Morphological Demographics of Galaxies at <i>z</i> ∼ 10–16: Log-normal Size Distribution and Exponential Profiles Consistent with the Disk Formation Scenario

Abstract We homogeneously investigate the morphological properties of 169 galaxies at z ∼ 10–16 with deep JWST NIRCam images employing our established techniques of GALFIT modeling and uncertainty evaluation (systematics+statistics). We obtain effective radii r e ranging 20–500 pc, with a distribution significantly broader than the scatter made by the uncertainties. We find that the r e distribution is well described by a log-normal distribution with a mean of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>r</mml:mi> <mml:mi mathvariant="normal">e</mml:mi> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>13</mml:mn> <mml:msubsup> <mml:mn>3</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>12</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>13</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> pc and a standard deviation of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>σ</mml:mi> <mml:mrow> <mml:mi>ln</mml:mi> <mml:msub> <mml:mi>r</mml:mi> <mml:mi mathvariant="normal">e</mml:mi> </mml:msub> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>0.52</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.08</mml:mn> </mml:math> . The standard deviation is comparable to that of local galaxies, indicating no significant evolution over z ∼ 0–10. We also find that the axis ratio distribution is nearly uniform, statistically similar to that of local spirals. We estimate the virial radius r vir from the stellar masses via the star formation main sequence and stellar-to-halo mass relation, obtaining a stellar-to-halo size ratio <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>r</mml:mi> <mml:mi mathvariant="normal">e</mml:mi> </mml:msub> <mml:mo>/</mml:mo> <mml:msub> <mml:mi>r</mml:mi> <mml:mi>vir</mml:mi> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>0.01</mml:mn> <mml:msubsup> <mml:mn>5</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.005</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.015</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> , which is comparable to those of star-forming galaxies in the local and low- z Universe. Our results of (1) the log-normal r e distribution, (2) the uniform axis ratio distribution, and (3) a mean radial profile consistent with an exponential profile ( n = 1.3 ± 0.6) suggest that galaxies at z ∼ 10–16 generally follow the classical galaxy disk formation scenario with a specific disk angular momentum fraction of j d / m d ∼ 0.5–1. Interestingly, we identify two remarkable outliers GN-z11 ( z spec = 10.60) and GHZ2 ( z spec = 12.34) with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>r</mml:mi> <mml:mi mathvariant="normal">e</mml:mi> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>5</mml:mn> <mml:msubsup> <mml:mn>5</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>5</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> pc and 39 ± 11 pc, respectively, that may not be explained by disk structures but by active galactic nucleus or compact star-forming galaxies merging underway in short periods of time, as reproduced in numerical simulations.