A current issue in the study of planetary nebulae with close binary central stars (CSs) is the extent to which the binaries affect the shaping of the nebulae. Recent studies have begun to show a high coincidence rate between nebulae with large-scale axial or point symmetries and close binary stars. In addition, combined binary-star and spatiokinematic modeling of the nebulae have demonstrated that all of the systems studied to date appear to have their central binary axis aligned with the primary axis of the nebula. Here we add two more systems to the list, the CSs and nebulae of NGC 6337 and Sp 1. We show both systems to be low inclination, with their binary axis nearly aligned with our line of sight. Their inclinations match published values for the inclinations of their surrounding nebulae. Including these two systems with the existing sample statistically demonstrates a direct link between the central binary and the nebular morphology. In addition to the systems' inclinations we give ranges for other orbital parameters from binary modeling, including updated orbital periods for the binary CSs of NGC 6337 and Sp 1.
We present new spectroscopic and BVRI photometric observations of the double-lined eclipsing binary AV Del (period=3.85days) conducted over six observing seasons.
Using a CCD detector, BVRI photometry has been carried out in the vicinity of nine Lynds dark nebulae. In conjunction with spectroscopic data which could be obtained at a later stage, the data listed herein could be used for possible distance determinations of the nine nebulae.
New photometric and spectroscopic observations of galaxies in the directions of three distant clusters are presented as part of our ongoing high-redshift cluster survey. The clusters are Cl 1324+3011 at z=0.76, Cl 1604+4304 at z=0.90, and Cl 1604+4321 at z=0.92. We have spectroscopically confirmed cluster membership for 2040 galaxies in each system and have also obtained spectra for over 280 field galaxies spanning the range 0<z<2.5.
We explored the regions within a radius of 25 arcsec around 473 nearby, low-metallicity G- to M-type stars using (VR)I optical filters and small-aperture telescopes. About 10% of the sample was searched up to angular separations of 90 arcsec. We applied photometric and astrometric techniques to detect true physical companions to the targets. The great majority of the sample stars was drawn from the Carney-Latham surveys; their metallicities range from roughly solar to [Fe/H]=-3.5dex. Our I-band photometric survey detected objects that are between 0 and 5mag fainter (completeness) than the target stars; the maximum dynamical range of our exploration is 9mag.
We present high-quality BVRI photometric data in the field of globular cluster NGC6496 obtained with the SOAR Telescope Adaptive Module (SAM). Our observations were collected as part of the ongoing SAM commissioning. The distance modulus and cluster color excess as found from the red clump are (m-M)_V_=15.71+/-0.02mag and E(V-I)=0.28+/-0.02mag. An age of 10.5+/-0.5Gyr is determined from the difference in magnitude between the red clump and the subgiant branch. These parameters are in excellent agreement with the values derived from isochrone fitting. From the color-magnitude diagram we find a metallicity of [Fe/H]=-0.65dex and hence support a disk classification for NGC 6496. The complete BVRI data set for NGC6469 is made available in the electronic edition of the Journal.
New BVRI broadband photometry and astrometry are presented for the globular cluster NGC 4147, based upon measurements derived from 524 ground-based CCD images mostly either donated by colleagues or retrieved from public archives. We have also reanalyzed five exposures of the cluster obtained with WFPC2 on the Hubble Space Telescope in the F439W and F555W (B and V) filters.
The results from work done to extend the Johnson-Cousins BVRI photometric standard sequence to faint levels of V~21mag in compact fields is presented. Such calibration and extension of sequences is necessary to fill a calibration gap if reliable photometry from modest aperture telescopes in space (e.g., the Hubble Space Telescope) or terrestrial telescopes with apertures exceeding 4m is to be done. Sequences like the ones presented here, which cover a large range in brightness as well as color, will allow photometric calibration to be done efficiently and will also make such work less prone to systematic sources of error. Photometry of stars in approximately 10'x10' fields around three globular clusters (NGC 2419, Pal 4, and Pal 14) are presented from data acquired over several photometric nights. In each field, several stars are measured in B, V, R, and I passbands, with standard errors in the mean less than 0.015mag from random errors, to levels fainter than V=21mag.
We present broadband photometry and provide a quantitative analysis of the structure of galaxies in the inner region of the Abell Cluster 2443 (z~0.1). The galaxy parameters have been derived by fitting a two-component model (Sersic r^1/n^ bulge and exponential disk) to a magnitude-limited sample. Using a new method of analysis that takes into account the effects of seeing on the structural parameters and considers ellipticity as an active parameter, we avoid systematic errors arising from assumptions of circular symmetry. Of the sample galaxies, 76% were classified with these models, while the rest were morphologically peculiar. For the spiral galaxies, the relation between n and B/D is consistent with the trend observed in nearby field galaxy samples. The Sersic index n (which can be considered as a concentration index) of the elliptical galaxies is correlated with the local surface density of the cluster. Monte Carlo simulations were used to check the reliability of the method and determine the magnitude selection criteria. Observations were obtained on 1998 August 19 at the 2.5 m Nordic Optical Telescope (NOT) at the Observatorio del Roque de los Muchachos on La Palma. The prime-focus CCD camera was used with pixel scale of 0.11"/pix, and the seeing ranged from FWHM 0.88" to 1".
We present a study of the distribution of AGNs in clusters of galaxies with a uniformly selected, spectroscopically complete sample of 35 AGNs in eight clusters of galaxies at z=0.06-->0.31. We find that the 12 AGNs with LX>10^42^ergs/s in cluster members more luminous than a rest-frame M_R_<-20mag are more centrally concentrated than typical cluster galaxies of this luminosity, although these AGNs have comparable velocity and substructure distributions to other cluster members.
