Changeset 40722
- Timestamp:
- May 7, 2019, 8:25:06 PM (7 years ago)
- Location:
- trunk/doc/release.2015/ps1.calibration
- Files:
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- 18 added
- 5 edited
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Makefile (modified) (4 diffs)
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calibration.tex (modified) (43 diffs)
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pics/A1.pdf (added)
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pics/A4.pdf (added)
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pics/DCR.example.pdf (added)
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pics/KHexample.pdf (added)
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pics/KHmap.pdf (added)
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pics/allsky.astrom.pv3.3.pdf (added)
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pics/allsky.histogram.astrom.compare.pdf (added)
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pics/allsky.photom.sigma.sm.png (added)
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pics/allsky.photom.v2.pdf (added)
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pics/astroflat.gri.v2.pdf (added)
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pics/astroflat.repair.pdf (added)
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pics/astroflat.zy.v2.pdf (added)
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pics/gaia.astrom.mean.pdf (added)
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pics/gaia.astrom.mean.png (modified) ( previous)
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pics/gaia.astrom.sigma.pdf (added)
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pics/gaia.astrom.sigma.png (modified) ( previous)
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pics/gaia.photom.v1.pdf (added)
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pics/gaia.photom.v1.png (modified) ( previous)
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pics/photflat.example.v1.pdf (added)
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pics/photom.pv3.3v4.pdf (added)
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pics/rings.v3.example.pdf (added)
Legend:
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trunk/doc/release.2015/ps1.calibration/Makefile
r40714 r40722 4 4 # remember to set \pdfoutput at the top 5 5 6 DO_BIBTEX = 16 DO_BIBTEX = 0 7 7 # remember to change from \bibliography to \input{.bbl} at the bottom 8 8 … … 13 13 all: pdf tgz 14 14 pdf: calibration.pdf 15 tgz: calibration.tgz 15 16 journal: calibration.journal.tgz 17 arxiv: calibration.arxiv.tgz 16 18 17 19 quick: calibration.quick.pdf 18 20 21 PNGPICS = \ 22 pics/gpc1.layout.pdf \ 23 pics/A1.pdf \ 24 pics/A4.pdf \ 25 pics/photflat.example.v1.png \ 26 pics/rings.v3.example.png \ 27 pics/allsky.photom.v2.png \ 28 pics/photom.pv3.3v4.png \ 29 pics/KHexample.png \ 30 pics/KHmap.png \ 31 pics/DCR.example.png \ 32 pics/astroflat.gri.v2.png \ 33 pics/astroflat.zy.v2.png \ 34 pics/allsky.astrom.pv3.3.png \ 35 pics/astroflat.repair.png \ 36 pics/allsky.histogram.astrom.compare.png \ 37 pics/gaia.photom.v1.png \ 38 pics/gaia.astrom.mean.png \ 39 pics/gaia.astrom.sigma.png 40 19 41 PDFPICS = \ 42 pics/gpc1.layout.pdf \ 20 43 pics/A1.pdf \ 21 pics/A3.pdf \ 22 pics/A4.pdf 44 pics/A4.pdf \ 45 pics/photflat.example.v1.pdf \ 46 pics/rings.v3.example.pdf \ 47 pics/allsky.photom.v2.pdf \ 48 pics/photom.pv3.3v4.pdf \ 49 pics/KHexample.pdf \ 50 pics/KHmap.pdf \ 51 pics/DCR.example.pdf \ 52 pics/astroflat.gri.v2.pdf \ 53 pics/astroflat.zy.v2.pdf \ 54 pics/allsky.astrom.pv3.3.pdf \ 55 pics/astroflat.repair.pdf \ 56 pics/allsky.histogram.astrom.compare.pdf \ 57 pics/gaia.photom.v1.pdf \ 58 pics/gaia.astrom.mean.pdf \ 59 pics/gaia.astrom.sigma.pdf 23 60 24 61 FILES = \ … … 26 63 ../inputs/code.sty \ 27 64 ../inputs/apj.bst \ 28 pics/rings.v3.example.png \29 pics/KHexample.png \30 pics/KHmap.png \31 pics/dcr.r2.g.png \32 pics/allsky.astrom.sigma.png \33 pics/gaia.photom.png \34 pics/gaia.astrom.png \35 $(PDFPICS) \36 65 calibration.tex 37 38 # pics/photflat.example.sm.png \39 # pics/allsky.photom.sigma.sm.png \40 # pics/astroflat.gri.sm.png \41 # pics/astroflat.zy.sm.png \42 66 43 67 pics/%.pdf : pics/%.ps … … 48 72 ps2pdf -dEPSCrop $< $@ 49 73 50 pdfpics: $(PDFPICS) 74 # pdfpics: $(PDFPICS) 75 51 76 calibration.pdf: $(FILES) 52 calibration.tgz: $(FILES) 77 78 calibration.journal.tgz: $(FILES) $(PDFPICS) calibration.bbl 79 calibration..arxiv.tgz: $(FILES) $(PNGPICS) calibration.bbl 53 80 54 81 include ../Makefile.Common 82 -
trunk/doc/release.2015/ps1.calibration/calibration.tex
