QUIJOTE scientific results - II. Polarisation measurements of the microwave emission in the Galactic molecular complexes W43 and W47 and supernova remnant W44

Abstract

We present Q-U-I JOint TEnerife (QUIJOTE) intensity and polarisation maps at 10-20 GHz covering a region along the Galactic plane 24° ≳ l ≳ 45°, |b| ≳ 8°. These maps result from 210 h of data, have a sensitivity in polarisation of ≈ 40 μK beam and an angular resolution of ≈1°. Our intensity data are crucial to confirm the presence of anomalous microwave emission (AME) towards the two molecular complexesW43 (22σ) and W47 (8σ).We also detect at high significance (6σ) AME associated with W44, the first clear detection of this emission towards a supernova remnant. The new QUIJOTE polarisation data, in combination with Wilkinson Microwave Anisotropy Probe (WMAP), are essential to (i) determine the spectral index of the synchrotron emission in W44, β = -0.62 ± 0.03, in good agreement with the value inferred from the intensity spectrum once a free-free component is included in the fit; (ii) trace the change in the polarisation angle associated with Faraday rotation in the direction of W44 with rotation measure -404 ± 49 rad m and (iii) set upper limits on the polarisation ofW43 of Π < 0.39 per cent (95 per cent C.L.) from QUIJOTE 17 GHz, and < 0.22 per cent from WMAP 41 GHz data, which are the most stringent constraints ever obtained on the polarisation fraction of the AME. For typical physical conditions (grain temperature and magnetic field strengths), and in the case of perfect alignment between the grains and the magnetic field, the models of electric or magnetic dipole emissions predict higher polarisation fractions. ; This work has been partially funded by the Spanish Ministry of Economy and Competitiveness (MINECO) under the projects AYA2007-68058-C03-01, AYA2010-21766- C03-02, AYA2012-39475-C02-01, the Consolider-Ingenio project CSD2010-00064 (EPI: Exploring the Physics of Inflation) and also by the European Union's Horizon 2020 research and innovation programme under grant agreement number 687312. FP thanks the European Commission under the Marie Sklodowska-Curie Actions within the H2020 program, Grant Agreement Number 658499-PolAME-H2020-MSCA-IF-2014. ; Peer Reviewed