text:   Galaxies in the Deep CANDELS GOODS Fields at $1 \leq z \leq 7$",5,"['On the @arxiv on Monday, Amy Whitney (Notts PhD student) et al. released a new paper on the evolution of differential galaxy sizes, accepted to ApJ.  A number of things are worth noting in this paper. A thread. (1/n)\n\n<LINK>', 'We develop a new method of distinguishing high-z galaxies from foreground galaxies. Because of the Lyman-break, we are able to remove contamination.  We call this ""2D Lyman-break imaging"" \n\nExample here, 2nd from left is original image, far right, cleaned of foreground.  (2/n) https://t.co/mLS3LRMbzJ', ""Using the Petrosian radius, which is independent of distances and surface brightness dimming we can measure how 'inner' and 'outer' parts of galaxies grow with time.   The 'eta' values are the ratio of the surface brightness at a radius to the surface brightness within a radius. https://t.co/8GSqk37aEt"", 'Taking the difference in the outer and inner radii it is clear that the outer radii are growing at a fast rate than the inner radii at z &lt; 7.   We confirm that this is an actual effect and not a bias by carrying out extensive simulations. (4/n) https://t.co/z4SgezyTok', 'There is more detail in the paper (have a look) but in general this demonstrates that inside-out growth of galaxies is the dominate process for forming galaxies at z=7 down to z=1.   How this happens is another question which we discuss, but minor mergers is one good way. (5/n)']",19,11,1322