The 640 combined flux- and wavelength-calibrated spectra over all exposures (potentially spanning multiple nights) for a given mapped plate.
In summary, this file contains the following:
Each HDU contains an entry for each of the 640 fibers on a plate.
There are two masks, an "AND" mask and an "OR" mask. The spectra are constructed from 3 or more 15-minute observations, and the "AND" mask bits are set if that bit is set for each and every input observation. The "OR" mask bits are set if that bit is set for any of the observations.
The mask bits are set as follows:
0 NOPLUG Fiber not listed in plugmap file
1 BADTRACE Bad trace from routine TRACE320CRUDE
2 BADFLAT Low counts in fiberflat
3 BADARC Bad arc solution
4 MANYBADCOLUMNS >10% pixels are bad columns
5 MANYREJECTED >10% pixels are rejected in extraction
6 LARGESHIFT Large spatial shift between flat and object pos'n
7 BADSKYFIBER Sky Fiber shows extreme residuals
8 NEARWHOPPER Within 2 fibers of a whopping fiber (inclusive)
10 SMEARIMAGE Smear available for red and blue cameras (deprecated)
11 SMEARHIGHSN S/N sufficient for full smear fit (deprecated)
12 SMEARMEDSN S/N only sufficient for scaled median fit (deprecated)
16 NEARBADPIXEL Bad pixel within 3 pixels of trace
17 LOWFLAT Flat field less than 0.5
18 FULLREJECT Pixel fully rejected in extraction (INVVAR=0)
19 PARTIALREJECT Some pixels rejected in extraction
20 SCATTEREDLIGHT Scattered light significant
21 CROSSTALK Cross-talk significant
22 NOSKY Sky level unknown at this wavelength (INVVAR=0)
23 BRIGHTSKY Sky level > flux + 10*(flux error)
AND sky > 2.0 * median(sky,99 pixels)
24 NODATA No data available in combine B-spline (INVVAR=0)
25 COMBINEREJ Rejected in combine B-spline
26 BADFLUXFACTOR Low flux-calibration or flux-correction factor
27 BADSKYCHI Relative chi^2 > 3 in sky residuals at this wavelength
28 REDMONSTER Contiguous region of bad chi^2 in sky residuals
(with threshhold of relative chi^2 > 3)
Which mask bits are important? The conditions that are considered very bad are already used to set the errors to infinity for the effected pixels (specifically, the inverse variance is set to zero). The most useful mask bit to look at is BRIGHTSKY, which indicates when the sky is so bright relative to the object that perhaps one shouldn't trust any of the object flux there. Our reported errors are meant to include sky-subtraction errors, but there are instances (particularly around 5577) where these errors may be untrustworthy.
The dispersion per pixel and the sky flux are computed at each pixel by re-weighting the individual spectra at each pixel according to their formal errors. This re-weighting is only approximate.
Note that the sky lines are slightly shifted in the reductions because we transform the velocities to the barycenter of the solar system. Each exposure that contributes to the co-added spectra will have slightly different barycenter correction, so the "average sky" contains a superposition of these slightly-offset sky lines. These shifts keep the object spectra as-measured at the barycenter, regardless of the time of year or the Earth's rotation relative to the spectroscopic targets.
Contains the flux density of each spectrum in units of 10^-17 erg/s/cm^2/Ang. The length of the spectra (NAXIS1) can vary, depending on the pixel binning and wavelength coverage. The number of spectra (NAXIS2) is always 640.
