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Evidence for major mergers of galaxies at 2 ≲ z < 4 in the VVDS and VUDS surveys

Evidence for major mergers of galaxies at 2 ≲ z < 4 in the VVDS and VUDS surveys

Authors :
L. A. M. Tasca
O. Le Fèvre
C. López-Sanjuan
P.-W. Wang
P. Cassata
B. Garilli
O. Ilbert
V. Le Brun
B. C. Lemaux
D. Maccagni
L. Tresse
S. Bardelli
T. Contini
S. Charlot
O. Cucciati
A. Fontana
M. Giavalisco
J.-P. Kneib
M. Salvato
Y. Taniguchi
D. Vergani
G. Zamorani
E. Zucca
Publication Year :
2014
Publisher :
EDP Sciences, 2014.

Abstract

Context. The mass assembly of galaxies can proceed through different physical processes. Here we report on the spectroscopic identification of close physical pairs of galaxies at redshi fts 2. z&lt; 4 and discuss the impact of major mergers in shaping galaxies at these early cosmological times. Aims. We aim to identify and characterize close physical pairs of galaxies destined to merge and use their properties to infer t he contribution of merging processes to the early mass assembly of galaxies. Methods. We search for galaxy pairs with a transverse separation rp ≤ 25 h −1 kpc and a velocity differencev≤ 500 km s −1 using the VIMOS VLT Deep Survey (VVDS) and early data from the VIMOSUltra Deep Survey (VUDS) that comprise a sample of 1111 galaxies with spectroscopic redshifts measurements at redshifts 1.8≤ z≤ 4 in the COSMOS, ECDFS, and VVDS-02h fields. We analyse their spectra and associated visible and near-infr ared photometry to assess the main properties of merging galaxies that have an average stellar mass M⋆ = 2.3&#215; 10 10 M⊙ at these redshifts. Results. Using the 12 physical pairs found in our sample we obtain a firs t estimate of the merger fraction at these rdshifts, fmerg∼ (15− 20)%. The pair separations indicate that these pairs will merge within 1 Gyr, on average, with each producing a more massive galaxy by the time the cosmic star formation peaks at z∼ 1− 2. From the average mass ratio between galaxies in the pairs, the stellar mass of the resulting galaxy after merging will be∼ 60% larger than the most massive galaxy in the pair before merging. We conclude that major merging of galaxy pairs is on-going at 2. z&lt; 4 and significantly contributing to the major assembly phase of galaxies at this early epoch.

Details

Language :
English
Database :
OpenAIRE
Accession number :
edsair.doi.dedup.....dc3bc33c92124a9321b9d6c57495ab8c