This is the "readme" file of the third U.S. Naval Observatory CCD Astrograph Catalog, UCAC3. This data release is available free of charge on a double sided DVD or through astronomical data centers.
UCAC3 is a compiled, all-sky star catalog covering mainly the 8 to 16 magnitude range in a single bandpass between V and R. Positional errors are about 15 to 20 mas for stars in the 10 to 14 mag range. It is supplemented by proper motions and SuperCosmos and 2MASS photometric data, as well as various flags.
The proper motions of bright stars are based on about 140 catalogs, including Hipparcos and Tycho, as well as all catalogs used for the Tycho-2 proper motion construction. Proper motions of faint stars are based on a re-reduction of early epoch SPM data (-90 to -10 deg Dec) plus Schmidt plate data from the SuperCosmos project (down weighted due to systematic errors of order 100 mas). The proper motions of faint stars (R >= 13.5) therefore should be used with caution. The unpublished plate measure data from the AGK2, the Hamburg Zone Astrograph, the USNO Black Birch Astrograph, and the Lick Astrograph have considerably contributed to improve proper motions for stars mainly in the 10 to 14 mag range (down to the UCAC3 limit for Lick data); however, these data do not cover all sky.
UCAC3 features a number of major differences with respect to UCAC2:
A UCAC4 release is anticipated in the future. The plan is to utilize a new reduction of the NPM plate material and benefit from global iterative solutions to further reduce possible systematic (zonal) errors and provide a strong link to the extragalactic reference frame. The UCAC4 release also might make individual positions at observational epochs public, and may serve pixel data as well.
Additional details will be published in the upcoming release paper (Zacharias et al. 2009) and in several technical papers describing details of the reduction procedures and results. For the latest updates see http://www.usno.navy.mil/usno/astrometry . The release paper should be sited whenever UCAC3 data is utilized. Requests for the data DVD should be sent to firstname.lastname@example.org, technical questions can be addressed to email@example.com . The DVD will be sent to all addresses on the UCAC2 distribution list as soon as our resources allow.
The UCAC is an observational program, using the U.S. Naval Observatory Twin Astrograph and a 4k by 4k CCD camera, covering just over one square degree per frame with a scale of 0.9"/pixel. The red-corrected, 20 cm aperture, 5-element lens of the astrograph provides a 9 degree (diameter) field of view (designed for photographic plates), thus only a fraction is utilized with our CCD camera, centered on the optical axis.
The CCD is a thick, Kodak device with 9 micrometer pixel size. The camera, made by Spectral Instruments, is Peltier cooled to -18 C. The raw data are severely affected by a low charge transfer efficiency (CTE) of our otherwise cosmetically excellent CCD chip. To mitigate this problem, a relatively warm operating temperature is used, causing a significant dark current.
Observations started in January 1998 at Cerro Tololo Interamerican Observatory (CTIO) in Chile, where the entire southern sky and about half of the northern sky were observed. In October 2001 the instrument was moved to the Naval Observatory Flagstaff Station (NOFS) in Arizona where it completed the northern sky in 2004.
A 2-fold, center-in-corner overlap pattern was adopted on a 0.5 degree grid, starting at the South Celestial Pole. Each field was observed with both a long (100 to 150 sec) and a short (20 to 30 sec) exposure. Extensive quality control routines led to the rejection of over 15% of the frames taken. All raw (pixel) data were saved and continue to be archived.
Observations were made in a single bandpass (579-642 nm), thus the UCAC magnitudes are between Johnson V and R. No attempt has been made to obtain high quality, photometric data from the CCD observations. In fact, observations were made during nights with thin cirrus clouds.
The telescope was actively guided with an ST-4 autoguider mounted behind the second, visually-corrected lens of the twin-astrograph. Operation was automated using a PC and a single board computer. An HP-Unix workstation was used for on-line reductions to obtain quality control statistics in near real-time.
The UCAC3 positions of the CCD observations are based on the Tycho-2 reference stars, similar to the UCAC2 catalog. However, the 2MASS was utilized to probe for systematic errors in the CCD data, particularly magnitude equations and coma-like errors caused by the poor CTE of the detector. Image centroiding is based on a modified Lorentz profile model which matches the observed PSF better than a Gaussian function. For details, please see upcoming journal papers.
Pixel processing included double star fits and real aperture photometry. "Flip" observations (telescope on West and East side of pier for same calibration field) were utilized to fix the overall magnitude equations.
