J/ApJS/256/14 RVs from LAMOST MRS DR7 stellar spectra (Zhang+, 2021)
Self-consistent stellar radial velocities from LAMOST Medium-Resolution Survey
DR7.
Zhang Bo, Li J., Yang F., Xiong J.-P., Fu J.-N., Liu C., Tian H.,
Li Y.-B., Wang J.-X., Liang C.-X., Zhou Y.-T., Zong W., Yang C.-Q.,
Liu N., Hou Y.-H.
<Astrophys. J. Suppl. Ser., 256, 14 (2021)>
=2021ApJS..256...14Z 2021ApJS..256...14Z
ADC_Keywords: Radial velocities; Spectra, optical; Surveys; Stars, standard
Keywords: Radial velocity ; Surveys ; Astronomy data analysis ;
Astronomy data reduction ; Spectroscopic binary stars ;
Radio spectroscopy ; Spectroscopy ; Catalogs ; Sky surveys ;
Astrostatistics ; Robust regression
Abstract:
Radial velocity (RV) is among the most fundamental physical quantities
obtainable from stellar spectra and is rather important in the
analysis of time-domain phenomena. LAMOST Medium-Resolution Survey
(MRS) DR7 contains five million single-exposure stellar spectra with
spectral resolution R∼7500. However, the temporal variation of the RV
zero-points (RVZPs) of the MRS, which makes the RVs from multiple
epochs inconsistent, has not been addressed. In this paper, we measure
the RVs of 3.8 million single-exposure spectra (for 0.6 million stars)
with signal-to-noise ratios (S/N) higher than 5 based on the
cross-correlation function method, and propose a robust method to
self-consistently determine the RVZPs exposure by exposure for each
spectrograph with the help of Gaia DR2 RVs. Such RVZPs are estimated
for 3.6 million RVs and can reach a mean precision of ∼0.38km/s. The
result of the temporal variation of RVZPs indicates that our algorithm
is efficient and necessary before we use the absolute RVs to perform
time-domain analyses. Validating the results with APOGEE DR16 shows
that our absolute RVs can reach an overall precision of 0.84/0.80km/s
in the blue/red arm at 50<S/N<100 and of 1.26/1.99km/s at 5<S/N<10.
The cumulative distribution function of the standard deviations of
multiple RVs (Nobs≥8) for 678 standard stars reaches 0.45/0.54,
1.07/1.39, and 1.45/1.86km/s in the blue/red arm at the 50%, 90%, and
95% levels, respectively.
Description:
LAMOST, after a five-year low-resolution spectroscopic survey (LRS;
R∼1800, 3800Å<λ<9000Å), started a five-year
medium-resolution spectroscopic survey (MRS; R∼7500,
4950Å<λ<5350Å and 6300Å<λ<6800Å) in 2017
September. DR7, including the data from 2017 September to 2019 June
(about five million spectra for over 800,000 stars) is available to
the international astronomical community.
In this work, 3,753,659 spectra with S/N>5 either in the blue arm or
in the red arm for 600,771 stars are selected.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 220 5739139 The 3.8 million RVs (vobs) obtained from
LAMOST MRS DR7 (v1.1)
table5.dat 189 37624 The RVZP correction values (Δv) for
LAMOST MRS DR7 (v1.1)
table6.dat 84 10320 Selected candidates of RV standard stars from
LAMOST MRS DR7 (v1.1)
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Description of file:
The original table in FITS format are also available on the FTP.
