J/MNRAS/482/2627 Isolated galaxy triplets in the local universe (Tawfeek+, 2019)
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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    (SIMBAD/NED BibCode)
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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 (r_h_) 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, 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). Triplet systems (in this selected catalogue) are
    restricted to have members with spectroscopic information, r-band
    model magnitudes (m_r_) 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,
    Cat. J/A+A/578/A110) based their isolation criterion on galaxies with
    no neighbours within radial velocity difference {Delta}v=<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, m_r_, in the r band;
    k-correction; the luminosity distance, D_L_; the photometric and
    spectroscopic redshifts) were extracted from CasJobs tool in SDSS DR12
    (Alam et al. 2015ApJS..219...12A, Cat. V/147). These parameters are
    helpful in estimating other basic parameters such as the absolute
    magnitude (M_r_) 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
          ({sigma}) following the expression: {sigma}=sqrt(<v^2^>-<v>^2^)
          (Chernin et al. 2000MNRAS.319..851C; Schneider 2006eac..book.....S;
          Duplancic et al. 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=9{pi}R{sigma}^2^/2G
          Where G is the gravitational constant, R can be considered to be the
          mean harmonic separation rh in meters, and {sigma} is the velocity
          dispersion in m/s (Chernin et al. 2000MNRAS.319..851C;
          Vavilova et al. 2005KFNT...21a...3V; Liljeblad 2012, Estimating masses
          of galaxy clusters, Chalmers University of Technology, Gothenburg,
          Sweden, p. 3; Duplancic et al. 2015MNRAS.447.1399D)
Note (4): The luminosity of each galaxy in r-band (Lr) is computed using the
          equation: Lr=dex[0.4(M_{sun},r_-Mr)],
          where M_{sun},r_ and Mr are the solar and galactic absolute magnitudes
          in the r band, respectively (Binney & Tremaine 1987Natur.326..219B;
          Ali G., 2001, PhD thesis, Univ. Cairo; Schneider 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=2<v>sin({theta}_ik_/2)/H_0_,
          where v=cz and {theta}_ik_ 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=3{Sigma}rp_ik_, where i, k = 1, 2, 3; i!=k
          (Chernin et al. 2000MNRAS.319..851C;
          Vavilova et al. 2005KFNT...21a...3V; Feng et al. 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

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(End)                                           Ana Fiallos [CDS]    30-Jun-2022