QUIJOTE Scientific Results – XVII. Studying the anomalous microwave emission in the Andromeda Galaxy with QUIJOTE-MFI

M. Fernández-Torreiro*, R. T. Génova-Santos*, J. A. Rubin͂o-Martín, C. H. López-Caraballo, M. W. Peel, C. Arce-Tord, R. Rebolo, E. Artal, M. Ashdown, R. B. Barreiro, F. J. Casas, E. de la Hoz, F. Guidi, D. Herranz, R. Hoyland, A. Lasenby, E. Martínez-Gonzalez, L. Piccirillo, F. Poidevin, B. Ruiz-GranadosD. Tramonte, F. Vansyngel, P. Vielva, R. A. Watson

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


The Andromeda Galaxy (M31) is the Local Group galaxy that is most similar to the Milky Way (MW). The similarities between the two galaxies make M31 useful for studying integrated properties common to spiral galaxies. We use the data from the recent QUIJOTE-MFI Wide Survey, together with new raster observations focused on M31, to study its integrated emission. The addition of raster data improves the sensitivity of QUIJOTE-MFI maps by almost a factor 3. Our main interest is to confirm if anomalous microwave emission (AME) is present in M31, as previous studies have suggested. To do so, we built the integrated spectral energy distribution of M31 between 0.408 and 3000 GHz. We then performed a component separation analysis taking into account synchrotron, free–free, AME, and thermal dust components. AME in M31 is modelled as a log-normal distribution with maximum amplitude, AAME, equal to 1.03 ± 0.32 Jy. It peaks at νAME = 17.2 ± 3.2 GHz with a width of WAME = 0.58 ± 0.16. Both the Akaike and Bayesian information criteria find the model without AME to be less than 1 per cent as probable as the one taking AME into consideration. We find that the AME emissivity per 100 μm intensity in M31 is εAME28.4 GHz = 9.6 ± 3.1 μK MJy−1 sr, similar to that of the MW. We also provide the first upper limits for the AME polarization fraction in an extragalactic object. M31 remains the only galaxy where an AME measurement has been made of its integrated spectrum.

Original languageEnglish
Pages (from-to)11945-11961
Number of pages17
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
Publication statusPublished - Feb 2024


  • ISM: general
  • Local Group
  • diffuse radiation
  • galaxies: ISM
  • radiation mechanisms: general
  • radio continuum: galaxies


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