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The IPHAS and VPHAS+ catalogues

The IPHAS and VPHAS+ catalogues

Talk presented at the "Milky Way Astrophysics from Wide-Field Surveys" workshop at the Royal Astronomical Society in London on 30 March 2015.

Workshop website: http://astro.kent.ac.uk/~df/gp/index.html

Geert Barentsen

April 02, 2015
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  1. The IPHAS and VPHAS+ catalogues
 A talk by Geert Barentsen

    (@GeertHub) for the RAS Milky Way Workshop in London on 30 March 2015
  2. The IPHAS and VPHAS+ catalogues
 A talk by Geert Barentsen

    (@GeertHub) for the RAS Milky Way Workshop in London on 30 March 2015
  3. Summary
 - We recently published IPHAS DR2, providing riHα photometry

    for 219 million unique sources in the North. - The first VPHAS+ multi-band catalogue is expected soon, providing ugriHα in the South.
  4. Isaac Newton Telescope (INT); 100-inch Schmidt-Cassegrain, Short for “the INT

    Photometric Hα Survey
 of the Northern Galactic Plane” Wide Field Camera;
 4 CCDs, 32 megapixel,
 0.33 arcsec/pixel.
 Survey operated entirely in competitive “open access time”.
  5. IPHAS DR2 - First quality-controlled, globally-calibrated release. - Median seeing

    1.1 arcsec. - 219 million sources (50% have SNR > 5 in all bands). - Median 5σ-limit: 21.2 (r), 20.3 (Hα), 20.0 (i). - Lists the best detection of each unique source. ! ! Barentsen et al. (2014)
  6. 0.0 0.5 1.0 1.5 2.0 2.5 3.0 r - i

    0.0 0.2 0.4 0.6 0.8 1.0 1.2 r - H↵ A0V K0V M0V M3V M4III E(B-V)=1 E(B-V)=2 E(B-V)=3 (`, b) = (180 , 3 ) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 r - i 0.0 0.2 0.4 0.6 0.8 1.0 1.2 r - H↵ (`, b) = (45 , 2 ) Galactic
 anti-centre: First
 quadrant: The r-i, r-Hα diagram Reddening (using the “a10point” quality flag)
  7. 0.0 0.1 0.2 0.3 0.4 r 0.0 0.1 0.2 0.3

    0.4 i 12 13 14 15 16 17 18 19 20 21 22 Magnitude 0.0 0.1 0.2 0.3 0.4 H↵ Poissonian magnitude uncertainties ! Barentsen et al. (2014)
  8. 0.0 0.1 0.2 0.3 0.4 |r r2 | (b) a10point

    sources 0.0 0.1 0.2 0.3 0.4 |i i2 | 12 13 14 15 16 17 18 19 20 21 22 Magnitude 0.0 0.1 0.2 0.3 0.4 |H↵ H↵2 | Photometric repeatability: σ=0.03 mag (r<18) ! Barentsen et al. (2014)
  9. Raw images Quality control Calibrated images Single-band
 source lists Multi-band


    catalogue debias, linearise, flat-correct, gain-correct, defringe, nightly zeropoint (Mike Irwin / CASU) source detection,
 photometry (Mike Irwin / CASU) cross-match,
 flag duplicates IPHAS DR2 Recalibration
  10. Derived products have also been made available, e.g. Stuart Sale’s

    3D extinction map: http://www.iphas.org/extinction
  11. All images were examined by eye: the quality of the

    data included in DR2 is excellent!
  12. 0.0 0.5 1.0 1.5 2.0 2.5 3.0 r - i

    0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 r - H↵ (b) After re-calibration 0.0 0.5 1.0 1.5 2.0 2.5 3.0 r - i 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 r - H↵ (a) Before re-calibration The initial calibration error exceeded
 0.1 mag across 9% of the footprint. using nightly standard star observations using a retrospective calibration
  13. => field edges invariably suffer from inaccurate flat and aperture

    corrections (~1% systematics) The utility of overlap regions to carry out retrospective calibration was found to be limited
  14. Ideally, surveys ought to use “random” footprints,
 e.g. simulations by

    (Holmes et al. 2012): Retrospective calibration improved
 by 1 dex!
  15. Solution: 52% of the IPHAS fields were cross-calibrated against APASS;

    overlaps were then used to correct the others. AAVSO Photometric All-Sky Survey (APASS)
 uses 20 cm f/3.6 Newtonians (8 deg2 FOV) => www.aavso.org/apass
  16. Raw images Calibrated images Single-band
 source lists Multi-band
 catalogue cross-match,


    flag duplicates VPHAS+ Master source list DAOPHOT PSF photometry flag poor fits
  17. An AstroPy-based catalogue generation tool for VPHAS+ is in an

    advanced stage at ! https://github.com/barentsen/surveytools
  18. Coordinated by Greenfield (STSci), Robitaille (Heidelberg), Tollerud (Yale). AstroPy brings

    distributed and transparent peer review to core astronomical software.
  19. Summary - IPHAS DR2: brand new release, first one to

    include thorough quality control and re-calibration. World public & ready for science! - VPHAS+: multi-band catalogue in preparation, single-band source lists already available in the ESO archive (credit: CASU). Visit www.iphas.org and www.vphas.eu for more info.