Survey for Large Scale Structure in the Universe. Yaoquan Chu Center for Astrophysics University of Science and Technology of China

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1 Survey for Large Scale Structure in the Universe Yaoquan Chu Center for Astrophysics University of Science and Technology of China

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4 Observational cosmology, like most other physical sciences, is technology driven. With each new generation of telescope and with each improvement in the photographic process, astronomers probed further into the Universe.

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6 哈勃定律

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8 距离阶梯

9 反射望远镜 的类型 牛顿式 卡塞格林式 折轴式

10 Schmidt telescope

11 The first Palomar Observatory Sky Survey (POSS I) was carried out on the Oschin Schmidt Telescope in using 103aO and 103aF plates. POSS I continues to be one of the most frequently used astronomical resources; paper or glass copies of the plates are to be found in most of the world's observatories

12 The48 inch Oschin Schmidt Telescope at the Palomar Observatory

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14 Catalogue Zwicky Catalog of Galaxies: It contain galaxies from the Catalog of Galaxies and Clusters of Galaxies (CGCG), by Fritz Zwicky. Zwicky Catalog of Galaxy Cluster: It contains 9134 galaxy clusters from the Catalog of Galaxies and Clusters of Galaxies (CGCG), by Fritz Zwicky Abell catalog: The Abell catalog of rich clusters of galaxies is an all sky catalog of 4,073 rich galaxy clusters of nominal redshift z = 0.2. This catalog supplements a revision of George Ogden Abell s original Northern Survey of 1958, which had only 2,712 clusters,

15 Digitized Sky Survey The Catalogs and Surveys Group of the Space Telescope Science Institute has digitized the photographic Sky survey plates from the Palomar and UK Schmidt telescopes to produce the "Digitized Sky Survey" (DSS). Each plate covers 6.5 x 6.5 degrees of the sky and have been digitized using a modified PDS microdensitometer with a pixel size of either 25 or 15 microns (1.7 or 1.0 arcsec respectively). These images are 14000x14000 (0.4GB) or 23040x23040 pixels (1.1GB) in size and are difficult to access quickly.

16 The "Lick Observatory Sky Atlas" (Lick Observatory, 1965) is a set of plates for 166 fields of 18 by 18 degrees, covering the sky from the north pole down to 30 degrees of declination. "The Mount John University Observatory Photographic Sky Survey" (Doughty et al., 1972) covers 142 similar fields from 15 degrees of declination down to the south pole. In the region of overlap, the fields are the same for the two surveys. Fields 1 46 of the Mount John survey cover the part of the sky ( 45 degrees of declination to the south pole) not in the Lick survey; in a special limited edition published in 1972, this part is called the "Canterbury Sky Atlas" (Australia). The overlap between fields is 3 degrees. The plate scale is approximately 232 arc seconds per millimeter. The limiting magnitude is approximately 16. The Lick survey was originally done to obtain galaxy statistics (Shane and Wirtanen 1967).

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18 APM galaxy survey The APM Galaxy Survey contains positions, magnitudes, sizes and shapes for about 3 million galaxies selected from UKST survey plates which were scanned using the APM Facility.

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20 Those catalogs listed objects as they appeared projected onto the celestial sphere. The only indication of depth or distance came from brightness and/or size.

21 Redshift Surveys The prime goals of redshift surveys are to map the Universe in both physical and velocity space (particularly the deviation from uniform Hubble expansion) with a view to understanding the clustering and the dynamics. Mapping the universe in this way will provide information about how structured the Universe is now and at relatively modest redshifts.

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23 CfA surveys The first CfA redshift survey was undertaken by Huchra et al. (1983) who mapped some 2400 galaxies down to m 14.5 taken from the Zwicky catalog.

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25 CfA-II slice of de Lapparent et al. (1986), the Slice of the Universe. this contained redshifts of only around 2000 galaxies with a maximum recession velocity of km s

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27 The Las Campanas Redshift Survey (Shectman et al.,1996) had a similar geometry, six thin parallel slices ( ) with the depth about 750h 1Mpc (z 0.25). The survey team measured redshifts of about galaxies in these slices.