SIMPLE = T / FIT STANDARD BITPIX = -32 / FITS BITS/PIXEL NAXIS = 2 / NUMBER OF AXES NAXIS1 = 3856 / WIDTH (TOTAL!) NAXIS2 = 640 / HEIGHT (TOTAL!) EXTEND = T / TAI = 4593557832.61 / 1st row - Number of seconds since Nov 17 1858 RA = 187.46463 / 1st row - Right ascension of telescope boresigh DEC = 12.487701 / 1st row - Declination of telescope boresight (d EQUINOX = 2000.00 / RADECSYS= 'FK5 ' / AZ = 300.020823333 / 1st row - Azimuth (encoder) of tele (0=N?) (de ALT = 56.0378723333 / 1st row - Altitude (encoder) of tele (de AIRMASS = 1.15830 / FOCUS = 60.000000 / 1st row - Focus piston (microns?) DATE-OBS= '2004-06-10' / 1st row - TAI date TAIHMS = '04:01:06.29' / 1st row - TAI time (HH:MM:SS.SS) (TAI-UT = appr TIMESYS = 'tai ' / TAI, not UTC TAI-BEG = 4593555888.00 / Exposure Start Time TAI-END = 4593558651.00 / Exposure End Time MJD = 53166 / MJD of observation MJDLIST = '53166 ' / VERSION = 'v3_138_0' / version of IOP CAMVER = 'SPEC1 v4_8' / Camera code version OBSERVER= 'jcb ' OBSCOMM = 'science ' TELESCOP= 'SDSS 2.5-M' / Sloan Digital Sky Survey NEXP = 12 / Number of exposures in this file BESTEXP = 27097 / EXPID01 = 'b1-00027096-00027094-00027095' / ID string for exposure 1 EXPID02 = 'b1-00027097-00027094-00027095' / ID string for exposure 2 EXPID03 = 'b1-00027098-00027094-00027095' / ID string for exposure 3 EXPID04 = 'b2-00027096-00027094-00027095' / ID string for exposure 4 EXPID05 = 'b2-00027097-00027094-00027095' / ID string for exposure 5 EXPID06 = 'b2-00027098-00027094-00027095' / ID string for exposure 6 EXPID07 = 'r1-00027096-00027094-00027095' / ID string for exposure 7 EXPID08 = 'r1-00027097-00027094-00027095' / ID string for exposure 8 EXPID09 = 'r1-00027098-00027094-00027095' / ID string for exposure 9 EXPID10 = 'r2-00027096-00027094-00027095' / ID string for exposure 10 EXPID11 = 'r2-00027097-00027094-00027095' / ID string for exposure 11 EXPID12 = 'r2-00027098-00027094-00027095' / ID string for exposure 12 NEXP_B1 = 3 / b1 camera number of exposures NEXP_B2 = 3 / b2 camera number of exposures NEXP_R1 = 3 / r1 camera number of exposures NEXP_R2 = 3 / r2 camera number of exposures EXPT_B1 = 2400.30 / b1 camera exposure time (seconds) EXPT_B2 = 2400.30 / b2 camera exposure time (seconds) EXPT_R1 = 2400.30 / r1 camera exposure time (seconds) EXPT_R2 = 2400.30 / r2 camera exposure time (seconds) EXPTIME = 2400.30 / Minimum of exposure times for all cameras SPCOADD = 'Sun Apr 29 13:56:29 2007' / SPCOADD finished FLAVOR = 'science ' / Flavor of this sequence (e.g., dome f QUALITY = 'excellent' / night/image quality RADEG = 1.87464100000000E+02 / Right Ascension. (degrees) DECDEG = 1.24877500000000E+01 / Declination. (degrees) PLATEID = 1615 / Plate Id TILEID = 1140 / Tile Id CARTID = 5 /Cartridge used in this plugging REDDEN = '0.0796 0.0586 0.0425 0.0322 0.0228' / Median reddening vector for pla MAPID = 5316001 / Map Id NAME = '1615-53160-01' / Name