r40714 r40722 21 21 %% NOTE: 2019 Feb versions of the figures are generated in /data/kukui.1/eugene/cal.paper.20190217 22 22 23 %\def\picdir{ /home/eugene/chipresid.20140404}24 \def\picdir{ /data/pikake.2/eugene/chipresid.20140404}23 %\def\picdir{pics} 24 \def\picdir{.} 25 25 26 26 % Pick a terse version of the title here; … … 247 247 \begin{figure} 248 248 \centering 249 \includegraphics[width=0.9\hsize,angle=0,clip]{{ pics/gpc1.layout}.pdf}249 \includegraphics[width=0.9\hsize,angle=0,clip]{{\picdir/gpc1.layout}.pdf} 250 250 \caption{Diagram illustrating layout of OTA devices in GPC1. The 251 251 blue dots mark the locations of the amplifiers for xy00 cells in … … 476 476 \end{eqnarray} 477 477 478 %% Include a description of the WCS keywords used to represent the fit elements?479 480 %% {\bf WCS Keywords} When this polynomial representation is written to481 %% the output files, a set of WCS keywords are used to define the482 %% astrometric transformation elements. It is necessary to transform the483 %% simply polynomials above into an alternate form:484 %% \begin{eqnarray}485 %% P & = & \sum_{i,j} C^P_{i,j} (X_{\rm chip} - X_0)^i (Y_{\rm chip} - Y_0)^j \\486 %% Q & = & \sum_{i,j} C^Q_{i,j} (X_{\rm chip} - X_0)^i (Y_{\rm chip} - Y_0)^j487 %% \end{eqnarray}488 489 %% \note{need to complete this discussion of the WCS keywords, both490 %% standard and non-standard, used to represent these polynomial491 %% transformations}492 493 %% \begin{verbatim}494 %% Here is a list of the keywords495 %% and the related terms from Eqns above:496 %% CTYPE1,2 : RA---WRP, DEC--WRP497 %% CTYPE1,2 : RA---DIS, DEC--DIS498 %% CRVAL1,2 : C^{L,M}_{0,0}499 %% CRPIX1,2 : X_0, Y_0500 %% PC001001 : C^{L}_{1,0}501 %% PC001002 : C^{L}_{0,1}502 %% PC002001 : C^{M}_{1,0}503 %% PC002002 : C^{M}_{0,1}504 %% PCA1XiYj : C^{L}_{i,j}505 %% PCA2XiYj : C^{M}_{i,j}506 %% \end{verbatim}507 508 478 \subsection{Cross-Correlation Search} 509 479 … … 543 513 astrometry guess for the chip. 544 514 545 %% \note{option to downweight based on photometric inconsistency : not used in PS1 analysis}546 547 515 \subsection{Pipeline Astrometric Calibration} 548 516 … … 586 554 representing the distortion. 587 555 588 %% \note{write out the math of the gradients}589 590 556 Once the common distortion coming from the optics and atmosphere have 591 557 been modeled, \ippprog{psastro} determines polynomial transformations … … 598 564 order for the final iterations. 599 565 600 %% \note{quality of the fits as a result of this stage}.601 602 566 \subsection{Pipeline Photometric Calibration} 603 604 %% \note{define / describe the robust median}605 567 606 568 After the astrometric calibration is determined, the photometric … … 671 633 Section~\ref{sec:synthdb}) was merged in. Next, the full Tycho 672 634 database was added, followed by the AllWISE database. After the Gaia 673 release in August 2016 \citep{2016AA...595A...2G}, we generated a DVO 674 database of the Gaia positional and photometric information and merged 675 that into the master PV3 $3\pi$ DVO database.635 Data Release 1 (DR1) in August 2016 \citep{2016AA...595A...2G}, we 636 generated a DVO database of the Gaia positional and photometric 637 information and merged that into the master PV3 $3\pi$ DVO database. 676 638 677 639 The master DVO database is used to perform the full photometric and … … 869 831 \end{table*} 870 832 871 %% \note{need to describe the assignment of flags, etc, for the external data sources}.872 873 833 \section{Photometry Calibration} 874 834 … … 1033 993 \subsection{Relphot Analysis} 1034 994 1035 %% \note{how many exposures are not in ubercal?}1036 1037 995 Relative photometry is used to determine the zero points of the 1038 996 exposures which were not included in the ubercal analysis. The … … 1059 1017 is taken up as an additional element of the atmospheric attenuation. 1060 1018 1061 %% \note{color-color terms between chips?}1062 1063 1019 We write a global $\chi^2$ equation which we attempt to minimize by 1064 1020 finding the best mean magnitudes for all objects and the best … … 1095 1051 rejections do not catch all cases of bad measurements. 1096 1052 1097 %% \citep[\code{PSF_QF} $< 0.85$, see][]{magnier2017.analysis};1098 %% \note{refer to the PSPHOT bad and poor psphot bits?}1099 1100 1053 After the initial iterations, we also perform outlier rejections based 1101 1054 on the consistency of the measurements. For each star, we use a two … … 1112 1065 deviation (of the measurements used for the mean) greater than 0.005 1113 1066 mags or 2$\times$ the median standard deviation, whichever is greater. 1114 1115 %% \note{is this true?}1116 1067 1117 1068 Similarly for images, we exclude those with more than 2 magnitudes of … … 1134 1085 dominates where they are present. 1135 1086 1136 % \note{do we drop this when calculating the final mean mags?}1137 % \note{do I need to present the math?}1138 1087 \begin{equation} 1139 1088 \mu = \frac{\sum m_i w_i \sigma_i^{-2}}{\sum w_i \sigma_i^{-2}} … … 1175 1124 % this is PV3.0 [pre-calibrations] 1176 1125 1126 % updated version at: 1127 % /data/kukui.1/eugene/cal.paper.images.20190217/flatplots.sh photflat.example 1177 1128 \begin{figure*}[htbp] 1178 1129 \begin{center} 1179 1130 \begin{minipage}{0.85\linewidth} 1180 \includegraphics[width=\textwidth,clip]{{ pics/photflat.example.v1}.png}1131 \includegraphics[width=\textwidth,clip]{{\picdir/photflat.example.v1}.