.Comment: Accepted for publication in PASJ, See
http://www.juen.ac.jp/lab/tosaki/paper/astro-ph/2011/tosaki2011.pdf for a
version with full resolution figure
Chemokine Receptor Expression in Oral Squamous Cell Carcinoma Correlation with Growth Factor- and Cytokine-mediated Cell Migration in vitro
AbstractMetastasis is the chief cause of mortality in cancer patients. Recently, chemokines and chemokine receptors were shown to play an important role in the metastasis of various cancers. We examined the role of chemokine receptor-mediated signaling in the invasion potential of human oral squamous cell carcinoma (OSCC) cell lines that were derived from 5 primary tumors and 6 cervical lymph node metastases. Comprehensive analysis of the mRNAs for human chemokine receptors showed that the OSCC cell lines had uniform expression patterns of chemokine receptors. Overall, there were no consistent differences in the expression of chemokine receptors between primary site- and lymph node metastasis-derived cell lines. However, a highly invasive OSCC cell line (SAS-H1) expressed up-regulation of CCR5, CCR6, CCR7, CXCR1, CXCR6 and CX3CR1 compared to a poorly invasive OSCC cell line (SAS-L1). Then we examined whether factors in the tumor microenvironment regulated chemokine receptor expression in SAS-H1 cells. Specifically, transforming growth factor (TGF) -β1 enhanced the expression of CCR5, CCR6, CCR7 and CX3CR1. Pretreatment of SAS-H1 cells with transforming growth factor (TGF) -β1 increased the expression of CCR7 and CX3CR1, and then enhanced CCL21- and CX3CL1-induced directional migration (1.5-fold enhancement as compared with untreated control). In addition, CX3CL1 increased the adhesion of SAS-H1 cells on uncoated tissue culture plates. Neither chemokine stimulated cell proliferation. Treatment of SAS-H1 cells with CX3CL1 activated the phosphotidylinositol-3-kinase (PI3K) and MEK signal transduction pathways. Our results suggest that chemokine receptor-mediated signaling is involved in the local invasion and metastasis of human OSCC
NRO M33 All-Disk Survey of Giant Molecular Clouds (NRO MAGiC): II. Dense Gas Formation within Giant Molecular Clouds in M33
We report the results of our observations of the 12CO (J=1-0) and 12CO
(J=3-2) line emission of 74 major giant molecular clouds (GMCs) within the
galactocentric distance of 5.1 kpc in the Local Group galaxy M33. The
observations have been conducted as part of the Nobeyama Radio Observatory M33
All-disk survey of Giant Molecular Clouds project (NRO MAGiC). The spatial
resolutions are 80 pc for 12CO (J=1-0) and 100 pc for 12CO (J=3-2). We detect
12CO (J=3-2) emission of 65 GMCs successfully. Furthermore, we find that the
correlation between the surface density of the star formation rate, which is
derived from a linear combination of Halpha and 24um emissions, and the 12CO
(J=3-2) integrated intensity still holds at this scale. This result show that
the star-forming activity is closely associated with warm and dense gases that
are traced with the 12CO (J=3-2) line, even in the scale of GMCs. We also find
that the GMCs with a high star-forming activity tend to show a high integrated
intensity ratio (R3-2/1-0). Moreover, we also observe a mass-dependent trend of
R3-2/1-0 for the GMCs with a low star-forming activity. From these results, we
speculate that the R3-2/1-0 values of the GMCs with a low star-forming activity
mainly depend on the dense gas fraction and not on the temperature, and
therefore, the dense gas fraction increases with the mass of GMCs, at least in
the GMCs with a low star-forming activity.Comment: 17 pages, 5 figures, Accepted for publication in PASJ, 2012, Vol. 64,
No.
Electronic Structure of the Novel Filled Skutterudite PrPt<sub>4</sub>Ge<sub>12</sub> Superconductor
We have performed soft x-ray photoemission spectroscopy (SXPES) and resonant photoemission spectroscopy (RPES) of the filled skutterudite superconductor PrPt4Ge12 in order to study the electronic structure of valence band and the character of Pr 4f. SXPES of PrPt4Ge12 measured with 1200 eV photon energy, where spectral contribution of Pr 4f is negligible, was found nearly identical with that of LaPt4Ge12, indicating similarity of Pt–Ge derived electronic states of the two compounds. Good correspondence with band calculations allows us to ascribe the dominant Ge 4p character of the density of states at the Fermi level (EF). Pr 3d → 4f RPES shows that, although Pr 4f electrons in PrPt4Ge12 are not as strongly hybridized with conduction electrons near EF as in PrFe4P12, there are finite Pr 4f contribution to the states near EF in PrPt4Ge12. These PES results give the information of fundamental electronic structure for understanding the physical properties of the novel filled skutterudite superconductor PrPt4Ge12
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