J/A+A/707/A302 Late-type galaxies morpho-kinematic class (Pacheco-Arias+, 2026)
New morpho-kinematic classification: The two-dimensional spatial distribution of
stellar specific angular momentum in late-type galaxies.
Pacheco-Arias J., Amram P., Epinat B., Mercier W.
<Astron. Astrophys. 707, A302 (2026)>
=2026A&A...707A.302P 2026A&A...707A.302P (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; Morphology ; Optical
Keywords: galaxies: kinematics and dynamics - Galaxies: evolution -
galaxies: fundamental parameters - galaxies: spiral -
galaxies: irregular - galaxies: structure
Abstract:
The two-dimensional spatial distribution of stellar specific angular
momentum (sAM) within galaxies has never been analyzed to date. We
seek to identify the morpho-kinematics of this property and its
correlation with the total stellar sAM (j*) and the total stellar mass
(M*) of late-type galaxies in the local universe.
We estimate the two-dimensional distribution of stellar sAM for 30
spiral and irregular galaxies, mostly located in nearby low-density
environments, part of the Gassendi Hα survey of SPirals (GHASP).
To do so, we produce for the first time, high-resolution stellar sAM
surface density (sAMSD) maps by using a formalism which combines the
3.4um WISE photometry with Hα velocity fields and rotation
curves. The features of these new maps are quantified using standard
non-parametric morphological indicators such as concentration,
asymmetry, and smoothness, augmented by two additional coefficients
that respectively measure the degree of similarity to an axisymmetric
Freeman disc and the prominence of bi-symmetric substructures within
the stellar sAMSD space.
Each galaxy in our sample is classified into one of the five new
morpho-kinematic categories proposed in this study: j*- ring, j*-
spiral, j*- bar, j*- clump and j*- irregular. These classes are named
after the predominant galactic substructure of their stellar sAMSD map
and form a new classification scheme that combines both morphological
characteristics and dynamic properties. For 14 galaxies, the
morphological classification does not coincide with the corresponding
morpho-kinematic category. As expected, there is a high correlation
between j* and M* for our sample. Similarly, our galaxies exhibit a
correlation between j* and their star formation rate, and between j*
and their total mass. The mean j* and M* are distributed along
different regions along the Fall relation for all j*- types, although
there is a considerable scatter within each type.
There is a link between the two-dimensional distribution of stellar
sAMSD and j*. The location of the different j*- types in the j*-M*
diagram could indicate a morpho-kinematic evolution of late-type
galaxies within the hierarchical paradigm of galaxy formation. The
physical mechanisms capable of modifying the shape of galaxies in the
stellar sAMSD space seem to be related with the stability of the
galactic disc. The spatial redistribution of angular momentum for
low-mass late-type galaxies may be driven by a combination of
feedback, dynamical friction, shock waves and resonances, while the
quasi-stationary rotating density wave can be responsible for the
aforementioned process in the massive spirals.
Description:
This catalogue contains geometrical, physical, and morpho-kinematic
parameters
derived for a sample of nearby galaxies using stellar specific angular
momentum surface density (sAMSD) maps.
The tables are organised following the same order as in the paper:
(1) average parameters by morpho-kinematic category,
(2) galaxy parameters,
(3) morpho-kinematic metrics.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 102 6 *Average parameters by morpho-kinematic category
tablea1.dat 92 30 Galaxy parameters
tablee1.dat 47 30 *Morpho-kinematic metrics
list.dat 79 30 List of fits maps
fits/* . 30 Individual fits maps
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Note on table1.dat: Mean values and 1-sigma dispersions are computed for each
morpho-kinematic category. The detailed definition of all morpho-kinematic
parameters is given in Sect. 4.1 and Appendix E of the paper.
Note on tablee1.dat: The morpho-kinematic metrics are measured on stellar
specific angular momentum surface density (sAMSD) maps. The detailed definition
of parameters R2, A2, C, A, and S is given in Sect. 4.1 of the paper.
