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Anomalously Blue Elliptical Galaxies in the Sloan Survey

Anomalously Blue Elliptical Galaxies in the Sloan Survey. Curtis Mitchell Department of Physics University of North Texas March 31, 2005. Mentor: Dr. Mike Fanelli, UNT Collaborators: Dr. Pam Marcum, TCU & NASA Headquarters Dr. Christian Aars, San Angelo State U. Galaxies.

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Anomalously Blue Elliptical Galaxies in the Sloan Survey

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  1. Anomalously Blue Elliptical Galaxies in the Sloan Survey Curtis Mitchell Department of Physics University of North Texas March 31, 2005 Mentor: Dr. Mike Fanelli, UNT Collaborators: Dr. Pam Marcum, TCU & NASA Headquarters Dr. Christian Aars, San Angelo State U.

  2. Galaxies • Elliptical galaxies are on the left side of the Hubble “tuning fork” Edwin Hubble (1889-1953) Hubble’s Galaxy Classification Scheme

  3. Stars • Formed when interstellar gas and dust clouds collapse and begin fusing hydrogen into helium • Wide variations in mass, color, and size exist Sagittarius Star Cloud

  4. Star-Forming Systems • Optically appear blue • Luminosity dominated by OB-type stars NGC 3310 NGC 2997

  5. Blueness • OB stars lie along the upper end of main sequence • Mark the location of recent star formation Hertzsprung-Russell Diagram NGC 3603

  6. Blue Galaxies • “Starburst” galaxies • Causes of star formation • Galactic interactions NGC 4038/4039 NGC 4314

  7. Typical Ellipticals • “Old” red galaxies • Little or no star formation in the last several billion years • Spherically shaped M 49 M 87

  8. Galactic Interactions • Unlike stellar evolution, interactions are important to galactic evolution NGC 2207 & IC 2163

  9. Origin of Ellipticals • Origins not clear • Most likely formed from galactic mergers • Early ellipticals possibly came from collapsing proto-galactic clouds Compact Group NGC 4038/4039

  10. Blue Ellipticals • Unusual objects • Probably late-stage mergers • Stars have “settled down” • Using up remaining gas and dust NGC 3921

  11. Isolated Systems • Merger and collapse scenarios can be tested by looking for isolated ellipticals • Most ellipticals are in dense galactic environments KIG 557

  12. Isolated Ellipticals • Marcum, et al examined a sample of nine isolated ellipticals • Contained two blue systems and two red, normal systems (possibly oldest pristine galaxies in universe)

  13. Questions • What is the nature of the blue systems? • How do these objects fit into an evolutionary sequence?

  14. Sloan Digital Sky Survey • Contains luminosities and positions for 100 million plus objects • Detailed mapping of one quarter of the sky • We will use the Sloan Survey to search for blue ellipticals SDSS Survey Telescope (2.5 meters)

  15. Sloan Information • SDSS will provide ID, redshifts, images, and spectra for up to a million galaxies Sloan Filters: Survey Telescope Primary Mirror

  16. Search Criteria • We will look for objects meeting the blueness and shape criteria

  17. Research Method • Data mining • New branch of research: Earth Sciences: Life Sciences: Astronomy:

  18. Search Example • Image of Haro 2 retrieved from Sloan Sky Server • Absolute blue magnitude ~ -18 • (B-V) color = +0.45 (typical E’s are +0.9 to 1.0) • Class: intermediate luminosity elliptical with a blue core, probably with a starburst nucleus

  19. Sources • Animation • http://burro.astr.cwru.edu/JavaLab/ Images Anglo-Australian Observatory NOAO (National Optical Astronomy Observatory) Hubble Space Telescope Literature R. Michard and P. Prugniel, “Peculiarities and Populations in Elliptical Galaxies” Astronomy and Astrophysics Vol. 423 N. 3 L.M. Buson, F. Bertola, A. Bressan, D. Burstein, and M. Cappellari, “Is the giant elliptical galaxy NGC 5018 a post-merger remnant?” Astronomy and Astrophysics v. 423 N. 3 F. Bournard, F. Combes, and C.J. Jog, “Unequal-mass galaxy merger remnants: Spiral-like morphology but elliptical-like kinematics” Astronomy and Astrophysics, V. 418 N. 2 P.M. Marcum, C.E. Aars, M.N. Fanelli, “Early-Type Galaxies in Extremely Isolated Environments: Typical Ellipticals?” The Astronomical Journal, Vol. 127 pp. 3213-3234 Sloan Web Page: www.sdss.org

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