101 research outputs found
3-D Kinematics of Water Masers in the W51A Region
We report proper motion measurements of water masers in the massive-star
forming region W51A and the analyses of the 3-D kinematics of the masers in
three maser clusters of W51A (W51 North, Main, and South). In W~51 North, we
found a clear expanding flow that has an expansion velocity of ~70 km/s and
indicates deceleration. The originating point of the flow coincides within 0.1
as with a silicon-monoxide maser source near the HII region W~51d. In W51 Main,
no systematic motion was found in the whole velocity range (158 km/s =< V(lsr)
=< -58 km/s) although a stream motion was reported previously in a limited
range of the Doppler velocity (54 km/s =< V(lsr) =< 68 kms). Multiple driving
sources of outflows are thought to explain the kinematics of W51 Main. In W51
South, an expansion motion like a bipolar flow was marginally visible. Analyses
based on diagonalization of the variance-covariance matrix of maser velocity
vectors demonstrate that the maser kinematics in W51 North and Main are
significantly tri-axially asymmetric. We estimated a distance to W51 North to
be 6.1 +/- 1.3 kpc on the basis of the model fitting method adopting a radially
expanding flow.Comment: 20 pages, 8 figures, 8 tables, appear in the NRO report No. 564
(ftp://ftp.nro.nao.ac.jp/nroreport/PASJ-W51.pdf) and will appear in Publ.
Astron. Soc. Japan, Vol. 54, No. 5 (10/25 issue
A Complete Survey of the Central Molecular Zone in NH3
We present a map of the major part of the central molecular zone (CMZ) of
simultaneous observations in the NH3 (J,K) = (1,1) and (2,2) lines using the
Kagoshima 6-m telescope. The mapped area is -1.000 < l < 1.625 deg, -0.375 < b
< +0.250 deg. The kinetic temperatures derived from the (2,2) to (1,1)
intensity ratios are 20--80 K or exceed 80 K. The gases corresponding to
temperature of 20--80 K and > 80 K contain 75% and 25% of the total NH3 flux,
respectively. These temperatures indicate that the dense molecular gas in the
CMZ is dominated by gas that is warmer than the majority of the dust present
there. A comparison with the CO survey by Sawada et al. (2001) shows that the
NH3 emitting region is surrounded by a high pressure region on the l-v plane.
Although NH3 emission traces dense gas, it is not extended into a high pressure
region. Therefore, the high pressure region is less dense and has to be hotter.
This indicates that the molecular cloud complex in the Galactic center region
has a ``core'' of dense and warm clouds which are traced by the NH3 emission,
and an ``envelope'' of less dense and hotter gas clouds. Besides heating by
ambipolar diffusion, the hot plasma gas emitting the X-ray emission may heat
the hot ``envelope''.Comment: 21 pages, 14 figures, accepted for PAS
Distance to G14.33-0.64 in the Sagittarius Spiral Arm: H2O Maser Trigonometric Parallax with VERA
We report on trigonometric parallax measurements for the Galactic star
forming region G14.33-0.64 toward the Sagittarius spiral arm. We conducted
multi-epoch phase-referencing observations of an H2O maser source in
G14.33-0.64 with the Japanese VLBI array VERA. We successfully detected a
parallax of 0.893+/-0.101 mas, corresponding to a source distance of
1.12+/-0.13 kpc, which is less than half of the kinematic distance for
G14.33-0.64. Our new distance measurement demonstrates that the Sagittarius arm
lies at a closer distance of ~1 kpc, instead of previously assumed ~2-3 kpc
from kinematic distances. The previously suggested deviation of the Sagittarius
arm toward the Galactic center from the symmetrically fitted model (Taylor &
Cordes 1993) is likely due to large errors of kinematic distances at low
galactic longitudes. G14.33-0.64 most likely traces the near side of the
Sagittarius arm. We attempted fitting the pitch angle of the arm with other
parallax measurements along the arm, which yielded two possible pitch angles of
i=34.7+/-2.7 degrees and i=11.2+/-10.5 degrees. Our proper motion measurements
suggest G14.33-0.64 has no significant peculiar motion relative to the
differential rotation of the Galaxy (assumed to be in a circular orbit),
indicating that the source motion is in good agreement with the Galactic
rotation.Comment: 14 pages, 7 figures, to appear in PASJ Vol. 62, No.
