The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) is a Chinese national scientific research facility operated by the National Astronomical Observatories, Chinese Academy of Sciences. It is a special reflecting Schmidt telescope with 4000 fibers in a field of view of 20 deg2 in the sky. Until July 2018, LAMOST has completed its pilot survey, which was launched in October 2011 and ended in June 2012, and the first eight years of regular survey, which was initiated on September 2012[1-7]. In this data release, there are totally 11,214,076 low resolution spectra published, which satisfy the selection criteria that the LAMOST LRS General Catalog also used. The data products of this release can be available from the website http://www.lamost.org/dr8/v1.0/, and they include：
1. Spectra. - There are 11,214,076 flux(relatively)- and wavelength-calibrated spectra in DR8, including 10,388,423 stellar spectra, 219,776 galaxy spectra, 71,786 quasar spectra, and 534,091 unknown object spectra, and these spectra cover the wavelength range of 3690 Å - 9100 Å with a resolution of 1800[2-3] at the 5500 Å.
2. Spectroscopic Parameter Catalogs. - In this data release, seven spectroscopic parameters catalogs are also published，and they are the LAMOST LRS General Catalog, the LAMOST LRS A, F, G and K Type Star catalog, the LAMOST LRS A Type Star Catalog, the LAMOST LRS M Type Star Catalog, the LAMOST LRS Multiple Epoch Catalog, the LAMOST LRS Observed Plate Information Catalog, and the LAMOST LRS Input Catalog respectively. LAMOST targets were cross-matched with Gaia DR2 catalog, and their Gaia source identifiers and G magnitudes are included in five LAMOST LRS catalogs except the LAMOST LRS Observed Plate Information Catalog and LAMOST LRS Input Catalog.There are 38 parameters (such as right ascension, declination, signal to noise ratio (S/N), magnitude, gaia_source_id, gaia_g_mean_mag, and so on) included in the LAMOST LRS General Catalog, the LAMOST LRS A, F, G and K Type Star Catalog, the LAMOST LRS A Type Star Catalog, and the LAMOST LRS M Type Star Catalog, and 24 out of them are also included in the LAMOST LRS Input Catalog. The LAMOST LRS A, F, G and K Type Star Catalog, the LAMOST LRS A Type Star Catalog, and the LAMOST LRS M Type Star Catalog also provide other parameters, for example, atmospheric parameters (effective temperature, surface gravity, and metallicity), spectral line indices, line widths, the metallicity sensitive parameter, and the magnetic activity flag. In addition, the LAMOST LRS Multiple Epoch Catalog provides 13 parameters for targets with multiple observations, and the LAMOST LRS Observed Plate Information Catalog mainly contains nine basic plate information for all published plates.
In section 2, we introduce the released FITS file in detail, and present seven parameter catalogs in section 3.
In this data release, over ten million FITS files are published on-line, and they are named in the form of ‘spec-MMMMM-YYYY_spXX-FFF.fits’. ‘MMMMM’, ‘YYYY’, ‘XX’, and ‘FFF’ represent the local modified Julian day (LMJD) which is a non-negative integer, the plan identity string (PLANID), the spectrograph identity number which is between 1 and 16, and the fiber identity number which is in the range of 1 to 250[8]. In addition, we can also get the LAMOST designation for an object from the DESIG keyword, and it is named in the form ‘LAMOST JHHMMSS.ss+DDMMSS.ss’, where ‘HHMMSS.ss’ is right ascension in unit of HMS, and ‘+DDMMSS.ss’ is declination in unit of DMS.
A primary header data unit (HDU), an optional conforming extension, and other optional special records compose a FITS file. A LAMOST FITS file in this release only contains the primary HDU, which is followed by a primary data array. Sub-section 2.2.1 will introduce keywords of the primary header, and sub-section 2.2.2 will describe the primary data array.
We divided keywords of the primary FITS header into eight groups, and they are mandatory keywords, file information keywords, telescope parameter keywords, observation parameter keywords, spectrograph parameters keywords, weather condition keywords, data reduction parameters keywords and spectra analysis results keywords respectively. We will explain each keyword as follows.
Mandatory keywords are required in every Header Data Unit (HDU), and their value must be written in fixed format.
SIMPLE = T /Primary Header created by MWRFITS v1.8
BITPIX = -32 /
NAXIS = 2 /
NAXIS1 = 3909 /
NAXIS2 = 5 /
EXTEND = T /Extensions may be present
SIMPLE Keyword --- It is required to be the first keyword in the primary header of all FITS file. The value field shall contain a logical constant with the value T if the file conforms to this standard. This keyword is mandatory for the primary header and is not permitted in extension headers. A value of F signifies that the file does not conform to this standard.
BITPIX Keyword --- The value field shall contain an integer, and it shall specify the number of bits that represent a data value. A value of -32 represents IEEE single precision floating point.
NAXIS Keyword --- The value field shall contain a non-negative integer no greater than 999, representing the number of axes in the associated data array. A value of zero signifies that no data follow the header in the HDU.
NAXIS1 and NAXIS2 Keywords --- The value field of these two indexed keywords shall contain a non-negative integer, representing the number of elements along axis n of a data array. The NAXIS1 keyword represents the number of wavelength array, i.e., the column number of the primary data array, and the NAXIS2 keyword indicates the row number of the primary data array.
EXTEND Keyword --- The value field shall contain a logical value indicating whether the FITS file is allowed to contain conforming extensions following the primary HDU. This keyword may only appear in the primary header and must not appear in an extension header. If the value field is T then there may be conforming extensions in the FITS file following the primary HDU. This keyword is only advisory, so its presence with a value T does not require that the FITS file contains extensions, nor does the absence of this keyword necessarily imply that the file does not contain extensions [9].
FILENAME= 'spec-58170-HD070403N361848V01_sp16-210.fits' / OBSID = 648816210 / Unique number ID of this spectrum AUTHOR = 'LAMOST Pipeline' / Who compiled the information DATA_V = 'LAMOST DR8' / Data release version EXTEN0 = 'Flux, Inverse, Wavelength, Andmask, Ormask' / N_EXTEN = 1 / The extension number EXTNAME = 'Flux ' / The extension name ORIGIN = 'NAOC-LAMOST' / Organization responsible for creating this file DATE = '2020-09-14T13:32:41' / Time when this HDU is created (UTC)
FILENAME Keyword --- The value field shall contain a character string giving the name of this FITS file. Take the ‘spec-58643-HD152645N051412B02_sp15-250.fits’ as an example, ‘58643’ is the local modified Julian day, ‘HD152645N051412B02’ is the plan ID, ‘sp15’ is the spectrograph ID, and ‘250’ is the Fiber ID.
OBSID Keyword --- The value field shall a non-negative integer giving the number ID of this spectrum.
AUTHOR Keyword --- This keyword contains a string constant ‘LAMOST Pipline’, which represents the author who produce this file.
DATA_V Keyword --- This keyword contains a string constant, which represents the data release version.
EXTEN0 Keyword --- This keyword contains a string constant ‘Flux Inverse Subcontinuum Andmask Ormask’ explaining each row of the primary data array in a primary HDU.
N_EXTEN Keyword --- The value field shall contain an integer giving the extension number of a FITS file.
EXTNAME Keyword --- This keyword contains a character string to be used to distinguish among different extensions of the same type in A FITS file. Within this context, the primary array should be considered as equivalent to an IMAGE extension.
ORIGIN Keyword --- This ORIGIN keyword contains a string constant ‘NAOC-LAMOST’, which indicates the Organization responsible for this FITS file. ‘NAOC’ represents the abbreviation of National Astronomical Observatories, Chinese Academy of Sciences.
DATE Keyword --- The value field shall contain a character string giving the UTC time when this FITS file is created.
TELESCOP= 'LAMOST ' / GuoShouJing Telescope LONGITUD= 117.58 / [deg] Longitude of site LATITUDE= 40.39 / [deg] Latitude of site FOCUS = 19964 / [mm] Telescope focus CAMPRO = 'NEWCAM ' / Camera program name CAMVER = 'v2.0 ' / Camera program version
TELESCOP Keyword --- This keyword contains a string constant ‘LAMOST’ giving the name of our telescope.
