Strong Evidence of Anomalous Microwave Emission from the Flux Density Spectrum of M31
- Creators
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Battistelli, E. S.
- Fatigoni, S.
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Murgia, M.
- Buzzelli, A.
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Carretti, E.
- Castangia, P.
- Concu, R.
- Cruciani, A.
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de Bernardis, P.
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Genova-Santos, R.
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Govoni, F.
- Guidi, F.
- Lamagna, L.
- Luzzi, G.
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Masi, S.
- Melis, A.
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Paladini, R.
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Piacentini, F.
- Poppi, S.
- Radiconi, F.
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Rebolo, R.
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Rubino-Martin, J. A.
- Tarchi, A.
- Vacca, V.
Abstract
We have observed the Andromeda galaxy, Messier 31 (M31), at 6.7 GHz with the Sardinia Radio Telescope. We mapped the radio emission in the C-band, re-analyzed WMAP and Planck maps, as well as other ancillary data, and we have derived an overall integrated flux density spectrum from the radio to the infrared. This allowed us to estimate the emission budget from M31. Integrating over the whole galaxy, we found strong and highly significant evidence for anomalous microwave emission (AME), at the level of 1.45_(-0.19)^(+0.17) Jy at the peaking frequency of ≃ 25 GHz. Decomposing the spectrum into known emission mechanisms such as free–free, synchrotron, thermal dust, and AME arising from electric dipole emission from rapidly rotating dust grains, we found that the overall emission from M31 is dominated, at frequencies below 10 GHz, by synchrotron emission with a spectral index of -1.10_(-0.08)^(+0.10), with subdominant free–free emission. At frequencies ≳ 10 GHz, AME has a similar intensity to that of synchrotron and free–free emission, overtaking them between 20 and 50 GHz, whereas thermal dust emission dominates the emission budget at frequencies above 60 GHz, as expected.
Additional Information
© 2019. The American Astronomical Society. Received 2019 April 10; revised 2019 May 15; accepted 2019 May 16; published 2019 May 31. The SRT is funded by the Ministry of Universities and Research, the Italian Space Agency, and the Autonomous Region of Sardinia (RAS), and is operated as a National Facility by INAF. These observations could not have been made without the continuous support of the SRT observers and technical staff. We acknowledge the financial support of Sapienza Ateneo-2016 funding. We acknowledge the use of the Planck Legacy Archive (http://www.esa.int/Planck) and of the Legacy Archive for Microwave Background Data Analysis (https://lambda.gsfc.nasa.gov/). This research made use of the CATS Database (https://www.sao.ru/cats/). We thank S. Righini for support in preparing the observing proposal and J. Fritz for the calibrated Herschel maps. R.G.S., F.G., and J.A.R.M. acknowledge financial support from the Spanish Ministry of Economy and Competitiveness (project AYA2017-84185-P). A.M. thanks the RAS for financial support in the context of the research project CRP 18 (P.I. of the project: Dr. M. Burgay). We acknowledge the Scientific Editorial Service of the Instituto de Astrofisica de Canarias. We would like to thank the anonymous referee for the useful comments which improved the Letter.Attached Files
Published - Battistelli_2019_ApJL_877_L31.pdf
Accepted Version - 1905.12276
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Additional details
- Eprint ID
- 95971
- Resolver ID
- CaltechAUTHORS:20190531-091630869
- Ministero dell'Istruzione, dell'Università e della Ricerca (MIUR)
- Agenzia Spaziale Italiana (ASI)
- CRP 18
- Autonomous Region of Sardinia
- Istituto Nazionale di Astrofisica (INAF)
- Ateneo-2016
- Sapienza University
- AYA2017-84185-P
- Ministerio de Economía y Competitividad (MINECO)
- Created
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2019-05-31Created from EPrint's datestamp field
- Updated
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2021-11-16Created from EPrint's last_modified field
- Caltech groups
- Infrared Processing and Analysis Center (IPAC)