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We present a magnetic field mapping of water maser clouds in the star-forming region W3 IRS5, which has been made on the basis of the linear polarization VLBI observation. Using the Very Long Baseline Array (VLBA) at 22.2 GHz, 16 of 61 detected water masers were found to be linearly polarized with polarization degrees up to 13%. Although 10 polarized features were widely distributed in the whole W3 IRS5 water maser region, they had similar position angles of the magnetic field vectors (~75 deg from the north). The magnetic field vectors are roughly perpendicular to the spatial alignments of the maser features. They are consistent with the hourglass model of the magnetic field, which was previously proposed to explain the magnetic field in the whole W3 Main region (r~0.1 pc). They are, on the other hand, not aligned to the directions of maser feature proper motions observed previously. This implies that the W3 IRS5 magnetic field was controlled by a collapse of the W3 Main molecular cloud rather than the outflow originated from W3 IRS5., 19 pages, 5 files, 1 table, accepted for publication in the Astrophysical Journal vol. 595, No.1 (2003 September 20 issue)

We have made multiepoch VLBA observations of water masers in the massive-star forming region W3 IRS 5. We measured radial velocities and proper motions of 108 water maser features during three observing sessions. The masers are clustered in two groups, which are associated with at least two different outflows. Positions of the outflow origins are close to the hypercompact radio continuum sources, which are clustered within a scale of 6000 AU. The continuum sources are probably driving sources of the outflows. We performed a three-dimensional kinematic model analysis of the maser motions in one of the two outflows, assuming a spherically symmetric expanding flow. We obtained a distance to the W3 IRS 5 region as 1.83 ? 0.14 kpc. The directions of the two outflows are roughly in the north-south direction, which is not significantly different from the direction of the global outflow seen in CO (J = 2-1) emission. This suggests that the massive-star cluster in the W3 IRS 5 region was created during formation of hierarchical structure in a parent molecular-cloud core. Such a structure is expected to preserve the angular momentum vector during star formation process, which may be along the directions of the present outflows.

We present aperture synthesis CO (J = 1-0) observations of the compact molecular outflow in the dark cloud B1 (Barnard 1). We have detected strong blueshifted emission having a peak brightness temperature of 14.3 K, while no significant emission was detected in the redshifted velocity range. The most prominent feature in our map is a distinct ringlike structure having a size of 25'' (8700 AU) × 14'' (5000 AU) at velocities blueshifted by 1.9-2.7 km s-1 from the systemic velocity. The central hole of the CO ring coincides well with the IRAS position, suggesting that this outflow is driven by the IRAS source, 03301+3057. The CO ring structure is interpreted as a conical outflow lobe with a brightened limb observed from its polar direction. The high-velocity gas that is blueshifted more than 4 km s-1 shows a V-shaped structure open to the southwest. This structure well delineates the northeast edge of the CO blue lobe observed with the single dish, where the CO lobe faces to the dense gas traced by the C18O emission. The strong peak of SiO emission observed by Yamamoto et al. is located at the interface between the CO outflow and the dense gas traced by the C18O and H13CO+ emission. This suggests that the outflow which emanates from the young star strongly interacts with the dense material and causes a shock that propagates into the surrounding cloud. The presence of strong SiO emission and the cold IRAS spectrum (log [Fν(60 μm)/Fν(100 μm)] < -0.76) suggest that the central source of B1 is a candidate for a protostar in the earliest evolutionary stage having an outflow in a nearly pole-on configuration.

