Erratum for: A&A 583, A101 (2015), DOI: 10.1051/0004-6361/201425540

Several errors were introduced at various stages of the article’s revision. None of them change the scientific content but they can be confusing. They are listed below:

• Section 3.1, second paragraph, page 4: “For weak refraction, Δr is ≪r₁” should read “For weak refraction, Δr = r_min − r₁ is ≪r₁”.

• Section 3.3, first paragraph, page 4: “In practice we excluded from regions” should read “In practice we excluded regions”.

• Section 4.2, first paragraph, page 5: “the saturation effect since it is slightly more marked” should read “the saturation effect being slightly more marked”.

• Section 4.3, third paragraph, page 6: “i) the observed decrease in EW densities derived from 150 and 164 MHz in 2004 is stronger at” should read “i) the observed decrease in the NS densities derived from 150 and 164 MHz in 2004 is stronger than that of the fit”.

• Section 5.2, second paragraph, page 7: “The first values refer to T_e = 1550 kK.” should read “The first values refer to T_e = 620 kK.”

© ESO, 2015