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We report on seven nights of optical observation taken over a two-week period, and the resultant analysis of the intermediate-frequency peaked BL Lac object (IBL), BL Lac itself, at redshift z = 0.069. The microvariable behavior can be confirmed over the course of minutes for each night. A relativistic beaming model was used in our analysis, to infer changes to the line of sight angles for the motion of the different relativistic components. This model has very few free parameters. The light curves we generated show both high and moderate frequency cadence to the variable behavior of BL Lac itself, in addition to the well documented long-term variability.

We have measured Johnson BV and Cousins RI magnitudes for comparison stars near five TeV blazars. We compare our values with published values, spanning 25 years in some cases, to identify those stars that are most likely proven stable. To avoid zero-point offsets mimicking long-term variability, we based our analysis on the standard deviation between measurements after a mean offset between data sets was removed. We found most stars to be stable at the 0.04 magnitude level. We confirm two stars as variable and identify two others as possibly being variable. In each of the five fields there are at least two stars, and typically many more, that show no evidence of variability.

A study of the photometric accuracy of deconvolved astronomical images was undertaken by processing two simulated images with several well-known algorithms. The simulations consisted of an image of a simple star field and an image of an active galactic nucleus (AGN). Each image was mathematically convolved with a known PSF and then deconvolved to recover the original image. Measurements and comparisons were made before and after the deconvolution to check for photometric accuracy. The best result for the star field was obtained with the multiscale Richardson-Lucy algorithm. When measuring the differential photometry of the nucleus of the AGN between different frames, leaving the image in its convolved state gave a closer variability result to the original than any deconvolution method.

We examine the issues surrounding an IR slitless prism survey for galaxies with highly redshifted Hα to see if some of the next generation of IR instruments should have the capability to conduct such surveys. We model the galaxy and star surface density as a function of J, H, and K magnitudes to estimate field crowding with depth. Using data from the Subaru 8.2 m telescope and Infrared Camera and Spectrograph detector as a benchmark, we estimate the number of detectable galaxies as a function of telescope aperture size, object magnitude, and line strength. We find that while crowding need not be a major problem, it is still difficult for even a large telescope to obtain a useful emission-line galaxy sample in the J, H, or K bands primarily because of the high IR background and the faintness of the galaxies with Hα in these bands.

We examine the population statistics for two samples of galaxies in the direction of the Perseus supercluster. One sample, with N = 258 galaxies having MB ≤ -19.52 + 5 log(h) and vh ≤ 8000 km s-1, is complete for those galaxies within the boundaries of our survey region that have apparent magnitudes mp ≤ 15.0 in the Zwicky catalog. A more restrictive sample with N = 177 galaxies having MB ≤ -20.00 + 5 log(h) (with the same redshift range) is complete in both luminosity and volume. We derive the statistics for the relative incidence of galaxies in the following spectroscopic classes: (1) absorption line only, (2) collisionally-excited emission lines only, (3) nuclear H II region, (4) starburst, (5) LINER, and (6) Seyfert 1.8–2.

Using new redshift data reported in Gregory et al., we examine the structure of the Perseus supercluster. We discuss in detail three filaments lying in the plane of the sky on the western end of the supercluster that are distinct from each other in redshift and/or position. Additionally, radially directed filaments are found, and it appears that all of the filaments in the region are connected. We speculate that an important feature of filamentary structures may be the fact that many, if not all of them, connect in such a way as to form complete loops or rings. Underdense regions that border our filaments may not be very representative of the now classical cosmic void, in that their structures are not predominantly spheroidal.

We present new optical spectroscopic data for 347 galaxies in the region of the Perseus supercluster. The new data were obtained using the Steward Observatory 2.3 m telescope and cover the whole optical window. Included are redshifts (for 345 objects), absorption-line equivalent widths, a continuum index measuring the 4000 A break, and emission-line flux ratios. After 11 objects are rejected for being too faint and redshifts for 26 objects are added from the literature, we arrive at a complete sample of 361 galaxies. The distribution of redshifts for the whole sample is examined, and we show the relationship of the continuum index to morphology.

Using long-slit spectra centered in wavelength about Hα, we have obtained a velocity map of a 20'' × 140'' east-west box centered on the nuclear region of M101. The velocity resolution is 2.5 km s-1, and the spatial resolution is approximately 1'' east-west and variable (3''–4'' on average) north-south. We have also obtained temperature, density, and shock maps of the same region using the [N II] λ6548, [N II] λ6583, Hα, [S II] λ6717, and [S II] λ6731 lines. The temperatures range from 4100 to 14,100 K, with an intensity-averaged temperature of 6200 K. The densities range from 6.6 to 36,600 cm-3, with an intensity-averaged density of 800 cm-3. Regions northeast and southwest of the nucleus have [N II] λ6583/Hα ratios 0.56 and [S II] λλ(6717 + 6731)/Hα ratios ≥0.4, which are indicative of shock-heated or power-law photoionized gas. The gas in an S-shaped region passing through the nucleus has [N II] λ6583/Hα ratios 0.56 and [S II] λλ(6717 + 6731)/Hα ratios of ≈0.1, which is representative of gas in H II regions. The velocity data are consistent with gas infalling toward the nucleus as part of streaming motions traveling west to east on the north side of the nucleus and east to west on the south side of the nucleus. However, there appears to be a local instability in which the motion southwest of the nucleus is moving west to east, creating a collision of the two opposing gas motions in a region of relatively high density and temperature. A blue arc emanating from an unresolved source on or near the nucleus shows evidence of collision in this same high-density, high-temperature region. Our data support a previous conclusion that M101 may be considered an intermediate galaxy with respect to activity, possibly in transition between a normal nucleus and a more active stage.

