Charles T. Liu

Three-Dimensional Fabry-Perot Imaging Spectroscopy of the Crab Nebula, Cassiopeia A, and Nova GK Persei

A three-dimensional model of the [0 III] A5007 line-emitting gas in the Crab Nebula has been developed from imaging spectroscopy taken with the Goddard Fabry-Perot Imager mounted on the McGrawHill 1.3m telescope of Michigan-Dartmouth-MIT Observatory. Several interesting morphological features revealed in three-dimensional isophotal displays are discussed.

Luminosity Functions and Evolution of Blue Galaxies in a Deep Multicolor CCD Field Survey

A complete sample of 659 field galaxies with 17.0 < U ≤ 21.1, each with UBVR-I7500-I8600 photometry, has been selected from a deep field survey that covers 0.83 deg2 along six lines of sight. Each galaxys spectral type and redshift have been estimated using a multicolor photometric technique of Liu & Green. Total number counts of the galaxies in the U band give a count slope d(log N)/dM = 0.55 ± 0.05, consistent with previous studies. The 545 galaxies in the sample classified as spectral type Sbc or bluer are analyzed for signs of evolution with redshift and for unusual star formation histories. The U-band luminosity function of these blue galaxies at 0.02 < z < 0.15 has a steep α -1.85 down to M(B) -14. The luminosity functions at 0.15 ≤ z < 0.3 and 0.3 ≤ z ≤ 0.5 show significant evolution in M* and * at levels consistent with those found in the Canada-France and Autofib redshift surveys. A significant population of very blue (rest-frame U - B < -0.35) galaxies, with spectral energy distributions indicating strong starburst activity, is observed at z 0.3 but not at z < 0.3. This population is confirmed via spectroscopy of part of the sample. These may be galaxies temporarily brightened by global starbursts, which subsequently fade and redden at lower redshifts.

H-alpha imaging of galaxies in the Bootes void

We report H-alpha and continuum imaging of 12 galaxies in the Bootes void. The H-alpha emission in ten galaxies is due to star formation; one galaxy is probably a narrow emission line Active Galactic Nuclei (AGN), and one a Seyfert 1. Star formation rates range from 3-55 solar mass/yr, with the most active galaxies producing stars at almost three times the rate found in normal field disk systems. Eleven galaxies have strong H-alpha emission in the nucleus. The morphology of several of the galaxies is disturbed. There are at least five spirals, three of which are probably one-armed spirals, and three edge-on disk systems. Three galaxies not identifiable as spirals have H-alpha emission from regions outside the nuclear point source. 1510+4727, which has the highest rate of star formation in our sample, does not have the strong far-infrared emission expected from a galaxy experiencing significant star formation. The galaxies are quite luminous M(sub B) = -21 to -23 mag), and are not the type predicted to be found in voids.

Blood-borne donor mast cell precursors migrate to mast cell-rich brain regions in the adult mouse

Mast cells are hematopoietic immune cells located throughout the body, including within the brain. Reconstitution of mast cell deficient Kit(W-sh/W-sh) mice has proven valuable in determining peripheral mast cell function. Here we study the brain mast cell population using a novel method of blood transfusion for reconstitution. We show that blood transfusion results in mast cells of donor origin in the WT mouse, including in the brain where they are restricted to regions bearing host mast cells. In contrast, in Kit(W-sh/W-sh) mice, transfusion results in mast cells in the pinna of the ear, but not the brain.

EXTRAORDINARY LINE-EMITTING KNOTS IN THE CRAB NEBULA

Extraordinary, semistellar, line-emitting knots are apparent in images of the Crab Nebula which were obtained with the Goddard Fabry-Perot imager at the Michigan-Dartmouth-MIT Observatory. The knots are most prominent for (O III) lambda 5007 emission through a 5.3 A (Full Width at Half Maximum (FWHM)) bandpass centered at 5015.3 A, with representative fluxes of roughly 10(exp -14) ergs/sq cm. They are aligned in arcs, seven to the north and four to the south, from the pulsar. The northern group appears to be in a bounded corridor through the filamentary structure. Measurements over a 2 year baseline yield proper motions of order 0.1 sec/yr, corresponding to transverse velocities of order 900 km/s for a distance of 1830 pc. The knots are characterized by remarkably strong (Ar III) emission, possibly indicating high argon abundances, high gas temperatures, or anomalous physical processes.