Mark H. Heyer

BOK globules and small molecular clouds - Deep IRAS photometry and (C-12)O spectroscopy

The entire sample of small molecular clouds cataloged by Clemens and Barvainis (1988) has been probed using deep, coadded IRAS survey data analysis and (C-12)O spectroscopy. The far-IR colors are similar to those found for other amorphous Galactic constituents. The mean 12.25 micron color was 0.01, the mean 25/60 micron color was 0.68, and the mean 60/100 micron color was 0.70. The bulk of the dust mass was colder than 30 K. A very strong anticorrelation was found between dust optical depth and 60/100 micron color temperature. The mean far-IR luminosity of the sample is about 6.4 solar luminosities, the mean cloud mass is about 11 solar, the radius is around 0.35 pc, and the density is around 1000 H2/cu cm. Upper and lower limits for the number of these clouds in the Galaxy are 160,000 and 650,000. A total Galactic mass in Bok globules of about 3.5 million solar and a total luminosity of about two million solar is found. 45 refs.

New optical features in L1551 and HH30

During a survey for faint H-alpha emission-line stars in Tau, a pair of on-line, off-line frames of the L1551-HH30-HL Tau region was obtained with an 800 x 800 CCD detector mounted on the Burrell Schmidt telescope at KPNO. Potentially important optical features unnoticed in most previous studies are discussed. In the L1551 core region there is a cluster of HH objects W of HH28 which on the average are larger and more diffuse than those which are closer to the source IRS5. In the SW and NE corners of the 20-arcmin field, new outlying HH objects are found. The evidence favors association with the second FIR source to the NE of IRS5 (L1551NE).

Newborn stars and stellar winds in Barnard 228

Imaging and spectroscopic observations of premain-sequence stars in the B228 molecular cloud have identified three sites of extended, shock-excited nebulosity. A highly collimated, blueshifted jet is associated with the T Tauri star Sz68 (CoD -33:10685 deg). A candidate Herbig-Haro object is found near Sz68 and the T Tauri star Sz69. A third region of shock-excited nebulosity is identified near the embedded newborn star IRAS 15398-3359. IR excesses observed toward these stellar sources may imply a relationship between outflow activity and the presence of a circumstellar disk. Only one of the two outflow sources with well-defined orientations is aligned with the large-scale, magnetic-field geometry of the cloud in contrast to the global alignment of outflows in the Taurus cloud complex. Data for three previously unidentified emission-line stars are presented. A faint 18th magnitude dMe star located 48 arcsecs west of Sz68 is identified.

Th28 (Krautter's star) and its string of Herbig-Haro objects

The authors have obtained an intermediate-resolution spectrum of the unusual emission-line star Th28 and its accompanying family of Herbig-Haro (HH) objects. They note a new HH object 87arcsecSE of the star along the axis defined by the other emission regions and point out that the more distant HH object, HH78, lies in this same direction and may also have been powered by Th28. Based on absorption and emission-line measurements the authors determine for the star a heliocentric velocity of +5 km s-1. They also present a low-resolution spectrum and infrared photometry for the star alone. A variety of emission lines are identified. The star has a moderate infrared excess between 1 and 3.5 μm showing the likely presence of heated dust in its immediate surroundings.

Young stars of low mass in the Gum nebula

Observations are presented for four recently formed stars in the vicinity of the Gum nebula which are heavily obscured by surrounding dust and are associated with small reflection nebulae. HH46 is the only currently active star of the sample, and it is found to have a spectral type in the range of late G-early K, with superimposed emission lines of H-alpha, Ca II, Fe I, Fe II, and weak He I at near zero velocities. It is suggested that the observed scenario of low-mass stars in an older massive star environment may be analogous to the circumstances surrounding the birth of the sun.

HH55 and its energy source

Imaging and spectroscopic observations of HH55 in the Lupus molecular cloud are presented. Cohen and Schwartz (1987) have shown that HH55 is apparently not excited by the nearby T Tau star RU Lup as once thought but rather by the coincident FIR point source 15533 - 3742 extracted from IRAS coadded images. The optical counterpart of this IR source is identified as an active, relatively unobscured M-dwarf star. The forbidden emission lines observed in the stellar spectrum exhibit slight asymmetries to blueshifted velocities. Deconvolution of the emission lines reveals a weak moderate-velocity (-100 km/sec) wind component and a stronger emission component whose velocity is very close to that of the star.