We measure the filling factor, correlation function, and power spectrum of transmitted flux in a large sample of Lyα forest spectra, comprised of 30 Keck HIRES spectra and 23 Keck LRIS spectra. We infer the linear matter power spectrum P (k) from the flux power spectrum P F (k), using an improved version of the method of Croft et al. (1998) that accounts for the influence of redshift-space distortions, non-linearity, and thermal broadening on the shape of P F (k). The evolution of the shape and amplitude of P (k) over the redshift range of the sample (z ≈ 2−4) is consistent with the predictions of gravitational instability, implying that non-gravitational fluctuations do not make a large contribution to structure in the Lyα forest. Our fiducial measurement of P (k) comes from a subset of the data with 2.3 < z < 2.9, mean absorption redshift z = 2.72, and total path length ∆z ≈ 25. It has a dimensionless amplitude ∆ 2 (k p ) = 0.74 +0.20 −0.16 at wavenumber k p = 0.03(km s −1 ) −1 and is well described by a power-law of index ν = −2.43±0.06 or by a CDM-like power spectrum with shape parameter Γ ′ = 1.3 +0.7 −0.5 ×10 −3 (km s −1 ) −1 at z = 2.72 (all error bars 1σ). The correspondence to present day P (k) parameters depends on the adopted cosmology. For Ω m = 0.4, Ω Λ = 0.6, the best-fit shape parameter is Γ = 0.16h Mpc −1 , in good agreement with measurements from the 2dF Galaxy Redshift Survey, and the best-fit normalization is σ 8 = 0.82(Γ/0.15) −0.44 . Matching the observed cluster mass function and our measured ∆ 2 (k p ) in spatially flat cosmological models requires Ω m = 0.38 +0.10 −0.08 + 2.2(Γ − 0.15). Matching ∆ 2 (k p ) in COBEnormalized, flat CDM models with no tensor fluctuations requires Ω m = (0.29 ± 0.04)n −2.89 h −1.9 65 , and models that satisfy this constraint are also consistent with our measured logarithmic slope. The Lyα forest complements other observational probes of the linear matter power spectrum by constraining a regime of redshift and lengthscale not accessible by other means, and the consistency of these inferred parameters with independent estimates provides further support for a cosmological model based on inflation, cold dark matter, and vacuum energy.

The Echellette Spectrograph and Imager (ESI) is a multipurpose instrument which has been delivered by the Instrument Development Laboratory of Lick Observatory for use at the Cassegrain focus of the Keck II telescope. ESI saw first light on August 29, 1999. ESI is a multi-mode instrument that enables the observer to seamlessly switch between three modes during an observation. The three modes of ESI are: An R=13,000-echellette mode; Low-dispersion prismatic mode; Direct imaging mode. ESI contains a unique flexure compensation system which reduces the small instrument flexure to negligible proportions. Long-exposure images on the sky show FWHM spot diameters of 34 microns (0. ′′ 34) averaged over the entire field of view. These are the best non-AO images taken in the visible at Keck Observatory to date. Maximum efficiencies are measured to be 28% for the echellette mode and greater than 41% for low-dispersion prismatic mode including atmospheric, telescope and detector losses. In this paper we describe the instrument and its development. We also discuss the performance-testing and some observational results.

