We present a study of dense molecular gas kinematics in seventeen nearby protostellar systems using single-dish and interferometric molecular line observations. The non-axisymmetric envelopes around a sample of Class 0/I protostars were mapped in the N 2 H + (J = 1 → 0) tracer with the IRAM 30m, CARMA and PdBI as well as NH 3 (1,1) with the VLA. The molecular line emission is used to construct line-center velocity and linewidth maps for all sources to examine the kinematic structure in the envelopes on spatial scales from 0.1 pc to ∼1000 AU. The direction of the large-scale velocity gradients from single-dish mapping is within 45 • of normal to the outflow axis in more than half the sample. Furthermore, the velocity gradients are often quite substantial, the average being ∼2.3 km s −1 pc −1 . The interferometric data often reveal small-scale velocity structure, departing from the more gradual large-scale velocity gradients. In some cases, this likely indicates accelerating infall and/or rotational spin-up in the inner envelope; the median velocity gradient from the interferometric data is ∼10.7 km s −1 pc −1 . In two systems, we detect high-velocity HCO + (J = 1 → 0) emission inside the highestvelocity N 2 H + emission. This enables us to study the infall and rotation close to the disk and estimate the central object masses. The velocity fields observed on large and small-scales are more complex than would be expected from rotation alone, suggesting that complex envelope structure enables other dynamical processes (i.e. infall) to affect the velocity field. 1 Based on observations carried out with the IRAM 30m Telescope and IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).-5with 20kHz channels and in 2009 we used 40 MHz with 20kHz channels; see Table 2 the list of sources observed and more detail.We conducted our observations using frequency-switched on-the-fly (OTF) mapping mode. The maps varied in size depending on the extent of the source being observed, most being 3 × 3 . Most maps were integrated down to at least σ T ∼ 150mK for the N 2 H + (J = 1 → 0) transition, noise levels for each map are listed in Table 2. We mapped the sources by scanning in the northsouth direction and again in the east-west direction to minimize striping in the final map. The scan legs were stepped by 5 and we repeated the maps to gain a higher signal-to-noise ratio. Calibration scans were taken about every 10 minutes between scan legs and the final maps took approximately 2 hours to complete. Pointing was checked about every two hours, azimuth and elevation offsets were typically ±5 ; the pointing offset remained stable, typically within ∼2 during an observation. These values agree well with the rms pointing accuracy of ∼2 .

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We present a high angular resolution ( 0. 2  ), high-sensitivity ( 0.2 s~mJy) survey of the 870 μm continuum emission from the circumstellar material around 49 pre-main-sequence stars in the ρ Ophiuchus molecular cloud. Because most millimeter instruments have resided in the northern hemisphere, this represents the largest highresolution, millimeter-wave survey of the circumstellar disk content of this cloud. Our survey of 49 systems comprises 63 stars; we detect disks associated with 29 single sources, 11 binaries, 3 triple systems, and 4 transition disks. We present flux and radius distributions for these systems; in particular, this is the first presentation of a reasonably complete probability distribution of disk radii at millimeter wavelengths. We also compare the flux distribution of these protoplanetary disks with that of the disk population of the Taurus-Auriga molecular cloud. We find that disks in binaries are both significantly smaller and have much less flux than their counterparts around isolated stars. We compute truncation calculations on our binary sources and find that these disks are too small to have been affected by tidal truncation and posit some explanations for this. Lastly, our survey found three candidate gapped disks, one of which is a newly identified transition disk with no signature of a dip in infrared excess in extant observations.

We use archived IRAC images from the Spitzer Space Telescope to show that many Class 0 protostars exhibit complex, irregular, and non-axisymmetric structure within their dusty envelopes. Our 8 µm extinction maps probe some of the densest regions in these protostellar envelopes. Many of the systems are observed to have highly irregular and non-axisymmetric morphologies on scales 1000 AU, with a quarter of the sample exhibiting filamentary or flattened dense structures. Complex envelope structure is observed in regions spatially distinct from outflow cavities, and the densest structures often show no systematic alignment perpendicular to the cavities. These results indicate that mass ejection is not responsible for much of the irregular morphologies we detect; rather, we suggest that the observed envelope complexity is mostly the result of collapse from protostellar cores with initially non-equilibrium structures. The striking nonaxisymmetry in many envelopes could provide favorable conditions for the formation of binary systems. We also note that protostars in the sample appear to be formed preferentially near the edges of clouds or bends in filaments, suggesting formation by gravitational focusing.

We present dust opacity spectral indexes (β) of the youngest protostellar systems (so-called Class 0 sources), L1448 IRS 2, L1448 IRS 3, and L1157, obtained between the λ = 1.3 mm and 2.7 mm continua, using the Combined Array for Research in Millimeter-wave Astronomy (CARMA). The unprecedented compact configuration and image fidelity of CARMA allow a better detection of the dust continuum emission from Class 0 sources, with a less serious missing flux problem normally associated with interferometry. Through visibility-modeling at both λ = 1.3 mm and 2.7 mm simultaneously, as well as image-and visibility-comparison, we show that β of the three Class 0 sources are around or smaller than 1, indicating that dust grains have already significantly grown at the Class 0 stage. In addition, we find a radial dependence of β, which implies faster grain growth in the denser central regions and/or dust segregation. Density distributions of the Class 0 sources are also addressed by visibility-modeling. 4 Dust "emissivity" has also been used in literatures from the viewpoint of dust thermal "emission".5 Recently 8 elements of 3.5 m antennas (the Sunyaev-Zel ′ dovich Array) have been merged as well.