The protostellar jet driven by L1448C was observed in the SiO J=8-7 and CO J=3-2 lines and 350 GHz dust continuum at ∼1 ′′ resolution with the Submillimeter Array (SMA). A narrow jet from the northern source L1448C(N) was observed in the SiO and the high-velocity CO. The jet consists of a chain of emission knots with an inter-knot spacing of ∼2 ′′ (500 AU) and a semi-periodic velocity variation. These knots are likely to be the internal bow shocks in the jet beam that were formed due to the periodic variation of the ejection velocity with a period of ∼15-20 yr. The innermost pair of knots, which are significant in the SiO map but barely seen in the CO, are located at ∼1 ′′ (250 AU) from the central source, L1448C(N). Since the dynamical time scale for the innermost pair is only ∼10 yr, SiO may have been formed in the protostellar wind through the gas-phase reaction, or been formed on the dust grain and directly released into the gas phase by means of shocks. It is found that the jet is extremely active with a mechanical luminosity of ∼7 L ⊙ , which is comparable to the bolometric luminosity of the central source (7.5 L ⊙ ). The mass accretion rate onto the protostar derived from the mass-loss rate is ∼10 −5 M ⊙ yr −1 . Such a high mass accretion rate suggests that the mass and the age of the central star are 0.03-0.09 M ⊙ and (4-12)×10 3 yr, respectively, implying that the central star is in the very early stage of protostellar evolution. The low-velocity CO emission delineates two Vshaped shells with a common apex at L1448C(N). The kinematics of these shells are reproduced by the model of a wide opening angle wind. The co-existence of the highly-collimated jets and the wide-opening angle shells can be explained by the "unified X-wind model" in which highly-collimated jet components correspond to the on-axis density enhancement of the wide-opening angle wind. The CO J=3-2 map also revealed the second outflow driven by the southern source L1448C(S) located at ∼8.3 ′′ (2000 AU) from L1448C(N). Although L1448C(S) is

We present the first submm (865 µm) imaging spectral line survey at one arcsecond resolution conducted with the Submillimeter Array toward Orion-KL. Within the two × two GHz bandpasses (lower and upper sidebands,, we find about 145 spectral lines from 13 species, 6 isotopologues, and 5 vibrational excited states. Most nitrogen-bearing molecules are strong toward the hot core, whereas the oxygen-bearing molecules peak toward the south-west in the so-called compact ridge. Imaging of spectral lines is shown to be an additional tool to improve the identifications of molecular lines. Arcsecond spatial resolution allows us to distinguish the molecular line emission of the sources I and n from that of the hot core. The only molecular species detected strongly toward source I is SiO, delineating mainly the collimated north-east south-west low-velocity outflow. The two positions close to source I, which have previously been reported to show maser emission in the v=0 28 SiO(1-0) and (2-1) lines, show no detectable maser emission in the v=0 28 SiO(8-7) line at our spatial resolution. SiO is weak toward source n, and thus source n may not currently be driving a molecular outflow. CH 3 OH is the molecule with the highest number of identified lines (46) in this spectral window. This "line forest" allows us to estimate temperatures in the region, and we find temperatures between 50 and 350 K, with the peak temperatures occurring toward the hot core. The detection of strong vibrational excited line emission from the submm continuum peak SMA1 supports the interpretation that the source SMA1 is likely of protostellar nature.

Arcsecond-resolution spectral observations toward the protobinary system IRAS 16293-2422 at 344 and 354 GHz were conducted using the Submillimeter Array. Complex organic molecules such as CH 3 OH and HCOOCH 3 were detected. Together with the rich organic inventory revealed, it clearly indicates the existence of two, rather than one, compact hot molecular cores ( 400 AU in radius) associated with each of the protobinary components identified by their dust continuum emission in the inner star-forming core.

We present the first 865 mm continuum image with subarcsecond resolution obtained with the Submillimeter Array. These data resolve the Orion KL region into the hot core, the nearby radio source I, the submillimeter counterpart to the infrared source n (radio source L), and new submillimeter continuum sources. The radio to submillimeter emission from source I can be modeled as either the result of proton-electron free-free emission that is optically thick to ∼100 GHz plus dust emission that accounts for the majority of the submillimeter flux, or H Ϫ free-free emission that gives rise to a power-law spectrum with a power-law index of ∼1.6. The latter model would indicate similar physical conditions as found in the inner circumstellar environment of Mira variable stars. Future subarcsecond resolution observations at shorter submillimeter wavelengths should easily discriminate between these two possibilities. The submillimeter continuum emission toward source n can be interpreted in the framework of emission from an accretion disk.

We have mapped the SiO J p 5-4 line at 217 GHz from the HH 211 molecular outflow with the Submillimeter Array (SMA). The high-resolution map (1Љ .6 # 0Љ .9) shows that the SiO J p 5-4 emission comes from the central narrow jet along the outflow axis with a width of ∼0Љ .8 (∼250 AU) FWHM. The SiO jet consists of a chain of knots separated by 3Љ-4Љ (∼1000 AU), and most of the SiO knots have counterparts in shocked H 2 emission seen in a new, deep VLT near-infrared image of the outflow. A new, innermost pair of knots have been discovered at just ‫2ע‬Љ from the central star. The line ratio between the SiO J p 5-4 data and the upper limits from the SiO J p 1-0 data of Chandler & Richer suggests that these knots have a temperature in excess of 300-500 K and a density of (0.5-1) # 10 7 cm Ϫ3 . The radial velocity measured for these knots is ∼30 km s Ϫ1 , comparable to the maximum velocity seen in the entire jet. The high temperature, high density, and velocity structure observed in this pair of SiO knots suggest that they are closely related to the primary jet launched close to the protostar.