天体测量星表与巡天观测的进展

Current Progress on Astrometric Catalogs and Sky Surveys

该文简述了巡天观测和星表编制的历史和意义。介绍了天体测量星表与巡天观测的最新进展,如位置星表URAT、Pan-STARSS、LSST;自行星表LSPM、PM2000、BDKP;视差星表USNO、CTOPI、L和T型星的视差测定等。简略介绍了天体物理星表,其中包括测光星表GCPD、UBV、GSPC;光谱星表MSS、BDSS、SDSS和视向速度星表GCRV、CORALIE、RAVE。特别描述了恒星名至今仍在使用的20世纪初编制的Durchmusterung、Lowell、Henry Draper星表。描述了近年来普遍受到人们关注的联合星表编制的发展,如SKYMAP、距离太阳10pc内的近距星表RECONS、描述了局部天区的HDF、双星星表等。另外还介绍了其他波段的巡天观测,如射电的NVSS、FIRST;近红外的IRAS PSC和FSS;X波段的WGCAT星表等。最后,对今后开展巡天观测和编制星表提出了应注意的几个问题。

The history and significance of the sky survey and compiling catalogs are briefly described. The current progress on compiling astrometric catalogues and sky survey such as URAT, Pan-STARSS, LSST in stellar position; LSPM, PM2000, BDKP in proper motions; USNO program, CTOPI, program of the L and T stars in parallax are introduced. Meantime, the astrophysical catalogues including GCPD, UBV, GSP in photometry; MSS, BDSS, SDSS in spectrometry; GCRV, CORALIE, RAVE in radial velocity are briefly introduced too. Especially the catalogues of Durchmusterung, Lowell and Henry Draper published at the beginning of 20th century are indicated. The star numbers of these catalogues are still used now. Recently the combined catalogues such as SKYMAP, RECONS, HDF and catalogue for binary, to which one should pay more attention, are described. In addition, the catalogues in other wavebands such as NVSS, FIRST in radio, IRAS PSC and FSS in infrared and WGCAT in X band are described. Finally, some suggestions on the sky survey and compiling catalogues in the future are pointed out as follows. The success of the Hipparcos mission initiated the space astrometry at the millisecond level. The follow-up next-generation astrometric satellite, Gain will open an era of micro-arcsecond astrometry. Due to the limit of the telescope aperture and satellite＇s lifetime Gain catalogue including 1 billion celestial objects down to 20 mag will be published in 2021. Although the accuracy at the tens of micro-arcsecond will not attain from ground-based observations, these reach down to a depth of V=25 mag. The observational results are significant to study largescale properties of our Galaxy and other galaxies with statistical analysis. During development of new astrometry for 10 years the celestial objects and phenomena are being observed at multi-wavelengths. Therefore a combination of astrometric parameters and astrophysical parameters are highly desirable to studies of the Galaxy. Especially the positional and photometric measurements can not be carried out separately after CCD as a detector is used. For example, the determinations of the absolute proper motion, photometric and spectral measurements for HDF and SA57 were performed on a relatively small part of the sky. Even though the original scientific propose of the large projects, such as SDSS, RICONS etc. is to study on astrophysics, the combined catalogue including astrometric and astrophysical parameters will be produced, It is an only way to fully understand the Galactic structure and evolution by using both parameters. Because of the obscurity induced by interstellar dust and gas the bulge in the central region of the Galaxy is difficult to be accessible at optical wavelength on ground, i.e. the extinction is more serious in optical band than that in others as shown in Figure 2 （VW projection） of reference [15]. Although the Earth＇s atmosphere is more opaque in infrared than that in visual optical the Earth＇s atmosphere is relatively transparent at the ＇windows＇ of near-infrared wavelengths for the J, H, and K bands. Therefore the near infrared observations on ground are as important as the space-based observations. In order to attain the high accuracy in proper motions the catalogues are compiled by using current total observational data. For example, ARIHIP was compiled by using 100 catalogues on ground and Hipparcos. Catalogues in proper motion should be compiled by using AC or Carte du Ciel as observational data at the first epoch and current observations as that at the second epoch as well as the others at the intermediate epoch. The accuracy can attain 1.5 mas/a, such as proper motions in Tycho-2, PM2000 and so on. There is a limit to the number of trigonometric parallax measurements, especially for the distant and faint stars because two parallactic periods about 1.5 years are acquired, at minimum, for a unique determination of the trigonometric parallax. Although the photometric and spectroscopic distances can be used it should be calibrated by trigonometric parallax. The publication of LSPM catalog is actually very important for brown and white dwarf stars but no trigonometric parallax have been provided. The photometric distance of 13.9±3.5 pc is only used to study the orbit of LSR1826＋3014, the faintest and high proper motion red dwarf star （V=19.36 mag, proper motion 2.38″/a）. The parallaxes for 15 nearby brown dwarf stars were determined in Bordeaux parallax program in which the relation between photometric distance and trigonometric parallax is also given. Although the range of determination of distance has expanded from 100 pc to 5 kpc by using radio differential technique the perspective of determining distance with this method is on the base of the number of masters in the Galaxy. Therefore, determinations of trigonometric parallaxes for faint stars by using optical observations are more significant. In general, the lifetime of space telescope is about 3-5 years. Therefore the reliability of determining binary orbits, especially for those binaries with a long period, will increase by incorporating the ground- observational data into the space-based observational data. After the spectrophotometer with high resolution is installed on LAMOST the radial velocities of celestial bodies down to 20 mag will be given. The spectroscopic binary and extra-solar planets will be also studied.