tokens: This paper made use of spectroscopic data that were obtained at the FLWO-1.5 m with FAST, which is operated by Harvard-Smithsonian Centre for Astrophysics. In particular we want to thank Perry Berlind and Mike Calkins for their role in obtaining most of the FLWO-1.5 m/FAST data. The paper also makes use of data obtained as part of the INT Photometric H Survey of the Northern Galactic Plane (IPHAS) carried out at the Isaac Newton Telescope (INT). The INT is operated on the island of La Palma by the Isaac Newton Group in the Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias. All IPHAS data are processed by the Cambridge Astronomical Survey Unit, at the Institute of Astronomy in Cambridge. We also acknowledge the use of data obtained at the INT and the Nordic Optical Telescope as part of a CCI International Time Programme. The work of L.G. and J.F. is supported by the Spanish Ministerio de Economía y Competitividad, and FEDER, under contracts AYA2010-18352 and AYA2013-48623-C2-2-P, and by the Generalitat Valenciana project of excellence PROMETEOII/2014/060. R.R. received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement No. 320964 (WDTracer). N.J.W. was supported by a Royal Astronomical Society fellowship. Finally, we are grateful to Dr. Pablo Reig for his assistance in the classification in the MK system.
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