Publications of the Astronomical Society of the Pacific

Hollweg, J. V.

doi: 10.1086/129646pmid: N/A

Review of recent theoretical and observational work attempting to explain the origin and nonlinear properties of interplanetary hydromagnetic waves and the role played by these waves in modifying the thermal and dynamic characteristics of the solar wind. Attention is restricted to propagating hydromagnetic waves which are intrinsic to the solar wind itself. An initial straightforward analysis of small-amplitude hydromagnetic waves serves as a guide for interpreting the data and as a reference point for examining the more complex nonlinear phenomena. Representative data illustrate the appearance of the various hydromagnetic wave modes in the solar wind. The various effects which the waves may have on the solar wind itself are finally discussed.

Worden, S. P.

doi: 10.1086/129647pmid: N/A

The dMe stars are late-type main-sequence objects which exhibit characteristics that can be explained as the result of solar-type surface magnetic activity. The battery mechanism of Biermann (1950) is used to explain the origin of the magnetic fields responsible for the surface activity. Magnetic fields 10-100 times the strength of solar magnetic fields can be produced in this manner. Such strong fields are consistent with the observed dMe properties and should be directly detectable.

doi: 10.1086/129648pmid: N/A

OF PAPERS PRESENTED AT THE BISHOP, CALIFORNIA, MEETING OF THE ASThONOMICAL SOCIETY OF THE PACIFIC, 11-13 JUNE 1974

Herbig, G. H.

doi: 10.1086/129651pmid: N/A

The small dark globules seen against the nebulosity in the northwest quadrant of NGC 2237-2244 are shown on a 120-inch direct photograph to have an elongated, tear-drop form with the symmetry axes and sharper edges directed toward the central star cluster. This orientation is shared by the well-known elephant trunk structure, which in general lies farther from the center than these isolated dark spots. Examples of globules still connected with large dark masses by dust filaments are also present. It is suggested that these globules represent a late stage in the pinching-off and dissipation of elephant trunks as the central cavity of the H II region expands into the peripheral dust clouds, and that these globules are not protostars. It is estimated that the age of a typical small isolated globule in this region of NGC 2237-2244 is of the order of 10,000 years.

Osterbrock, D. E.

doi: 10.1086/129652pmid: N/A

Coude spectrograms of NGC 7027 were obtained at sufficiently high dispersion to resolve the H alpha, H beta, and H gamma line profiles. Comparison of the blue and red sides shows no differences that can be attributed to internal extinction by dust within this planetary nebula.

Smith, H.

doi: 10.1086/129653pmid: N/A

The mass of the Coma cluster of galaxies is estimated by comparing it to calculated N-bedy systems and applying the virial theorem. The mass estimated by comparison with systems with two mass components is 1.4 X 1015 9)'to. Key words: clusters of galaxies - galaxy cluster mass

Balick, B.; Gammon, R. H.; Hjellming, R. M.

doi: 10.1086/129654pmid: N/A

The Orion nebula is the best studied of all H II regions. The experimental data for this nebula are reviewed, and interpretive models of the structure of both the nebula and its environs are developed. The H II region is composed of an inner 3-min core surrounding the exciting star theta 1 C which is partially imbedded on the near side of a massive neutral complex. A network of strong flows results that resupplies high-density ionized gas to the core region. Gas in the core then freely expands, where possible, primarily into the foreground, south, and west. Details of this model are compared with optical, radio, and infrared observations of the ionized, neutral atomic, and molecular gas in the Orion nebula. The nature of the neutral complex is also discussed.

Kaler, J. B.; Aller, L. H.

doi: 10.1086/129655pmid: N/A

We have measured radial velocities along the major axis of NGC 2440, which show that the outer knots do not lie on a line with the inner condensations. The observations suggest that the bright inner nebula is expanding faster than the faint outer halo, and that these two parts of the nebula were produced independently of one another. The nebula shows an extreme degree of stratification. Key words: planetary nebulae

Beaver, E. A.; Harms, R. J.; Tifft, W. G.; Sargent, T. A.

doi: 10.1086/129656pmid: N/A

Surface brightness and color data are derived for two points in the bridge and tail structure of Arp 295. The best observed point has a surface brightness in V of 25.9 magnitudes per square arc second and (B-V) = +1.00 m. A point on the tail is brighter with the same color.

Hodge, Paul W.

doi: 10.1086/129657pmid: N/A

The dwarf irregular galaxy CR8 has a radial velocity, determined from optical and radio observations, of + 227 ::::: 5 km sec-1. It contains two well-resolved Hii regions of low surface brightuess. Its distance is estimated from six different but highly uncertain arguments, from which it is concluded that probably the best estimate at present is 1.0 ::::: 0.5 Mpc. This places it just inside the local group and implies that its size is 300 pc and its absolute magnitude is Mv = -10.6. Key words: galaxy - radial velocity