J/A+A/710/A145 COUGS-DESI Polar-Structure Galaxies in DESI (Bahr+, 2026)
COUGS-DESI: A Catalog of Unusual Galaxies with polar Structures in the
DESI Legacy Imaging Surveys
Bahr S.K.H., Mosenkov A.V., Guerrette J.A., Jensen I.H., George J.X.,
Spigarelli T.E., Smith R.P., Burton B.T., Beckstead K.W., Seguine J.D.,
Casper H.K., Pineda N., Holland M.
<Astron. Astrophys. 710, A145 (2026)>
=2026A&A...710A.145B 2026A&A...710A.145B (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, optical ; Galaxies, peculiar ; Galaxy catalogs ;
Morphology ; Photometry, classification ; Cross identifications ;
Positional data ; Extinction ; Redshifts ; Magnitudes, absolute
Keywords: methods: data analysis - techniques: image processing - atlases -
catalogs - surveys - galaxies: peculiar
Abstract:
Polar-structure galaxies (PSGs) host photometrically and kinematically
decoupled components oriented at large angles to one another. These
systems, which include polar rings, polar disks, polar halos, polar
bulges, polar dust lanes, and polar tidal structures, provide valuable
insights into galaxy formation and evolution, although their rarity
has limited statistical studies.
We aim to construct the largest and most homogeneous catalog of PSGs
to date in order to enable robust statistical studies of their
properties and occurrence rates in the local Universe. Using DESI
Legacy Imaging Surveys (DR10) data, we identified PSG candidates in
the Siena Galaxy Atlas (SGA) through visual inspection, convolutional
neural network classification, and cross-matching with previously
reported systems. Each galaxy was assigned a PSG subtype and host
morphology. We analyzed general properties of PSGs and compared them
with those for all galaxies in the SGA. Simple image simulations were
used to evaluate projection effects.
The resulting Catalog of Unusual Galaxies with polar Structures in the
DESI Legacy Imaging Surveys (COUGS-DESI) contains 2989 PSG candidates,
including 342 previously known objects. Projection effects from random
galaxy overlaps are negligible. The sample spans a wide range of polar
morphologies, with 1113 polar rings, 75 polar bulges, 216 polar halos,
185 polar dust lanes, and 1315 polar tidal structures. PSGs constitute
2.2% of local non-dwarf galaxies, with polar rings representing 0.7%.
Approximately 1% of S0 galaxies in the SGA host polar rings, whereas
spirals constitute the most common morphological type among the PSG
hosts in our catalog.
COUGS-DESI increases the number of known PSG candidates by an order of
magnitude and provides a foundation for detailed studies of the
formation and evolution of polar structures.
Description:
Photometric parameters and morphological classifications for 2989
polar-structure galaxies in the DESI DR10 Legacy Imaging Surveys are
presented in cougs.dat. For each galaxy, equatorial coordinates,
morphological types of the polar structure(s) and host, alternate
identifiers, griz surface brightnesses at the 26mag/arcsec2
isophote with errors, griz 26mag/arcsec2 isophote radii with
errors, galactic extinctions, redshifts, distances, K-corrections,
absolute magnitudes, and physical sizes are given.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
cougs.dat 357 2989 Photometric and morphological parameters for our
polar structure galaxies sample
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See also:
J/A+A/702/A258 : Catalogue of inspected PRGs - CIPRG (Dobrycheva+, 2025)
