Growth of galactic bulges by mergers

Eliche‐Moral, M. C.; Balcells, M.; Aguerri, J. A. L.; González-García, A. César

doi:10.1051/0004-6361:20065394

Cited by 104 publications

(126 citation statements)

References 93 publications

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“…One possible mechanism is minor merging. The N-body simulations find that minor mergers increase the Sérsic index of galaxies (Eliche-Moral et al 2006) and that several minor mergers have the same effect as a major one: only the final mass accreted is important (i.e., ten 1/10 mergers are equivalent to one equal-mass merger, Bournaud et al 2007). We find that the minor-to-major merger ratio of blue galaxies increases between z = 0.8 and z = 0.5 from ∼0.5 to ∼2, indicating that minor mergers may play an important role in the growth of the red sequence since z ∼ 0.5.…”

Section: The Role Of Minor Mergers In the Mass Assembly Of Luminous Gmentioning

confidence: 99%

The VIMOS VLT Deep Survey

López-Sanjuan

Fèvre

Ravel

et al. 2011

A&A

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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 > ∼ L * B galaxies in the VVDS-Deep spectroscopic survey, and study its dependence on the B-band luminosity ratio the pair galaxies, μ ≡ L B,2 /L B,1 , focusing on minor mergers with 1/10 ≤ μ < 1/4, and on the rest-frame NUV − r colour of the principal galaxies. Methods. We use spectroscopic pairs with redshift z < ∼ 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 max p and a relative velocity Δv ≤ 500 km s −1 in redshift space. We vary r max p from 30 h −1 kpc to 100 h −1 kpc. We study f m in two redshift intervals and for several values of μ, from 1/2 to 1/10. We take μ ≥ 1/4 and 1/10 ≤ μ < 1/4 as major and minor mergers. Results. The merger fraction increases with z and its dependence on μ is well described by a power-law function, f m (≥μ) ∝ μ 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 μ, 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 > ∼ L * B galaxies has grown by about 25% since z ∼ 1 because of the combined effects 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 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 ∼ 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 contributing to the mass growth of galaxies in the last ∼8 Gyr.

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Section: The Role Of Minor Mergers In the Mass Assembly Of Luminous Gmentioning

confidence: 99%

The VIMOS VLT Deep Survey

López-Sanjuan

Fèvre

Ravel

et al. 2011

A&A

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“…Nevertheless, several minor mergers can also produce galaxies with photometrical and dynamical properties typical of early-type galaxies. In particular, repeated minor mergers can form spheroidal galaxy components with Sersic shape parameter n from 1 to 4 Eliche-Moral et al 2006;Bournaud et al 2007) or produce galaxies with ratios of the mean velocity to mean velocity dispersion (V/σ) similar to those of early-type galaxies (Bournaud et al 2007). Minor mergers with large gas fractions can also activate central starbursts and lead to the rejuvenation of the central regions of galaxies (Bournaud et al 2007;Kaviraj et al 2009).…”

Section: Eask3: Wet Minor Mergers?mentioning

confidence: 99%

Dissecting the morphological and spectroscopic properties of galaxies in the local Universe

Aguerri

Huertas-Company

Alméida

et al. 2012

A&A

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Aims. We revisit the scaling relations and star-forming histories of local elliptical galaxies using a novel selection method applied to the Sloan Digital Sky Survey DR7. Methods. We combine two probability-based automated spectroscopic and morphological classifications of ∼600 000 galaxies with z < 0.25 to isolate true elliptical galaxies. Our sample selection method does not introduce artificial cuts into the parameters describing the galaxy but instead associates every object with a weight measuring the probability of being in a given spectro-morphological class. Thus, the sample minimizes the selection biases. Results. We show that morphologically defined ellipticals are basically distributed into three spectral classes, which dominate at different stellar masses. The bulk of the population (∼50%) is formed by a well-defined class of galaxies with old stellar populations that formed their stars at very early epochs in a short episode of star formation. They dominate the scaling relations of elliptical galaxies known from previous works and represent the canonical elliptical class. At the low mass end, we find a population of ellipticals with relatively large shapes and smaller velocity dispersions at fixed stellar mass, which seem to have experienced a more recent episode of star formation probably triggered by gas-rich minor mergers. The high mass end tends to be dominated by a third spectral class that is slightly more metal rich and hosts more efficient stellar formation than the reference class. This third class contributes to the curvature in the mass-size relation at high masses reported in previous works. Our method is therefore able to isolate the typical spectra of elliptical galaxies following different evolutionary pathways.

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“…Nowadays, these differences are explained in terms of the different evolution of the high density and the field galaxy populations. Hence, all previous observational results could be explained in terms of several large-and small-scale mechanisms present in high density environments and not in the field, among which we can mention galaxy harassment (Moore et al 1996), ram-pressure stripping (Gunn & Gott 1972;Quilis et al 2000), tidal stripping (Merritt 1983(Merritt , 1984, major and minor galaxy mergers (Aguerri et al 2001;Eliche-Moral et al 2006), and starvation (Larson et al 1980). Within this framework of galaxy evolution, where the environemnt plays an important role, substructure should be taken into account in seeking a global picture of the evolution of galaxies.…”

Section: Introductionmentioning

confidence: 97%

A study of catalogued nearby galaxy clusters in the SDSS-DR4

Aguerri¹,

Sánchéz-Janssen

2010

A&A

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Context. According to the current cosmological paradigm, large scale structures form hierarchically in the Universe. Clusters of galaxies grow through a continuous accretion of mass, and the presence of cluster substructures can be interpreted as signature of this process. Nevertheless, the rate and manner of mass accretion events are still matters of debate. Aims. We have analysed the presence of substructures in one of the largest sample of nearby cluster galaxies available in the literature. We have determined the fraction of clusters with substructure and the properties of the galaxies located in such substructures. Methods. Substructure in the galaxy clusters was studied using the Dressler-Shectman test, which was calibrated through extensive Monte Carlo simulations of galaxy clusters similar to real ones. In order to avoid possible biases in the results due to differing incompleteness among clusters, we selected two galaxy populations: a) galaxies brighter than M r = −20 located in clusters at z < 0.1 (EC1); and b) galaxies of brightness M r < −19 located at z < 0.07 (EC2). Results. In the inner cluster regions (r < r 200 ) 11% and 33% of the clusters of EC1 and EC2 respectively show substructure. This fraction is larger in the outer cluster regions (≈55%) for EC1 and EC2 samples. Cluster global properties, such as σ c , f b or Δm 12 do not depend on the amount of cluster substructure. We have studied the properties of individual galaxies located in substructures in the EC1 and EC2 galaxy populations. The fraction of galaxies within substructures is larger in the outer cluster regions when fainter galaxies are included. The distribution of relative velocities of galaxies within substructures suggest that they consist of an infalling population mixed with backsplash galaxies. We can not rule out that the infalling galaxy population located in substructures are genuine field ones.

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Growth of galactic bulges by mergers

Cited by 104 publications

References 93 publications

The VIMOS VLT Deep Survey

The VIMOS VLT Deep Survey

Dissecting the morphological and spectroscopic properties of galaxies in the local Universe

A study of catalogued nearby galaxy clusters in the SDSS-DR4

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