LONGITUD Keyword --- The keyword contains a floating-point constant, which provide the longitude of Xinglong station where LAMOST is mounted on.
LATITUDE Keyword --- The keyword contains a floating-point constant, which provide the latitude of Xinglong station.
FOCUS Keyword --- The FOCUS keyword gives the telescope focus, and its unit is millimeter.
CAMPRO Keyword --- The value field contain a string constant ‘NEWCAM’, which shows the name of camera.
CAMVER Keyword --- The value field contain a character string, which gives the present camera program version.
DATE-OBS= '2018-02-20T12:48:00' / The observation median UTC DATE-BEG= '2018-02-20T20:30:18.0' / The observation start local time DATE-END= '2018-02-20T21:06:58.0' / The observation end local time LMJD = 58170 / Local Modified Julian Day MJD = 58169 / Modified Julian Day LMJMLIST= '83764590-83764603-83764616' / Local Modified Julian Minute list PLANID = 'HD070403N361848V01' / Plan ID in use RA = 103.632286 / [deg] Right ascension of object DEC = 37.801677 / [deg] Declination of object RA_OBS = 103.632286 / [deg] Right ascension during observing DEC_OBS = 37.801677 / [deg] Declination during observing OFFSET = F / Whether there's a offset during observing OFFSET_V= 0.00 / Offset value in arcsecond DESIG = 'LAMOST J065431.74+374806.0' / Designation of LAMOST target FIBERID = 210 / Fiber ID of Object CELL_ID = 'H1502 ' / Fiber Unit ID on the focal plane X_VALUE = '636.4868805740' / [mm] X coordinate of object on the focal plane Y_VALUE = '-545.8922217890' / [mm] Y coordinate of object on the focal plane OBJNAME = '259566658905513' / Name of object OBJTYPE = 'Star ' / Object type from input catalog TSOURCE = 'LEGUE_LCH' / Name of input catalog TCOMMENT= '16612266169952852' / Target information TFROM = 'LCH000001' / Target catalog FIBERTYP= 'Obj ' / Fiber type of object FIBERMAS= 0 / Bitmask of warning values, 0 means all is well MAGTYPE = 'gri ' / Magnitude type of object MAG1 = 13.47 / [mag] Mag1 of object MAG2 = 12.95 / [mag] Mag2 of object MAG3 = 12.75 / [mag] Mag3 of object MAG4 = 99.00 / [mag] Mag4 of object MAG5 = 99.00 / [mag] Mag5 of object MAG6 = 99.00 / [mag] Mag6 of object MAG7 = 99.00 / [mag] Mag7 of object OBS_TYPE= 'OBJ ' / The type of target (OBJ, FLAT, ARC or BIAS) OBSCOMM = 'Science ' / Science or Test RADECSYS= 'FK5 ' / Equatorial coordinate system EQUINOX = 2000.00 / Equinox in years LAMPLIST= 'lamphgcdne.dat' / Arc lamp emission line list SKYLIST = 'skylines.dat' / Sky emission line list NEXP = 3 / Number of valid exposures NEXP_B = 3 / Number of valid blue exposures NEXP_R = 3 / Number of valid red exposures EXPT_B = 1800.00 / [s] Blue exposure duration time EXPT_R = 1800.00 / [s] Red exposure duration time EXPTIME = 1800.00 / [s] Minimum of exposure time for all cameras BESTEXP = 83764590 / LMJM of the best exposure SCAMEAN = 6.90 / [ADU] Mean level of scatter light
DATE-OBS Keyword --- The value field shall contain a character string, which gives the median moment UTC of multiple exposures.
DATE-BEG Keyword --- The value field shall contain a character string giving the observation start Beijing Time.
DATE-END Keyword --- The value field shall contain a character string, which provide the observation end Beijing Time.
LMJD Keyword --- The value field shall be a non-negative integer giving the local modified Julian day.
MJD Keyword --- The value field shall be a non-negative integer giving the modified Julian day.
LMJMLIST Keyword --- The value field shall contain a character string, which shows a list of local modified Julian minute of n times exposures.
PLANID Keyword --- The value field shall contain a character string providing the plan name of the target.
RA Keyword --- The value field shall contain a non-negative real floating-point number, which gives the right ascension of target from the input catalog.
DEC Keyword --- The value field shall contain a real floating-point number, which gives the declination of target from the input catalog.
RA_OBS Keyword --- The value field shall contain a non-negative real floating-point number, which gives the pointing right ascension of target during observation.
DEC_OBS Keyword --- The value field shall contain a real floating-point number, which gives the pointing declination of target during observation.
OFFSET Keyword --- The value field shall contain a boolean value (T or F), which indicates if there is a fiber-offset for the target. The fiber-offset usually applied for the very bright stars (r<11) to avoid CCD saturation.
OFFSET_V Keyword --- The value field shall contain a real floating-point number giving the offset value in unit of arcsec.
DESIG Keyword --- The value field shall contain a character string, which indicates the name of LAMOST target. Like the name of SDSS target, numbers after the character ‘J’ and before ‘+’ represents RA in unit of HMS, and numbers after the character ‘+’ are DEC in unit of DMS.
FIBERID Keyword --- The value field shall contain a non-negative integer between 1 and 250, which shows the fiber ID and shall be used together with the spectrograph ID.
CELL_ID Keyword --- The value field shall contain a character string, which gives the fiber unit ID on the focal plane. LAMOST focal plane is divided into four quadrant named ‘EFGH’ respectively, the first character of this keyword represents the quadrant number, the first two numbers after the first character is the row number in this quadrant, and the next two numbers is the column numbers.
X_VALUE and Y_VALUE Keywords --- The value field shall contain two real floating-point numbers, which give X and Y coordinates of target on the focal plane.
OBJNAME Keyword --- The value field shall contain character string, giving the name ID of object that determined by the RA, DEC and HTM method [10].
OBJTYPE Keyword --- The value field shall contain a character string giving the class of objects in input catalogs.
TSOURCE Keyword --- The value field shall contain a character string which shows the name of organization or person who submit input catalog.
TCOMMENT Keyword --- The value field shall contain a character string which shows the target ID from SDSS, UCAC4, PANSTAR and other catalogues.
TFROM Keyword --- The value field shall contain a character string which shows input catalog submitted by an organization or a person determined by the TSOURCE.
FIBERTYP Keyword --- The value field shall contain a character string, giving the type of fiber assigned to this target. This keyword has six values, i.e., Obj, Sky, F-std, Unused, PosErr and Dead. Obj means the fiber is assigned to an object, including star, galaxy and so on. Sky indicates that the fiber is allocated to take skylight. F-std shows the fiber is used to take the light of a flux calibration standard star. Unused, PosErr and Dead mean the unused fiber, a wrong fiber position, or out of commission respectively.
FIBERMAS Keyword --- The value field shall contain an integer, which is used to show the problems of fibers. If you want to know the exact problem of a fiber, you should first convert the decimal value of ‘FIBERMAS’ to a nine-bit binary number, which is shown in table 1. If the value of a bit is 1, it represents the fiber has associated problem, and the following table 2 lists the associated fiber problem of each bit.
Table 1: Nine bits of the ‘FIBERMAS’ field
|
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
Table 2: The fiber problems
|
Bit |
Problem |
Comment |
|
1 |
NOALLOTTED |
Fiber not allotted |
|
2 |
BADTRACE |
Bad trace from the routine TRACECENTER |
|
3 |
BADFLAT |
Low counts in flat field |
|
4 |
BADARC |
Bad arc solution |
|
5 |
MANYBADPIXEL |
>10% pixels are bad on CCD |
|
6 |
SATURATED |
>10% pixels are saturated |
|
7 |
WHOPPER |
Whopping fiber |
|
8 |
NEARWHOPPER |
Near a whopping fiber |
|
9 |
BADSKYFIBER |
Sky fiber shows extreme residuals |
MAGTYPE Keyword --- The value field shall contain a character string, which shows the magnitude type of a target.
MAG1, MAG2, MAG3, MAG4, MAG5, MAG6 and MAG7 Keywords --- The value field shall contain a real floating-point number between 0 and 100, giving the associated magnitudes of MAGTYPE keyword. For example, The MAGTYPE keyword is ‘ugrizjh’, the MAG1, MAG2, MAG3, MAG4, MAG5, MAG6 and MAG7 keywords provide the magnitudes of u, g, r, i, z, j and h filter respectively.
