Radio continuum spectra of galaxies Uli Klein (Univ. Bonn) Ute - PowerPoint PPT Presentation

Radio continuum spectra of galaxies Uli Klein (Univ. Bonn) Ute Lisenfeld (Univ. de Granada) Simon Verley (Univ. de Granada) Bonn, Feb. 2018 1

star-forming galaxies: FIR, free-free radiation star-formation Lyc photons H  , H  , … fast particles supernovae relativistic particles shock waves dynamo/SNe magnetic field synchrotron radiation Bonn, Feb. 2018 2

Radio continuum spectra of star-forming galaxies assumed for decades:      S ( ) S ( ) S ( ) tot ff syn where  0 . 1          S ( ) S ( 0 )    ff ff   0 and     syn         S ( ) S ( 0 )   0  syn syn syn   0 (optically thin case,   300 MHz) Bonn, Feb. 2018 3

408 MHz 2450 MHz 1400 MHz H  FIR 4750 MHz 8550 MHz Bonn, Feb. 2018 4

measurements with Effelsberg 100-m telescope at 24 GHz, 1982 – 1984 5

dwarf galaxies: II Zw 40, II Zw 70, IC 10, NGC 1569, NGC 4449 massive starburst galaxies: M 82, NGC 2146, NGC 3079, NGC 3310 interacting: M 51, NGC 4490, NGC 4631 mergers: NGC 4038, NGC 6052 6

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with data  10.7 GHz 8

with data  10.7 GHz 9

best fit (mostly): −0.1 𝛽 𝑡𝑧𝑜 − 𝜉 𝜉 𝜉 ! 𝜉 𝑐 𝑇 𝑡𝑧𝑜 𝜉 = 𝑇 𝑔𝑔 𝜉 0 ∙ + 𝑇 𝑡𝑧𝑜 𝜉 0 ∙ ∙ 𝑓 𝜉 0 𝜉 0 Bonn, Feb. 2018 10

best fit (mostly): −0.1 𝛽 𝑡𝑧𝑜 − 𝜉 𝜉 𝜉 ! 𝜉 𝑐 𝑇 𝑡𝑧𝑜 𝜉 = 𝑇 𝑔𝑔 𝜉 0 ∙ + 𝑇 𝑡𝑧𝑜 𝜉 0 ∙ ∙ 𝑓 𝜉 0 𝜉 0 Bonn, Feb. 2018 11

fitting synchrotron spectra: power-law, curved, break, cut-off Bonn, Feb. 2018 12

Bonn, Feb. 2018 13

f th (1 GHz) = 15% power-law + ff  nth = -0.5 power-law with cut-off + ff 14

f th (1 GHz) = 15%  nth = -0.5 data: NGC 2146 15

fraction of thermal emission extinction Bonn, Feb. 2018 16

 nth : comparison with SNR (Green, 2014) spectra:  nth of low-frequency galaxy spectra similar to  nth of shell-type SNR <  SNR > = 0.50,   SNR = 0.33 <  Gal > = 0.59,   Gal = 0.20 Bonn, Feb. 2018 17

SN(R) inject particles with power-law high-energy particles age quickly in thin disk migrate to low energy-regime are transported into halo may reside and radiate there for long time … Bonn, Feb. 2018 18

Conclusions: revised radio continuum spectra • reveal broken power-laws of synchrotron spectra • indicate low containment of comic rays in dwarf galaxies • exhibit  low   SNR (must be checked with LOFAR!) • cut-off energies 1.5 - 7 GeV more such work worthwhile: Effelsberg SRT!!! Paper: Klein, Lisenfeld, Verley Greenbank A&A, in press 2017arXiv171003149K Bonn, Feb. 2018 19