Galaxy triplets in Sloan Digital Sky Survey Data Release 7: II. A connection with compact groups?

• Autores: Duplancic Videla, Maria Fernanda; O'mill, Ana Laura; Garcia Lambas, Diego Rodolfo; Sodré Jr., Laerte; Alonso Giraldes, Maria Sol
• Año de publicación: 2013
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: GALAXY; TRIPLETS; COMPACT; GROUPS
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

We analyse a sample of 71 triplets of luminous galaxies derived from the work of O´Mill et al. We compare the properties of triplets and their  members with those of control samples of compact groups, the 10 brightest members of rich clusters and galaxies in pairs. The triplets are restricted to have members with spectroscopic redshifts in the range 0.01<=z<=0.14 and absolute r-band luminosities brighter than Mr=-20.5. For these member galaxies, we analyse the stellar mass content, the star formation rates, the Dn(4000) parameter and (Mg-Mr) colour index. Since galaxies in triplets may finally merge in a single system, we analyse different global properties of these systems. We calculate the probability that the properties of galaxies in triplets are strongly correlated. We also study total star formation activity and global colours, and define the triplet compactness as a measure of the percentage of the system total area that is filled by the light of member galaxies. We concentrate in the comparison of our results with those of compact groups to assess how the triplets are a natural extension of these compact systems. Our analysis suggests that triplet galaxy members behave similarly to  compact group members and galaxies in rich clusters.We also find that systems comprising three blue, star-forming, young stellar population galaxies (blue triplets) are most probably real systems and not a chance configuration of interloping galaxies. The same holds for triplets  composed of three red, non-star-forming galaxies, showing the correlation of galaxy properties in these systems. From the analysis of the triplet as a whole, we conclude that, at a given total stellar mass content, triplets show a total star formation activity and global colours similar to compact groups. However, blue triplets show a high total star formation activity with a lower stellar mass content. From an analysis of the compactness parameter of the systems we find that light is even more concentrated in triplets than in compact groups. We propose that triplets composed of three luminous galaxies, should not be considered as an analogous of galaxy pairs with a third extra member, but rather they are a natural extension of compact groups.
Fil: Duplancic Videla, Maria Fernanda. Consejo Nacional de Investigaciones Cientiâ­ficas y Tecnicas. Centro Cientifico Tecnologico San Juan. Instituto de Ciencias Astronomicas de la Tierra y del Espacio; Argentina
Fil: O'mill, Ana Laura. Universidade Do Sao Paulo. Instituto Astronomia, Geofisica E Ciencias Atmosfericas. Departamento de Astronomia; Brasil
Fil: Garcia Lambas, Diego Rodolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto de Astronomía Teórica y Experimental; Argentina
Fil: Sodré Jr., Laerte. Universidade Do Sao Paulo. Instituto Astronomia, Geofisica E Ciencias Atmosfericas. Departamento de Astronomia; Brasil
Fil: Alonso Giraldes, Maria Sol. Consejo Nacional de Investigaciones Cientiâ­ficas y Tecnicas. Centro Cientifico Tecnologico San Juan. Instituto de Ciencias Astronomicas de la Tierra y del Espacio; Argentina