OBS_TYPE Keyword --- The value field shall contain a character string giving the type of observation targets, which include object, flat, bias and arc lamp.
OBSCOMM Keyword --- The value field shall contain a character string constant representing the observation purposes, which includes observations used for science researches and kinds of tests.
RADECSYS Keyword --- The value field shall contain a character string giving the equatorial coordinate system based on the J2000 position.
EQUINOX Keyword --- The value field shall contain a real floating-point number giving the standard epoch used at present.
LAMPLIST Keyword --- The value field shall contain a character string giving the file name of arc lamp emission line list, which is used in the process of wavelength calibration.
SKYLIST Keyword --- The value field shall contain a character string giving the file name of sky emission line list, which is used in the process of sky subtraction.
NEXP, NEXP_B and NEXP_R Keywords --- The value field of these three keywords shall contain three non-negative integers, which provide numbers of exposures, and numbers of valid blue and red exposures respectively.
EXPT_B and EXPT_R Keywords --- The value fields of these two keywords shall contain two real floating-point numbers, which give exposure duration times of blue and red CCD.
EXPTIME Keyword --- The value field shall contain a real floating-point, which gives the minimum of blue and red total exposures times.
BESTEXP Keyword --- The value field shall contain a integer, which gives the local modified Julian minute of a exposure with maximum S/N in n time exposures.
SCAMEAN Keyword --- The value field shall contain a real floating-point giving the mean level of scatter light, which is the average flux of regions where there is no fiber and is at the left and right edge of a two dimension spectra image.
SPID = 16 / Spectrograph ID SPRA = 104.4324682 / [deg] Average RA of this spectrograph SPDEC = 37.9555196 / [deg] Average DEC of this spectrograph SLIT_MOD= 'x2/3 ' / Slit mode, x1, x2/3 or x1/2
SPID Keyword --- The value field shall contain a non-negative integer numbers between 1 and 16, which provides the spectrograph ID.
SPRA and SPDEC Keywords --- The value field of these two keywords shall contain two real floating-point numbers, which are the averages of RA and DEC of all objects in each spectrograph.
SLIT_MOD Keyword --- The value field shall contain a character string of ‘x2/3’, which gives the slit mode and responds spectra resolution of 1800 respectively at 4750 Å (blue) and 7350 Å (red).
TEMPCCDB= -121.70 / [deg] The temperature of blue CCD TEMPCCDR= -110.70 / [deg] The temperature of red CCD SEEING = 3.30 / [arcsec] Seeing during exposure MOONPHA = 1.93 / [day] Moon phase for a 29.53 days period TEMP_AIR= -3.50 / [deg] Temperature outside dome TEMP_FP = -1.10 / [degree celsius] Temprature of the focal plane DEWPOINT= -23.40 / [deg] DUST = ' ' / Reservation HUMIDITY= 19.60 / WINDD = 153.60 / [deg] Wind direction WINDS = 1.50 / [m/s] Wind speed SKYLEVEL= ' ' / Reservation
TEMPCCDB Keyword --- The value field shall contain a real floating-point number, which provides the temperature of blue CCD. The unit ‘degree’ represents centigrade degree.
TEMPCCDR Keyword --- The value field shall contain a real floating-point number, which provides the temperature of red CCD. The unit ‘degree’ represents centigrade degree.
SEEING Keyword --- The value field shall contain a real floating-point number giving seeing during exposure, which is calculated by manually measuring the full width at half maximum of guide star image.
MOONPHA Keyword --- The value field shall contain a real floating-point number giving the moon phase.
TEMP_AIR Keyword --- The value field shall contain a real floating-point number giving the temperature outside dome, which is measured by automatic weather instrument. The unit ‘degree’ represents centigrade degree.
TEMP_FP Keyword --- The value field shall contain a real floating-point number giving the temperature of focal plane, which is measured by automatic weather instrument. The unit ‘degree’ represents centigrade degree.
DEWPOINT Keyword --- The value field shall contain a real floating-point number giving the dew-point temperature, which is also measured by the automatic weather instrument. The unit ‘degree’ represents centigrade degree.
DUST Keyword --- The value of this keyword is temporarily empty at present, because the dust measuring instrument is now in debugging, and we will write this parameters into fits header when problems are resolved.
HUMIDITY Keyword --- The value field shall contain a real floating-point number between 0 and 1, which gives humidity in the air.
WINDD Keyword --- The value field shall contain a real floating-point number which records the instantaneous wind direction when start exposure, and the direction of north is the 0 degree wind direction.
WINDS Keyword --- The value field shall contain a real floating-point number which records the instantaneous wind speed when start exposure, and wind direction and speed are also measured also by the automatic weather instrument.
SKYLEVEL Keyword --- This keyword is NULL now, because the instrument is debugging.
EXTRACT = 'aperture' / Extraction method SFLATTEN= T / Super flat has been applied PCASKYSB= T / PCA sky-subtraction has been applied NSKIES = 37 / Sky fiber number SKYCHI2 = 2.0 / Mean chi^2 of sky-subtraction SCHI2MIN= 1.7 / Minimum chi^2 of sky-subtraction SCHI2MAX= 2.4 / Maximum chi^2 of sky-subtraction NSTD = 6 / Number of (good) standard stars FSTAR = '216-141-192-191-112-214' / FiberID of flux standard stars FCBY = 'auto ' / Standard stars origin (auto, manual or catalog) HELIO = T / Heliocentric correction HELIO_RV= 22.19496 / [km/s] Heliocentric correction VACUUM = T / Wavelengths are in vacuum NWORDER = 2 / Number of linear-log10 coefficients WFITTYPE= 'LOG-LINEAR' / Linear-log10 dispersion COEFF0 = 3.5682 / Central wavelength (log10) of first pixel COEFF1 = 0.0001 / Log10 dispersion per pixel WAT0_001= 'system=linear' / WAT1_001= 'wtype=linear label=Wavelength units=Angstroms' / CRVAL1 = 3.5682 / Central wavelength (log10) of first pixel CD1_1 = 0.0001 / Log10 dispersion per pixel CRPIX1 = 1 / Starting pixel (1-indexed) CTYPE1 = 'LINEAR ' / DC-FLAG = 1 / Log-linear flag
EXTRACT Keyword --- The value field shall contain a character string, which indicates the method of spectrum extraction. In LAMOST spectra reduction pipeline, only the aperture method is applied to spectra extraction.
SFLATTEN Keyword --- The value of this keyword shall be Boolean, which represents whether or not use the super flat. In LAMOST spectra reduction pipeline, super flat is used to make the fiber-to-fiber relative efficiency around 1.
PCASKYSB Keyword --- The value of this keyword shall be Boolean, which represents whether or not use the PCA method to subtract sky light. In LAMOST spectra reduction pipeline, the PCA method is used to subtract sky light at the wavelength range larger than 7200 Å.
NSKIES Keyword --- The value field shall contain an integer, which shows the number of sky fiber in a spectrograph.
SKYCHI2 Keyword --- The value field shall contain a real floating-point, which gives the mean chi-square of sky-subtraction. In the process of LAMOST spectra reduction, super sky is obtained by spline fitting m sky spectra. And thus, the chi-square between the super sky and each sky spectra in an exposure, and the average chi-square of m sky spectra can also be able to obtain. Assuming n times exposures, there will be 2n average chi-square because of n blue spectra and n red spectra, and this keyword will be evaluated by calculating the mean value of these 2n average chi-squares.
SCHI2MIN Keyword --- The value field shall contain a real floating-point, which gives the minimum chi-square of sky-subtraction. As mentioned above, there will be 2n average chi-squares assuming n time exposures, and this keyword will be the minimum of these chi-squares.
SCHI2MAX Keyword --- The value field shall contain a real floating-point, which gives the maximum chi-square of sky-subtraction. As mentioned above, there will be 2n average chi-squares assuming n time exposures, this keyword will be the maximum of these chi-squares.
NSTD Keyword --- The value field shall contain a non-negative integer, which shows the number of flux standard stars with good spectra quality.
FSTAR Keyword --- The value field shall contain a character string giving the fiber identity numbers of flux standard stars, which are separated by the symbol ‘-’. It should be noted that the fiber identity number of each flux standard star starts from zero.
