Issue |
Astron. Astrophys. Suppl. Ser.
Volume 130, Number 3, June II 1998
|
|
---|---|---|
Page(s) | 551 - 560 | |
DOI | https://doi.org/10.1051/aas:1998243 | |
Published online | 15 June 1998 |
Beam distortion effects on anisotropy measurements of the cosmic microwave background
1
Istituto TeSRE, Consiglio Nazionale delle Ricerche, Via Gobetti 101, 40129 Bologna, Italy
2
SISSA, International School for Advanced Studies, Via Beirut 2-4, 34014 Trieste, Italy
3
IFCTR, Consiglio Nazionale delle Ricerche, Via Bassini 15, 20133 Milano, Italy
Received:
7
November
1997
Accepted:
18
December
1997
High resolution observations of CMB anisotropy
requires the use of feed arrays at the focus of an optical system.
Beam responses are typically not symmetric
for array elements de-centred from the telescope focus,
whereas theoretical
predictions and standard deconvolution methods generally assume pure
symmetric beams.
For estimating the effect of main beam asymmetry on
temperature fluctuations measurements
we have generated high resolution sky maps
by using standard spherical harmonics expansion for the CMB fluctuations and
by extrapolating available full sky maps to predict Galaxy emission
at frequencies and angular scales appropriate to future space missions,
like Planck and MAP.
We have then convolved simulated maps of the microwave sky
with asymmetric beams
by adopting the Planck configuration and scanning strategy.
We find that
the typical difference between
temperature measurements performed by symmetric and asymmetric beams is of
few and that it is an increasing function of
the beam eccentricity and FWHM.
Although this effect is not very large, it
is of order of the ultimate sensitivity of the next generation of experiments,
and must be reduced by optimizing the feedhorns locations on the focal plane.
Key words: cosmology: cosmic microwave background / diffuse radiation / methods: data analysis / telescopes
© European Southern Observatory (ESO), 1998