J/A+A/712/A55 Galaxy groups within voids (Argudo-Fernandez+, 2026)
Galaxy groups within voids.
Argudo-Fernandez M., Torres-Rios G., Vasquez-Bustos P., Verley S., Perez I.,
Duarte Puertas S., Jimenez A., Garcia-Benito R., Zurita A.,
Alcazar-Laynez M., Bidaran B., Conrado A., Espada D., Florido E.,
Gonzalez Delgado R., Hernandez-Sanchez M., del Moral-Castro I., Roman J.,
Sanchez-Menguiano L., Subramanian S., Villalba-Gonzalez P.
<Astron. Astrophys. 712, A55 (2026)>
=2026A&A...712A..55A 2026A&A...712A..55A (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, group ; Morphology ; Redshifts ; Photometry ; Optical
Keywords: galaxies: evolution - galaxies: fundamental parameters -
galaxies: general - galaxies: groups: general -
large-scale structure of Universe
Abstract:
Despite cosmic voids being vast and almost empty, galaxy aggregations
do exist within them, although they are much sparser than in denser
regions like walls, filaments and clusters. The internal matter
distribution within voids might have an impact on the properties and
evolution of void galaxies.
In this work, we aim to identify and characterise a sample of galaxy
groups within voids in the local Universe (z<0.08), taking into
account the peculiarities of these vast and empty structures.
The void galaxies used in this study are selected from a well-defined
void galaxy sample, from which the parent sample of the Calar Alto
Void Integral-field Treasury surveY (CAVITY) legacy project was drawn.
To identify galaxy groups, we applied a fiends-of-friends (FoF) like
group finder algorithm to the selected sample, ensuring a certain
degree of gravitational binding among group members. The same
algorithm has been applied to identify a control sample of groups not
in clusters nor voids, referred as NCNV groups.
The catalogue of groups consists on 1367 physically bound groups, with
a total of 3040 galaxies, plus 14672 galaxy singlets. Most of the
galaxies in voids are singlets (59%), in contrast, most of the NCNV
galaxies in the control sample are in groups (60%). To consider the
dynamical stage of the groups we used the parameters harmonic radius
(RH), radial velocity dispersion (sigmavr2), dimensionless
crossing time (H0tc), and group virial mass (Mvir). We also used the
total optical (r-band) luminosity, L_r, to estimate the mass-to-light
ratio (M/L) of the groups. We studied the relations of void properties
and these parameters with the group richness.
Galaxy groups can be found in any void in the local Universe, with no
dependency of group richness on the density of voids. The densest
groups in the studied sample of voids are composed of six galaxies,
therefore, voids generally contain small groups, in comparison to
denser structures such as filaments, walls, and galaxy clusters.
Galaxy groups within voids are typically loose groups, in an early
stage of their evolution.
Description:
Catalogue of group galaxies, with galaxy positions, redshifts, and
optical magnitudes, as well as the catalogue of groups with group
richness, total stellar mass, total optical luminosity, and dynamical
parameters.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 60 17712 Catalogue of group galaxies
table3.dat 45 1367 Catalogue of groups in voids
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- GroupID [1/16039] Group identification
7- 10 I4 --- VoidID [18/1011] Void identification
12- 16 I5 --- CavityID [137/79944] CAVITY galaxy identification
18- 27 F10.6 deg RAdeg Right ascension (J2000.0)
29- 38 F10.6 deg DEdeg Declination (J2000.0)
40- 47 F8.6 --- z Redshift
49- 53 F5.2 mag rmag Apparent magnitude in the r-band
55- 60 F6.2 mag rMAG Absolute magnitude in the r-band
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- GroupID [1/1367] Group identification
6 I1 --- Ngal [2/6] Group richness
8- 12 F5.2 [Msun] Mtot Total stellar mass of the group
14- 18 F5.2 [Lsun] Ltot Total r-band luminosity of the group
20- 25 F6.2 km/s sigma Velocity dispersion
27- 32 F6.2 kpc Rh Harmonic radius
34- 39 F6.2 --- H0tc Crossing time
41- 45 F5.2 [Msun] Mvir Virial mass
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Acknowledgements:
Maria del Carmen Argudo-Fernandez, margudo(at)ugr.es
License: CC-BY-4.0
(End) Patricia Vannier [CDS] 01-Jul-2026