VLBI Monitoring Observations of Water Masers Around the Semi-Regular Variable Star R Crateris
We monitored water-vapor masers around the semi-regular variable star R
Crateris with the Japanese VLBI Network (J-Net) at the 22 GHz band during four
epochs with intervals of one month. The relative proper motions and
Doppler-velocity drifts of twelve maser features were measured. Most of them
existed for longer than 80 days. The 3-D kinematics of the features indicates a
bipolar expanding flow. The major axis of the asymmetric flow was estimated to
be at P.A. = 136 degrees. The existence of a bipolar outflow suggests that a
Mira variable star had already formed a bipolar outflow. The water masers are
in a region of apparent minimum radii of 1.3 x 10^12 m and maximum radii of 2.6
x 10^12 m, between which the expansion velocity ranges from 4.3 to 7.4 km/s.
These values suggest that the water masers are radially accelerated, but still
gravitationally bound, in the water-maser region. The most positive and
negative velocity-drifting features were found relatively close to the systemic
velocity of the star. We found that the blue-shifted features are apparently
accelerated and the red-shifted apparently decelerated. The acceleration of
only the blue-shifted features seems to be consistent with that of the
expanding flow from the star.Comment: 15 pages, 5 figures, Accepted for publication in PASJ (2001),
preprint can be obtained via WWW on
http://www.nro.nao.ac.jp/library/report/list.htm
VLBI Astrometry of the Semiregular Variable RX Bootis
We present distance measurement of the semiregular variable RX Bootis (RX
Boo) with its annual parallax. Using the unique dual-beam system of the VLBI
Exploration of Radio Astrometry (VERA) telescope, we conducted astrometric
observations of a water maser spot accompanying RX Boo referred to the quasar
J1419+2706 separated by 1.69 degrees from RX Boo. We have measured the annual
parallax of RX Boo to be 7.31 +/- 0.50 mas, corresponding to a distance of 136
+10/-9 pc, from the one-year monitoring observation data of one maser spot at
VLSR = 3.2 km/s. The distance itself is consistent with the one obtained with
Hipparcos. The distance uncertainty is reduced by a factor of two, allowing us
to determine the stellar properties more accurately. Using our distance, we
discuss the location of RX Boo in various sequences of Period-Luminosity (PL)
relations. We found RX Boo is located in the Mira sequence of PL relation. In
addition, we calculated the radius of photosphere and the mass limitation of RX
Boo and discussed its evolutionary status.Comment: 8 pages, 4figure
Annual Parallax Distance to the K-type star system IRAS 22480+6002 measured with VERA
We present the astrometric VLBI observations of water masers associated with
IRAS 22480+6002 (IRC+60370, hereafter I22480) with the VLBI Exploration of
Radio Astrometry (VERA). The stellar type of I22480 looks unusual as a stellar
maser source and has been debated since the 1970s. We successfully determined
the annual parallax of a group of the water maser spots, pi=0.400+/-0.025 mas,
corresponding to a distance to I22480 of D=2.50 /+0.17/-0.15 kpc. This suggests
that the estimated bolometric luminosity of I22480 should be revised to 35 000
L_sun, favoring a K-type supergiant rather than an RV Tau-type variable star
previously suggested. Although the spectral type is unusual as a stellar maser
source, the internal motions of the water maser features suggest that the water
masers are associated with the circumstellar envelope of this star. Taking into
account a possible stellar motion with respect to the maser feature motions, we
derived a secular proper motion of I22480, (mu_alpha, mu_delta)=(-2.58+/-0.33,
-1.91+/-0.17) [mas yr^-1]. The derived motion of I22480 in the Milky Way has a
deviation by ~ -30 km/s in the galactic azimuthal direction from a circular
motion estimated from the galactocentric distance to I22480 and assumption of a
flat Galactic rotation curve. This peculiar motion is still comparable to those
typically seen in the water maser sources located in the Perseus spiral arm.
