Search for unresolved sources in the COBE-DMR two-year sky maps

Abstract

We have searched the temperature maps from the COBE Di erential Microwave Radiometers (DMR) rst two years of data for evidence of unresolved sources. The high-latitude sky (jbj > 30 ) contains no sources brighter than 192 K thermodynamic temperature (322 Jy at 53 GHz). The cumulative count of sources brighter than threshold T , N (>T ), is consistent with a superposition of instrument noise plus a scale-invariant spectrum of cosmic temperature uctuations normalized to Q rms PS = 17 K. We examine the temperature maps toward nearby clusters and nd no evidence for any Sunyaev-Zel'dovich e ect, y < 7.3 10 6 (95% CL) averaged over the DMR beam. We examine the temperature maps near the brightest expected radio sources and detect no evidence of signi cant emission. The lack of bright unresolved sources in the DMR maps, taken with anisotropy measurements on smaller angular scales, places a weak constraint on the integral number density of any unresolved Planck-spectrum sources brighter than ux density S, n(>S) < 2 10 4 (S=1 Jy) 2 sr 1 .Subject headings: cosmic microwave background | radio continuum:general 2

Noncosmological Signal Contributions to the [ITAL]COBE[/ITAL] DMR 4 Year Sky Maps

“…Bennett et al (1993) predicted that the LMC, and specifically the giant HII region 30 Doradus, might contribute a signal of order 50 µK at 53 GHz. Kogut et al (1994) determined an upper limit of 87 µK (95% confidence level) from the two year sky maps with a point source fitting technique, in good agreement with this prediction. Using the peak-peak limits from the earlier fits including this region, we place 95% upper limits to the antenna temperature microwave emission of the LMC of 109, 49 and 57 µK at 31.5, 53 and 90 GHz respectively.…”

“…We consider the mean temperatures in the DMR maps towards 5 nearby clusters to search for indications of SZ decrements or radio and dust emission from galaxies within the cluster (which are competing effects at the DMR frequencies, and any limits should be considered in light of this). A "ring" technique, as utilized previously in Bennett et al (1993) and Kogut et al (1994), computes the difference between the mean temperature of pixels within a disk of radius θ and those in the surrounding annulus of equal area. This technique should be sensitive to low surface Comptonization.…”

Four-Year [ITAL]COBE[/ITAL] DMR Cosmic Microwave Background Observations: Maps and Basic Results

“…There is no evidence for an excess of large deviations, as would be expected if there were an unknown population of point sources. A search for point sources in the 2-year maps was negative (Kogut et al 1994). Given the large beam of the instrument and the variance of both cosmic signals and receiver noise, it is still possible for interesting signals to be hidden in the data.…”

Tests for Non-Gaussian Statistics in the DMR Four-Year Sky Maps

“…The number density of peaks or valleys is dominated by the noise properties of the map (Kogut et al 1994). The clustering of the extrema, as measured by the 2point correlation function of the maxima and minima, provides additional information on the underlying CMB temperature field.…”