# REMOVABLE MATTER-POWER-SPECTRUM COVARIANCE FROM BIAS FLUCTUATIONS

## Abstract

We find a simple, accurate model for the covariance matrix of the real-space cosmological matter power spectrum on slightly nonlinear scales (k {approx} 0.1-0.8 h Mpc{sup -1} at z = 0), where off-diagonal matrix elements become substantial. The model includes a multiplicative, scale-independent modulation of the power spectrum. It has only one parameter, the variance (among realizations) of the variance of the nonlinear density field in cells, with little dependence on the cell size between 2 and 8 h{sup -1} Mpc. Furthermore, we find that this extra covariance can be modeled out by instead measuring the power spectrum of {delta}/{sigma}{sub cell}, i.e., the ratio of the overdensity to its dispersion in grid cells. Dividing {delta} by {sigma}{sub cell} essentially removes the non-Gaussian part of the covariance matrix, nearly diagonalizing it.

- Authors:

- Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States)

- Publication Date:

- OSTI Identifier:
- 21578362

- Resource Type:
- Journal Article

- Journal Name:
- Astrophysical Journal

- Additional Journal Information:
- Journal Volume: 736; Journal Issue: 1; Other Information: DOI: 10.1088/0004-637X/736/1/8; Journal ID: ISSN 0004-637X

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COSMOLOGY; FLUCTUATIONS; MATRIX ELEMENTS; MATTER; MODULATION; SPECTRA; VARIATIONS

### Citation Formats

```
Neyrinck, Mark C.
```*REMOVABLE MATTER-POWER-SPECTRUM COVARIANCE FROM BIAS FLUCTUATIONS*. United States: N. p., 2011.
Web. doi:10.1088/0004-637X/736/1/8.

```
Neyrinck, Mark C.
```*REMOVABLE MATTER-POWER-SPECTRUM COVARIANCE FROM BIAS FLUCTUATIONS*. United States. doi:10.1088/0004-637X/736/1/8.

```
Neyrinck, Mark C. Wed .
"REMOVABLE MATTER-POWER-SPECTRUM COVARIANCE FROM BIAS FLUCTUATIONS". United States. doi:10.1088/0004-637X/736/1/8.
```

```
@article{osti_21578362,
```

title = {REMOVABLE MATTER-POWER-SPECTRUM COVARIANCE FROM BIAS FLUCTUATIONS},

author = {Neyrinck, Mark C.},

abstractNote = {We find a simple, accurate model for the covariance matrix of the real-space cosmological matter power spectrum on slightly nonlinear scales (k {approx} 0.1-0.8 h Mpc{sup -1} at z = 0), where off-diagonal matrix elements become substantial. The model includes a multiplicative, scale-independent modulation of the power spectrum. It has only one parameter, the variance (among realizations) of the variance of the nonlinear density field in cells, with little dependence on the cell size between 2 and 8 h{sup -1} Mpc. Furthermore, we find that this extra covariance can be modeled out by instead measuring the power spectrum of {delta}/{sigma}{sub cell}, i.e., the ratio of the overdensity to its dispersion in grid cells. Dividing {delta} by {sigma}{sub cell} essentially removes the non-Gaussian part of the covariance matrix, nearly diagonalizing it.},

doi = {10.1088/0004-637X/736/1/8},

journal = {Astrophysical Journal},

issn = {0004-637X},

number = 1,

volume = 736,

place = {United States},

year = {2011},

month = {7}

}