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- Class Morpho-kinematic category
20- 21 I2 --- Ngal Number of galaxies in each category
23- 26 F4.2 --- Ttype Mean morphological type code
28- 31 F4.2 --- e_Ttype 1-sigma standard deviation of Ttype
33- 37 F5.2 [Msun] logMstar Mean stellar mass (log10)
39- 42 F4.2 [Msun] e_logMstar 1-sigma standard deviation of logMstar
44- 47 F4.2 [kpc.km/s] logjstar Mean stellar specific angular momentum
(log10)
49- 52 F4.2 [kpc.km/s] e_logjstar 1-sigma standard deviation of logjstar
54- 57 F4.2 --- R2 Mean ringness parameter
59- 62 F4.2 --- e_R2 1-sigma standard deviation of R2
64- 67 F4.2 --- A2 Mean bar predominance parameter
69- 72 F4.2 --- e_A2 1-sigma standard deviation of A2
74- 77 F4.2 --- C Mean concentration index
79- 82 F4.2 --- e_C 1-sigma standard deviation of C
84- 87 F4.2 --- A Mean asymmetry index
89- 92 F4.2 --- e_A 1-sigma standard deviation of A
94- 97 F4.2 --- S Mean smoothness index
99-102 F4.2 --- e_S 1-sigma standard deviation of S
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- UGC Name of the galaxy in the UGC catalogue
7- 18 A12 --- MType Morphological type from NED
21- 28 F8.4 deg RAdeg Right ascension of the photometric
centre (J2000) (1)
30- 37 F8.4 deg DEdeg Declination of the photometric
centre (J2000) (1)
39- 40 I2 deg Incl Kinematic inclination (2)
42- 43 I2 deg e_Incl Kinematic inclination error
45- 47 I3 deg PA Kinematic position angle (2)
49- 50 I2 deg e_PA Kinematic position angle error
53- 55 A3 --- n_PA Note on PA (3)
57- 61 F5.2 Mpc D Distance to the galaxy from Epinat et al.
(2008)
63- 67 F5.2 kpc Rmax Maximum radius (4)
69- 71 A3 --- n_Rmax Note on Rmax (5)
73- 77 F5.2 [Msun] logMstar Stellar mass computed using Eq. (8)
(log10)
79- 82 F4.2 [Msun] e_logMstar Stellar mass computed using Eq. (8)
(log10) error
84- 87 F4.2 [kpc.km/s] logjstar Total stellar specific angular momentum
computed using Eq. (6) (log10)
89- 92 F4.2 [kpc.km/s] e_logjstar Total stellar specific angular momentum
computed using Eq. (6) (log10) error
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Note (1): Right ascension and declination of the photometric centre determined
as the brightest pixel of the WISE W1-band image.
Note (2): Kinematic inclination and position angle derived from the velocity
field analysis of Epinat et al. (2008).
Note (3): Note as follows:
KIN = kinematic PA
Mor = photometric PA from HyperLeda replaces the kinematic PA for the
computation of stellar specific angular momentum
Note (4): Maximum radius defined using the criterion given in Eq. (9).
Note (5): Note as follows:
EXT = galaxies for which the rotation curve was extrapolated to reach Rmax
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Byte-by-byte Description of file: tablee1.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- UGC Name of the galaxy in the UGC catalogue
7- 21 A15 --- MKtype Morpho-kinematic type
23- 27 F5.2 --- R2 Ringness of the stellar sAMSD map
29- 32 F4.2 --- A2 Bar predominance of the stellar sAMSD map
34- 37 F4.2 --- C Concentration of the stellar sAMSD map
39- 42 F4.2 --- A Asymmetry of the stellar sAMSD map
44- 47 F4.2 --- S Smoothness of the stellar sAMSD map
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- UGC Name of the galaxy in the UGC catalogue
7- 15 F9.5 deg RAdeg Right Ascension of center (J2000)
16- 24 F9.5 deg DEdeg Declination of center (J2000)
26- 29 I4 --- Nx Number of pixels along X-axis
31- 34 I4 --- Ny Number of pixels along Y-axis
37- 40 I4 Kibyte size Size of FITS file
42- 65 A24 --- FileName Name of FITS file, in subdirectory fits
67- 79 A13 --- Title Title of the FITS file
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Acknowledgements:
Juan Pacheco-Arias, juan.pacheco(at)lam.fr
(End) Patricia Vannier [CDS] 27-Jan-2026