Star Formation at the Epoch of Reionization with CANUCS: The Ages of Stellar Populations in MACS1149-JD1
Maruša Bradač, Victoria Strait, Lamiya Mowla, Kartheik G. Iyer, Gaël Noirot, Chris J. Willott, Gabriel Brammer, Roberto Abraham, Yoshihisa Asada, G. Desprez, Vicente Estrada-Carpenter, Anishya Harshan, Nicholas S. Martis, Jasleen Matharu, Adam Muzzin, Gregor Rihtaršič, Ghassan T. E. Sarrouh, Marcin Sawicki
Abstract
Abstract We present measurements of stellar populations properties of a z = 9.1 gravitationally lensed galaxy MACS1149-JD1 using deep James Webb Space Telescope NIRISS slitless spectroscopy as well as NIRISS and NIRCam imaging from the CAnadian NIRISS Unbiased Cluster Survey (CANUCS). The galaxy is split into four components. Three magnified ( μ ∼ 11) star-forming components are unresolved, giving intrinsic sizes of <25 pc. In addition, the underlying extended component contains the bulk of the stellar mass, formed the majority of its stars ∼50 Myr earlier than the other three components, and is not the site of the most active star formation currently. The NIRISS and NIRCam resolved photometry does not confirm a strong Balmer break previously seen in Spitzer. The NIRISS grism spectrum has been extracted for the entire galaxy and shows a clear continuum and Lyman break, with no Ly α detected.