Central enhancement of the nitrogen-to-oxygen abundance ratio in barred galaxies

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Table 2

Statistics for barred and unbarred non-AGN and star-forming galaxies.


	Non-AGN					Star-forming


	P-value^a	barred		unbarred		P-value^a	barred		unbarred
		median	N	median	N		median	N	median	N


c(Hβ)	0.8%	0.50±0.04	104	0.44±0.03	140	0.6%	0.53±0.04	43	0.46±0.04	96
log R ₂₃	64.0%	0.31±0.04	105	0.31±0.04	130	0.3%	0.19±0.04	41	0.22±0.04	86
N2	0.0009%	–0.28±0.02	110	–0.38±0.02	152	0.02%	–0.37±0.03	43	–0.43±0.01	96
log Σ_SFR	0.07%	–1.1±0.1	112	–1.3±0.1	155	0.1%	–0.9±0.1	43	–1.2±0.1	96
[S ii]λ6717/[S ii]λ6731	0.05%	1.25±0.03	104	1.31±0.03	127	0.7%	1.28±0.03	40	1.33±0.03	84
log (N/O)	0.01%	–0.49±0.03	105	–0.58±0.03	143	0.03%	–0.49±0.04	40	–0.58±0.03	91
12+log (O/H)	4.3%	8.68±0.01	107	8.69±0.01	151	7.4%	8.69±0.01	40	8.70±0.01	92
log U	5.3%	–3.08±0.02	107	–3.14±0.02	151	2.5%	–3.09±0.03	40	–3.18±0.02	92

Notes. Median values and errors (95% confidence interval of the median) of the distributions of: c(Hβ), R₂₃ and N2 gas-phase metallicity indicators, star formation rate per unit area, [S ii]λ6717/[S ii]λ6731 line ratio, oxygen abundance and N/O ratio, and logarithm of the ionisation parameter. All figures refer to the centres of barred and unbarred galaxies in the sub-samples of non-AGN and pure star-forming galaxies (Sect. 4). N is the number of galaxies in each sub-sample. The P-values of the k-sample A-D test for the comparison of distributions for barred and unbarred galaxies are shown for all cases.

^(a)

A-D test P-value or approximate significance level at which the null hypothesis (the two samples are drawn from the same population) can be rejected. Usually, significance levels lower than 5% are requested to reject the null hypothesis.

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