The Digitized Second Palomar Observatory Sky Survey (DPOSS). III. Star-galaxy separation

S. C. Odewahn, R. R. De Carvalho, R. R. Gal, S. G. Djorgovski, Robert J Brunner, A. Mahabal, P. A.A. Lopes, J. L.Kohl Moreira, B. Stalder

Research output: Contribution to journalReview article

Abstract

We discuss object classification for a multicolor survey of high-latitude fields from the Digitized Second Palomar Observatory Sky Survey (DPOSS) and the resulting Palomar-Norris Sky Catalog. Two methods are used to perform automated image classification for star-galaxy separation in DPOSS. As a source of classifier training/testing data, we employ an unprecedented 500 field collection of CCD photometry in the Thuan & Gunn gri system obtained with the Palomar 60 inch (1.5 m) telescope. We have trained artificial neural network (ANN) and decision tree (DT) image classifiers using images of ≈4000 galaxies and ≈3000 stars classified with FOCAS on 52 deep CCD images. We assess the systematic errors in our classifiers as a function of apparent magnitude. To model the loss of galaxies through misclassification and the contamination of our galaxy samples by misclassified stars, we compare the DPOSS ANN+DT image classifications with image data from 46 CCD fields on 21 POSS-II fields not used in the initial training/testing process. We assess these same functions in a more stringent manner by comparing classifications of DPOSS images common with different fields via the plate overlaps. These tests are combined to derive analytic descriptions of sample incompleteness and contamination for future use in our assessment of multicolor galaxy number counts and the two-point angular correlation function. Finally, we derive star and galaxy number counts from 341 DPOSS fields covering a total of 7756 deg 2 in both the north and south Galactic hemispheres. These data are used to establish a final correction for stellar contamination in our galaxy samples and to demonstrate the level of classification homogeneity in the DPOSS g and r catalogs drawn from a wide range of Galactic latitudes.

Original languageEnglish (US)
Pages (from-to)3092-3107
Number of pages16
JournalAstronomical Journal
Volume128
Issue number6
DOIs
StatePublished - Dec 1 2004

Fingerprint

observatories
observatory
galaxies
stars
classifiers
image classification
charge coupled devices
contamination
artificial neural network
catalogs
education
homogeneity
field survey
hemispheres
angular correlation
systematic errors
polar regions
photometry
sky
coverings

Keywords

  • Catalogs
  • Methods: data analysis
  • Surveys

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Odewahn, S. C., De Carvalho, R. R., Gal, R. R., Djorgovski, S. G., Brunner, R. J., Mahabal, A., ... Stalder, B. (2004). The Digitized Second Palomar Observatory Sky Survey (DPOSS). III. Star-galaxy separation. Astronomical Journal, 128(6), 3092-3107. https://doi.org/10.1086/425525

The Digitized Second Palomar Observatory Sky Survey (DPOSS). III. Star-galaxy separation. / Odewahn, S. C.; De Carvalho, R. R.; Gal, R. R.; Djorgovski, S. G.; Brunner, Robert J; Mahabal, A.; Lopes, P. A.A.; Moreira, J. L.Kohl; Stalder, B.

In: Astronomical Journal, Vol. 128, No. 6, 01.12.2004, p. 3092-3107.

Research output: Contribution to journalReview article

Odewahn, SC, De Carvalho, RR, Gal, RR, Djorgovski, SG, Brunner, RJ, Mahabal, A, Lopes, PAA, Moreira, JLK & Stalder, B 2004, 'The Digitized Second Palomar Observatory Sky Survey (DPOSS). III. Star-galaxy separation', Astronomical Journal, vol. 128, no. 6, pp. 3092-3107. https://doi.org/10.1086/425525
Odewahn SC, De Carvalho RR, Gal RR, Djorgovski SG, Brunner RJ, Mahabal A et al. The Digitized Second Palomar Observatory Sky Survey (DPOSS). III. Star-galaxy separation. Astronomical Journal. 2004 Dec 1;128(6):3092-3107. https://doi.org/10.1086/425525
Odewahn, S. C. ; De Carvalho, R. R. ; Gal, R. R. ; Djorgovski, S. G. ; Brunner, Robert J ; Mahabal, A. ; Lopes, P. A.A. ; Moreira, J. L.Kohl ; Stalder, B. / The Digitized Second Palomar Observatory Sky Survey (DPOSS). III. Star-galaxy separation. In: Astronomical Journal. 2004 ; Vol. 128, No. 6. pp. 3092-3107.
@article{75a774859edd493a88ded526b1953dc1,
title = "The Digitized Second Palomar Observatory Sky Survey (DPOSS). III. Star-galaxy separation",
abstract = "We discuss object classification for a multicolor survey of high-latitude fields from the Digitized Second Palomar Observatory Sky Survey (DPOSS) and the resulting Palomar-Norris Sky Catalog. Two methods are used to perform automated image classification for star-galaxy separation in DPOSS. As a source of classifier training/testing data, we employ an unprecedented 500 field collection of CCD photometry in the Thuan & Gunn gri system obtained with the Palomar 60 inch (1.5 m) telescope. We have trained artificial neural network (ANN) and decision tree (DT) image classifiers using images of ≈4000 galaxies and ≈3000 stars classified with FOCAS on 52 deep CCD images. We assess the systematic errors in our classifiers as a function of apparent magnitude. To model the loss of galaxies through misclassification and the contamination of our galaxy samples by misclassified stars, we compare the DPOSS ANN+DT image classifications with image data from 46 CCD fields on 21 POSS-II fields not used in the initial training/testing process. We assess these same functions in a more stringent manner by comparing classifications of DPOSS images common with different fields via the plate overlaps. These tests are combined to derive analytic descriptions of sample incompleteness and contamination for future use in our assessment of multicolor galaxy number counts and the two-point angular correlation function. Finally, we derive star and galaxy number counts from 341 DPOSS fields covering a total of 7756 deg 2 in both the north and south Galactic hemispheres. These data are used to establish a final correction for stellar contamination in our galaxy samples and to demonstrate the level of classification homogeneity in the DPOSS g and r catalogs drawn from a wide range of Galactic latitudes.",
keywords = "Catalogs, Methods: data analysis, Surveys",
author = "Odewahn, {S. C.} and {De Carvalho}, {R. R.} and Gal, {R. R.} and Djorgovski, {S. G.} and Brunner, {Robert J} and A. Mahabal and Lopes, {P. A.A.} and Moreira, {J. L.Kohl} and B. Stalder",
year = "2004",
month = "12",
day = "1",
doi = "10.1086/425525",
language = "English (US)",
volume = "128",
pages = "3092--3107",
journal = "Astronomical Journal",
issn = "0004-6256",
publisher = "IOP Publishing Ltd.",
number = "6",