FCBY Keyword --- The value field shall contain a character string giving the selection methods of flux standard stars, which include auto, manual and catalog. Auto represents the standard stars are selected by the LAMOST reduction pipeline, manual means they are picked out by experienced staffs, and catalog indicates the standard stars are provided by the input catalog.
HELIO Keyword --- The value of this keyword shall be Boolean, which represents whether or not to perform the heliocentric correction.
HELIO_RV Keyword --- The value field shall contain a real floating-point, which gives the radial velocity used to carry out the heliocentric correction.
VACUUM Keyword --- The value of this keyword shall be Boolean, which represents whether or not the LAMOST spectra is converted to vacuum wavelength.
NWORDER Keyword --- The value of this keyword shall contain an integer, which gives number of linear-log10 coefficients.
WFITTYPE Keyword --- The value field shall contain a character string giving linear-log10 dispersion.
COEFF0 Keyword --- The value field shall contain a real floating-point number, which provides central wavelength (log10) of first pixel.
COEFF1 Keyword --- The value field shall contain a real floating-point number giving log10 dispersion per pixel.
WAT0_001 Keyword --- The value field contains a character string.
WAT1_001 Keyword --- The value field contains a character string.
CRVAL1 Keyword --- The value field shall contain a real floating-point number, which gives the coordinate value of the reference pixel provided by the CRPIX1 keyword [11].
CD1_1 Keyword --- The value field shall contain a real floating-point giving the dispersion of per pixel.
CRPIX1 Keyword --- The value of this keyword shall contain an integer, which sets the reference pixel location on pixel axis [11].
CTYPE1 Keyword --- The value field shall contain a character string, which will have the value ‘LINEAR’ to define the wavelength axes to be linear [12].
DC-FLAG Keyword --- The value of this keyword shall be Boolean, a value of 0 defines a linear sampling of the dispersion and a value of 1 defines a logarithmic sampling of the dispersion [12].
VERSPIPE= 'v2.9.7 ' / Version of Pipeline CLASS = 'STAR ' / Class of object SUBCLASS= 'M0 ' / Subclass of object Z = -0.00019311 / Redshift of object Z_ERR = 0.00001923 / Redshift error of object ZFLAG = 'PIPILINE' / Which method computes the redshift SNRU = 0.66 / SNR of u filter SNRG = 13.32 / SNR of g filter SNRR = 36.14 / SNR of r filter SNRI = 78.57 / SNR of i filter SNRZ = 63.93 / SNR of z filter
VERSPIPE Keyword --- The value field shall contain a character string constant, which provides the version of LAMOST pipelines used to spectra processing and analysis. In this data release, the value of VERSPIPE is ‘v2.9.7’. It should be noted that, ‘v2.9’ is the version of spectra reduction pipeline, ‘v7’ is the version of spectra analysis pipeline, and ‘v2.9.7’ combines these two versions together.
CLASS Keyword --- The value field shall contain a character string providing the classification result determined by the LAMOST spectra analysis pipeline, which includes ‘STAR’, ‘GALAXY’, ‘QSO’ or ‘Unknown’.
SUBCLASS Keyword --- The value field shall contain a character string, which gives a sub-classification results for stars. This keyword provides a more detailed spectra type for F, G, K and M dwarfs, and spectra and photometric type for A type stars. For galaxies, quasars or unknown type objects, this keyword is set to ‘Non’ now.
Z Keyword --- The value field shall contain a real floating-point number providing redshift for a target, which is determined mainly by the LAMOST spectra analysis pipeline. For the case that redshift is unable to calculate by the pipeline, it will be manually determined through measuring the shifts of some spectral line centers. If the quality of a spectrum is poor, or it is classified as ‘Unknown’, its redshift is artificially set to -9999.
Z_ERR Keyword --- The value field shall contain a real floating-point number, which gives redshift error of a target.
ZFLAG Keyword --- The value field shall contain three possible methods to compute the Z value: ‘PIPELINE’, ‘EYE-CHECK’, and ‘LASP’.
SNRU, SNRG, SNRR, SNRI and SNRZ Keywords --- The value fields of these five keywords shall contain five real floating-point numbers, which give the signal to noise ratios (S/Ns) of u, g, r, i and z bands. Using the center wavelength and bandwidth, we can obtain the wavelength range of each SDSS band, and then the S/N in each band is the median value of each pixel S/N in this band. However, it is possible that not all pixel is valid to calculate S/N. Thus, the S/N is artificially set as -9999 when the number of valid pixels used to estimate S/N is less than half of the total pixel number in each band.
The primary data array has 5 rows and NAXIS1 (a keyword explained previously) columns, and table 3 explains the data in each row.
Table 3: Primary data array of LAMOST fits file
|
Row Number |
Data |
Type |
|
5 |
Ormask |
float |
|
4 |
Andmask |
float |
|
3 |
WaveLength |
float |
|
2 |
Inverse Variance |
float |
|
1 |
Flux |
float |
The first row is flux, and the second row stores the ‘inverse variance’ (one over sigma-squared, and sigma is the uncertainty), which can be used to estimate S/N of each pixel (flux * (inverse variance) ^ 0.5). The third row stores wavelength in unit of angstrom, which can be directly used by users. The ‘andmask’ information in fourth row is a decimal integer determined by a six-bit binary number shown in table 4, which represents six situations respectively as listed in table 5. The associated bit of ‘andmask’ will be set to 1, if the case always appears in each exposure. Like the ‘andmask’, the ‘ormask’ information in fifth row is also a decimal integer determined by a six-bit binary number. The difference is that each bit of ‘ormask’ will be set to 1 if the related case happens in any exposure.
Table 4: Six bits of ‘Andmask’ and ‘Ormask’
|
6 |
5 |
4 |
3 |
2 |
1 |
Table 5: The significance of six bits of ‘Andmask’ and ‘Ormask’
|
Bit |
Keyword |
Comments |
|
1 |
BADCCD |
bad pixel on CCD |
|
2 |
BADPROFILE |
bad profile in extraction |
|
3 |
NOSKY |
no sky information at this wavelength |
|
4 |
BRIGHTSKY |
sky level too high |
|
5 |
BADCENTER |
fiber trace out of the CCD |
|
6 |
NODATA |
no good data |
For a spectrum, if you want to check which case in table 5 has happened in the spectrum reduction process, you can firstly convert the decimal ‘Andmask’ and ‘Ormask’ to a six-bit binary number. Then, a case must has happened in each exposure if associated bit is 1 in binary ‘Andmask’, and a case must has happened at least one time if associated bit is 1 in binary ‘Ormask’.
In this section, we introduce seven LAMOST catalogs published in this data release, which can be available from the website of http://www.lamost.org/dr8/v1.0/catalogue. They are the LAMOST LRS General Catalog, the LAMOST LRS A, F, G and K Type Star Catalog, the LAMOST LRS A Type Star Catalog, the LAMOST LRS M Type Star Catalog, the LAMOST LRS Multiple Epoch Catalog, the LAMOST LRS Observed Plate Information Catalog, and the LAMOST LRS Input Catalog, respectively.
LAMOST targets were cross-matched with Gaia DR2 catalog, and their Gaia source identifiers, i.e., the “source_id” fields, and Gaia G magnitudes, i.e., the “phot_g_mean_mag” fields, are included in five LAMOST LRS catalogs except the LAMOST LRS Observed Plate Information Catalog and LAMOST LRS Input Catalog.
Here, it should note that, the LAMOST LRS A, F, G and K Type Star Catalog, the LAMOST LRS A Type Star Catalog, and the LAMOST LRS M Type Star Catalog are all subsets of the LAMOST LRS General Catalog. In addition, except galaxies, quasars and unknown objects, most majorities of objects not included in above three sub-tables are F, G and K type stars, which do not satisfy the select criterion, and the remaining small fraction of these objects are O and B type stars, white dwarf stars, emission line stars, carbon stars, spectroscopic double stars and so on.
The following table 6, 7, 8, 9, 10, 11, and 12 separately show all fields of above seven catalogs, and provide comment for each field. Most fields in these tables are explained in detail in sub-section 2.2.1, and we only introduce the fields, which are not introduced above.
