After analyzing the observed data, the scientific committee of LAMOST telescope decided to use slit with 2/3 fixed width for LAMOST survey (hereafter, 2/3slit). LAMOST technicians have measured the spectra resolution for different spectrograph and optical fibers under the condition of 1/2 slit , 2/3 slit and full open slit. Using 2/3 slit, we can not only improve the efficiency, but also can combine the scientific goals of two working group, which can also improve the usage efficiency of the telescope.
In the summer of 2011, LAMOST technicians have updated the spectrograph slit. After carefully designing and installing, by the end of August, the installation and test of fixed slit on 16 spectrographs have been finished.
The length of 2/3 slit is 144mm, width is 0.22 mm. The technicians have made checking and modification with many times to guarantee straightness of slit to be better than 5um. Many works have been done to guarantee that each fiber can point to the middle region of slit.
(the figure is the 2/3 slit)
After analyzing the observed data, the scientific committee of LAMOST telescope decided to use slit with 2/3 fixed width for LAMOST survey (hereafter, 2/3slit). LAMOST technicians have measured the spectra resolution for different spectrograph and optical fibers under the condition of 1/2 slit , 2/3 slit and full open slit. Using 2/3 slit, we can not only improve the efficiency, but also can combine the scientific goals of two working group, which can also improve the usage efficiency of the telescope.
In the summer of 2011, LAMOST technicians have updated the spectrograph slit. After carefully designing and installing, by the end of August, the installation and test of fixed slit on 16 spectrographs have been finished.
The length of 2/3 slit is 144mm, width is 0.22 mm. The technicians have made checking and modification with many times to guarantee straightness of slit to be better than 5um. Many works have been done to guarantee that each fiber can point to the middle region of slit.
(the figure is the 2/3 slit)
According to the requirement of LAMOST scientific committee, the data of LAMOST should be released after one month of observation. At 24th December 2011, the survey and data departments with help of information center of NAOC released the data observed at 24th October 2011. By the end of 2011, 230,000 spectra distributed in 117 sky area have been released. The distributed system are mounted on the internet cooperative work platform, which have been open for accessing (http://lamost.escience.cn/dct/page). People who are interesting in the spectra can apply to get permission for downloading and using the distributed data. Detailed registering, please refer to web page.
After one month preparation, the survey and data department have checked all the spectra by eye, and compared it with 1D PIPELINE. Then the parameters, final_class, final_subclass, and final_z etc, have been released.
figure1 is the Examples of observed sky area,figure 2 is the data retrieval result and spectrum.
After analyzing the astrophysical front, the scientific committee of LAMOST telescope has determined the task of the first stage of spectra survey – the survey area and scientific object for the pilot survey. The reasonable observing plan have been designed with the help of scientists in the Center for Operation and Development of LAMOST Telescope. The software system of LAMOST have been tested and evaluated for many times. Especially, the meeting of international evaluation for LAMOST software was hold successfully in December 2010. The experts draw the consensus conclusion that software of LAMOST can fulfill the requirement of spectra survey based on the observing plan, observing control, data reduce. On hardware, the optical fiber positioning has made breakthrough progress that among 4000 fibers the accuracy of 90% fibers is better than 1 arc-second. After finely tuned, the stability of spectrograph has been improved. The overall efficiency of spectrographs have been improved aftercoating. According to the requirement of scientific survey, the new installed 2/3 slit is used to improve resolution. The optical efficiency is guaranteed after coating all the sub-mirrors of MA. The Center for Operation and Development of LAMOST Telescope have improved the organization, regulated the operation of telescope and rules. LAMOST get ready for massive survey. The pilot survey formally began at 23rd October, 2011.
The Andromeda galaxy (M31) is the nearest spiral galaxy in the Local Group. During the 2009 commissioning phase of the LAMOST Telescope (GSJT ), two M31 testing fields that are centered close to the optical nucleus of the galaxy and in the northeastern halo, respectively, are observed. It is for the first time that the optical spectra covering the whole galactic bulge and disk are observed for M31. These spectra are flux-calibrated by the photometric data of 15 intermediate bands in the BATC survey. As a result, there are 59 usable spectra in total. They are used to study the kinematic properties and stellar populations of this galaxy. Via fitting the spectra with the model spectra of the stellar population synthesis method, the radial velocities, velocity dispersions, ages, metallicities and reddening values are estimated and the two-dimensional distributions of these parameters are shown. This work not only utilize-for the first time-the optical spectra to obtain the global velocity field, velocity dispersion, age, metallicity and reddening distributions in an FOV of one degree, but also-for the first time-use the observed data of the GSJT to study the nearby galaxies.
Thus, it paves the way for the astrophysical researches by using the GSJT spectra.
Figure1.Two-dimensional distributions of different parameters derived by STARLIGHT.From left to right and top to bottom, they are the radial velocity, velocity dispersion, age, metallicity and intrinsic reddening in E(B − V ) in their turn. The crossing symbol in each panel is the optical center (α=10.685 ◦ and δ=41.269 ◦ ). In the first panel, two perpendicular dashed lines are the optical major and minor axes. The outer arcs are the clipped elliptical enclosure of the Andromeda’s disk. Here again, we adopt the length of the major axis of about 1.59 ◦ , the disc inclination angle of 78 ◦ and position angle of the major axis of 38 ◦ . Contours are drawn in equally spaced levels within the age ranges as shown in the color bars
Research work which related with Galaxy needs to know massive stellar mass, age, abundance, spatial velocity and distance etc. All of these data is hard to be derived through direct observations. In order to get these information, normally first we determine some valuable fundamental stellar atmospheric parameters through analysis of the observed stellar spectra. Then with these parameters, other stellar physical parameters could be predicted . To better understand the Galactic origin, structure and evolution, we need statistically analysis large data sample of stars. LAMOST will produce unprecedented massive observing data, and these resources are very important for helping us understand our Milky Way’s structure, origin and evolution etc.
By adopting the ULySS package, the authors automatically determined LAMOST commissioning observed stellar spectra’s atmospheric parameters. They have tested the effect of different resolutions and signal-to-noise ratios (SNR) on the measurement of the stellar atmospheric parameters (effective temperature Teff, surface gravity log g, and metallicity [Fe/H]). They show that ULySS is reliable for determining these parameters with medium-resolution spectra (R~2000) like LAMOST commissioning observations. Adopting spectra observed in one LAMOST commissioning field on 2010 February 13 (most of the observations are field stars around M67), they selected 771 stars which are better quality spectra and homogeneous sample, then they applied the ULySS method to measure the parameters of these sample stars. The results were compared with the SDSS/SEGUE Stellar Parameter Pipeline (SSPP), and they derived precisions of 167 K, 0.34 dex, and 0.16 dex for Teff, log g and [Fe/H] respectively. The resulting precision is relatively satisfied for LAMOST kind stellar spectra. This work gives us an early insight on the scientific capability of the LAMOST for the research work related to out Milky Way. Furthermore, 120 of these stars are selected to construct the primary stellar spectral template library (Version 1.0) of LAMOST, and will be deployed as basic ingredients for the LAMOST automated parameterization pipeline. Since the LAMOST commissioning period is still ongoing, they will collect more stellar spectra and enlarge this template library including all stellar evolution stages and with wider coverage in the atmospheric parameter space