See also:
VI/39 : Model Atmospheres (Kurucz, 1979)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
V/156 : LAMOST DR7 catalogs (Luo+, 2019)
III/284 : APOGEE-2 data from DR16 (Johnsson+, 2020)
J/AJ/137/4377 : List of SEGUE plate pairs (Yanny+, 2009)
J/AJ/156/90 : APOGEE radial velocity standard stars (Huang+, 2018)
J/ApJS/244/27 : Radial velocity measurements in LAMOST-II (Wang+, 2019)
J/ApJ/886/154 : Sgr stream K- & M-giants and BHB stars (Yang+, 2019)
J/ApJS/249/31 : Short period sp. & EBs from LAMOST & PTF (Yang+, 2020)
J/ApJS/246/9 : Stellar parameters of LAMOST stars using SLAM (Zhang+, 2020)
J/ApJS/251/15 : LAMOST-Kepler/K2 survey (LK-MRS) 1st year obs. (Zong+, 2020)
J/MNRAS/506/150 : The GALAH+ Survey DR3 (Buder+, 2021)
http://github.com/hypergravity/paperdata : Associated data to this paper
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 I9 --- obsID [588902003/747816250] LAMOST observational ID
11- 18 I8 min LMJM [83555758/84454742] Local Modified Julian
Date of the beginning of exposure x1440 (G1)
20- 34 F15.7 d BJDmid [/2.45865e+06]?=0 Barycentric Julian date of
the middle of exposure
36- 53 A18 --- planid Plan ID
55- 56 I2 --- spid [1/16] Spectrograph ID
58- 60 I3 --- fiberid [1/250] Fiber ID
62- 72 F11.7 deg RAdeg Right ascension (J2000)
74- 83 F10.7 deg DEdeg [-10/79.1] Declination (J2000)
85- 96 E12.6 --- snrB [0/1e+20] S/N of blue arm (snr_B)
98- 109 E12.6 --- snrR [0/1e+20] S/N of red arm (snr_R)
111- 114 A4 --- lampB Lamp used to calibrate blue arm (lamp_B)
116- 119 A4 --- lampR Lamp used to calibrate red arm (lamp_R)
121- 128 F8.2 km/s rvB [-2785/3784]?=- Radial Velocity (vobs),
blue arm (rv_B)
130- 137 F8.3 km/s e_rvB [0/1065]?=- rvB uncertainty (rverrB)
139- 146 F8.2 K TeffB [3603/14796]?=- Effective temperature of the
best template, blue arm (rvteffB)
148- 153 F6.4 --- ccfmaxB [0.039/0.97]?=- CCF maximum value, blue arm
(ccfmax_B)
155- 162 F8.2 km/s rvR [-3354/3309]?=- Radial Velocity (vobs), red
arm (rv_R)
164- 170 F7.3 km/s e_rvR [0/867]?=- RVR uncertainty (rverrR)
172- 179 F8.2 K TeffR [3603/14796]?=- Effective temperature of the
best template, red arm (rvteffR)
181- 186 F6.4 --- ccfmaxR [0.036/1]?=- CCF maximum value, red arm
(ccfmax_R)
188- 195 F8.2 km/s rvRm [-4101/4043]?=- Radial Velocity (vobs), red
arm without Hα (rv_Rm)
197- 204 F8.3 km/s e_rvRm [0/1765]?=- rvRm uncertainty (rverrRm)
206- 213 F8.2 K TeffRm [3603/14796]?=- Effective temperature of the
best template, red arm without Hα
(rvteffRm)
215- 220 F6.4 --- ccfmaxRm [0.039/0.94]?=- CCF maximum value, red arm
without Hα (ccfmax_Rm)
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- planid Plan ID
20- 27 I8 min LMJM [83555758/84454742] Local Modified Julian
Date of the beginning of exposure x1440 (G1)
29- 30 I2 --- spid [1/16] Spectrograph ID
32- 42 F11.6 km/s RVcor0B [-294/567]?=- Initial guess of RVZP
correction, blue arm (rvcorr0B)
44- 46 I3 --- NsB [0/213] Number of stars in this SEU with Gaia
DR2 RVs, blue arm (nStarfntB)
48- 57 F10.6 km/s RVcor2B [-13.2/15.6]?=- Final RVZP correction
(Δv), blue arm (rvcorr2B)
59- 61 I3 --- NF1B [0/132] Number of stars for first term of
cost function, blue arm (nF1_B)