In this sub-section, we present the LAMOST LRS General Catalog. In this table, it includes objects obtained from LAMOST pilot survey and eight-year regular survey. For galaxy, QSO and M type stars, all of them are in the catalog. But for other type targets, we published spectra with r band S/Ns larger than 2, or g band S/Ns larger than 5, or i band S/Ns larger than 5.
We totally published 11,214,076 spectra in this table, including 10,388,423 stellar spectra, 219,776 galaxy spectra, 71,786 quasar spectra, and 534,091 unknown object spectra. In addition, there are 7,159,477 spectra with g band S/Ns larger than 10, 9,599,029 spectra with i band S/Ns larger than 10, and 7,077,066 spectra with g band S/Ns larger than 10 and i band S/Ns larger than 10.
All parameters of this catalog are listed in table 6, and most majorities of them are explained in section 2.2.1 in detail. In order to prevent saturation, we artificially add offsets to the equatorial coordinates from input catalog for a fraction of luminous stars during observation. Thus, we add four new fields in catalogs except the LAMOST LRS Observed Plate Information Catalog, and they are ‘ra_obs’, ‘dec_obs’, ‘offsets’ and ‘offsets_v’ respectively. The fields ‘ra_obs’ and ‘dec_obs’ are fiber pointing right ascension and declination during observation, and the fields ‘ra’ and ‘dec’ are the equatorial coordinates from the input catalog. The field ‘offsets’ represents whether there is a fiber offset during observation, and the field ‘offsets_v’ gives the offset value of equatorial coordinator in the input catalog if the ‘offsets’ field is true. Note that, the fields of ‘offsets’ and ‘offsets_v’ also in other four catalogs except the LAMOST LRS Observed Plate Information Catalog are the same as the fields of ‘offset’ and ‘offset_v’ in the primary FITS header (in subsection 2.2.1.4), and the reason adding ‘s’ after ‘offset’ lie in ‘offset’ is the keyword of the data base. The fields ‘z’ and ‘z_err’ are redshift and uncertainty respectively, which were given by the LAMOST 1D pipeline, and they are set to -9999 if the redshift is unable to be estimated. Besides, the ‘fibermask’ field is the same as the ‘FIBERMAS’ field in the ‘Pimary FITS Header’, which has already detailedly described in subsection 2.2.1.4.
On the website http://www.lamost.org/dr8/v1.0/catalogue, we provide two format LAMOST LRS General Catalogs, which include a FITS table and a CSV table, and the two catalog files have the same contents.
Table 6: LAMOST LRS General Catalog
|
Field (unit) |
Type |
Comment |
|
obsid |
long integer |
Unique Spectra ID |
|
designation |
varchar |
Target Designation |
|
obsdate |
char |
Target Observation Date |
|
lmjd |
char |
Local Modified Julian Day |
|
mjd |
char |
Modified Julian Day |
|
planid |
char |
Plan Name |
|
spid |
integer |
Spectrograph ID |
|
fiberid |
integer |
Fiber ID |
|
ra_obs (degree) |
float |
Fiber Pointing Right Ascension |
|
dec_obs (degree) |
float |
Fiber Pointing Declination |
|
snru |
float |
S/N of u filter |
|
snrg |
float |
S/N of g filter |
|
snrr |
float |
S/N of r filter |
|
snri |
float |
S/N of i filter |
|
snrz |
float |
S/N of z filter |
|
objtype |
varchar |
Object Type |
|
class |
varchar |
Spectra Type |
|
subclass |
varchar |
Stellar Sub-Class |
|
z |
float |
Redshift |
|
z_err |
float |
Redshift Uncertainty |
|
magtype |
varchar |
Target Magnitude Type |
|
mag1 (mag) |
float |
Associated Magnitude 1 |
|
mag2 (mag) |
float |
Associated Magnitude 2 |
|
mag3 (mag) |
float |
Associated Magnitude 3 |
|
mag4 (mag) |
float |
Associated Magnitude 4 |
|
mag5 (mag) |
float |
Associated Magnitude 5 |
|
mag6 (mag) |
float |
Associated Magnitude 6 |
|
mag7 (mag) |
float |
Associated Magnitude 7 |
|
tsource |
varchar |
Organization or person who submit input catalog |
|
fibertype |
varchar |
Fiber Type of target [Obj, Sky, F-std, Unused, PosErr, Dead] |
|
tfrom |
varchar |
Input catalog submitted by an organization or a person determined by the tsource |
|
tcomment |
varchar |
Target ID from SDSS, UCAC4, PANSTAR and other catalogues |
|
offsets |
Bool |
Whether there is a fiber offset during observation |
|
offsets_v (arcsec) |
float |
If the ‘offsets’ field is true, ‘offsets_v’ gives the offset distance from the target’s coordinator in input catalog |
|
ra (degree) |
float |
Right Ascension from input catalog |
|
dec (degree) |
float |
Declination from input catalog |
|
fibermask |
integer |
Possible fiber problems |
|
gaia_source_id |
char |
The "source_id" field of Gaia DR2 catalog |
|
gaia_g_mean_mag |
float |
The "phot_g_mean_mag" field of Gaia DR2 catalog |
In this sub-section, we introduce the LAMOST LRS A, F, G and K Type Star Catalog. We totally published 6,478,063 spectra in this catalog, including 100,468 A type star spectra, 1,983,821 F type star spectra, 3,249,746 G type star spectra and 1,144,028 K type star spectra.
These spectra are selected with the criterion of S/N in g band larger than 6 in dark nights, and S/N in g band larger than 15 in bright nights. All fields of this catalog are listed in table 7, the fields of ‘teff’, ‘logg’, ‘feh’ and ‘rv’ are the effective temperatures, surface gravities, metallicities and radial velocity, which were determined by the LAMOST Stellar Parameter pipeline (LASP). The uncertainty of atmospheric parameters and radial velocity is affected mainly by two factors, i.e., the S/N and the best-matched chi-square. Using a sample of stars subtracting variable stars and having multiple observations, the precisions of atmospheric parameters and radial velocity for each observation and the relationship between the precisions and S/N were determined. Besides, the function relationship of the best-matched chi-square and S/N can also be obtained with another sample of stars. The ‘teff_err’, ‘logg_err’, ‘feh_err’ and ‘rv_err’ are uncertainties of atmospheric parameters and radial velocity, respectively, and they are estimated by the above best-matched chi-square, S/N, and the two relationships.
It should be noted that A type stars in this catalog is a subset of the LAMOST LRS A Type Star Catalog, and they all have high S/N spectra. We provide two format LAMOST LRS A, F, G and K Type Star Catalogs, which include a FITS table and a CSV table, and can be available from the website http://www.lamost.org/dr8/v1.0/catalogue.
