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August 2006

TELESCOPES and DETECTORS. LSST - A Plan for Photo-z Calibrations. August 2006 Bogdan Popescu. OVERVIEW 1.

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August 2006

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  1. TELESCOPES and DETECTORS LSST - A Plan for Photo-z Calibrations August 2006 Bogdan Popescu

  2. OVERVIEW 1 To complete a spectroscopic calibration program there would be several steps along the way: Step 1) A group of experts analyzes a combination of archived data in regions of the sky where a combination of deep spectroscopy and both HST /ACS and Spitzer near-IR imaging are available; e.g. the DEEP2, GOODS, and COSMOS fields. In combination with existing ground-based imaging, these datasets give photometry in effectively ~10 broadband filters calibrated with spectroscopy. The combination will greatly refine evolution and selection function models. This step is already happening. Step 2) These deep fields would be further enhanced via deep imaging in new bands, covering the far UV to IR. The superphotometric bands/facilities should include GALEX (FUV + NUV for isolated galaxies), HST ACS (I,g), Subaru (deeper BVgrizy), CFHT (u + JHK), and possibly Spitzer (3 shortest wavelength IR bands for isolated galaxies). This deep super-photo-z system then requires spectroscopic calibration. Step 3) The first two steps are likely to reveal important holes in our understanding of the models. This knowledge will be used to inform a dedicated effort using of order 50 nights of VLT time and also of order 50 nights of Keck and/or Gemini time to undertake the necessary spectroscopy to constrain the models well. This would produce about 20,000 spectroscopic calibrations out to z=3 for the super photo-z training set. It is possible that fewer calibrators could be used. The key would be to understand the selection function. For example, DEIMOS can go to R = 26 in about 40 hours. Beyond z = 1.4 one would probably want to use a blue sensitive spectrograph, or a near-IR spectrograph for emission line galaxies around z = 2. For z >~ 2.5 or so one would be back to DEIMOS for the Ly-a line. If a calibration precision of 0.001(1+z) were required, four times this investment would be needed. We would select an initial sample and then iterate the next selection based on how well we do. Spectroscopic facilities which could be used include Keck/DEIMOS, VLT/VIMOS, Gemini/GMOS, Magellan/COSMOS, and Subaru IRSPEC. Step 4) Once these steps are complete, we would have some understanding of the remaining systematics leading to confidence in the redshifts of ~20,000 galaxies in these selected fields in order to calibrate the local super-photo-z system. The ~1 million galaxies with super-photo-z in each of these training fields then would be used to calibrate the 6-band photo-z's for programs like LSST. The precision of bias calibration and the variance will vary with redshift, being worst in the “optical desert.” However, these error estimates will be known both as a function of type and redshift, and that can be used for more precise extraction of cosmological parameters from WL and BAO analyses. Furthermore, galaxies in portions of color space which are poorly constrained (or fail to ever yield redshifts) could be excluded from WL or BAO analyses with minimal impact. 1 http://www.lsst.org/Science/Phot-z-plan.pdf August 2006 Bogdan Popescu

  3. HST / ACS 2 The Advanced Camera for Surveys (ACS) is a third-generation Hubble Space Telescope (HST) instrument. ACS was installed by space shuttle Columbia astronauts Grunsfeld, Currie, Newman, Linnehan and Massimino on STS-109 during HST servicing mission 3B. The development of ACS is a collaborative effort between: * Johns Hopkins University * Goddard Space Flight Center * Ball Aerospace * Space Telescope Science Institute The Advanced Camera for Surveys (ACS) includes three channels: * a Wide Field Channel (WFC), with a field of view of 202x202 square arcsec covering the range from 3700 to 11000 Å and a plate-scale of 0.05 arcsec/pixel; * a High Resolution Channel (HRC), with a field of view of 26x29 square arcsec covering the range from 2000 to 11000 Å and a plate-scale of 0.027 arcsec/pixel; * a Solar Blind Channel (SBC), with a field of view of 31x35 square arcsec, spanning the range from 1150 to 1700 Å and a plate-scale of 0.032 arcsec/pixel. 2 http://www.stsci.edu/hst/acs/ August 2006 Bogdan Popescu

