Yale/San Juan SPM4 Catalog
--------------------------
(Release 2009-11-05)
1) Overview
The SPM4 Catalog contains absolute proper motions, celestial coordinates,
and B,V photometry for 103,319,647 stars and galaxies between the south
celestial pole and -20 degrees declination. The catalog is roughly
complete to V=17.5. It is based on photographic and CCD observations
taken with the Yale Southern Observatory's double-astrograph at Cesco
Observatory in El Leoncito, Argentina.
Those in a hurry to extract data from the SPM4 catalog files can skip to
section 4) for a description of the organization and format of the files
and of two Fortran programs included for making extractions. Those wanting
a more thorough explanation of the procedures used to construct the catalog
are invited to forge ahead and read on.
2) Observations
The first-epoch survey, taken from 1965 to 1979, was entirely photographic.
The second-epoch survey is approximately 1/3 photographic (taken from 1988
to 1998) and 2/3 CCD-based (taken from 2004 through 2008). The survey
consists of fields at 5-degree centers in declination and varying separation
along right ascension, but always less than or equal to 5 degrees. Since
each photographic plate covers a 6.3 x 6.3 degree area of sky, there is
significant overlap in the photographic portion of the survey. Also, each
field has a pair of blue and yellow passband plates taken (typically)
simultaneouly with the double-astrograph. For a small fraction of the
fields, plates were repeated within the same "epoch". Each photographic
observation consisted of two offset exposures, one 2 hours in duration, the
other 2 minutes. Also, an objective wire grating was always used in order
to produce measurable grating images for the brighter stars. In this
manner, the effective dynamic range of the plates was greatly increased,
allowing bright Hipparocos-magnitude stars to be linked to external galaxies
on the same plate. A more thorough description of the plate material and
the various image systems is given by Girard et al. (1998).
All SPM plates were scanned with the Precision Measuring Machine (PMM) at the
US Naval Observatory's Flagstaff Station (NOFS). The raw pixel data were
saved and later analyzed at the US Naval Observatory in Washington (USNO),
to obtain image centers and photometric indices for all detectable images.
Beginning in 2001, CCD cameras were installed on the double astrograph in
order to complete the SPM second-epoch survey. (Photographic plates with
the 103 emulsion were no longer being produced.) Two cameras were installed,
a 4K x 4K PixelVision (PV) camera (15 micron pixels) in the focal plane of
the yellow lens, and an Apogee 1K x 1K (24 micron pixels) camera behind the
blue lens. The latter was later replaced by an Apogee Alta 2K x 2K (12
micron pixels) CCD camera. Exposure times were 120-s, reaching the same
depth as the first-epoch plates. As with the plates, the objective grating
was in place for the CCD observations. A two-fold overlap of frames with
the PV's 0.93 x 0.93 degree FOV was initiated for all SPM fields lacking
second-epoch plate material. Eventually, when it was found that a single
CCD exposure was superior to the multiple first-epoch plate material in
terms of astrometric precision, the two-fold coverage was changed to single
coverage with the PV frames. The yellow lens' PV data were used for both
astrometry and photometry. The blue lens' Apogee data were used only in
the photometric reductions.
3) Construction of the Catalog
The astrometric reductions, for both the photographic and CCD data, made
use of an input "master" catalog that was necessary to properly identify
the various multiple images (diffraction grating orders and, in the case of
the plates, multiple exposures). This master catalog was constructed by
combining the following external catalogs in the specified order;
1 = Hipparcos
2 = Tycho2
3 = UCAC2
4 = 2MASS psc
5 = 2MASS xsc (extended sources, largely (but not entirely!) galaxies)
6 = LEDA (confirmed galaxies, Paturel et al. 2005, A&A 430, 751)
7 = QSO (Veron-Cetty & Veron 2006, A&A 455, 773)
Objects appearing in multiple catalogs were found by positional coincidence
and reconciled by adopting the position of the higher ranked one (Hipparocs
being considered best). This master input catalog was then used to identify
all measurable images within the list of detections in the SPM plate and
CCD data. Thus, an object that does not appear in any of these input
catalogs, cannot appear in the SPM4 catalog. The completeness of the SPM4
is the product of the completeness of these input catalogs and the magnitude
limits and resolving limits (i.e., ability to center crowded/blended images)
of the SPM material.
