MegaPipe: Supporting the CFHT Large (and Largish) programs. Stephen Gwyn Canadian Astronomy Data Centre

Transcription

1 MegaPipe: Supporting the CFHT Large (and Largish) programs

2 MegaPipe - MegaPipe has been operating since Original purpose: to stack all public MegaCam data square degrees so far

3 MegaPipe - MegaPipe has been operating since Original purpose: to stack all public MegaCam data square degrees so far Latitude Longitude

4 MegaPipe - MegaPipe has been operating since Original purpose: to stack all public MegaCam data square degrees so far Latitude Longitude

5 Preprocessing 1 square degree pointings Astrometric/photometric calibration Local background removal Resampling and combining Catalog generation

6 MegaPipe Large Programs NGVS OSSOS MATLAS LUAU CLAUDS New Horizons

7 NGVS: Next Generation Virgo Survey Challenges: - local background subtraction also removes large galaxies - global background removal done with Elixir-LSB, where possible - global background removal done with MegaPipe when Elixir-LSB not available.

8 NGVS: Next Generation Virgo Survey Challenges: - local background subtraction also removes large galaxies - global background removal done with Elixir-LSB, where possible - global background removal done with MegaPipe when Elixir-LSB not available.

9 NGVS: Next Generation Virgo Survey Challenges: - local background subtraction also removes large galaxies - global background removal done with Elixir-LSB, where possible - global background removal done with MegaPipe when Elixir-LSB not available.

10 NGVS: Next Generation Virgo Survey Challenges: - local background subtraction also removes large galaxies - global background removal done with Elixir-LSB, where possible - global background removal done with MegaPipe when Elixir-LSB not available.

11 OSSOS: Outer Solar System Origins Survey Not interested in stacks Real Time Analysis is required Astrometric accuray is key Three astrometric calibration levels: - Level 1: use SDSS or UCAC4 - Level 2: merge catalogs to build astrometric reference catalog - Level 3: make a stack covering whole field to create astrometric reference catalog Astrometric residuals typically 40 mas Current problem: long, good seeing gri wide-band images are too deep to calibrate with SDSS

12 OSSOS: Outer Solar System Origins Survey Not interested in stacks Real Time Analysis is required Astrometric accuray is key Three astrometric calibration levels: - Level 1: use SDSS or UCAC4 - Level 2: merge catalogs to build astrometric reference catalog - Level 3: make a stack covering whole field to create astrometric reference catalog Astrometric residuals typically 40 mas Current problem: long, good seeing gri wide-band images are too deep to calibrate with SDSS

13 OSSOS: Outer Solar System Origins Survey Not interested in stacks Real Time Analysis is required Astrometric accuray is key Three astrometric calibration levels: - Level 1: use SDSS or UCAC4 - Level 2: merge catalogs to build astrometric reference catalog - Level 3: make a stack covering whole field to create astrometric reference catalog Astrometric residuals typically 40 mas Current problem: long, good seeing gri wide-band images are too deep to calibrate with SDSS

14 MATLAS: Mass Assembly of early-type galaxies with their fine Structures - Originally, MegaPipe involvment minimal - Background removal and stacking with ElixirLSB with 3-pixel binning - Recently, full resolution stacks built with MegaPipe - Minor modification required relative to NGVS, due to larger dithers

15 MATLAS: Mass Assembly of early-type galaxies with their fine Structures - Originally, MegaPipe involvment minimal - Background removal and stacking with ElixirLSB with 3-pixel binning - Recently, full resolution stacks built with MegaPipe - Minor modification required relative to NGVS, due to larger dithers

16 LUAU: Legacy for the U-band All-sky Universe New u-band tricky to calibrate SDSS is unreliable in u Elixir calibration also has issues A hybrid calibration has been developed Large dithers require a tiling system to produce stacks

17 - Elixir calibration is determined by camera run - ZP can change significantly night to night, even on photometric nights

18 Comparing SDSS and Elixir Chip-to-chip zeropoint differences change run-to-run

19 Comparing SDSS and Elixir Chip-to-chip zeropoint differences change run-to-run

20 LUAU: Legacy for the U-band All-sky Universe New u-band tricky to calibrate SDSS is unreliable in u Elixir calibration also has issues A hybrid calibration has been developed Large dithers require a tiling system to produce stacks

21 CLAUDS: CFHT Large Area U-band Deep Survey - HSC tiles don't match up with MegaCam pointings - Input images were calibrated then resampled on HSC tiles - CADC data service allows retrieval of a single MegaCam extension

22 CLAUDS: CFHT Large Area U-band Deep Survey In addition to CLAUDS images, stacks include archival data from CFHTLS and other surveys Depth is very important - Careful tracing of expected depth from input images to stacks - In the end, no upgrades to MegaPipe were necessary

23 New Horizons Initial CFHT involvement was the search for a second target Astrometric catalog was used for guiding the approach into the Pluto system Photometric catalog was used instrument calibration Second target was discovered with HST, but astrometric calibration done with CFHT data First burn was done in Sept 2015 Second will be in July 2016 Astometric accuracy: 20 mas (random)

24 Processing: - Virtual Machine based - VM on demand - batch processing - Close to CFHT archive Storage: - VOspace cloud storage - store, share, publish data Usable by any CFHT astronomer

25 Summary These Large Programs are large - NGVS: 7500 images - OSSOS: 6200 images (so far) - MATLAS: 3436 images - LUAU: 7200 images (so far) Compare to CFHTLS-W: 5900 images All these Large Programs require specialized processing Looking forward to CFIS