Cosmological Implications of the MAXIMA-1 High-Resolution Cosmic Microwave Background Anisotropy Measurement

Abstract

We discuss the cosmological implications of the new constraints on the power spectrum of the Cosmic Microwave Background Anisotropy derived from a new high resolution analysis of the MAXIMA-I measurement. The power spectrum indicates excess power at ℓ ∼ 860 over the average level of power at 411 ≤ ℓ ≤ 785. This excess is statistically significant on the ∼ 95% confidence level. Its position coincides with that of the third acoustic peak as predicted by generic inflationary models, selected to fit the first acoustic peak as observed in the data. The height of the excess power agrees with the predictions of a family of inflationary models with cosmological parameters that are fixed to fit the CMB data previously provided by BOOMERANG-LDB and MAXIMA-I experiments.Our results, therefore, lend support for inflationary models and more generally for the dominance of adiabatic coherent perturbations in the structure formation of the Universe. At the same time, they seem to disfavor a large variety of the non-standard (but inflation-based) models that have been proposed to improve the quality of fits to the CMB data and consistency with other cosmological observables.Within standard inflationary models, our results combined with the COBE-DMR data give best fit values and 95% confidence limits for the baryon density, Ω b h 2 ≃ 0.033±0.013, and the total density, Ω = 0.9 +0.18 −0.16 . The primordial spectrum slope (n s ) and the optical depth to the last scattering surface (τ c ) are found to be degenerate and to obey the relation n s ≃ (0.99 ± 0.14) + 0.46τ c , for τ c ≤ 0.5 (all 95% c.l.).

MAXIMA: A balloon-borne cosmic microwave background anisotropy experiment

“…The array was housed inside an evacuated cryostat and was cooled by an adiabatic demagnetization refrigerator ͑ADR͒ backed by a closedcycle 3 He sorption refrigerator, a pumped open-cycle liquid 4 He bath, and a pumped open-cycle liquid N 2 bath. These cooling systems are summarized in Table X. A 13 l liquid N 2 tank cooled an outer layer of radiation shielding to 77 K. During the flights, this temperature dropped to ϳ50 K when the liquid N 2 tank was exposed to vacuum.…”

“…Inset into the liquid 4 He tank were the ADR and the liquid 3 He refrigerator. All wiring entering the receiver was heat sunk to the liquid 4 He and liquid N 2 tanks and was made of low thermal conductivity stainless steel leads.…”

“…We designed and constructed a large capacity 3 He sorption refrigerator for the MAXIMA cryostat. The closed-cycle refrigerator consisted of 42 STP liters of 3 He of 99.995% purity, an activated charcoal sorption pump, a copper condenser, and a copper evaporator which was hermetically coupled to the condenser with a thin walled stainless steel bellows.…”

“…The thermal conductivity of tin was known to decrease rapidly with temperature. By design, the tin wire was a poor thermal link for temperatures above 10 K. The refrigerator was cycled by first heating the charcoal to 40 K for ϳ30 min, which desorbed the 3 He from the pump. After heating, the charcoal and tin slowly cooled back to the 4 He cold plate temperature.…”

“…Meanwhile, the desorbed atoms condensed into liquid and pooled into the evaporator. Once the charcoal had cooled below 10 K, it pumped on the 3 He, which cooled the liquid to ϳ300 mK. The refrigerator maintained this base temperature for 36-48 h with an unpumped 4 He bath and had a cooling capacity of 25 J.…”