There are 670 SPM field centers at declination -20 degrees and southward.
The SPM4 is comprised of 660 of these fields. There are nine -20-deg fields
for which first-epoch plates were never taken and one -20-deg field for which
the first-epoch plates were mistakenly not measured. Thus, the northern
boundary of the SPM4 sky coverage contains a small number of "notches"
at which the northernmost stars are at approximately -21.9 degrees instead
of -20 degrees.
An input master catalog, as described above, was constructed from cutouts
of the external source catalogs for each of the 660 SPM fields included
in the SPM4. Within a single field, each object was assigned a "master"
ID number that was simply the running number corresponding to the order of
that object in the field's cumulative list. Thus, Hipparcos stars would be
assigned the lowest numbers, increasing through Tycho2 stars, UCAC2 stars,
etc. Combining the three digit field number with the seven digit master
catalog number within a field yields a star's overall SPM4 ID number.
Since many stars in the substantial overlap of neighboring fields would
possess multiple IDs, the ID from the lowest numbered field was adopted as
the unique SPM4 identifier.
3.1) astrometric reductions
All SPM plates were scanned with the PMM at NOFS. The raw pixel data from
the scans were stored and sent to USNO for analysis. The existing StarScan
pipeline (Zacharias et al. 2008) was heavily modified by USNO staff to
accomodate the SPM pixel data. The overall process included a conversion of
the PMM transmission values into density values, smoothing the data for the
purposes of image detection and background fitting, and then fitting the
unsmoothed 2-d density profiles with an azimuthally symmetric exponential
function. (Tests using an elliptical exponential function showed no
improvement over the azimuthally symmetric one, even for the slightly
elongated 1st and 2nd-order diffraction images.) The derived image positions
on each of the 884 PMM CCD footprints required to cover an SPM plate were then
transformed into a single global coordinate system using information from the
overlap regions of adjacent footprints and the laser interferometric metrology
of the footprint centers. As the resulting astrometry from all first-epoch
SPM plates was included in the construction of the UCAC3 catalog, further
discussion of the PMM data analysis can be found in Zacharias et al. (2010).
The USNO-derived centers and image parameters for all detections on the SPM
plates, both first and second-epoch plates, were then provided to the Yale SPM
team for subsequent reduction.
The SPM CCD frames are corrected for bias, dark (in the case of the Apogee
frames, dark current is neglible in the PV), and flatfielding. SExtractor
is used to identify detections, give aperture photometry, and provide
preliminary x,y centers. Final x,y centers are derived by fitting
two-dimensional elliptical Gaussian functions to the image intensities.
See Casetti-Dinescu et al. (2007) for further details of the astrometric
reduction procedures used with the PixelVision camera data.
In general, similar techniques to those used in constructing previous
versions of SPM catalogs were used to build the SPM4. (See Girard et al.
1998, Platais et al. 1998, Girard et al. 2004.) Stars for which both
the central-order exposure and first-order grating-image pair were
measurable were used to derive and correct each plate's magnitude equation
individually. Following the procedures developed for the SPM1 and SPM2
catalogs, all extended sources were given magnitude corrections corresponding
to their measured magnitude shifted by -0.7.
In the case of the CCD image centers, there were systematic offsets
detected between the position of the central image and the mean of the
positions of the grating-order pairs. However, these did not follow the
behavior expected for magnitude equation (or charge transfer efficiency
effects). Therefore, this offset was corrected as such, a simple offset
between the image order systems, instead of as a magnitude equation.
(See Casetti-Dinescu et al. 2007.)