\plotext} 1181 1132 \end{minipage} 1182 1133 \hspace{-3.0in} … … 1592 1543 1593 1544 % generate from : 1594 % /data/kukui.1/eugene/c zw.paper.images.20181130 (see .dvo)1545 % /data/kukui.1/eugene/cal.paper.images.20190217/rings.sh 1595 1546 1596 1547 \begin{figure*}[htbp] 1597 1548 \begin{center} 1598 \includegraphics[width=\hsize,clip]{{ pics/rings.v3.example}.png}1549 \includegraphics[width=\hsize,clip]{{\picdir/rings.v3.example}.\plotext} 1599 1550 \caption{\label{fig:rings.v3.example} Illustration of overlapping 1600 1551 skycells and the identification of the ``primary'' detections.} … … 1828 1779 \subsection{Photometry Calibration Quality} 1829 1780 1781 % /data/kukui.1/eugene/cal.paper.images.20190217/scatter.sh : allsky.scatter.photom 1830 1782 \begin{figure*}[htbp] 1831 1783 \begin{center} 1832 1784 %width=\hsize 1833 \includegraphics[height=\vsize,clip]{{ pics/allsky.photom.v2}.png}1785 \includegraphics[height=\vsize,clip]{{\picdir/allsky.photom.v2}.\plotext} 1834 1786 \caption{\label{fig:allsky.photom.sigma} Consistency of photometry 1835 1787 measurements across the sky. Each panel shows a map of the … … 1876 1828 18)$ millimagnitudes. 1877 1829 1830 % /data/kukui.1/eugene/cal.paper.images.20190217/kronrepair.sh : full.figure 1878 1831 \begin{figure*}[htbp] 1879 1832 \begin{center} 1880 \includegraphics[width=\hsize,clip]{{ pics/photom.pv3.3v4}.png}1833 \includegraphics[width=\hsize,clip]{{\picdir/photom.pv3.3v4}.\plotext} 1881 1834 \caption{\label{fig:photom.pv3.3v4} Sample comparison of PV3.3 and 1882 1835 PV3.4 photometry illustrating the impact of the issues identified … … 1919 1872 1920 1873 \section{Astrometry Calibration} 1921 1874 \label{sec:astrometry} 1875 1876 % /data/kukui.3/eugene/pv3.stats.20161202/mana.sh 1922 1877 \begin{figure*}[htbp] 1923 1878 \begin{center} 1924 \includegraphics[width=\hsize,clip]{{ pics/KHexample}.png}1879 \includegraphics[width=\hsize,clip]{{\picdir/KHexample}.\plotext} 1925 1880 \caption{\label{fig:KHexample} Illustration of the Koppenh\"ofer Effect 1926 1881 on OTA04. {\bf Bottom left} X-direction before correction. The solid line shows the measured … … 1933 1888 \end{figure*} 1934 1889 1935 % from: /data/kukui.3/eugene/pv3.stats.20161202/ 1936 1890 % /data/kukui.3/eugene/pv3.stats.20161202/mana.sh 1937 1891 \begin{figure}[htbp] 1938 1892 \begin{center} 1939 \includegraphics[width=\hsize,clip]{{ pics/KHmap}.png}1893 \includegraphics[width=\hsize,clip]{{\picdir/KHmap}.\plotext} 1940 1894 \caption{\label{fig:KHmap} Map of the amplitude of the 1941 1895 Koppenh\"ofer Effect on chips across the focal plane. In the … … 2077 2031 % /data/ipp094.0/eugene/pv3.cam.20150607/astrom.corrections/dcr.meas.20151203.0.fits 2078 2032 2033 % /data/kukui.3/eugene/dcr.20141205/dvo.dcr.sh : figure8 2079 2034 \begin{figure}[htbp] 2080 2035 \begin{center} 2081 \includegraphics[width=\hsize,clip]{{ pics/dcr.r2.g}.png}2036 \includegraphics[width=\hsize,clip]{{\picdir/DCR.example}.\plotext} 2082 2037 \caption{\label{fig:DCRexample} Example of the DCR trend in the 2083 2038 g-band. {\bf top:} DCR trend in the parallactic direction {\bf … … 2118 2073 % /data/ipp105.0/eugene/astrom.20170225/astroflat.20170217/astroflat.20170217.med.cam.dX.g.fits 2119 2074 2075 % last version in : 2076 % /data/kukui.1/eugene/cal.paper.images.20190217/flatplots.sh astroflat.example 2120 2077 \begin{figure*}[htbp] 2121 2078 \begin{center} 2122 \includegraphics[width=0.85\textwidth,clip]{{ pics/astroflat.gri.v2}.png}2079 \includegraphics[width=0.85\textwidth,clip]{{\picdir/astroflat.gri.v2}.\plotext} 2123 2080 \caption{\label{fig:astroflat.gri} High-resolution astrometric flat-field correction images for $gri$.} 2124 2081 \end{center} 2125 2082 \end{figure*} 2126 2083 2084 % /data/kukui.1/eugene/cal.paper.images.20190217/flatplots.sh astroflat.example 2127 2085 \begin{figure*}[htbp] 2128 2086 \begin{center} 2129 \includegraphics[width=0.85\textwidth,clip]{{ pics/astroflat.zy.v2}.png}2087 \includegraphics[width=0.85\textwidth,clip]{{\picdir/astroflat.zy.v2}.\plotext} 2130 2088 \caption{\label{fig:astroflat.zy} High-resolution astrometric flat-field correction images for $zy$.} 2131 2089 \end{center} … … 2325 2283 2326 2284 For the initial PV3 analysis, we again used the 2MASS coordinates as 2327 an external astrometric reference. After the DR1 object parameters2328 were ingested into the PSPS database, the Gaia DR1 astrometry was 2329 released \citep{2016AA...595A...4L}. This gave us the option to use2330 the Gaia positions for the external astrometric reference. We re-did 2331 the astrometric analysis and generated a Gaia-based astrometry table 2332 for the Pan-STARRS DR1. For Pan-STARRS DR2, the average object 2333 coordinates are based on the analysis using the Gaia coordinates. The 2334 Gaia DR1 coordinates used a fixed 2015 epoch. Coordinates were 2335 propagated from that epoch to the epoch for each PS1 image as 2336 described above.2285 an external astrometric reference. After the Pan-STARRS DR1 object 2286 parameters were ingested into the PSPS database, the Gaia DR1 2287 astrometry was released \citep{2016AA...595A...4L}. This gave us the 2288 option to use the Gaia positions for the external astrometric 2289 reference. We re-did the astrometric analysis and generated a 2290 Gaia-based astrometry table for the Pan-STARRS DR1. For Pan-STARRS 2291 DR2, the average object coordinates are based on the analysis using 2292 the Gaia DR1 coordinates. The Gaia DR1 coordinates used a fixed 2015 2293 epoch. Coordinates were propagated from that epoch to the epoch for 2294 each PS1 image as described above. 