QUIJOTE scientific results – IV. A northern sky survey in intensity and polarization at 10–20 GHz with the multifrequency instrument

Abstract

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| > 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.

QUIJOTE scientific results – IX. Radio sources in the QUIJOTE-MFI wide survey maps

“…For this reason, an annulus around the sources is used, as mentioned at the beginning of this section. The lobes in the U map is an instrumental effect associated with intensity-to-polarization leakage due to the difference between the two co-polar beams, as explained in section 9.3 of Rubiño-Martín et al (2023). These are visible in this case because most of Crab polarized emission is contained in the Q direction in Galactic coordinates.…”

“…In order to check the self-consistency of IFCAPOL, as well as have at hand an additional means of testing the stability of QUIJOTE data and the map-making algorithm (see Gómez-Reñasco et al 2012;Pérez-de-Taoro et al 2016;Rubiño-Martín et al 2023;Génova-Santos et al 2023), we have conducted a series of jackknife tests comparing the estimation of the main photometric and polarimetric quantities (I, P and 𝜙, but also Q and U individually) on two different maps, which have been produced by splitting the MFI wide survey data into two halves. The maps that we use are the so-called 'half-mission maps' and they are constructed by separating the individual observations (6 h each) according to the calendar date in each observing period (there are four in total, spread over 6 yr) and each telescope elevation (usually we have three or four observing elevations in each period).…”

“…The maps that we use are the so-called 'half-mission maps' and they are constructed by separating the individual observations (6 h each) according to the calendar date in each observing period (there are four in total, spread over 6 yr) and each telescope elevation (usually we have three or four observing elevations in each period). A more complete description of these maps is given in Rubiño-Martín et al (2023). By construction, these maps are designed to have almost identical sky signal and sky coverage, but independent noise.…”

“…In total, the MFI provides four frequency bands centred around 11, 13, 17 and 19 GHz, each band being covered by two independent horns. Although wide-survey maps made by horn 1 have been produced for internal consistency tests, they have not been used for this paper because they are significantly affected by systematic effects (see Rubiño-Martín et al 2023, for more details). The approximate angular resolution, given in terms of the full width at half maximum, is 55 arcmin for the low-frequency bands at 11 and 13 GHz, and 40 arcmin for the 17 and 19 GHz channels.…”

“…This was one of the main scientific objectives of QUI-JOTE (Rubiño-Martín et al 2012) and of the MFI instrument in particular, which was in operation between 2012 and 2018. A detailed description of the Wide Survey and its scanning strategy, sky coverage and maps can be found in Rubiño-Martín et al (2023). The QUIJOTE Wide Survey provides a unique view of a large portion of the sky at a frequency range of utmost importance for the characterization of radio foregrounds for CMB science.…”