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

TL;DR

This paper presents a comprehensive quasar catalog from LAMOST Data Releases 10 to 12, including newly discovered quasars, improved flux calibration using ZTF data, and analyses of quasar properties and variability.

Contribution

The study introduces recalibrated spectra using ZTF photometry, expanding the LAMOST quasar catalog and enabling detailed variability and rare quasar investigations.

Findings

Identified 11,346 quasars in DR10-12, with 5,386 new discoveries.

Recalibrated spectra using ZTF data improve flux accuracy.

Enabled detection of changing-look and broad absorption line quasars.

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.