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 −1 and an angular resolution of ≈ 1 • . Our intensity data are crucial to confirm the presence of anomalous microwave emission (AME) towards the two molecular complexes W43 (22σ) and W47 (8σ). We also detect at high significance (6σ) AME associated with W44, the first clear detection of this emission towards a SNR. The new QUI-JOTE polarisation data, in combination with WMAP, are essential to: i) Determine the spectral index of the synchrotron emission in W44, β sync = −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 −2 . And iii) set upper limits on the polarisation of W43 of Π AME < 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.

Anomalous microwave emission (AME) has been observed in numerous sky regions, using different experiments in the frequency range ∼ 10 − 60 GHz. One of the most scrutinized regions is G159.6-18.5, located within the Perseus molecular complex. In this paper we present further observations of this region (194 hours in total over ≈ 250 deg 2 ), both in intensity and in polarization. They span four independent frequency channels between 10 and 20 GHz, and were gathered with QUIJOTE, a new CMB experiment with the goal of measuring the polarization of the CMB and Galactic foregrounds. When combined with other publicly-available intensity data, we achieve the most precise spectrum of the AME measured to date in an individual region, with 13 independent data points between 10 and 50 GHz being dominated by this emission. The four QUIJOTE data points provide the first independent confirmation of the downturn of the AME spectrum at low frequencies, initially unveiled by the COSMOSOMAS experiment in this region. We accomplish an accurate fit of these data using models based on electric dipole emission from spinning dust grains, and also fit some of the parameters on which these models depend.We also present polarization maps with an angular resolution of ≈ 1 • and a sensitivity of ≈ 25 µK/beam. From these maps, which are consistent with zero polarization, we obtain upper limits of Π < 6.3% and < 2.8% (95% C.L.) respectively at 12 and 18 GHz, a frequency range where no AME polarization observations have been reported to date. These constraints are compatible with theoretical predictions of the polarization fraction from electric dipole emission originating from spinning dust grains. At the same time, they rule out several models based on magnetic dipole emission from dust grains ordered in a single magnetic domain, which typically predict higher polarization levels. Future QUIJOTE data in this region may allow more stringent constraints on the polarization level of the AME.

We present QUIJOTE intensity and polarization maps in four frequency bands centred around 11, 13, 17, and 19 GHz, and covering approximately 29 000 deg2, including most of the northern sky region. These maps result from 9000 h of observations taken between May 2013 and June 2018 with the first QUIJOTE multifrequency instrument (MFI), and have angular resolutions of around 1°, and sensitivities in polarization within the range 35–40 µK per 1° beam, being a factor ∼2–4 worse in intensity. We discuss the data processing pipeline employed, and the basic characteristics of the maps in terms of real space statistics and angular power spectra. A number of validation tests have been applied to characterize the accuracy of the calibration and the residual level of systematic effects, finding a conservative overall calibration uncertainty of 5 per cent. We also discuss flux densities for four bright celestial sources (Tau A, Cas A, Cyg A, and 3C274), which are often used as calibrators at microwave frequencies. The polarization signal in our maps is dominated by synchrotron emission. The distribution of spectral index values between the 11 GHz and WMAP 23 GHz map peaks at β = −3.09 with a standard deviation of 0.14. The measured BB/EE ratio at scales of ℓ = 80 is 0.26 ± 0.07 for a Galactic cut |b| &gt; 10°. We find a positive TE correlation for 11 GHz at large angular scales (ℓ ≲ 50), while the EB and TB signals are consistent with zero in the multipole range 30 ≲ ℓ ≲ 150. The maps discussed in this paper are publicly available.