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THE MULTIWAVELENGTH SURVEY BY YALE–CHILE (MUSYC)

THE MULTIWAVELENGTH SURVEY BY YALE–CHILE (MUSYC). Author: Cardamone et al. 2010 Speaker: Guang Yang 2013.05.15. I ntroduction. Early Photometric Redshift broad-band filters (e.g. FWHM ~ 1000A for optical bands)  low accuracy

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THE MULTIWAVELENGTH SURVEY BY YALE–CHILE (MUSYC)

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  1. THE MULTIWAVELENGTH SURVEY BY YALE–CHILE (MUSYC) Author: Cardamoneet al. 2010 Speaker: Guang Yang 2013.05.15

  2. Introduction • Early Photometric Redshift broad-band filters (e.g. FWHM ~ 1000A for optical bands)  low accuracy  catastrophic outliers

  3. nuv, fuv UBVRIz (Capak 04) ACS series

  4. Medium-Bandwidth Filters • First used in COMBO-17 survey (Wolf et al. 04) • FWHM ~ 300A (optical)  z quality 1% ~ 2%  accurate rest-frame colors  capture strong emission lines detecting AGN & StarBurstGalaxy

  5. Filters in this Paper

  6. The Authors’ Work • 18-band optical medium-band photometry • Field: Extended Chandra Deep Field-South (E-CDFS, 30’×30’) • Telescope: 8m Subaru (Suprime Cam) • Analyse photometric redshift (+previous data, using EAZY)

  7. Observations • 6 runs over 2 years • 10*2k*4K CCDs (24’*27’) • Problem: small gaps • Solve: multiple exposures

  8. Data Reduction • Flat Fielding Dome Flat: pixel-to-pixel variation Sky Flat: sky background • Bias ~10 – 20 bias frame master bias frame average

  9. Image Combination • Combining images from CCDs based on a weighted average • Bad pixels: 1. IRAF 2. human eyes (also rule out some artifacts e.g. satellite trails)

  10. Final Image 

  11. Photometric Calibration • Observe ESO standard stars each night (I doubt the second term should be + !) airmass: optical path length through Earth’s atmosphere airmass coefficient (get from manual)

  12. Ancillary Data Used in z_photo calculation

  13. Photometry • Problem different seeing in different filter big aperture: sacrifice good quality img smallaperture: different fraction of light

  14. Solution: PSF matching • 12 images with narrow PSFs smooth to PSF of the BVR ∼ 0.8’’ image measured by a singlesperture • Other images

  15. Aperture Correction

  16. Source Detection • Sextractordual image mode BVR image for detection another for photometry • AUTO flux elliptical apertures (Kron 1980)

  17. Completeness Fraction of Simulated Stars Detected Luminosity function

  18. Photometric Redshift • EAzY almost default parameters (I think additional templates might help improving results) • Results

  19. Power of ‘Medium’ Filters

  20. Why? The sharp Ly α absorption line Detected!

  21. Star/Galaxy Separation • Bz’K color selection  accurate  shallow K band • Fitting stellar SED templates  less accurate  universal

  22. Comparison

  23. Rest-Frame Color

  24. Is the Red Really Red? Only ~ 20% ‘red’ are intrinsically red, others are redden by dust

  25. Reference • THE MULTIWAVELENGTH SURVEY BY YALE–CHILE (MUSYC): DEEP MEDIUM-BAND OPTICAL IMAGING AND HIGH-QUALITY 32-BAND PHOTOMETRIC REDSHIFTS IN THE ECDF-S Carolin N. Cardamone et al. The Astrophysical Journal Supplement Series, 189:270–285, 2010 August

  26. Thanks!

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