J/MNRAS/481/2458 On the nature of small galaxy systems (Duplancic+, 2018)
On the nature of small galaxy systems.
Duplancic F., Coldwell G.V., Alonso S., Lambas D.G.
<Mon. Not. R. Astron. Soc., 481, 2458-2469 (2018)>
=2018MNRAS.481.2458D 2018MNRAS.481.2458D (SIMBAD/NED BibCode)
ADC_Keywords: Galaxy catalogs ; Surveys ; Photometry, SDSS ; Redshifts
Keywords: galaxies: groups: general - galaxies: interactions -
galaxies: statistics
Abstract:
We aim at defining homogeneous selection criteria of small galaxy
systems in order to build catalogues suitable to compare main
properties of pairs, triplets, and groups with four or more members.
To this end we use spectroscopic and photometric Sloan Digital Sky
Survey (SDSS) data to identify systems with a low number of members.
We study global properties of these systems and the properties of
their member galaxies finding that galaxies in groups are
systematically redder and with lower star formation activity
indicators than galaxies in pairs which have a higher fraction of
star-forming galaxies. Triplet galaxies present intermediate trends
between pairs and groups. We also find an enhancement of star
formation activity for galaxies in small systems with companions
closer than 100kpc, irrespective of the number of members. We have
tested these analyses on SDSS mock catalogues derived from the
Millennium simulation, finding as conservative thresholds 76 per cent
completeness and a contamination of 23 per cent in small galaxy
systems, when considering an extreme case of incompleteness due to
fiber collisions. Nevertheless, we also found that the results
obtained are not likely affected by projection effects. Our studies
suggest that an extra galaxy in a system modify the properties of the
member galaxies. In pairs, galaxy-galaxy interactions increase gas
density and trigger starbursts. However, repeated interactions in
triplets and groups can generate gas stripping, turbulence, and shocks
quenching the star formation in these systems.
Description:
We present a catalogue of small galaxy systems derived from SDSS-DR14
spectroscopic and photometric data. The catalogue comprises systems
with a low number of members (two to six) populating environments that
promote galaxy-galaxy interactions and mergers.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 92 10929 Main properties of small galaxy systems
tablea2.dat 94 22846 Galaxy properties of small galaxy systems members
--------------------------------------------------------------------------------
See also:
V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
http://www.sdss.org/ : SDSS home page
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 --- ID System Identifier
10- 18 F9.5 deg RAdeg System Centre Right Ascension (J2000)
22- 30 F9.5 deg DEdeg System Centre Declination (J200)
36- 42 F7.5 --- zave Average redshift of the System (1)
46 I1 --- Nm [2/6] Number of members in the system
53 I1 --- Nspec [1/6] Number of spectroscopic members in
the system
60- 68 F9.5 km/s dVmax ?=-99.99 Maximum radial velocity difference (2)
72- 80 F9.5 kpc R System radius (3)
86- 92 F7.5 --- drmag System magnitude difference (4)
--------------------------------------------------------------------------------
Note (1): Average redshift of the system calculating by using only
spectroscopic members
Note (2): Absolute value of the maximum radial velocity difference between
spectroscopic system members.
If the system has only one spectroscopic member dVmax=-99.99
Note (3): Calculated as the projected distance from the system geometric centre
to the most distant galaxy member.
Note (4): Absolute value of the r-band absolute magnitude difference between
the brightest and the faintest galaxy in the system.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 --- ID System Identifier
9 I1 --- idgx [1/6] Galaxy identifier within the system (1)
15 I1 --- Nm [2/6] Number of members in the system
21 A1 --- idsp [0/1] Spectroscopic/photometric flag (2)
28- 46 I19 --- objID SDSS long object identification
50- 58 F9.5 deg RAdeg Right Ascension (J2000)
62- 70 F9.5 deg DEdeg Declination (J2000)
76- 82 F7.5 --- z Galaxy redshift (3)
86- 94 F9.5 mag rMAG r-band absolute magnitude of the galaxy (4)
--------------------------------------------------------------------------------
Note (1): If the system has N members then idgx range from 1 to N being
idgx=1 the brightest galaxy in the system and idgx=N the faintest one.
Note (2): Spectroscopic/photometric flag as follows:
0 = the galaxy is spectroscopic
1 = the galaxy is photometric
Note (3): If idsp=0 it is spectroscopic redshift,
if idsp=1 it is photometric redshift.
Note (4): SDSS r-band model magnitude corrected by extinction and k-correction.
--------------------------------------------------------------------------------
Acknowledgements:
Fernanda Duplancic, fduplancic(at)unsj-cuim.edu.ar
(End) Patricia Vannier [CDS] 12-Apr-2021