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