Saturated images of stars were propagated through the output catalog, so UCAC3 contains many more bright stars than UCAC2. However positional results are not as reliable as for unsaturated images and the user is urged to pay attention to flags and the meaning of various data columns.
Proper motions of bright stars (R ~8 to ~12.5) were derived using a combination of ground-based photographic and transit circle catalogs, and included satellite observations from the Hipparcos and Tycho-2 catalogs. In addition, the U.S. Naval Observatory measured about 5000 astrograph plates on the StarScan machine to derive about 9 million positions for stars mainly in the 10 to 14 magnitude range, including the complete set of AGK2 (Bonn and Hamburg zones, +90 to -2.5 deg Dec).
For the faint stars (~12.5 to ~16.5), data from the first epoch plates of the Yale Southern Proper Motions (SPM, van Altena et al. 1999) are utilized. These plates were measured on the Precision Measuring Machine at USNO Flagstaff Station by D. Monet. A complete re-reduction of the data were performed in a joint USNO - Yale University effort utilizing the StarScan pipeline for the pixel reductions and the Yale software to obtain RA,Dec coordinates. Because the re-reduction of the NPM data is still in progress, the SuperCosmos data (Hambly et al. 2001a,b,c) were included in UCAC3 to provide proper motion coverage of faint stars, particularly in the north. For this purpose stars with magnitude R <= 17 and all sky were extracted from a copy of the SuperCosmos "source" data. Due to zonal (plate pattern) systematic errors in the range of 50 to 200 mas, as compared to 2MASS data, the SuperCosmos positions at their mean epoch were downweighted with an additional 100 mas RMS error contribution. Other catalogs were handled similarly, with somewhat lower additional error contributions. The number of stars in UCAC3 which are also in major other catalogs used for the proper motions is as follows:
numb.stars cat ID and name ------------------------------------------ 65392 1 Hipparcos 2386607 2 Tycho-2 4098873 3 AC2000 270823 4 AGK2 Bonn 960074 5 AGK2 Hamb 4320925 6 ZA 2970383 7 BY 1043857 8 Lick 85563642 9 SuperCosmos 51112855 10 SPM YSJ1 51297 - high proper motion stars from external catalogs 98114307 - 2MASS 100766420 - all stars in UCAC3
For more details please see the upcoming journal papers.
It is hoped that this approach reduced systematic errors in UCAC3 proper motions of faint stars as compared to the procedures adopted for UCAC2.
There are 51297 tagged previously known high proper motion stars in the UCAC3 release. While we have made an effort to identify previously known high proper motion stars, the list is not comprehensive. The high proper motion stars were identified by utilizing known proper motion catalogs to match with our UCAC3 positions. In all cases the proper motion given for each star come from the source catalog. In the North we used the LSPM-North Catalog (Lepine+ 2005) of 61977 new and previously known high proper motion stars having proper motions greater than 0.15"/yr. In the South we used many smaller surveys along with the Revised NLTT Catalog (Salim+, 2003), which produced 17730 unique high proper motion stars greater than 0.15"/yr. In chronological order, the smaller southern surveys used include: seven papers covering various portions of the southern sky by Wroblewski and collaborators (Wroblewski & Torres 1989, 1991, 1994, 1996, 1997; Wroblewski & Costa 1999, 2001), (2) UK Schmidt Telescope survey plates of 40 survey fields by Scholz and collaborators (Scholz et al. 2000), (3) The Calan-ESO survey (Ruiz et al. 2001) (4) SuperCOSMOS-RECONS proper-motion survey of the entire southern sky (Henry et al. 2004; Subasavage et al. 2005a, 2005b; Finch et al. 2007), (5) the Southern Infrared Proper-Motion Survey (SIPS; Deacon et al. 2005) and (7) Lepine's SUPERBLINK survey of a portion of the southern sky (Lépine 2008).) Identified images of high proper motion stars in UCAC data were cut from the remaining pipeline and reduced separately. Results for those stars were then added in a later stage of the reductions. This avoids creating duplicate entries in UCAC3.
The computation of proper motions is performed similarly to the procedure used for the UCAC2 and the Tycho-2 catalogs. All input catalogs were reduced to the ICRF utilizing Hipparcos data or some denser, interim catalog that follows the system of Hipparcos. Standard errors for each position are estimated. These error estimates are used as weights to compute a mean position and proper motion, which utilizes a weighted, least-squares adjustment procedure. Error estimates of UCAC3 astrometry are provided.
