**Table 7:** Comparison of average values of colour gradients for our full sample and for the *Pec* subsample of morphologically peculiar objects (Michard & Prugniel 2004). Among *Pec* objects we distinguish the YP family with evidence for the presence of some young stars and the NP family with no such evidence.
Y	All	N	$A\rm v$	YP	N	$A\rm v$	NP	N	$A\rm v$
$\Delta _{BV}$	All	53	- $0.066\pm.003$	YP	9	$-0.060\pm.005$	NP	7	$-0.057\pm.006$
$\Delta _{UB}$	id	41	- $0.157\pm.007$	id	7	$-0.137\pm.006$	id	6	$-0.138\pm.010$
$\Delta_{BR}$	id	43	- $0.082\pm.004$	id	8	$-0.074\pm.005$	id	6	$-0.074\pm.011$
$\Delta_{VI}$	id	47	- $0.061\pm.005$	id	7	$-0.052\pm.006$	id	7	$-0.053\pm.008$
$\Delta _{VJ}$	id	53	- $0.136\pm.013$	id	9	$-0.108\pm.029$	id	7	$-0.123\pm.021$
$\Delta _{VK}$	id	53	- $0.227\pm.015$	id	9	$-0.169\pm.029$	id	7	$-0.201\pm.024$
$\Delta_{JK}$	id	54	- $0.093\pm.004$	id	9	$-0.073\pm.009$	id	7	$-0.083\pm.009$

(1) Gradient Y; (2) sample; (3) number of objects N; (4) average with estimated error; (5) sample; (6) number of objects N; (7) average with estimated error; (8) sample; (9) number of objects N; (10) average with estimated error.

Source LaTeX | All tables | In the text

	1 Introduction
	2 Collecting the gradients
	3 Properties of colour gradients
	4 Simulated datasets of colour gradients
	5 Concluding summary
	References