http://arxiv.org/abs/2305.08547
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 a factor greater than 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, $A_{\rm AME}$, equal to $1.06\pm0.30$ Jy. It peaks at $\nu_{\rm AME}=17.28\pm3.08$ GHz with a width of $W_{\rm AME}=0.57\pm0.15$. Both the Akaike and Bayesian Information Criteria find the model without AME to be less than 1 % as probable as the one taking AME into consideration, thus strongly favouring the presence of AME in M31. We find that the AME emissivity in M31 is $\epsilon_{\rm AME}^{\rm 28.4\,GHz}=9.1\pm2.9$ $\mu$K/(MJy/sr), similar to that computed for 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.
M. Fernández-Torreiro, R. Génova-Santos, J. Rubiño-Martín, et. al.
Tue, 16 May 23
40/83
Comments: 16 pages, 10 figures. Submitted to MNRAS. QUIJOTE data maps available at this https URL