Measures from all exposures and all grating-image systems were transformed
to a single system for each plate and for each CCD frame. The CCD x,y
positions were then corrected for a fixed-pattern geometric distortion
believed to be linked to the filter. This correction "mask" was built up
from residuals of hundreds of frames at different pointings reduced into
UCAC2 coordinates. The corrected CCD x,y positions were then transformed
onto the system of the UCAC2 to facilitate pasting together the roughly 50
to 100 frames (depending on whether it had two-fold or single coverage) that
comprise a 6 deg x 6 deg SPM field. An overlap method is employed to
perform this task, using Tycho2 stars as an external reference system to
ensure that systematics from the individual overlap solutions do not
accumulate. In this manner, an artificial "pseudo-plate" is built up from
CCD frames. This pseudo-plate can then be treated the same as a real
second-epoch plate.
In previous versions of SPM catalogs, first- and second-epoch plate pairs
were combined to yield relative proper motions per plate pair. These
were then corrected to absolute proper motions using external galaxies in
the case of SPM1 and SPM2, or Hipparcos star proper motions in the case of
SPM3. For the SPM4, instead of combining plate pairs, we have decided to
construct the best possible position catalogs at first and at second epoch,
over the entire coverage area. This is accomplished by dividing the
plates into three groups; first-epoch plates, second-epoch plates, and
second-epoch pseudo-plates, then combining plate data within each group using
a plate-overlap strategy as follows.
Within each of these plate groups, all plates are pushed through the software
pipeline that performs the preliminary reductions described above. This
pipeline combines multiple images of the same star (short/long exposure and
diffraction orders), corrects the positions for magnitude equation, and then
models these x,y positions into RA,Dec from a subset of the Tycho2 catalog
adjusted to the epoch of the plate. (The subset is roughly half the Tycho2
stars, those of better quality.) The plate model consists of classical
5th-order distortion terms plus a general 3rd-order polynomial. Uncertainties
as a function of magnitude are derived from the scatter of stars with multiple
images measured on that plate.
With each plate having been reduced into RA,Dec on the system of Tycho2,
we then make use of the overlapping areas to make further adjustments of
each plate. This is done in an iterative approach as opposed to a
simultaneous global solution. The procedure we're using is to
1/ create an "internal+external" reference catalog by doing a weighted
average of mutiply-measured stars' RA,Dec and supplementing this with
Hipparcos and Tycho2 positions/proper-motions,
2/ model each plate into this ref catalog with a general 3rd-order model
plus classical 5th-order distortion, correcting the plate's RA,Decs at
the end of the iteration,
3/ examine the differences in positions, obtained before and after this
iteration. If it's still subtstantial, go back to step 1/.
The presence of the Hipparcos/Tycho2 stars in the reference catalog prevents
errors from the overlap solutions from accumulating and causing a reference
system drift. The number of iterations required for convergence was from
5 to 9 for the three plate groups.
When all is done, i.e., after sufficient convergence of the iterative
solutions, the weighted-average positions for every object on every plate
are derived and adopted as the celestial coordinates of that object, at the
weighted mean epoch for that particular star.
This procedure was applied to the first-epoch plates, the second-epoch plates,
and the second-epoch pseudo-plates that had been pasted together from the
PV CCD frame data. For this last group, a second "pasting" of the CCDs
was performed using preliminary proper motions derived from a first
iteration to update all CCD data within a single pseudo-plate to the same
epoch. Also, for the pseudo-plate regions it was realized that there were
some "holes" in the sky coverage from several causes. In areas with
single-fold sky coverage, inaccurate telescope pointing led to occasional
gaps between adjacent PV frames. Additionally, some frames that had passed
a quality check at the telescope were later found to have problems that
rendered them unusable. Finally, there were a handful of SPM fields for
which the second-epoch plates were also unusable and pseudo-plates created
from an incomplete number of CCD frames in these fields were constructed in
their place. In order to avoid having holes or cracks in the SPM4 sky
coverage for want of second-epoch positions in these cases, it was decided to
supplement the pseudo-plate fields with second-epoch positions taken from
the master input catalog. The additional stars and galaxies added were those
with input catalog V estimates less than 17.5 in most areas, but a cutoff of
V=16.5 was used in two galactic plane fields. Of course, in order to appear
in the final SPM4 catalog, a corresponding detection and measure of the
object in the first-epoch plate material must exist. Objects with proper
motions derived in this manner can be identified in the catalog, their values
of np and nc, the number of second-epoch plate and CCD measures per object,
will both be zero.
