The Solution of Elliptic Difference Equations by Semi-Explicit Iterative Techniques

In [8], the author discusses an iterative scheme for solving a difference analogue for the elliptic differential equation ∇•α∇u = f on two-dimensional rectangular regions with Dirichlet boundary conditions. It is shown there that a semi-explicit technique involving the inversion only of the Peaceman-Rachford [10] alternating-direction operators for the Laplacian gives convergence in O(h^(-2) log h^(-1)) operations

Volume phase holographic gratings for the Subaru Prime Focus Spectrograph: performance measurements of the prototype grating set

The Prime Focus Spectrograph (PFS) is a major instrument under development for the 8.2 m Subaru telescope. Four identical spectrograph modules are located in a room above one Nasmyth focus. A 55~m fiber optic cable feeds light to the spectrographs from a robotic positioner at the prime focus, behind the wide-field corrector developed for Hyper Suprime-Cam. The positioner contains 2400 fibers and covers a 1.3~degree hexagonal field of view. The spectrograph optical design consists of a Schmidt collimator, two dichroic beamsplitters to split the light into three channels, and for each channel a volume phase holographic (VPH) grating and a dual-corrector, modified Schmidt reimaging camera. This design provides a 275~mm collimated beam diameter, wide simultaneous wavelength coverage from 380~nm to 1.26~\textmu m, and good imaging performance at the fast f/1.05 focal ratio required from the cameras to avoid oversampling the fibers. The three channels are designated as the blue, red, and near-infrared (NIR), and cover the bandpasses 380--650~nm (blue), 630--970~nm (red), and 0.94--1.26~\textmu m (NIR). A mosaic of two Hamamatsu 2k$\times$4k, 15~\textmu m pixel CCDs records the spectra in the blue and red channels, while the NIR channel employs a 4k$\times$4k, substrate-removed HAWAII-4RG array from Teledyne, with 15~\textmu m pixels and a 1.7~\textmu m wavelength cutoff. VPH gratings were an obvious choice for PFS and a set of three prototype VPH gratings (one each of the blue, red, and NIR designs) was ordered and has been recently delivered. In this paper we present the design and specifications for the PFS gratings, the plan and setups used for testing both the prototype and final gratings, and results from recent optical testing of the prototype grating set.Comment: 18 pages, 20 figures SPIE Astronomical Telescopes and Instrumentation 2014, Montrea

Evolutionary Synthesis Of Stellar Population In Elliptical Galaxies .1. Ingredients, Broad-Band Colors, And Infrared Features

NSF MPS 73-04673 A01, GP-40482, GP-3143, MPS 75-01398Astronom

Designing a Small Language Laboratory for the 1980's

When Rockford College needed a new language laboratory, it was necessary firstto decide how the lab was to be used and then how it was to operate. These decisionsdetermined the choice of equipment

A new method to simulate vertical and horizontal structure in galactic disks

We have modified the particles in an N-body treecode to have different softening lengths in the horizontal and vertical directions. This allows us to simultaneously have thin enough particles to resolve the vertical structure in galactic disks, and horizontally large enough particles to suppress the vertical heating due to two-body effects

Optical Design of the SuMIRe PFS Spectrograph

The SuMIRe Prime Focus Spectrograph (PFS), developed for the 8-m class SUBARU telescope, will consist of four identical spectrographs, each receiving 600 fibers from a 2394 fiber robotic positioner at the telescope prime focus. Each spectrograph includes three spectral channels to cover the wavelength range 0.38-1.26 um with a resolving power ranging between 2000 and 4000. A medium resolution mode is also implemented to reach a resolving power of 5000 at 0.8 um. Each spectrograph is made of 4 optical units: the entrance unit which produces three corrected collimated beams and three camera units (one per spectral channel). The beam is split by using two large dichroics; and in each arm, the light is dispersed by large VPH gratings. The proposed optical design was optimized to achieve the requested image quality while simplifying the manufacturing of the whole optical system. The camera design consists in an innovative Schmidt camera observing a large field-of-view (10 degrees) with a very fast beam. To achieve such a performance, the classical spherical mirror is replaced by a catadioptric mirror (i.e meniscus lens with a reflective surface on the rear side of the glass, like a Mangin mirror). This article focuses on the optical architecture of the PFS spectrograph and the perfornance achieved. We will first described the global optical design of the spectrograph. Then, we will focus on the Mangin-Schmidt camera design. The analysis of the optical performance and the results obtained are presented in the last section.Comment: 8 pages - submitted at SPIE Astronomical Telescopes - Instrumentation 2014 - Montrea

The Shape of Space

There is only one universe, doing--as far as we can tell--rather simple things. But do we understand those things

A Catalog of Digital Images of 113 Nearby Galaxies

We present a digital catalog of images of 113 galaxies in this paper. These galaxies are all nearby, bright, large and well resolved. All images were recorded with charge coupled devices (CCDs) at the Palomar Observatory with the 1.5 meter telescope and at the Lowell Observatory with the 1.1 meter telescope. At Palomar we used the Thuan--Gunn g, r and i photometric bands to take 3 images each of 31 spiral galaxies; at Lowell we used the B_J and R bands (2 images per galaxy) of the photometric system by Gullixson et al. (1995) to observe 82 spirals and ellipticals. The galaxies were selected to span the Hubble classification classes. All data are photometrically calibrated with foreground stars removed. Important data on these galaxies published in the "Third Reference Catalog of Bright Galaxies" (RC3) are recorded in the FITS file headers. All files are available through anonymous FTP from ftp://astro.princeton.edu/, through WWW at http://astro.princeton.edu/~frei/galaxy_catalog.html, and Princeton University Press will soon publish the data on CD-ROM.Comment: uuencoded compressed tar archive of postscript files (paper + 2 tables + 7 figures) Accepted for publication in the Astronomical Journa

Optical Cluster-Finding with An Adaptive Matched-Filter Technique: Algorithm and Comparison with Simulations

We present a modified adaptive matched filter algorithm designed to identify clusters of galaxies in wide-field imaging surveys such as the Sloan Digital Sky Survey. The cluster-finding technique is fully adaptive to imaging surveys with spectroscopic coverage, multicolor photometric redshifts, no redshift information at all, and any combination of these within one survey. It works with high efficiency in multi-band imaging surveys where photometric redshifts can be estimated with well-understood error distributions. Tests of the algorithm on realistic mock SDSS catalogs suggest that the detected sample is ~85% complete and over 90% pure for clusters with masses above 1.0*10^{14} h^{-1} M_solar and redshifts up to z=0.45. The errors of estimated cluster redshifts from maximum likelihood method are shown to be small (typically less that 0.01) over the whole redshift range with photometric redshift errors typical of those found in the Sloan survey. Inside the spherical radius corresponding to a galaxy overdensity of Delta=200, we find the derived cluster richness Lambda_{200} a roughly linear indicator of its virial mass M_{200}, which well recovers the relation between total luminosity and cluster mass of the input simulation.Comment: Accepted to ApJ. 13 pages, 9 figure