2337 2295 2338 2296 \subsection{Object Astrometry} … … 2347 2305 PS1 \ippstage{chip}-stage measurements were used for the astrometry 2348 2306 measurement (no stack or forced-warp measurements). If available, the 2349 2MASS and Gaia astrometry for an object was also used in the2307 2MASS and Gaia DR1 astrometry for an object was also used in the 2350 2308 calculation of the astrometry. Measurements which were kept for the 2351 2309 astrometric fit for an object were marked with the bit-flags … … 2355 2313 the bit flag \code{ID_MEAS_POOR_ASTROM}. 2356 2314 2357 If 2MASS or Gaia astrometry measurements2315 If 2MASS or Gaia DR1 astrometry measurements 2358 2316 were available for an object, {\em all} measurements for that object 2359 2317 are marked with the bit-flag \code{ID_MEAS_OBJECT_HAS_2MASS} or … … 2494 2452 \subsection{Astrometry Calibration Quality} 2495 2453 2454 % /data/kukui.1/eugene/cal.paper.images.20190217/scatter.sh : allsky.scatter.astrom 2496 2455 \begin{figure*}[htbp] 2497 2456 \begin{center} 2498 \includegraphics[width=\hsize,clip]{{ pics/allsky.astrom.pv3.3}.png}2457 \includegraphics[width=\hsize,clip]{{\picdir/allsky.astrom.pv3.3}.\plotext} 2499 2458 \caption{\label{fig:allsky.astrom.sigma} Consistency of astrometry 2500 2459 measurements across the sky. Each panel shows a map of the 2501 2460 standard deviation of astrometry residuals for stars in each 2502 2461 pixel. The median value of the standard deviations across the sky 2503 is $(\sigma_\alpha, \sigma_\delta) = ( 22, 23)$ milliarcseconds.2462 is $(\sigma_\alpha, \sigma_\delta) = (16, 16)$ milliarcseconds. 2504 2463 These values reflect the typical single-measurement errors for 2505 2464 bright stars. See discussion regarding the astrometric flat which … … 2508 2467 \end{figure*} 2509 2468 2469 % /data/kukui.1/eugene/cal.paper.images.20190217/flatplots.sh : astroflat.repair 2510 2470 \begin{figure*}[htbp] 2511 2471 \begin{center} 2512 \includegraphics[width=\hsize,clip]{{ pics/astroflat.repair}.png}2472 \includegraphics[width=\hsize,clip]{{\picdir/astroflat.repair}.\plotext} 2513 2473 \caption{\label{fig:astroflat.repair} Comparison of the 2514 2474 high-resolution astrometric flat-field images used for PV3.2 … … 2535 2495 %% filter y : 42867074 stars 2536 2496 2497 % /data/kukui.1/eugene/cal.paper.images.20190217/scatter.sh : allsky.histogram.astrom.compare 2537 2498 \begin{figure*}[htbp] 2538 2499 \begin{center} 2539 \includegraphics[width=\hsize,clip]{{ pics/allsky.histogram.astrom.compare}.png}2500 \includegraphics[width=\hsize,clip]{{\picdir/allsky.histogram.astrom.compare}.\plotext} 2540 2501 \caption{\label{fig:allsky.astro.histogram} Illustration of the 2541 2502 impact of the astrometric flat-field correction used for PV3.2 vs … … 2577 2538 photometry, we attribute this to failure of the PSF fitting due to 2578 2539 crowding. The celestial North pole regions have somewhat elevated 2579 errors in both R.A. and DEC, with some specifc structures. Some of2540 errors in both R.A.\ and DEC, with some specifc structures. Some of 2580 2541 these structures may be due to the larger typical seeing at these high 2581 2542 airmass regions, but some are due to astrometric failures which stem … … 2583 2544 Section~\ref{sec:pole.problems} for further details). Several 2584 2545 features can be seen which appear to be an effect of the tie to the 2585 Gaia astrometry: the stripes near the center of the DEC image and the2586 right side of the R.A. image. The mesh of circular outlines one the 22546 Gaia DR1 astrometry: the stripes near the center of the DEC image and the 2547 right side of the R.A.\ image. The mesh of circular outlines one the 2 2587 2548 degree scale is due to the outer edge of the focal plane where the 2588 2549 astrometric calibration is poorly determined. … … 2697 2658 2698 2659 \subsection{Comparison to Gaia} 2660 \label{sec:gaia.tie} 2699 2661 2700 2662 After the full relative astrometry analysis was performed for the PV3 … … 2704 2666 observations. Gaia DR1 objects which are bright enough to have proper 2705 2667 motion and parallax solutions are in general saturated in the PS1 2706 observations. Thus, we are limited to using the Gaia mean positions2707 reported for the fainter stars. We extracted all Gaia sources not2668 observations. Thus, we are limited to using the Gaia DR1 mean positions 2669 reported for the fainter