Table 7: LAMOST LRS A, F, G and K Type Star Catalog
|
Field (unit) |
Type |
Comment |
|
obsid |
long integer |
Unique Spectra ID |
|
designation |
varchar |
Target Designation |
|
obsdate |
char |
Target Observation Date |
|
lmjd |
char |
Local Modified Julian Day |
|
mjd |
char |
Modified Julian Day |
|
planid |
char |
Plan Name |
|
spid |
integer |
Spectrograph ID |
|
fiberid |
integer |
Fiber ID |
|
ra_obs (degree) |
float |
Fiber Pointing Right Ascension |
|
dec_obs (degree) |
float |
Fiber Pointing Declination |
|
snru |
float |
S/N of u filter |
|
snrg |
float |
S/N of g filter |
|
snrr |
float |
S/N of r filter |
|
snri |
float |
S/N of i filter |
|
snrz |
float |
S/N of z filter |
|
objtype |
varchar |
Object Type |
|
class |
varchar |
Spectra Type |
|
subclass |
varchar |
Stellar Sub-Class |
|
z |
float |
Redshift |
|
z_err |
float |
Redshift Uncertainty |
|
magtype |
varchar |
Target Magnitude Type |
|
mag1 (mag) |
float |
Associated Magnitude 1 |
|
mag2 (mag) |
float |
Associated Magnitude 2 |
|
mag3 (mag) |
float |
Associated Magnitude 3 |
|
mag4 (mag) |
float |
Associated Magnitude 4 |
|
mag5 (mag) |
float |
Associated Magnitude 5 |
|
mag6 (mag) |
float |
Associated Magnitude 6 |
|
mag7 (mag) |
float |
Associated Magnitude 7 |
|
tsource |
varchar |
Organization or person who submit input catalog |
|
fibertype |
varchar |
Fiber Type of target [Obj, Sky, F-std, Unused, PosErr, Dead] |
|
tfrom |
varchar |
Input catalog submitted by an organization or a person determined by the tsource |
|
tcomment |
varchar |
Target ID from SDSS, UCAC4, PANSTAR and other catalogues |
|
offsets |
Bool |
Whether there is a fiber offset during observation |
|
offsets_v (arcsec) |
float |
If the ‘offsets’ field is true, ‘offsets_v’ gives the offset distance from the target’s coordinator in input catalog |
|
ra (degree) |
float |
Right Ascension from input catalog |
|
dec (degree) |
float |
Declination from input catalog |
|
teff (K) |
float |
Effective Temperature obtained by the LASP |
|
teff _err (K) |
float |
Effective Temperature Uncertainty obtained by the LASP |
|
logg (dex) |
float |
Surface Gravity obtained by the LASP |
|
logg_err (dex) |
float |
Surface Gravity Uncertainty obtained by the LASP |
|
feh(dex) |
float |
Metallicity obtained by the LASP |
|
feh_err (dex) |
float |
Metallicity Uncertainty obtained by the LASP |
|
rv (km/s) |
float |
Heliocentric Radial Velocity obtained by the LASP |
|
rv_err (km/s) |
float |
Uncertainty of Heliocentric Radial Velocity obtained by the LASP |
|
gaia_source_id |
char |
The "source_id" field of Gaia DR2 catalog |
|
gaia_g_mean_mag |
float |
The "phot_g_mean_mag" field of Gaia DR2 catalog |
In this sub-section, we introduce the LAMOST LRS A Type Star Catalog. We publish all 629,041 A type star spectra in this catalog, which are also in the LAMOST LRS General Catalog. Table 8 shows all fields of this catalog, the ‘class’ field presents the two-dimension spectral classification results, and nearly all A type stars have luminosity class, which are provided by the LAMOST 1D pipeline. The fields ‘kp6’, ‘kp12’, ‘kp18’, ‘halpha12’, ‘halpha24’, ‘halpha48’, ‘halpha70’, ‘hbeta12’, ‘hbeta24’, ‘hbeta48’, ‘hbeta60’, ‘hgamma12’, ‘hgamma24’, ‘hgamma48’, ‘hgamma54’, ‘hdelta12’, ‘hdelta24’, ‘hdelta48’, ‘hdelta64’, ‘paschen13’, ‘paschen142’ and ‘paschen242’ are line indices of Ca II K, Halpha, Hbeta, Hgamma, Hdelta, and Paschen lines respectively, and the numbers in their names are the used band widths in the unit of angstrom. It should be noted that the three Paschen line indices use the local continua at 8467.5 Å, 8598.0 Å, and 8751.0 Å respectively. Besides, the fields ‘halpha_d02’, ‘hbeta_d02’, ‘hgama_d02’, and ‘hdelta_d02’ are the widths at 20% below the local continua of four BALMER lines. If these line indices and line widths were not available, they were set to -9999.
We provide two formats LAMOST LRS A Type Star Catalogs, which include a FITS table and a CSV table, and can be download from the website http://www.lamost.org/dr8/v1.0/catalogue.
Table 8: LAMOST LRS A Type Star Catalog
|
Field (unit) |
Type |
Comment |
|
obsid |
long integer |
Unique Spectra ID |
|
designation |
varchar |
Target Designation |
|
obsdate |
char |
Target Observation Date |
|
lmjd |
char |
Local Modified Julian Day |
|
mjd |
char |
Modified Julian Day |
|
planid |
char |
Plan Name |
|
spid |
integer |
Spectrograph ID |
|
fiberid |
integer |
Fiber ID |
|
ra_obs (degree) |
float |
Fiber Pointing Right Ascension |
|
dec_obs (degree) |
float |
Fiber Pointing Declination |
|
snru |
float |
S/N of u filter |
|
snrg |
float |
S/N of g filter |
|
snrr |
float |
S/N of r filter |
|
snri |
float |
S/N of i filter |
|
snrz |
float |
S/N of z filter |
|
objtype |
varchar |
Object Type |
|
class |
varchar |
Stellar Class |
|
subclass |
varchar |
Stellar Sub-Class |
|
z |
float |
Redshift |
|
z_err |
float |
Redshift Uncertainty |
|
magtype |
varchar |
Target Magnitude Type |
|
mag1 (mag) |
float |
Associated Magnitude 1 |
|
mag2 (mag) |
float |
Associated Magnitude 2 |
|
mag3 (mag) |
float |
Associated Magnitude 3 |
|
mag4 (mag) |
float |
Associated Magnitude 4 |
|
mag5 (mag) |
float |
Associated Magnitude 5 |
|
mag6 (mag) |
float |
Associated Magnitude 6 |
|
mag7 (mag) |
float |
Associated Magnitude 7 |
|
tsource |
varchar |
Organization or person who submit input catalog |
|
fibertype |
varchar |
Fiber Type of target [Obj, Sky, F-std, Unused, PosErr, Dead] |
|
tfrom |
varchar |
Input catalog submitted by an organization or a person determined by the tsource |
|
tcomment |
varchar |
Target ID from SDSS, UCAC4, PANSTAR and other catalogues |
|
offsets |
Bool |
Whether there is a fiber offset during observation |
|
offsets_v (arcsec) |
float |
If the ‘offsets’ field is true, ‘offsets_v’ gives the offset distance from the target’s coordinator in input catalog |
|
ra (degree) |
float |
Right Ascension from input catalog |
|
dec (degree) |
float |
Declination from input catalog |
|
kp12 (Å) |
float |
Ca II K line index with band widths of 12 Å |
|
kp18 (Å) |
float |
Ca II K line index with band widths of 18 Å |
|
kp6 (Å) |
float |
Ca II K line index with band widths of 6 Å |
|
hdelta12 (Å) |
float |
Hdelta Line Index with band widths of 12 Å |
|
hdelta24 (Å) |
float |
Hdelta Line Index with band widths of 24 Å |
|
hdelta48 (Å) |
float |
Hdelta Line Index with band widths of 48 Å |
|
hdelta64 (Å) |
float |
Hdelta Line Index with band widths of 64 Å |
|
hgamma12 (Å) |
float |
Hgamma Line Index with band widths of 12 Å |
|
hgamma24 (Å) |
float |
Hgamma Line Index with band widths of 24 Å |
|
hgamma48 (Å) |
float |
Hgamma Line Index with band widths of 48 Å |
|
hgamma54 (Å) |
float |
Hgamma Line Index with band widths of 54 Å |
|
hbeta12 (Å) |
float |
Hbeta Line Index with band widths of 12 Å |
|
hbeta24 (Å) |
float |
Hbeta Line Index with band widths of 24 Å |
|
hbeta48 (Å) |
float |
Hbeta Line Index with band widths of 48 Å |
|
hbeta60 (Å) |
float |
Hbeta Line Index with band widths of 60 Å |
|
Halpha12 (Å) |
float |
Halpha Line Index with band widths of 12 Å |
|
Halpha24 (Å) |
float |
Halpha Line Index with band widths of 24 Å |
|
halpha48 (Å) |
float |
Halpha Line Index with band widths of 48 Å |
|
halpha70 (Å) |
float |
Halpha Line Index with band widths of 70 Å |
|
paschen13 (Å) |
float |
Paschen line index from local continuum at 8467.5 with band widths of 13.0 |
|
paschen142 (Å) |
float |
Paschen line index from local continuum at 8598.0 with band widths of 42.0 |
|
paschen242 (Å) |
float |
Paschen line index from local continuum at 8751.0 with band widths of 42.0 |
|
halpha_d02 (Å) |
float |
Width at 20% below the local continuum of Halpha line |
|
hbeta_d02 (Å) |
float |
Width at 20% below the local continuum of Hbeta line |
|
hgama_d02 (Å) |
float |
Width at 20% below the local continuum of Hgama line |
|
hdelta_d02 (Å) |
float |
Width at 20% below the local continuum of Hdelta line |
|
gaia_source_id |
char |
The "source_id" field of Gaia DR2 catalog |
|
gaia_g_mean_mag |
float |
The "phot_g_mean_mag" field of Gaia DR2 catalog |
In this sub-section, we introduce the LAMOST LRS M Type Star Catalog. We publish parameters for all 773,721 M type star spectra in this catalog, and 728,493 of them have surface gravities larger than or equal to 3.5 dex.
