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Planck intermediate results: XXV. The Andromeda galaxy as seen by Planck

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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä

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en

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23

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Astronomy & Astrophysics, Volume 582, issue 1, pp. p. A28

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The Andromeda galaxy (M 31) is one of a few galaxies that has sufficient angular size on the sky to be resolved by the Planck satellite. Planck has detected M 31 in all of its frequency bands, and has mapped out the dust emission with the High Frequency Instrument, clearly resolving multiple spiral arms and sub-features. We examine the morphology of this long-wavelength dust emission as seen by Planck, including a study of its outermost spiral arms, and investigate the dust heating mechanism across M 31. We find that dust dominating the longer wavelength emission (greater than or similar to 0.3 mm) is heated by the diffuse stellar population (as traced by 3.6 mu m emission), with the dust dominating the shorter wavelength emission heated by a mix of the old stellar population and star-forming regions (as traced by 24 mu m emission). We also fit spectral energy distributions for individual 5' pixels and quantify the dust properties across the galaxy, taking into account these different heating mechanisms, finding that there is a linear decrease in temperature with galactocentric distance for dust heated by the old stellar population, as would be expected, with temperatures ranging from around 22 K in the nucleus to 14 K outside of the 10 kpc ring. Finally, we measure the integrated spectrum of the whole galaxy, which we find to be well-fitted with a global dust temperature of (18.2 +/- 1.0) K with a spectral index of 1.62 +/- 0.11 (assuming a single modified blackbody), and a significant amount of free-free emission at intermediate frequencies of 20-60 GHz, which corresponds to a star formation rate of around 0.12 M-circle dot yr(-1). We find a 2.3 sigma detection of the presence of spinning dust emission, with a 30 GHz amplitude of 0.7 +/- 0.3 Jy, which is in line with expectations from our Galaxy.

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VK: BIBCODE: 2015A&A...582A..28P; DOI: 10.1051/0004-6361/201424643; eprintid: arXiv:1407.5452

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Ade, P A R, Aghanim, N, Arnaud, M, Ashdown, M, Aumont, J, Baccigalupi, C, Banday, A J, Barreiro, R B, Bartolo, N, Battaner, E, Battye, R, Benabed, K, Bendo, G J, Benoit-Levy, A, Bernard, J -P, Bersanelli, M, Bielewicz, P, Bonaldi, A, Bonavera, L, Bond, J R, Borrill, J, Bouchet, F R, Burigana, C, Butler, R C, Calabrese, E, Cardoso, J -F, Catalano, A, Chamballu, A, Chary, R -R, Chen, X, Chiang, H C, Christensen, P R, Clements, D L, Colombo, L P L, Combet, C, Couchot, F, Coulais, A, Crill, B P, Curto, A, Cuttaia, F, Danese, L, Davies, R D, Davis, R J, de Bernardis, P, de Rosa, A, de Zotti, G, Delabrouille, J, Dickinson, C, Diego, J M, Lähteenmäki, A & Planck Collaboration 2015, 'Planck intermediate results : XXV. The Andromeda galaxy as seen by Planck', Astronomy & Astrophysics, vol. 582, no. 1, 28, pp. p. A28. https://doi.org/10.1051/0004-6361/201424643

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