An extremely compact, low-mass post-starburst galaxy at $z=5.2$

• DOI: 10.48550/arxiv.2303.11349
• Publication Date: 2023-01-01
• Authors: Victoria Strait; Gabriel Brammer; Adam Muzzin; Guillaume Dezprez; Yoshihisi Asada; Roberto Abraham; Maruša Bradač; Kartheik G. Iyer; Nicholas Martis; Lamiya Mowla; Gaël Noirot; Ghassan T. E. Sar...; Marcin Sawicki; Chris J. Willott; Katriona Gould; Tess Grindlay; Jasleen Matharu; Gregor Rihtaršič
• Keywords: Stellar mass; Star (game theory); Low Mass

We report the discovery of a low-mass $z=5.200\pm 0.002$ galaxy that is in process ceasing its star formation. The galaxy, MACS0417-z5PSB, multiply imaged with magnification factors $\sim40$ by cluster MACS J0417.5-1154, observed as part CAnadian NIRISS Unbiased Cluster Survey (CANUCS). Using observations MACS0417-z5PSB JWST/NIRSpec Prism spectrum and NIRCam imaging, we investigate mechanism responsible for cessation formation speculate about possibilities future. spectrophotometric fitting, find remarkably low stellar mass $\rm{M_*}=4.3\pm^{0.9}_{0.8} \times 10^{7} \rm{M_{\odot}}$, less than 1% characteristic at $z\sim5$. measure de-lensed rest-UV half-light radius source plane $30\pm^{7}_{5}$ pc, rate from H$\alpha$ $0.14\pm^{0.17}_{0.12}$ $\rm{M_{\odot}/yr}$. under assumption double power law history, has seen recent rise formation, peaking $\sim10-30$ Myr ago declining precipitously since then. Together, these measurements reveal low-mass, extremely compact which mechanisms have led to considering AGN feedback, environmental processes. can likely rule out an most processes, but leave open possibility could be forming lull bursty history.