J/A+A/408/873 : Gas and stellar kinematics in spirals (Corsini+, 2003)
J/MNRAS/526/4768 : Galaxy Zoo DESI (Walmsley+, 2023)
J/MNRAS/511/3063 : PS1 edge-on Galaxies catalog (Makarov+, 2022)
J/MNRAS/509/3966 : Galaxy Zoo DR1+2, DR5 and DeepL version (Walmsley+, 2022)
J/MNRAS/486/390 : Morphology of 16908 SDSS Stripe 82 galaxies
(Bottrell+, 2019)
J/MNRAS/456/1359 : IAC Stripe 82 Legacy Project: Photometry (Fliri+, 2016)
J/MNRAS/418/244 : SDSS-based Polar Ring Catalogue (Moiseev+, 2011)
J/MNRAS/410/166 : Morphological types from Galaxy Zoo 1 (Lintott+, 2011)
J/ApJ/787/24 : Structural parameters of true edge-on galaxies
(Bizyaev+, 2014)
J/ApJS/269/3 : Siena Galaxy Atlas 2020 (SGA-2020) (Moustakas+, 2023)
J/AJ/152/73 : Stellar nuclei and bulges of nearby S0 galaxies
(Sil'chenko+, 2016)
VII/292 : DESI Legacy Imaging Surveys DR8 photometric redshifts
(Duncan+, 2022)
VII/237 : HYPERLEDA. I. Catalog of galaxies (Paturel+, 2003)
VII/233 : 2MASS All-Sky Extended Source Catalog (XSC)
(IPAC-UMass, 2003-2006)
II/294 : The SDSS Photometric Catalog, Release 7
(Adelman-McCarthy+, 2009)
Byte-by-byte Description of file: cougs.dat
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Bytes Format Units Label Explanations
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1- 24 A24 --- Name Galaxy name in the COUGS v1 catalog
(NAME)
26- 44 A19 --- IAU IAU-designated galaxy identifier based
on RA and DEC (IAU_ID)
46- 56 F11.7 deg RAdeg Right ascension (J2000.0) of the galaxy
center (RA)
58- 68 F11.7 deg DEdeg Declination (J2000.0) of the galaxy
center (DEC)
70- 72 A3 --- TYPE1 Primary structural classification of the
PSG (PSGTYPE1) (4)
74- 76 A3 --- TYPE2 Secondary structural classification of
the PSG (PSGTYPE2) (4)
78- 81 A4 --- Morph Host galaxy morphological type
(E, S0, S, Irr, M) (MORPHTYPE)
83- 89 I7 --- PGC ?=- Principal Galaxy Catalog identifier
(PGC)
91- 94 A4 --- MorphL Morphological classification from LEDA
(MORPHTYPE_LEDA)
96-102 I7 --- SGA ? ID number from the SGA catalog (SGA_ID)
104-109 F6.3 mag gmag ? g-band magnitude measured at 26 mag
arcsec-2 level (GMAGSB26_IRAF) (1)
111-115 F5.3 mag e_gmag ? Uncertainty of the g-band asymptotic
magnitude (GMAGSB26ERRIRAF)
117-122 F6.4 arcmin radgiso ? g-band isophotal radius at 26 mag
arcsec-2 (R26GIRAF)
124-129 F6.4 arcmin e_radgiso ? Uncertainty of the g-band isophotal
radius at 26 mag arcsec^-2
(R26GERR_IRAF)
131-137 F7.4 mag rmag ? r-band magnitude measured at 26 mag
arcsec-2 level (RMAGSB26_IRAF) (1)
139-144 F6.4 mag e_rmag ? Uncertainty of the r-band asymptotic
magnitude (RMAGSB26ERRIRAF)
146-152 F7.4 arcmin radriso ? r-band isophotal radius at 26 mag
arcsec^-2 (R26RIRAF)
154-159 F6.4 arcmin e_radriso ? Uncertainty of the r-band isophotal
radius at 26 mag arcsec^-2
(R26RERR_IRAF)
161-166 F6.3 mag imag ? i-band magnitude measured at 26 mag
arcsec-2 level (IMAGSB26_IRAF) (1)
168-172 F5.3 mag e_imag ? Uncertainty of the i-band asymptotic
magnitude (IMAGSB26ERRIRAF)
174-179 F6.4 arcmin radiiso ? i-band isophotal radius at 26 mag
arcsec^-2 (R26IIRAF)
181-186 F6.4 arcmin e_radiiso ? Uncertainty of the i-band isophotal
radius at 26 mag arcsec^-2
(R26IERR_IRAF)
188-193 F6.3 mag zmag ? z-band magnitude measured at 26 mag
arcsec-2 level (ZMAGSB26_IRAF) (1)
195-199 F5.3 mag e_zmag ? Uncertainty of the z-band asymptotic
magnitude (ZMAGSB26ERRIRAF)
201-206 F6.4 arcmin radziso ? z-band isophotal radius at 26 mag
arcsec^-2 (R26ZIRAF)
