### Abstract

We investigate the clustering effect of dark energy (DE) in the formation of galaxy clusters using the spherical collapse model. Assuming a fully clustered DE component, the spherical overdense region is treated as an isolated system which conserves the energy separately for both matter and DE inside the spherical region. Then, by introducing a parameter r to characterize the degree of DE clustering, which is defined by the nonlinear density contrast ratio of matter to DE at turnaround in the recollapsing process, i.e. r≡δ_{de,ta} ^{NL}∕δ_{m,ta} ^{NL}, we are able to uniquely determine the spherical collapsing process and hence obtain the virialized overdensity Δ_{vir} through a proper virialization scheme. Estimation of the virialized overdensities from current observation on galaxy clusters suggests that 0.5<r<0.8 at 1σ level for the clustered DE with w<−0.9. Also, we compare our method to the linear perturbation theory that deals with the growth of DE perturbation at early times. While both results are consistent with each other, our method is practically simple and it shows that the collapse process is rather independent of initial DE perturbation and its evolution at early times.

Original language | English |
---|---|

Pages (from-to) | 12-20 |

Number of pages | 9 |

Journal | Physics of the Dark Universe |

Volume | 19 |

DOIs | |

Publication status | Published - 2018 Mar |

### Fingerprint

### Keywords

- Dark energy models
- Structure formation

### ASJC Scopus subject areas

- Astronomy and Astrophysics
- Space and Planetary Science

### Cite this

*Physics of the Dark Universe*,

*19*, 12-20. https://doi.org/10.1016/j.dark.2017.10.006

**Spherical collapse models with clustered dark energy.** / Chang, Chia Chun; Lee, Wolung; Ng, Kin Wang.

Research output: Contribution to journal › Article

*Physics of the Dark Universe*, vol. 19, pp. 12-20. https://doi.org/10.1016/j.dark.2017.10.006

}

TY - JOUR

T1 - Spherical collapse models with clustered dark energy

AU - Chang, Chia Chun

AU - Lee, Wolung

AU - Ng, Kin Wang

PY - 2018/3

Y1 - 2018/3

N2 - We investigate the clustering effect of dark energy (DE) in the formation of galaxy clusters using the spherical collapse model. Assuming a fully clustered DE component, the spherical overdense region is treated as an isolated system which conserves the energy separately for both matter and DE inside the spherical region. Then, by introducing a parameter r to characterize the degree of DE clustering, which is defined by the nonlinear density contrast ratio of matter to DE at turnaround in the recollapsing process, i.e. r≡δde,ta NL∕δm,ta NL, we are able to uniquely determine the spherical collapsing process and hence obtain the virialized overdensity Δvir through a proper virialization scheme. Estimation of the virialized overdensities from current observation on galaxy clusters suggests that 0.5

AB - We investigate the clustering effect of dark energy (DE) in the formation of galaxy clusters using the spherical collapse model. Assuming a fully clustered DE component, the spherical overdense region is treated as an isolated system which conserves the energy separately for both matter and DE inside the spherical region. Then, by introducing a parameter r to characterize the degree of DE clustering, which is defined by the nonlinear density contrast ratio of matter to DE at turnaround in the recollapsing process, i.e. r≡δde,ta NL∕δm,ta NL, we are able to uniquely determine the spherical collapsing process and hence obtain the virialized overdensity Δvir through a proper virialization scheme. Estimation of the virialized overdensities from current observation on galaxy clusters suggests that 0.5

KW - Dark energy models

KW - Structure formation

UR - http://www.scopus.com/inward/record.url?scp=85034079488&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85034079488&partnerID=8YFLogxK

U2 - 10.1016/j.dark.2017.10.006

DO - 10.1016/j.dark.2017.10.006

M3 - Article

AN - SCOPUS:85034079488

VL - 19

SP - 12

EP - 20

JO - Physics of the Dark Universe

JF - Physics of the Dark Universe

SN - 2212-6864

ER -