Stellar SEDs from 0.3 to 2.5 μm: Tracing the stellar locus and searching for color outliers in the SDSS and 2MASS

K. R. Covey, Ž Ivezić, D. Schlegel, D. Finkbeiner, N. Padmanabhan, R. H. Lupton, M. A.A. Güeros, J. J. Bochanski, S. L. Hawley, A. A. West, A. Seth, A. Kimball, S. M. Gogarten, M. Claire, D. Haggard, N. Kaib, D. P. Schneider, B. Sesar

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Abstract

The Sloan Digital Sky Survey (SDSS) and Two Micron All Sky Survey (2MASS) are rich resources for studying stellar astrophysics and the structure and formation history of the Galaxy. As new surveys and instruments adopt similar filter sets, it is increasingly important to understand the properties of the ugrizJHKs stellar locus, both to inform studies of "normal" main-sequence stars and enable robust searches for point sources with unusual colors. Using a sample of ∼600,000 point sources detected by SDSS and 2MASS, we tabulate the position and width of the ugrizJHKs stellar locus as a function of g - i color, and provide accurate polynomial fits. We map the Morgan-Keenan spectral type sequence to the median stellar locus by using synthetic photometry of spectral standards and by analyzing 3000 SDSS stellar spectra with a custom spectral typing pipeline, described in the Appendix to this paper. We develop an algorithm to calculate a point source's minimum separation from the stellar locus in a seven-dimensional color space, and use it to robustly identify objects with unusual colors, as well as spurious SDSS/2MASS matches. Analysis of a final catalog of 2117 color outliers identifies 370 white-dwarf/M dwarf (WDMD) pairs, 93 QSOs, and 90 M giant/carbon star candidates, and demonstrates that WDMD pairs and QSOs can be distinguished on the basis of their J - Ks and r - z colors. We also identify a group of objects with correlated offsets in the u - g versus g - r and g - r versus r - i color-color spaces, but subsequent follow-up is required to reveal the nature of these objects. Future applications of this algorithm to a matched SDSS-UKIDSS catalog may well identify additional classes of objects with unusual colors by probing new areas of color-magnitude space.

Original languageEnglish (US)
Pages (from-to)2398-2417
Number of pages20
JournalAstronomical Journal
Volume134
Issue number6
DOIs
StatePublished - Dec 1 2007

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loci
tracing
outlier
color
point sources
point source
quasars
catalogs
stellar spectra
giant stars
carbon stars
main sequence stars
astrophysics
photometry
resources
polynomials
histories
galaxies
filter
filters

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Covey, K. R., Ivezić, Ž., Schlegel, D., Finkbeiner, D., Padmanabhan, N., Lupton, R. H., ... Sesar, B. (2007). Stellar SEDs from 0.3 to 2.5 μm: Tracing the stellar locus and searching for color outliers in the SDSS and 2MASS. Astronomical Journal, 134(6), 2398-2417. https://doi.org/10.1086/522052
Covey, K. R. ; Ivezić, Ž ; Schlegel, D. ; Finkbeiner, D. ; Padmanabhan, N. ; Lupton, R. H. ; Güeros, M. A.A. ; Bochanski, J. J. ; Hawley, S. L. ; West, A. A. ; Seth, A. ; Kimball, A. ; Gogarten, S. M. ; Claire, M. ; Haggard, D. ; Kaib, N. ; Schneider, D. P. ; Sesar, B. / Stellar SEDs from 0.3 to 2.5 μm : Tracing the stellar locus and searching for color outliers in the SDSS and 2MASS. In: Astronomical Journal. 2007 ; Vol. 134, No. 6. pp. 2398-2417.
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abstract = "The Sloan Digital Sky Survey (SDSS) and Two Micron All Sky Survey (2MASS) are rich resources for studying stellar astrophysics and the structure and formation history of the Galaxy. As new surveys and instruments adopt similar filter sets, it is increasingly important to understand the properties of the ugrizJHKs stellar locus, both to inform studies of {"}normal{"} main-sequence stars and enable robust searches for point sources with unusual colors. Using a sample of ∼600,000 point sources detected by SDSS and 2MASS, we tabulate the position and width of the ugrizJHKs stellar locus as a function of g - i color, and provide accurate polynomial fits. We map the Morgan-Keenan spectral type sequence to the median stellar locus by using synthetic photometry of spectral standards and by analyzing 3000 SDSS stellar spectra with a custom spectral typing pipeline, described in the Appendix to this paper. We develop an algorithm to calculate a point source's minimum separation from the stellar locus in a seven-dimensional color space, and use it to robustly identify objects with unusual colors, as well as spurious SDSS/2MASS matches. Analysis of a final catalog of 2117 color outliers identifies 370 white-dwarf/M dwarf (WDMD) pairs, 93 QSOs, and 90 M giant/carbon star candidates, and demonstrates that WDMD pairs and QSOs can be distinguished on the basis of their J - Ks and r - z colors. We also identify a group of objects with correlated offsets in the u - g versus g - r and g - r versus r - i color-color spaces, but subsequent follow-up is required to reveal the nature of these objects. Future applications of this algorithm to a matched SDSS-UKIDSS catalog may well identify additional classes of objects with unusual colors by probing new areas of color-magnitude space.",
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Covey, KR, Ivezić, Ž, Schlegel, D, Finkbeiner, D, Padmanabhan, N, Lupton, RH, Güeros, MAA, Bochanski, JJ, Hawley, SL, West, AA, Seth, A, Kimball, A, Gogarten, SM, Claire, M, Haggard, D, Kaib, N, Schneider, DP & Sesar, B 2007, 'Stellar SEDs from 0.3 to 2.5 μm: Tracing the stellar locus and searching for color outliers in the SDSS and 2MASS', Astronomical Journal, vol. 134, no. 6, pp. 2398-2417. https://doi.org/10.1086/522052

