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All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

CCD surface photometry of field galaxies. I - Observations

Images of 105 galaxies selected from a larger complete sample of intrinsically luminous galaxies have been obtained for the purpose of computing surface brightness profiles. The intensity profiles along the major and minor axes are computed by a method in which elliptical contours whose position angle and ellipticity are allowed to vary with radius are fitted to the true isophotes of a galaxy. The resulting profiles and ellipse parameters are listed for each object. An extensive comparison of the present photometry with that of other workers is made to assess the reliability of the data. For most objects, additional photometric information is given, including an isophotal radius and magnitude within a limiting isophote of 24.0 mag/sq arcsec, an approximate total magnitude, the effective radius containing one-half the total light, and the mean surface brightness inside this radius. A full analysis of the data is deferred to a second paper where the profiles will be decomposed into bulge and disk components.

Kent, S. M.↗
NASA NTRS1984

Photometry of resolved galaxies. IV - Holmberg I and Holmberg II

Colors and magnitudes are presented for 279 resolved stars in the Holmberg I dwarf galaxy and 468 resolved stars in Holmberg II. Both systems are Magellanic type dwarf members of the M81-NGC 2403 Group, which lies at approximately 3 Mpc from the Local Group. The photometry was done in the GRI passbands using CCD detectors. Color-magnitude diagrams and luminosity functions are constructed; these are compared with results for several Local Group galaxies and with theoretical work. Holmberg I is found to have a low present star formation rate, while Holmberg II is very active at present.

Hoessel, J. G.↗
NASA NTRS1986

Three-color CCD photometry of the distant cluster of galaxies Cl 0024 + 1654

Photometry of 265 galaxies in rich cluster Cl 0024 + 1654 (z = 0.39), based on CCD imaging in three filters, is presented. The luminosity of this system ranks it among the richest known clusters, and it has a blue mass-to-light ratio of about 210. The color-magnitude diagram has a prominent E/S0 sequence. There are essentially no blue cluster members brighter than r equals about 19.3, and only very red galaxies inhabit the central 30 arcsec of the cluster. The blue cluster members have sizes and surface brightnesses similar to spiral galaxies in nearby clusters.

Schneider, D. P.↗
NASA NTRS1995

Automated surface photometry for the Coma Cluster galaxies: The catalog

A homogeneous photometry catalog is presented for 450 galaxies with B(sub 25.5) less than or equal to 16 mag located in the 9.8 deg x 9.8 deg region centered on the Coma Cluster. The catalog is based on photographic photometry using an automated surface photometry software for data reduction applied to B-band Schmidt plates. The catalog provides accurate positions, isophotal and total magnitudes, major and minor axes, and a few other photometric parameters including rudimentary morphology (early of late type).

Doi, M.↗
NASA NTRS1972

Photometry of compact galaxies.

Photometric histories of the N galaxies 3C 390.3 and PKS 0521-36. Four other compact galaxies, Markarian 9, I Zw 92, 2 Zw 136, and III Zw 77 showed no evidence of variability. The photometric histories were obtained from an exhaustive study of those plates of the Harvard collection taken with large aperture cameras. The images of all galaxies reported were indistinguishable from stars due to the camera f-ratios and low surface brightness of the outlying nebulosities of the galaxies. Standard techniques for the study of variable stars are therefore applicable.

Shen, B. S. P.↗
NASA NTRS1981

Surface photometry of spiral galaxies. I - Theoretical color variation and surface brightness across spiral arms

A method for the construction of color variations and surface brightness across a galactic spiral arm, using the concepts and results of the density-wave theory, is developed. The color variation measured by the index Q varies with the ratio of the light of young stars to that of the old stars, the initial mass function, and the pattern speed. The fact that the variation of brightness and color across a spiral arm is relatively smooth and symmetrical and not sharp as in the galactic shock picture is due to the smearing-out effects of star formation inside a cloud in the regions behind the galactic shock, and the tendency of new stars to fall back to small galactocentric distances after their formation because of their lower angular velocity at birth. Both effects arise naturally in the context of the density-wave theory.

Yuan, C.↗
NASA NTRS1982

Photometry of resolved galaxies. I - The Pegasus dwarf irregular

Color-magnitude diagrams for resolved stars in the Pegasus dwarf galaxy in the green, red, and infrared passbands of the extended Gunn photometric system are presented. The evolved nature of the upper main sequence and the lack of luminous red supergiants indicate that recent star formation in Pegasus has been very subdued. Three star clusters are identified. Their red colors indicate they are of intermediate age or older. Two features of the color-magnitude diagrams are of interest: a group of red stars with I at about 21.3, which may be the counterparts of the carbon stars found in the Magellanic Clouds, and a clump in the (I, R-I)-diagram, which is probably the tip of the old giant branch. A provisional distance estimate for Pegasus of 1.7 Mpc is derived, placing it at the outer margins of the Local Group.

