Estimating Bolometric Luminosities of Type 1 Quasars with Self-organizing Maps

Abstract We present a new method to calculate bolometric luminosities for unobscured, type 1 quasars with multiband photometric data. Bolometric luminosity is a fundamental property for understanding quasars, and it is commonly estimated from monochromatic luminosities using bolometric corrections that often neglect quasar spectral energy distribution (SED) diversity. We take advantage of the fact that most quasars now have multiband observations from UV to mid-IR and construct SEDs for a well-defined sample of Sloan Digital Sky Survey (SDSS) quasars at 0.5 ≤ z ≤ 2. Based on this fiducial sample, we explore quasar SEDs, their diversity, and their relations with bolometric luminosities. We then use unsupervised neural network self-organizing maps (SOM) to describe the SED diversity and compute the bolometric luminosities with a fully trained SOM model. This method reduces systematical uncertainties compared to the traditional method. In addition, we update the multilinear regression relations between bolometric luminosity and monochromatic luminosities at rest frame 1450 Å, 3000 Å, and 5100 Å. Our method is applicable to large quasar samples with a wide range of luminosity and redshift. We have applied it to the SDSS Data Release 16 quasars. We have also made our code publicly available.