A Constraint on Primordial B-modes from the First Flight of the Spider Balloon-borne Telescope
Résumé
We present the first linear polarization measurements from the 2015 long-duration balloon flight of Spider, which is an experiment that is designed to map the polarization of the cosmic microwave background (CMB) on degree angular scales. The results from these measurements include maps and angular power spectra from observations of 4.8% of the sky at 95 and 150 GHz, along with the results of internal consistency tests on these data. While the polarized CMB anisotropy from primordial density perturbations is the dominant signal in this region of sky, Galactic dust emission is also detected with high significance. Galactic synchrotron emission is found to be negligible in the Spider bands. We employ two independent foreground-removal techniques to explore the sensitivity of the cosmological result to the assumptions made by each. The primary method uses a dust template derived from Planckdata to subtract the Galactic dust signal. A second approach, which constitutes a joint analysis of Spider and Planckdata in the harmonic domain, assumes a modified-blackbody model for the spectral energy distribution of the dust with no constraint on its spatial morphology. Using a likelihood that jointly samples the template amplitude and r parameter space, we derive 95% upper limits on the primordial tensor-to-scalar ratio from Feldman–Cousins and Bayesian constructions, finding r < 0.11 and r < 0.19, respectively. Roughly half the uncertainty in r derives from noise associated with the template subtraction. New data at 280 GHz from Spider’s second flight will complement the Planckpolarization maps, providing powerful measurements of the polarized Galactic dust emission.
Mots clés
cosmic background radiation: polarization
cosmic background radiation: anisotropy
polarization: linear
perturbation: primordial
energy: density: primordial
density: perturbation
power spectrum: angular dependence
SPIDER
galaxy
satellite: Planck
synchrotron radiation
detector: sensitivity
noise
cosmological model
numerical calculations
Monte Carlo: Markov chain
detector: noise
statistical analysis: Bayesian
black body
data analysis method
cosmic background radiation: B-mode