Outshining in the spatially resolved analysis of a strongly lensed galaxy at z = 6.072 with JWST NIRCam
Journal article, 2024
We present JWST/NIRCam observations of a strongly lensed, sub-L∗, multiply imaged galaxy at z=6.072, with magnification factors μ³20 across the galaxy. The galaxy has rich HST, MUSE, and ALMA ancillary observations across a broad wavelength range. Aiming to quantify the reliability of stellar mass estimates of high redshift galaxies, we performed a spatially resolved analysis of the physical properties at scales of ~200 pc, inferred from spectral energy distribution (SED) modelling of five JWST/NIRCam imaging bands covering 0.16 μm < λrest < 0.63 μm on a pixel-by-pixel basis. We find young stars surrounded by extended older stellar populations. By comparing Hα+[Nâ¯II] and [Oâ¯III]+Hβ maps inferred from the image analysis with our additional NIRSpec integral field unit (IFU) data, we find that the spatial distribution and strength of the line maps are in agreement with the IFU measurements. We explore different parametric star formation history (SFH) forms with BAGPIPES on the spatially integrated photometry, finding that a double power-law (DPL) star formation history retrieves the closest value to the spatially resolved stellar mass estimate, and other SFH forms suffer from the dominant outshining emission from the youngest stars, thus underestimating the stellar mass - up to ~0.5 dex. On the other hand, the DPL cannot match the IFU-measured emission lines. Additionally, the ionising photon production efficiency may be overestimated in a spatially integrated approach by ~0.15 dex, when compared to a spatially resolved analysis. The agreement with the IFU measurements implies that our pixel-by-pixel results derived from the broadband images are robust, and that the mass discrepancies we find with spatially integrated estimates are not just an effect of SED-fitting degeneracies or the lack of NIRCam coverage. Additionally, this agreement points towards the pixel-by-pixel approach as a way to mitigate the general degeneracy between the flux excess from emission lines and underlying continuum, especially when lacking photometric medium-band coverage and/or IFU observations. This study stresses the importance of studying galaxies as the complex systems that they are, resolving their stellar populations when possible, or using more flexible SFH parameterisations. This can aid our understanding of the early stages of galaxy evolution by addressing the challenge of inferring robust stellar masses and ionising photon production efficiencies of high redshift galaxies.
Galaxies: structure
Galaxies: photometry
Galaxies: high-redshift
Galaxies: star formation
Author
C. Giménez-Arteaga
Niels Bohr Institute
Cosmic Dawn Center (DAWN)
S. Fujimoto
The University of Texas at Austin
F. Valentino
Cosmic Dawn Center (DAWN)
European Southern Observatory (ESO)
G. Brammer
Niels Bohr Institute
Cosmic Dawn Center (DAWN)
C. A. Mason
Niels Bohr Institute
Cosmic Dawn Center (DAWN)
F. Rizzo
Niels Bohr Institute
Cosmic Dawn Center (DAWN)
V. Rusakov
Cosmic Dawn Center (DAWN)
Niels Bohr Institute
L. Colina
Centro de Astrobiologia (CAB)
G. Prieto-Lyon
Niels Bohr Institute
Cosmic Dawn Center (DAWN)
Pascal A. Oesch
Cosmic Dawn Center (DAWN)
University of Geneva
Niels Bohr Institute
D. Espada
Universidad de Granada
K. E. Heintz
Niels Bohr Institute
Cosmic Dawn Center (DAWN)
Kirsten Knudsen
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
M. Dessauges-Zavadsky
University of Geneva
N. Laporte
Laboratoire d'Astrophysique de Marseille
M. M. Lee
Technical University of Denmark (DTU)
Cosmic Dawn Center (DAWN)
Georgios E. Magdis
Cosmic Dawn Center (DAWN)
Technical University of Denmark (DTU)
Niels Bohr Institute
Y. Ono
University of Tokyo
Y. Ao
University of Science and Technology of China
Chinese Academy of Sciences
Masami Ouchi
National Astronomical Observatory of Japan
The Graduate University for Advanced Studies (SOKENDAI)
University of Tokyo
K. Kohno
Research Center for the Early Universe
University of Tokyo
Anton M. Koekemoer
Space Telescope Science Institute (STScI)
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 686 A63Subject Categories
Astronomy, Astrophysics and Cosmology
DOI
10.1051/0004-6361/202349135