When completed, first-epoch positions and second-epoch positions on the
system of the ICRS were in hand for all detected objects in the 660 fields.
Uncertainties in the positions were derived from the (weighted) scatter of
multiply measured stars as a function of magnitude and this empirical relation
calculated for each object according to its magnitude estimate.
The positions and uncertainties were then combined to yield proper motions
and proper-motion uncertainties in a straightforward manner. While in
theory these proper motions should be on the system of the ICRS via Hipparcos
and Tycho2, and thus absolute, in practice an additional correction is
needed. Examining the measured proper motions of galaxies within each
field as well as the differences with Hipparcos proper motions at the bright
end, it was apparent that a residual magnitude equation remained in the
derived proper motions. It was decided to calculate a final correction to
absolute proper motion per field that was linear with magnitude, using the
mean magnitude of galaxies and of Hipparcos stars on the field. Such a
linear correction was derived for all 660 fields. The actual proper-motion
correction applied to each star in the catalog was the weighted mean of the
corrections for the three closest field centers to the star, weighted by the
inverse distance from the field center squared.
We note that the quoted uncertainties, particularly those of the proper
motions, are unexpectedly (and possibly unrealistically) low. This may
be due to the use of weightings that are themselves uncertain enough that
a single measurement dominates the calculated mean, more so than it should.
The uncertainties will be studied further and presented in an upcoming
paper (Girard et al. 2010). In the meantime, the proper-motion
uncertainties should be used with caution.
3.2) photometric reductions
The B,V photometry in the SPM4 is extremely heterogeneous. In some cases,
it is derived from our blue and visual filtered CCD cameras. In some cases,
it is derived from the PMM measures of our first-epoch plates. And in the
cases where neither of these are available or reliable, it is propogated
from the input master catalog. In this latter group one can find relatively
good photometry from Tycho2 or less reliable extrapolations to B and V
magnitudes from 2MASS J,H,K. As such, it is difficult to estimate
uncertainties for much of the B,V photometry listed. Our magnitude errors
are as likely to be caused by spurious radius measures or inapproriate
extrapolations as they are by signal to noise considerations. Thus, we
do not provide individual uncertainty estimates for the B,V photometry
listed. We do, however, indicate the source of the B and V values given,
be they CCD-based, plate-based, or input catalog values.
For the purpose of identifying which image orders should be searched for
within the list of detections on a plate or CCD, a magnitude estimate of
each star in the input master catalog is needed. For Hipparcos and Tycho2
stars, the B_Tycho and V_Tycho values (transformed to the Johnson system)
were adopted. For almost all other stars, B and V photometry was not
available so an approximate extrapolation was derived based on 2MASS J,H,K.
Hipparcos and Tycho2 stars, which have both B,V and 2MASS photometry, were
used to calibrate each SPM field with a relation of the form
B-J = b0 + b1*(J-H) + b2*(H-K) + b3*J*(J-H) + b4*J*(H-K)
with a similar function for V-J. These were used to provide an approximate
estimate of B and V for stars without Tycho2 photometry. For the small
fraction of objects without Tycho2 or 2MASS photometry, the objects were
assumed to be faint and arbitrarily assigned the magnitude limit of the
plate or CCD on which it was expected to fall. Again, these input master
catalog B,V magnitude estimates were primarily to aid in identifying the
various image orders detected. Only in the case that there was neither SPM
plate-based photometry nor SPM CCD-based photmetry did these estimates find
their way to the final catalog.
