The NASA-Sloan Atlas data is available in flat-file form, which we document and link to here. See the search page for on-line searching and browsing of the galaxies. See the documentation for a more detailed description of our methods and the caveats for a list of known problems. Below please find information about how to access the FITS images, the data model for the master file, some source catalog information, and release notes.

The current catalog can be obtained as single FITS format file (0.5 Gb):

nsa_v0_1_2.fits     (see data model below)

Through this web site, registered users can make comments on particular entries, for example marking badly deblended cases or unusual galaxies. We provide you with an up-to-date Yanny parameter file version of these comments at the link below:

nsa_comments.par     (current version, subject to change)

FITS images

Given a catalog entry, it is possible to download the images used for their measurement. For each object, FITS format images can be retrieved at URLs following the pattern:

   http://sdss.physics.nyu.edu/mblanton/v0/detect/v0_1/[SUBDIR]/[IAUNAME]-[band].fits.gz  (full mosaic)
   http://sdss.physics.nyu.edu/mblanton/v0/detect/v0_1/[SUBDIR]/atlases/[PID]/[IAUNAME]-parent-[PID].fits.gz (parent image)
   http://sdss.physics.nyu.edu/mblanton/v0/detect/v0_1/[SUBDIR]/atlases/[PID]/[IAUNAME]-[PID]-atlas-[AID].fits.gz (child image)

The full mosaic for each band is a square mosaic centered around the catalog object center (RACAT, DECCAT in the master catalog); in this case "band" is one of "u", "g", "r", "i", "z", "fd", and "nd".

The parent image is a cutout of that mosaic containing the galaxy and any of its close neighbors. It has 14 HDU: the even HDU are the images in SDSS u, SDSS g, SDSS r, SDSS i, SDSS z, GALEX near UV, and GALEX far UV; the odd HDU are the inverse variances of the same. The units are nanomaggies.

The child image is the deblended child of the parent, used for the measurements in the catalog. It has 7 HDU, one for each image in each band; the inverse variances used in the measurements are the same as for the parent.

