Estimated FR of the stellar disk in NGC 551 as a function of radius. The estimation was obtained using different modeled scale heights. The solid red line represents the FR of scale length and HWHM scale height. The dashed blue line represents the FR obtained from the ratio of scale length and exponential scale height. The dashed-dotted green line represents the FR obtained from the ratio of scale length and sech² scale height. The FR varies substantially (between ∼8−23) with radius.