We have carried out the first very long baseline interferometry (VLBI) imaging of 44 GHz class I methanol maser (7_{0}-6_{1}A^{+}) associated with a millimeter core MM2 in a massive star-forming region IRAS 18151-1208 with KaVA (KVN and VERA Array), which is a newly combined array of KVN (Korean VLBI Network) and VERA (VLBI Exploration of Radio Astrometry). We have succeeded in imaging compact maser features with a synthesized beam size of 2.7 milliarcseconds x 1.5 milliarcseconds (mas). These features are detected at a limited number of baselines within the length of shorter than approximately 650 km corresponding to 100 Mlambda in the uv-coverage. The central velocity and the velocity width of the 44 GHz methanol maser are consistent with those of the quiescent gas rather than the outflow traced by the SiO thermal line. The minimum component size among the maser features is ~ 5 mas x 2 mas, which corresponds to the linear size of ~ 15 AU x 6 AU assuming a distance of 3 kpc. The brightness temperatures of these features range from ~ 3.5 x 10^{8} to 1.0 x 10^{10} K, which are higher than estimated lower limit from a previous Very Large Array observation with the highest spatial resolution of ~ 50 mas. The 44 GHz class I methanol maser in IRAS 18151-1208 is found to be associated with the MM2 core, which is thought to be less evolved than another millimeter core MM1 associated with the 6.7 GHz class II methanol maser., Comment: 19 pages, 3 figures

We have made aperture synthesis observations of the very young planetary nebula CRL 618 by 12 CO J=1-0 line and continuum at 115.271 GHz with the Nobeyama Millimeter Array. The maps with the angular resolution of 3″.6×3″.5 show strong concentration of CO toward the ionized core with no clear evidence of a toroidal structure around the star nor along the axis of visible bipolar lobes. Velocity-channel maps show complex structures characterized by a spheroidal component weakly elongated to the east-west direction and a hornlike feature which looks to be spread from the center in a narrow opening angle. It seems difficult to interpret the maps by the simple model with a smooth outflow

We discuss the fragmentation of a filamentary molecular cloud on the basis of a magnetohydrodynamical stability analysis and the observations of the Orion A cloud with the Nobeyama 45 m telescope. Our model cloud has axial and helical magnetic fields and rotates around the axis. The dispersion relation for this cloud shows that the presence of a magnetic field and/or rotation shortens the wavelength of the most unstable mode, i.e., the mean distance between the adjacent fragments, measured in units of the filament diameter. We compare the theoretical results with the observed clumpy structure of the filamentary Orion A cloud and find that the sum of magnetic and centrifugal forces in the parent cloud was comparable with the pressure force (thermal and turbulent) and has had significant effects on the fragmentation

A first high-resolution survey of molecular cloud cores in the Orion A giant molecular cloud is reported. We identified 125 molecular cloud cores from an analysis of the spatial and velocity distribution of the CS (1-0) emission. The cores are generally elongated along the filamentary molecular cloud, and the axial ratio is about 0.5. The mass spectrum index of the cores is -1.6 for M≥50 M ○ .. The physical properties of the cores identified in Orion are compared with those of cores in dark clouds reported in the literature. The average radius of the cores in the Orion A cloud, 0.16 pc, is comparable to that of the cores in dark clouds

In the L1157 dark cloud, a well-collimated bipolar CO outflow associated with a cold IRAS source 20386+6751 have been discovered. The gas kinetic temperature toward the blue lobe of the outflow rises to-30 K from the temperature of the surrounding gas (≤10 K); this high temperature region is very localized with the blue lobe. The HCO + , HCN, and NH3 lines show blueshifted and broad-line profiles toward the blue CO lobe. Furthermore, their distributions are similar to that of the blue lobe

Interferometric observations of the 12 CO (J=1-0) and 2.6 mm continuum emission toward the young stellar object in B335 are presented. The angular resolution of 8″ × 5″ is a factor of 3 higher than those of the previous single-dish observations. The 12 CO high-velocity emission shows distinct biconical outflow structure having a size of a few thousand AU. The north-south extent of the outflow at its center is smaller than our present beam size, indicating that the outflow is focused within ∼1000 AU of its origin

Molecular line observations of the dark cloud L1221 in the J = 1-0 transitions of CO, 13 CO, C 18 O, HCO + , HCN, and CS with angular resolutions of 17″-2.7' are presented. A bipolar CO outflow associated with IRAS 22266+6845 have been discovered. The outflow shows a remarkably bent U-shaped structure. The present observations show rather clear evidence for interaction of the outflow with the ambient molecular gas; the ambient gas shows density depression and velocity shift just toward the blue lobe of the outflow. This fact indicates the acceleration and exclusion of the ambient gas by the outflow.