Errors in proper motions of the bright stars (to R ~12) run from about 1 to 3 mas/yr mainly due to the large epoch spans involved. For the fainter stars using SPM data, typical errors are 2 to 3 mas/yr, while with SuperCosmos early epoch data alone proper motion errors are about 6 to 8 mas/yr (as a conservative estimate).
Contrary to UCAC2, not all stars in UCAC3 have proper motions. Stars made it into the UCAC3 release catalog if any one of the following applies:
A master list of exactly 139,134,800 mean positions from CCD data was matched against the various other catalogs, resulting in exactly 100,766,420 objects actually provided in this UCAC3 data release. Of these 51,297 are identified, known high proper motions stars.
UCAC3 is an all-sky catalog with at least about 40 stars per square deg anywhere on the sky. The average density of this catalog is over 2000 stars per square deg.
UCAC3 is more complete than UCAC2, including previously omitted "problem" stars and double stars, many of which could be new discoveries. A paper is in preparation about a sample of new double stars found in UCAC3 and the rate of confirmation by speckle observations. The separation limit for double stars in UCAC3 varies as function of brightness of the components and brightness difference. However, some doubles with separations of only 1 arcsec in UCAC3 have been confirmed as real. Stars fainter than about R = 10 and separations larger than 2 arcsec are well covered.
UCAC3 also contains observations of some bright stars, as they happened to make it through the pipeline. However, UCAC3 is not supplemented by a bright star catalog and is incomplete at around magnitude R=7.5 and brighter. Some positions are based on a center-of-mass centroiding when the least-squares fit did not succeed. The positions of those stars (number of used images, nu = 0) are not reliable and are given only to indicate a problem area in this area of the sky.
If a star's proper motion was computed to be larger than 300 mas/yr in either coordinate, but it was not found in a high proper motion star catalog, the proper motion was set to zero and only the mean observed CCD position is given in UCAC3.
Over 95 million stars in UCAC3 have a computed proper motion; for 45.4 million of these the proper motion is based on only 2 epochs, while for 49.5 million stars at least 3 epochs were available.
If the computed position error of a star exceeds 500 mas in either coordinate it was set to 500 mas but the star was kept, if at least 2 observations from different CCD observations were matched or the star is either in the 2MASS, SPM or SuperCosmos data files. Similarly, the error in proper motion was truncated to 50 mas/yr but respective stars kept in UCAC3 by the same criteria as for large positional errors. Obviously all large error objects need to be handled with caution, and some of these will just be fake. This approach, different to UCAC2, was taken in order to drive up the completeness of UCAC3 at the expense of slightly greater contamination. In particular, the larger limits in errors deemed acceptable for UCAC3 accommodate the fainter limiting magnitude, which was possible mainly due to superior handling of dark subtraction in the pixel data. This allowed many low signal-to-noise, real stars to enter the catalog, although with expected larger random errors.
The astrometry provided in UCAC3 is on the Hipparcos system, i.e. the International Celestial Reference System (ICRS), as represented by the Tycho-2 catalog. Any possible deviations of the Tycho system with respect to Hipparcos or the extragalactic radio reference frame are under investigation for UCAC4.
Positions in UCAC3 are given at the standard epoch of Julian date 2000.0, thus the UCAC3 is a compiled catalog. In order to be able to calculate positional errors at any epoch, the central epoch, i.e. the weighted mean epoch of the data (UCAC + early epoch) is given. At the central epoch (which varies from star to star and is also different for RA and Dec) the positional error has its smallest value, the one given in the catalog for "sigma position". In most cases this central epoch will be close to the UCAC observational epoch due to the relatively large weight given to the UCAC observations. However, a fair number of stars have a vastly different mean epoch, ranging back to about 1900.
The proper motions are given at the central epoch. Positional errors of stars increase according to the errors in the proper motions when going forward or backward in time from the central epoch.
UCAC3 covers the magnitude range of about R = 7.5 to 16.3 in a 579-642 nm bandpass. This is between visual (V) and red (R). The limiting magnitude can vary by about +-0.3 mag. The bright magnitude cut-off varies even more, depending on sky conditions at the time of observation.
UCAC3 gives centroid fit-model magnitudes as well as aperture photometry derived from the new pixel data reductions. Systematic errors in these magnitudes are believed to be below 0.1 mag, which is a significant improvement over the UCAC2 release. Tycho-2 stars, except for the faint end, were used to perform differential photometric reductions, CCD frame by frame, including a zero-point and a linear color term. However, UCAC observations were performed in non-photometric sky conditions. Mean magnitudes were derived from CCD frames with indications of "good photometric quality", which is about 50% of the observations.
