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The first JWST data revealed an unexpected population of red galaxies thatappear to have redshifts of $z\sim 7-9$ and high masses of $M_*$ $\sim$10$^{10}$ M$_{\odot}$ (Labb\'e et al. 2023). Here we fit S\'ersic profiles tothe F200W NIRCam images of the 13 massive galaxy candidates of Labb\'e et al.,to determine their structural parameters. Satisfactory fits were obtained fornine galaxies. We find that their effective radii are extremely small, rangingfrom $r_{\rm e}\sim 80$ pc to $r_{\rm e} \sim 300$ pc, with a mean of $\langler_{\rm e}\rangle \approx 150$ pc. For their apparent stellar masses, thegalaxies are smaller than any other galaxy population that has been observed atany other redshift. We use the fits to derive circularized three-dimensionalstellar mass profiles of the galaxies, and compare these to the mass profilesof massive quiescent galaxies at $z\sim$2.3 and nearby elliptical galaxies. Wefind that, despite the high redshift galaxies having $10-20$ times smallerhalf-light radii, the central stellar densities are comparable to those oftheir putative descendants at later times. The most straightforwardinterpretation is that the dense compact inner regions of the most massiveellipticals today were already in place $\sim 600$ Myr after the Big Bang. Wecaution that the redshifts and masses of the galaxies remain to be confirmed,and that the complex NIRCam point spread function is not yet fullycharacterized.

Sizes and mass profiles of candidate massive galaxies discovered by JWST  at 7<z<9: evidence for very early formation of the central ~100 pc of  present-day ellipticals