Master catalog datamodel

Column name Data type Units Description
IAUNAME string IAU-style designation based on RA/Dec
SUBDIR string Subdirectory for images in the 'detect' directory
RA float64 deg Right Ascension of measured object center (J2000)
DEC float64 deg Declination of measured object center (J2000)
ISDSS int32 Zero-indexed row of SDSS source file (-1 if no match)
INED int32 Zero-indexed row of NED source file (-1 if no match)
ISIXDF int32 Zero-indexed row of 6dFGRS source file (-1 if no match)
IALFALFA int32 Zero-indexed row of ALFALFA source file (-1 if no match)
IZCAT int32 Zero-indexed row of ZCAT source file (-1 if no match)
ITWODF int32 Zero-indexed row of 2dFGRS source file (-1 if no match)
MAG float32 mag Nominal B magnitude; not reliable, only used to set size of image for analysis
Z float32 Heliocentric redshift
ZSRC string Source of redshift determination (alfalfa, ned, sdss, sixdf, twodf, or zcat)
SIZE float32 deg Size of analyzed mosaics
RUN int16 SDSS drift scan run covering catalog position (RACAT, DECCAT)
CAMCOL int8 SDSS camcol covering catalog position (RACAT, DECCAT)
FIELD int16 SDSS field covering catalog position (RACAT, DECCAT)
RERUN string Photometric rerun of SDSS used to determine SDSS coverage
XPOS float32 pix SDSS camera column of catalog position (RACAT, DECCAT)
YPOS float32 pix SDSS camera row of catalog position (RACAT, DECCAT)
ZLG float32 Local Group redshift (following Yahil et al. 1977)
ZDIST float32 Distance estimate using pecular velocity model of Willick et al. (1997); multiply by c/H0 for Mpc
ZDIST_ERR float32 Error estimate in distance
NSAID int32 unique ID within NSA catalog
NMGY[7] float32 nanomaggies Galactic-extinction corrected AB flux used for K-correction (from SERSICFLUX) in FNugriz
NMGY_IVAR[7] float32 nanomaggies-2 Inverse variances used for K-correction in FNugriz (includes error floors)
OK int16 1 if K-correction was performed, 0 if not (should all be 1)
RNMGY[7] float32 nanomaggies Reconstructed AB nanomaggies from K-correction fit
ABSMAG[7] float32 mag Absolute magnitude estimates for FNugriz from K-corrections (Ωm=0.3, ΩΛ=0.7, h=1)
AMIVAR[7] float32 mag-2 Inverse variance on absolute magnitudes in FNugriz
EXTINCTION[7] float32 mag Galactic extinction in FNugriz from Schlegel, Finkbeiner & Davis (1997)
KCORRECT[7] float32 mag K-corrections used for absolute magnitudes in FNugriz
KCOEFF[5] float32 Coefficients of templates in K-correction fit (see Blanton & Roweis 2007)
MTOL[7] float32 solar Mass-to-light ratio derived in K-correction for FNugriz
B300 float32 Star-formation rate b-parameter (current over past average) for last 300 Myrs (from K-correction fit, use with caution)
B1000 float32 Star-formation rate b-parameter (current over past average) for last 1 Gyrs (from K-correction fit, use with caution)
METS float32 Metallicity from K-correction fit (use with caution)
MASS float32 h-2 solar masses Stellar mass from K-correction fit (use with caution)
XCEN float64 pix X centroid in child atlas image
YCEN float64 pix Y centroid in child atlas image
NPROF[7] float32 Number of measured azimuthally averaged profile bins in FNugriz
PROFMEAN[7,15] float32 nanomaggies per pixel Mean surface brightness in annuli in FNugriz (note that F and N have pixel size 1.5 arcsec, ugriz have pixel size 0.396 arcsec)
PROFMEAN_IVAR[7,15] float32 nanomaggies-2 Inverse variance of PROFMEAN in FNugriz
QSTOKES[7,15] float32 Q Stokes parameter in each annulus in FNugriz
USTOKES[7,15] float32 U Stokes parameter in each annulus in FNugriz
BASTOKES[7,15] float32 Axis ratio b/a derived from Stokes paramaters in each annulus in FNugriz
PHISTOKES[7,15] float32 deg Angle (E of N) derived from Stokes paramaters in each annulus in FNugriz
PETROFLUX[7] float32 nanomaggies Azimuthally-averaged SDSS-style Petrosian flux in FNugriz (GALEX-SDSS photometric systems)
PETROFLUX_IVAR[7] float32 nanomaggies-2 Inverse variance of PETROFLUX
FIBERFLUX[7] float32 nanomaggies Flux in 3-arcsec diameter aperture (not apodized) in FNugriz
FIBERFLUX_IVAR[7] float32 nanomaggies-2 Inverse variance of FIBERFLUX
BA50 float32 Axis ratio b/a from Stokes parameters at 50% light radius
PHI50 float32 deg Angle (E of N) from Stokes parameters at 50% light radius
BA90 float32 Axis ratio b/a from Stokes parameters at 90% light radius
PHI90 float32 deg Angle (E of N) from Stokes parameters at 90% light radius
SERSICFLUX[7] float32 nanomaggies 2D Sersic fit flux in FNugriz (GALEX-SDSS photometric systems)
SERSICFLUX_IVAR[7] float32 nanomaggies-2 Inverse variance of SERSICFLUX
SERSIC_N float32 2D Sersic index from fit
SERSIC_BA float32 Axis ratio b/a from 2D Sersic fit
SERSIC_PHI float32 deg Angle (E of N) of major axis in 2D Sersic fit
ASYMMETRY[7] float32 Asymetry parameter in FNugriz
CLUMPY[7] float32 Clumpy parameter in FNugriz
DFLAGS[7] float32 Flags from measurement in each band (FNugriz)
AID float32 Child id within parent
PID float32 Parent id within mosaic for this object
DVERSION float32 Version of dimage used for measurement
PROFTHETA[15] float32 arcsec Outer radius of each measured annulus
