N(z) K-S test to identify bad fibers in jura

[rongpu]

Repeat the exercise in issue #1946, I have identified the following 15 fibers in jura with K-S test p-value less than 1e-4 for either BGS (14 fibers) or LRG (10 fibers): 466, 551, 552, 553, 725, 1008, 1098, 3234, 3235, 3250, 3504, 3969, 3994, 4720, 4891

Below are redshift vs date plots for these fibers:

FIBER 466 BGS

FIBER 551 BGS

FIBER 552 BGS LRG

FIBER 553 BGS LRG

FIBER 725 LRG

FIBER 1008 BGS LRG

FIBER 1098 BGS

FIBER 3234 BGS LRG

FIBER 3235 BGS LRG

FIBER 3250 BGS LRG

FIBER 3504 BGS LRG

FIBER 3969 BGS LRG

FIBER 3994 BGS LRG

FIBER 4720 BGS

FIBER 4891 BGS

[rongpu]

If I run the same test on the ELGs without the OII quality cuts, the K-S test finds 129 fibers with p-value below the (more restrictive) threshold of 2e-6. This large number of "bad" fibers are perhaps expected since 20-30% of the ELG targets are low-S/N featureless spectra, and their redshifts can be sensitive to subtle CCD defects (which can otherwise be ignored for any spectrum with reasonable S/N). Still there might be useful information in their redshift vs date plots, and they can be found here: https://data.desi.lbl.gov/desi/users/rongpu/redshift_qa/nz_ks_test/bad_fibers_from_nz-elg-zcatalog.html

Alternatively we can simply look at ELG spectra that pass the OII cuts (here instead of zcatalog, I use Ashley's LSS catalog which includes the OII columns). This flags 10 fibers with p-value<1e-4: 551, 1261, 1269, 1295, 1659, 1971, 1972, 2246, 3234, 3359 Since the OII cuts already removed most of the spurious redshifts, this list is almost certainly an incomplete list of fibers with low ELG redshift efficiency. The redshift vs date plots can be found here: https://data.desi.lbl.gov/desi/users/rongpu/redshift_qa/nz_ks_test/bad_fibers_from_nz-elg-lss_catalog.html