  4. Spitzer Space telescope 3 The Spitzer Space Telescope (formerly SIRTF, the Space Infrared Telescope Facility) was launched into space by a Delta rocket from Cape Canaveral, Florida on 25 August 2003. During its 2.5-year mission, Spitzer will obtain images and spectra by detecting the infrared energy, or heat, radiated by objects in space between wavelengths of 3 and 180 microns (1 micron is one-millionth of a meter). Most of this infrared radiation is blocked by the Earth's atmosphere and cannot be observed from the ground. Consisting of a 0.85-meter telescope and three cryogenically-cooled science instruments, Spitzer is the largest infrared telescope ever launched into space. Its highly sensitive instruments give us a unique view of the Universe and allow us to peer into regions of space which are hidden from optical telescopes. Many areas of space are filled with vast, dense clouds of gas and dust which block our view. Infrared light, however can penetrate these clouds, allowing us to peer into regions of star formation, the centers of galaxies, and into newly forming planetary systems. Infrared also brings us information about the cooler objects in space, such as smaller stars which are too dim to be detected by their visible light, extrasolar planets, and giant molecular clouds. Also, many molecules in space, including organic molecules, have their unique signatures in the infrared. 3 http://www.spitzer.caltech.edu/ August 2006 Bogdan Popescu

  5. Spitzer Space telescope 3 Because infrared is primarily heat radiation, the telescope must be cooled to near absolute zero (-459 degrees Fahrenheit or -273 degrees Celsius) so that it can observe infrared signals from space without interference from the telescope's own heat. Also, the telescope must be protected from the heat of the Sun and the infrared radiation put out by the Earth. To do this, Spitzer carries a solar shield and will be launched into an Earth-trailing solar orbit. This unique orbit places Spitzer far enough away from the Earth to allow the telescope to cool rapidy without having to carry large amounts of cryogen (coolant). This innovative approach has significantly reduced the cost of the mission. Spitzer will be the final mission in NASA's Great Observatories Program - a family of four orbiting observatories, each observing the Universe in a different kind of light (visible, gamma rays, X-rays, and infrared). Other missions in this program include the Hubble Space Telescope (HST), Compton Gamma-Ray Observatory (CGRO), and the Chandra X-Ray Observatory(CXO). Spitzer is also a part of NASA's Astronomical Search for Origins Program, designed to provide information which will help us understand our cosmic roots, and how galaxies, stars and planets develop and form. 3 http://www.spitzer.caltech.edu/ August 2006 Bogdan Popescu

  6. Spitzer Space telescope - IRAC 3 The Infrared Array Camera (IRAC) is one of Spitzer's three science instruments, and provides imaging capabilities at near- and mid-infrared wavelengths. It is a general-purpose camera that will be used by observers on Spitzer for a wide variety of astronomical research programs. IRAC is a four-channel camera that provides simultaneous 5.12 x 5.12 arcmin images at 3.6, 4.5, 5.8, and 8 microns. Each of the four detector arrays in the camera are 256 x 256 pixels in size. IRAC uses two sets of detector arrays. The two short-wavelength channels are imaged by composite detectors made from indium and antimony. The long-wavelength channels use silicon detectors that have been specially treated with arsenic. The only moving part in IRAC is the camera shutter. 3 http://www.spitzer.caltech.edu/ August 2006 Bogdan Popescu

  7. Spitzer Space telescope - IRS 3 The Infrared Spectrograph(IRS) is one of the three instruments onboard Spitzer and provides both high- and low-resolution spectroscopy at mid-infrared wavelengths. Spectrometers are instruments which spread light out into its constituent wavelengths creating a spectra. Within this spectra, astronomers can study emission and absorption lines: which are the fingerprints of atoms and molecules The IRS has four separate modules: a low-resolution, short-wavelength mode covering the 5.3-14 micron interval; a high-resolution, short-wavelength mode covering 10-19.5 microns; a low-resolution, long-wavelength mode for observations at 14-40 microns; and a high-resolution, long-wavelength mode for 19-37 microns. Each module has its own entrance slit to let infrared light in. The detectors are 128 x 128 arrays. The shorter-wavelength silicon detectors are treated with arsenic; the longer-wavelength silicon detectors are treated with antimony. The IRS instrument consists of two physically separated parts, the cold assemblies which are located within the Spitzer multiple instrument chamber and the warm electronics, which are located in the Spitzer spacecraft bus. The IRS has no moving parts! 3 http://www.spitzer.caltech.edu/ August 2006 Bogdan Popescu