The fields of ‘teff’, ‘logg’, and ‘m_h’ in table 9 are effective temperatures, surface gravities, and metallicities for M type stars, which were determined by the minimum chi-squre estimation mentioned in Du B. et al. (2021) [13], and their errors of ‘teff_err’, ‘logg_err’, and ‘m_h_err’ were estimated with the method that LASP used. Here, the BT-Settl CIFIST2011 spectra[14-15] were used as templates to estimate‘teff’, ‘logg’, and‘m_h’. The ‘ewha’ and ‘ewha_err’ fields are Halpha line equivalent width and error. The fields of ‘tio1’, ‘tio1_err’, ‘tio2’, ‘tio2_err’, ‘tio3’, ‘tio3_err’, ‘tio4’, ‘tio4_err’, ‘tio5’, ‘tio5_err’, ‘cah1’, ‘cah1_err’, ‘cah2’, ‘cah2_err’, ‘cah3’, ‘cah3_err’, ‘caoh’, ‘caoh_err’, and ‘na’ are TiO, CaH, CaOH, and Na spectral line indices and their errors. Besides, a metallicity sensitive parameter of ‘zeta’, its error of ‘zeta_err’, and a magnetic activity flag of ‘type’ were also provided in this catalog. The value of ‘type’ includes 1 and 0, where 1 represents a M star has magnetic activity, and 0 means it does not have magnetic activity. Previous equivalent width, spectral line indices, ‘zeta’, ‘type’, and their errors were all given by the HAMMER software, and they were set to -9999 if they were unable to be determined. In addition, ‘z’ and ‘z_err’ are redshift and uncertainty separately, and they were estimated by the LAMOST 1D pipeline.
We provide two formats LAMOST LRS M Type Star Catalogs, which include a FITS table and a CSV table, can be available from the website http://www.lamost.org/dr8/v1.0/catalogue.
Table 9: LAMOST LRS M Type Star Catalog
|
Field (unit) |
Type |
Comment |
|
obsid |
long integer |
Unique Spectra ID |
|
designation |
varchar |
Target Designation |
|
obsdate |
char |
Target Observation Date |
|
lmjd |
char |
Local Modified Julian Day |
|
mjd |
char |
Modified Julian Day |
|
planid |
char |
Plan Name |
|
spid |
integer |
Spectrograph ID |
|
fiberid |
integer |
Fiber ID |
|
ra_obs (degree) |
float |
Fiber Pointing Right Ascension |
|
dec_obs (degree) |
float |
Fiber Pointing Declination |
|
snru |
float |
S/N of u filter |
|
snrg |
float |
S/N of g filter |
|
snrr |
float |
S/N of r filter |
|
snri |
float |
S/N of i filter |
|
snrz |
float |
S/N of z filter |
|
objtype |
varchar |
Object Type |
|
class |
varchar |
Spectra Type |
|
subclass |
varchar |
Stellar Sub-Class |
|
z |
float |
Redshift |
|
z_err |
float |
Redshift Uncertainty |
|
magtype |
varchar |
Target Magnitude Type |
|
mag1 (mag) |
float |
Associated Magnitude 1 |
|
mag2 (mag) |
float |
Associated Magnitude 2 |
|
mag3 (mag) |
float |
Associated Magnitude 3 |
|
mag4 (mag) |
float |
Associated Magnitude 4 |
|
mag5 (mag) |
float |
Associated Magnitude 5 |
|
mag6 (mag) |
float |
Associated Magnitude 6 |
|
mag7 (mag) |
float |
Associated Magnitude 7 |
|
tsource |
varchar |
Organization or person who submit input catalog |
|
fibertype |
varchar |
Fiber Type of target [Obj, Sky, F-std, Unused, PosErr, Dead] |
|
tfrom |
varchar |
Input catalog submitted by an organization or a person determined by the tsource |
|
tcomment |
varchar |
Target ID from SDSS, UCAC4, PANSTAR and other catalogues |
|
offsets |
Bool |
Whether there is a fiber offset during observation |
|
offsets_v (arcsec) |
float |
If the ‘offsets’ field is true, ‘offsets_v’ gives the offset distance from the target’s coordinator in input catalog |
|
ra (degree) |
float |
Right Ascension from input catalog |
|
dec (degree) |
float |
Declination from input catalog |
|
teff (K) |
float |
Effective Temperature obtained by the cross correlation method |
|
teff _err (K) |
float |
Effective Temperature Uncertainty estimated with the method LASP used |
|
logg (dex) |
float |
Surface Gravity obtained by the cross correlation method |
|
logg_err (dex) |
float |
Surface Gravity Uncertainty estimated with the method LASP used |
|
m_h (dex) |
float |
Metallicity obtained by the cross correlation method |
|
m_h_err (dex) |
float |
Metallicity Uncertainty estimated with the method LASP used |
|
ewha (Å) |
float |
Equivalent Width of Halpha line |
|
ewha_err (Å) |
float |
Equivalent Width Uncertainty of Halpha line |
|
tio5 (Å) |
float |
Spectral Indice of TiO5 |
|
cah2 (Å) |
float |
Spectral Indice of CaH2 |
|
cah3 (Å) |
float |
Spectral Indice of CaH3 |
|
tio1 (Å) |
float |
Spectral Indice of TiO1 |
|
tio2 (Å) |
float |
Spectral Indice of TiO2 |
|
tio3 (Å) |
float |
Spectral Indice of TiO3 |
|
tio4 (Å) |
float |
Spectral Indice of TiO4 |
|
cah1 (Å) |
float |
Spectral Indice of CaH1 |
|
caoh (Å) |
float |
Spectral Indice of CaOH |
|
tio5_err (Å) |
float |
Spectral Indice Error of TiO5 |
|
cah2_err (Å) |
float |
Spectral Indice Error of CaH2 |
|
cah3_err (Å) |
float |
Spectral Indice Error of CaH3 |
|
tio1_err (Å) |
float |
Spectral Indice Error of TiO1 |
|
tio2_err (Å) |
float |
Spectral Indice Error of TiO2 |
|
tio3_err (Å) |
float |
Spectral Indice Error of TiO3 |
|
tio4_err (Å) |
float |
Spectral Indice Error of TiO4 |
|
cah1_err (Å) |
float |
Spectral Indice Error of CaH1 |
|
caoh_err (Å) |
float |
Spectral Indice Error of CaOH |
|
zeta |
float |
Metallicity Sensitive Parameter |
|
zeta_err |
float |
Error of Metallicity Sensitive Parameter |
|
type |
integer |
Magnetic Activity |
|
na (Å) |
float |
Line Indice of Na Line |
|
gaia_source_id |
char |
The "source_id" field of Gaia DR2 catalog |
|
gaia_g_mean_mag |
float |
The "phot_g_mean_mag" field of Gaia DR2 catalog |
In this sub-section, we introduce the LAMOST LRS Multiple Epoch Catalog. In previous four LAMOST LRS catalogs, each row records parameters of a spectrum. In this catalog, each row represents a target with multiple observations, and there are 13 parameters provided for them.
In this data release, there are in total of 7,912,959 targets published. Using the “TOPCAT” tool, cross-match of these targets with Gaia DR2 were performed with a radius of 3 arc sec, and obtained 7,494,891 targets with both LAMOST DR8 and Gaia DR2 parameters. Among them, 2,012,297 targets with multiple observations were selected and included in this catalog. The equatorial coordinate, unique ID and G band magnitude of Gaia DR2 are provided in this catalog, and they are renamed as “ra”, “dec”, “gaia_source_id”, and “gaia_g_mean_mag”. Gaia equatorial coordinates were used to calculate the unique LAMOST source ID, i.e., “source_id”, which adopted the Hierarchical Triangular Mesh (HTM) algorithm [16] and the“HMpTy” package of Python.
