The rest-frame optical colours of 99 000 sloan digital sky survey galaxies

V. Smolčić, Ž Ivezić, M. Gaćeša, K. Rakos, K. Pavlovski, S. Ilijić, M. Obrić, R. H. Lupton, D. Schlegel, G. Kauffmann, C. Tremonti, J. Brinchmann, S. Charlot, T. M. Heckman, G. R. Knapp, J. E. Gunn, J. Brinkmann, I. Csabai, M. Fukugita, J. Loveday

Research output: Contribution to journalArticle

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Abstract

We discuss the colours of 99 088 galaxies selected from the Sloan Digital Sky Survey (SDSS) Data Release 1 'main' spectroscopic sample (a flux-limited sample, r Pet <17.77, for 1360 deg 2) in the rest-frame Strömgren system (uz, vz, bz, yz). This narrow-band (∼200 Å) photometric system, first designed for the determination of effective temperature, metallicity and gravity of stars, measures the continuum spectral slope of galaxies in the rest-frame 3200-5800 Å wavelength range. We synthesize rest-frame Strömgren magnitudes from SDSS spectra, and find that galaxies form a remarkably narrow locus (∼0.03 mag) in the resulting colour-colour diagram. Using the Bruzual & Charlot population-synthesis models, we demonstrate that the position of a galaxy along this locus is controlled by metallicity and age of the dominant stellar population. The distribution of galaxies along the locus is bimodal, with the local minimum corresponding to an ∼1-Gyr-old single stellar population. The position of a galaxy perpendicular to the locus is independent of metallicity and age, and reflects the galaxy's dust content, as implied by both the models and the statistics of IRAS detections. Comparison of the galaxy locus in the rest-frame Strömgren colour-colour diagram with the galaxy locus in the Hδ A-D n(4000) diagram, utilized by Kauffmann et al. to estimate stellar masses, reveals a tight correlation, although the two analysed spectral ranges barely overlap. Furthermore, the rest-frame r - i colour (5500-8500 Å wavelength range) can be 'predicted' with an rms of 0.05 mag using the rest-frame Strömgren colours. Overall, the galaxy spectral energy distribution in the entire ultraviolet to near-infrared range can be described as a single-parameter family with an accuracy of 0.1 mag, or better. This nearly one-dimensional distribution of galaxies in the multidimensional space of measured parameters strongly supports the conclusion of Yip et al., based on a principal component analysis, that SDSS galaxy spectra can be described by a small number of eigenspectra. Furthermore, the rest-frame Strömgren colours correlate tightly with the classification scheme proposed by Yip et al. based on the first three eigenspectra. Apparently, the contributions of stellar populations that dominate the optical emission from galaxies are combined in a simple and well-defined way. We also find a remarkably tight correlation between the rest-frame Strömgren colours of emission-line galaxies and their position in the Baldwin-Phillips-Terlevich diagram. These correlations between colours and various spectroscopic diagnostic parameters support earlier suggestions that rest-frame Strömgren photometry offers an efficient tool to study faint cluster galaxies and low surface brightness objects without performing time-consuming spectral observations.

Original languageEnglish
Pages (from-to)121-137
Number of pages17
JournalMonthly Notices of the Royal Astronomical Society
Volume371
Issue number1
DOIs
Publication statusPublished - Sep 2006

Fingerprint

galaxies
color
loci
diagram
metallicity
color-color diagram
wavelength
diagrams
principal component analysis
near infrared
Infrared Astronomy Satellite
gravity
spectral energy distribution
principal components analysis
dust
stellar mass
wavelengths
suggestion
photometry
light emission

Keywords

  • Galaxies: fundamental parameters
  • Galaxies: Seyfert
  • Galaxies: statistics
  • Methods: statistical
  • Surveys

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Smolčić, V., Ivezić, Ž., Gaćeša, M., Rakos, K., Pavlovski, K., Ilijić, S., ... Loveday, J. (2006). The rest-frame optical colours of 99 000 sloan digital sky survey galaxies. Monthly Notices of the Royal Astronomical Society, 371(1), 121-137. https://doi.org/10.1111/j.1365-2966.2006.10662.x

The rest-frame optical colours of 99 000 sloan digital sky survey galaxies. / Smolčić, V.; Ivezić, Ž; Gaćeša, M.; Rakos, K.; Pavlovski, K.; Ilijić, S.; Obrić, M.; Lupton, R. H.; Schlegel, D.; Kauffmann, G.; Tremonti, C.; Brinchmann, J.; Charlot, S.; Heckman, T. M.; Knapp, G. R.; Gunn, J. E.; Brinkmann, J.; Csabai, I.; Fukugita, M.; Loveday, J.

