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arXiv · 1009.5921

The VIMOS VLT Deep Survey: the contribution of minor mergers to the growth of L_B >= L*_B galaxies since z ~ 1 from spectroscopically identified pairs

C. López-Sanjuan·O. Le Fèvre·L. de Ravel·O. Cucciati·O. Ilbert·L. Tresse·S. Bardelli·M. Bolzonella·T. Contini·B. Garilli·L. Guzzo·D. Maccagni·H. J. McCraken·Y. Mellier·A. Pollo·D. Vergani·E. Zucca
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Abstract

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 <= r_p^max and a relative velocity Delta v <= 500 km s^-1 in redshift space. We vary r_p^max from 30h^-1 kpc to 100h^-1 kpc. We study f_m in two redshift intervals and for several values of mu, the B-band luminosity ratio of the galaxies in the pair, from 1/2 to 1/10. We take mu >= 1/4 and 1/10 <= mu < 1/4 as major and minor mergers. The merger fraction increases with z and its dependence on mu is described well as f_m (>= mu) proportional to mu^s. The value of s evolves from s = -0.60 +- 0.08 at z = 0.8 to s = -1.02 +- 0.13 at z = 0.5. The fraction of minor mergers for bright galaxies evolves with redshift as a power-law (1+z)^m with index m = -0.4 +- 0.7 for the merger fraction and m = -0.5 +- 0.7 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 than for blue galaxies, with red galaxies subject to 0.5 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. Our results also suggest that, for blue galaxies, minor mergers likely lead to early-type spirals rather than elliptical galaxies. These results show that minor merging is a significant but not dominant mechanism driving the mass growth of galaxies in the last ~8 Gyr (Abriged).

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C. López-Sanjuan, O. Le Fèvre, L. de Ravel, O. Cucciati, O. Ilbert, L. Tresse, S. Bardelli, M. Bolzonella, T. Contini, B. Garilli, L. Guzzo, D. Maccagni, H. J. McCraken, Y. Mellier, A. Pollo, D. Vergani, E. Zucca. 2011-02-22. The VIMOS VLT Deep Survey: the contribution of minor mergers to the growth of L_B >= L*_B galaxies since z ~ 1 from spectroscopically identified pairs. https://doi.org/10.1051/0004-6361%2F201015839

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