Vol 21, No 3 (2021) / Ren

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On the radial velocity calibrations in the LAMOST medium-resolution spectroscopic survey of nebulae

Juan-Juan Ren, Hong Wu, Chao-Jian Wu, Wei Zhang, Jian-Jun Chen, Chih-Hao Hsia, Fan Yang, Chao Liu, Jian-Rong Shi, Yu-Zhong Wu, Hui Zhu, Bin Li, Zhong-Rui Bai, Hao Tian, Yong-Hui Hou

Abstract

Accurate radial velocity determinations of optical emission lines (i.e., [N II ] λλ 6548, 6584, Hα and [S II ] λλ 6717, 6731) are very important for investigating the kinematic and dynamic properties of nebulae. The second stage survey program of Large sky Area Multi-Object fiber Spectroscopic Telescope (LAMOST) has started a sub-survey of nebulae (MRS-N) which will spectroscopically observe the optical emission lines of a large sample of nebulae near the Galactic plane. Until now, 15 MRS-N plates have been observed from September 2017 to June 2019. Based on fitting the sky emission lines in the red band spectra of MRS-N, we investigate the precision of wavelength calibration and find there are systematic deviations of radial velocities (RVs) from ∼ 0.2 to 4 km s−1 for different plates. Especially for the plates obtained in March 2018, the systematic deviations of RVs can be as large as ∼ 4 km s−1, which then go down to ∼ 0.2 – 0.5 km s−1 at the end of 2018 and January 2019. An RV calibration function is proposed for these MRS-N plates, which can simultaneously and successfully calibrate the systematic deviations and improve the precision of RVs.

Keywords


ISM: general — ISM: kinematics and dynamics — technique: spectroscopic — technique: radial velocities

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DOI: https://doi.org/10.1088/1674-4527/21/3/51

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