}

TY - JOUR

T1 - The Digitized Second Palomar Observatory Sky Survey (DPOSS). III. Star-galaxy separation

AU - Odewahn, S. C.

AU - De Carvalho, R. R.

AU - Gal, R. R.

AU - Djorgovski, S. G.

AU - Brunner, Robert J

AU - Mahabal, A.

AU - Lopes, P. A.A.

AU - Moreira, J. L.Kohl

AU - Stalder, B.

PY - 2004/12/1

Y1 - 2004/12/1

N2 - We discuss object classification for a multicolor survey of high-latitude fields from the Digitized Second Palomar Observatory Sky Survey (DPOSS) and the resulting Palomar-Norris Sky Catalog. Two methods are used to perform automated image classification for star-galaxy separation in DPOSS. As a source of classifier training/testing data, we employ an unprecedented 500 field collection of CCD photometry in the Thuan & Gunn gri system obtained with the Palomar 60 inch (1.5 m) telescope. We have trained artificial neural network (ANN) and decision tree (DT) image classifiers using images of ≈4000 galaxies and ≈3000 stars classified with FOCAS on 52 deep CCD images. We assess the systematic errors in our classifiers as a function of apparent magnitude. To model the loss of galaxies through misclassification and the contamination of our galaxy samples by misclassified stars, we compare the DPOSS ANN+DT image classifications with image data from 46 CCD fields on 21 POSS-II fields not used in the initial training/testing process. We assess these same functions in a more stringent manner by comparing classifications of DPOSS images common with different fields via the plate overlaps. These tests are combined to derive analytic descriptions of sample incompleteness and contamination for future use in our assessment of multicolor galaxy number counts and the two-point angular correlation function. Finally, we derive star and galaxy number counts from 341 DPOSS fields covering a total of 7756 deg 2 in both the north and south Galactic hemispheres. These data are used to establish a final correction for stellar contamination in our galaxy samples and to demonstrate the level of classification homogeneity in the DPOSS g and r catalogs drawn from a wide range of Galactic latitudes.

AB - We discuss object classification for a multicolor survey of high-latitude fields from the Digitized Second Palomar Observatory Sky Survey (DPOSS) and the resulting Palomar-Norris Sky Catalog. Two methods are used to perform automated image classification for star-galaxy separation in DPOSS. As a source of classifier training/testing data, we employ an unprecedented 500 field collection of CCD photometry in the Thuan & Gunn gri system obtained with the Palomar 60 inch (1.5 m) telescope. We have trained artificial neural network (ANN) and decision tree (DT) image classifiers using images of ≈4000 galaxies and ≈3000 stars classified with FOCAS on 52 deep CCD images. We assess the systematic errors in our classifiers as a function of apparent magnitude. To model the loss of galaxies through misclassification and the contamination of our galaxy samples by misclassified stars, we compare the DPOSS ANN+DT image classifications with image data from 46 CCD fields on 21 POSS-II fields not used in the initial training/testing process. We assess these same functions in a more stringent manner by comparing classifications of DPOSS images common with different fields via the plate overlaps. These tests are combined to derive analytic descriptions of sample incompleteness and contamination for future use in our assessment of multicolor galaxy number counts and the two-point angular correlation function. Finally, we derive star and galaxy number counts from 341 DPOSS fields covering a total of 7756 deg 2 in both the north and south Galactic hemispheres. These data are used to establish a final correction for stellar contamination in our galaxy samples and to demonstrate the level of classification homogeneity in the DPOSS g and r catalogs drawn from a wide range of Galactic latitudes.

KW - Catalogs

KW - Methods: data analysis

KW - Surveys

UR - http://www.scopus.com/inward/record.url?scp=12444344836&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=12444344836&partnerID=8YFLogxK

U2 - 10.1086/425525

DO - 10.1086/425525

M3 - Review article

AN - SCOPUS:12444344836

VL - 128

SP - 3092

EP - 3107

JO - Astronomical Journal

JF - Astronomical Journal

SN - 0004-6256

IS - 6

ER -