AllBRICQS: The Discovery of Luminous Quasars in the Northern Hemisphere

TL;DR

AllBRICQS-North reports the discovery of 62 spectroscopically confirmed, optically bright quasars in the Northern Hemisphere using Gaia DR3 astrometry and WISE infrared colors, extending the AllBRICQS program beyond its prior southern results. The study details candidate selection, multi-telescope spectroscopic observations, thorough data calibration, redshift determination, and bolometric luminosity estimation, with redshifts spanning roughly 0.09 to 2.48 and bolometric luminosities up to about 10^48 erg s^-1. It highlights a rare, exceptionally luminous FeLoBAL quasar and compares the northern sample with Quaia, SDSS DR16Q, and DESI, revealing gaps in existing catalogs and underlining the necessity of spectroscopic follow-up to achieve a complete census of the brightest quasars. The North sample provides a valuable resource for quasar evolution, black hole growth, and host-galaxy studies across wavelengths, and points to improvements in candidate purity through stricter astrometric cuts.

Abstract

We present the second catalog of bright quasars from the All-sky BRIght, Complete Quasar Survey (AllBRICQS), focusing on spectroscopically observed quasars in the Northern Hemisphere with Galactic latitude $|b| > 10^\circ$. This catalog includes their spectral data, redshifts, and luminosities. AllBRICQS aims to identify the last remaining optically bright quasars using data from the Wide-field Infrared Survey Explorer (WISE) and Gaia all-sky survey Data Release 3 (DR3). AllBRICQS searches for quasars that are brighter than $B_P = 16.5$ or $R_P = 16$ mag in Gaia DR3, based on simple selection criteria. Here, we report 62 new AllBRICQS quasars spanning various types, which include typical broad emission line quasars and the most luminous iron low-ionization broad absorption line quasars discovered to date. Spectroscopic observations were conducted using the Long-Slit Spectrograph on the 1.8-meter telescope at Bohyunsan Optical Astronomy Observatory, YFOSC on the 2.4-meter telescope at Lijiang Observatory, and BFOSC on the 2.16-meter telescope at Xinglong Observatory. We applied flux calibration using ZTF broadband photometry to correct for attenuation due to intermittent thin clouds during the observations. Redshifts were determined using inverse-variance weighted cross-correlation methods. Our targets span the bolometric luminosity range of $44.9<\log \left( L_{\rm bol} / {\rm erg~s^{-1}} \right)<48.0$ at redshifts between 0.09 and 2.48. These confirmed AllBRICQS quasars provide a valuable resource for future research into quasar evolution, black holes, their environments, and their host galaxies across multiple wavelengths.

Figures (14)

• Figure 1: The sky positions of the 75 observed targets are overplotted on the SDSS footprint. Red points with yellow outlines indicate the observed sources. The red and blue dashed lines represent Galactic latitudes of $b = 0^\circ$ and $b = \pm10^\circ$, respectively.
• Figure 2: Distribution of redshift and bolometric luminosity for AllBRICQS quasars in this work (Northern Hemisphere; red circles) and from onken_allbricqs_2023 (Southern Hemisphere; blue triangles), in comparison to the SDSS DR16 Quasar Catalog lyke_sloan_2020, shown as grey contours. The AllBRICQS quasars occupy the bright end of the quasar luminosity distribution, exhibiting significantly higher luminosities than the bulk of the SDSS DR16Q sample. The grey contours correspond to a two-dimensional histogram constructed using 10,000 bins (100 bins per axis), effectively illustrating the density distribution of the SDSS quasars.
• Figure 3: Distributions of key properties of the spectroscopically observed 75 sources in this study. The histograms, displayed from left to right, show Gaia $R_P$ magnitude, $W1-W2$ color, measured redshift, and Galactic latitude. The $W1-W2$ color cut at 0.2 is indicated by a black dashed line. The color values are primarily sourced from the CatWISE catalog eisenhardt_catwise_2020marocco_catwise2020_2021 and supplemented with AllWISE when CatWISE values are unavailable. Although the original AllBRICQS selection used AllWISE magnitudes, the color values shown here are based on CatWISE to reflect the intended selection methodology. As a result, a few objects appear below the 0.2 cut, since they were selected using AllWISE but would not have satisfied the cut under CatWISE photometry. With the exception of redshift, all other properties are derived from Gaia DR3 gaia_collaboration_gaia_2016gaia_collaboration_gaia_2021.
• Figure 4: Comparison of redshift measurements between AllBRICQS spectroscopic values and Quaia photometric estimates. The $x$-axis represents the spectroscopic redshifts obtained from AllBRICQS observations, while the $y$-axis shows the corresponding photometric redshift estimates from the Quaia catalog.
• Figure 5: Distribution of $R_P - W1$ and $W1 - W2$ colors as a function of redshift. The shaded regions along the central dashed lines represent the mean color trends and the 1$\sigma$ scatter within redshift bins of width 0.2. The red shaded region corresponds to our newly discovered 62 quasars, while the black shaded region corresponds to 319 SDSS DR16Q quasars lyke_sloan_2020 that satisfy our bright selection criteria ($B_P < 16.5$ or $R_P < 16.0$ mag). Redshift bins in the SDSS sample containing only a single data point within $z < 2.0$ were excluded. Red pentagons denote the 18 quasars located within the SDSS footprint.