Hoessel, J. G.↗
NASA NTRS1983

Photometry of resolved galaxies. II - Sextans A

Luminosity functions and color-magnitude diagrams are given for 652 stars in the Sextans A dwarf irregular galaxy, and they are compared with other Local Group galaxies. The brightest red and blue stars presently determined are in agreement with those of Sandage and Carlson (1982), and a group of red stars is identified which may be analogous to the bright carbon star population recently found in the Magellanic Clouds. While the similarity of Sextans A's luminosity function with those of the LMC and the Milky Way is in keeping with a universal luminosity function, stellar mass function and birthrate resemble those of the SMC. Per unit gas mass, Sextans A has a birthrate almost identical to the SMC, suggesting that the mean age of stars in Sextans A is significantly less than of those in the Magellanic Clouds.

Hoessel, J. G.↗
NASA NTRS1984

Studies of the Virgo Cluster. I - Photometry of 109 galaxies near the cluster center to serve as standards

Attention is given to the technical aspects of photometric measurements of 109 galaxies near the center of the Virgo Cluster, noting various types of radii and surface brightness for about 50 E and dE galaxies in the sample that range in absolute magnitude from -20 to -12. These data are combined with data from the literature for giant E and dwarf E galaxies in the Local Group to study the systematic properties of E galaxies over a range of one million luminosities. The radial intensity profiles derived are fitted to the manifold of King (1978) models to derive model-dependent central surface brightness, core radii, and cutoff radii.

Sandage, A.↗
NASA NTRS1985

CCD surface photometry of field Galaxies. II - Bulge/disk decompositions

Major- and minor-axis profiles given previously for 105 galaxies of all morphological types are decomposed into bulge and disk components. In addition, three model-independent parameters which measure the mean surface brightness, scale radius, and degree of light concentration are derived. The best correlations are found between Hubble type, concentration, bulge/disk ratio, and mean surface brightness. Correlations between the individual bulge and disk parameters generally show large scatter. The properties of S0 galaxies are inconsistent with their having been formed from spiral galaxies via gas depletion; their properties are intermediate between those of ellipticals and spirals. Most elliptical galaxies probably do not form by the merging of disk galaxies. The difficulty of distinguishing between elliptical and S0 galaxies in some cases is emphasized.

Kent, D. M.↗
NASA NTRS1986

Multicolor photometry of field galaxies to B = 24

The redshifts and colors of nearly 10,000 galaxies at galactic latitudes SA57 and SA68 were determined by photometric scans which included UV and near-IR bands, covering 0.5 sq deg of sky. Slopes were calculated for UV, IR, red and blue counts of galaxies with respect to the brightness detected. It was found that galaxies of magnitudes over 20 show increasingly greater UV excess, which may be indicative of star formation regions. Future applications of the data generated for examining galaxy clustering patterns and evolutionary scenarios are discussed.

Koo, David C.↗
NASA NTRS1991

Surface photometry of radio galaxies. II - Cluster sources

R-band CCD photometric observations are reported for 52 radio galaxies in clusters for which good radio maps are available. Data obtained with the No. 1 0.9-m telescope at KPNO (following the procedures described by Owen and Laing, 1989) are presented in tables and graphs and discussed in detail. Optical and radio luminosity are found to be well correlated in twin-jet, fat-double, narrow-angle-tail, and small-twin-jet sources, all of which are clearly distinguished from the classical doubles as in the scheme of Fanaroff and Riley (1974). It is also shown that the elliptical parent galaxies of the extended radio sources form a one-parameter family with the optical luminosity as the key parameter.

Owen, Frazer N.↗
NASA NTRS1982

BL Lac objects and their associated galaxies

CCD photometry of five BL Lac objects indicates that at least three, and possibly four, are located at the centers of giant elliptical galaxies. The redshift for one of these objects, 1218+304, is estimated. A lower limit is placed on the redshift of 1219+28, for which no associated galaxy has been detected. Separation of the galaxy emission from the total observed flux makes possible comparison of the optical - far red flux from the point source alone with radio and X-ray data. This comparison suggests the emission from 1727+50 and 1218+304 can be interpreted as due to direct synchrotron emission. Observations of a small group of galaxies associated with the BL Lac object 1400+162 are also discussed.

Weistrop, D.↗
NASA NTRS1983

Luminosity distributions for Virgo cluster galaxies. I Near-infrared surface photometry of 81 disk systems

I-band (8500 A) surface photometry of 81 galaxies in Virgo provides the basis for comparing the disk properties of S0 galaxies with those of Sa, Sb, and Sc systems. No significant difference is found in the distributions of either central surface brightness or exponential scale length between S0's and later Hubble types. Because the I-band is dominated by contributions from the old-disk population, this result suggests that the factors which control the distribution of luminous disk material in all types of disk systems are identical. Evidently, environmental factors have not played a significant role in affecting the star-forming histories of the Virgo disks.

Boroson, T. A.↗