of target; PlateId-MJD-Mapper Re NGUIDE = 27.0000 / Number of guider frames during exposure SEEING20= 1.22667 / 20% seeing during exposure (arcsec) SEEING50= 1.32667 / 50% seeing during exposure (arcsec) SEEING80= 1.47667 / 80% seeing during exposure (arcsec) RMSOFF20= 0.132410666667 / 20% RMS offset of guide fibers (arcsec) RMSOFF50= 0.250306333333 / 50% RMS offset of guide fibers (arcsec) RMSOFF80= 0.378881333333 / 80% RMS offset of guide fibers (arcsec) COLBIN = 1 / Binning factor perpendicular to the c ROWBIN = 1 / Binning factor perpendicular to the r PROGRAM = 'binning 1 1 ' / Identifying name for CCD program SECFOCUS= 6.00000000000000E+01 / Secondary Mirror Position as reported GUIDEIMG= '/data/spectro/guider/gimg0208.fits' / Last archived guider image WTIME = 1086840891.67 / weatherData(timeStamp) AIRTEMP = 14.6333333333 / weatherData(airtemp) DEWPOINT= -6.43333333333 / weatherData(dewpoint) DEWDEP = 21.0666666667 / weatherData(dewpointDep) DUSTA = -9999.00000000 / weatherData(dusta) DUSTB = 1326.66666667 / weatherData(dustb) DUSTC = 14545.3333333 / weatherData(dustc) DUSTD = 1068.33333333 / weatherData(dustd) GUSTD = 2.78100000000000E+02 / weatherData(gustd) GUSTS = 22.0333333333 / weatherData(gusts) HUMIDITY= 22.7000000000 / weatherData(humidity) HUMIDOUT= 22.0000000000 / weatherData(humidout) PRESSURE= 21.4900000000 / weatherData(pressure) WINDD = 268.933333333 / weatherData(windd) WINDS = 14.6000000000 / weatherData(winds) TEMP01 = -93.3600000000 / CCD 01 Temperature TEMP02 = -93.4900000000 / CCD 02 Temperature TEMP03 = -92.3200000000 / CCD 03 Temperature TEMP04 = -92.5800000000 / CCD 04 Temperature AUTHOR = 'Scott Burles & David Schlegel' / VERSIDL = '6.3 ' / Version of IDL VERSUTIL= 'v5_2_0 ' / Version of idlutils VERSREAD= 'v5_3_3 ' / Version of idlspec2d for pre-processing raw dat VERS2D = 'v5_3_3 ' / Version of idlspec2d for 2D reduction VERSCOMB= 'v5_3_2 ' / Version of idlspec2d for combining multiple spe VERSLOG = 'fermi-CVS 04/29/07' / Version of SPECLOG product VERSFLAT= 'v1_7 ' / Version of SPECFLAT product OPBC = 'opBC-51813.par' / OPCONFIG= 'opConfig-50000.par' / OPECALIB= 'opECalib-51577.par' / XSIGMA = 0.954296739300 / XSIGMIN = 0.931442000000 / XSIGMAX = 1.01137995720 / WSIGMA = 0.897743760824 / WSIGMIN = 0.850736000000 / WSIGMAX = 1.00960004330 / PLUGFILE= 'plPlugMapM-1615-53160-01.par' / LAMPLIST= 'lamphgcdne.dat' / SKYLIST = 'skylines.dat' / HELIO_RV= 27.9144043066 / Heliocentric correction (added to velocities) VACUUM = T / Wavelengths are in vacuum SFLATTEN= T / Superflat has been applied PSFSKY = 3 / Order of PSF skysubtraction SKYCHI2 = 1.13077654335 / Mean chi^2 of sky-subtraction SCHI2MIN= 1.03063195647 / SCHI2MAX= 1.23022636571 / PREJECT = 0.200000 / Profile area rejection threshold SPEC1_G = 18.2088 /(S/N)^2 for spec 1 at mag 20.20 SPEC1_R = 20.4968 /(S/N)^2 for spec 1 at mag 20.25 SPEC1_I = 17.8236 /(S/N)^2 for spec 1 at mag 