SDSS Data Products: "gal_idxfix"

This binary structure contains measurements of stellar absorption line indices (Lick indices) corrected for sky lines using the best-fit model spectrum to interpolate over the sky line contamination. The file also contains the red and blue bandpass fluxes separately.

The problem with the standard index measurements is that they are sensitive to telluric sky line contamination. This leads to significantly increased scatter in their values at certain redshifts. Empirically it is only possible to see this for the oxygen lines at 5577Å and 6300Å so only these have been considered.

To carry out the interpolation we use the best-fit model spectrum to the continuum - but only across the wavelength gap affected by the sky lines. By looking at the data we adopted a 10Å wide range around each sky line as the relevant region to interpolate across.

Tag Name

Data Type / Units

Description

plateid
int[1]
Plate id
fiberid
int[1]
Fiber number (1-640)
z float[1] Redshift
(index_name)_sub
float[1]
Restframe index measurement on the data after subtracting all 3-sigma emission lines
(index_name)_sub_err
float[1]
Error in the above index measurement
(index_name)_sub_fb float[1] The flux through the blue bandpass
(index_name)_sub_fr float[1] The flux through the red bandpass
(index_name)_sub_fb_err float[1]
The error on the flux through the blue bandpass
(index_name)_sub_fr_err float[1]
The error on the flux through the red bandpass
(index_name)_sub_flag byte[1]
A flag indicating whether the index has been interpolated or not. A value of 0 means no interpolation has taken place. A 1 indicates that the blue bandpass has been interpolated, a 2 indcates interpolation in the red bandpass and a 9 means that the central bandpass has been interpolated.


Index Name Index bandpass Blue continuum bandpass Red continuum bandpass Units
Lick_CN1 4142.125 - 4177.125 4080.125 - 4117.625 4244.125 - 4284.125 mag
Lick_CN2 4142.125 - 4177.125 4083.875 - 4096.375 4244.125 - 4284.125 mag
Lick_Ca4227 4222.250 - 4234.750 4211.000 - 4219.750 4241.000 - 4251.000 A
Lick_G4300 4281.375 - 4316.375 4266.375 - 4282.625 4318.875 - 4335.125 A
Lick_Fe4383 4369.125 - 4420.375 4359.125 - 4370.375 4442.875 - 4455.375 A
Lick_Ca4455 4452.125 - 4474.625 4445.875 - 4454.625 4477.125 - 4492.125 A
Lick_Fe4531 4514.250 - 4559.250 4504.250 - 4514.250 4560.500 - 4579.250 A
Lick_C4668 4634.000 - 4720.250 4611.500 - 4630.250 4742.750 - 4756.500 A
Lick_Hb 4847.875 - 4876.625 4827.875 - 4847.875 4876.625 - 4891.625 A
Lick_Fe5015 4977.750 - 5054.000 4946.500 - 4977.750 5054.000 - 5065.250 A
Lick_Mg1 5069.125 - 5134.125 4895.125 - 4957.625 5301.125 - 5366.125 mag
Lick_Mg2 5154.125 - 5196.625 4895.125 - 4957.625 5301.125 - 5366.125 mag
Lick_Mgb 5160.125 - 5192.625 5142.625 - 5161.375 5191.375 - 5206.375 A
Lick_Fe5270 5245.650 - 5285.650 5233.150 - 5248.150 5285.650 - 5318.150 A
Lick_Fe5335 5312.125 - 5352.125 5304.625 - 5315.875 5353.375 - 5363.375 A
Lick_Fe5406 5387.500 - 5415.000 5376.250 - 5387.500 5415.000 - 5425.000 A
Lick_Fe5709 5696.625 - 5720.375 5672.875 - 5696.625 5722.875 - 5736.625 A
Lick_Fe5782 5776.625 - 5796.625 5765.375 - 5775.375 5797.875 - 5811.625 A
Lick_NaD 5876.875 - 5909.375 5860.625 - 5875.625 5922.125 - 5948.125 A
Lick_TiO1 5936.625 - 5994.125 5816.625 - 5849.125 6038.625 - 6103.625 mag
Lick_TiO2 6189.625 - 6272.125 6066.625 - 6141.625 6372.625 - 6415.125 mag
Lick_Hd_A 4083.500 - 4122.250 4041.600 - 4079.750 4128.500 - 4161.000 A
Lick_Hg_A 4319.750 - 4363.500 4283.500 - 4319.750 4367.250 - 4419.750 A
Lick_Hd_F 4091.000 - 4112.250 4057.250 - 4088.500 4114.750 - 4137.250 A
Lick_Hg_F 4331.250 - 4352.250 4283.500 - 4319.750 4354.750 - 4384.750 A
DTT_CaII8498 8483.000 - 8513.000 8447.500 - 8462.500 8842.500 - 8857.500 A
DTT_CaII8542 8527.000 - 8557.000 8447.500 - 8462.500 8842.500 - 8857.500 A
DTT_CaII8662 8647.000 - 8677.000 8447.500 - 8462.500 8842.500 - 8857.500 A
DTT_MgI8807 8799.500 - 8814.500 8775.000 - 8787.000 8845.000 - 8855.000 A
BH_CNB 3810.000 - 3910.000 3785.000 - 3810.000 3910.000 - 3925.000 mag
BH_HK 3925.000 - 3995.000 3910.000 - 3925.000 3995.000 - 4010.000 mag
BH_CaI 4215.000 - 4245.000 4200.000 - 4215.000 4245.000 - 4260.000 mag
BH_G 4285.000 - 4315.000 4275.000 - 4285.000 4315.000 - 4325.000 mag
BH_Hb 4830.000 - 4890.000 4800.000 - 4830.000 4890.000 - 4920.000 mag
BH_MgG 5150.000 - 5195.000 5125.000 - 5150.000 5195.000 - 5220.000 mag
BH_MH 4940.000 - 5350.000 4740.000 - 4940.000 5350.000 - 5550.000 mag
BH_FC 5250.000 - 5280.000 5225.000 - 5250.000 5280.000 - 5305.000 mag
BH_NaD 5865.000 - 5920.000 5835.000 - 5865.000 5920.000 - 5950.000 mag
D4000

3750.000 - 3950.000
4050.000 - 4250.000

D4000_n

3850.000 - 3950.000
4000.000 - 4100.000

Balmer_Break
Not correctly implemented




Lick indices from Worthey et al., 1994, ApJS, 94, 687 and Worthey and Ottaviani, 1997, ApJS, 111, 377
BH indices from Brodie and Hanes (see Huchra et al. 1996, ApJS, 102, 29)
DTT indices from Diaz, Terlevich, & Terlevich, 1989, MNRAS, 239, 325
D4000 is from Bruzual, 1983, ApJ, 273, 105
D4000_n is from Balogh et al. 1999, ApJ, 527, 54