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Statistical properties of extragalactic sources in the New Extragalactic WMAP Point Source (NEWPS) catalogue | | J. González-Nuevo
; M. Massardi
; F. Argüeso
; D. Herranz
; L. Toffolatti
; J.L. Sanz
; M. López-Caniego
; G. De Zotti
; | | Date: |
16 Nov 2007 | | Abstract: | We present results on spectral index distributions, number counts, redshift
distribution and other general statistical properties of extragalactic point
sources in the NEWPS5 sample L’opez-Caniego et al. (2007). The flux
calibrations at all the WMAP channels have been reassessed both by comparison
with ground based observations and through estimates of the effective beam
areas. The two methods yield consistent statistical correction factors. A
search of the NED has yielded optical identifications for 89% of sources in the
complete sub-sample of 252 sources with S/N>5 and S>1.1 Jy at 23 GHz; 5 sources
turned out to be Galactic and were removed. The NED also yielded redshifts for
92% of the extragalactic sources at |b|>10deg. Their distribution was compared
with model predictions; the agreement is generally good but a possible
discrepancy is noted. Using the 5 GHz fluxes from the GB6 or PMN surveys, we
find that 76% of the 191 extragalactic sources with S_23GHz>1.3,Jy can be
classified as flat-spectrum sources between 5 and 23 GHz. A spectral steepening
is observed at higher frequencies: only 59% of our sources are still
flat-spectrum sources between 23 and 61 GHz and the average spectral indexes
steepen from <alpha_5^23>= 0.01pm 0.03 to <alpha_41^61>= 0.37pm 0.03. We
think, however, that the difference may be due to a selection effect. The
source number counts have a close to Euclidean slope and are in good agreement
with the predictions of the cosmological evolution model by De Zotti et al.
(2005). The observed spectral index distributions were exploited to get
model-independent extrapolations of counts to higher frequencies. The risks of
such operations are discussed and reasons of discrepancies with other recent
estimates are clarified. | | Source: | arXiv, 0711.2631 | | Services: | Forum | Review | PDF | Favorites | |
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