19.90 SPEC2_G = 18.0836 /(S/N)^2 for spec 2 at mag 20.20 SPEC2_R = 16.9525 /(S/N)^2 for spec 2 at mag 20.25 SPEC2_I = 15.7482 /(S/N)^2 for spec 2 at mag 19.90 NSTD = 16 / Number of (good) std stars GOFFSTD = -0.0647583 / Spectrophoto offset for std stars in G-band GRMSSTD = 0.0488723 / Spectrophoto RMS for std stars in G-band ROFFSTD = -0.0422068 / Spectrophoto offset for std stars in R-band RRMSSTD = 0.0385001 / Spectrophoto RMS for std stars in R-band IOFFSTD = -0.0537424 / Spectrophoto offset for std stars in I-band IRMSSTD = 0.0358539 / Spectrophoto RMS for std stars in I-band GROFFSTD= -0.0159950 / Spectrophoto offset for std stars in (GR) GRRMSSTD= 0.0492487 / Spectrophoto RMS for std stars in (GR) RIOFFSTD= -0.00345993 / Spectrophoto offset for std stars in (RI) RIRMSSTD= 0.0257763 / Spectrophoto RMS for std stars in (RI) NGAL = 449 / Number of (good) main galaxies GOFFGAL = 0.00695229 / Spectrophoto offset for main galaxies in G-band GRMSGAL = 0.0514427 / Spectrophoto RMS for main galaxies in G-band ROFFGAL = 0.00336075 / Spectrophoto offset for main galaxies in R-band RRMSGAL = 0.0504721 / Spectrophoto RMS for main galaxies in R-band IOFFGAL = 0.00660992 / Spectrophoto offset for main galaxies in I-band IRMSGAL = 0.0561837 / Spectrophoto RMS for main galaxies in I-band GROFFGAL= 0.000831604 / Spectrophoto offset for main galaxies in (GR) GRRMSGAL= 0.0390498 / Spectrophoto RMS for main galaxies in (GR) RIOFFGAL= -0.00204182 / Spectrophoto offset for main galaxies in (RI) RIRMSGAL= 0.0255867 / Spectrophoto RMS for main galaxies in (RI) LOWREJ = 5 / Extraction: low rejection HIGHREJ = 8 / Extraction: high rejection SCATPOLY= 0 / Extraction: Order of scattered light polynomial PROFTYPE= 3 / Extraction profile: 1=Gaussian NFITPOLY= 1 / Extraction: Number of parameters in each profil XCHI2 = 1.19279 / Extraction: Mean chi^2 XCHI2MIN= 1.05698 / XCHI2MAX= 1.34297 / NWORDER = 2 / Linear-log10 coefficients WFITTYPE= 'LOG-LINEAR' / Linear-log10 dispersion COEFF0 = 3.57930000000 / Central wavelength (log10) of first pixel COEFF1 = 0.000100000000000 / Log10 dispersion per pixel UNAME = 'fnpc197.fnal.gov' / FBADPIX = 0.0290671 / Fraction of bad pixels FBADPIX1= 0.0292774 / Fraction of bad pixels on spectro-1 FBADPIX2= 0.0288568 / Fraction of bad pixels on spectro-2 WAT0_001= 'system=linear' / WAT1_001= 'wtype=linear label=Wavelength units=Angstroms' / CRVAL1 = 3.57930000000 / Central wavelength (log10) of first pixel CD1_1 = 0.000100000000000 / Log10 dispersion per pixel CRPIX1 = 1 / Starting pixel (1-indexed) CTYPE1 = 'LINEAR ' / DC-FLAG = 1 / Log-linear flag BUNIT = '1E-17 erg/cm^2/s/Ang' /
Contains the estimated inverse variance (i.e., the inverse of the square of the estimated error) of the flux density of each spectrum, in units of (10^-17 erg/s/cm^2/Ang)^-2. It is set to zero (i.e., infinite error) for pixels with flags indicating that the data are unreliable.
