Teh Effect of Stellar Contamination on Different Measures of Galaxy Photometry
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Fundamental parameters of brightest cluster galaxies
Photometry and spectroscopy of a sample of the brightest cluster galaxies (BCGs) are presented, and the relationships between scale length, surface brightness, velocity dispersion, and line strength are determined and compared with the relations determined for lower luminosity ellipticals (LLEs). It is found that the relation between log r(e), log sigma, and mean surface brightness reported by Dressler et al. for LLEs also describes the relation for BCGs fairly well. Fundamental plane solutions for BCGs are derived which can be used as distance indicators with a predicted error of about 21 percent per galaxy. Only a weak correlation is found between the Na D 5893 line strength and velocity dispersion for BCGs, in contrast to the significant correlation between these quantities reported for LLEs. It is found that the mean mass-to-light ratio for BCGs is a factor of about two greater than for the LLEs in the Virgo and Coma sample of Dressler et al.
Oegerle, William R.↗
Surface photometry of galaxies. I - The SB0 NGC 2950
Surface photometry of NGC 2950, a classic example of the SB0 type galaxy, is presented. The analysis shows that except for the rudimentary bar the galaxy closely resembles an S0 galaxy. The disk component has an exponential light curve with a central surface brightness of B(0) = 21.65 per square second of arc and a scale size of 4.3 kpc. The nucleus, bar, and disk components contain 29, 22, and 48 percent, respectively, of the light. Integral and differential colors are presented and discussed in terms of the three components mentioned above.
Crane, P.↗
CCD surface photometry of galaxies
We present here the results based on analysis of broad band optical images of radio loud and radio quiet galaxies selected from a set of x-ray galaxies. Data reduction techniques, and surface photometry using the IRAF data reduction package are described. The radial surface brightness profile of each galaxy is obtained. The disc, bulge, and nucleus of the galaxy are modeled based on the estimated brightness profile. The model of the galaxy is constructed, which is subtracted from the observed image to enhance the small scale features in the galaxy. Color maps of the galaxy are obtained and compared with those of normal galaxies. The optical properties of the galaxy are compared with its x-ray and radio properties.
Anupama, G. C.↗
Middle-ultraviolet photometry of Virgo cluster galaxies
Photographic photometry of Virgo cluster galaxies has been performed in a wavelength band extending from 1620-3200 A using sounding rocket techniques. The observational results are middle ultraviolet magnitudes, U2421, or faint limits for U2421, for 201 galaxies within 5.5 arcmin of the cluster center. A strong negative correlation is found between U2421 - V and V for all observed S0 galaxies and a similar but weaker correlation for the observed ellipticals. No such correlation is found for spiral galaxies regardless of their projection angles on the sky. The measured colors are generally compatible with colors computed from previously generated composite spectra.
Smith, A. M.↗
Intermediate bandpass photometry of galaxies and globular clusters
Galaxies and globular clusters, obtaining data by measurements with intermediate bandpass photometry
Neff, J. S.↗
Preliminary results of OAO ultraviolet photoelectric photometry of galaxies
General results are presented based on nearly completed reductions of data for approximately 35 galaxies of all Hubble types. In general the visual and ultraviolet energy distributions are well correlated. The energy distribution in late-type galaxies appears to turn up sharply in the region around 2000 A, and this is tentatively interpreted as due to the presence of early-type stars whose energy distribution is modified by interstellar dust within these objects. Similar turnups may be present in several elliptical galaxies but the evidence at this time is not definitive.
Code, A. D.↗
Surface colour photometry of galaxies with Schmidt telescopes.
A method is described which owes its practicality to the capability of Schmidt telescopes to record a number of galaxy images on a single plate and to the existence of high speed computer controlled area-scanning precision microdensitometers such as the Photometric Data Systems model 1010. The method of analysis results in quantitative color-index information which is displayed in a manner that allows any user to effectively study the morphological properties of the distribution of color-index in galaxies.
Wray, J. D.↗
Photometry of resolved galaxies. III - GR 8
Photometry of 84 resolved stellar images in GR 8 is presented. The numbers are derived by applying point spread function fitting techniques on digital images obtained with a three-phase Texas Instruments CCD. The resulting color-magnitude diagrams are discussed. These data are compared with theoretical stellar evolutionary tracks and similar results for other resolved galaxies.