Stellar SEDs from 0.3 to 2.5 μm : Tracing the stellar locus and searching for color outliers in the SDSS and 2MASS. / Covey, K. R.; Ivezić, Ž; Schlegel, D.; Finkbeiner, D.; Padmanabhan, N.; Lupton, R. H.; Güeros, M. A.A.; Bochanski, J. J.; Hawley, S. L.; West, A. A.; Seth, A.; Kimball, A.; Gogarten, S. M.; Claire, M.; Haggard, D.; Kaib, N.; Schneider, D. P.; Sesar, B.

In: Astronomical Journal, Vol. 134, No. 6, 01.12.2007, p. 2398-2417.

Research output: Contribution to journalArticle

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T1 - Stellar SEDs from 0.3 to 2.5 μm

T2 - Tracing the stellar locus and searching for color outliers in the SDSS and 2MASS

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AU - Ivezić, Ž

AU - Schlegel, D.

AU - Finkbeiner, D.

AU - Padmanabhan, N.

AU - Lupton, R. H.

AU - Güeros, M. A.A.

AU - Bochanski, J. J.

AU - Hawley, S. L.

AU - West, A. A.

AU - Seth, A.

AU - Kimball, A.

AU - Gogarten, S. M.

AU - Claire, M.

AU - Haggard, D.

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AU - Sesar, B.

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N2 - The Sloan Digital Sky Survey (SDSS) and Two Micron All Sky Survey (2MASS) are rich resources for studying stellar astrophysics and the structure and formation history of the Galaxy. As new surveys and instruments adopt similar filter sets, it is increasingly important to understand the properties of the ugrizJHKs stellar locus, both to inform studies of "normal" main-sequence stars and enable robust searches for point sources with unusual colors. Using a sample of ∼600,000 point sources detected by SDSS and 2MASS, we tabulate the position and width of the ugrizJHKs stellar locus as a function of g - i color, and provide accurate polynomial fits. We map the Morgan-Keenan spectral type sequence to the median stellar locus by using synthetic photometry of spectral standards and by analyzing 3000 SDSS stellar spectra with a custom spectral typing pipeline, described in the Appendix to this paper. We develop an algorithm to calculate a point source's minimum separation from the stellar locus in a seven-dimensional color space, and use it to robustly identify objects with unusual colors, as well as spurious SDSS/2MASS matches. Analysis of a final catalog of 2117 color outliers identifies 370 white-dwarf/M dwarf (WDMD) pairs, 93 QSOs, and 90 M giant/carbon star candidates, and demonstrates that WDMD pairs and QSOs can be distinguished on the basis of their J - Ks and r - z colors. We also identify a group of objects with correlated offsets in the u - g versus g - r and g - r versus r - i color-color spaces, but subsequent follow-up is required to reveal the nature of these objects. Future applications of this algorithm to a matched SDSS-UKIDSS catalog may well identify additional classes of objects with unusual colors by probing new areas of color-magnitude space.

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Covey KR, Ivezić Ž, Schlegel D, Finkbeiner D, Padmanabhan N, Lupton RH et al. Stellar SEDs from 0.3 to 2.5 μm: Tracing the stellar locus and searching for color outliers in the SDSS and 2MASS. Astronomical Journal. 2007 Dec 1;134(6):2398-2417. https://doi.org/10.1086/522052