stars. We extracted all Gaia DR1 sources not 2708 2670 marked as a duplicate from the Gaia archive and generated a DVO 2709 database from this dataset. We then merged the Gaia D VO into the PV32671 database from this dataset. We then merged the Gaia DR1 DVO into the PV3 2710 2672 master DVO database. We re-ran the complete relative astrometry 2711 analysis using Gaia as an additional measurement. We applied the2673 analysis using Gaia DR1 as an additional measurement. We applied the 2712 2674 analysis described above, applying the estimated distances to 2713 determine preliminary proper motions. The Gaia mean epoch is reported2675 determine preliminary proper motions. The Gaia DR1 mean epoch is reported 2714 2676 as 2015.0, so all Gaia measurements were assigned this epoch. We 2715 2677 wanted to ensure the Gaia measurements dominated the astrometric … … 2723 2685 even at a lower weight, helps to tile over those gaps. 2724 2686 2687 % /data/kukui.3/eugene/pv3.stats.20161022/plots.sh 2688 2725 2689 \begin{figure*}[htbp] 2726 2690 \begin{center} 2727 \includegraphics[width=\hsize,clip]{{ pics/gaia.photom.v1}.png}2728 \caption{\label{fig:gaia.photom} Comparison with Gaia 2729 photometry. {\bf Left} Mean of PS1 - Gaia , {\bf Right} Standard2730 deviation of PS1 - Gaia . For pixels with $|b| > 30$ and $\delta >2731 -30$, the standard deviation of the PS1 - Gaia mean values is 6.92691 \includegraphics[width=\hsize,clip]{{\picdir/gaia.photom.v1}.\plotext} 2692 \caption{\label{fig:gaia.photom} Comparison with Gaia DR1 2693 photometry. {\bf Left} Mean of PS1 - Gaia DR1, {\bf Right} Standard 2694 deviation of PS1 - Gaia DR1. For pixels with $|b| > 30$ and $\delta > 2695 -30$, the standard deviation of the PS1 - Gaia DR1 mean values is 6.9 2732 2696 millimagnitudes, while the median of the standard deviations is 12.4 2733 2697 millimagnitudes. The former is a statement about the consistency 2734 of the Gaia and Pan-STARRS\,1 photometry, while the latter2698 of the Gaia DR1 and Pan-STARRS\,1 photometry, while the latter 2735 2699 reflects the combined bright-end errors for both systems. } 2736 2700 \end{center} … … 2738 2702 2739 2703 Figure~\ref{fig:gaia.photom} shows a comparison between the Pan-STARRS 2740 photometry in $g,r,i$ and the Gaia photometry in the $G$-band. To2704 photometry in $g,r,i$ and the Gaia DR1 photometry in the $G$-band. To 2741 2705 compare the PS1 photometry to the very broadband Gaia G filter, we 2742 2706 have determined a transformation based on a 3rd order polynomial fit … … 2779 2743 \begin{figure*}[htbp] 2780 2744 \begin{center} 2781 \includegraphics[width=0.4 5\hsize,clip]{{pics/gaia.astrom.mean}.png}2782 \includegraphics[width=0.4 5\hsize,clip]{{pics/gaia.astrom.sigma}.png}2745 \includegraphics[width=0.48\hsize,clip]{{\picdir/gaia.astrom.mean}.\plotext} 2746 \includegraphics[width=0.48\hsize,clip]{{\picdir/gaia.astrom.sigma}.\plotext} 2783 2747 \caption{\label{fig:gaia.astrom} Comparison with Gaia 2784 astrometry. {\bf Left} Mean of PS1 - Gaia , {\bf Right} Standard2785 deviation of PS1 - Gaia . The median value of the standard2748 astrometry. {\bf Left} Mean of PS1 - Gaia DR1, {\bf Right} Standard 2749 deviation of PS1 - Gaia DR1. The median value of the standard 2786 2750 deviations is $(\sigma_\alpha, \sigma_\delta) = (4.8, 3.1)$ 2787 2751 milliarcseconds. } … … 2790 2754 2791 2755 Figure~\ref{fig:gaia.astrom} shows a comparison between the Pan-STARRS 2792 mean astrometry positions in $\alpha,\delta$ and the Gaia astrometry.2756 mean astrometry positions in $\alpha,\delta$ and the Gaia DR1 astrometry. 2793 2757 For this comparison, we have seleted all PS1 stars with Gaia 2794 measurements with $14 < i< 19$ and with at least 10 total2758 measurements with $14 < \ips < 19$ and with at least 10 total 2795 2759 measurements. For Figure~\ref{fig:gaia.astrom}, we calculate the 2796 difference between the position predicted by PS1 at the Gaia epoch2760 difference between the position predicted by PS1 at the Gaia DR1 epoch 2797 2761 (using the proper motion and parallax fit) and the position reported 2798 2762 by Gaia. For each pixel, we determine the histogram of these 2799 differences in the R.A \.and DEC directions, and calculate the median2763 differences in the R.A.\ and DEC directions, and calculate the median 2800 2764 and the 68\%-ile range. In Figure~\ref{fig:gaia.astrom}, these 2801 2765 values are plotted as a color scale. 2802 2766 2803 There is good consistency between the PS1 and Gaia astrometry. There2767 There is good consistency between the PS1 and Gaia DR1 astrometry. There 2804 2768 are patterns from the Galactic plane (though not very strongly at the 2805 2769 bulge). There are also clear features due to the PS1 exposure … … 2810 2774 statisics of the per-exposure measurement residuals 2811 2775 (Figure~\ref{fig:allsky.astrom.sigma}. The standard deviations of the 2812 median differences are ($\sigma_\alpha, \sigma_\delta) = (4 , 3)$2776 median differences are ($\sigma_\alpha, \sigma_\delta) = (4.8, 3.1)$ 2813 2777 milliarcseconds. 