# Four-year COBE DMR cosmic microwave background observations: Mapsand basic results

## Abstract

In this Letter we present a summary of the spatial properties of the cosmic microwave background radiation based on the full 4 yr of COBE Differential Microwave Radiometer (DMR) observations, with additional details in a set of companion Letters. The anisotropy is consistent with a scale-invariant power-law model and Gaussian statistics. With full use of the multifrequency 4 yr DMR data, including our estimate of the effects of Galactic emission, we find a power-law spectral index of n = 1.2 +/- 0.3 and a quadrupole normalization Q(rms-PS) = 15.31(-2.8)(+3.8) mu K. For n = 1 the best-fit normalization is Q(rms-PS/n=1) = 18 +/- 1.6 mu K. These values are consistent with both our previous 1 yr and 2 yr results. The results include use of the l = 2 quadrupole term; exclusion of this term gives consistent results, but with larger uncertainties. The final DMR 4 yr sky maps, presented in this Letter, portray an accurate overall visual impression of the anisotropy since the signal-to-noise ratio is similar to 2 per 10 degrees sky map patch. The improved signal-to-noise ratio of the 4 yr maps also allows for improvements in Galactic modeling and limits on non-Gaussian statistics.

- Authors:

- Publication Date:

- Research Org.:
- COLLABORATION - NASA

- OSTI Identifier:
- 894241

- Report Number(s):
- LBNL-61840

Journal ID: ISSN 0004-637X; ASJOAB; TRN: US200701%%276

- DOE Contract Number:
- DE-AC02-05CH11231

- Resource Type:
- Journal Article

- Journal Name:
- Astrophysical Journal

- Additional Journal Information:
- Journal Volume: 464; Related Information: Journal Publication Date: 06/10/1996; Journal ID: ISSN 0004-637X

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ANISOTROPY; QUADRUPOLES; RADIATIONS; RADIOMETERS; RELICT RADIATION; SIGNAL-TO-NOISE RATIO; SIMULATION; SKY; STATISTICS

### Citation Formats

```
Bennett, C.L., Banday, A.J., Gorski, K.M., Hinshaw, G., Jackson,P., Keegstra, P., Kogut, A., Smoot, G.F., Wilkinson, D.T., and Wright, E.L.
```*Four-year COBE DMR cosmic microwave background observations: Mapsand basic results*. United States: N. p., 1996.
Web. doi:10.1086/310075.

```
Bennett, C.L., Banday, A.J., Gorski, K.M., Hinshaw, G., Jackson,P., Keegstra, P., Kogut, A., Smoot, G.F., Wilkinson, D.T., & Wright, E.L.
```*Four-year COBE DMR cosmic microwave background observations: Mapsand basic results*. United States. doi:10.1086/310075.

```
Bennett, C.L., Banday, A.J., Gorski, K.M., Hinshaw, G., Jackson,P., Keegstra, P., Kogut, A., Smoot, G.F., Wilkinson, D.T., and Wright, E.L. Wed .
"Four-year COBE DMR cosmic microwave background observations: Mapsand basic results". United States. doi:10.1086/310075.
```

```
@article{osti_894241,
```

title = {Four-year COBE DMR cosmic microwave background observations: Mapsand basic results},

author = {Bennett, C.L. and Banday, A.J. and Gorski, K.M. and Hinshaw, G. and Jackson,P. and Keegstra, P. and Kogut, A. and Smoot, G.F. and Wilkinson, D.T. and Wright, E.L.},

abstractNote = {In this Letter we present a summary of the spatial properties of the cosmic microwave background radiation based on the full 4 yr of COBE Differential Microwave Radiometer (DMR) observations, with additional details in a set of companion Letters. The anisotropy is consistent with a scale-invariant power-law model and Gaussian statistics. With full use of the multifrequency 4 yr DMR data, including our estimate of the effects of Galactic emission, we find a power-law spectral index of n = 1.2 +/- 0.3 and a quadrupole normalization Q(rms-PS) = 15.31(-2.8)(+3.8) mu K. For n = 1 the best-fit normalization is Q(rms-PS/n=1) = 18 +/- 1.6 mu K. These values are consistent with both our previous 1 yr and 2 yr results. The results include use of the l = 2 quadrupole term; exclusion of this term gives consistent results, but with larger uncertainties. The final DMR 4 yr sky maps, presented in this Letter, portray an accurate overall visual impression of the anisotropy since the signal-to-noise ratio is similar to 2 per 10 degrees sky map patch. The improved signal-to-noise ratio of the 4 yr maps also allows for improvements in Galactic modeling and limits on non-Gaussian statistics.},

doi = {10.1086/310075},

journal = {Astrophysical Journal},

issn = {0004-637X},

number = ,

volume = 464,

place = {United States},

year = {1996},

month = {1}

}