The presence or absence of dwarf galaxies with Mr' > -14 in low-density volumes correlates with dark matter halos and how they affect galaxy formation. We are conducting a redshifted Hα imaging survey for dwarf galaxies with Mr' > -13 in the heart of the well-defined voids FN2 and FN8 using the KPNO 4m Mayall telescope and Mosaic Imager. These data have furnished over 600 strong candidates in a four square degree area. Follow-up spectra finding none of these candidates to be within the void volumes will constrain the dwarf population there to be 2 to 8% of the cosmic mean. Conversely, finding even one Hα dwarf in the void heart will challenge several otherwise successful theories of large-scale structure formation.

The KPNO International Spectroscopic Survey (KISS) is an objective-prism survey designed to detect extragalactic emission-line objects. It combines many of the features of previous slitless spectroscopic surveys with the advantages of modern CCD detectors, and is the first purely digital objective-prism survey for emission-line galaxies (ELGs). Here we present the third list of ELG candidates selected from our red spectral data, which cover the wavelength range 6400 to 7200 A. In most cases, the detected emission line is H-alpha. The current survey list covers the region of the NOAO Deep Wide-Field Survey (NDWFS). This survey covers two fields; the first is 3 x 3 degrees square and located at RA = 14h 30m, DEC = 34.5 deg (B1950), the second is 2.3 x 4.0 degrees and centered at RA = 2h 7.5m, DEC = -4.75 deg. A total area of 19.65 deg^2 is covered by the KISS data. A total of 261 candidate emission-line objects have been selected for inclusion in the survey list (13.3 per deg^2). We tabulate accurate coordinates and photometry for each source, as well as estimates of the redshift, emission-line flux and line equivalent width based on measurements of the digital objective-prism spectra. The properties of the KISS ELGs are examined using the available observational data. When combined with the wealth of multi-wavelength data already available for the NDWFS fields, the current list of KISS ELGs should provide a valuable tool for studying star-formation and nuclear activity in galaxies in the local universe., Comment: 18 pages, including 10 figures and 4 tables. Accepted for publication in the December, 2005 AJ

The KPNO International Spectroscopic Survey (KISS) is an objective-prism survey for extragalactic emission-line objects. It combines many of the features of previous slitless spectroscopic surveys with the advantages of modern CCD detectors, and is the first purely digital objective-prism survey for emission-line galaxies. Here we present the first list of emission-line galaxy candidates selected from our blue spectral data, which cover the wavelength range 4800 -- 5500 A. In most cases, the detected emission line is [O III]5007. The current survey list covers a one-degree-wide strip located at Dec = 29 deg 30' (B1950.0) and spanning the right ascension range 8h 30m to 17h 0m. An area of 116.6 deg^2 is covered. A total of 223 candidate emission-line objects have been selected for inclusion in the survey list (1.91 deg^-2). We tabulate accurate coordinates and photometry for each source, as well as estimates of the redshift, emission-line flux, and equivalent width based on measurements of the digital objective-prism spectra. The median apparent magnitude of the sample is B = 18.2, and galaxies with redshifts approaching z = 0.1 are detected. The properties of the KISS emission-line galaxies are examined using the available observational data, and compared to previous surveys carried out with photographic plates as well as with the H-alpha-selected portion of KISS., 21 pages, with 12 figures and 3 tables. Accepted for publication in the March, 2002 AJ. Full versions of the catalog tables available from KISS website (http://www.astro.wesleyan.edu/~slaz/research/kiss/kisspubs.html)

The paper reports on VLA 20 cm observations of an extensive sample of galaxies in 139 poor groups. These groups, composed of galaxies down to the limit of the Zwicky et al. (CGCG) catalog, were chosen using a percolation algorithm set at a high surface-density threshold. Approximately 50 percent of the groups have measured redshifts. These groups were surveyed using a snapshot mode of the VLA with a resolution of about 13 arcsec. Analysis of the resulting radio and optical properties reveals that the presence of a nearby companion galaxy has an important role in generating radio emission in a galaxy. CCD observations of two radio-loud, disturbed galaxies with companions are presented and are used to discuss models of radio-source production. Nine tailed radio galaxies are found in the poor groups, which is much more than had been expected from previous work on rich clusters and from theoretical models. The paper discusses previous statistical biases and proposes a method for bending head-tail sources in poor groups. From the confinement of extended radio features associated with tailed sources, the presence of a substantial intracluster medium that should radiate significantly at soft-X-ray energies is predicted. 56 references.

The spatial distribution of emission-line galaxies (ELGs) relative to normal galaxies in several areas of the sky is discussed. Current evidence supports the notion that ELGs trace a low-density population in all the surveyed areas with the possible exception of the CfA 'Slice of the Universe' survey. Based on this and other survey data in the north galactic cap, it is suggested that the ELGs inside the Bootes void may actually define the edge of a totally empty volume within an underdense distribution of normal galaxies.

Les deplacements vers le rouge de 3 nouvelles galaxies montrent qu'elles sont a l'interieur du vide. Le nombre des galaxies dans le vide de Bootes est donc actuellement de huit. Leur diametre est voisin de 10 h −1 et leur morphologie irreguliere

VLA 20-cm continuum observations of eight emission-line galaxies in the Bootes void are presented. Five of the eight galaxies have weak (0.7-4.4 mJy) and compact radio emission. The radio and optical properties of these galaxies are compared with those of Seyferts and starburst galaxies in an effort to understand the origin and nature of galaxy activity in such an underdense region. It is concluded that the radio and optical properties of these galaxies are remarkably similar to those of active galaxies in richer cluster environments. 22 references.