标题： LAMOST在一个星系团外区域发现的八颗新类星体 显示英文标题

标题： Eight new quasars discovered by LAMOST in one extragalactic field

摘要： 我们报告了利用2009年12月18日LAMOST调试观测，在一个星系外区域（以赤经$08^h58^m08.2^s$、赤纬$01^o32'29.7''$为中心，半径五度）发现的八颗新类星体。这些类星体的光度范围为$i$16.44至19.34，红移范围为0.898至2.773，虽然其中六个红移小于2.5的类星体在SDSS光谱巡天中被选为目标，但它们并未被识别出来。除了一个缺乏近红外$Y$波段数据的源之外，这八个新类星体中的七个符合一项新的基于近红外和光学颜色的类星体选择标准。其中有两颗类星体位于类星体的“红移沙漠区”（红移范围$z$2.2至3），表明该新标准对于恢复具有类似恒星光学颜色的缺失类星体是有效的。 尽管LAMOST在调试观测期间遇到了一些问题，但我们仍然能够在该区域内识别出另外38个已知的SDSS类星体，其光度范围为$i$16.24至19.10，红移范围为0.297至4.512。我们的识别结果表明，在之前的类星体巡天中可能遗漏了大量的类星体。文中还讨论了本研究结果对未来LAMOST类星体巡天的启示。 显示英文摘要

摘要： 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.