Naomi A. Ridge

TURBULENCE DRIVEN BY OUTFLOW-BLOWN CAVITIES IN THE MOLECULAR CLOUD OF NGC 1333

Outflows from young stellar objects (YSOs) have been identified as a possible source of turbulence in molecular clouds. To investigate the relationship between outflows, cloud dynamics, and turbulence, we compare the kinematics of the molecular gas associated with NGC 1333, traced in 13CO (1-0), with the distribution of YSOs within. We find a velocity dispersion of ~1-1.6 km s-1 in 13CO that does not significantly vary across the cloud and is uncorrelated with the number of nearby young stellar outflows identified from optical and submillimeter observations. However, from velocity channel maps we identify about 20 depressions in the 13CO intensity of scales 0.1-0.2 pc and velocity widths 1-3 km s-1. The depressions exhibit limb-brightened rims in both individual velocity channel maps and position-velocity diagrams, suggesting that they are slowly expanding cavities. We interpret these depressions to be remnants of past YSO outflow activity: if these cavities are presently empty, they would fill in on timescales of ~106 yr. This can exceed the lifetime of a YSO outflow phase or the transit time of the central star through the cavity, explaining the absence of any clear correlation between the cavities and YSO outflows. We find that the momentum and energy deposition associated with the expansion of the cavities is sufficient to power the turbulence in the cloud. In this way we conclude that the cavities are an important intermediate step between the conversion of YSO outflow energy and momentum into cloud turbulent motions.

Kinematics of NGC 2264 : Signs of cluster formation

We present results from 1078 high-resolution spectra of 990 stars in the young open cluster NGC 2264, obtained with the Hectochelle multiobject echelle spectrograph on the 6.5 m MMT. We confirm 471 stars as members on the basis of their radial velocity and/or Hα emission. The radial velocity distribution of cluster members is non-Gaussian, with a dispersion of σ ≈ 3.5 km s-1. We find a substantial north-south velocity gradient and spatially coherent structure in the radial velocity distribution, similar to that seen in the molecular gas in the region. Our results suggest that there are at least three distinguishable subclusters in NGC 2264, correlated with similar structure seen in 13CO emission, which is likely to be a remnant of initial structure in this very young cluster. We propose that this substructure is the result of gravitational amplification of initial inhomogeneities during overall collapse to a filamentary distribution of gas and stars, as found in simulations by Burkert & Hartmann (2004).

The complete nature of the warm dust shell in perseus

The Perseus molecular cloud complex is a &30pc long chain of molecular clouds most well-known for the two star-forming clusters NGC1333 and IC348 and the well-studied outflow source in B5. However, when studied at mid- to far-infrared wavelengths the region is dominated by a ∼10pc diameter shell of warm dust, likely generated by an Hii region caused by the early B-star HD278942. Using a revised calibration technique the COMPLETE team has produced high-sensitivity temperature and column-density maps of the Perseus region from IRAS Sky Survey Atlas (ISSA) 60 and 100µm data. In this paper, we combine the ISSA based dust-emission maps with other observations collected

Dynamical and chemical properties of the "starless" core L1014

Spitzer Space Telescope observations of a point-like source, L1014-IRS, close to the dust peak of the low-mass dense core L1014, have raised questions about its starless nature. These show the presence of an object with colors expected for an embedded protostar with the implication that L1014-IRS would be the lowest luminosity isolated protostar known, and an ideal target with which to test star formation theories at the low mass end. In order to study its molecular content and to search for the presence of a molecular outflow, we mapped L1014 in at least one transition of 12 CO, N2H + ,H CO + , CS, and of their isotopologues 13 CO, C 18 O, C 17 O, N2D + ,a nd H 13 CO + , using the Five College Radio Astronomy Observatory (FCRAO), the IRAM 30 m antenna, and the Caltech Submillimeter Observatory (CSO). The data show physical and chemical properties in L1014 typical of moderately evolved dense cores: i.e. H2 central density of a few 10 5 molecules cm −3 , estimated mass of ∼2 M� , CO integrated depletion factor less than 10, N(N2H + ) � 6 × 10 12 cm −2 , N(N2D + )/N(N2H + ) equal to 10%, and relatively broad N2H + and N2D + lines (0.35 km s −1 ). Infall signatures and significant velocity shifts between optically thick and optically thin tracers are not observed in the line profiles. No classical signatures of molecular outflow are found in the 12 CO and 13 CO FCRAO observations. In particular, no high velocity wings are found, and no well-defined blue-red lobes of 12 CO emission are seen in the channel maps. Sensitive, higher resolution observations will clarify the presence of a molecular outflow on a smaller scale than that probed by our observations.