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Abstract

We present stellar mass values for the 82 galaxies in SHIELD (the Survey of HI in Extremely Low-mass Dwarfs), which is a comprehensive study of the physical properties of extremely low-mass, low-metallicity galaxies (M_HI < 10^7 M⊙ from the ALFALFA Survey). These values were derived using aperture photometry on images taken by the Spitzer Space Telescope at 3.6 μm and by assuming a fixed mass-to-light ratio (specifically, M/L = 0.5). The Spitzer data was analyzed in tandem with optical data from the Hubble Space Telescope (HST), the Sloan Digital Sky Survey (SDSS), and the DESI Legacy Imaging Survey to better distinguish and excise non-galaxy contaminants. Due to the irregular morphologies, low signal-to-noise ratios (SNR), and the presence of foreground and background contaminants for some of these galaxies, additional corrections were applied including point source extraction of bright foreground stars. In combination with 21-cm line derived HI masses, the stellar mass values allow us to derive the baryonic masses and gas fractions. These values can provide a better understanding of fundamental scaling relations such as the Baryonic Tully-Fisher Relation (BTFR) and also provide insights into fundamental galaxy properties. The stellar mass values span the range between 10^5.87 M⊙ ≤ M⋆ ≤ 10^8.05 M⊙ with a decreasing gas fraction as stellar mass increases.

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