The First Release of AST3 point source catalog from Dome A, Antarctica in 2012 MA Bin, WEI Peng, SHANG Zhaohui, LIU Qiang, HU Yi (NAOC) 973 课题二 AST3 Xuyi

Outline 1. Introduction to data 2. Data reduction 3. Importing catalogs to database 4. Query AST3 data on China-VO 5. Site testing results from AST3

1. Introduction to Data AST3-1 pilot obs. from 20 Mar to 7 May, k x 5k image, 1”/pixel, 4.3 sq. degree, median FWHM ~ 3”.9 Num of fieldsSky coverage (deg 2 ) Num of frames (good/total) exptime (sec) LMC+SMC62~250687/71960 SN Survey496~ / Num of frames (good/total)exptime (sec) LMC-center4184/ Transit3158/339830, 60 HD /71720, 30, 60 HD /66120, 30 HD /145310, 20, 30 HD /59210, 20

2. Data reduction CCD cross-talk correction Dark current correction (Ma et al. 2014) Flat-fielding (Wei et al. 2014) Bad pixel mask Photometry (SExtractor) Astrometry (Scamp) Magnitude calibration to APASS Relative calibration for time series images

Dark current correction Deriving dark frame from obs. images background ~ 620ADU, -41 ℃ Raw RMS ~ 56 ADU Corrected by lab dark RMS ~ 45 ADU Corrected by derived dark RMS ~ 24 ADU

Astrometry precision a (280.4, -73.0) FWHM 2.8”, BACKGROUND 550ADU, t_CCD -40C SCAMP ref. cat: PPMX (~0.04”) ΔRA RMS ~ 0.09”; ΔDEC RMS ~ 0.13”

Photometric precision Δmag between a and a Scatter of Δmag as photometric error 5-σ :19mag, mag_err ~ 3mmag at bright end

Magnitude calibration APASS: The AAVSO Photometric All-Sky Survey, in BVgri bands down to 17mag. Compared to SDSS, the spatial uniformity of APASS i-mag is < 0.1mag for 95% area. i-mag = -2.5log(flux/t) + zp - extinction For 3,000 SNsurvey images, the maximum i+2.5log(flux/t) is regarded as zp (no extinction) : zp = The reference images of time series fields are calibrated to APASS, then the rest are calibrated to the ref to derive high quality light curves.

3. Importing catalogs to database Developed by Tianjin Univ. Catalog import: cross-match by (ra, dec) Time cost: 1.4ms per source, independent on number of known stars (from 0 to 1M, 10M) -- bottleneck on inserting records rather than cross-match 30sec for typical SNsurvey images (~ 20k sources/image) sec for dense fields (>300k sources/image) – 10 days for 3-4 k images NAOC-TJU team is improving it

Exporting LCs to individual files, updating ra, dec, mag with mean value, & mag_rms. Num of sourcesNum of sources with >50 records SNsurvey12,768,934- LMC+SMC3,396,185- LMC-center3,535,982819,282 Transit2,332,920764,279 HD ,765137,206 HD ,190148,798 HD ,15266,284 HD ,07041,578

4. Query AST3 data on China-VO With the help of Dr. HE Boliang & Dr. FAN Dongwei (NAOC), AST3 data are released on Chinese Astronomical Data Center: vo.org/ vo.org/ This release consists of three parts: corrected images and catalogs; survey photometry; light curves (for sources with > 50 records).

FITS: MJD, X, Y, mag, mag_err, fwhm, flags … Results: download; save to VOSpace, and access in Virtual machine of AstroCloud

Example of LCs

Saved data in MyVOSpace

Access & analysis the data in AstroCloud

Research on these data Wang L.-Z. et al. in prep

Currently AST3 data are private for AST3 collaborators (NAOC, PMO, THU, NJU, BNU, PRIC), but will be public soon. Note: the data are not perfect since they were from commissioning phase, nor is the data processing (some instrument effects are not well corrected).

5. Site testing results from AST3 Sky brightness: from ADU/s to mag/arcsec 2, dependant on APASS accuracy. Sky brightness in SNsurvey: median 19.5, max 20.2, not normalized to zenith (+ ~0.1 mag) AST3-1 stopped before the darkest time Zou et al. (2010)

Transparency Compared to CSTAR, AST3 observed 100x more area, but much less time. SNsurvey: zero-point variation compared to APASS i-mag = -2.5log(flux/t) + zp - extinction Time series fields: compared to ref images Median extinction: 0.23 mag (CSTAR: 0.1 mag) AST % Zou et al. (2010)

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