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29 IRAS redshift samples: PSCz the IRAS (Infrared Astronomical Satellite) Point Source Catalog (PSC) covers uniformly almost all of the sky. This catalog was used to select galaxies for redshift programs, which extended down to successively smaller flux limits: the 2 Jy survey of Strauss et al. (1992) with 2658 galaxies; the 1.2 Jy survey of Fisher et al. (1995) added 2663 galaxies; and the 0.6 Jy sparse sampled (1 in 6) QDOT survey of Lawrence et al. (1999) with 2387 galaxies. This culminated in the PSCz survey of some galaxies by Saunders et al. (2000), which includes practically all IRAS galaxies within the 0.6 Jy flux limit.

30 IRAS PSCz Survey

31 Multi Objects Spectrograph The scientific motivation for large scale redshift surveys has driven the development of efficient multi object spectroscopy (MOS) instrumentation Their high multiplex advantage is typically achieved by the placement of optical fibres in the focal plane of a telescope to relay light from multiple astronomical targets to a spectrograph.

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33 2dF galaxy redshift survey The 2dF multi fiber spectrograph on the 3.9m Anglo Australian Telescope is capable of observing up to 400 objects simultaneously over a field of view some 2 degrees in diameter, hence the name of the survey. The sample of galaxies targeted for having their redshifts measured consists of some 250,000 galaxies located in extended regions around the north and south Galactic poles. The source catalog is a revised APM survey. The galaxies in the survey go down to the magnitude bj = The median redshift of the sample is z = 0.11and redshifts extend to about z 0.3.

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36 英澳天文台 2dF 项目 : 磁扣式光纤定位系统 400 根光纤固定在微小的磁扣上, 由机器人手臂布置磁扣

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38 The 2dFGRS obtained spectra for objects, mainly galaxies, brighter than a nominal extinction corrected magnitude limit of b J = Reliable (quality>=3) redshifts were obtained for galaxies. The galaxies cover an area of approximately 1500 square degrees selected from the extended APM Galaxy Survey in three regions: an NGP strip, an SGP strip and random fields scattered around the SGP strip. The arrangement of survey fields is shown below.

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41 Sloan Digital Sky Survey (SDSS) the Sloan Digital Sky Survey (SDSS). The survey team has close to two hundred members from 13 institutions in U.S., Europe, and Japan, and uses a dedicated 2.5 m telescope. The initial photometric program is measuring the positions and luminosities of about 10 8 objects in π sterradians of the Northern sky, and the follow up spectroscopy is planned to give redshifts of about 10 6 galaxies and 10 5 quasars.

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49 美国 SDSS 项目 : 打孔式光纤定位系统, 完成所有的观测任务需要约 2000 块焦面板 每块焦面板上根据星表数据预先打有 640 个孔, 观测前将光纤植入孔中

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51 Mapping the Universe in galaxies redshift survey will provide information about how structured the Universe is now and at relatively modest redshifts. We need to understand how we extract information from these data and what is the selection effection in these survey.

52 Flux limited surveys and selection functions Such surveys include all galaxies in a given region of the sky exceeding an apparent magnitude cutoff. Thus only a small fraction of intrinsically very high luminosity galaxies are bright enough to be detected at large distances.

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54 For the statistical analyses of these surveys there are two possible approaches: 1. Extracting volume limited samples. 2. Using selection functions. This quantity is usually derived from the luminosity function, which is the number density of galaxies within a given range of luminosities.

55 Sky survey area

56 Sky coverage for the SDSS

57 Sampling

58 Redshift distortion velocity of any galaxy has two parts: V=V h +V p where V H h is the part which arises due to the expansion of the Universe and the peculiar velocity V p which is due to the inhomogeneities in the matter distribution.

59 Viewed in redshift space, which is the only three dimensional view we have, the universe looks anisotropic: the distribution of galaxies is elongated in what have been called fingers of god pointing toward us

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65 Galaxy traces the Mass? Using galaxies as tracers to map the LSS has the problem that the relation between the distribution of galaxies and the distribution of matter (which is believed to be mostly invisible i.e. dark matter) is not known. There are reasons to believe that the two distributions might be different.

66 Study the distribution of galaxies at Large Scale Our goals are to understand the origin of this structure, and to use it as a cosmological probe.

67 Can we test our basic assumptions? General Relativity, Cosmological Principle, The Big Bang, inflationary paradigm, Growth of structure by gravitational instability What were the initial conditions of the universe? How did structure form and evolve, on all scales? How did galaxies form? What physics is important for understanding structure formation?

68 Over the last few decades, astronomers have made observations that have addressed many of these questions and more. We now have a standard cosmological model that fits essentially all the data in a wonderfully unified way. However, this model includes components about which we know little: dark baryons, non baryonic dark matter, and dark energy.

