J/MNRAS/482/2627 Isolated galaxy triplets in the local universe (Tawfeek+, 2019)
Fundamental parameters of isolated galaxy triplets in the local universe:
statistical study.
Tawfeek A.A., Ali G.B., Takey A., Awad Z., Hayman Z.M.
<Mon. Not. R. Astron. Soc., 482, 2627-2643 (2019)>
=2019MNRAS.482.2627T 2019MNRAS.482.2627T (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; Galaxy catalogs ; Positional data ; Redshifts ;
Velocity dispersion
Keywords: galaxies: fundamental parameters - galaxies: groups: general -
galaxies: statistics
Abstract:
Understanding the dynamics of galaxy triplet systems is one of the
significant ways of obtaining insight into the dynamics of large
galaxy clusters. Towards that aim, we present a detailed study of all
isolated triplet systems (total of 315) taken from the 'SDSS-based
catalogue of Isolated Triplets' (SIT). In addition, we compared our
results with those obtained for a sample of triplets from the Local
Supercluster, SDSS-triplets, Tully's catalogue, Wide (W) and Compact
(K)-triplets. In addition, we performed the correlation between the
dynamical parameters and the large-scale structure (LSS).
Interestingly, we found that there is no correlation between both the
mean projected separation for the triplet systems and the LSS and its
dynamical parameters. Furthermore, we found that only 3 per cent of
these systems can be considered as compact since the mean harmonic
separation (rh) is more than 0.4Mpc for 97 per cent of the
population. Thus, we may conclude that mergers might not have played a
dominant role in their evolution.
Description:
We conduct a statistical study on 315 galaxy triplet systems taken
from the SIT catalogue by Argudo-Fernandez et al.
(2015A&A...578A.110A 2015A&A...578A.110A, Cat. J/A+A/578/A110). This catalogue is based on
the Sloan Digital Sky Survey-Tenth Data Release (SDSS-DR10; Ahn et al.
2014ApJS..211...17A 2014ApJS..211...17A). Triplet systems (in this selected catalogue) are
restricted to have members with spectroscopic information, r-band
model magnitudes (mr) in the range 14.5=<m_r=<17.7 over a redshift
range 0.006=<z=<0.080. Argudo-Fernandez et al. (2015A&A...578A.110A 2015A&A...578A.110A,
Cat. J/A+A/578/A110) based their isolation criterion on galaxies with
no neighbours within radial velocity difference Δv=<500km/s,
and all galaxies are found within Mpc radius (d=<1Mpc). In addition,
they performed a star-galaxy separation in order to prevent
classifying a star as a galaxy and removed multiple identifications of
the same galaxy. Following this criteria they compiled a catalogue of
315 isolated triplet systems.
The observational parameters (apparent magnitude, mr, in the r band;
k-correction; the luminosity distance, DL; the photometric and
spectroscopic redshifts) were extracted from CasJobs tool in SDSS DR12
(Alam et al. 2015ApJS..219...12A 2015ApJS..219...12A, Cat. V/147). These parameters are
helpful in estimating other basic parameters such as the absolute
magnitude (Mr) in r band and the radial velocity. The SDSS-DR12 is
the final data release of the SDSS-III that contains observations up
to 2014 July.
Table A1 lists the main computed parameters for the 315 studied galaxy
triplet systems.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 55 315 Computed basic parameters of the 315 studied
triplet systems in the SIT catalogue
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See also:
V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- ID System identification
5- 11 F7.3 deg RAdeg Right ascension (J2000) (1)
13- 18 F6.3 deg DEdeg Declination (J2000) (1)
20- 24 F5.3 --- z Redshift
26- 31 F6.2 km/s sigma Velocity dispersion (2)
33- 36 F4.2 10+12Msun Mvir Viral Mass (3)
38- 43 F6.2 Msun/Lsun Mvir/Lr Mass-to-light ratio (4)
45- 48 F4.2 Mpc rp Mean projected separation (5)
50- 53 F4.2 Mpc rh Mean harmonic separation (6)
55 A1 --- f_ID Flag on the system status (7)
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Note (1): Positions of the brightest galaxy in the system
Note (2): After estimating the radial velocity (v) of the three galaxies in a
triplet system, we can compute the system velocity dispersion
(σ) following the expression: σ=sqrt(<v2>-2)
(Chernin et al. 2000MNRAS.319..851C 2000MNRAS.319..851C; Schneider 2006eac..book.....S 2006eac..book.....S;
Duplancic et al. 2015MNRAS.447.1399D 2015MNRAS.447.1399D).
Note (3): For a system of 3 members occupied in a circle of minimum radius R,
which contains the centres of these members, the virial mass is given
by: Mvir=9πRσ2/2G
Where G is the gravitational constant, R can be considered to be the
mean harmonic separation rh in meters, and σ is the velocity
dispersion in m/s (Chernin et al. 2000MNRAS.319..851C 2000MNRAS.319..851C;
Vavilova et al. 2005KFNT...21a...3V 2005KFNT...21a...3V; Liljeblad 2012, Estimating masses
of galaxy clusters, Chalmers University of Technology, Gothenburg,
Sweden, p. 3; Duplancic et al. 2015MNRAS.447.1399D 2015MNRAS.447.1399D)
Note (4): The luminosity of each galaxy in r-band (Lr) is computed using the
equation: Lr=dex[0.4(M☉,r-Mr)],
where M☉,r and Mr are the solar and galactic absolute magnitudes
in the r band, respectively (Binney & Tremaine 1987Natur.326..219B 1987Natur.326..219B;
Ali G., 2001, PhD thesis, Univ. Cairo; Schneider 2006eac..book.....S 2006eac..book.....S).
Note (5): Projected separation is defined as the minimum separation between two
celestial objects. We can estimate the projected separation between
each of the two galaxies in the triplet systems using the generalized
equation rp=2sin(θik/2)/H0,
where v=cz and θik is the angular separation between the
members of each triplet system, i, k = 1, 2, 3; i!=k.
Note (6): The general formula of the mean harmonic separation (rh) is expressed
in terms of the number of galaxies in a given group or cluster. For
triplet galaxies rh=3Σrpik, where i, k = 1, 2, 3; i!=k
(Chernin et al. 2000MNRAS.319..851C 2000MNRAS.319..851C;
Vavilova et al. 2005KFNT...21a...3V 2005KFNT...21a...3V; Feng et al. 2016RAA....16...72F 2016RAA....16...72F).
Note (7): Flag as follows:
k = compact triplet system
w = wide triplet system
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 30-Jun-2022