In: Monthly Notices of the Royal Astronomical Society, Vol. 371, No. 1, 09.2006, p. 121-137.

Research output: Contribution to journalArticle

Smolčić, V, Ivezić, Ž, Gaćeša, M, Rakos, K, Pavlovski, K, Ilijić, S, Obrić, M, Lupton, RH, Schlegel, D, Kauffmann, G, Tremonti, C, Brinchmann, J, Charlot, S, Heckman, TM, Knapp, GR, Gunn, JE, Brinkmann, J, Csabai, I, Fukugita, M & Loveday, J 2006, 'The rest-frame optical colours of 99 000 sloan digital sky survey galaxies', Monthly Notices of the Royal Astronomical Society, vol. 371, no. 1, pp. 121-137. https://doi.org/10.1111/j.1365-2966.2006.10662.x
Smolčić, V. ; Ivezić, Ž ; Gaćeša, M. ; Rakos, K. ; Pavlovski, K. ; Ilijić, S. ; Obrić, M. ; Lupton, R. H. ; Schlegel, D. ; Kauffmann, G. ; Tremonti, C. ; Brinchmann, J. ; Charlot, S. ; Heckman, T. M. ; Knapp, G. R. ; Gunn, J. E. ; Brinkmann, J. ; Csabai, I. ; Fukugita, M. ; Loveday, J. / The rest-frame optical colours of 99 000 sloan digital sky survey galaxies. In: Monthly Notices of the Royal Astronomical Society. 2006 ; Vol. 371, No. 1. pp. 121-137.
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author = "V. Smolčić and Ž Ivezić and M. Gaćeša and K. Rakos and K. Pavlovski and S. Ilijić and M. Obrić and Lupton, {R. H.} and D. Schlegel and G. Kauffmann and C. Tremonti and J. Brinchmann and S. Charlot and Heckman, {T. M.} and Knapp, {G. R.} and Gunn, {J. E.} and J. Brinkmann and I. Csabai and M. Fukugita and J. Loveday",
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AU - Smolčić, V.

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AU - Pavlovski, K.

AU - Ilijić, S.

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AU - Charlot, S.

AU - Heckman, T. M.

AU - Knapp, G. R.

AU - Gunn, J. E.

AU - Brinkmann, J.

AU - Csabai, I.

AU - Fukugita, M.

AU - Loveday, J.