The "obs_number", "obsid_list", "midmjm_list", "z_list", "teff_list", "logg_list", "feh_list", and "rv_list" fields provide the observation number, unique spectrum ID list, modified Julian minute list at the middle time of multiple exposures in one-night, red shift list , effective temperature list, surface gravity list, metallicity list and radial velocity list, respectively. Because these targets were observed at multiple nights, their “obs_number” are all greater than 1, and their unique spectrum ID, modified Julian minute of the middle time of multiple exposures, red shift, effective temperature, surface gravity, metallicity, and radial velocity of each observation are separated by the sign of "-” in the last seven fields of this catalog.
It should be noted that, you can use each obsid in the “obsid_list” field to cross-match with other LAMOST LRS catalogs.
Table 10: LAMOST LRS Multiple Epoch Catalog
|
Field (unit) |
Type |
Comment |
|
source_id |
char |
Unique LAMOST source ID |
|
ra |
float |
Right Ascension |
|
dec |
float |
Declination |
|
gaia_source_id |
float |
Gaia DR2 "source_id" field, which is a unique identifier for each Gaia DR2 target |
|
gaia_g_mean_mag |
float |
Gaia DR2 G mag, i.e., the "phot_g_mean_mag" field of Gaia DR2 catalog |
|
obs_number |
int |
Observation plan numbers for each target with multiple epoch observations |
|
obsid_list |
char |
Spectrum ID List |
|
midmjm_list |
char |
Modified Julian Minute List of the middle time of multiple exposure |
|
z_list |
char |
Red Shift List |
|
teff_list |
char |
Effective Temperature List |
|
logg_list |
char |
Surface Gravity List |
|
feh_list |
char |
Metallicity List |
|
rv_list |
char |
Radial Velocity List |
In this sub-section, we introduce the LAMOST LRS Observed Plate Information Catalog. Besides ‘obsdate’ and ‘planid’ fields also in other catalogs, we provide other seven basic information of all 5,207 published plates as described in table 10. The fields of ‘ra’ and ‘dec’ are right ascension and declination of center star of each plate, and the field ‘mag’ is the magnitude of center star. The field ‘seeing’ is the dome seeing of the first exposure, and the field ‘exptime’ is the total exposure time of n time exposures. Besides, the field ‘lmjm’ is the local modified Julian minute at the start time of each plate, and the ‘pid’ is the unique ID of each plate.
We provide a format of this table to download, which is available from the website http://www.lamost.org/dr8/v1.0/catalogue.
Table 11: LAMOST LRS Observed Plate Information Catalog
|
Field (unit) |
Type |
Comment |
|
pid |
integer |
Plate ID |
|
obsdate |
float |
Target Observation Date |
|
planid |
char |
Plan Name |
|
ra (degree) |
float |
Right Ascension of center star |
|
dec (degree) |
float |
Declination of center star |
|
mag (mag) |
float |
Magnitude of center star |
|
seeing |
float |
Seeing of the first exposure |
|
exptime (second) |
float |
The total exposure time of n time exposures |
|
lmjm |
Integer |
Local Modified Julian Minute at the start time of each plate |
In this sub-section, we introduce the LAMOST LRS Input Catalog. This catalog includes 27 fields for 13,954,016 targets. There are three fields which are not included in above five tables, and they are the ‘unitid’, ‘epoch’ and ‘tname’ fields respectively. The ‘unitid’ field is the ID of 4000 fiber units, and the ‘tname’ field provides unique ID of this catalog for each target. Besides, the value of the ‘epoch’ field is ‘J2000’.
We provide a format of this table to download, which is available from the website http://www.lamost.org/dr8/v1.0/catalogue.
Table 12: LAMOST LRS Input Catalog
|
Field (unit) |
Type |
Comment |
|
obsid |
long integer |
Unique Spectra ID |
|
obsdate |
float |
Target Observation Date |
|
planid |
char |
Plan Name |
|
spid |
integer |
Spectrograph ID |
|
fiberid |
integer |
Fiber ID |
|
unitid |
char |
ID of 4000 fiber unites |
|
ra_obs (degree) |
float |
Fiber Pointing Right Ascension |
|
dec_obs (degree) |
float |
Fiber Pointing Declination |
|
objtype |
varchar |
Object Type |
|
magtype |
varchar |
Target Magnitude Type |
|
mag1 (mag) |
float |
Associated Magnitude 1 |
|
mag2 (mag) |
float |
Associated Magnitude 2 |
|
mag3 (mag) |
float |
|
|
mag4 (mag) |
float |
Associated Magnitude 4 |
|
mag5 (mag) |
float |
Associated Magnitude 5 |
|
mag6 (mag) |
float |
Associated Magnitude 6 |
|
mag7 (mag) |
float |
Associated Magnitude 7 |
|
tsource |
varchar |
Organization or person who submit input catalog |
|
fibertype |
varchar |
Fiber Type of target [Obj, Sky, F-std, Unused, PosErr, Dead] |
|
tfrom |
varchar |
Input catalog submitted by an organization or a person determined by the objsourc |
|
tcomment |
varchar |
Target ID from SDSS, UCAC4, PANSTAR and other catalogues |
|
offsets |
bool |
Whether there is a fiber offset during observation |
|
offsets_v (arcsec) |
float |
If the ‘offsets’ field is true, ‘offsets_v’ gives the offset distance from the target’s coordinator in input catalog |
|
ra (degree) |
float |
Right Ascension from input catalog |
|
dec (degree) |
float |
Declination from input catalog |
|
epoch |
char |
J2000 |
|
tname |
char |
Unique ID for each targets in this catalog |
1. http://www.sdss.org/
2. Stoughton, Chris, Lupton, Robert H., Bernardi, Mariangela et al. 2002, Sloan Digital Sky Survey: Early Data Release, AJ, 123, 485.
3. Abazajian, Kevork, Adelman-McCarthy, Jennifer K., et al. 2003, The First Data Release of the Sloan Digital Sky Survey, AJ, 126,2081.
4. Abazajian, Kevork, Adelman-McCarthy, Jennifer K., et al. 2004, The Second Data Release of the Sloan Digital Sky Survey, AJ, 128, 502.
5. Zhang, Yueyang, Deng, Licai, Liu, Chao, et al. 2013, DA White Dwarfs Observed in the LAMOST Pilot Survey, AJ, 146, 34.
6. Cui, Xiangqun, Zhao, Yongheng, Chu, Yaoquan, et al. 2012, The Large Sky Area Multi-Object Spectroscopic Telescope (LAMOST), RAA, 12, 1197.
7. Zhao, Gang, Zhao, Yongheng, Chu, Yaoquan, et al. 2012, LAMOST spectral survey – An overview, RAA, 12, 723.
8. Luo, A-li, Zhang, Haotong, Zhao Yongheng, et al. 2012, Data release of the LAMOST pilot survey, RAA, 12, 1243.
9. Pence, W.D., Chiappetti, L., Page, C.G., et al. 2010, Definition of the Flexible Image Transport System (FITS), version 3.0, A&A, 524, 4
10. http://www.skyserver.org/htm/
11. http://adass.org/adass/proceedings/adass94/greisene.html
12. http://iraf.net/irafdocs/specwcs.php
13. Du Bing, Luo Ali, Zhang Shuo, et al. 2021, RAA, 21, 202
14. Allard, F., Homeier, D., & Freytag, B. 2011, Astronomical Society of the Pacific Conference Series, Vol. 448, Model Atmospheres From Very Low Mass Stars to Brown Dwarfs, ed. C. Johns-Krull, M. K. Browning, & A. A. West, 91
15. Allard, F., Homeier, D., Freytag, B., & Sharp, C. M. 2012, in EAS Publications Series, Vol. 57, EAS Publications Series, ed. C. Reylé, C. Charbonnel, & M. Schultheis, 3–43
16. Kunszt, Peter Z., Szalay, Alexander S., Thakar, Aniruddha. 2001, The Hierarchical Triangular Mesh, Mining the Sky: Proceedings of the MPA/ESO/MPE Workshop Held at Garching, Germany, July 31 - August 4, 2000, ESO ASTROPHYSICS SYMPOSIA. ISBN 3-540-42468-7. Edited by A.J. Banday, S. Zaroubi, and M. Bartelmann. Springer-Verlag, 2001, p. 631
