Quasars behind the Galactic plane (GPQs) are important astrometric references and valuable probes of Galactic gas, yet the search for GPQs is difficult due to severe extinction and source crowding in the Galactic plane. In this paper, we present a sample of 204 spectroscopically confirmed GPQs at |b| < 20°, 191 of which are new discoveries. This GPQ sample covers a wide redshift range from 0.069 to 4.487. For the subset of 230 observed GPQ candidates, the lower limit of the purity of quasars is 85.2%, and the lower limit of the fraction of stellar contaminants is 6.1%. Using a multicomponent spectral fitting, we measure the emission line and continuum flux of the GPQs, and estimate their single-epoch virial black hole masses. These GPQs have higher black hole masses and continuum luminosities in comparison to the SDSS DR7 quasar sample. This is due to a selection effect raised from Galactic extinction and target magnitude. The spectral-fitting results and black hole mass estimates are compiled into a main spectral catalog, and an extended spectral catalog of GPQs. The successful identifications prove the reliability of both our GPQ selection methods and the GPQ candidate catalog, shedding light on the astrometric and astrophysical programs that make use of a large sample of GPQs in the future.

Description of gpq2_204_GPQ_spec.tar.gz:

• Name: Spectra of the 204 identified Quasars behind the Galactic Plane
• Short name: GPQ Spectra
• This tar package includes reduced one-dimensional spectra of the 204 identified GPQs in FITS format. The FITS files are named in the format of "spec_Jhhmmss.ss+ddmmss.s_Telescope.fits". The FITS files can be viewed with the splot task of IRAF or read with other standard FITS I/O routines (e.g. astropy.io.fits, specutils).

Description of gpq2_contam_spec.tar.gz:

• Name: Spectra of the 39 contaminants
• Short name: Contam. Spectra
• This tar package includes reduced one-dimensional spectra of the 39 contaminants in FITS format. The FITS files are named in the format of "Bspec_Jhhmmss.ss+ddmmss.s_Telescope.fits". The FITS files can be viewed with the splot task of IRAF or read with other standard FITS I/O routines (e.g. astropy.io.fits, specutils).

Description of gpq2_main_cat_tableA1.fits:

• Name: Main spectral catalog of the 204 identified GPQs
• Short name: GPQ Main Cat.
• The unmeasurable values are indicated with -999.

Description of gpq2_ext_cat_tableA2.fits:

• Name: Extended spectral catalog of the 204 identified GPQs
• Short name: GPQ Ext. Cat.
• The unmeasurable values are indicated with -999.

Description of gpq2_contam_tableC1.fits:

• Name: List of the stellar and galaxy contaminants
• Short name: Contam. list
• The redshift values of stars are filled with 0.

Change Log

Version 2.0

• Fixed wrong fields in the metadata of gpq2_main_cat_tableA1.fits and gpq2_ext_cat_tableA2.fits to match those of the finalised journal version.
• Updated the description in this page with the finalised abstract of the paper.