  8. The DEEP2 Redshift Survey 4 The DEEP survey is a two-phased project using the Keck telescopes to study the distant Universe. Phase 1 used the LRIS spectrograph to study a sample of ~1000 galaxies to a limit of I=24.5. This project was executed by the UCSC team and is a pilot program for the phase 2 effort. Phase 2 of the DEEP project is using the new DEIMOS spectrograph to obtain spectra of ~50,000 faint galaxies with redshifts z>0.7. The scientific goals are to study the evolution of properties of galaxies and the evolution of the clustering of galaxies compared to samples at low redshift. The survey is designed to have the fidelity of local redshift surveys such as the LCRS survey, and to be complementary to ongoing large redshift surveys such as the SDSS project and the 2dF survey. The DEIMOS/DEEP or DEEP2 survey has been executed with resolution R~5000, and we measure linewidths and rotation curves for a substantial fraction of the target galaxies. DEEP2 will thus also be complementary to the VLT/VIRMOS Deep Survey project, which will survey more galaxies in a larger region of the sky but with much lower spectral resolution and with fewer objects at high redshift. InstrumentDEIMOS spectrograph on Keck II Principal Redshift Range z=0.75-1.4 4 http://deep.berkeley.edu/ August 2006 Bogdan Popescu

  9. KECK Observatory 5 The DEEP From a remote outpost on the summit of Mauna Kea astronomers at the W. M. Keck Observatory probe the deepest regions of the Universe with unprecedented power and precision. Their instruments are the twin Keck Telescopes, the world's largest optical and infrared telescopes. Each stands eight stories tall and weighs 300 tons, yet operates with nanometer precision. At the heart of each Keck Telescope is a revolutionary primary mirror. Ten meters in diameter, the mirror is composed of 36 hexagonal segments that work in concert as a single piece of reflective glass. Made possible through grants totaling more than $140 million from the W. M. Keck Foundation, the Observatory is operated by the California Association for Research in Astronomy (CARA), whose Board of Directors includes representatives from the California Institute of Technology and the University of California. In 1996, the National Aeronautics and Space Administration (NASA) joined as a partner in the Observatory. The Keck I telescope began science observations in May 1993; Keck II began in October 1996. Keck's capabilities make full use of Mauna Kea's research potential. Surrounded by thousands of miles of relatively thermally stable ocean, the 13,796-foot Mauna Kea summit has no nearby mountain ranges to roil the upper atmosphere or throw light-reflecting dust into the air. Few city lights pollute its extremely dark skies. For most of the year, the atmosphere above Mauna Kea is clear, calm and dry. 5 http://www.keckobservatory.org/ August 2006 Bogdan Popescu

  10. KECK/DEIMOS 6 The DEep Imaging Multi-Object Spectrograph (DEIMOS) is a general-purpose, faint-object, multi-slit, double-beam, visible-wavelength imaging spectrograph currently being assembled at the Nasmyth focus on Keck II. First light was achieved in June 2002 and first science commenced two weeks later. DEIMOS features wide spectral coverage (up to 5000 Å per exposure), high spectral resolution (down to ~1 Å), high throughput, and relatively wide field of view (81.5 arcmin² field). Conceived as a dual-beam instrument, it has been built with one camera and offers three observing modes: direct imaging, long-slit, and multi-slit spectroscopy. 6 http://www2.keck.hawaii.edu/inst/deimos/ August 2006 Bogdan Popescu