For convenience to the user, the UCAC3 observational data are supplemented with plate photometry (B, R, I) from the SuperCosmos project (Hambly et al 2001), as well as with new, IR photometry from the Two Micron All Sky Survey, 2MASS (Scrutsky 2006). In addition to the J, H, and K_s magnitudes, rounded errors and some flags are provided as well. For more details see http://www-wfau.roe.ac.uk/sss/ and http://www.ipac.caltech.edu/2mass/releases/allsky/ .
The UCAC3 contains some galaxies, particularly at the faint end. No flag indicating a galaxy or star has been derived from the CCD pixel data; however, a cross reference to the LEDA galaxies (Paturel et al. 2005) and the 2MASS extended source catalog (Skrutskie et al. 2006) has been made and corresponding information is put into the UCAC3 release.
Observations of asteroids have been identified and taken out of the main UCAC3 catalog. Individual epoch observations of about 1000 asteroids at multiple epochs have been prepared for publication, but are not part of the UCAC3 release. The observing schedule explicitly avoided all minor planets brighter than about R = 12, except for special observing campaigns to derive masses of asteroids.
Only some basic access code is included with this release to illustrate the data format and allow conversion of the main binary files to ASCII tables. It is anticipated that 3rd party companies specialized in providing interfaces between various star catalogs and the user will integrate UCAC3 data into their products, as has been the case for UCAC2.
The main catalog data are arranged in declination zones of 0.5 degree width, with zone number 1 starting at the South Pole and increasing toward north. There is a separate file for each of the 360 zones. Records in the individual data files are sorted by right ascension. Each record contains the data for one star, 84 bytes of binary integers.
Official UCAC3 star ID numbers should be utilized for identification purposes and for communication with the UCAC team. The main identifier is the running star number in the CCD mean position data (MPOS number) which is provided on the UCAC3 individual star records as the last 4-byte integer item. This number spans the range of 3 to 140051297 but includes gaps for stars which did not make it into the release. MPOS numbers over 140 million identify high proper motion stars, which have been handled differently in the pipeline and were merged at a later stage into the release.
Alternatively, a unique running star ID number without any gaps can be generated on the fly, counting stars along zones from south to north and along RA within each zone, similarly to what was recommended for UCAC2.
ID = n0 + running star number in zone z
where z is zone number where the star in question is located (1 to 360; zone 1: -90 to -89.5 decl., ...), n0 is the largest star ID number of the previous zone and ID is this official UCAC3 star ID number. A table is provided listing some statistics of zones, which include this n0 number.
If needed, this 9-digit star ID number should be given in connection with the IAU sanctioned acronym of this project and this data release number, such as "3UCAC100200300". The star ID number runs from 000000001 to 100766420. Leading zeros are to be used to fill 9 digits in the star name.
The DVD does not contain sub-directories; all information is provided in files on the top level for each side of the double-sided DVD.
The main catalog data are contained in zone files "z001" to "z360". Each zone is 0.5 degree wide, beginning at the south celestial pole. The format of these binary data files is explained below.
