Reduction Guide for Xinglong HRS

Introduction to Instrument

Since 2009, A fiber-fed High Resolution Spectrograph (HRS) was attached on the Cassegrain focus of the 2.16m telescope in Xinglong Observatory of National Astronomical Observatories, Chinese Academy of Sciences (CAS). The spectrograph has a resolving power (R = λ/Δλ) of ~49,800 at the slit width of 0.19 mm, covering the wavelength range of 365 ~ 1000 nm. The CCD detector is a back-illuminated E2V CCD 203-82 chip with 4096 × 4096 pixels and the pixel size of 12.0 μm. For more information, see Fan et al. 2016 [1].

Parameter Value
Wavelength Coverage 3,650 - 10,000 Å
Resolving Power 32,000 - 106,000
Fiber Diameter 2”.4/1”.6
CCD Detector E2V 4k × 4k back illuminated, 12 μm/pixel
Radial Velocity Precision ±6 m/s (with an I2 cell)

The CCD gain and readout noise of four gates at different readout speeds are summarized as below:

Readout Speed Gain Mode Gain (e−/ADU) Read Out Noise (e−/pixel)
L0 L1 R0 R1 L0 L1 R0 R1
Slow 0 2.369 ± 0.146 2.309 ± 0.067 2.928 ± 0.314 2.358 ± 0.102 3.89 ± 0.31 3.86 ± 0.32 6.88 ± 2.26 4.03 ± 0.27
1 1.005 ± 0.023 1.022 ± 0.020 1.074 ± 0.031 1.033 ± 0.019 2.84 ± 0.13 2.84 ± 0.15 3.38 ± 0.38 2.90 ± 0.11
2 0.430 ± 0.004 0.447 ± 0.007 0.448 ± 0.004 0.448 ± 0.006 2.47 ± 0.07 2.54 ± 0.06 2.72 ± 0.08 2.58 ± 0.12
Medium 0 4.954 ± 0.566 4.590 ± 0.196 8.381 ± 0.000 5.096 ± 0.622 6.89 ± 1.03 6.38 ± 0.55 15.34 ± 5.20 7.19 ± 1.13
1 2.301 ± 0.163 2.189 ± 0.065 2.847 ± 0.303 2.303 ± 0.137 4.60 ± 0.46 4.29 ± 0.21 6.58 ± 1.18 4.61 ± 0.37
2 0.863 ± 0.009 0.896 ± 0.007 0.937 ± 0.003 0.891 ± 0.009 3.20 ± 0.12 3.22 ± 0.07 3.69 ± 0.11 3.29 ± 0.09
Fast 0 2.406 ± 0.140 2.484 ± 0.090 2.866 ± 0.192 2.521 ± 0.186 9.31 ± 0.74 8.52 ± 0.70 19.37 ± 9.26 9.02 ± 0.77
1 1.010 ± 0.021 1.057 ± 0.020 1.075 ± 0.039 1.027 ± 0.029 7.88 ± 0.40 7.33 ± 0.44 16.69 ± 6.92 7.34 ± 0.52
2 0.431 ± 0.008 0.451 ± 0.018 0.463 ± 0.004 0.448 ± 0.004 6.84 ± 0.40 6.27 ± 0.41 8.28 ± 0.26 6.62 ± 0.38

Preparing Data & Config File

The first step is to create a new working directory in a place where the user has full read/write permissions. All the steps performed by GAMSE will be done in this directory.

Then, a text file containing the necessary information is required to tell GAMSE which instrument the data is obtained with, and the path to raw data. The name of the text file is arbitrary, but the suffix must be .cfg. The user must make sure there is only one .cfg file in the working directory.

Generating the Observing Log

The following command scans the raw images and generate an observing log file with name of YYYY-MM-DD.obslog, where YYYY-MM-DD is the date of the first FITS image in the data folder.

$ gamse list

If the file name already exists, YYYY-MM-DD.1.obslog, YYYY-MM-DD.2.obslog … will be used as substituions.

At this step, the program also reads a file obsinfo.txt if it exists. This file contains addtional infomations, such as whether an iodine cell is used, and the accurate starting time of an exposure, since these parameters are not included in the FITS files of HRS on the Xinglong 2.16m telescope. An example of obsinfo.txt is shown below:

frameid  object   i2cell      obsdate
  int      str     bool         time
-------- -------- ------ -------------------
01-10    Flat
12-21    Flat
22       I2
23       thar
24       thar
25       HD195820 True   2014-11-03T18:25:27
26       HD195820 True   2014-11-03T19:00:44
27       HD210460 False  2014-11-03T19:28:04
... ...

comparing to the ‘ascii.fixed_width_two_line’ format in astropy.table module, the second row contains the data types of table columns.

Starting Data Reduction

After preparation of the configuration file *.cfg and the observing log file *.obslog, one can start the data reduction by running:

gamse reduce

The following entries are accepted in the [reduce] section in the configuration file:

Accepted entries in reduce section
Key Type Default Value Description
midproc str midproc Path to the mid-process folder.
report str report Path to the 1d spectra folder.
onedspec str onedspec Path to the report folder.
mode str normal Reduction mode. Available modes are “normal”, “debug” and “fast”.
oned_suffix str ods Suffix of the 1d spectra files.
fig_format str png Format of figures.

Overscan Correction

Perpare the Configuration File

The pipeline accepts the following options in the config file:

Accepted options in config file
Section Option Type Default Value Description
data telescope str Xinglong216 Name of the telescope (Fixed).
data instrument str HRS Name of the instrument (Fixed).
data rawdata str rawdata Path to the rawdata.
bias cosmic_clip float 10 Upper clipping value for removing the cosmic-rays.
bias maxiter int 5 Maximum iteration numbers.
bias smooth_method str   Method of smoothing the bias data.
bias smooth_sigma int   Sigma of Gaussian smoothing core.
bias smooth_mode str   Mode of Gaussian smoothing core.
trace scan_step int   Steps of pixels used to scan along the main dispersion direction.
trace minimum float   Minimum value to filter the input image.
trace seperation float   Estimated order seperations (in pixel) at y = 0 along the cross-dispersion.
trace sep_der float   Estimated first derivative of seperations per 1000 pixels along the y axis.
trace filling float   Fraction of detected pixels to total step of scanning.
trace display bool   Display a figure on screen if yes.
trace degree int   Degree of polynomial used to describe the positions of orders.
background scan_step int   Steps of pixels used to scan along the main dispersion direction.
background xorder int   Degree of 2D polynomial along x-axis (dispersion direction).
background yorder int   Degree of 2D polynomial along y-axis (cross-dispersion direction).
background maxiter int   Maximum number of iteration of 2D polynomial fitting.
background upper_clip float   Upper sigma clipping threshold.
background lower_clip float   Lower sigma clipping threshold.
background extend bool   Extend the grid to the whole image if True.
background display bool   Display a graphics if yes.

APIs

make_config
make_obslog
reduce_rawdata
common.get_ccd_geometry
common.get_region_lst
common.get_sci_region
common.get_ovr_region
common.correct_overscan
common.get_bias
common.get_mask
common.get_badpixel_mask
common.fix_cr
common.select_calib_from_database
common.TraceFigure
reduce_singlefiber.reduce_singlefiber
reduce_doublefiber.reduce_doublefiber
flat.smooth_aperpar_A
flat.smooth_aperpar_k
flat.smooth_aperpar_c
flat.smooth_aperpar_bkg