Abstract
Abstract
We revisit the evolution of galaxy morphology in the Cosmic Evolution Survey field over the redshift range 0.2 ≤ z ≤ 1, using a large and complete sample of 33,605 galaxies with a stellar mass of log(M
*/M
⊙) > 9.5 with significantly improved redshifts and comprehensive nonparametric morphological parameters. Our sample has 13,881 (∼41.3%) galaxies with reliable spectroscopic redshifts and more accurate photometric redshifts with a σ
NMAD ∼ 0.005. This paper is the first in a series that investigates merging galaxies and their properties. We identify 3594 major merging galaxies through visual inspection and find 1737 massive galaxy pairs with log(M
*/M
⊙) >10.1. Among the family of nonparametric morphological parameters including C, A, S, Gini, M
20, A
O, and D
O, we find that the outer asymmetry parameter A
O and the second-order momentum parameter M
20 are the best tracers of merging features compared to other combinations. Hence, we propose a criterion for selecting candidates of violently star-forming mergers: M
20 > − 3A
O + 3 at 0.2 < z < 0.6 and M
20 > − 6A
O + 3.7 at 0.6 < z < 1.0. Furthermore, we show that both the visual merger sample and the pair sample exhibit a similar evolution in the merger rate at z < 1, with
R
∼
(
1
+
z
)
1.79
±
0.13
for the visual merger sample and
R
∼
(
1
+
z
)
2.02
±
0.42
for the pair sample. The visual merger sample has a specific star formation rate that is about 0.16 dex higher than that of nonmerger galaxies, whereas no significant star formation excess is observed in the pair sample. This suggests that the effects of mergers on star formation differ at different merger stages.
Funder
MOST ∣ National Natural Science Foundation of China
MOST ∣ MOST∣ National Natural Science Foundation of China (NSFC)
The Science Research Grants from the China Manned Space Project
The Ministry of Science and Technology of China
The CAS Project for Young Scientists in Basic Research
Publisher
American Astronomical Society
Subject
Space and Planetary Science,Astronomy and Astrophysics