readme_u3 = this file table_zones = table listing info for each zone u3index.asc = index file for each 0.1 hour in RA, ASCII text file u3index.unf = index file for each 0.1 hour in RA, unformatted binary u3read.f = Fortran code to read UCAC3 zone files u3read.dat = sample data ASCII output file generated with u3read.f
sample code to illustrate data format (Fortran 77)
* items to read from input files INTEGER*4 i, ra,spd, pmrac,pmdc, id2m, rn INTEGER*2 im1,im2,sigmag, sigra,sigdc, cepra,cepdc,sigpmr,sigpmd . ,jmag,hmag,kmag, smB,smR2,smI INTEGER*1 objt,dsf, na1,nu1,us1,cn1, clbl,qfB,qfR2,qfI INTEGER*1 icqflg(3), e2mpho(3), catflg(10), g1,c1,leda,x2m OPEN (20,FILE=fnu3,ACCESS='direct',RECL=84) ! 1 record per star i = 0 DO i = i + 1 READ (20,REC=i,ERR=99) ! number of bytes . ra,spd, im1,im2,sigmag, objt,dsf ! 8 + 6 + 2 = 16 . ,sigra,sigdc, na1,nu1,us1,cn1 ! 4 + 4 = 8 . ,cepra,cepdc, pmrac,pmdc, sigpmr,sigpmd ! 4 + 8 + 4 = 16 . ,id2m, jmag,hmag,kmag, icqflg, e2mpho ! 4 + 6 + 6 = 16 . ,smB,smR2,smI, clbl,qfB,qfR2,qfI ! 6 + 4 = 10 . ,catflg, g1,c1, leda, x2m, rn ! 10 + 4 + 4 = 18 ENDDO 99 WRITE (*,'(a,i9)') 'last record number on file = ',i-1 num item fmt unit explanation remark ------------------------------------------------------------------------ 1 ra I*4 mas right ascension at epoch J2000.0 (ICRS) (1) 2 spd I*4 mas south pole distance epoch J2000.0 (ICRS) (1) 3 im1 I*2 millimag UCAC fit model magnitude (2) 4 im2 I*2 millimag UCAC aperture magnitude (2) 5 sigmag I*2 millimag UCAC error on magnitude (larger of sc.mod)(3) 6 objt I*1 object type (4) 7 dsf I*1 double star flag (5) 16 8 sigra I*2 mas s.e. at central epoch in RA (*cos Dec) 9 sigdc I*2 mas s.e. at central epoch in Dec 10 na1 I*1 total # of CCD images of this star 11 nu1 I*1 # of CCD images used for this star (6) 12 us1 I*1 # catalogs (epochs) used for proper motions 13 cn1 I*1 total numb. catalogs (epochs) initial match 8 14 cepra I*2 0.01 yr central epoch for mean RA, minus 1900 15 cepdc I*2 0.01 yr central epoch for mean Dec,minus 1900 16 pmrac I*4 0.1 mas/yr proper motion in RA*cos(Dec) 17 pmdc I*4 0.1 mas/yr proper motion in Dec 18 sigpmr I*2 0.1 mas/yr s.e. of pmRA * cos Dec 19 sigpmd I*2 0.1 mas/yr s.e. of pmDec 16 20 id2m I*4 2MASS pts_key star identifier 21 jmag I*2 millimag 2MASS J magnitude 22 hmag I*2 millimag 2MASS H magnitude 23 kmag I*2 millimag 2MASS K_s magnitude 24 icqflg I*1 * 3 2MASS cc_flg*10 + phot.qual.flag (7) 25 e2mpho I*1 * 3 2MASS error photom. (1/100 mag) (8) 16 26 smB I*2 millimag SuperCosmos Bmag 27 smR2 I*2 millimag SC R2mag (9) 28 smI I*2 millimag SC Imag 29 clbl I*1 SC star/galaxy classif./quality flag (10) 30 qfB I*1 SC quality flag Bmag (11) 31 qfR2 I*1 SC quality flag R2mag (11) 32 qfI I*1 SC quality flag Imag (11) 10 33 catflg I*1 * 10 mmf flag for 10 major catalogs matched (12) 34 g1 I*1 Yale SPM object type (g-flag) (13) 35 c1 I*1 Yale SPM input cat. (c-flag) (14) 36 leda I*1 LEDA galaxy match flag (15) 37 x2m I*1 2MASS extend.source flag (16) 38 rn I*4 MPOS star number; identifies HPM stars (17) 18 ------------------------------------------------------------------------ 84 = total number of bytes per star record
Note (1): Positions are on the International Celestial Reference System (ICRS) as represented by the Hipparcos / Tycho-2 catalogs. The epoch for the positions of all stars is J2000.0; the weighted mean catalog position was updated using the provided proper motions. The observational UCAC position is but one of several going into these values and is not given in the UCAC3, thus the original UCAC observation cannot be recovered from these data. The declination is given in south pole distance (spd) and can be converted back to a true declination by subtracting 324000000 mas.
Note (2): Unknown, or unrealistic photometric results are set to magnitude = 18 (18000 mmag entry in catalog). Systematic errors are expected to be below 0.1 mag for im1, im2 photometric results obtained from the UCAC CCD pixel data. The aperture photometry is considered more robust, particularly for "odd" cases, while the model fit magnitude is expected to be more accurate for "well behaved" stars.
Note (3): A value of -1 for error in magnitude means "unknown". For many stars a photometric error based on the scatter from individual observations of that star on different CCD frames could be obtained. A model error was also attempted to be assigned, based on the S/N ratio. The error quoted here is the larger of the 2. If that error exceeds 0.9 mag the error was set to 0.9 mag (900 mmag entry in catalog data).