XTENSION= 'IMAGE ' / IMAGE extension BITPIX = -32 / Number of bits per data pixel NAXIS = 2 / Number of data axes NAXIS1 = 3856 / NAXIS2 = 640 / PCOUNT = 0 / No Group Parameters GCOUNT = 1 / One Data Group WAT0_001= 'system=linear' / WAT1_001= 'wtype=linear label=Wavelength units=Angstroms' / CRVAL1 = 3.57930000000 / Central wavelength (log10) of first pixel CD1_1 = 0.000100000000000 / Log10 dispersion per pixel CRPIX1 = 1 / Starting pixel (1-indexed) CTYPE1 = 'LINEAR ' / DC-FLAG = 1 / Log-linear flag BUNIT = '1/(1E-17 erg/cm^2/s/Ang)^2' /
Contains the 'AND' mask, setting bits in the combined spectra if they are set in each of the 3 or more individual exposures making up the observation.
XTENSION= 'IMAGE ' / IMAGE extension BITPIX = 32 / Number of bits per data pixel NAXIS = 2 / Number of data axes NAXIS1 = 3856 / NAXIS2 = 640 / PCOUNT = 0 / No Group Parameters GCOUNT = 1 / One Data Group WAT0_001= 'system=linear' / WAT1_001= 'wtype=linear label=Wavelength units=Angstroms' / CRVAL1 = 3.57930000000 / Central wavelength (log10) of first pixel CD1_1 = 0.000100000000000 / Log10 dispersion per pixel CRPIX1 = 1 / Starting pixel (1-indexed) CTYPE1 = 'LINEAR ' / DC-FLAG = 1 / Log-linear flag
Contains the 'OR' mask, setting bits in the combined spectra if they are set in any of the 3 or more individual exposures making up the observation.
XTENSION= 'IMAGE ' / IMAGE extension BITPIX = 32 / Number of bits per data pixel NAXIS = 2 / Number of data axes NAXIS1 = 3856 / NAXIS2 = 640 / PCOUNT = 0 / No Group Parameters GCOUNT = 1 / One Data Group WAT0_001= 'system=linear' / WAT1_001= 'wtype=linear label=Wavelength units=Angstroms' / CRVAL1 = 3.57930000000 / Central wavelength (log10) of first pixel CD1_1 = 0.000100000000000 / Log10 dispersion per pixel CRPIX1 = 1 / Starting pixel (1-indexed) CTYPE1 = 'LINEAR ' / DC-FLAG = 1 / Log-linear flag
Contains the RMS resolution at each pixel in units of pixels. To
get the FWHM resolution, multiply the pixel values by sqrt(8*ln(2))
∼ 2.35. Since the spectra are binned with constant logarithmic
dispersion, the pixel size is fixed in velocity space at 69 km/s =
ln(10) * c * 0.0001, where 0.0001 is the log10 dispersion
per pixel (stored in the header field CD1_1). To convert
to resolution in wavelength units, multiply by the local pixel size in
wavelength units, which is ln(10) * lambda * 0.0001 where lambda is
the wavelength of the pixel and 0.0001 is again the log10
dispersion.
XTENSION= 'IMAGE ' / IMAGE extension BITPIX = -32 / Number of bits per data pixel NAXIS = 2 / Number of data axes NAXIS1 = 3856 / NAXIS2 = 640 / PCOUNT = 0 / No Group Parameters GCOUNT = 1 / One Data Group WAT0_001= 'system=linear' / WAT1_001= 'wtype=linear label=Wavelength units=Angstroms' / CRVAL1 = 3.57930000000 / Central wavelength (log10) of first pixel CD1_1 = 0.000100000000000 / Log10 dispersion per pixel CRPIX1 = 1 / Starting pixel (1-indexed) CTYPE1 = 'LINEAR ' / DC-FLAG = 1 / Log-linear flag BUNIT = 'pixels ' /cm^2/s/Ang)^2' /
Contains the entries from the plPlugMapM file used for the Spectro-2D reduction. There are always 640 rows (one per object). Note that there are two arrays 'tsobjid' and 'tsobj_mag' tacked onto the end of each element of this table which contain the tsObj (from calibrated photo) id and fiber mags used in the spectrophotometry calculations for this object.