2814 2778 2815 2779 For a future data release, we will recalibrate the Pan-STARRS $3\pi$ 2816 astrometry using the Gaia DR2 release. The addition of Gaia-measured 2817 proper motions will obviate the need to correct for the Galactic rotation. 2780 astrometry using the Gaia DR2 release \citep{2018AA...616A...1G}. The 2781 addition of Gaia-measured proper motions will obviate the need to 2782 correct for the Galactic rotation. 2818 2783 2819 2784 \section{Polar Astrometry Issues} 2820 2821 Internal consistency testing of the PV3 stacks measurements indicated 2785 \label{sec:pole.problems} 2786 2787 Internal consistency testing of the PV3 stack measurements indicated 2822 2788 potential problems with the astrometric registration of the exposures 2823 2789 in small areas near the North Pole. These issues were originally … … 2827 2793 these anomalous sources demonstrated the presence of significant 2828 2794 misalignments between exposures; one of the worst cases is shown in 2829 Figure~\ref{fig:pole.issue.examp e}. While such sources appeared to be2795 Figure~\ref{fig:pole.issue.example}. While such sources appeared to be 2830 2796 rare, astrometric registration errors have the potential to affect 2831 2797 several different source properties: morphology and photometry in 2832 2798 addition to astrometry. Therefore we carried out an astrometric 2833 regsitration test for all skycells North of $ \delta=+70\deg$.2799 regsitration test for all skycells North of $\delta=+70\mathdegree$. 2834 2800 2835 2801 \begin{figure*}[htbp] 2836 2802 \begin{center} 2837 \includegraphics[width=\hsize,clip]{{ pics/A1}.pdf}2803 \includegraphics[width=\hsize,clip]{{\picdir/A1}.pdf} 2838 2804 \caption{\label{fig:pole.issue.example} Example of a stack source badly affected by polar astrometry failures. Source from multiple detections from skycell 2643.093.} 2839 2805 \end{center} … … 2841 2807 2842 2808 This test was based primarily on the ``original detection positions'', 2843 \ie, the positions of sources (detections) found in individual 2844 exposures as measured after each exposure's astrometric calibration, 2845 but before recalibration of the combined values to the Gaia reference 2846 frame (described in Section 7.3). We started by collecting the 2847 original detection positions (as defined above) for each skycell. To 2848 ensure good signal-to-noise ratios and minimize potential spurious 2849 detections, we used only the top quartile (in flux) of detections 2850 within each chip. We grouped these detections on a filter-by-filter 2851 basis within a radius of $ 2\farcs5 $ (10 pixels), ensuring that each 2852 group contained only one source per exposure, and retaining only 2853 groups with at least five detections; we then recorded the 2-D 2854 position dispersion for each group. The mean positions for each group 2855 were cross-correlated against the Gaia DR2 sources, showing that these 2856 were real sources and providing information on their absolute 2857 astrometry. 2858 2859 \begin{figure*}[htbp] 2860 \begin{center} 2861 % \includegraphics[width=\hsize,clip]{{pics/A2}.pdf} 2862 \caption{\label{fig:pole.issue.example} Example of a stack source badly affected by polar astrometry failures.} 2863 \end{center} 2864 \end{figure*} 2809 \ie, the positions of detections found in individual exposures as 2810 measured after each exposure's astrometric calibration, but before 2811 recalibration of the combined values to the Gaia reference frame 2812 (described in Section~\ref{sec:gaia.tie}) since that step had the 2813 opportunity to repair any astrometric failures. We started by 2814 collecting the original detection positions (as defined above) for 2815 each skycell. To ensure good signal-to-noise ratios and minimize 2816 potential spurious detections, we used only the top quartile (in flux) 2817 of detections within each chip. We grouped these detections on a 2818 filter-by-filter basis within a radius of $ 2\farcs5 $ (10 pixels), 2819 ensuring that each group contained only one source per exposure, and 2820 retaining only groups with at least five detections; we then recorded 2821 the 2-D position dispersion for each group. The mean positions for 2822 each group were cross-correlated against the Gaia DR2 sources \citep{2018AA...616A...1G}, showing 2823 that these were real sources and providing information on their 2824 absolute astrometry. 2865 2825 2866 2826 Overall, the vast majority of the detection groups thus defined have … … 2869 2829 having an internal dispersion $ > 1 $ pixel, can result from spurious 2870 2830 sources or other anomalies, and are generally rare (fewer than a few 2871 percent of al groups). However, some skycells have a significant2831 percent of all groups). However, some skycells have a significant 2872 2832 fraction ($ > 10\%$) of bad groups. Direct inspection demonstrates 2873 2833 that the incidence of bad groups is related to astrometric 2874 registration failures. Figure~\ref{fig:pole.astrom.failures} shows an 2875 example of a good and of a bad group. 