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| COMBO-17 | |
|---|---|
| Name | COMBO-17 |
| Type | Astronomical Survey |
| Location | La Silla Observatory, Cerro Tololo Inter-American Observatory |
| Wavelength | Optical |
| Start date | 1999 |
| End date | 2004 |
| Principal investigator | Klaus Meisenheimer |
| Telescopes | 2.2-metre Max-Planck-ESO telescope, MPG/ESO 2.2-m telescope |
| Instruments | Wide-field imager |
| Data products | Photometric catalogs, redshift estimates, spectral energy distributions |
COMBO-17 COMBO-17 was a medium-band optical imaging survey that produced multi-colour photometry and photometric redshifts across several extragalactic fields. Led by Klaus Meisenheimer and collaborators at institutions such as the Max Planck Institute for Astronomy, the survey targeted deep fields including the Chandra Deep Field South, Abell 901/902, and the Extended Groth Strip to study galaxy evolution, active galactic nuclei, and large-scale structure. Its multi-filter strategy influenced follow-up projects like ALHAMBRA, COSMOS, and COMBO-17-inspired medium-band efforts.
COMBO-17 aimed to bridge broadband surveys like Sloan Digital Sky Survey and narrowband programs like Sloan Digital Sky Survey II by using 17 optical filters to derive low-resolution spectral energy distributions. Observations used the MPIA-backed wide-field imager on the 2.2-metre Max-Planck-ESO telescope at La Silla Observatory and targeted fields previously observed by Hubble Space Telescope, Chandra X-ray Observatory, and XMM-Newton. The survey delivered catalogs cross-matched with datasets from VLT, Subaru Telescope, and Spitzer Space Telescope to enable multiwavelength studies of sources from local analogues to high-redshift galaxies.
The filter set combined 12 medium-band and 5 broadband filters designed to sample spectral features such as the 4000 Å break and emission lines common to objects studied by Sloan Digital Sky Survey, 2dF Galaxy Redshift Survey, and DEEP2 Redshift Survey. The imager was mounted on the MPG/ESO 2.2-m telescope and used a mosaic CCD focal plane similar to instruments on Canada–France–Hawaii Telescope and Subaru Suprime-Cam. The survey strategy took inspiration from surveys like Hubble Deep Field, GOODS, and CFHT Legacy Survey, optimizing depth and area to study populations found in Hubble Ultra Deep Field and COSMOS.
Observations spanned multiple seasons and coordinated with campaigns involving Very Large Telescope, Keck Observatory, and Gemini Observatory for spectroscopic calibration. Image reduction reused pipelines comparable to those developed for SDSS, including bias correction, flat-fielding, astrometric calibration referenced to USNO, and photometric calibration tied to standards used by Landolt. Source detection employed software akin to SExtractor and catalogs were cross-matched with X-ray catalogs from Chandra and infrared catalogs from Spitzer Space Telescope and WISE. Photometric redshifts were computed through template fitting similar to methods in HyperZ and Le Phare, calibrated against spectroscopic redshifts from VLT and Keck programs such as VVDS and DEEP2.
COMBO-17 produced robust photometric redshifts enabling studies of luminosity functions and color bimodality across redshift ranges probed by surveys like 2dF Galaxy Redshift Survey and SDSS. Key findings included measurements of galaxy evolution in fields overlapping studies by Hubble Space Telescope programs and constraints on the evolution of the red sequence and blue cloud akin to results from DEEP2 and VVDS. The survey identified numerous active galactic nuclei through color selection consistent with X-ray detections from Chandra X-ray Observatory and XMM-Newton, enabling comparisons with AGN demographics from Sloan Digital Sky Survey quasar catalogs. COMBO-17 data informed weak-lensing mass reconstructions in the Abell 901/902 region, complementing studies by HST and ground-based lensing surveys such as those conducted with the Subaru Telescope and CFHT.
Catalogs, photometry, and photometric redshift catalogs were released to the community and archived in formats compatible with services like the Centre de Données astronomiques de Strasbourg and virtual observatory standards. Data products were cross-referenced with public spectroscopic datasets from VVDS, DEEP2, and SDSS to facilitate external validation and follow-up proposals to facilities such as VLT, Keck Observatory, and Gemini Observatory. The releases supported multiwavelength cross-matching with surveys from Spitzer Space Telescope, Chandra X-ray Observatory, GALEX, and WISE.
COMBO-17 influenced subsequent medium-band and photometric-redshift surveys including ALHAMBRA, PAUS, and COSMOS, shaping strategies for filter selection and calibration used by projects on facilities like Subaru Telescope and VLT. Its catalogs have been cited in studies of galaxy formation, AGN demographics, and large-scale structure, complementing spectroscopic programs such as VVDS and DEEP2. Instrumentation and pipeline lessons contributed to survey planning for initiatives involving LSST, Euclid, and future missions that integrate multi-filter photometry with spectroscopy. The survey’s datasets remain a resource for cross-comparison with archival observations from Hubble Space Telescope, Chandra X-ray Observatory, Spitzer Space Telescope, and ground-based facilities.
Category:Astronomical surveys