Faint Object Classification Research Articles

The application of the Faint Object Classification and Analysis System (FOCAS) and Source Extractor (SExtractor) packages to the Digitized Sky Survey

In this paper the comparison between the Faint Object Classification and Analysis System (FOCAS) and Source Extractor (SExtractor) packages for automated star–galaxy classification is discussed. The analysis presented here uses a data set containing 43 Abell clusters of galaxies obtained from the Digitized Sky Survey. Comparison is based on four image parameters: the magnitude, area, ellipticity and position angle computed for each object. Statistical analysis shows that in the case of individual clusters, in general, there is good correlation between parameters obtained from both packages. The comparison of visual classification with automatic classification from FOCAS shows that the percentage of misclassified galaxies is about 20.

DWARF GALAXIES IN THE COMA CLUSTER. I. DETECTION, MEASUREMENT AND CLASSIFICATION TECHNIQUES

ABSTRACT Deep B- and R-band CCD images of the central ~ 700 arcmin2 of the Coma cluster core have been used to measure the dwarf-galaxy population in Coma. In this paper, we describe a newly developed code for automated detection, photometry and classification of faint objects of arbitrary shape and size on digital images. Intensity-weighted moments are used to compute the positions, radial structures, ellipticities, and integrated magnitudes of detected objects. We demonstrate that Kron-type 2 r1 aperture aperture magnitudes and surface brightnesses are well suited to faint-galaxy photometry of the type described here. Discrimination between starlike and extended (galaxy) objects is performed interactively through parameter-space culling in several possible parameters, including the radial moments, surface brightness, and integrated color versus magnitude. Our code is tested and characterized with artificial CCD images of star and galaxy fields; it is demonstrated to be accurate, robust and versatile. Using these analysis techniques, we detect a large population of dE galaxies in the Coma cluster core. These dEs stand out as a tight sequence in the R, (B-R) color-magnitude diagram.

DEEP CCD PHOTOMETRY OF THE RICH GALAXY CLUSTER ABELL 1656: CHARACTERISTICS OF THE DWARF ELLIPTICAL GALAXY POPULATION IN THE CLUSTER CORE

ABSTRACT I have developed a statistically rigorous and automated program code (DYNAMO) to implement the detection, photometry and classification of faint objects on digital images. Detected objects correspond to local maxima of the intensity distribution, whose peak-flux pixel intensity exceeds a user-defined threshold. For all detected objects, several intensity-weighted quantities are computed: average and centers, the radial moments r1 and r-2, the ellipticity epsilon and the concentration index cin. Then, Kron's 2r1 total magnitude, integrated colors derived from standard fixed aperture magnitudes, and measures of surface brightness (central and average) are then calculated for each object. The process of discrimination between galaxy and starlike objects is performed interactively, through parameter-space culling and color-magnitude discrimination. Statistical number correction with remote background fields can then be used to further reduce contamination in the resulting distributions. This program code was tested and characterized using artificial CCD images of star and galaxy fields: it is accurate, robust and versatile. I have analyzed deep R- and B-band KPNO 4-m CCD images of the central ~700 arcmin2 of the Coma cluster (Abell 1656, v ~= 7000 km/s, richness-class 2), using the new photometry software described above. I detected and measured total R magnitudes and (B-R) colors for a sample of 3741 objects in Coma cluster core and 1164 objects on a remote control field, complete to a limiting magnitude of R = 22.5 mag. The typical uncertainties are ±0.06 and ±0.12 mag in total magnitude and color respectively. The dwarf elliptical (dE) galaxies are confined to a tight sequence in the color range given by 0.7 ≤ (B-R) ≤ 1.9 mag; within this interval there are 2535 dE candidates in the cluster core, and 694 objects on the control field (2.57 X less area). Scaling the number of objects on the control field to the area of the program fields leaves a sample of about 750 candidate dwarf elliptical galaxies. I detected a significant color gradient in the radial distribution of dE galaxies, and calibrating a color-metallicity relationship based upon Galactic globular clusters, this color gradient corresponds to a metallicity gradient which goes as Z proportional to R-0.32 outwards from the cluster center at NGC 4874. As well, there is a strong color-luminosity correlation: for each one magnitude increase in R, the dEs become redder (in the mean) by 0.062 mag in (B-R). These observations are consistent with a model in which the intracluster gas exerted a confinement pressure (greatest near the cluster core), impeding the outflow of supernovae-driven metal-rich gas from the young dE galaxies. The spatial distribution of the faint dE galaxies is well fit by a standard King model with a central surface density of Sigma0 = 1.424 dEs arcmin-2 and a core radius of Rc = 18.73 arcmin (~= 0.44 Mpc). This core radius is significantly larger than Rc = 12.3 arcmin found for the brightest dEs and giant cluster galaxies, and it is consistent with tidal disruption of faint dEs in the dense cluster core. The composite luminosity function for the Coma cluster galaxies (completeness corrected and background subtracted) was modeled as the sum of a Gaussian distribution for the giant galaxies and a Schechter function for the dE galaxies. In this manner, weighted least-squares fits and subsequent numerical integration allowed us to solve for the relative contributions of the two populations. During this modeling and analysis, the dispersion of the Gaussian distribution was constrained to the observed range sigma = 1.0 ± 0.20 mag, while the faint-end slope of the Schechter function was constrained to alpha = -1.41 ± 0.05, calculated for this luminosity function from a separate analysis. Decomposing the galaxy luminosity function in this manner, I found that the early-type dwarf-to-giant ratio (EDGR) for the Coma cluster core is identical with that of the Virgo cluster. I proposed that the presence of substructure is an important factor in determining the cluster's EDGR, since during the merger of two or more richness-class 1 galaxy clusters, the total number of dwarf and giant galaxies will be conserved (to first order). Thus, this low EDGR result is consistent with the Coma cluster being formed as the merger of multiple, less-rich galaxy clusters.