2876 2877 %% [Note: the rest of this 2878 %% paragraph, and Figure A3, may be too much information for this 2879 %% paper.] It also appears that registration problems, when present, 2880 %% are not uniform within a skycell; Figure (A3) shows the difference 2881 %% between mean group position and the position of individual detections 2882 %% for all G band exposures overlapping skycell 2637.088, which has one 2883 %% of the worst-case mismatches in the g band. 2884 2885 % caption: Map of astrometric displacement for all g-band exposures 2886 % overlapping skycell 2637.088, with one of the worst astrometric 2887 % registration issues. [Optional] 2834 registration failures. 2888 2835 2889 2836 \begin{figure*}[htbp] 2890 2837 \begin{center} 2891 \includegraphics[width=\hsize,clip]{{ pics/A4}.pdf}2838 \includegraphics[width=\hsize,clip]{{\picdir/A4}.pdf} 2892 2839 \caption{\label{fig:pole.bad.histogram} Histogram of the fraction of bad groups for each skycell (red line).} 2893 2840 \end{center} … … 2895 2842 2896 2843 Bad skycells, defined as those with more than 10\% bad groups, are 2897 essentially limited to the North polar cap ($ \delta > +80 ^{\degree}$).2844 essentially limited to the North polar cap ($ \delta > +80\mathdegree$). 2898 2845 Of the 2500 skycells in this region, 164, or 6.6\%, have more than 10\% 2899 2846 bad groups; 64 of these have more than 20\% bad groups. By comparison, 2900 essentially no skycells between $ +70^\degree $ and $ +80^\degree$ have2847 essentially no skycells between $+70\mathdegree$ and $+80\mathdegree$ have 2901 2848 more than 10\% bad groups. Figure~\ref{fig:pole.bad.histogram} shows a histogram 2902 2849 of the fraction of bad groups for each skycell. … … 2904 2851 In order to have an independent validation of the impact of this 2905 2852 astrometric alignment issue, we also carried out a photometric test 2906 based on a comparison of stack tomean object photometry. In the2853 based on a comparison between stack and mean object photometry. In the 2907 2854 presence of modest registration errors, mean object photometry would 2908 2855 not be affected, as individual detection woulds have the correct … … 2917 2864 in poor stack photometry for the affected skycells. 2918 2865 2919 \note{discuss the cause of the failure due to the duplicates in the reference catalog, and the original polar astrometry failures} 2920 2921 As a result of these tests, we decided to 1) exclude from the main DR2 2922 catalogs all sources in the skycells with more than 10\% bad groups, 2923 and 2) to reprocess all such skycells with an improved procedure. The 2924 reprocessing was carried out in late 2018, and the astrometric 2925 registration test was repeated on the reprocessed exposures. The 2926 reprocessing greatly ameliorated the registration issue, as shown 2927 Figure (A4). Here the red line shows the histogram of the fraction of 2928 bad groups for each skycell {\sl before reprocessing}, while the black 2929 line refers to the results {\sl after reprocessing}. The improvement 2930 is apparent. After reprocessing, only 23 cells, instead of the 2931 original 164, exceed 10\% of bad groups, and even for these the 2932 fraction of bad groups is substantially reduced. Sources in the 2933 previously bad, now fixed skycells will be included in an upcoming 2934 partial release. 2935 2936 \note{the above is not quite accurate -- a test reprocess demonstrated 2937 partial improvement, but did not use a totally repaired ref catalog. 2938 we are running a new analysis based on a DR2-tied catalog with 2939 pristine source set.} 2866 Further investigaion revealed that the cause of these failures was an 2867 error in the internal reference catalog used for the PV3 analysis (see 2868 Section~\ref{sec:synthdb}). This reference catalog used PS1 2869 observations to generate a catalog of \grizy\ photometry tied to the 2870 2MASS astrometric system. The astrometry used for this catalog was 2871 generated using the analysis discussed in Section~\ref{sec:astrometry} 2872 to define a collection of reference stars with a coordinate system 2873 tied to 2MASS but with the higher accuracy of the Pan-STARRS 2874 measurements on small spatial scales. Unfortunately, in the vicinity 2875 of the celestial north pole, this reference catalogs was contaminated 2876 by a number of poor measurements. In this portion of the sky, the 2877 astrometric registration of the exposures is more challanging due to 2878 the degeneracy between boresite position errors and field rotation. 2879 In addition, the PS1 telescope suffers from larger pointing errors 2880 near the celestial north pole, largely for the same reason. Because 2881 of these two factors, a number of exposures near the celestial pole 2882 were included in the reference database with invalid astrometry, 2883 injecting apparently good reference stars in the database with 2884 positions displaced from the true position by 1-2 arcseconds. 