PETROTHETA float32 arcsec Petrosian radius (derived from r band)
PETROTH50 float32 arcsec Petrosian 50% light radius (derived from r band)
PETROTH90 float32 arcsec Petrosian 90% light radius (derived from r band)
SERSIC_TH50 float32 arcsec 50% light radius of 2D Sersic fit (along major axis)
OBJNO int32 Index number for Renbin Yan fits to spectra (PLATE*1000+FIBERID)*100L+(MJD%100)
PLATE int32 SDSS plate number (0 if not observed)
FIBERID int32 SDSS fiber number (0 if not observed)
MJD int32 SDSS MJD of spectroscopic observation (0 if not observed)
COEFF[7] float32 Coefficients for spectroscopic continuum fit
VDISP float32 km/s Velocity dispersion
D4000 float32 Dn4000 parameter (Balogh et al 1999)
D4000ERR float32 Error in Dn4000 parameter
FA float32 A fraction in K+A fit
FAERR float32 error in A fraction in K+A fit
S2FLUX float32 10-17 erg/s/cm2 [SII] 6716, 6731 flux
S2FLUXERR float32 10-17 erg/s/cm2 Error in [SII] 6716, 6731 flux
S2EW float32 [SII] 6716, 6731 equivalent width
S2EWERR float32 Error in [SII] 6716, 6731 equivalent width
S2VMEAS float32 km/s Gaussian σ for this line, corrected for instrumental broadening
S2VMERR float32 km/s Error in Gaussian σ for this line, corrected for instrumental broadening
S2RATIO float32 flux ratio in [SII] doublet ([SII] 6731 / [SII] 6716)
HAFLUX float32 10-17 erg/s/cm2 Hα flux
HAFLUXERR float32 10-17 erg/s/cm2 Error in Hα flux
HAEW float32 Hα equivalent width
HAEWERR float32 Error in Hα equivalent width
HAVMEAS float32 km/s Gaussian σ for this line, corrected for instrumental broadening
HAVMERR float32 km/s Error in Gaussian σ for this line, corrected for instrumental broadening
N2FLUX float32 10-17 erg/s/cm2 [NII] 6584 flux
N2FLUXERR float32 10-17 erg/s/cm2 Error in [NII] 6584 flux
N2EW float32 [NII] 6584 equivalent width
N2EWERR float32 Error in [NII] 6584 equivalent width
N2VMEAS float32 km/s Gaussian σ for this line, corrected for instrumental broadening
N2VMERR float32 km/s Error in Gaussian σ for this line, corrected for instrumental broadening
HBFLUX float32 10-17 erg/s/cm2 Hβ flux
HBFLUXERR float32 10-17 erg/s/cm2 Error in Hβ flux
HBEW float32 Hβ equivalent width
HBEWERR float32 Error in Hβ equivalent width
HBVMEAS float32 km/s Gaussian σ for this line, corrected for instrumental broadening
HBVMERR float32 km/s Error in Gaussian σ for this line, corrected for instrumental broadening
O1FLUX float32 10-17 erg/s/cm2 [OI] 6300 flux
O1FLUXERR float32 10-17 erg/s/cm2 Error in [OI] 6300 flux
O1EW float32 [OI] 6300 equivalent width
O1EWERR float32 Error in [OI] 6300 equivalent width
O1VMEAS float32 km/s Gaussian σ for this line, corrected for instrumental broadening
O1VMERR float32 km/s Error in Gaussian σ for this line, corrected for instrumental broadening
O2FLUX float32 10-17 erg/s/cm2 [OII] 3727 flux
O2FLUXERR float32 10-17 erg/s/cm2 Error in [OII] 3727 flux
O2EW float32 [OII] 3727 equivalent width
O2EWERR float32 Error in [OII] 3727 equivalent width
O2VMEAS float32 km/s Gaussian σ for this line, corrected for instrumental broadening
O2VMERR float32 km/s Error in Gaussian σ for this line, corrected for instrumental broadening
O3FLUX float32 10-17 erg/s/cm2 [OIII] 5007 flux
O3FLUXERR float32 10-17 erg/s/cm2 Error in [OIII] 5007 flux
O3EW float32 [OIII] 5007 equivalent width
O3EWERR float32 Error in [OIII] 5007 equivalent width
O3VMEAS float32 km/s Gaussian σ for this line, corrected for instrumental broadening
O3VMERR float32 km/s Error in Gaussian σ for this line, corrected for instrumental broadening
AHGEW float32 Hγ absorption equivalent width (no emission infill correction)
AHGEWERR float32 Error in Hγ absorption equivalent width
AHDEW float32 Hδ absorption equivalent width (no emission infill correction)
AHDEWERR float32 Error in Hδ absorption equivalent width
NE3EW float32 [NeIII] equivalent width
NE3EWERR float32 Error in [NeIII] equivalent width
NE5EW float32 [NeV] equivalent width
NE5EWERR float32 Error in [NeV] equivalent width
AV float32 AV assuming intrinsic Balmer decrement of 2.85, RV = 3.1 and O'Donnell (1994) extinction
S2NSAMP float32 median signal-to-noise ratio per pixel between 3600 and 6900 A (restframe)
RACAT float64 deg Right Ascension of catalog object (J2000)
DECCAT float64 deg Declination of catalog object (J2000)
ZSDSSLINE float32 Redshift from emission lines
SURVEY string Survey within SDSS of plate
PROGRAMNAME string Program name of plate
PLATEQUALITY string Quality of plate
TILE int32 Tile number of spectrum
PLUG_RA float64 deg Right Ascension of spectroscopic fiber (J2000)
PLUG_DEC float64 deg Declination of spectroscopic fiber (J2000)

Source catalog information

Some ancillary information regarding the catalogs from which this sample is selected can be found here:

Release notes

The NSA version numbers are of the form "vN_M_P". In this scheme, "N" refers to the version of the source catalogs used. All versions starting with vN will have consistent NSAID numbers. "M" refers to the version of the photometric analysis; for example, when a new set of imaging is included, M is incremented. "P" refers to changes in derived data (K-corrections, line measurements, and the like).