63- 65 I3 --- NF2B [0/210] Number of stars for second term of
cost function, blue arm (nF2_B)
67- 68 I2 --- NexpB [0/63] Median number of exposures, blue arm
(nOthermedB)
70- 71 I2 --- B_NexpB [0/76] Maximum number of exposures, blue arm
(nOthermaxB)
73- 74 I2 --- b_NexpB [0/63] Minimum number of exposures, blue arm
(nOtherminB)
76- 83 F8.6 km/s e_RVcor2B [0.1/3.1]?=- Uncertainty of the final RVZP
correction (σΔv), blue arm
(rvcorr2unc_B)
85- 95 F11.6 km/s RVcor0R [-882/945]?=- Initial guess of RVZP
correction, red arm (rvcorr0R)
97- 99 I3 --- NsR [0/214] Number of stars in this SEU with Gaia
DR2 RVs, red arm (nStarfntR)
101- 110 F10.6 km/s RVcor2R [-8.2/15]?=- Final RVZP correction
(Δv), red arm (rvcorr2R)
112- 114 I3 --- NF1R [0/132] Number of stars for first term of
cost function, red arm (nF1_R)
116- 118 I3 --- NF2R [0/209] Number of stars for second term of
cost function, red arm (nF2_R)
120- 121 I2 --- NexpR [0/67] Median number of exposures, red arm
(nOthermedR)
123- 124 I2 --- B_NexpR [0/77] Maximum number of exposures, red arm
(nOthermaxR)
126- 127 I2 --- b_NexpR [0/67] Minimum number of exposures, red arm
(nOtherminR)
129- 136 F8.6 km/s e_RVcor2R [0.14/2.5]?=- Uncertainty of the final RVZP
correction (σΔv), red arm
(rvcorr2unc_R)
138- 148 F11.6 km/s RVcor0Rm [-167/978]?=- Initial guess of RVZP
correction, red arm without Hα
(rvcorr0Rm)
150- 152 I3 --- NsRm [0/214] Number of stars in this SEU with Gaia
DR2 RVs,red arm without Hα
(nStarfntRm)
154- 163 F10.6 km/s RVcor2Rm [-8.2/15]?=- Final RVZP correction
(Δv), red arm without Hα
(rvcorr2Rm)
165- 167 I3 --- NF1Rm [0/132] Number of stars for first term of
cost function, red arm without Hα
(nF1_Rm)
169- 171 I3 --- NF2Rm [0/209] Number of stars for second term of
cost function, red arm without Hα
(nF2_Rm)
173- 174 I2 --- NexpRm [0/67] Median number of exposures, red arm
without Hα (nOthermedRm)
176- 177 I2 --- B_NexpRm [0/77] Maximum number of exposures, red arm
without Hα (nOthermaxRm)
179- 180 I2 --- b_NexpRm [0/67] Minimum number of exposures, red arm
without Hα (nOtherminRm)
182- 189 F8.6 km/s e_RVcor2Rm [0.14/3]?=- Uncertainty of the final RVZP
correction (σΔv), red arm without
Hα (rvcorr2unc_Rm)
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 11 F11.7 deg RAdeg Right ascension (J2000) (ra)
13- 22 F10.7 deg DEdeg [0.5/60.5] Declination (J2000) (dec)
24- 31 F8.3 km/s RVmedB [-287/362] Median absolute RV, blue arm
(rvmed_B)
33- 37 F5.3 km/s e_RVmedB [0.04/1.6] Standard deviation of absolute RVs,
blue arm (rvstd_B)
39- 40 I2 --- NexpB [8/77] Number of exposures, blue arm (Nexp_B)
42- 53 F12.8 d tsB [238.3/624.3] Time span, blue arm (ts_B)
55- 62 F8.3 km/s RVmedR [-289/361] Median absolute RV, red arm (rvmed_R)
64- 68 F5.3 km/s e_RVmedR [0.05/2] Standard deviation of absolute RVs,
red arm (rvstd_R)
70- 71 I2 --- NexpR [8/78] Number of exposures, red arm (Nexp_R)
73- 84 F12.8 d tsR [238.3/624.3] Time span, red arm (ts_R)
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Global notes:
Note (G1): The LMJM is 1440x the local modified Julian date of the beginning
of exposure, which is an 8 bit integer assigned to each exposure.
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 16-Aug-2023