Note (4): The object type flag is used to identify possible problems with a star and has the following meaning:
-2 = warning: object could be from possible streak -1 = warning: object is near overexposed star 0 = good star 1 = good star (data copied from another entry) 2 = warning: contains at least 1 overexposed image 3 = warning: all images are overexposed or "bad"
Note (5): The dsf flag is a double star flag used to indicate the type/quality of double star fit with the following meaning:
0 = single star 1 = primary of pair with unreal secondary = single 2 = forced separation, on same frame 3 = blended image, some CCD frames show single star, some double 4 = forced separation, 2 objects on same frame number 5 = primary component of real double 6 = secondary component of real double 7 = other "odd" case
Note (6): A zero for the number of used images indicates that all images have some "problem" (such as overexposure). In that case an unweighted mean over all available images (na) is taken to derive the mean position, while normally a weighted mean was calculated based on the "good" images, excluding possible problem images (nu <= na).
Note (7): For each 2MASS bandpass a combined flag was created (cc_flg*10 + ph_qual) consisting of the contamination flag (0 to 5) and the photometric quality flag (0 to 8).
0 = cc_flg 2MASS 0, no artifacts or contamination 1 = cc_flg 2MASS p, source may be contaminated by a latent image 2 = cc_flg 2MASS c, photometric confusion 3 = cc_flg 2MASS d, diffraction spike confusion 4 = cc_flg 2MASS s, electronic stripe 5 = cc_flg 2MASS b, bandmerge confusion 0 = no ph_qual flag 1 = ph_qual 2MASS X, no valid brightness estimate 2 = ph_qual 2MASS U, upper limit on magnitude 3 = ph_qual 2MASS F, no reliable estimate of the photometric error 4 = ph_qual 2MASS E, goodness-of-fit quality of profile-fit poor 5 = ph_qual 2MASS A, valid measurement, [jhk]snr>10 AND [jhk]cmsig<0.10857 6 = ph_qual 2MASS B, valid measurement, [jhk]snr> 7 AND [jhk]cmsig<0.15510 7 = ph_qual 2MASS C, valid measurement, [jhk]snr> 5 AND [jhk]cmsig<0.21714 8 = ph_qual 2MASS D, valid measurement, no [jhk]snr OR [jhk]cmsig req.
For example icqflg = 05 is decoded to be cc_flg=0, and ph_qual=5, meaning no artifacts or contamination from cc_flg and 2MASS qual flag = "A" .
Note (8): The photometric errors from 2MASS were rounded by 1 digit here to fit into fewer bytes (1/100 mag instead of millimag).
Note (9): The R magnitude from the second epoch Schmidt plates (R2) is used for UCAC3, as provided in the SuperCosmos source catalog.
Note (10): clbl is a combination of the SuperCOSMOS "meanclass" and modified "blend" flag (meanclass + 10*blend) originally for each magnitude (B, R1, R2, I). The flag provided here is the maximum value over all bands for each of the 2 flags. The SuperCOSMOS mean class flag is an estimate of image class based on unit-weighted mean of individual classes from (B, R1, R2, I). The SuperCOSMOS modified blend flag indicates if blending is detected.