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N2 - We discuss the colours of 99 088 galaxies selected from the Sloan Digital Sky Survey (SDSS) Data Release 1 'main' spectroscopic sample (a flux-limited sample, r Pet <17.77, for 1360 deg 2) in the rest-frame Strömgren system (uz, vz, bz, yz). This narrow-band (∼200 Å) photometric system, first designed for the determination of effective temperature, metallicity and gravity of stars, measures the continuum spectral slope of galaxies in the rest-frame 3200-5800 Å wavelength range. We synthesize rest-frame Strömgren magnitudes from SDSS spectra, and find that galaxies form a remarkably narrow locus (∼0.03 mag) in the resulting colour-colour diagram. Using the Bruzual & Charlot population-synthesis models, we demonstrate that the position of a galaxy along this locus is controlled by metallicity and age of the dominant stellar population. The distribution of galaxies along the locus is bimodal, with the local minimum corresponding to an ∼1-Gyr-old single stellar population. The position of a galaxy perpendicular to the locus is independent of metallicity and age, and reflects the galaxy's dust content, as implied by both the models and the statistics of IRAS detections. Comparison of the galaxy locus in the rest-frame Strömgren colour-colour diagram with the galaxy locus in the Hδ A-D n(4000) diagram, utilized by Kauffmann et al. to estimate stellar masses, reveals a tight correlation, although the two analysed spectral ranges barely overlap. Furthermore, the rest-frame r - i colour (5500-8500 Å wavelength range) can be 'predicted' with an rms of 0.05 mag using the rest-frame Strömgren colours. Overall, the galaxy spectral energy distribution in the entire ultraviolet to near-infrared range can be described as a single-parameter family with an accuracy of 0.1 mag, or better. This nearly one-dimensional distribution of galaxies in the multidimensional space of measured parameters strongly supports the conclusion of Yip et al., based on a principal component analysis, that SDSS galaxy spectra can be described by a small number of eigenspectra. Furthermore, the rest-frame Strömgren colours correlate tightly with the classification scheme proposed by Yip et al. based on the first three eigenspectra. Apparently, the contributions of stellar populations that dominate the optical emission from galaxies are combined in a simple and well-defined way. We also find a remarkably tight correlation between the rest-frame Strömgren colours of emission-line galaxies and their position in the Baldwin-Phillips-Terlevich diagram. These correlations between colours and various spectroscopic diagnostic parameters support earlier suggestions that rest-frame Strömgren photometry offers an efficient tool to study faint cluster galaxies and low surface brightness objects without performing time-consuming spectral observations.

AB - We discuss the colours of 99 088 galaxies selected from the Sloan Digital Sky Survey (SDSS) Data Release 1 'main' spectroscopic sample (a flux-limited sample, r Pet <17.77, for 1360 deg 2) in the rest-frame Strömgren system (uz, vz, bz, yz). This narrow-band (∼200 Å) photometric system, first designed for the determination of effective temperature, metallicity and gravity of stars, measures the continuum spectral slope of galaxies in the rest-frame 3200-5800 Å wavelength range. We synthesize rest-frame Strömgren magnitudes from SDSS spectra, and find that galaxies form a remarkably narrow locus (∼0.03 mag) in the resulting colour-colour diagram. Using the Bruzual & Charlot population-synthesis models, we demonstrate that the position of a galaxy along this locus is controlled by metallicity and age of the dominant stellar population. The distribution of galaxies along the locus is bimodal, with the local minimum corresponding to an ∼1-Gyr-old single stellar population. The position of a galaxy perpendicular to the locus is independent of metallicity and age, and reflects the galaxy's dust content, as implied by both the models and the statistics of IRAS detections. Comparison of the galaxy locus in the rest-frame Strömgren colour-colour diagram with the galaxy locus in the Hδ A-D n(4000) diagram, utilized by Kauffmann et al. to estimate stellar masses, reveals a tight correlation, although the two analysed spectral ranges barely overlap. Furthermore, the rest-frame r - i colour (5500-8500 Å wavelength range) can be 'predicted' with an rms of 0.05 mag using the rest-frame Strömgren colours. Overall, the galaxy spectral energy distribution in the entire ultraviolet to near-infrared range can be described as a single-parameter family with an accuracy of 0.1 mag, or better. This nearly one-dimensional distribution of galaxies in the multidimensional space of measured parameters strongly supports the conclusion of Yip et al., based on a principal component analysis, that SDSS galaxy spectra can be described by a small number of eigenspectra. Furthermore, the rest-frame Strömgren colours correlate tightly with the classification scheme proposed by Yip et al. based on the first three eigenspectra. Apparently, the contributions of stellar populations that dominate the optical emission from galaxies are combined in a simple and well-defined way. We also find a remarkably tight correlation between the rest-frame Strömgren colours of emission-line galaxies and their position in the Baldwin-Phillips-Terlevich diagram. These correlations between colours and various spectroscopic diagnostic parameters support earlier suggestions that rest-frame Strömgren photometry offers an efficient tool to study faint cluster galaxies and low surface brightness objects without performing time-consuming spectral observations.

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KW - Galaxies: Seyfert

KW - Galaxies: statistics

KW - Methods: statistical

KW - Surveys

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