2885 Sometimes a chip processed in this region would find an astrometric 2886 solution using only good reference stars. Sometimes the solution 2887 would use only bad reference stars, resulting in a chip apparently 2888 displaced from the truth position by 1-2 arcseconds. 2889 2890 To correct the astrometry failures that caused the original errors in 2891 the reference catalog, we extended the field rotation search range for 2892 the polar exposures. We also added tests to the analysis of the 2893 exposures to ensure they would not fail in a marginal way and 2894 introduce poor solutions into the calibration database. We then ran a 2895 test to confirm that we could generate good astrometry in this region 2896 with an acceptable reference catalog. 2897 2898 We first used the PV3 mean astrometry and photometry to define a new 2899 reference catalog in the assumption that the bulk of the failures 2900 would be eliminated by the astrometric recalibration. We reprocesed a 2901 section of the polar cap data using this PV3-based reference catalog 2902 and re-ran the astrometric registration test was repeated on the 2903 reprocessed exposures. The reprocessing greatly ameliorated the 2904 registration issue, as shown in Figure~\ref{fig:pole.bad.histogram}. 2905 Here the red line shows the histogram of the fraction of bad groups 2906 for each skycell {\sl before reprocessing}, while the black line 2907 refers to the results {\sl after reprocessing}. The improvement is 2908 apparent. After reprocessing, only 23 cells, instead of the original 2909 164, exceed 10\% of bad groups, and even for these the fraction of bad 2910 groups is substantially reduced. 2911 2912 To further improve the astrometric calibration reliability in this 2913 region, we have generated a new reference catalog combining the PS1 2914 PV3 photometry with astrometry from Gaia DR2 \citep{2018AA...616A...1G}. We are reprocessing all 2915 images from the region North of $+70\mathdegree$ and will provide a 2916 complete Polar Region release using the same data as used for DR2. 2917 This updated release is expected to be available from MAST near the 2918 end of summer 2019. 2919 2920 We consider skycells with more than 10\% bad groups to have been 2921 adversely affected by this problem. Uses of DR2 should be aware that 2922 the affected skycells have poor astrometry and effective image 2923 quality. However, as these images may be useful to the community, 2924 they are available from the MAST cutout server. Users who attempt to 2925 download these problem skycells will see a warning message and should 2926 avoid using the skycell images for quantitative measurements without 2927 extreme caution. Since stack measurements from these skycells are 2928 significantly damaged, the DR2 release has set the measured stack 2929 properties of these objects to a null value. Again, users should 2930 exercise caution with sources from the affected skycells. 2940 2931 2941 2932 \section{Conclusion} 2942 2933 2943 \note{WRITE THIS} 2934 The Pan-STARRS Data Release 2 provides astromtry and photometry of 2935 roughly 3 billion astronomical objects across the $3\pi$ survey 2936 region. The photometry system has been shown to be reliable across 2937 the sky at the level of (8.0, 7.0, 9.0, 10.7, 12.4) millimags in 2938 (\grizy). The median value of the measure standard deviations for 2939 stars across the sky is $(\sigma_g, \sigma_r, \sigma_i, \sigma_z, 2940 \sigma_y) = (14, 14, 15, 15, 18)$ millimags, reflecting the systematic 2941 floor on the accuracy of individual measurements of bright stars. The 2942 astrometric calibration is tied to the Gaia DR1 frame with a 2943 systematic error floor of ($\sigma_\alpha, \sigma_\delta) = (4.8, 2944 3.1)$ milliarcseconds. The median residual astrometric scatter for 2945 bright objects across the sky is 16 milliarcseconds in both R.A.\ and 2946 DEC. Caution should be used for 164 skycells in the celestial north 2947 pole regions where the reference catalog was contaminated with 2948 astrometric failures. The Pan-STARRS DR2 photometry and astrometry 2949 will be a valuable resource for many years for the astronomical 2950 community. 2944 2951 2945 2952 \acknowledgments … … 2963 2970 \ref{fig:allsky.photom.sigma}, \ref{fig:photom.pv3.3v4}, 2964 2971 \ref{fig:astroflat.gri}, \ref{fig:astroflat.zy}, 2965 \ref{fig:allsky.astrom.sigma}, and \ref{fig:astroflat.repair} from 2966 Peter Kovesi \citep[Good Colour Maps: How to Design Them.][]{2015arXiv150903700K}. 2972 \ref{fig:allsky.astrom.sigma}, and \ref{fig:astroflat.repair} are 2973 based on the matplotlib ``magma'' colormap with additional guidance 2974 from Peter Kovesi's work \citep[Good Colour Maps: How to Design 2975 Them.][]{2015arXiv150903700K}. 2967 2976 2968 2977 \bibliographystyle{apj} 2969 \bibliography{lib}{}2970 %\input{calibration.bbl}2978 % \bibliography{lib}{} 2979 \input{calibration.bbl} 2971 2980 2972 2981 \end{document}
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