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D18 small galaxy systems center catalogue


Catalogue of small galaxy systems from SDSS-DR14


Fernanda Duplancic

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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 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 100 kpc, 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.


On the nature of small galaxy systems

Data Table Fields:

NameTable Head DescriptionUnitUCD
tile_name Tile id source tile name N/A meta.code;
ID Id System identifier N/A
Ra Ra J2000 right ascension of the system geometric deg pos.eq.ra;meta.main
Dec Dec J2000 declination of the system geometric deg pos.eq.dec;meta.main
zave Zave average redshift of the system calculating by using spectroscopic galaxies N/A src.redshift
Nm Nm number of members in the system N/A meta.number
nspec Nspec number of spectroscopic members in the system N/A meta.number
dVmax Dvmax absolute value of the maximum radial velocity difference between spectroscopic system members. If the system has only one spectroscopic member dVmax=-99.99 km/s arith.diff
R R system radius kpc phys.size.radius
dMr Dmr absolute value of the r-band absolute magnitude difference between the brightest and the faintest galaxy in the system mag arith.diff
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