The PV and Apogee CCD frames of the second-epoch SPM survey were reduced in
a standard fashion using aperture photometry with calibration into Tycho2
V and B photometry (corrected to the Johnson system). When available, these
CCD-based magnitudes are provided in the SPM4 catalog, superseding the other
magnitude estimates.
Photographic photometry based on the parameters of the image model fits of
the PMM scan data proved to be problematic. Among the various image model
fit parameters derived, the fit radius provided the best (although still
poor) correlation with external calibrating photometry. For extended sources,
the radius was, of course, inappropriate. For such objects the input master
catalog's magnitude estimate was retained instead, (unless there existed
CCD-based photometry). Also, there was a large, non-gaussian scatter between
the radius measures and calibrating photometry, indicating that at times the
radius estimate was simply erroneous. Thus, during the SPM4 plate photometric
reduction procedure, a comparison was made between the preliminarily derived
(radius-based) magnitude and that from the input master catalog. If these
differed by more than one magnitude, it was interpreted as evidence that one
or the either was in error. Since we could not know which, a somewhat
expedient choice was made: the fainter of the two magnitude values was
retained, under the assumption that the steepness of the luminosity function
implies that it is more likely that the star is faint. Unfortunately, the
only relevant flag that was retained per star was whether or not it had
passed through the plate photometry portion of the pipeline, not whether the
resulting magnitude estimate was truly plate-based or a retention of the input
master catalog value. The photographic photometry was disappointingly poor
in any event. Thus, the only truly reliable B,V photometry in the SPM4
catalog is that flagged as being CCD-based, i.e., with ib=3 and/or iv=3.
4) Organization and format of the SPM4 Catalog files
This distribution of the SPM4 catalog consists of the following files:
readme_spm4.txt = this file describing the SPM4 catalog
boxcut_spm4.f = Fortran code for rectangular cutouts from SPM4
match_spm4.f = Fortran code for matching the SPM4 by RA,Dec
rsNN.asc (NN=20 to 89) = main catalog files, in 1-deg Declination strips
rsNN.ind (NN=20 to 89) = index of record numbers at every 1-deg of RA
2massxid/rsNN.2mx = auxiliary 2MASS cross-identification files
In the DVD distribution, the rsNN.asc and rsNN.2mx files are actually bzip2
compressed and have a bz2 suffix on the filenames. These files can be
uncompressed using bunzip2 (or the equivalent) to obtain the ascii files
that are described here. Once uncompressed, the main catalog and index
files occupy 14 GB of disk space. Files in the 2massxid subdirectory
occupy an additional 3.8 GB.
4.1) the main catalog
The main catalog data are contained within files binned by declination into
1-degree wide strips. Within each of these declination strips, the stars
and galaxies are sorted by right ascension. There are 70 such declination
strip files, named rsNN.asc, where NN ranges from 20 to 89. The "asc"
suffix indicates these are plain ascii files, 144 bytes per record (including
line feed). Each record contains the data for one object. There is no
header line. The format of each record is as described in Table 1 and its
accompanying explanatory notes.
Table 1. Format of the rsNN.asc files
col bytes format name unit description
------------------------------------------------------------------------------
1 001-012 f12.7 RA deg right ascension (ICRS, epoch=2000.0)
2 013-024 f12.7 Dec deg declination (ICRS, epoch=2000.0)
3 025-030 f6.1 era mas error in right ascension
4 031-036 f6.1 edec mas error in declination
5 037-045 f9.2 pma mas/yr abs. proper motion in RA (mu_alpha*cos(Dec))
6 046-054 f9.2 pmd mas/yr abs. proper motion in Dec
7 055-061 f7.2 epma mas/yr error in pma
8 062-068 f7.2 epmd mas/yr error in pmd
9 069-074 f6.2 B mag B magnitude
10 075-080 f6.2 V mag V magnitude
11 081-082 i2 ib source flag for B mag
12 083-083 i1 iv source flag for V mag
13 084-089 f6.2 epav yrs weighted mean epoch of obs. minus 1950
14 090-095 f6.2 ep1 yrs weighted mean 1st-epoch minus 1950
15 096-101 f6.2 ep2 yrs weighted mean 2nd-epoch minus 1950
16 102-104 i3 mp number of 1st-epoch plates used
17 105-106 i2 np number of 2nd-epoch plates used
18 107-108 i2 nc number of 2nd-epoch CCD frames used
19 109-119 i11.10 spmid unique spm4 id: field no. + input cat. line
20 120-121 i2 igal galaxy/extended-source flag
21 122-122 i1 icat input catalog source flag
22 123-129 f7.3 J 2MASS J magnitude
23 130-136 f7.3 H 2MASS H magnitude
24 137-143 f7.3 K 2MASS K magnitude
------------------------------------------------------------------------------
Notes to Table 1.
