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Surface Photometry Techniques for SDSS Images: Methods and Challenges

This presentation discusses surface photometry of SDSS images, covering available data quantities, defects observed in images, and preliminary image reduction methods. Key focus areas include the use of different photometric measurements like Pogson magnitude, PSF magnitude, and Petrosian photometry. We will also address common issues found in SDSS images, such as sky level overestimation near bright objects and artifacts caused by cosmic rays. Two recent works utilizing these techniques will be presented, providing insights into star and galaxy morphology analysis.

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Surface Photometry Techniques for SDSS Images: Methods and Challenges

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  1. Surface Photometry On SDSS images Fengshan Liu Oct. 29, in Shanghai

  2. *Outline • SDSS image data & available quantities • Defects in SDSS images & available quantities • Preliminary image reduction • Multi-color surface photometry • Applied to two recent work

  3. 1. SDSS image data & available quantities *Available quantities: • Pogson (Pogson 1856) magnitude • PSF magnitude (psfMag) • Filber magnitude (fiberMag) • Petrosian photometry (petroMag) • Model fits (e.g., devMag, expMag, ModelMag) • Shape and Morphology (stars & galaxies) • Radial Profiles

  4. *Outline • SDSS image data & available quantities • defects in SDSS images & available quantities • Preliminary image reduction • Multi-color surface photometry • Applied to two recent work

  5. 2. Defects in SDSS images & available quantities • Overestimation of sky levels in the vicinity of bright objects (e.g., Strauss et al. 2002; Mandelbaum et al. 2005) • ‘Red halo’ in the PSF wings (e.g., Michard 2002, Wu et al. 2005) • other problems (e.g., red leak to the u filter; cosmic-ray rejection, faint ghosts of saturated stars in z, see SDSS website and Stoughton et al. 2002) • Approximate circular aperture.

  6. *Outline • SDSS image data & available quantities • Defects in SDSS images & available quantities • Preliminary image reduction • Multi-color surface photometry • Applied to two recent work

  7. *Outline • SDSS image data & available quantities • Defects in SDSS images & available quantities • Preliminary image reduction • Multi-color surface photometry • Applied to two recent work

  8. 3. Preliminary image reduction

  9. SB ellip pa A3 A4 x0 B3 B4 y0

  10. *Outline • SDSS image data & available quantities • Defects in SDSS images & available quantities • Preliminary image reduction • Multi-color surface photometry • Applied to two recent work

  11. Work1 Petrosian (Petrosian 1976) parameters profiles (Kjaergaard et al. 1993; Brough et al. 2005) 76 objects : 31 cD-like & 45 ordinary

  12. Work2 Mass of SBHs (e.g., Lauer et al. 2006; Batcheldor et al. 2006;Bonta et al. 2006)) ?

  13. The End!

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