Hoessel, J. G.↗
High-resolution surface photometry of elliptical galaxies
High-resolution CCD surface photometry profiles have been obtained for a sample of 42 nearby elliptical and SO galaxies as a first step in a program to investigate their central structure and core properties. A comparison of the present profiles to those of other observers shows that the accuracy of the central surface brightnesses is to better than 0.02 mag rms. Central resolution is limited by the atmospheric seeing PSF which is measured for each profile. A hybrid Fourier deconvolution procedure has been developed to correct the surface photometry for seeing in a model-independent way. Tests of the procedure on simulated galaxy images show that intrinsic core radii equal to the seeing FWHM or larger can be recovered from the observations. Application of the deconvolution procedure to the observed galaxies yields surface photometry profiles of slightly sub-arc second resolution.
Lauer, T. R.↗
Surface photometry of Virgo cluster galaxies - Barred galaxies
Photographic surface photometry in B and V is presented for three barred galaxies in the Virgo cluster: N4548, N4596, and N4608. Intercomparisons of luminosity and color profiles and standard photometric parameters indicate that for these galaxies: (1) the nuclear component follows the fourth-root-of-radius luminosity law for both B and V, (2) the luminosity profiles along the bar show a characteristic shoulder with a slight fall in B-V color profile at the brightest point in the bar, the strength of the effect declining from N4548 to N4608, (3) the integrated bar component is slightly bluer than the nucleus, and (4) as the disk, arm, and ring components contribute less to the total luminosity of the system, the contribution of the bar increases as does the equivalent gradient.
Benedict, G. F.↗
New Cepheid distances to nearby galaxies based on BVRI CCD photometry. II - The local group galaxy M33
A true distance modulus to the nearby spiral galaxy M33 has been determined based on CCD photometry obtained at BVRI wavelengths. M33 is presently one of five nearby galaxies used in the calibration of the IR Tully-Fisher relation, and thereby in the determination of the Hubble constant. Using period-luminosity relations at several wavelengths offers the advantage that the distance moduli derived can be corrected for the effects of interstellar extinction. These data indicate that there is internal reddening affecting the Cepheid photometry in M33 which must be accounted for if a true distance modulus is to be obtained for this galaxy. Adopting a true distance modulus to the LMC of 18.5 mag, the new CCD data yield a true distance to M33 of 24.64 + or - 0.09 mag, corresponding to a linear distance of 840 kpc. A mean value of the total color excess (foreground and internal) for the Cepheids in M33 is estimated to be E(B - V) = 0.10 + or - 0.09 mag, assuming a value for the total mean LMC Cepheid color excess of 0.10 mag.
Freedman, Wendy L.↗
An H II region beyond the optical disk of the galaxy
The detection of a faint H II region at a kinematic distance of 28 kpc from the Galactic center is reported. The velocity and morphology of H-alpha emission obtained using a Fabry-Perot indicate that the H II region is associated with a molecular cloud detected by Digel et al. (1993). The ionizing source must be close to the cloud and is constrained to be an early B star; a distant blue star, probably an early B supergiant, is identified as the ionizing star. Although its precise luminosity is uncertain, the likely range implies a distance modulus placing the H II region well beyond the optical disk of the Galaxy. Photometry of other stars associated with the GMC/H II region will allow a reliable distance determination and extend the rotation curve of the Galaxy by 60 percent. The implications of current star formation beyond the optical disk are discussed.
De Geus, E. J.↗
HST Observations of Star Formation in Interacting Galaxies: NGC 4194, the "Medusa"
Ultraviolet and visible imaging of the blue compact galaxy NGC4194 was obtained to survey the star-forming knots in the center of this galaxy. Photometry and image analysis were performed on these regions. Comparison with evolutionary tracks indicates many of the knots are reddened with a typical E(B-V)approx.0.3. The knot ages range from 10(exp 6-10(exp 8)years. Some of the knots may have masses 3-5x10(exp 5) solar mass. The FUV fluxes correspond to the flux from 60-3.8x10(exp 3) O5V stars.
