Table 2: Estimates of the uncertainties in the velocity dispersion due to changes in aperture dimensions for the central and most intense Gaussian function fitted to the observed spectrum for a group of selected H II regions in the barred galaxies: NGC 3359, NGC 1530 and NGC 6951. The catalogued radii of the H II regions (Rad. in Col. 3) and the apertures are in pixels in the intensity maps and $\sigma$ in km s^-1. The third value for $\sigma$ is obtained with a circular aperture of radius r. This radius r is the mean value of the radii obtained from the rectangular apertures, assuming their areas are equal to those of circular projected areas.
Region log $L_{\scriptsize\mbox{H$\alpha$ }}$ Rad. $\sigma$ Aperture $\sigma$ Aperture $\sigma$ r

(galaxy) (erg s^-1) (pix) (km s^-1) (pix $\times$ pix) (km s^-1) (pix $\times$ pix) (km s^-1) (pix)

11(N1530) 39.4338 6.0 39.5 $\pm$ 5.0 15 $\times$ 8 38.6 $\pm$ 4.0 7 $\times$ 5 41.5 $\pm$ 4.3 4.8

15(N1530) 39.3467 5.9 40.7 $\pm$ 0.7 7 $\times$ 7 41.0 $\pm$ 0.6 6 $\times$ 4 40.4 $\pm$ 0.6 3.4

35(N1530) 38.8842 3.8 35.3 $\pm$ 5.1 7 $\times$ 8 34.6 $\pm$ 3.3 6 $\times$ 4 38.8 $\pm$ 3.8 3.5

63(N3359) 38.4188 5.9 26.0 $\pm$ 0.9 7 $\times$ 5 25.2 $\pm$ 0.8 4 $\times$ 5 25.4 $\pm$ 0.8 3.3

51(N3359) 38.5170 5.1 27.1 $\pm$ 0.8 8 $\times$ 6 25.6 $\pm$ 0.8 6 $\times$ 5 26.7 $\pm$ 0.9 3.5

41(N3359) 38.5965 6.1 28.4 $\pm$ 0.5 8 $\times$ 11 28.3 $\pm$ 0.5 7 $\times$ 6 28.7 $\pm$ 0.5 4.5

21(N6951) 38.5823 2.9 31.0 $\pm$ 0.8 7 $\times$ 8 31.1 $\pm$ 0.7 5 $\times$ 5 31.2 $\pm$ 0.6 3.5

28(N6951) 38.4441 2.6 24.8 $\pm$ 0.8 8 $\times$ 6 24.7 $\pm$ 0.7 4 $\times$ 5 24.8 $\pm$ 0.6 3.2

3(N6951) 39.1203 4.4 29.1 $\pm$ 0.5 7 $\times$ 8 28.7 $\pm$ 0.5 6 $\times$ 5 28.9 $\pm$ 0.4 3.6

**Table 2:** Estimates of the uncertainties in the velocity dispersion due to changes in aperture dimensions for the central and most intense Gaussian function fitted to the observed spectrum for a group of selected H II regions in the barred galaxies: NGC 3359, NGC 1530 and NGC 6951. The catalogued radii of the H II regions (Rad. in Col. 3) and the apertures are in pixels in the intensity maps and $\sigma$ in km s^-1. The third value for $\sigma$ is obtained with a circular aperture of radius r. This radius r is the mean value of the radii obtained from the rectangular apertures, assuming their areas are equal to those of circular projected areas.
Region	log $L_{\scriptsize\mbox{H$\alpha$ }}$	Rad.	$\sigma$	Aperture	$\sigma$	Aperture	$\sigma$	r
(galaxy)	(erg s^-1)	(pix)	(km s^-1)	(pix $\times$ pix)	(km s^-1)	(pix $\times$ pix)	(km s^-1)	(pix)
11(N1530)	39.4338	6.0	39.5 $\pm$ 5.0	15 $\times$ 8	38.6 $\pm$ 4.0	7 $\times$ 5	41.5 $\pm$ 4.3	4.8
15(N1530)	39.3467	5.9	40.7 $\pm$ 0.7	7 $\times$ 7	41.0 $\pm$ 0.6	6 $\times$ 4	40.4 $\pm$ 0.6	3.4
35(N1530)	38.8842	3.8	35.3 $\pm$ 5.1	7 $\times$ 8	34.6 $\pm$ 3.3	6 $\times$ 4	38.8 $\pm$ 3.8	3.5
63(N3359)	38.4188	5.9	26.0 $\pm$ 0.9	7 $\times$ 5	25.2 $\pm$ 0.8	4 $\times$ 5	25.4 $\pm$ 0.8	3.3
51(N3359)	38.5170	5.1	27.1 $\pm$ 0.8	8 $\times$ 6	25.6 $\pm$ 0.8	6 $\times$ 5	26.7 $\pm$ 0.9	3.5
41(N3359)	38.5965	6.1	28.4 $\pm$ 0.5	8 $\times$ 11	28.3 $\pm$ 0.5	7 $\times$ 6	28.7 $\pm$ 0.5	4.5
21(N6951)	38.5823	2.9	31.0 $\pm$ 0.8	7 $\times$ 8	31.1 $\pm$ 0.7	5 $\times$ 5	31.2 $\pm$ 0.6	3.5
28(N6951)	38.4441	2.6	24.8 $\pm$ 0.8	8 $\times$ 6	24.7 $\pm$ 0.7	4 $\times$ 5	24.8 $\pm$ 0.6	3.2
3(N6951)	39.1203	4.4	29.1 $\pm$ 0.5	7 $\times$ 8	28.7 $\pm$ 0.5	6 $\times$ 5	28.9 $\pm$ 0.4	3.6

Source LaTeX | All tables | In the text

	1 Introduction
	2 The observations
	3 Relating the photometric and spectroscopic data sets
	4 Extraction of the line profiles
	5 Spectral analysis
	6 The luminosity v. non-thermal velocity dispersion relation
	7 The masses of the H II regions in the log L ${_{\scriptsize {\rm H \alpha}}}$ - log ${\sigma _{\rm nt}}$ diagram
	8 Conclusions
	Appendix A: The effects of different H II region size estimate criteria
	References