208-213 F6.4 arcmin e_radziso ? Uncertainty of the z-band isophotal
radius at 26 mag arcsec^-2
(R26ZERR_IRAF)
215-219 F5.3 mag Ag Galactic extinction in g band (A_G) (2)
221-225 F5.3 mag Ar Galactic extinction in r band (A_R) (2)
227-231 F5.3 mag Ai Galactic extinction in i band (A_I) (2)
233-237 F5.3 mag Az Galactic extinction in z band (A_Z) (2)
239-247 F9.6 --- z ? Final adopted redshift (REDSHIFT)
249-268 A20 --- n_z Name of the column that supplied
REDSHIFT for that row (REDSHIFT_SOURCE)
270-275 F6.2 Mpc DA ? Angular diameter distance (DA)
277-281 F5.3 kpc/arcsec Scale ? Physical scale (SCALE)
283-289 F7.2 Mpc DL ? Luminosity distance (DL)
291-296 F6.3 mag Kcorg ? K-corrections in g band (KCOR_G) (3)
298-303 F6.3 mag Kcorr ? K-corrections in r band (KCOR_R) (3)
305-311 F7.3 mag Kcori ? K-corrections in i band (KCOR_I) (3)
313-318 F6.3 mag Kcorz ? K-corrections in z band (KCOR_Z) (3)
320-326 F7.3 mag gMAG ? Absolute magnitude in g band corrected
for Galactic extinction and K-correction
(M_G)
328-334 F7.3 mag rMAG ? Absolute magnitude in r band corrected
for Galactic extinction and K-correction
(M_R)
336-342 F7.3 mag iMAG ? Absolute magnitude in i band corrected
for Galactic extinction and K-correction
(M_I)
344-350 F7.3 mag zMAG ? Absolute magnitude in z band corrected
for Galactic extinction and K-correction
(M_Z)
352-357 F6.2 kpc rMajAxis ? Physical semi-major axis at the r-band
SB26 level (PHYSSMASB26)
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Note (1): Calculated using IRAF.
Note (2): Galactic extinctions based on Schlafly & Finkbeiner
(2011ApJ...737..103S 2011ApJ...737..103S).
Note (3): Calculated using K-corrections calculator.
Note (4): All polar structures are primarily identified by a near-orthogonal
orientation relative to the major axis of their host galaxy.
Further distinctions between polar structure subtypes
are as follows:
EW = Extreme warps are highly tilted or warped stellar disks,
not inclined, enough to be true polar structures,
81 TYPE1 and 17 TYPE 2 occurences in our sample
PB = polar bulge are small, faint, prolate central component in a
disk galaxy, 75 occurences in our sample
PDL = polar dust lane are distinct dust lanes without any prominent
stellar counterpart, 185 TYPE1 and 117 TYPE2 occurences in
our sample
PH = polar halo are smooth, symmetrical, oval-shaped outer structure
(halo or shell), potentially representing unresolved complex
structures, 216 TYPE1 and 5 TYPE2 occurences in our sample
PR = polar ring are complete, closed ring or disk symmetrically
centered on host galaxy, 1113 TYEP1 and 23 TYPE2 occurences
in our sample
PTS = polar tidal structure are tidal features that cross the host
at a large inclination, typically double-sided but not
necessarily symmetric, often exhibiting nearly closed loops,
multiple rings or loops, off-center positions, or tidally
disrupted satellites, 1315 TYPE1 and 645 TYPE2 occurences
in our sample
X = X-shaped bulges are elongated in the vertical direction,
4 TYPE1 and 1 TYPE2 occurences in our sample
In addition to the polar structure subtypes listed above, COUGS-DESI
includes EW and X which are representative but incomplete samples
of related objects can appear similar to PSGs.
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History:
From electronic version of the journal
Acknowledgements:
Seneca Bahr, hsenecak(at)byu.edu
License: CC-BY-4.0
(End) Seneca Bahr [BYU], Luc Trabelsi [CDS] 23-Apr-2026