FOCAS AUTOMATIC CATALOG MATCHING ALGORITHMS

ABSTRACT This paper describes efficient algorithms that automatically take two or more catalogs of objects with instrumental coordinates and magnitudes and matches them. The challenges are that the instrumental coordinates may be only partially overlapping, at a different scale, rotated, or even inverted (flipped). The object magnitudes may be derived from different passbands so that the relative magnitudes of the objects differ. Also, the catalog may not contain all the same objects to to differences in separating close objects or to partial overlap between images. Finally, the catalog positions and magnitudes are subject to noise in the images from which they were derived. The algorithms are applicable to any automated cataloging system. However, the implementation described here is part of the Faint Object Classification and Analysis System (FOCAS). FOCAS automatically produces catalogs of objects from digital images. The algorithms described here first take a subsample of the brightest objects from the catalog, and other catalogs. Then all the objects in the catalogs are matched based on the transformed reference coordinates.

Faint Object Classification Using Artificial Neural Networks

Artificial Neural Network techniques are applied to the classification of faint objects, detected in digital astronomical images, and a Bayesian classifier (the neural network classifier, NNC hereafter) is proposed. This classifier can be implemented using a feedforward multilayered neural network trained by the back-propagation procedure (Werbos 1974).

4513979 Machine tool with chucking controls : Martin L Silverman assigned to The Warner & Swasey Company

A photographic search of the five Earth-Moon Lagrangian positions included the solar-synchronized positions in the stable L4/L5 libration orbits, the potentially stable nonplanar orbits near L1/L2, Earth-Moon L3, and also L2 in the Sun-Earth system. Observations using the 61-cm Burrell Schmidt telescope at the Warner and Swasey Observatory, Kitt Peak Station, spanned 60° along the lunar orbital plane × 5° around Earth-Moon L5, 48° × 5° around L4, 25° × 13° around L3, 15° × 24° around the Moon (L1/L2), and 14° × 14° around Sun-Earth L2. Limiting magnitude for the detection of libration objects near L3, L4, and L5 was 17–19th magnitude, 10–18th magnitude for L1/L2 plates, and 14–16th magnitude for Sun-Earth L2. No natural or artificial objects were found. An automated search of selected priority plates was attempted using the Faint Object Classification and Analysis System (FOCAS) software package.

New limits on the surface density of M dwarfs. I - Photographic survey and preliminary CCD data