1,2: Positions are given in degrees, at epoch 2000.0 and on the J2000 (ICRS)
system.
3,4: Estimated uncertainties in the position, in mas, at the mean epoch
of observation (column 13).
5,6: Absolute proper motion, in mas/yr, along RA (mu_alpha*cos(Dec)) and
along Dec.
7,8: Estimated uncertainties in proper motion, in mas/yr, at the mean
epoch of observation (column 13).
9: Johnson B magnitude estimate. ib (col. 11) indicates the source.
10: Johnson V magnitude estimate. iv (col. 12) indicates the source.
11: If 1, the B magnitude came from the compiled input catalog.
If 2, the B magnitude was based on 1st-epoch SPM plates.
If 3, the B magnitude was based on 2nd-epoch SPM CCD observations.
12: If 1, the V magnitude came from the compiled input catalog.
If 2, the V magnitude was based on 1st-epoch SPM plates.
If 3, the V magnitude was based on 2nd-epoch SPM CCD observations.
13: Weighted mean epoch of observations, minus 1950.
14: Weighted mean epoch of 1st-epoch material, minus 1950.
15: Weighted mean epoch of 2nd-epoch material, minus 1950. Note that
CCD frames were assembled into pseudo-plates during processing.
Small differences in epoch between the frames were compensated for
using preliminary proper motions to put all CCD pseudo-plates at an
arbitrary epoch of 2007.0.
16: Number of 1st-epoch plates used, mp.
17: Number of 2nd-epoch plates used, np.
18: Number of 2nd-epoch CCD frames used, nc. If nc > 9, it is set to 9.
Note that if np=0 and nc=0, the 2nd-epoch position used to calculate
the proper motion was adopted from the input source catalog.
19: SPM4 identifier. The first three digits indicate the SPM field
number. The final seven digits are the running line number from that
field's input master list, an ordered concatenation of the external
catalogs merged to create the SPM4 input list.
20: If 0, there is no indication the object is non-stellar.
If 1, the object is a 2MASS extended source.
If 2, the object is a LEDA confirmed galaxy.
if 3, the object is from the Veron-Cetty & Veron QSO catalog.
21: If 1, the object is from Hipparcos.
If 2, the object is from Tycho-2.
if 3, the object is from UCAC2.
If 4, the object is from the 2MASS point source catalog (psc).
If 5, the object is from the 2MASS extended source catalog (xsc).
If 6, the object is from the LEDA galaxy catalog.
If 7, the object is from the Veron-Cetty & Veron QSO catalog.
Note that for objects in multiple catalogs, the first (lowest number)
catalog identification is retained.
22-24: J, H, K from 2MASS (psc) for matched objects, otherwise = 0.000.
------------------------------------------------------------------------------
The minimum and maximum values of each data column are given in Table 2. It
is evident that there are spurious proper motion values within the catalog.
There was no post-construction attempt made to filter these out, so caution
is advised. Values of both 0.00 and 99.00 were used to flag objects for
which B or V photometry is absent.
