High Angular Resolution, Sensitive CS J=2-1 and J=3-2 Imaging of the Protostar L1551 NE: Evidence for Outflow-Triggered Star Formation ?

High angular resolution and sensitive aperture synthesis observations of CS ($J=2-1$) and CS ($J=3-2$) emissions toward L1551 NE, the second brightest protostar in the Taurus Molecular Cloud, made with the Nobeyama Millimeter Array are presented. L1551 NE is categorized as a class 0 object deeply embedded in the red-shifted outflow lobe of L1551 IRS 5. Previous studies of the L1551 NE region in CS emission revealed the presence of shell-like components open toward L1551 IRS 5, which seem to trace low-velocity shocks in the swept-up shell driven by the outflow from L1551 IRS 5. In this study, significant CS emission around L1551 NE was detected at the eastern tip of the swept-up shell from $V_{\rm{lsr}}$ = 5.3 km s$^{-1}$ to 10.1 km s$^{-1}$, and the total mass of the dense gas is estimated to be 0.18 $\pm$ 0.02 $M_\odot$. Additionally, the following new structures were successfully revealed: a compact disklike component with a size of $\approx$ 1000 AU just at L1551 NE, an arc-shaped structure around L1551 NE, open toward L1551 NE, with a size of $\sim 5000$ AU, i.e., a bow shock, and a distinct velocity gradient of the dense gas, i.e., deceleration along the outflow axis of L1551 IRS 5. These features suggest that the CS emission traces the post-shocked region where the dense gas associated with L1551 NE and the swept-up shell of the outflow from L1551 IRS 5 interact. Since the age of L1551 NE is comparable to the timescale of the interaction, it is plausible that the formation of L1551 NE was induced by the outflow impact. The compact structure of L1551 NE with a tiny envelope was also revealed, suggesting that the outer envelope of L1551 NE has been blown off by the outflow from L1551 IRS 5.Comment: 29 pages, 12 figures, Accepted for Publication in the Astrophysical Journa

GRAVITATIONAL EFFECT ON GROWTH OF InX Ga1-XSb TERNARY BULK CRYSTALS

The effect of gravity on dissolution of GaSb in InSb melt and growth of InGaSb was experimentally investigated using GaSb(seed)/InSb/GaSb(feed) sandwich samples. Two parameters were considered: (1) the inclination angle of the sample for gravity as 0°, 53° and 90°, (2) the sample diameter (D) as 9 mm and 5mm. When θ =0°, the interface was almost flat whereas the interfaces were strongly distorted when θ = 53° and 90°. The undissolved GaSb(feed) remained for \theta = 0 °. However, it dissolved completely for θ = 90°, and partially for θ = 53°. As the gravitational angle was increased, the growth length of uniform composition became long. The decrease of sample diameter reduced the dissolution area of GaSb. These facts indicated that the dissolution and growth processes were strongly influenced by gravity

High abundance ratio of 13^{13}CO to C18^{18}O toward photon-dominated regions in the Orion-A giant molecular cloud

Aims. We derive physical properties such as the optical depths and the column densities of $^{13}$CO and C$^{18}$O to investigate the relationship between the far ultraviolet (FUV) radiation and the abundance ratios between $^{13}$CO and C$^{18}$O. Method. We have carried out wide-field (0.4 deg$^2$) observations with an angular resolution of 25.8 arcsec ($\sim$ 0.05 pc) in $^{13}$CO ($J$=1--0) and C$^{18}$O ($J$=1--0) toward the Orion-A giant molecular cloud using the Nobeyama 45 m telescope in the on-the-fly mode. Results. Overall distributions and velocity structures of the $^{13}$CO and C$^{18}$O emissions are similar to those of the $^{12}$CO ($J$=1--0) emission. The optical depths of the $^{13}$CO and C18O emission lines are estimated to be 0.05 $<$ $\tau_{\rm ^{13}CO}$ $<$ 1.54 and 0.01 $<$ $\tau_{\rm C^{18}O}$ $<$ 0.18, respectively. The column densities of the $^{13}$CO and C$^{18}$O emission lines are estimated to be 0.2 $\times$ 10$^{16}$ $<$ $N_{\rm ^{13}CO}$ $<$ 3.7 $\times$ 10$^{17}$ cm$^{-2}$ and 0.4 $\times$ 10$^{15}$ $<$ $N_{\rm C^{18}O}$ $<$ 3.5 $\times$ 10$^{16}$ cm$^{-2}$, respectively. The abundance ratios between $^{13}$CO and C$^{18}$O, $X_{\rm ^{13}CO}$/$X_{\rm C^{18}O}$, are found to be 5.7 - 33.0. The mean value of $X_{\rm ^{13}CO}$/$X_{\rm C^{18}O}$ in the nearly edge-on photon-dominated regions is found to be 16.47 $\pm$ 0.10, which is a third larger than that the solar system value of 5.5. The mean value of $X_{\rm ^{13}CO}$/$X_{\rm C^{18}O}$ in the other regions is found to be 12.29 $\pm$ 0.02. The difference of the abundance ratio is most likely due to the selective FUV photodissociation of C$^{18}$O.Comment: 11 pages, 9 figures, Accepted to A&

Detection of Strong Millimeter Emission from the Circumstellar Dust Disk Around V1094 Sco: Cold and Massive Disk around a T Tauri Star in a Quiescent Accretion Phase?

We present the discovery of a cold massive dust disk around the T Tauri star V1094 Sco in the Lupus molecular cloud from the 1.1 millimeter continuum observations with AzTEC on ASTE. A compact ($r\lesssim$320 AU) continuum emission coincides with the stellar position having a flux density of 272 mJy which is largest among T Tauri stars in Lupus. We also present the detection of molecular gas associated with the star in the five-point observations in $^{12}$CO J=3--2 and $^{13}$CO J=3--2. Since our $^{12}$CO and $^{13}$CO observations did not show any signature of a large-scale outflow or a massive envelope, the compact dust emission is likely to come from a disk around the star. The observed SED of V1094 Sco shows no distinct turnover from near infrared to millimeter wavelengths, which can be well described by a flattened disk for the dust component, and no clear dip feature around 10 \micron suggestive of absence of an inner hole in the disk. We fit a simple power-law disk model to the observed SED. The estimated disk mass ranges from 0.03 to $\gtrsim$0.12 M_\sun, which is one or two orders of magnitude larger than the median disk mass of T Tauri stars in Taurus.Comment: 18 pages, 4 figures, accepted for publication in Ap