Size Growth on Short Timescales of Star-forming Galaxies: Insights from Size Variation with Rest-frame Wavelength with JADES

Abstract We investigate size variation with rest-frame wavelength for star-forming galaxies based on the second James Webb Space Telescope Advanced Deep Extragalactic Survey data release. Star-forming galaxies are typically smaller at longer wavelengths from the UV to the near-IR at z &lt; 3.5, especially for more massive galaxies, indicating the inside-out assembly with in situ star formation if ignoring dust attenuation. The size variation with wavelength shows a strong dependence on stellar mass and shows little or no dependence on redshift, specific star formation rate, and galaxy environment. This suggests that the size growth of star-forming galaxies is a self-regulated process primarily governed by stellar mass. We model size as a function of both mass and redshift simultaneously, obtaining <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">e</mml:mi> </mml:mrow> </mml:msub> <mml:mo>∝</mml:mo> <mml:msubsup> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>*</mml:mo> </mml:mrow> <mml:mrow> <mml:mn>0.23</mml:mn> </mml:mrow> </mml:msubsup> <mml:msup> <mml:mrow> <mml:mo stretchy="false">(</mml:mo> <mml:mn>1</mml:mn> <mml:mo>+</mml:mo> <mml:mi>z</mml:mi> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1.04</mml:mn> </mml:mrow> </mml:msup> </mml:math> at a wavelength of 0.45 μ m, and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">e</mml:mi> </mml:mrow> </mml:msub> <mml:mo>∝</mml:mo> <mml:msubsup> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>*</mml:mo> </mml:mrow> <mml:mrow> <mml:mn>0.20</mml:mn> </mml:mrow> </mml:msubsup> <mml:msup> <mml:mrow> <mml:mo stretchy="false">(</mml:mo> <mml:mn>1</mml:mn> <mml:mo>+</mml:mo> <mml:mi>z</mml:mi> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1.08</mml:mn> </mml:mrow> </mml:msup> </mml:math> at 1.0 μ m. Based on this size evolution and the star formation main sequence from the literature, we obtain the locus of typical size growth for individual galaxies of different masses on the mass–size plane. The moving trend of galaxies on the mass–size plane, which indicates the slopes of their locus, strongly correlates with the size ratio between 0.45 μ m and 1.0 μ m, supporting the idea that the size variation with wavelength provides important information on the size growth of galaxies on short timescales.