Robert B. Loren

Cobwebs of Ophiuchus. I. Strands of (C-13)O - the mass distribution

A 4.5 deg x 6.5 deg area of the Rho Ophiuchus molecular complex has been mapped in J = 1-0 (C-13)O with a 2.4 arcmin beam. The spatial distribution of (C-13)O, the distribution of clumps according to size, mass, density, and kinetic temperature are described. The distribution of material in the cloud is compared with the magnetic field distribution and with a shocked cloud model. Evidence supporting the role of shock in the cloud is found in the cloud morphology. 48 references.

Cold DCO(+) cores and protostars in the warm Rho Ophiuchi cloud

The decrease of DCO(+) abundance with elevation of a clouds T(K) is used to identify a cluster of a dozen of the coldest, youngest dense cores embedded in the L1688, L1689, and L1709 clouds in the Rho Ophiuchi complex. Most of the cores in L1688 have T(K) = 12-14 K, about half that indicated by CO throughout L1688. Ten cold dust shell, protostellar IR point sources are embedded within these cores. Not every DCO(+) core contains a protostar, but every protostar with a steep spectral index is found in close association with DCO(+) emission. The rotational axes for all of the Rho Oph DCO(+) cores are parallel to the ambient magnetic field, regardless of whether a core is elongated parallel or perpendicular to the direction of the magnetic field. In the Taurus complex the ambient magnetic field is perpendicular to the axes of the major filaments and will inhibit further concentration of material. 53 refs.

Cobwebs of Ophiuchus. II. (C-13)O filament kinematics

The molecular kinematics in the Rho Ophiuchi complex are examined. Streaming motions in the form of V(LSR) gradients along filament axes, as predicted for a shocked cloud model, are found only in a short warm filament associated with L1689N, but are not found in the three longest filaments. They have, instead, either approximately uniform V(LSR) or abrupt jumps in V(LSR) between adjacent lumps. A small fraction of clumps are rotating. About evenly divided between senses of rotation, most of these clumps share a common axial alignment paralleling the ambient magnetic field. Within most individual clumps the V(LRSR) is constant within 0.1-0.2 km/s. There is no correlation between the turbulent velocity dispersion in a clump and the clump size or mass. A distinction in turbulent sigma is found between clumps with embedded stars and those without. 37 references.

L1689N - misalignment between a bipolar outflow and a magnetic field

High-resolution radio observations of L1689N, a dense molecular core in the Rho Oph molecular complex, are reported. Transitions of (C-12)O, (C-13)O, C(O-18), DCO(+), H(C-13)O(+), SO, and NH3 were mapped during 1984-1986 using the 4.9-m antenna at the Millimeter Wave Observatory, the 43-m antenna at NRAO Green Bank, the VLA, and the 12-m NRAO telescope at KPNO; the results are presented graphically and characterized in detail. Most of the dense material in L1689N is found to be contained in a gravitationally bound cold clump with mass about 20 solar masses and maximum density n(H2) = about 10 to the 6th/cu cm. A warmed clump, lying 0.07 pc west of the cold clump and surrounding IRAS 16293-422, is found to contain a bipolar mass-outflow region with crossing time about 9000 yr. 33 references.

High-velocity HCO/sup +/ in cepheus A: Ionization levels in high-density clumps within a molecular flow

High-velocity (FWZP approx.44 km s/sup -1/) HCO/sup +/ wings have been detected in both the J = 1-0 and J = 3-2 lines toward Cep A. Modeling the intensity ratio in the wings of these two lines indicates that this emission arises in high-density (10/sup 6/ cm/sup -3/) clumps within a high-velocity outflow. The highest velocity HCO/sup +/ emission is confined to an unresolved region at the location of the IR cluster and H/sub 2/O masers. At intermediate velocities the HCO/sup +/ emission is spatially extended, with redshifted and blueshifted lobes on opposite sides of the dense core, a bipolar pattern similar to that seen in CO emission wings. Both the HCO/sup +/ abundance (3-6 x 10/sup -9/) and the electron abundance (<10/sup -8/) in the high-velocity flow are similar to more quiescent cold molecular clouds. Such low ionization levels with the molecular flow are a condition needed for the magnetic precursor model of shock structure (Draine 1980).

CO AND SHOCKS RELATED TO THE EVOLUTION OF THE ORION-NEBULA

Henry Draper’s first photograph of the Orion Nebula was a milestone in the observational study of star formation and the interstellar medium. Modern astronomical techniques produce images that contain information complementary to that contained in Draper’s optical photograph. In this paper, we discuss the features of the molecular emission from the giant molecular cloud that is associated with the nebula. Although it is invisible in optical photographs of the region, the molecular gas has played an important role in the evolution of the visible features. The processes that produce the optical features have, in turn, affected the structure and temperature of the molecular gas. Thus, we may study these properties via millimeter line observations to learn about the sequence of events that produced the present appearance of the nebula. Specifically, the study of the shocked regions of molecular gas that resulr from the expansion of the H I I region allows us to test current models of its evolution. Our interest in the relationship between an evolving H II region and a molecular cloud goes beyond the structure of the optical nebula. We would also like to know what this relationship has been in the past and what it is likely to be in the future. Since we believe that the Trapezium stars were formed from molecular gas that was initially part of the giant molecular cloud complex, we may also approach its study with an eye towards deducing the physical conditions under which stars form. This view is supported by recent discussions of the possible roles of 0 and B stars in the formation of new stars. Elmegreen and Lada suggest that the expansion of an evolving H II region provides the impetus for the formation of new stars in the shocked boundary layer of the molecular cloud.’ Thus, the study of the shocked regions could provide important

Submillimeter molecular spectroscopy with the Texas millimeter wave observatory radio telescope

A large number of previously unreported molecular transitions have been detected in the submillimeter wavelength band toward OMC-1 and M17 SW using the Texas 4.9 m radio antenna. The emission components in OMC-1 that come from the unresolved plateau and hot core regions are stronger in these higher energy transitions than in the lower-energy, lower-frequency lines. Intense, probably thermalized high J SiO lines require a very hot core if they arise in a region the same size as that mapped in J = 2-1 SiO by interferometer measurements. Despite the high energy levels of the submillimeter lines of CN and CCH, there is no broad emission component evident, consistent with their greatly reduced abundance due to removal by chemical reactions. 33 references.

Asymmetric Broad HCO+ Line Wings in Cores of Molecular Clouds

High resolution observations of HCO+ in the cores of the W3, NGC 2071 and Cep MC-1 molecular clouds reveal asymmetric line wings extending over velocity ranges of 20, 35 and 55 km s-1, respectively. Red and blue wings of the profiles are enhanced on opposite sides of infrared objects embedded in the cores of NGC 2071 and Cep MC-1. The lines attain their maximum breadths at the positions of these infrared objects. These facts imply that the infrared objects are the energy sources for the high velocity gas. Rotation cannot account for all observed features of the profiles. A model incorporating outflow centered on the infrared objects is suggested. W3, on the other hand, is more complex and evidence is presented which shows the presence of two molecular clouds in the core, one centered near IRS 5 and the other near IRS 4, the latter exhibiting a blue-shifted wing.