Vol 19, No 12

Photometrically estimating the spatially-resolved stellar mass-to-light ratios for low-redshift galaxies

Cheng Du, Niu Li, Cheng Li


Abstract The stellar mass-to-light ratio (M∗/L) of galaxies in a given wave band shows tight correlations with optical colors, which have been widely applied as cheap estimators of galaxy stellar masses. These estimators are usually calibrated using either broadband spectral energy distributions (SEDs) or spectroscopy at galactic centers. However, it is unclear whether the same estimators provide unbiased M∗/L for different regions within a galaxy. In this work we employ integral field spectroscopy from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. We also examine the correlations of spatially resolved M∗/L obtained from full spectral fitting, with different color indices, as well as galaxy morphology types, distances to the galactic center, and stellar population parameters such as stellar age and metallicity. We find that the (g − r) color is better than any other color indices, and it provides almost unbiased M∗/L for all the SDSS five bands and for all types of galaxies or regions, with only slight biases depending on stellar age and metallicity. Our analysis indicates that combining multiple colors and/or including other properties to reduce the systematics and scatters of the estimator does not work better than a single color index defined by two bands. Therefore, we have obtained a best estimator with the (g − r) color and applied it to the MaNGA galaxies. Both the two-dimensional map and radial profile of M∗/L are reproduced well in most cases. Our estimator may be applied to obtain surface mass density maps for large samples of galaxies from imaging surveys at both low and high redshifts.


Keywords galaxies: stellar stellar content — galaxies: fundamental parameters — galaxies: general

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