XTENSION= 'BINTABLE' /Binary table written by MWRFITS v1.4a BITPIX = 8 /Required value NAXIS = 2 /Required value NAXIS1 = 178 /Number of bytes per row NAXIS2 = 640 /Number of rows PCOUNT = 0 /Normally 0 (no varying arrays) GCOUNT = 1 /Required value TFIELDS = 21 /Number of columns in table COMMENT COMMENT *** End of mandatory fields *** COMMENT * COMMENT *** Column names *** COMMENT TTYPE1 = 'OBJID ' / TTYPE2 = 'HOLETYPE ' / TTYPE3 = 'RA ' / TTYPE4 = 'DEC ' / TTYPE5 = 'MAG ' / TTYPE6 = 'STARL ' / TTYPE7 = 'EXPL ' / TTYPE8 = 'DEVAUCL ' / TTYPE9 = 'OBJTYPE ' / TTYPE10 = 'XFOCAL ' / TTYPE11 = 'YFOCAL ' / TTYPE12 = 'SPECTROGRAPHID ' / TTYPE13 = 'FIBERID ' / TTYPE14 = 'THROUGHPUT ' / TTYPE15 = 'PRIMTARGET ' / TTYPE16 = 'SECTARGET ' / TTYPE17 = 'OFFSETID ' / TTYPE18 = 'SCI_EXPTIME ' / TTYPE19 = 'CALIBFLUX ' / TTYPE20 = 'CALIBFLUX_IVAR ' / TTYPE21 = 'SFD_EBV ' / COMMENT COMMENT *** Column formats *** COMMENT TFORM1 = '5J ' / TFORM2 = '6A ' / TFORM3 = 'D ' / TFORM4 = 'D ' / TFORM5 = '5E ' / TFORM6 = 'E ' / TFORM7 = 'E ' / TFORM8 = 'E ' / TFORM9 = '16A ' / TFORM10 = 'D ' / TFORM11 = 'D ' / TFORM12 = 'J ' / TFORM13 = 'J ' / TFORM14 = 'J ' / TFORM15 = 'J ' / TFORM16 = 'J ' / TFORM17 = 'J ' / TFORM18 = 'E ' / TFORM19 = '5E ' / TFORM20 = '5E ' / TFORM21 = 'E ' /
The sky spectrum subtracted from each fiber, in units of 10^-17 erg/sec/cm^2/A. Note that the sky lines are slightly shifted in the reductions because we transform the velocities to the barycenter of the solar system. Each exposure that contributes to the co-added spectra will have slightly different barycenter correction, so the "average sky" contains a superposition of these slightly-offset sky lines. These shifts keep the object spectra as-measured at the barycenter, regardless of the time of year or the Earth's rotation relative to the spectroscopic targets.
XTENSION= 'IMAGE ' /Image Extension created by MWRFITS v1.4a BITPIX = -32 / NAXIS = 2 / NAXIS1 = 3856 / NAXIS2 = 640 / PCOUNT = 0 / GCOUNT = 1 /
Broad-band magnitudes synthesized from the spectra. These values are here for testing purposes only, and should be considered "unofficial"; better is to use the synthesized magnitudes available in the spZbest files (output of the specBS pipeline).
XTENSION= 'IMAGE ' /Image Extension created by MWRFITS v1.4a BITPIX = -32 / NAXIS = 2 / NAXIS1 = 5 / NAXIS2 = 640 / PCOUNT = 0 / GCOUNT = 1 /
Median signal-to-noise ratio per pixel for each fiber in the g, r, and i regions. These values are here for testing purposes only, and should be considered "unofficial".
XTENSION= 'IMAGE ' /Image Extension created by MWRFITS v1.4a BITPIX = -32 / NAXIS = 2 / NAXIS1 = 3 / NAXIS2 = 640 / PCOUNT = 0 / GCOUNT = 1 /