Weistrop, D.↗
Disk Galaxies in the Outer Local Supercluster: Optical CCD Surface Photometry and Distribution of Galaxy Disk Parameter
We report new B-band CCD surface photometry on a sample of 76 disk galaxies brighter than BT = 14.5 mag in the Uppsala General Catalogue of Galaxies, which are confined within a volume located in the outer part of the Local Supercluster.
galaxies fundamental parameters Photometry spiral↗
Spectroscopy of galaxies in distant clusters. IV - A catalog of photometry and spectroscopy for galaxies in seven clusters with z in the range of 0.35 to 0.55
Photometry and spectroscopy for seven deep fields containing distant clusters of galaxies with z in the range of 0.35 to 0.55 are presented. Positions and photometric parameters, including r-magnitudes g - r and r - i colors, surface brightnesses, and photometric profile types are given for about 2000 galaxies. Low-resolution spectroscopy is obtained from which redshifts are determined for 289 objects, of which 190 are cluster members. These are classified according to dominant spectral features, and examples are plotted in each cluster. Color-magnitude and color-color diagrams are formed which show trends in the cluster populations, and maps are made of the cluster field using the color-color relations to increase the contrast of cluster over field. Galaxies with spectra typical of old stellar populations cluster most strongly, with active galaxies, those with recent or ongoing star formation, or an active nucleus, distributed more diffusely. The g - r color is well correlated with active star formation as judged from spectral features.
Dressler, Alan↗
Photometry of resolved galaxies. V - NGC 6822
Three-color CCD frames of the local group irregular galaxy NGC 6822 have been reduced to GRI photometry for 3475 stars using RICHFLD point-spread function fitting techniques. The data are compared with earlier work on this galaxy, particularly with Kayser (1966) on a star-by-star basis. Color-magnitude diagrams are constructed from the data and compared with both theoretical stellar model tracks and the expected foreground star contamination. A luminosity function for the blue stars is derived; comparison of this luminosity function with those of 10 other irregular galaxies indicates that NGC 6822 has a typical young star population. The stellar birthrate and initial mass function are estimated for this galaxy. The slope at the bright end of the mass function looks similar to recent results for the Galaxy, the Magellanic Clouds, and the irregular galaxy Sextans A. NGC 6822 appears to be presently forming stars at a slower rate for its mass than Sextans A or the Magellanic Clouds.
Hoessel, J. G.↗
The RSA survey of dwarf galaxies, 1: Optical photometry
We present detailed surface photometry, based on broad B-band charge coupled device (CCD) images, of about 80 dwarf galaxies. Our sample represents approximately 10% of all dwarf galaxies identified in the vicinity of Revised Shapley-Ames (RSA) galaxies on high resolution blue photographic plates, referred to as the RSA survey of dwarf galaxies. We derive global properties and radial surface brightness profiles, and examine the morphologies. The radial surface brightness profiles of dwarf galaxies, whether early or late type, display the same varieties in shape and complexity as those of classical giant galaxies. Only a few are well described by a pure r(exp 1/4) law. Exponential profiles prevail. Features typical of giant disk galaxies, such as exponential profiles with a central depression, lenses, and even, in one case (IC 2041), a relatively prominent bulge are also found in dwarf galaxies. Our data suggest that the central region evolves from being bulge-like, with an r(exp 1/4) law profile, in bright galaxies to a lens-like structure in dwarf galaxies. We prove detailed surface photometry to be a helpful if not always sufficient tool in investigating the structure of dwarf galaxies. In many cases kinematic information is needed to complete the picture. We find the shapes of the surface brightness profiles to be loosely associated with morphological type. Our sample contains several new galaxies with properties intermediate between those of giant and dwarf ellipticals (but no M32-like objects). This shows that such intermediate galaxies exist so that at least a fraction of early-type dwarf ellipticals is structurally related to early-type giants instead of belonging to a totally unrelated, disjunct family. This supports an origin of early-type dwarf galaxies as originally more massive systems that acquired their current morphology as a result of substantial, presumable supernova-driven, mass loss. On the other hand, several early-type dwarfs in our sample are merger candidates. Merger events may lead to anisotropic velocity distributions in systems of any luminosity, including dwarfs. The RSA sample of dwarf galaxies is more likely to contain mergers because, in contrast to earlier dwarf galaxy surveys that have focused on clusters and rich groups of galaxies, the RSA dwarfs are typically located in low density environments. The occurrence of mergers among dwarf galaxies is of interest in connection with the rapid evolution of faint blue galaxy counts at redshift z less than 1 which suggests that dwarf galaxies were about five times more numerous in the recent past. Finally, our sample contains several examples of late-type dwarfs and 'transition' types that are potential precursors of nucleated early-type dwarfs. All the above processes--mass loss, mergers, astration--are likely to have contributed to the formation of the current population of diffuse early-type dwarfs. A few new redshifts of dwarf galaxies are reported in this paper.
Vader, J. Patricia↗