We have obtained 2640 CCD spectra with resolution ∼4Å in the region 7250-9000Å for 976 stars lying near the red giant branches in color-magnitude diagrams of 52 Galactic globular clusters. Radial velocities of ∼16 km s −1 accuracy per star determined from the spectra are combined with other criteria to assess quantitative membership probabilities. Measurements of the equivalent widths of the infrared 1 Visiting Astronomer, Las Campanas Observatory.-2calcium triplet lines yield a relative metal-abundance ranking with a precision that compares favorably to other techniques. Regressions between our system and those of others are derived. Our reduction procedures are discussed in detail, and the resultant catalog of derived velocities and equivalent widths is presented. The metal abundances derived from these data will be the subject of a future paper.provided numerous results of widespread interest, the original motivation of our program remains. In this paper we describe how we optimized our reduction of the spectral data ( §3) to provide radial velocities ( §4) and equivalent widths ( §5), compare our prescriptions and results with those of other workers ( §5.5), and present a catalog of the individual stellar results ( §7). Following the AD91 prescription, the cluster reduced equivalent widths, W ′ , are calculated ( §6). A companion paper discusses the calibration of our cluster W ′ values to [Fe/H] values, and the astrophysical implications of our results. ObservationsSpectra were obtained at the Las Campanas Observatory's 2.5m Dupont telescope equipped with the modular spectrograph and the Canon 85mm f/1.2 camera. A GG495 filter was used to block the second and higher spectral orders. The TI#2 detector (800 × 800 thinned CCD; readout noise = 11 e − pix −1 ; gain = 1.35 e − per ADU; scale = 0.85 ′′ pix −1 ) was used with an 831 l mm −1 (8000Å blaze) grating, which produced a dispersion of 2.19Å pix −1 and spectral coverage from 7250-9000Å. The 8 ′ × 1.25 ′′ slit provided an instrumental spectral resolution of ∼4Å.Observations were obtained on two 1989 runs: 1) April 13-20 and 2) July 13-21. Of the 52 clusters observed, 23 were observed during the first run only, 26 were observed during the second run only, and three were observed during both runs to check the consistency of our results. In each cluster, spectra were obtained for 10 to 20 stars selected from published color-magnitude diagrams (CMDs) to lie on the red giant branch (RGB) and, if proper motion data were available, to be likely proper-motion members. Probable asymptotic branch (AGB) stars were avoided, as were horizontal branch (HB) stars, and known variable stars near the RGB tip. Slit positions were chosen to contain at least two stars per spectrograph rotation.Each star was observed two or three times consecutively, with an Fe-Ar arc taken before and after each sequence for the wavelength calibration. Occasionally the same star was observed on different nights, or with a different slit orientation, to check for systematic effects in our results. ...

BV(Rl) KC light curves are presented for 27 type la supemovae discovered during the course of the Calán/Tololo Survey and for two other SNe la observed during the same period. Estimates of the maximum hght magnitudes in the B, V, and I bands and the initial decline rate parameter Am 15 (B) are also given.

The Automated Planet Finder (APF) is a facility purpose-built for the discovery and characterization of extrasolar planets through high cadence Doppler velocimetry of the reflex barycentric accelerations of their host stars. Located atop Mt. Hamilton, the APF facility consists of a 2.4-m telescope and its Levy Spectrometer, an optical echelle spectrometer optimized for precision Doppler velocimetry. APF features a fixed format spectral range from 374 nm -970 nm, and delivers a "Throughput" (resolution * slit width product) of 114,000 arc-seconds, with spectral resolutions up to 150,000.Overall system efficiency (fraction of photons incident on the primary mirror that are detected by the science CCD) on blaze at 560 nm in planet-hunting mode is 15%. Firstlight tests on the RV standard stars HD 185144 and HD 9407 demonstrate sub-m s −1 precision (RMS per observation) held over a 3-month period. This paper reviews the basic features of the telescope, dome, and spectrometer, and gives a brief summary of first-light performance.

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We have undertaken an imaging survey of low surface brightness dwarf galaxies in nearby groups with the main goal of studying the faint-end of the galaxy luminosity function at z ∼ 0. Here we describe the results on the search for LSB dwarf galaxies in two compact groups: HCG44 and HCG68. Our study explores the surface brightness, sizes, magnitudes and colours of these candidate dwarf galaxies. The selection criteria were their central surface brightness, scale factors and diameters at the limiting isophote of 26 R mag/" 2 . We estimate the faint end of the luminosity function of galaxies through Monte Carlo simulations. The observed magnitude distribution of the candidate dwarf galaxies in the groups (down to MR ∼ −13) is compatible with a Schechter function with a slope α ∼ − 1.2. † Present address: IAG-USP,