Taking into account the peculiar motion and the proximity to the Galactic
midplane (z ~60 pc), I22480 may be a member of the Galactic thin disk.Comment: 11 pages, 7 figures, accepted by PASJ (issue on vol. 65, No.1).
Figure formats were correcte
Astaxanthin Exerts Immunomodulatory Effect by Regulating SDH-HIF-1α Axis and Reprogramming Mitochondrial Metabolism in LPS-Stimulated RAW264.7 Cells
Astaxanthin (AX) is a carotenoid that exerts potent antioxidant activity and acts in cell membranes and mitochondria, which consist of the bilayer molecules. Targeting mitochondria to ameliorate inflammatory diseases by regulating mitochondrial metabolism has become possible and topical. Although AX has been shown to have anti-inflammatory effects in various cells, the mechanisms are quite different. In particular, the role of AX on mitochondrial metabolism in macrophages is still unknown. In this study, we investigated the effect of AX on mitochondria-mediated inflammation and its mechanisms in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. AX attenuated the mitochondrial O2− production and maintained the mitochondrial membrane potential, implying that AX preserved mitochondrial homeostasis to avoid LPS stimulation-induced mitochondrial dysfunction. Additionally, AX prevented the decrease in mitochondrial complexes I, II, and III, which were caused by LPS stimulation. Especially, AX inhibited the reduction in mitochondrial succinate dehydrogenase (SDH; complex II) activity and upregulated the protein and mRNA level of SDH complex, subunit B. Furthermore, AX blocked the IL-1β expression by regulating the SDH-HIF-1α axis and suppressed the energy shift from an OXPHOS phenotype to a glycolysis phenotype. These findings revealed important effects of AX on mitochondrial enzymes as well as on mitochondrial energy metabolism in the immune response. In addition, these raised the possibility that AX plays an important role in other diseases caused by SDH mutation and metabolic disorders
Monitoring Observations of the Jupiter-Family Comet 17P/Holmes during 2014 Perihelion Passage
We performed a monitoring observation of a Jupiter-Family comet, 17P/Holmes,
during its 2014 perihelion passage to investigate its secular change in
activity. The comet has drawn the attention of astronomers since its historic
outburst in 2007, and this occasion was its first perihelion passage since
then. We analyzed the obtained data using aperture photometry package and
derived the Afrho parameter, a proxy for the dust production rate. We found
that Afrho showed asymmetric properties with respect to the perihelion passage:
it increased moderately from 100 cm at the heliocentric distance r_h=2.6-3.1 AU
to a maximal value of 185 cm at r_h = 2.2 AU (near the perihelion) during the
inbound orbit, while dropping rapidly to 35 cm at r_h = 3.2 AU during the
outbound orbit. We applied a model for characterizing dust production rates as
a function of r_h and found that the fractional active area of the cometary
nucleus had dropped from 20%-40% in 2008-2011 (around the aphelion) to
0.1%-0.3% in 2014-2015 (around the perihelion). This result suggests that a
dust mantle would have developed rapidly in only one orbital revolution around
the sun. Although a minor eruption was observed on UT 2015 January 26 at r_h =
3.0 AU, the areas excavated by the 2007 outburst would be covered with a layer
of dust (<~ 10 cm depth) which would be enough to insulate the subsurface ice
and to keep the nucleus in a state of low activity.Comment: 25 pages, 6 figures, 2 tables, ApJ accepted on December 29, 201
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