SDSS Data Products: "gal_line:"

This FITS binary structure contains equivalent width,and flux measurements of the nebular emission lines.


Tag Name

Data Type / Units

Description

plateid
int[1]
Plate number
fiberid
int[1]
Fiber number  (1 - 640)
sigma_balmer
float[1] km/s
Velocity dispersion (sigma not FWHM) measured simultaneously in all of the Balmer lines
sigma_balmer_err
float[1]  km/s
Error in the above
sigma_forbidden
float[1]  km/s
Velocity dispersion (sigma not FWHM) measured simultaneously in all the forbidden lines
sigma_forbidden_err
float[1]  km /s
Error in the above
v_off_balmer
float[1] km/s
Velocity offset of the Balmer lines from the measured redshift
v_off_balmer_err
float[1] km/s
Error in the above
v_off_forbidden
float[1] km/s
Velocity offset of the forbidden lines from the measured redshift
v_off_forbidden_err
float[1] km/s
Error in the above
(line_name)_cont
float[1]
1E-17 erg/s/cm^2/A
Continuum at line center from 200 pixel  median smoothing of the emission-line subtracted continuum
(line_name)_cont_err
float[1]
1E-17 erg/s/cm^2/A
Error in the continuum computed from the variance in the band pass (check this!!)
(line_name)_reqw Angstroms
The equivalent width of the continuum-subtracted emission line computed from straight integration over the bandpasses listed below (emisison is negative).   In this case the continuum comes from a running 200 pixel median and does not properly account for stellar absorption.   In general the EQW measurements provide a better measure of the true equivalent width.  The purpose of this measurement is to help characterize the stellar absorption effecting the line.  (EW_stellar = REQW - EQW)
(line_name)_reqw_err Angstroms Error in the equivalent width described above
(line_name)_eqw Angstroms
The equivalent width of the BC03 continuum-subtracted emission line computed from straight integration over the bandpasses listed below (emisison is negative) .  This properly takes into account stellar absorption.  Note that it will not be correct in the case of blended lines (ie NII & H-alpha)  -- instead use FLUX/CONT.
(line_name)_eqw_err Angstroms
Error in the equivalent width described above
(line_name)_flux float[1]
1E-17 erg/s/cm^2/A
Flux from Gaussian fit to continuum subtracted data.  (Note that the fit is done simultaneously to all the lines so de-blending happens automatically)
(line_name)_flux_err float[1]
1E-17 erg/s/cm^2/A
Error in the flux -- comes from MPFIT routine -- currently it is not clear if this is correct.  There are pretty large differences in the errors depending on if numerical or empirical derivatives are used.  
(line_name)_inst_res float[1] km/s
Instrumental resolution at the line center (measured for each spectrum from the ARC lamps)
(line_name)_chisq float[1]
Reduced chi-squared of the line fit over the bandpass used for the EW measurement



Line Name
Line Cener (A)
Lower bound
Upper bound
Type
OII_3726
3726.032
3717.0
3737.0
Em
OII_3729
3728.815
3717.0
3737.0
Em
NeIII_3869
3869.060
3859.0
3879.0
Em
H_delta
4101.734
4092.0
4111.0
Em
H_gamma
4340.464
4330.0
4350.0
Em
OIII_4363
4363.210
4350.0
4378.0
Em
H_beta
4861.325
4851.0
4871.0
Em
OIII_4959
4958.911
4949.0
4969.0
Em
OIII_5007
5006.843
4997.0
5017.0
Em
HeI_5876
5875.67
5866.0
5886.0
Em
OI_6300
6300.304
6290.0
6310.0
Em
NII_6548
6548.040
6533.0
6553.0
Em
H_alpha
6562.800
6553.0
6573.0
Em
NII_6584
6583.460
6573.0
6593.0
Em
SII_6717
6716.440
6704.0
6724.0
Em
SII_6731
6730.810
6724.0
6744.0
Em
ArIII7135
7135.8
7130.0
7140.0
Em
Ca_K 
3933.66
3919.0
3949.0
IS
Ca_H
3968.45
3953.0
3983.0
IS
Na_D
5891.94
5881.0
5906.0
IS

Line Centers in air from "The Atomic Line List v2.04"
Em = emission, IS = interstellar absorption