Speaker
Description
Cosmic microwave background (CMB) photons crossing galaxy clusters
can be scattered by hot electrons in the ionized intracluster medium
(ICM). This results in a small change of the spectrum of the CMB in
the direction of clusters of galaxies. The spectrum of the effect is
characteristic, with a brightness decrease at f < 217 GHz and an
increase at f > 217 GHz, independent of the redshift of the cluster.
This is the thermal Sunyaev-Zeldovich (SZ) effect. Thousands of
clusters have been already detected by means of photometric
measurements of the SZ effect at low frequencies. The motion of the
scatterers produces an additional spectral distortions, with
different shape (kinematic SZ effect).
OLIMPO is a 2.6m aperture mm-wave telescope, working from the
stratosphere at around 150, 250, 350 and 460 GHz to dectect the SZ
effects. At high frequencies, its angular resolution is comparable
to the one of 6-10m aperture ground based telescopes working at low
frequencies. The instrument operates in a pointed mode, so that very
deep observations of specific nearby (z \sim 0.05) clusters can be
obtained, allowing for detailed studies of the density and
temperature distributions of the gas, and of its dynamic state.
The instrument features four arrays of lumped elements kinetic
inductance detectors working at 0.3K, reaching photon-noise limited
performance. For the mainden flight it was launched from the Arctic
airport of Longyearbyen, in 2018. During this technical flight we
succesfully validated for the first time in near space (40 km
altitude) the operation of kinetic inductance detectors arrays, and
the operation of a plug-in differential Fourier Transform
Spectrometer (FTS) for spectral studies within the four wide
observation bands.
In the talk I will review the science goals of OLIMPO, the measured
performance, and the preparation of the payload for the scientific
flight.
