Astronomy and Astrophysics – Astrophysics
Scientific paper
Nov 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011hsa6.conf..232l&link_type=abstract
Highlights of Spanish Astrophysics VI, Proceedings of the IX Scientific Meeting of the Spanish Astronomical Society (SEA), held
Astronomy and Astrophysics
Astrophysics
Scientific paper
In this work we measure the merger fraction, f_m, of L_B ≥ L^*_B galaxies in the VVDS-Deep spectroscopic Survey. We define kinematical close pairs as those galaxies with a separation in the sky plane 5h^{-1} kpc < r_p ≤ 100h^{-1} kpc and a relative velocity Δ v ≤ 500 km s^{-1} in redshift space. We study f_m in two redshift intervals and for several values of μ, the B-band luminosity ratio of the galaxies in the pair, from 1/2 to 1/10. We take μ ≥ 1/4 and 1/10 ≤ μ < 1/4 as major and minor mergers. The fraction of minor mergers for bright galaxies evolves with redshift as a power-law (1+z)^m with index m = -0.4 ± 0.6 for the merger fraction and m = -0.8 ± 0.9 for the merger rate. We split our principal galaxies in red and blue by their rest-frame NUV-r colour, finding that i) f_m is higher for red galaxies, ii) f_m^red does not evolve with z, and iii) f_m^blue evolves dramatically. Our results show that the mass of normal L_B ≥ L^*_B galaxies has grown ˜ 25% since z ˜ 1 because of minor and major mergers. The relative contribution of the mass growth by merging is ˜ 25% due to minor mergers and ˜ 75% due to major ones. The relative effect of merging is more important for red galaxies, with those subject to 0.6 minor and 0.7 major mergers since z ˜ 1, which leads to a mass growth of ˜ 40% and a size increase by a factor of 2. These results show that minor merging is a significant but not dominant mechanism driving the mass growth of galaxies in the last ˜ 8 Gyr.
Bardelli Sandro
Bolzonella Micol
Contini Thierry
Cucciati Olga
de Ravel Loic
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