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72 We measure the properties of a large sample of galaxies, we understand the way to analyze this through N body models, and on that basis we extract the information we want.

73 Quantify the structures in the distribution of galaxies. The deviations from a uniform distribution (fluctuations) are usually quantified using Δ g ( x) = N where Ng(x) is the number density of galaxies at the position x in the survey and N is the mean number density of galaxies. g ( x) N N

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76 Power Spectrum The Fourier transform of Δ g (x) ik x δ ( k) = e Δ ( x) dx g g is used to define the power spectrum P g ( k) = δ ( k) g 2

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78 Dark Energy

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90 The areas of sky covered by some present survey

91 the size and volume of existing redshift surveys.

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93 Two Micron All Sky Survey (2MASS)

94 X ray survey Galaxy clusters contain hot gas, which radiates X ray radiation due to bremsstrahlung

95 ROSAT, the Roentgen SATellite

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98 大天区面积多目标光谱光学天文望远镜 The Large Sky Area Multi-Object Fiber Spectroscopic Telescope Project (LAMOST)

99 Structure of LAMOST

100 Basic parameters of LAMOST 4.5m/6.3m Schmidt telescope The declination of observable sky area ranges from 10 to square degree of the FOV 4000 fibers Spectrum resolution: VPH (Volume Phase Holographic) Grating R=1000, 2000, 5000, 10000

101 cas1 Xinglong Station, NAOC the site Beijing: NAOC Project HQ Instruments & Software Science Nanjing: NIAOT (NAOC) Telescope Instruments Hefei: USTC Science

102 M A : 5.72mx4.4m reflecting corrector (24 sub mirrors) M B : 6.67mx6.05m spherical mirror (37 sub mirrors)

103 Active optics & supporting

104 Active optics Technical Challenges Both thin mirror and segmented mirror active optics in M A segmented mirror active optics in M B Positioning 4000 fibers

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106 Results of test at Nanjing Initial WF: PTV= µm RMS=2.641 µm d 80 =11.28 Before Act.Opt. performed Energy distribution corrected WF: PTV= µm RMS=0.152 µm d 80 =0.91". After Act.Opt. correction seeing (FWHM)=1.4

107 multi optical fiber positioning

108 Fiber positioning unit

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111 16 Spectrographs

112 LAMOST LRS Optical System Red (570~900nm) Blue (370~590nm) R5000/10000 R1000/2000 R5000/10000 R1000/2000

113 Resolution powers Grating Blue branch 5900 Å 5400Å Red branch Å Å R binning narrow 2000 slit narrow slit

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116 VPHG (Volume Phase Holographic Grating)

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118 E2V CCD203

119 First light of the small system On May The LAMOST small system (about 2m in diameter and have 250 firbers) got its first spectrum!

120 Sky 白天天光观测 5 月 25 日 15 时

121 6 月 5 日 18 时 天光光谱

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123 Component & Total Efficiency Efficieny telescope fiber Spectrograph CCD total Wavelength(A)

124 Efficiency R 波段 Observe data ( Sky):12.0% Theoretical value: 16.5% 中值为 1

125 Present status of LAMOST Optical system: Finished all the Sub mirrors Ma: 24 sub mirrors Mb: 37 sub mirrors

126 MA

127 MB

128 Full size (1.75m) focus plane

129 Spectrographs 15 Spectrographs have been setup 12 Spectrographs have been finished electronic mechanics adjustment Gratings just arrive

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131 CCD control system

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134 The Construction of full size LAMOST will be finished this year!

135 SDSS 2DF LAMOST Aperture 2.5m 4m 4m Field of View Number of Fiber Spectral resolution , Spectral ranges(å) Diameter of Fiber Mini Distance of Fibers 3 (180mu) 2.16 (140mu) 3 (320mu) (30 ) 40 S/N 4.5/pix (g=20.2) 13/pix (mean) 11/pix (20.5, 1.5h) Limited Magnitude i= ,20.2(q) r<17.7(g) bj (q) bj (g) B<20.5 Fiber Position Accuracy 0.5 Sqrt( ^2)~ (3 sigma)

136 3 Key Projects for LAMOST Extra galactic spectroscopic survey Galaxy and QSO redshift survey Stellar spectroscopic survey Structure of the Galaxy, and so on. Cross identification of multi waveband survey.

137 Welcome you to use LAMOST in the future Thank you!