** We thank the referee for the careful reading and thoughtful suggestions.


I've looked over the latest changes. The changes to the uncertainty estimates in the surface photometry and color profiles seem appropriately done, and the observational data is presented clearly.

I appreciate the new Figure 1, with the sample galaxies shown. My only suggestion here is that the authors use a logarithmic stretch that shows detail throughout the galaxies, so that we can see both their inner structure (which will show the galaxy morphology well) and outer structure (showing the light in the outer isophotes). As it looks now, to get the light in the outer isophotes to show, the inner regions are all saturated black, so the galaxies all just look like black blobs.

** We have added inner contours to highlight the structural properties within the outermost apertures (no image stretching scenario yields satisfactory views of both the inner and outer emission).


I certainly understand (and agree) that a detailed analysis of CIGALE systematics isn't warranted here. But the authors statement in their reply that "we find that the output errors for tau are not a strong function of the input flux uncertainties" is pretty eye-opening. If the uncertainty of the inferred model is not a strong function of the input data, I think that statement needs to be somewhere up front in the discussion of the modeling so that the readers can judge for themselves how well the modeling is being constrained by the actual observations. I suspect the errorbars on tau are much larger than is really reflected in Fig 9.

But if I stick to the observed colors rather than the CIGALE modeling, now that the photometric uncertainties have been cleared up, we can just see if the observational data shows the behavior the authors claim -- that we are seeing reversals of the color gradients. And I just don't see that in the sample. If I just look at Figure 5, taking into account the errorbars on the colors, I see the following:

outer gradients staying blue: 3 galaxies (N4220, N5273, N5523) outer gradients going red : 3 galaxies (N4490, N4618, N5608)

and no clear gradients in the others (and I don't know what to say about N4485, its outskirts look a bit redder than the inner regions, but if anything I see a red gradient turning blue in the outskirts...)

And even if I adopt the CIGALE modeling as correct and believe those tau errorbars and do the same inspection of Fig 9, only 5-6 of the galaxies (out of 15) show actual trends to lower taus at large radius.

That does not seem to me to be a sample of galaxies that shows the blue-turning-red gradient reversals that are talked about in the abstract and discussion sections. And the results in Figure 6(top) show such scatter at given radius that, given the heterogeneity of the sample (in overall color as well as inclination) and photometric uncertainties in the outskirts, I don't find the extremely weak shifts in the median values to be very meaningful.

Or put another way, lets say I had a sample where 10 objects that show no gradients and 5 objects that show red gradients. If I median them all up radially, my median will go red in the outskirts when that's not the behavior of the sample as a whole. Or if I had half the sample going blue weakly and half the sample going red strongly, the median would go red even though the sample is split 50/50 in their trends. So a median over a diverse sample can really mislead.

So I'm afraid that while the observational data (and uncertainties) now seem to be well handled (and I appreciate the authors' efforts there), I just don't feel they support the conclusions the authors reach. Certainly *some* of these galaxies show gradient reversals, but many more don't. It's the diversity of their profiles that seems to characterize the sample much more than any systematic behavior. That's what I'd suggest the authors focus on instead; it's more honest to the data, regardless of what inside-out galaxy formation models say.

** The referee raises fair concerns.  In response, we have dialed back our statements about the sample-wide trends for redder/older outer disks, and placed added focus on the heterogeneity of the sample.  Below are examples of modifications that have been made to the text.

Abstract:
However, these trends are quite modest and the variation from galaxy to galaxy is substantial.  Additional data for a larger sample of galaxies are needed to confirm or dismiss these modest sample-wide trends.

Section 4.2:
However, noll09 caution that the degeneracies inherent to the models result in less than well-constrained tau values for fits based on broad-band photometry of nearby galaxies; in such cases tau values can only typically be characterized as "rather high" or "rather low".

Section 5.2:
However, given the typical color uncertainties in the outskirts, this average reddening is modest and is clearly seen for only a few individual galaxies (e.g., NGC4490, NGC4618, NGC4707, NGC5608).  There is a considerable diversity in the galaxy color profiles, with some galaxies exhibiting flat (NGC5055, UGC7301) or even blue trends (NGC5273, NGC5523), and so caution must be taken when analyzing sample-wide averages.

Section 5.3:
Nonetheless, there is a large diversity in the individual profiles, similar to what is seen for the g-r colors; for some galaxies the tau_0 trend is essentially flat, for others it is mildly falling, there are galaxies that show rising-then-falling radial trends, etc.  Thus, it is perhaps more illuminating to note the sample diversity than any average trend that may be unduly influenced by outliers, especially in light of the range of morphologies represented in the sample.  

Summary:
[added] For a subset of the sample 
[added] suggesting for this subset
[removed] these data and this analysis present a coherent picture of star formation within nearby galaxies