A search is made for circumnuclear C-12O (J = 1-0) emission from 12 Seyfert galaxies with recession velocities less than 5000 km/s, using the Nobeyama Radio Observatory 45 m telescope. Circumnuclear CO emission has been detected from four Seyfert galaxies. Among them, NGC 591 (= Mrk 1157) is a new detection. Comparing these results with those of published larger beam CO observations, molecular gas clouds are not highly concentrated in the circumnuclear zones in the Seyfert galaxies. This property is different from that of starburst nuclei, in which the inner surface density of molecular gas is significantly higher than that of the outer one. However, there is no significant difference in the circumnuclear molecular gas densities between the Seyferts and the starburst nuclei. This implies that the circumnuclear molecular gas density within a diameter of less than 5 kpc is not a key parameter which activity occurs in galactic nuclei. 39 refs.

H2O maser emission in the NGC 7538 molecular cloud has been mapped with the Nobeyama Millimeter Array with absolute and relative positional accuracies of 0.5 arcsec and 0.2 arcsec, respectively. Five new masers have been found within an 8 arcmin x 8 arcmin area. One is associated with IRS 9, and the other four are not associated with any known infrared or optical sources. The brightest H{sub 2}O maser spot is 3 arcmin southwest from IRS 11 with a flux density of 156 Jy. These masers may be related to premain-sequence objects and/or protostars in the NGC 7538 molecular cloud. Two previously known H{sub 2}O masers associated with IRS 1-3 and IRS 11 are resolved into 11 and 12 maser spots, respectively. The H{sub 2}O maser spots associated with IRS 1-3 seem to be separated into two groups: one of which is very close to the ultracompact H II region at IRS 1, and the other far from IRS 1. 36 refs.

The CO (J = 1-0) emission at 115.271 GHz from the compact planetary nebula IRAS 21282 + 5050 has been mapped. The results suggest that the CO gas forms an expanding torus with an axis along the east-west direction, normal to the line of sight. The kinematical age of the torus is estimated at about 21,000 D yr, where D is the distance to IRAS 21282 + 5050 in kpc. It is concluded that IRAS 21282 + 5050 is in earlier evolutionary stage of planetary nebular than NGC 7027 and NGC 2346. 20 refs.

Observations of the high-velocity flows in the high-density core region of the molecular cloud NGC 7538 are reported. The core region is found to be a very active site of the flows. Three such flows, associated with IRS 1, IRS 9, and IRS 11, and one possible candidate are found. The energy input into the core region from the flows is so large that it can compensate for the energy dissipation by turbulence in the region for at least several tens of thousands of years. If the conversion efficiency is near 100 percent, the flows will destroy the core region. 34 refs.

Millimeter-wave, near-IR, and 21 cm observations of the radio source G70.7 + 1.2 , which has been proposed to be a recent SNR developing inside a molecular cloud, are presented. A small molecular cloud with properties similar to a large dark cloud or globule is interacting with the nonthermal radio continuum source. The molecular cloud has a lumpy structure with its highest column density portion lying just outside the brightest portion of the radio continuum shell. If the radio source was produced by a supernova explosion, its kinetic energy was several orders of magnitude less than that of most observed supernovae. An OB star wind with certain characteristics is sufficient to drive the bubble, but the high radio continuum nonthermal surface brightness and polarization of the object is not explained by this model. 23 references.

The high-velocity (C-12)O (J = 1-0) emission in B335 with a high angular resolution of 16 arcsec has been mapped. The high-velocity emission shows distinct bipolar pattern centered at IRAS 19345+0727, toward which a strong high-velocity (C-12)O emission has been detected. The bipolar lobes delineate remarkable collimation toward the IRAS source, indicating that the flow is focused within 0.02 pc of the driving source. Each lobe is accompanied by significant wing emission with the opposite velocity shift, which clearly shows the association with IRAS 19345+0727. This feature is well explained as a bipolar flow the axis of which is nearly perpendicular to the line of sight. There is no evidence of another evolved bipolar flow which does not associate with any dense core as previously suggested. This suggests that B335 is a site of very recent star formation, containing a single bipolar flow with an age of about 30,000 yr. 15 references.