The VIMOS VLT Deep Survey : The contribution of minor mergers to the growth of L-B greater than or similar to L-B* galaxies since z similar to 1 from spectroscopically identified pairs
Articolo
Data di Pubblicazione:
2011
Citazione:
The VIMOS VLT Deep Survey : The contribution of minor mergers to the growth of L-B greater than or similar to L-B* galaxies since z similar to 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. Mccracken, Y. Mellier, A. Pollo, D. Vergani, E. Zucca. - In: ASTRONOMY & ASTROPHYSICS. - ISSN 0004-6361. - 530(2011), pp. A20.1-A20.16. [10.1051/0004-6361/201015839]
Abstract:
Aims. The role of minor galaxy mergers in galaxy evolution, and in particular to mass assembly, remains an open question. In this work we measure the merger fraction, f(m), of L-B greater than or similar to L-B* galaxies in the VVDS-Deep spectroscopic survey, and study its dependence on the B-band luminosity ratio the pair galaxies, mu L-B,L-2/L-B,L-1, focusing on minor mergers with 1/10 <= mu < 1/4, and on the rest-frame NUV - r colour of the principal galaxies.
Methods. We use spectroscopic pairs with redshift z greater than or similar to 1 in the VVDS-Deep survey to define kinematical close pairs as those galaxies with a separation on the sky plane 5 h(-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 30 h(-1) kpc to 100 h(-1) kpc. We study f(m) in two redshift intervals and for several values of mu, from 1/2 to 1/10. We take mu >= 1/4 and 1/10 <= mu < 1/4 as major and minor mergers.
Results. The merger fraction increases with z and its dependence on mu is well described by a power-law function, 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 shows little evolution 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, in contrast with the increase in the major merger fraction (m = 1.3 +/- 0.5) and rate (m = 1.3 +/- 0.6) for the same galaxies. We split our principal galaxies in red and blue, finding that i) f(m) is higher for red galaxies at every mu, ii) f red m does not evolve with z, with s = -0.79 +/- 0.12 at 0.2 < z < 0.95, and iii) f blue m evolves dramatically: the major merger fraction of blue galaxies decreases by a factor of three with cosmic time, while the minor merger fraction of blue galaxies is roughly constant.
Conclusions. Our results show that the mass of normal L-B greater than or similar to L-B* galaxies has grown by about 25% since z similar to 1 because of the combined effects of minor and major mergers. The relative contribution of the mass growth by merging is similar to 25% due to minor mergers and similar to 75% due to major mergers. 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 similar to 1, which leads to a mass growth of similar to 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 contributing to the mass growth of galaxies in the last similar to 8 Gyr.
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
galaxies: evolution; galaxies: formation; galaxies: interactions; galaxies: statistics
Elenco autori:
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. Mccracken, Y. Mellier, A. Pollo, D. Vergani, E. Zucca
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