ANDROMEDA: AN ANOMALOUS EMITTING GALAXY

English
An international collaboration, led by Sapienza University, has highlighted, in the emission of the Andromeda galaxy, an Anomalous component in the microwave in excess with respect to expectations. This has been possible thanks to the astronomical observations undertaken with the 64 meters radio telescope Sardinia Radio Telescope, a new facility managed by the Istituto Nazionale di Astrofisica. The work is under publication in the scientific journal Astrophysical Journal Letter.
 
The Andromeda galaxy is the largest of the galaxies of the Local Group hosting also our Milky Way. It is a very well studied galaxy at all wavelengths with the exception of the microwave band. Thanks to the observations undertaken with the 64-m Sardinia Radio Telescope (SRT-http://www.srt.inaf.it/), managed by the Istituto Nazionale di Astrofisica (INAF), an international collaboration, led by Sapienza University, and including also the Osservatorio Astronomico di Cagliari-INAF, the Instituto de Astrofisica de Canarias-Spain, the University of British Columbia-Canada, the California Institute of Technology-USA, and the Istituto di Radio Astronomia di Bologna-INAF, has completely mapped the Andromeda galaxy in the microwave band at wavelength of 4,5cm (frequency 6.7GHz), with the aim to study its astrophysical emission and the reasons for such emission. Thanks to the state of the art technology implemented in the SRT, as well as to the excellent sensitivity and stability of the observations, it has been observed that, beyond the classical emission mechanisms originated by the interaction of the interstellar medium with the galaxy magnetic field, Andromeda shows the Anomalous emission in excess with respect to what expected which requires a new emission mechanism. The most accepted models foresee that this emission is due to rapidly rotating very small dust grains of the interstellar medium, emitting through electric dipole emission: Spinning Dust.
 
In 2015, the Planck satellite saw a hint of such an emission with low significance. However, now it is certain the such an emission is present in the overall emission of Andromeda. The Anomalous Microwave Emission (AME) has been so far observed mainly within our own Galaxy and there is still discussion about the effective presence, and the amount of it, in other galaxies. Observing Andromeda galaxy in its entire extension is a unique way to study effects so far studied only in out Galaxy from an external point of view.
 
These kind of studies are still currently in progress with shorter wavelengths observations being undertaken with the SRT, and will allow the researchers to study the astrophysics of the Andromeda galaxy, its star formation rate, the magnetic field within the galaxy, and the possibility of laser emission in the microwave band (MASER) due to the presence of molecules of water.

 

The SRT is funded by the Ministry of Universities and Research, the Italian Space Agency, and the Autonomous Region of Sardinia, and it is operated as a National Facility by INAF. This research is supported by the Sapienza Ateneo research projects (progetti medi 2016).
 

Reference:
"Strong evidence of Anomalous Microwave Emission from the flux density spectrum of M31"
E.S. Battistelli (Sapienza), S. Fatigoni (UBC), M. Murgia (OAC-INAF), A. Buzzelli (Sapienza/Tor Vergata), E. Carretti (IRA-INAF), P. Castangia (OAC-INAF), R. Concu (OAC-INAF), A. Cruciani (Sapienza), P. de Bernardis (Sapienza), R. Genova-Santos (IAC), F. Govoni (OAC-INAF), F. Guidi (IAC), L. Lamagna (Sapienza), G. Luzzi (ASI/Sapienza), S. Masi (Sapienza), A. Melis (OAC-INAF), R. Paladini (Caltech), F. Piacentini (Sapienza), S. Poppi (OAC-INAF), F. Radiconi (Sapienza), R. Rebolo (IAC), J.A. Rubino-Martin (IAC), A. Tarchi (OAC-INAF), and V. Vacca (OAC-INAF)

 

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