Christopher D. Impey

Low surface brightness galaxies in the local universe .1. The catalog

Data are presented for 693 galaxies identified in a large new survey for low surface brightness galaxies in the nearby universe (z less than or similar to 0.1). The survey covers 786 square degrees centered on the equator, and it extends significantly the surface brightness range of galaxy surveys in which there are a substantial number of galaxies with redshifts. The data are derived from the Automated Plate Measuring machine scans of survey plates from the UK Schmidt Telescope and from follow-up observations at radio and optical wavelengths. Accurate positions, total B magnitudes, surface brightness parameters, and angular sizes are tabulated for each galaxy. Radial velocities, optical luminosities, and neutral hydrogen masses are listed for a subset of the sample. Finding charts are also presented for those objects having a large enough angular size that the scans from survey plates provide some morphological information. The selection function and the luminosity function that can be derived from the survey are discussed in two companion papers.

Low surface brightness galaxies in the local universe .2. Selection effects and completeness of the automated plate measuring survey

We discuss the techniques employed for identifying low surface brightness galaxies for the Automated Plate Measuring (APM) survey. We present the method of calibrating the photometry performed from the APM scans and discuss the uncertainties associated with the calibrations. We also review the possible sources of incompleteness in the survey, and we present the results of a program of simulations to estimate the completeness as a function of galaxy parameters. Finally, we discuss the implications of the survey results and show, in particular, that the observed distribution of central surface brightnesses among all galaxies in one survey held is almost flat for mu(B)(0) > 23 mag arcsec-(2).

The Wasilewski sample of emission-line galaxies - Follow-up CCD imaging and spectroscopic and IRAS observations

The results of an extensive imaging and spectroscopic follow-up of the objective prism-selected emission line galaxy (ELG) sample of Wasilewski (1982) are presented. Fluxes at 12, 25, 60, and 100 microns were also obtained from the coadded IRAS survey data. ELGs found by objective prism surveys are found to be generally small and underluminous galaxies which usually have higher than average optical surface brightness. The Seyfert detection rate in objective prism surveys is roughly 10 percent and the ratio of the space densities of Seyfert 2 to Seyfert 1 galaxies is significantly larger than unity. Most of the galaxies selected by objective prism surveys are star-forming, late-type spirals which often show disturbed morphology. About 25 percent of the galaxies detected by the surveys are faint, high-excitation metal-poor compact H II regions. 62 refs.

The miniblazar in 3C 273

The compact core of 3C 273 has been studied for over two years using optical photometry and accurate polarimetry. A wealth of polarization behavior, including variable polarization, observed at a level of under 1 percent is described. The results indicate that 3C 273 harbors a weak continuum component having all the characteristic properties of blazars. It is predicted that other compact radio sources with low optical polarization will also be found to harbor miniblazars. The detection of variable polarization in 3C 273 strengthens the link between superluminal motion at radio wavelengths and blazar activity at optical wavelengths. 76 refs.

1E 1415.6+2557 - An X-ray-selected BL Lacertae object in a luminous galaxy

The identification of a fifth serendipitous Einstein source with a new BL Lac object in a very luminous galaxy is reported. The resolved component is well fitted by an exponential disk with scale length 18 kpc and absolute magnitude of roughly -24.2. A redshift of 0.237 is derived from stellar absorption features. No emission lines are seen in the 3200-9000 A wavelength range. Decomposition of the optical spectrum into a standard galaxy plus a power law yields a spectral index of 0.5 + or - 0.5, significantly flatter than in the average BL Lac object. Linear polarization of the nonstellar component is about 6 percent in the 4500-7000 A wavelength range. The X-ray flux in the 0.3-3.5 keV band is 1.16 x 10 to the -11th ergs/sq cm/s, corresponding to a luminosity of 3.5 x 10 to the 45th ergs/s . The radio flux density is 85.6 mJy at 20 cm and 54.5 mJy at 6 cm.