New tidal debris nearby the Sagittarius leading tail from the LAMOST DR2 M giant stars

• 来源期刊: 天文和天体物理学研究
• 年，卷（期）: 2016,（8）
• 页码范围: 61-70
• 页数: 10页
• 语种: 英文
• DOI: 10.1088/1674-4527/16/8/125

摘要

We report two new sets of tidal debris nearby the Sagittarius (Sgr) tidal stream in the north Galactic cap (NGC) identified from the M giant stars in LAMOST DR2.The M giant stars located in the sky area of 210° ＜A＜ 290°,and having a distance of 10-20 kpc and [Fe/H] ＜-0.75 show clear bimodality in their velocity distribution.We denote the two peaks as Vel-3+83 for the one within a mean velocity of -3 km s-1 with respect to that of the well observed Sgr leading tail at the same A and Vel+162+26 for the other one with a mean velocity of 162 km s-1 with respect to the Sgr leading tail.Although the projected A-Vgsr relation of Vel-3+83 is very similar to the Sgr leading tail,the opposite trend in the A-distance relation as compared to the Sgr leading tail suggests Vel-3+83 has a different 3D direction of motion with any branch of the simulated Sgr tidal stream from Law & Majewski.Therefore,we propose it is new tidal debris not related to the Sgr stream.Similarly,the other substructure Vel+162+26,which is the same one as the NGC group discovered by Chou et al.,also moves toward a different direction with respect to the Sgr stream,implying that it may have a different origin than the Sgr tidal stream.