QUIJOTE scientific results - X. Spatial variations of anomalous microwave emission along the Galactic plane

Anomalous microwave emission (AME) is an important emission component between 10 and 60 GHz that is not yet fully understood. It seems to be ubiquitous in our Galaxy and is observed at a broad range of angular scales. Here we use the new QUIJOTE-MFI wide survey data at 11, 13, 17, and 19 GHz to constrain the AME in the Galactic plane (|b| < 10°) on degree scales. We built the spectral energy distribution between 0.408 and 3000 GHz for each of the 5309 0.9° pixels in the Galactic plane, and fitted a parametric model by considering five emission components: synchrotron, free–free, AME, thermal dust and CMB anisotropies. We show that not including QUIJOTE-MFI data points leads to the underestimation (up to 50 per cent) of the AME signal in favour of free–free emission. The parameters describing these components are then intercompared, looking for relations that help to understand AME physical processes. We find median values for the AME width, WAME, and for its peak frequency, νAME, respectively of 0.560−0.050+0.059 and 20.7−1.9+2.0 GHz, slightly in tension with current theoretical models. We find spatial variations throughout the Galactic plane for νAME, but only with reduced statistical significance. We report correlations of AME parameters with certain ISM properties, such as that between the AME emissivity (which shows variations with the Galactic longitude) and the interstellar radiation field, and that between the AME peak frequency and dust temperature. Finally, we discuss the implications of our results on the possible molecules responsible for AME.We thank the staff of the Teide Observatory for invaluable assistance in the commissioning and operation of QUIJOTE. The QUIJOTE experiment is being developed by the Instituto de Astrofisica de Canarias (IAC), the Instituto de Fisica de Cantabria (IFCA), and the Universities of Cantabria, Manchester and Cambridge. Partial financial support was provided by the Spanish Ministry of Science and Innovation under the projects AYA2007-68058-C03-01, AYA2007-68058-C03-02, AYA2010-21766-C03-01, AYA2010-21766-C03-02, AYA2014-60438-P, ESP2015-70646-C2-1-R, AYA2017-84185-P, ESP2017-83921-C2-1-R, PID2019-110610RB-C21, PID2020-120514GB-I00, IACA13-3E-2336, IACA15-BE-3707, EQC2018-004918-P, the Severo Ochoa Programs SEV-2015-0548 and CEX2019-000920-S, the Maria de Maeztu Program MDM-2017-0765 and by the Consolider-Ingenio project CSD2010-00064 (EPI: Exploring the Physics of Inflation). We acknowledge support from the ACIISI, Consejeria de Economia, Conocimiento y Empleo del Gobierno de Canarias and the European Regional Development Fund (ERDF) under grant with reference ProID2020010108. This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement number 687312 (RADIOFOREGROUNDS). We thank the anonymous referee whose comments helped to improve this work. We also thank Bruce Draine, Brandon Hensley, and Enrique Fernández Cancio for their useful comments. MFT acknowledges support from the Agencia Estatal de Investigación (AEI) of the Ministerio de Ciencia, Innovación y Universidades (MCIU) and the European Social Fund (ESF) under grant with reference PRE-C-2018-0067. SEH acknowledges support from the STFC Consolidated Grant (ST/P000649/1). FP acknowledges support from the Spanish State Research Agency (AEI) under grant number PID2019-105552RB-C43 and support from the Agencia Canaria de Investigación, Innovación y Sociedad de la Información (ACIISI) under the European FEDER (FONDO EUROPEO DE DESARROLLO REGIONAL) de Canarias 2014-2020 grant No. PROID2021010078. This paper made use of the IAC Supercomputing facility HTCONDOR (http://research.cs.wisc.edu/htcondor/), partly financed by the Ministry of Economy and Competitiveness with FEDER funds, code IACA13-3E-2493. We acknowledge the use of the Legacy Archive for Microwave Background Data Analysis (LAMBDA), part of the High Energy Astrophysics Science Archive Center (HEASARC). HEASARC/LAMBDA is a service of the Astrophysics Science Division at the NASA Goddard Space Flight Center. We acknowledge the use of data provided by the Centre d’Analyse de Données Etendues (CADE), a service of IRAP-UPS/CNRS [http://cade.irap.omp.eu, Paradis et al. (2012)]. This research has made use of the SIMBAD data base, operated at CDS, Strasbourg, France (Wenger et al. 2000). This work has made use of S-band Polarisation All Sky Survey (S-PASS) data. Based on observations obtained with Planck (http://www.esa.int/Planck), an ESA science mission with instruments and contributions directly funded by ESA Member States, NASA, and Canada. Some of the presented results are based on observations obtained with the QUIJOTE experiment (http://research.iac.es/proyecto/quijote). Some of the results in this paper have been derived using the healpy and HEALPIX packages (Górski et al. 2005; Zonca et al. 2019). We have also used SCIPY (Virtanen et al. 2020), EMCEE (Foreman-Mackey et al. 2013), NUMPY (Harris et al. 2020), MATPLOTLIB (Hunter 2007), CORNER (Foreman-Mackey 2016), and ASTROPY (Astropy Collaboration 2013, 2018) PYTHON packages