Top panel: the top curve represents the background corrected Chandra spectrum (uncorrected for the response of the instrument; crosses denote spectral widths and amplitude uncertainties) extracted at the position of Hα filaments (see Fig. 6), and fitted with a two-temperature thermal equilibrium model (solid line). The lower curve represents the background spectrum. Data, represented by crosses, have been binned to give a signal-to-noise ratio >5 in each bin (for plotting purposes only). Bottom panel: the data-to-model ratio (the green solid line representing a ratio of unity), showing the residuals at about 1 keV, 1.4 keV, 1.8 keV, 2.2 keV, and 5 keV.