Spectral Classification of Galaxies: an Orthogonal Approach

Connolly, Andrew J.; Szalay, A. S.; Bershady, M. A.; Kinney, A. L.; Calzetti, D.

doi:10.1086/117587

Cited by 211 publications

(306 citation statements)

References 9 publications

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“…In this paper the library is constructed by applying the principal component analysis ( PCA) technique (e.g., Connolly et al 1995;Lahav et al 1996;Bromley et al 1998;Eisenstein et al 2003;Yip et al 2004) to a sample of pure absorption-line galaxies.…”

Section: Stellar Subtractionmentioning

confidence: 99%

Active Galactic Nuclei in the Sloan Digital Sky Survey. I. Sample Selection

Hao¹,

Strauss²,

Tremonti³

et al. 2005

227

206

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We have compiled a large sample of low-redshift active galactic nuclei (AGNs) identified via their emission-line characteristics from the spectroscopic data of the Sloan Digital Sky Survey. Since emission lines are often contaminated by stellar absorption lines , we developed an objective and efficient method of subtracting the stellar continuum from every galaxy spectrum before making emission-line measurements. The distribution of the measured H FWHM values of emission-line galaxies is strongly bimodal, with two populations separated at about 1200 km s À1 . This feature provides a natural separation between narrow-line and broad-line AGNs. The narrowline AGNs are identified using standard emission-line ratio diagnostic diagrams. There are 1317 broad-line and 3074 narrow-line AGNs identified from about 100,000 galaxy spectra selected over 1151 deg 2 . This sample is used in a companion paper to determine the emission-line luminosity function of AGNs.

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Section: Stellar Subtractionmentioning

confidence: 99%

Active Galactic Nuclei in the Sloan Digital Sky Survey. I. Sample Selection

Hao¹,

Strauss²,

Tremonti³

et al. 2005

227

206

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“…Panel a shows the histogram of the galaxy spectral classification parameter eClass as provided by the SDSS for DR1. This spectral classification parameter is based on a principal component analysis method (Connolly et al 1995;Connolly & Szalay 1999). Note that the spectral classification of galaxies by Connolly et al (1995) is slightly different from the one used in SS99 who removed from the analysis the wavelength regions containing emission lines.…”

Section: Overall Properties Of Our Sample Of Normal Galaxiesmentioning

confidence: 99%

What drives the Balmer extinction sequence in spiral galaxies?

Stasińska

Mateus

Sodré

et al. 2004

A&A

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Abstract. Using spectra of normal emission line galaxies from the First Data Release of the Sloan Digital Sky Survey (SDSS) we have investigated the relations between the extinction C(Hβ) as derived from the Hα/Hβ emission line ratio and various global parameters of the galaxies. Our main findings are that: 1) C(Hβ) is linked with the galaxy spectral type and colour, decreasing from early-to late-type spirals; 2) C(Hβ) increases with increasing metallicity; 3) C(Hβ) is larger in galaxies with an older stellar population; 4) C(Hβ) is larger for more luminous galaxies; 5) The extinction of the stellar light is correlated with both the extinction of the nebular light and the intrinsic galaxy colours. We propose phenomenological interpretations of our empirical results. We have also cross-correlated our sample of SDSS galaxies with the IRAS data base. Due to the lower redshift limit of our sample and to the detection limit of IRAS, such a procedure selected only luminous infrared galaxies. We found that correlations that were shown by other authors to occur between optical and infrared properties of galaxies disappear when restricted the sample to luminous infrared galaxies. We also found that the optical properties of the luminous infrared galaxies in our SDSS sample are very similar to those of our entire sample of SDSS galaxies. This may be explained by the IRAS luminosity of the galaxies originating in the regions that formed massive stars less than 1 Myr ago, while the opacity of galaxies as derived from the Hα/Hβ emission line ratio is due to diffuse dust. We show some implications of our empirical results for the determination of global star formation rates and total stellar masses in normal galaxies.

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“…These include the calculation of rest-frame colors (e.g., Strateva et al 2001); principal component analysis (PCA) based spectral classifications (e.g., Connolly et al 1995;Bromley et al 1998;Folkes et al 1999;Madgwick et al 2002;de Lapparent et al 2003), and other more sophisticated discriminations (e.g., Heavens, Jimenez, & Lahav 2000;Slonim et al 2001), based upon information theory. The underlying theme of all these alternative methods is that they characterize the galaxy population exclusively in terms of their observed spectra.…”

Section: Introductionmentioning

confidence: 99%

The DEEP2 Galaxy Redshift Survey: Spectral Classification of Galaxies at \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontComman

Madgwick

Coil

Conselice

et al. 2003

ApJ

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We present a principal component analysis (PCA)-based spectral classification, , for the first 5600 galaxies observed in the DEEP2 Redshift Survey. This parameter provides a very pronounced separation between absorption-and emission-dominated galaxy spectra-corresponding to passively evolving and actively star-forming galaxies in the survey, respectively. In addition it is shown that, despite the high resolution of the observed spectra, this parameter alone can be used to quite accurately reconstruct any given galaxy spectrum, suggesting there are not many '' degrees of freedom '' in the observed spectra of this galaxy population. It is argued that this form of classification, , will be particularly valuable in making future comparisons between high-and low-redshift galaxy surveys for which very large spectroscopic samples are now readily available, particularly when used in conjunction with high-resolution spectral synthesis models, which will be made public in the near future. We also discuss the relative advantages of this approach to distant galaxy classification compared to other methods such as colors and morphologies. Finally, we compare the classification derived here with that adopted for the 2dF Galaxy Redshift Survey and in so doing show that the two systems are very similar. This will be particularly useful in subsequent analyses when making comparisons between results from each of these surveys to study evolution in the galaxy populations and large-scale structure.

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Spectral Classification of Galaxies: an Orthogonal Approach

Cited by 211 publications

References 9 publications

Active Galactic Nuclei in the Sloan Digital Sky Survey. I. Sample Selection

Active Galactic Nuclei in the Sloan Digital Sky Survey. I. Sample Selection

What drives the Balmer extinction sequence in spiral galaxies?

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