  11. GOODS: The Great Observatories Origins Deep Survey7 The Great Observatories Origins Deep Survey (GOODS) incorporates a Spitzer Legacy project designed to study galaxy formation and evolution over a wide range of redshift and cosmic lookback time. The project will trace the mass assembly history of galaxies, the evolution of their stellar populations, and the energetic output from star formation and active nuclei. GOODS builds on the deepest observations from NASA's other Great Observatories, Hubble and Chandra, and will be done in partnership with astronomers at Gemini and ESO, with a commitment of extensive ESO and NOAO observing time. By observing at lambda > 3 um, Spitzer will measure the rest-frame near- and mid-infrared light from objects at 1 < z < 6, but very deep observations are needed to detect "ordinary" galaxies at these high redshifts. GOODS will survey approximately 300 square arcmin divided into two fields: the Hubble Deep Field North and the Chandra Deep Field South. These are among the most data-rich portions of the sky, and are the sites of the deepest observations from Hubble, Chandra, ESA's XMM-Newton, and from many ground-based facilities. Dividing our survey area provides insurance against cosmic variance due to galaxy clustering, and guarantees that astronomers in both hemispheres can carry out related observations. GOODS will image these fields at 3.6-8 um with IRAC, with a mean exposure time per position of approximately 25 hours per band, reaching far deeper flux limits than observations planned for the Guaranteed Time programs. 10 hour exposures with MIPS at 24 um are also planned, pending on-orbit tests to establish that the data will achieve a significant gain in sensitivity relative to planned 20 minute GTO exposures. Finally, a pair of ultradeep IRAC fields are planned for the HDF-N, with total exposure times up to 100 hours, again pending on-orbit demonstration of instrument performance and source confusion. 7 http://www.stsci.edu/science/goods/ August 2006 Bogdan Popescu

  12. GOODS: The Great Observatories Origins Deep Survey7 The GOODS IRAC observations are designed to detect rest-frame near-infrared light from the progenitors of galaxies like the Milky Way out to z=4, and will enable us to measure the stellar mass distribution of galaxies through most of cosmic history. The smaller, ultradeep IRAC field will probe the faintest sources and highest redshifts. The MIPS observations will offer the best opportunity to detect emission from dust-obscured star formation in ordinary galaxies out to z=2.5, and, in concert with the Chandra data, will enable a census of supermassive central black holes in obscured and unobscured AGN. Overall, the data will provide the best lower limits to the extragalactic background light at 3.6-24 um. By combining space- and ground-based observations, we will create a public data archive extending from X-ray through radio wavelengths, with a large sample of objects out to the highest known redshifts. This survey will give a uniquely comprehensive history of galaxies, from early epochs to the relatively recent past, and will serve as a bridge to future exploration in these wavelength and redshift regimes with the Next Generation Space Telescope. The GOODS HST Treasury Program will use the new Advanced Camera for Surveys (ACS) to image the two GOODS fields through four broad, non-overlapping filters: F435W (B), F606W (V), F775W (i), and F850LP (z). The exposure times will be 3, 2.5, 2.5 and 5 orbits per filter, respectively, reaching extended-source sensitivities within 0.5-0.8 mags of the WFPC2 HDF observations. GOODS is a deep survey, not a wide one, but it is much larger than most previous, deep HST/WFPC2 surveys, covering 320 square arcmin, 32x the combined solid angles of the HDF-N and S, and 4x larger than their combined flanking fields. The Viz imaging will be taken in five repeat visits separated by approximately 45 days, enabling a search for SNe Ia at 1.2 < z < 1.8 to test the transition from cosmic deceleration to acceleration predicted in world models dominated by dark energy. The z-band observations will image the optical rest-frame light from galaxies out to z = 1.2, with angular resolution superior to that from WFPC2. Combined GOODS data from HST, Spitzer, Chandra, and ground-based observatories will make it possible to map the evolution of the Hubble sequence with redshift, reconstructing the history of galaxy mass assembly, star formation and nuclear activity. The ACS BViz imaging will enable a systematic survey of Lyman break galaxies at 4 < z < 6.5, reaching back to the suggested epoch of reionization. The HST data will also provide a powerful tool to study the dark matter mass around galaxies using gravitational lensing, to search for low-mass stars in our own galaxy, and perhaps to detect moving objects in the outer solar system. 7 http://www.stsci.edu/science/goods/ August 2006 Bogdan Popescu

