Eight new quasars discovered by LAMOST in one extragalactic field

TL;DR

This study reports the discovery of eight new quasars in a specific extragalactic field using LAMOST, demonstrating the effectiveness of a new selection criterion and revealing potential gaps in previous quasar surveys.

Contribution

The paper introduces a new near-IR and optical color-based quasar selection criterion and applies it to identify quasars missed by previous surveys, including those in the redshift desert.

Findings

Discovered 8 new quasars not identified in SDSS.

The new criterion effectively finds quasars in the redshift desert.

Identified 38 known SDSS quasars in the same field.

Abstract

We report the discovery of eight new quasars in one extragalactic field (five degree centered at RA=$08^h58^m08.2^s$, Dec=$01^o32'29.7''$) with the LAMOST commissioning observations on December 18, 2009. These quasars, with $i$ magnitudes from 16.44 to 19.34 and redshifts from 0.898 to 2.773, were not identified in the SDSS spectroscopic survey, though six of them with redshifts less than 2.5 were selected as quasar targets in SDSS. Except one source without near-IR $Y$-band data, seven of these eight new quasars meet a newly proposed quasar selection criterion involving both near-IR and optical colors. Two of them were found in the 'redshift desert' for quasars ($z$ from 2.2 to 3), indicating that the new criterion is efficient for recovering the missing quasars with similar optical colors as stars. Although LAMOST met some problems during the commissioning observations, we were still able to identify other 38 known SDSS quasars in this field, with $i$ magnitudes from 16.24 to 19.10 and redshifts from 0.297 to 4.512. Our identifications imply that a substantial fraction of quasars may be missing in the previous quasar surveys. The implication of our results to the future LAMOST quasar survey is discussed.