### Abstract

Large-scale bulk flows in the universe distort the initial density field, broadening the baryon-acoustic-oscillation (BAO) feature that was imprinted when baryons were strongly coupled to photons. Additionally, there is a small shift inward in the peak of the conventional overdensity correlation function, a mass-weighted statistic. This shift occurs when high-density peaks move toward each other. We explore whether this shift can be removed by applying to the density field a transform (such as a logarithm) that gives fairer statistical weight to fluctuations in underdense regions. Using configuration-space perturbation theory in the Zel'dovich approximation, we find that the log-density correlation function shows a much smaller inward shift in the position of the BAO peak at low redshift than is seen in the overdensity correlation function. We also show that if the initial, Lagrangian density of matter parcels could be estimated at their Eulerian positions, giving a displaced-initial-density field, its peak shift would be even smaller. In fact, a transformed field that accentuates underdensities, such as the reciprocal of the density, pushes the peak the other way, outward. In our model, these shifts in the peak position can be attributed to shift terms, involving the derivative of the linear correlation function, that entirely vanish in this displaced-initial-density field.

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

Article number | L14 |

Journal | Astrophysical Journal Letters |

Volume | 763 |

Issue number | 1 |

DOIs | |

Publication status | Published - Jan 20 2013 |

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### Keywords

- cosmology: theory
- large-scale structure of universe

### ASJC Scopus subject areas

- Space and Planetary Science
- Astronomy and Astrophysics

### Cite this

*Astrophysical Journal Letters*,

*763*(1), [L14]. https://doi.org/10.1088/2041-8205/763/1/L14

**Removing baryon-acoustic-oscillation peak shifts with local density transforms.** / McCullagh, Nuala; Neyrinck, Mark C.; Szapudi, I.; Szalay, Alexander S.

Research output: Contribution to journal › Article

*Astrophysical Journal Letters*, vol. 763, no. 1, L14. https://doi.org/10.1088/2041-8205/763/1/L14

}

TY - JOUR

T1 - Removing baryon-acoustic-oscillation peak shifts with local density transforms

AU - McCullagh, Nuala

AU - Neyrinck, Mark C.

AU - Szapudi, I.

AU - Szalay, Alexander S.

PY - 2013/1/20

Y1 - 2013/1/20

N2 - Large-scale bulk flows in the universe distort the initial density field, broadening the baryon-acoustic-oscillation (BAO) feature that was imprinted when baryons were strongly coupled to photons. Additionally, there is a small shift inward in the peak of the conventional overdensity correlation function, a mass-weighted statistic. This shift occurs when high-density peaks move toward each other. We explore whether this shift can be removed by applying to the density field a transform (such as a logarithm) that gives fairer statistical weight to fluctuations in underdense regions. Using configuration-space perturbation theory in the Zel'dovich approximation, we find that the log-density correlation function shows a much smaller inward shift in the position of the BAO peak at low redshift than is seen in the overdensity correlation function. We also show that if the initial, Lagrangian density of matter parcels could be estimated at their Eulerian positions, giving a displaced-initial-density field, its peak shift would be even smaller. In fact, a transformed field that accentuates underdensities, such as the reciprocal of the density, pushes the peak the other way, outward. In our model, these shifts in the peak position can be attributed to shift terms, involving the derivative of the linear correlation function, that entirely vanish in this displaced-initial-density field.

AB - Large-scale bulk flows in the universe distort the initial density field, broadening the baryon-acoustic-oscillation (BAO) feature that was imprinted when baryons were strongly coupled to photons. Additionally, there is a small shift inward in the peak of the conventional overdensity correlation function, a mass-weighted statistic. This shift occurs when high-density peaks move toward each other. We explore whether this shift can be removed by applying to the density field a transform (such as a logarithm) that gives fairer statistical weight to fluctuations in underdense regions. Using configuration-space perturbation theory in the Zel'dovich approximation, we find that the log-density correlation function shows a much smaller inward shift in the position of the BAO peak at low redshift than is seen in the overdensity correlation function. We also show that if the initial, Lagrangian density of matter parcels could be estimated at their Eulerian positions, giving a displaced-initial-density field, its peak shift would be even smaller. In fact, a transformed field that accentuates underdensities, such as the reciprocal of the density, pushes the peak the other way, outward. In our model, these shifts in the peak position can be attributed to shift terms, involving the derivative of the linear correlation function, that entirely vanish in this displaced-initial-density field.

KW - cosmology: theory

KW - large-scale structure of universe

UR - http://www.scopus.com/inward/record.url?scp=84872302874&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84872302874&partnerID=8YFLogxK

U2 - 10.1088/2041-8205/763/1/L14

DO - 10.1088/2041-8205/763/1/L14

M3 - Article

AN - SCOPUS:84872302874

VL - 763

JO - Astrophysical Journal Letters

JF - Astrophysical Journal Letters

SN - 2041-8205

IS - 1

M1 - L14

ER -