  13. COSMOS – Cosmic Evolution Survey8 8 http://www.astro.caltech.edu/~cosmos/ August 2006 Bogdan Popescu

  14. COSMOS – Cosmic Evolution Survey8 COSMOS Project Summary COSMOS is an HST Treasury Project to survey a 2 square degree equatorial field with the Advanced Camera for Surveys (ACS). It is the largest survey that HST has ever done, utilizing 10% (640 orbits) of its observing time over the course of two years (HST Cycles 12 and 13). The project also incorporates major commitments from other observatories around the world, including the VLA radio telescope, ESO's VLT in Chile, ESA's XMM X-ray satellite, and Japan's 8-meter Subaru telescope in Hawaii. The COSMOS collaboration involves almost 100 scientists in a dozen countries. The primary goal of COSMOS is to study the relationship between large scale structure (LSS) in the universe and the formation of galaxies, dark matter, and nuclear activity in galaxies. This includes a careful analysis of the dependence of galaxy evolution on environment. The wide field of coverage of COSMOS will sample a larger range of LSS than any previous HST survey. COSMOS will detect: * over 2 million objects with IAB > 27 mag * over 35,000 Lyman Break Galaxies (LBGs) * extremely red galaxies out to z ~ 5 The COSMOS field is equatorial, for easy access to telescopes in both hemispheres: RA (J2000) = 10:00:28.6 DEC (J2000) = +02:12:21.0 Status of COSMOS: July 1, 2005 COSMOS has completed all of its HST observations. This includes two years of observations with the ACS, WFPC2, and NICMOS instruments. Currently the first cycle of observations are available through the COSMOS Archive. Additional observations, such as the Subaru optical, VLA radio, and XMM X-ray surveys of the field have also been completed. Those data will be released over the next several months. Object catalogs are also being produced, and spectral observations of objects in the field are ongoing. 8 http://www.astro.caltech.edu/~cosmos/ August 2006 Bogdan Popescu

  15. GALEX – Galaxy Evolution Explorer9 The Galaxy Evolution Explorer (GALEX) is an orbiting space telescope that will observe galaxies in ultraviolet light across 10 billion years of cosmic history. Such observations will tell scientists how galaxies, the basic structures of our Universe, evolve and change. Additionally, GALEX will probe the causes of star formation during a period when most of the stars and elements we see today had their origins. Led by the California Institute of Technology, GALEX will conduct several first-of-a-kind sky surveys, including an extra-galactic (beyond our galaxy) ultraviolet all-sky survey. During its 29 month mission GALEX will produce the first comprehensive map of a Universe of galaxies under construction, bringing us closer to understanding how galaxies like our own Milky Way were formed. GALEX will also identify celestial objects for further study by ongoing and future missions. GALEX data will populate a large, unprecedented archive available to the entire astronomical community and to the general public. Scientists would like to understand when the stars that we see today and the chemical elements that make up our Milky Way galaxy were formed. With its ultraviolet observations, GALEX will fill in one of the key pieces of this puzzle. 9 http://www.galex.caltech.edu/ August 2006 Bogdan Popescu

  16. GALEX – Galaxy Evolution Explorer9 GALEX is a small explorer class mission that is part of NASA's Structure and Evolution of the Universe theme. These are relatively inexpensive science missions that typically weigh around 500 pounds or less. GALEX will be launched from Cape Canaveral Air Force station by a Pegasus XL rocket and will orbit 690 kilometers (428 miles) above Earth for 29 months. During the mission GALEX will observe hundreds of thousands of nearby and distant galaxies in ultraviolet (UV) light. Additionally, GALEX will view the stars in our own galaxy, the Milky Way. Science Objectives GALEX will perform both imaging and spectroscopy (the study of the spectrum, or range, of light), conducting several types of surveys. Some of the GALEX surveys will be science "firsts." For example, GALEX is the first mission to conduct an extra-galactic (beyond our galaxy) all-sky survey. During these surveys, GALEX will be "polling" the skies like a census taker, examining the UV emission from star-forming regions in all types of galaxies. To perform these many science firsts, GALEX will take full advantage of the science data of previous and current missions. With its wide field of view and sensitive UV detectors, GALEX will complement the capabilities of space observatories like the Hubble Space Telescope (HST) and the UV spectroscopic capabilities of the Far Ultraviolet Spectroscopic Explorer, both currently in orbit. It will also complement future space observatories, such as the infrared observations of the Space Infrared Telescope Facility, launching in 2003, and the James Webb Space Telescope (formerly called the Next Generation Space Telescope), planned for later this decade. The comparison of the infrared all-sky survey maps obtained from satellites like the Infrared Astronomical Satellite and the UV all-sky maps produced by GALEX will allow astronomers to investigate the effects of gas and dust on star formation in galaxies. GALEX will also pave the way for future HST observations by identifying intriguing celestial objects for study. GALEX will single out galaxies that are actively creating stars. GALEX will also determine the relationship between the UV properties of galaxies and their star-formation rate, and then use that relationship to map the history of star formation across the Universe. 9 http://www.galex.caltech.edu/ August 2006 Bogdan Popescu

