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Upper Limits to Magnetic Fields in the Outskirts of Galaxies

Observatorio Astronómico de Quito, Escuela Politécnica Nacional, Av. Gran Colombia S/N, Quito 170403, Ecuador
Author to whom correspondence should be addressed.
Academic Editor: Tomotsugu Goto
Galaxies 2017, 5(3), 55;
Received: 31 July 2017 / Revised: 12 September 2017 / Accepted: 18 September 2017 / Published: 19 September 2017
(This article belongs to the Special Issue On the Origin (and Evolution) of Baryonic Galaxy Halos)
PDF [328 KB, uploaded 21 September 2017]


Based on CO(2-1) public data, we study the monoxide oxygen gas excitation conditions and the magnetic field strength of four spiral galaxies. For the galaxy outskirts, we found kinetic temperatures in the range of ≲35–38 K, CO column densities ≲ 10 15 10 16 cm - 2 , and H 2 masses ≲ 4 × 10 6 6 × 10 8 M . An H 2 density ≲ 10 3 cm - 3 is suitable to explain the 2 σ upper limits of the CO(2-1) line intensity. We constrain the magnetic field strength for our sample of spiral galaxies and their outskirts by using their masses and H 2 densities to evaluate a simplified magneto-hydrodynamic equation. Our estimations provide values for the magnetic field strength on the order of ≲6–31 μ G. View Full-Text
Keywords: nearby galaxies; magnetic fields; molecules nearby galaxies; magnetic fields; molecules

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López, E.; Armijos-Abendaño, J.; Llerena, M.; Aldás, F. Upper Limits to Magnetic Fields in the Outskirts of Galaxies. Galaxies 2017, 5, 55.

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