News and updates
Bug in synthetic magnitudes of spectra: mag_0,mag_1,mag_2 --> u,g,r (not g,
There is a bug in the tabulating of synthetic magnitudes of objects
based on their integrated, flux calibrated spectra convolved with
the SDSS filter curves. In the CAS table specObjAll (and its subset
table specObj), the three quantities: mag_0, mag_1, and mag_2
are intended to be the synthetic g, r, and i band magnitudes
of each object. In fact, in DR6 they are the
u, g, and r band synthetic magnitudes. The wavelength
coverage of the u band (centered on 3551 Angstroms) does
not overlap (except at the few percent level) the wavelength coverage
of the spectrographs (which start at about 3800 Angstroms), and
the synthetic u band is only a very rough estimate. Thus, the
i synthetic magnitude is not directly available in the DR6
If you currently need access to the i band synthetic magnitude,
they are currently only available in the DR6 DAS:
You may find them in HDU# 7 of the spPlate-$plate-$mjd.fits
file in the form of a 640x5 (row x col) size image extension
table containing the u,g,r,i,z synthetic magnitudes for
all 640 objects with spectra, in fiber number order
(i.e. the first 5 numbers are for the ugriz synthetic mags
for the object at fiber#1, etc).
You may download the full spPlate-$plate-$mjd.fits file from
the DAS and extract this 'imaging region' from HDU#7 to access
The u and z synthetic magnitudes are generally not to be used since,
as mentioned above, the overlap of the wavelength coverage of the
spectrographs with these filter bandpasses is minimal.
Note that the DR5 CAS has correct g,r,i synthetic values
in mag_0,mag_1,mag_2, however, an older version of the
spectroscopic pipeline was used to process these data
and the handling of reddening is different.
Also note that the synthetic magnitude values may need an
AB correction applied to put them onto the SDSS gri system.
The spSpec-$mjd-$plate-$fiber.fit files have header keywords
MAG_G, MAG_R, MAG_I which are intended to be the same as
mag_0, mag_1, mag_2 in the specObjAll table of the CAS.
These synthetic numbers are also 'shifted by one filter'
in DR6, thus, they actually are
synthetic mags u, g and r (instead of g,r, and i) respectively.
Please note this bug.
It will be corrected for the DR7 release of the
DAS and CAS.
DR6 paper in print
The DR6 paper (Adelman-McCarthy,
J.K. et al. 2008, ApJS, 175, 297-313) has appeared in print.
Proper motions update announcement.
Proper motions are not correct.
Bug in SEGUE primTarget flag
PrimTarget flag in SEGUE plates is trunctated in the CAS
A new collaboration based on the legacy of SDSS and SDSS-II has
been formed to pursue a number of new science goals. See the SDSS-III web site at www.sdss3.org.
Patch applied to DR6
This patch, applied the week of Aug 27,2007, corrects several
bugs in the database.
The list of patches to DR6 is as follows:
- 6 segments in Stripe 36 had a bug in their
startMu/endMu, resulting in ~1500 duplicate primary
objects in the main database. This has been corrected,
and the previously duplicate primaries have been made
- The 'Propermotions' table has been incremented for BESTDR6 from
DR5 to the full DR6 dataset. Additionally, propermotions have
been added for a large number of objects which previously
had been missed because they were targeted as galaxies (but turned
out to be stars). Additionally, propermotions have
been added for Segue imaging to the SEGUEDR6 database context
in a parallel propermotions table.
Note that all these propermotions have been
're-zeropointed' from their USNO-B source by matching to
the SDSS positions for objects with zero proper motion (distant
galaxies and quasars), and thus are of overall higher accuracy than
those in the 'USNO' table.
- The 'Match' and 'MatchHead' tables in the CAS,
which connects duplicate measurements of the
same physical object on the sky, observed at
different times (for instance, objects in the overlap
between scanlines), were incompletely populated prior
to Aug 31, 2007. They have now been updated.
- The sppParams table incorrectly computed the derived
parameter velgal (the velocity of a star in
the Galactic frame of reference, subtracting out
the suns motion of (v_x,v_y,v_z) = (7,224,10) km/s
prior to Aug 31, 2007. The table is now correct.
The velgal velocities now also reflect the 7.3 km/s offset
determined by absolute reference to known globular clusters
and other Radial velocity standards. The best
radial velocity for stars in the DR6 dataset is the
'rva' value in the sppParams table. It is reliable when
the rvaerr is strictly > 0.
- A view (subset) of the sppParams table, called 'spbsparams'
has been generated for easy access to Galaxy spectral parameters,
including redshift (along with redshift confidence) and
velocity dispersion (measured two different ways). These
parameters are available on a plate-by-plate basis
in the DAS as part of the spZbest* binary FITS tables, and on a
fiber-by-fiber basis in the spSpec* FITS spectra as header
keywords, but they are gathered here in a SQL searchable table.
- Documentation has been updated on matching photometry to
spectroscopy on the SEGUE
website. Magnitudes in the sppParams table are 'PSF target' magnitudes,
the best available at the time an object was targetted for
spectroscopic followup. Since then, the imaging data for
an object may be remeasured (recorded as the best photometry).
Finally, ubercal photometry is also available for many
- The prepackaged tarballs of spectra, organized by object
category (galaxy, qso, star, etc), are now available again,
and include updates for DR6.
DR6 is available
About DR6 explains what is
new in DR6.
SEGUE spectroscopic parameters available
DR6 includes a slew of new SEGUE data, including new stellar atmospheric
parameters ([Fe/H], log g, Teff) and line indices in
the CAS BESTDR6 database. See About
DRsup - Data Release Supplemental - is available
DRsup contains additional SEGUE, M31/Perseus and stripe 82 imaging. About DRsup explains what DRsup is
and how to get it.
SDSS acknowledgements updated
The SDSS has entered a second phase of funding and operations, SDSS-II,
with new participating institutions. Please use the updated SDSS acknowledgement
statement in your publications using SDSS data.
DAS hardware is up and healthy.
Last modified: Mon Mar 31 17:06:47 CEST 2008