Table 2. Extreme values of the data fields in the rsNN.asc files
col name minimum maximum
-----------------------------------------
1 RA 0.0000302 359.9999933
2 Dec -89.9887208 -20.0000007
3 era 0.0 754.8
4 edec 0.1 680.4
5 pma -9990.75 10000.34
6 pmd -9980.70 10002.64
7 epma 0.37 161.71
8 epmd 0.24 327.67
9 B 0.00 99.00
10 V 0.00 99.00
11 ib 1 3
12 iv 1 3
13 epav 15.72 57.00
14 ep1 15.50 31.69
15 ep2 37.58 57.00
16 mp 1 20
17 np 0 14
18 nc 0 9
19 spmid 0010000001 6705238549
20 igal 0 3
21 icat 1 7
22 J -2.652 99.999
23 H -3.732 99.999
24 K -4.227 99.999
-----------------------------------------
The following table compiles some other statistics pertaining to the make-up
of the catalog.
Table 3. Catalog contents statistics
Total # of objects......................... = 103,319,647
# with 2nd-epoch CCD measures.............. = 65,355,419
# with 2nd-epoch plate measures............ = 27,042,797
# with 2nd-epoch taken from input catalog.. = 10,921,431
# with no 2MASS cross-id................... = 153,192
# with ig=3, i.e., QSOs.................... = 1,341
# with ig=2, i.e., confirmed LEDA galaxies. = 85,519
# with ig=1, i.e., 2MASS extended sources.. = 214,279
4.2) index files
To facilitate efficient access to the rsNN.asc files, each has a corresponding
rsNN.ind file that indexes the record number of the rsNN.asc as a function
of right ascension, in 1-degree bins. Specifically, there are 360 lines in
each rsNN.ind file, listing the record number in the rsNN.asc file of the last
entry with RA less than 1 degree, 2 degrees, etc, up to 360 degrees in RA.
For instance, the first and last five lines of rs20.ind are
1 722 0.9993611
2 1475 1.9996621
3 2228 2.9996152
4 2911 3.9980199
5 3578 4.9961548
.
.
.
356 1797264 355.9998468
357 1798055 356.9985624
358 1798916 357.9986077
359 1799709 358.9987489
360 1800554 359.9998957
The fixed-format columns of the rsNN.ind files are
column 1: limiting integer RA,
column 2: record no. in the rsNN.asc file with RA less than this limit,
column 3: precise RA of the referenced object in the rsNN.asc file.
(Note that the final (360th) line in each rsNN.ind file provides the total
number of records in the corresponding rsNN.asc file.)
4.3) 2MASS cross-identifications
Within the 2massxid subdirectory are files giving cross-identifications
between the SPM4 id, the record number within the rsNN.asc files, and the
2MASS identification. These files are named similarly to the rsNN.asc
files but with a *.2mx suffix. They contain the same number of records as
their rsNN.asc counterparts. The first and last five lines of rs20.2mx are
given below as an example.
20 0000001 5990037144 00000015-2004276
20 0000002 5990029697 00000017-2053536
20 0000003 5990033543 00000028-2029235
20 0000004 5990032553 00000049-2030280
20 0000005 5990029698 00000075-2050038
.
.
.
20 1800550 5990005442 23595886-2009435
20 1800551 5990031572 23595937-2043208
20 1800552 5990034458 23595958-2029578
20 1800553 5990034460 23595986-2025016
20 1800554 5990035378 23595997-2021111
The fixed-format columns are
column 1: the declination strip number, i.e., the "NN" in rsNN.asc
column 2: the record number in the corresponding rsNN.asc file
column 3: the SPM4 id
column 4: the 2MASS id, "00000000+0000000" indicates no cross-id
These rsNN.2mx files should prove useful in matching SPM4 data with star
lists that a user might have that already contain 2MASS ids. Re-sorting the
rsNN.2mx files by 2MASS id may be necessary to use them efficiently, but
this will vary depending on a user's particular cross-matching task.
4.4) Fortran programs for accessing the catalog
Two Fortran programs are included in the distribution that users can
compile and run in order to make extractions from the SPM4 catalog. The
first of these, boxcut_spm4.f, makes a rectangular cutout (gnomonic
projection) about a specified field center and with specified widths, in
degrees. Output is all SPM4 lines that fall within the rectangular portion
of sky.
