Cool DZ white dwarfs I: Identification and spectral analysis

Abstract

White dwarfs with metal lines in their spectra act as signposts for post-main\nsequence planetary systems. Searching the Sloan Digital Sky Survey (SDSS) data\nrelease 12, we have identified 231 cool (<9000 K) DZ white dwarfs with strong\nmetal absorption, extending the DZ cooling sequence to both higher metal\nabundances, lower temperatures, and hence longer cooler ages. Of these 231\nsystems, 104 are previously unknown white dwarfs. Compared with previous work,\nour spectral fitting uses improved model atmospheres with updated line profiles\nand line-lists, which we use to derive effective temperatures and abundances\nfor up to 8 elements. We also determine spectroscopic distances to our sample,\nidentifying two halo-members with tangential space-velocities >300 kms-1. The\nimplications of our results on remnant planetary systems are to be discussed in\na separate paper.\n