DREAMS: Taking the Temperature of a Massive Galaxy at z ~ 11

Abstract

We present a detailed photometric and spectroscopic analysis of Janus-11, a $z=10.7933\pm 0.0006$ galaxy magnified by a factor 1.6 by the galaxy cluster MACS J0416. It was observed with JWST/NIRCam as part of the PEARLS program and with JWST/NIRSpec MSA as part of the DREAMS program. It has M${}_{\mathrm{UV}}=-19.78_{-0.11}^{+0.12}$, and its stellar mass of log(M*/M_sun) = 8.75 (+0.08/-0.10) places it among the most massive known $z>10$ galaxies, while its $A_V=0.54\pm 0.09$ mag and UV slope of $\beta =-1.71\pm 0.26$ are compatible with a red monster classification, albeit among the least obscured members of this population: this could hint at a transition from the red monster to the blue monster phase. Moreover, the [OIII]4363 detection allows for the highest-redshift metallicity measurement based on the [OIII]4363 direct method to date of $12+\log (O/H)=7.74_{-0.10}^{+0.11}$, together with an electron temperature of $T_e$(O${}^{++}$) = $(2.1\pm 0.2)\times 10^4$ K. Its spatially resolved nature, with an effective radius of $136\pm 9$ pc, together with the narrow FWHM of the emission lines ($\lesssim 230$ km s${}^{-1}$, or ${\sigma }_v\lesssim 100$ km s${}^{-1}$), and the lack of significant detections of high-ionization emission lines and broad components, favor an SFG classification, although an AGN contribution cannot be excluded. Janus-11 joins the small sample of spectroscopically confirmed and characterized sources at $z>10$, providing new information on massive systems with non-negligible dust attenuation and well-measured metallicity in this epoch.

arXiv comment9 pages, 8 figures, 3 tables. Submitted to A&A. Comments welcome