Early results from GLASS-JWST. V: the first rest-frame optical size-luminosity relation of galaxies at \(z>7\)

• Published in: arXiv.org
• Main Authors: Yang, Lilan, Morishita, T, Leethochawalit, N, Castellano, M, Calabro, A, Treu, T, Bonchi, A, Fontana, A, Mason, C, Merlin, E, Paris, D, Trenti, M, Roberts-Borsani, G, Bradac, M, Vanzella, E, Vulcani, B, Marchesini, D, Ding, X, Nanayakkara, Themiya, Birrer, Simon, Glazebrook, K, Jones, T, Boyett, K, Santini, P, Strait, Victoria, Wang, Xin
• Format: Paper
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 07.09.2022
• Subjects: Galaxies; James Webb Space Telescope; Luminosity; Space telescopes
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2207.13101

We present the first rest-frame optical size-luminosity relation of galaxies at \(z>7\), using the NIRCam imaging data obtained by the GLASS James Webb Space Telescope Early Release Science (GLASS-JWST-ERS) program, providing the deepest extragalactic data of the ERS campaign. Our sample consist of 19 photometrically selected bright galaxies with \(m_\text{F444W}\leq27.8\) at \(7<z<9\) and \(m_\text{F444W}<28.2\) at \(z\sim9-15\). We measure the size of the galaxies in 5 bands, from the rest-frame optical (\(\sim4800\,{\rm \AA}\)) to the ultra-violet (UV; \(\sim1600\,{\rm \AA}\)) based on the Sérsic model, and analyze the size-luminosity relation as a function of wavelength. Remarkably, the data quality of NIRCam imaging is sufficient to probe the half-light radius \(r_e\) down to \(\sim 100\) pc at \(z>7\). Given the limited sample size and magnitude range, we first fix the slope to that observed for larger samples in rest-frame UV using HST samples. The median size \(r_0\) at the reference luminosity \(M=-21\) decreases slightly from rest-frame optical (\(600\pm80\) pc) to UV (\(450\pm130\) pc). We then re-fit the size-luminosity relation allowing the slope to vary. The slope is consistent with \(\beta\sim0.2\) for all bands except F150W, where we find a marginally steeper slope of \(\beta=0.53\pm0.15\). The steep UV slope is mainly driven by the smallest and faintest galaxies. If confirmed by larger samples, it implies that the UV size-luminosity relation breaks toward the faint end as suggested by lensing studies.