THE MINOR ROLE OF GAS-RICH MAJOR MERGERS IN THE RISE OF INTERMEDIATE-MASS EARLY TYPES AT z <= 1
- Instituto de Astrofisica de Canarias, Calle Via Lactea s/n, E-38205 La Laguna, Tenerife (Spain)
- Departamento de Astrofisica y Ciencias de la Atmosfera, Facultad de C.C. Fisicas, Universidad Complutense de Madrid, E-28040 Madrid (Spain)
We study the evolution of galaxy structure since z {approx} 1 to the present. From a Great Observatories Origins Deep Survey South (GOODS-S) multi-band catalog, we define (blue) luminosity- and mass-weighted samples, limited by M{sub B} <= -20 and M{sub *} >= 10{sup 10} M{sub sun}, comprising 1122 and 987 galaxies, respectively. We extract early-type (ET; E/S0/Sa) and late-type (LT; Sb-Irr) subsamples by their position in the concentration-asymmetry plane, in which galaxies exhibit a clear bimodality. We find that the ET fraction, f{sub ET}, rises with cosmic time, with a corresponding decrease in the LT fraction, f{sub LT}, in both luminosity- and mass-selected samples. However, the evolution of the comoving number density is very different: the decrease in the total number density of M{sub B} <= -20 galaxies since z = 1 is due to the decrease in the LT population, which accounts for {approx}75% of the total star formation rate in the range under study, while the increase in the total number density of M{sub *} >= 10{sup 10} M{sub sun} galaxies in the same redshift range is due to the evolution of ETs. This suggests that we need a structural transformation between LT galaxies that form stars actively and ET galaxies in which the stellar mass is located. Comparing the observed evolution with the gas-rich major merger rate in GOODS-S, we infer that only {approx}20% of the new ET galaxies with M{sub *} >= 10{sup 10} M{sub sun} appeared since z {approx} 1 can be explained by this kind of mergers, suggesting that minor mergers and secular processes may be the driving mechanisms of the structural evolution of intermediate-mass (M{sub *} {approx} 4 x 10{sup 10} M{sub sun}) galaxies since z {approx} 1.
- OSTI ID:
- 21394459
- Journal Information:
- Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 710; ISSN ASJOAB; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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