Spatially-resolved H$\hat{I}\pm$ and ionizing photon production efficiency in the lensed galaxy MACS1149-JD1 at a redshift of 9.11

Abstract

We present MIRI/JWST medium-resolution spectroscopy (MRS) and imaging (MIRIM) of the lensed galaxy MACS1149-JD1 at a redshift of $z$=9.1092$\pm$0.0002 (Universe age about 530 Myr). We detect, for the first time, spatially resolved H$\hat{I}\pm$ emission in a galaxy at a redshift above nine. The structure of the H$\hat{I}\pm$ emitting gas consists of two clumps, S and N. The total H$\hat{I}\pm$ luminosity implies an instantaneous star-formation of 5.3$\pm$0.4 $M_{\odot }$ yr${}^{-1}$ for solar metallicities. The ionizing photon production efficiency, $\log (\hat{I}{\P }_{\mathrm{ion}})$, shows a spatially resolved structure with values of 25.55$\pm$0.03, 25.47$\pm$0.03, and 25.91$\pm$0.09 Hz erg${}^{-1}$ for the integrated galaxy, and clumps S and N, respectively. The H$\hat{I}\pm$ rest-frame equivalent width, EW${}_0$(H$\hat{I}\pm$), is 726${}_{-182}^{+660}$ Ángstrom for the integrated galaxy, but presents extreme values of 531${}_{-96}^{+300}$ Ángstrom and $\ge$1951 Ángstrom for clumps S and N, respectively. The spatially resolved ionizing photon production efficiency is within the range of values measured in galaxies at redshift above six, and well above the canonical value (25.2$\pm$0.1 Hz erg${}^{-1}$). The extreme difference of EW${}_0$(H$\hat{I}\pm$) for Clumps S and N indicates the presence of a recent (<5 Myrs) burst in clump N and a star formation over a larger period of time (e.g., $\sim$50 Myr) in clump S. Finally, clump S and N show very different H$\hat{I}\pm$ kinematics with velocity dispersions of 56$\pm$4 km s${}^{-1}$ and 113$\pm$33 km s${}^{-1}$, likely indicating the presence of outflows or increased turbulence in the clump N. The dynamical mass, $M_{\mathrm{dyn}}$= (2.4$\pm$0.5)$\times$10${}^9$ $M_{\odot }$, is within the range measured with the spatially resolved [OIII]88$\hat{I}¼$m line.

11 pages, 6 figures, published version in A&A