The "meanclass" has the following meaning from SuperCOSMOS:
1 = galaxy 2 = star 3 = unclassifiable 4 = noiseThe modified "blend" flag has the following meaning:
0 = no blending 1 = possible blending detected
Note (11): This is a modified quality flag from the "qualB", "qualR2", and "qualI" quality flag from SuperCOSMOS, which gives an indication of the quality of the image from the three bands (B, R2, I). The modified quality flag qfB, qfR2, and qfI have the following meaning:
-1 = qual blank in SuperCOSMOS, no flag given 0 = qual zero in SuperCOSMOS, no problems detected 1 = qual < 128 in SuperCOSMOS, reliable image 2 = qual < 65535 in SuperCOSMOS, problems detected 3 = qual >= 65535 in SuperCOSMOS, spurious detection
Note (12): The catflg provides reference to 10 major catalogs used in the computation of the proper motions and catalog matching. Each of the 10 numbers range from 0 to 6 and are the "mmf" (multiple match flag) with respect to each of the 10 following catalogs:
Hip, Tycho, AC2000, AGK2B, AGK2H, ZA, BY, Lick, SC, SPM catflg 1 2 3 4 5 6 7 8 9 10The value for each byte, the mmf flag, has the following meaning:
0 = star not matched with this catalog 1 = unique match, not involving a double star 2 = closest match, not involving a double, likely o.k. 3 = unique match, and involving a double star 4 = closest match, and involving a double, likely o.k. 5 = maybe o.k. smallest sep. match in both directions 6 = same as 5, but involving a double star
Note (13): The g-flag from the Yale San Juan first epoch Southern Proper Motion data (YSJ1, SPM) has the following meaning:
0 = no info 1 = matched with 2MASS extended source list 2 = LEDA galaxy 3 = known QSO
Note (14): The c-flag from the Yale San Juan first epoch Southern Proper Motion data (YSJ1, SPM) indicates which input catalog has been used to identify stars for pipeline processing:
1 = Hipparcos 2 = Tycho2 3 = UCAC2 4 = 2MASS psc 5 = 2MASS xsc (extended sources, largely (but not all!) galaxies) 6 = LEDA (confirmed galaxies, Paturel et al. 2005) 7 = QSO (Veron-Cetty & Veron 2006)
Note (15): This flag is either 0 (no match) or contains the log of the apparent total diameter for I-band (object size) information copied from the LEDA catalog (galaxies). A size value of less than 1 has been rounded up to 1.
Note (16): This flag is either 0 (no match) or contains the length of the semi-major axis of the fiducial ellipse at the K-band (object size) information copied from the 2MASS extended source catalog. If the size is larger than 127, the flag was set to 127.
Note (17): MPOS running star numbers over 140 million indicate high proper motion stars which were identified in UCAC pixel data from matches with known HPM stars. The position given for those HPM stars is the unweighted mean of the CCD observations and the proper motion is copied from the literature catalog.
The following table gives the total range of values present these data.
# explanation unit minimum maximum ---------------------------------------------------------------------- 1 right ascension epoch J2000.0 (ICRS) [mas] 2 1295999990 2 south pole distance epoch J2000.0 (ICRS) [mas] 57990 647908484 3 UCAC fit model magnitude [mmag] 2329 18000 4 UCAC aperture magnitude [mmag] 2797 18000 5 error on magnitude (larger of sc.model) [mmag] -1 900 6 object type -2 3 7 double star flag 0 7 8 s.e. at central epoch in RA (*cos Dec) [mas] 5 500 9 s.e. at central epoch in Dec [mas] 5 500 10 total numb. of CCD images per star 1 70 11 number of CCD images used per star 0 68 12 numb. catalogs (epochs) used for proper motion 1 31 13 total numb. of catalogs (epochs) initial match 0 113 14 central epoch - 1900 for mean RA [1/100 yr] -477 10438 15 central epoch - 1900 for mean Dec [1/100 yr] -938 10438 16 proper motion in RA*cos(Dec) [0.1 mas/yr] -37060 67670 17 proper motion in Dec [0.1 mas/yr] -58130 102770 18 s.e. of pmRA * cos Dec [0.1 mas/yr] -10 500 19 s.e. of pmDE [0.1 mas/yr] -10 500 20 2MASS pts_key star identifier 0 1340037129 21 2MASS J magnitude [mmag] -2652 30000 22 2MASS H magnitude [mmag] -3732 30000 23 2MASS K_s magnitude [mmag] -4227 30000 24 2MASS cc_flg*10 + phot.qual.flag J band 0 58 25 2MASS cc_flg*10 + phot.qual.flag H band 0 58 26 2MASS cc_flg*10 + phot.qual.flag K band 0 58 27 2MASS error photom. J band [1/100 mag] 0 127 28 2MASS error photom. H band [1/100 mag] 0 127 29 2MASS error photom. K band [1/100 mag] 0 127 30 SC Bmag [mmag] 0 30000 31 SC R2mag [mmag] 0 30000 32 SC Imag [mmag] 0 30000 33 SC star/galaxy classif./quality flag 0 14 34 SC quality flag Bmag -1 2 35 SC quality flag R2mag 0 2 36 SC quality flag Imag -1 2 37 mmf flag Hipparcos catalog 0 1 38 mmf flag Tycho-2 catalog 0 1 39 mmf flag AC2000 catalog 0 1 40 mmf flag AGK Bonn catalog 0 6 41 mmf flag AGK Hamburg catalog 0 6 42 mmf flag ZA catalog 0 6 43 mmf flag BY catalog 0 6 44 mmf flag Lick catalog 0 6 45 mmf flag SuperCosmos catalog 0 6 46 mmf flag SPM catalog 0 6 47 Yale SPM object type (g-flag) 0 3 48 Yale SPM input cat. (c-flag) 0 7 49 LEDA galaxy match flag (size info) 0 118 50 2MASS extend.source flag (size info) 0 127 51 MPOS star number 3 140051297
table_zones = table listing info for each zone
