J/AJ/170/90 New redshifts for SDSS galaxies from visual inspection (Yagi+, 2025)
Reidentification of redshifts of SDSS galaxies overlapped with galactic objects.
Yagi M., Iye M., Fukumoto H.
<Astron. J., 170, 90 (2025)>
=2025AJ....170...90Y 2025AJ....170...90Y
ADC_Keywords: Galaxy catalogs; Galaxies, spectra; Redshifts; Photometry, SDSS
Keywords: Catalogs ; Redshift surveys ; Galaxies
Abstract:
This work presents a catalog of reidentified redshifts of 853 galaxies
for which the redshifts of overlapping foreground objects were
registered in the Sloan Digital Sky Survey (SDSS) DR16 Database. We
examined SDSS DR16 spectra of the candidates contaminated by
foreground Galactic stars and reidentified their galaxy redshift
features, such as Hα and other emission lines or absorption
lines. Comparisons of redshifts measured at neighboring fibers,
previous SDSS fits, and other published literature showed that our
reidentification of redshift would be accurate to within 0.001. For
the redshift range, 0<z<0.35, at least 0.1% of galaxies overlap
with Galactic stars, and SDSS DR16 assigns the redshift of the
foreground object, not the galaxies.
Description:
The samples, totaling 853 galaxies, are selected from the Sloan
Digital Sky Survey Data Release 16 (SDSS DR16, V/154) using three
different sets of criteria. We visually inspected SDSS jpeg images
with spectroscopic fitting by SDSS. DR16 is the fourth data release of
the fourth phase of SDSS (SDSS-IV). DR16 contains SDSS observations
through August 2018.
1) Spectroscopic STAR. We picked up objects from SDSS DR16 with the
spectroscopic class "STAR" that satisfy specific criteria (see Section
2.1). In total, 53031 objects with redshifts spanning between
-0.004460≤z≤0.004621 satisfied our criteria. We cut it down to 9927
by applying an additional criteria on magnitude and, after visually
inspecting all of them, we found 841 out of 9927 objects (8.5%) had a
new redshift that should be used for the galaxy.
2) Spectroscopic not STAR. This query on the the "no STAR" class
returned 2716 objects. Only five were galaxies with a new redshift
component.
3) Spin Study. In Fukumoto+2025 (in prep), we cross identified
SDSS DR16 spectroscopic data at z<0.05 with the galaxies in PanSTARRS1
(PS1) DR2 (II/389). We removed compact objects by visual inspection of
PS1 i-band images. We also noticed that some galaxies in Galaxy Zoo 1
(Lintott+2011, J/MNRAS/410/166), which have spin information, also
have incorrectly small redshifts.
In SDSS, some galaxies have more than one redshift measurement at
different positions of the galaxy. We downloaded 40" square postage
stamps with spectroscopic fiber marks overlaid, and visually checked
them for the presence of another spectroscopic measurement in the same
galaxy. Foreground stars and neighboring galaxies are not included.
Among the 853 galaxies, 58 galaxies have other spectroscopic
information. Nine out of the 58 have two fibers in the same galaxy,
and one of them has three fibers.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 61 853 Redshifts measured in this study
table3.dat 56 69 Redshifts for SDSS fibers at different positions in
galaxies
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See also:
II/389 : The Pan-STARRS release 1 (PS1) Survey - DR2 (Magnier+, 2025)
V/154 : Sloan Digital Sky Surveys (SDSS), Release 16 (DR16) (Ahumada+, 2020)
J/MNRAS/410/166 : Morphological types from Galaxy Zoo 1 (Lintott+, 2011)
J/MNRAS/444/2456 : Spectral galaxy pairs from SDSS DR9 (Yang+, 2014)
J/ApJ/907/123 : Spin Parity of Spiral Galaxies. III. (Iye+, 2021)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- SpecObjID SDSS DR16 (V/154) SpecObj ID (specobjid) (1)
21- 29 F9.5 deg RAdeg SDSS DR16 (V/154) Right Ascension of fiber
(J2000)
31- 40 F10.6 deg DEdeg SDSS DR16 (V/154) Declination of fiber
(J2000)
42- 50 F9.6 --- zSDSS [-4.4e-3/4.7e-3] SDSS DR16 (V/154) redshift
52- 57 F6.4 --- z [2.5e-3/0.331] Redshift from this study
59 I1 --- Type [1-3] Selection type (selection) (2)
61 I1 --- zClass [1-5] Class of the redshift estimation
(class) (3)
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Note (1): The links to the online SDSS-DR16 data are done by position. To
ensure it is the right object, verify that the online SDSS-DR16 SpecObjID
(which is different from the SDSS ObjID) matches the one in the VizieR
catalog.
Note (2): Selection type as follows:
1 = Spectroscopic STAR (841 occurrences)
2 = Spectroscopic not STAR and -0.005<z<0.005 (5 occurrences)
3 = Supplementary objects from Spin Study (7 occurrences)
Note (3): Class of redshift estimation as follows:
1 = Halpha emission and two or more emission lines (773 occurrences)
2 = Halpha emission and another emission line, supported by absorption lines
(14 occurrences)
3 = Halpha emission supported by several absorption lines (3 occurrences)
4 = unclear Halpha, while clear [NII], [OII], or [OIII] for redshift
(42 occurrences)
5 = no or weak Halpha emission, and redshift is estimated from absorption
lines (21 occurrences)
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- SpecObjID SDSS DR16 (V/154) SpecObj ID (specobjid)
21- 26 F6.4 --- z [3.3e-3/0.19] Redshift from this study
28- 47 A20 --- SpecObjIDfib SDSS DR16 (V/154) SpecObj ID of a nearby
fiber (specobjid2)
49- 56 F8.6 --- zSDSSfib [3.3e-3/0.19] Redshift of objIDfib
(zSDSS2)
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History:
From electronic version of the journal
License: CC-BY-4.0
(End) Prepared by [AAS], Robin Leichtnam [CDS] 09-Jun-2026