Exploring the dust content of Low Surface Brightness Galaxies with multi-wavelength observations

Although it is recognized now that low surface brightness galaxies (LSBs) contribute to a large fraction of the number density of galaxies, many of their properties are still poorly known. The upcoming Legacy Survey of Space and Time (LSST) will be particularly interesting for LSBs since they are difficult to detect with other traditional surveys. LSBs are often considered as “dust poor”, with a very low amount of dust, based on a few studies.

We use, for the first time, a large sample of LSBs and high surface brightness galaxies (HSBs) with deep observational data to study the variation of stellar and dust properties as a function of the surface brightness/surface mass density. Our sample consists of 1631 galaxies that are optically selected (with ugrizy-bands) at z < 0.1 from the North Ecliptic Pole (NEP) wide field.

We use the large multi-wavelength set of ancillary data in this field, ranging from UV to FIR. We measured the optical size and the surface brightness of the targets, and analyzed their spectral energy distribution using the CIGALE fitting code. Based on the measured average r-band surface brightness (mue_avg), our sample consists of 1003 LSBs (mue_avg > 23 mag/arcsec^2) and 628 HSBs (mue_avg ≤ 23 mag/arcsec^2). We found that the specific star formation rate and specific infrared luminosity (total infrared luminosity per stellar mass) remain mostly flat as a function of surface brightness for both LSBs and HSBs that are star-forming but decline steeply for the quiescent galaxies. The majority of LSBs in our sample have negligible dust attenuation (Av < 0.1 mag), except for about 4% of them that show significant attenuation with a mean Av of 0.8 mag. We found that these LSBs with a significant attenuation also have a high r-band mass-to-light ratio (M/Lr > 3 Msun/Lsun), making them outliers from the linear relation of surface brightness and stellar mass surface density. These outlier LSBs also show similarity to the extreme giant LSBs from the literature, indicating a possibly higher dust attenuation in giant LSBs as well.

This work provides a large catalog of LSBs and HSBs with detailed measurements of their several optical and infrared physical properties. Our results suggest that the dust content of LSBs is more varied than previously thought, with some of them having significant attenuation making them fainter than their intrinsic value. With these results, we will be able to make predictions on the dust content of the population of LSBs and how the presence of dust will affect their observations from current/upcoming surveys like JWST and LSST.