The Large Sky Area Multi-object Fiber Spectroscopic Telescope (LAMOST) Quasar Survey: Quasar Properties from Data Release 10 to 12

Abstract

We present the quasar catalog from Data Releases 10 to 12 of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Quasar Survey, comprising quasars observed between September 2021 and June 2024. We robustly identified $11,346$ quasars, of which $5,386$ are newly discovered objects not present in the Million Quasars catalog. This release brings the total number of quasars identified by the 12-year LAMOST survey to $67,521$, of which $29,513$ are newly discovered. While the absolute flux calibration for LAMOST quasar spectra from Data Releases 6 to 9 was previously performed using the SDSS/PanSTARRS1 multi-band photometric data, the inherent variability of quasars can affect the flux accuracy. To address this limitation, we recalibrated the LAMOST spectra using (quasi-)simultaneous photometric data from Zwicky Transient Facility (ZTF), which has conducted high-cadence sky monitoring since March 2018. Based on the recalibrated single-epoch spectra, we estimated the emission line fluxes, continuum fluxes, and virial black hole masses. These improved spectra facilitate direct comparison with the spectra of common quasars from the Sloan Digital Sky Survey (SDSS), enabling searches for rare quasars, such as changing-look quasars exhibiting the appearance or disappearance of broad emission lines and broad absorption line quasars. The combined dataset of photometry and multi-epoch spectra will enhance the detections of AGN-related transients, such as Bowen fluorescence flares and extreme variability quasars, thereby improving our understanding of quasar variability.

Figures (18)

• Figure 1: The HEALPix sky distributions of the quasars identified in LAMOST DR10-12 (upper panel) and DR1-12 (lower panel) are shown in equatorial coordinates with the parameters $\rm N_{side=64}$ and area of 0.839 $\rm deg^{2}$ per pixel.
• Figure 2: The distribution in the magnitude-redshift space for the visually confirmed quasars for previous (DR1-9) LAMOST quasar survey (black contours) and in DR10-12 (blue). The absolute magnitudes $\rm M_{i} (z=2)$ are normalized at z=2, following the K-correction of 2006AJ....131.2766R. The upper and right panels show the absolute magnitude and redshift distributions, respectively.
• Figure 3: The distribution of redshift difference ($\Delta z$) for common quasars between this work and SDSS versus LAMOST spectral S/N.
• Figure 4: The distributions of LAMOST quasars in the SDSS-WISE/UKIDSS color diagram. The WISE and UKIDSS magnitudes are in Vega magnitudes. The SDSS magnitudes in the panels (a) and (b) are plotted in AB magnitudes. The dash-dotted lines indicate the criteria previously used in the LAMOST QSO survey 2010MNRAS.406.1583W2012AJ....144...49W.The contours in pink show the distribution for common quasars between this work and Milliquas, while the contours in gray show the distribution for unique quasars identified in this work. The mean ($\mu$) and dispersion ($\sigma$) of each distribution are tabulated in corresponding plots.
• Figure 5: The distribution of time interval between LAMOST and ZTF and the intrinsic variability of quasars in the ZTF $g$ and $r$ bands.