The second program, match_spm4.f, allows a user to match an input list of
RA and Dec with the SPM4 catalog, extracting all matches within a specified
tolerance (in arcseconds). The program can read RA,Dec positions in either
degrees or in sexagesimal format. The user specifies the format in the
input file interactively, specifying a character string label at the same
time. The output is a file with a format similar to that of the *.asc
files, with the matched input label and separation added to each line.
Both programs work only with the uncompressed versions of the *.asc files
of the SPM4. In their current form, the programs also assume these and the
*.ind files are located in the directory from which the programs are run.
This can easily be modified by changing the length and value of the string
"aroot" in the Fortran source code.
5) Acknowledgements
The Southern Proper Motion program is a decades-long endeavor involving the
participation of numerous institutions and countless people. The following
is a meager attempt at listing those "countless" many who have contributed
to the success of the SPM program, culminating with the release of the SPM4
catalog.
Bill van Altena (Yale)
Terry Girard (Yale)
Norbert Zacharias (USNO)
Carlos Lopez (Univ. de San Juan, Argentina)
Dana Casetti-Dinescu (Yale)
Kathy Vieira (Yale/CIDA)
Dave Monet (NOFS)
Danillo Castillo (ALMA)
David Herrera (NOAO)
Imants Platais (Johns Hopkins)
Vera Kozhurina-Platais (STScI)
Tim Beers (Michigan State Univ.)
Young Sun Lee (Michigan State Univ.)
Reed Meyer (TripAdvisor LLC, Boston)
Arnold Klemola (Lick Obs.)
Rene Mendez (Univ. de Chile)
Xinjian Guo (Yale)
Paulo Holvorcem (Univ. Estadual de Campinas, Brazil)
John T. Lee (Interactive Data, Boxborough, Mass.)
Zhenghong Tang (Shanghai Astronomical Obs.)
Valdimir Korchagin (Rostov Univ., Russia)
Ting-Gao Yang (Chinese Academy of Sciences, Time Service Center)
Wen-Zhang Ma (Beijing Normal Univ.)
Gary Wycoff (USNO)
Charlie Finch (USNO)
Jin-Fuw Lee (IBM, deceased)
We are grateful to the National Science Foundation for their substantial
support in the form of a series of grants spanning more than two decades,
the University of San Juan for extensive logistical and personnel support
throughout the course of the survey, the Argentine CONICET for funding of
some of the instrumentation, and Yale University for critical financial
support during the completion of the SPM program. Also, the program would
not have begun were it not for an initial grant from the Ford Foundation,
which we also gratefully acknowledge. Finally, we are indebted to our
observers who provided the raw material upon which this catalog is based.
6) References
Casetti-Dinescu, D. I., Girard, T. M., Herrera, D., van Altena, W. F.,
Lopez, C. E., & Castillo, D. J. 2007, AJ 134, 195.
Girard, T. M., Platais, I., Kozhurina-Platais, V., van Altena, W. F.,
& Lopez, C. E. 1998, AJ 115, 855.
Girard, T. M., Dinescu, D. I., van Altena, W. F., Platais, I., Monet, D. G.,
& Lopez, C. E. 2004, AJ 127, 3060.
Girard et al. 2010, (in preparation)
Zacharias, N., Winter, L., Holdenried, E. R., de Cuyper, J.-P., Rafferty,
T. J., & Wycoff, G. L. 2008, PASP 120, 644.
Zacharias N, et al. 2010, "The Third US Naval Observatory CCD Astrograph
Catalog (UCAC3)", submitted AJ.
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Questions or bug reports concerning the contents of this readme file, the
Fortran code, or any aspects of this distribution of the SPM4 Catalog may
be addressed to
Terry Girard
Yale Astronomy Dept.
P.O. Box 208101
New Haven, CT 06520-8101 USA
terry.girard(*AT*)yale.edu