Kavli Affiliate: Luis C. Ho
| First 5 Authors: Jeong Hwan Lee, Minjin Kim, Taehyun Kim, Hyunjin Shim, Luis C. Ho
| Summary:
The upcoming all-sky infrared spectrophotometric SPHEREx mission is set to
provide spatially resolved stellar mass maps of nearby galaxies, offering more
detailed insights than integrated light observations. In this study, we develop
a strategy for estimating stellar mass using SPHEREx by examining the
dependence on different stellar population synthesis (SPS) models and proposing
new scaling relations based on simulated SPHEREx data. We estimate the resolved
stellar masses of 19 nearby late-type galaxies from the PHANGS-MUSE survey,
treating these as fiducial masses. By testing four SPS models covering infrared
wavelengths, i.e., E-MILES, Bruzual & Charlot 2003 (BC03), Charlot & Bruzual
2019 (CB19), and FSPS, we find systematic differences in mass-to-light ratios
at $3.6~{rm mu m}$ ($M_{ast}/L_{rm 3.6mu m}$) among the SPS models. In
particular, BC03 and CB19 yield mass-to-light ratios on average
$sim0.2-0.3~{rm dex}$ lower than those from E-MILES and FSPS. These
mass-to-light ratios strongly correlate with stellar age, indicating a
significant impact of young stellar populations on stellar mass measurements.
Our analysis, incorporating fiducial masses and simulated SPHEREx data,
identifies the $1.6~{rm mu m}$ band as the optimal wavelength for stellar
mass estimation, with the lowest scatter ($0.15-0.20~{rm dex}$) of the stellar
mass. This scatter can be further reduced to $0.10-0.12~{rm dex}$ across all
SPS models by incorporating optical and SPHEREx colors. These results can
provide guidance for measuring the stellar masses of the numerous nearby
galaxies that SPHEREx will survey.
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