view Abstract Citations (28) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS New limits on the surface density of M dwarfs. I. Photographic survey and preliminary CCD data. Boeshaar, P. C. ; Tyson, J. A. Abstract Several observations have suggested a massive, dark component to galaxies (the 'mission mass' controversy). Very-low-mass stars near the hydrogen-burning limit (0.07 solar masses) have long been a favorite theoretical candidate for the missing mass. It is shown that the Faint Object Classification and Analysis System faint red star counts do not support this hypothesis for the disk and that the stellar luminosity function at the faint end of the main sequence (for the lowest-mass stars, M less than 0.1 solar masses) most likely decreases with decreasing with decreasing absolute luminosity. This faint red star search was done out to 40-100 pc from the sun; it implies small or negligible dynamical consequences arising from intrinsically faint stars in the disk. This extreme M-dwarf search is being continued to beyond 2 kpc (halo) with the new CCD survey on the CTIO 4-m telescope. Multicolor CCD data on the Lowell 1.8-m telescope for a complete sequence of M dwarfs to dM9 is presented. The 0.7-1 micron color of the most extreme M dwarfs reaches a limiting value. Publication: The Astronomical Journal Pub Date: May 1985 DOI: 10.1086/113791 Bibcode: 1985AJ.....90..817B Keywords: Astronomical Photography; Dwarf Stars; Galactic Structure; Missing Mass (Astrophysics); Stellar Structure; Charge Coupled Devices; Color-Magnitude Diagram; Elliptical Galaxies; Mass To Light Ratios; Stellar Luminosity; Stellar Magnitude; Stellar Spectrophotometry; Astrophysics full text sources ADS | data products SIMBAD (11)

A search for objects near the Earth-Moon Lagrangian points

A photographic search of the five Earth-Moon Lagrangian positions included the solar-synchronized positions in the stable L4/L5 libration orbits, the potentially stable nonplanar orbits near L1/L2, Earth-Moon L3, and also L2 in the Sun-Earth system. Observations using the 61-cm Burrell Schmidt telescope at the Warner and Swasey Observatory, Kitt Peak Station, spanned 60° along the lunar orbital plane × 5° around Earth-Moon L5, 48° × 5° around L4, 25° × 13° around L3, 15° × 24° around the Moon (L1/L2), and 14° × 14° around Sun-Earth L2. Limiting magnitude for the detection of libration objects near L3, L4, and L5 was 17–19th magnitude, 10–18th magnitude for L1/L2 plates, and 14–16th magnitude for Sun-Earth L2. No natural or artificial objects were found. An automated search of selected priority plates was attempted using the Faint Object Classification and Analysis System (FOCAS) software package.

FOCAS - Faint Object Classification and Analysis System

view Abstract Citations (324) References (18) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Focas: faint object classification and analysis system. Jarvis, J. F. ; Tyson, J. A. Abstract The FOCAS (Faint Object Classification and Analysis System) apparatus for the detection and classification of images on astronomical plates which is intended to be used for the automatic assembly of catalogs of faint objects, is presented. The system has been used to process plates obtained by the KPNO 40-m telescope under good seeing conditions for 12 selected areas, which were digitized in 20-micron steps with a 20-sq micron pixel in a 6000 x 6000 raster corresponding to a field 37 arcmin on a side. The FOCAS acts to reduce the digitized image to a list including the magnitude, position and classification data for objects in the field as faint as the 24th magnitude, by a process including the segmentation of objects, object area assembly, and object assembly. Objects are then classified as noise, stars or galaxies on the basis of conventional nonparametric statistical pattern recognition techniques, and catalogs of objects meeting given criteria can be obtained by various programs. System tests have shown detection efficiencies of 97% and classification capabilities for 90 and 80% of the galaxies and stars, respectively, for apparent magnitudes down to 24, although the optimality and accuracy of the classifier have not been established. FOCAS has been used to assemble catalog of 86,000 objects which is 3 to 4 mag deeper than existing surveys. Publication: The Astronomical Journal Pub Date: March 1981 DOI: 10.1086/112907 Bibcode: 1981AJ.....86..476J Keywords: Astronomical Catalogs; Astronomical Photography; Celestial Bodies; Image Resolution; Systems Analysis; Classifications; Digital Systems; Galaxies; Magnitude; Pattern Recognition; Photographic Plates; Stars; Astronomy full text sources ADS | data products SIMBAD (7)

Automated Faint Galaxy Counts and Galactic Evolution

Detection and classification of faint images by eye has traditionally encountered systematic errors faintwards of 20th mag on Schmidt plates and 22nd mag on 4-meter plates. Automated classification of Schmidt plate images has pushed the classification limit to 22 mag (Kibblewhite, et al., 1975). Automated detection and classification of faint 4-meter limit plate images has recently led to statistical studies of galaxy numbers and clustering at redshifts where cosmology and galactic evolution dominate over local effects. Here we report on some aspects of the FOCAS (Faint Object Classification and Analysis System) automated classifier (Tyson and Jarvis, 1979) and compare our results of number counts in SA57 with those of Kron, 1979. Differential galaxy counts in six high latitude fields and evidence for galaxy evolution are briefly discussed.