This is a text file (ASCII) giving summary information about stars in each zone. There are 360 lines, 1 each for a 0.5 deg wide zone in declination, beginning at the South Celestial Pole. The meaning of the columns are:
1 zn = zone number (1 to 360) 2 n1 = running star ID number of 1st star in this zone 3 ns = total number of stars in this zone 4 dec = upper limit of declination of this zone sample data: zn n1 ns dec 1 1 1258 -89.5 2 1259 3828 -89.0 3 5087 6485 -88.5 ... 358 100759267 4104 89.0 359 100763371 2132 89.5 360 100765503 918 90.0
u3index.asc = index file for each 0.1 hour in RA, ASCII
This is a text file (ASCII). Each line contains data for an area of sky (bin) 0.5 deg wide in declination (indexed by zone number from 1 to 360), and 0.1 h wide in RA (indexed from 1 to 240). So there are a total of 360 * 240 = 86400 lines on this file. The meaning of the columns are:
1 n0 = running star number (index along the main data file) of the star before the first one in this bin, the sequence stars out with 0 at the beginning of each new declination zone 2 nn = number of stars in this bin (which can be zero) 3 zn = zone number (1 to 360) 4 j = index for bins along RA (1 to 240) (divide by 10 = RA hour) 5 dec = declination corresponding to zn, printed out only at the beginning of a new zone sample data: 0 3 1 1 -89.5 3 3 1 2 6 6 1 3 12 4 1 4 ... 304461 305 180 239 304766 310 180 240 0 318 181 1 0.5 318 315 181 2 ... 913 1 360 238 914 1 360 239 915 3 360 240
u3index.unf = index file for each 0.1 hour in RA, unformatted binary
This file contains the same data as the u3index.asc, however as binary with the following access explanation (Fortran):
INTEGER*4 n0(360,240), nn(360,240) OPEN (15,FILE=fnidxu,ACCESS='direct',RECL=345600) ! 360 * 240 * 4 READ (15,REC=1) n0 READ (15,REC=2) nn
u3read.sample: This is the output of a run of the u3read code on zone z042 showing the first 20 records of that binary file. Exactly the same data as the corresponding binary file data are shown with columns in the same order as outlined above. However, the 3 items of "e2mpho" (error in 2MASS photometry) are separate columns, while the SPM g1 and c1 items are merged into a single column. Thus the ASCII table output of the sample data has 39 columns.
u3read.f = sample Fortran code to read UCAC3 zone files
This code reads a file from the main UCAC3 data (binary zone data) and outputs all the information into an ASCII table, star by star, 1 star per line. The user can select a range in RA, Dec and magnitude.
In a project such as this that has spanned a decade and two continents, many people have been involved. Here we list people and their main contributions to the project.
This project would not have been possible without support from the USNO administration. Special thanks are given to Thomas Corbin for under- standing the need for such a project, articulating it to those with resources, and administering the project in its early days. Thanks are given to the three USNO Astrometry Department Heads during the UCAC project. Without their continued support, it would not have come to fruition. They are F. Stephen Gauss, Ted Rafferty, and Ralph Gaume. Thanks are given to the USNO Scientific Director, Kenneth Johnston, for his approval and support of the project and for making USNO resources available.
Our successful stay at the Cerro Tololo Interamerican Observatory would not have been possible without a memorandum of understanding, worked out by P. Kenneth Seidelmann, USNO, and the then director of CTIO, Malcolm Smith. The entire staff of CTIO is thanked for their generous support. The same holds for all the people at the Naval Observatory Flagstaff Station (NOFS) during the northern hemisphere observing of UCAC, in particular we want to thank the then director Jeff Pier.
Also, we wish to thank Gary Sims from Spectral Instruments for building our 4k camera and providing outstanding support over the years. Finally, we wish to acknowledge the following for their important contributions; Bill Gray for custom updates to his GUIDE software regarding minor planet ephemerids, and Rae Stiening (Univ.of Mass.) for providing preliminary and pre-release 2MASS data to our project.
This list includes items relevant to UCAC even if they are not cited in the above text.