  17. GALEX – Galaxy Evolution Explorer9 Technology Firsts In addition to performing many science firsts, GALEX is also equipped with some technological firsts: * the first large (65 millimeter diameter) Far UV (FUV) and Near UV (NUV) microchannel plate sealed detectors * innovative coatings for optical components, including the first UV dichroic beam splitter and the first NUV red light blocking filter * the first FUV and NUV grism (spectroscopic grating on a prism) GALEX uses a single instrument with state-of-the-art UV detectors and a straightforward observing strategy to achieve its mission goals. Scientists expect these advanced technologies to help us understand when the stars that we see today, along with the chemical elements that make up the Milky Way, were formed. Data collected by GALEX will populate a large, unparalleled archive that will fill in this crucial missing piece of the current cosmological puzzle. Once the raw GALEX data is processed it will be made available to both the science community and the public. The GALEX archive will be cross referenced to other existing astronomical archives so information can be easily exchanged. LAUNCH DATE:    GALEX was launched at 8am EDT (5am PDT) on April 28th, 2003. 9 http://www.galex.caltech.edu/ August 2006 Bogdan Popescu

  18. Subaru Telescope10 An 8.2-m Optical-Infrared TelescopeThe Subaru telescope is an optical-infrared telescope at the 4,200m (13,460ft.) summit of Mauna Kea on the island of Hawaii. The telescope represents a new generation in telescope design not only because of the size of its primary mirror with an effective aperture of 8.2 meters, but also because of the various revolutionary technologies used to achieve outstanding performance. An active support system that maintains an unprecedentedly high mirror surface accuracy, a new enclosure design to suppress local atmospheric turbulence, an extremely accurate tracking mechanism using magnetic driving systems, seven observational instruments installed at the four foci, and an auto-exchanger system to use the observational instruments effectively are just some of the unique features associated with this telescope. These sophisticated systems have been used and fine-tuned since the telescope's First Light. 10 http://www.naoj.org/ August 2006 Bogdan Popescu

  19. Subaru Telescope10 Subaru Telescope has a suite of seven first generation instruments providing imaging and spectroscopic capabilities over the full range of wavelengths from optical to mid-infrared. * AO - Subaru Adaptive Optics system - delivers diffraction-limited images in the near-infrared. * CIAO - Coronagraphic Imager with Adaptive Optics - provides a near-infrared imaging capability in the vicinity of bright sources. * COMICS - Cooled Mid-Infrared Camera and Spectrograph - provides imaging and spectroscopy from 8-20 microns. * FOCAS - Faint Object Camera And Spectrograph - provides optical imaging and longslit and multi-slit spectroscopy over a 6 arcmin field of view. * HDS - High Dispersion Spectrograph - provides extremely high-resolution optical spectroscopy. * IRCS - Infrared Camera and Spectrograph - provides imaging from 1-5 microns, and low-resolution and echelle spectroscopy over the same range. * MOIRCS - Multi-Object Infrared Camera and Spectrograph - provides imaging from 1.2-2.3 microns over a 4 arcmin x 7 arcmin field of view. * CISCO - Cooled Infrared Spectrograph and Camera for OHS - provides imaging and low-resolution spectroscopy in the near-infrared. * Suprime-Cam - Subaru Prime Focus Camera - provides optical imaging over a large field of view with a mosaic of CCDs. 10 http://www.naoj.org/ August 2006 Bogdan Popescu

  20. Subaru Telescope10 Infrared Camera and Spectrograph (IRCS) IRCS is a workhorse infrared instrument for the Subaru telescope, providing high angular resolution, sensitivity and is used in conjunction with the Adaptive Optics unit. It is able to separate light with a wavelength difference of 1 part in 20,000. Coronagraphic Imager with Adaptive Optics (CIAO) CIAO is a instrument for imaging faint objects close to much brighter objects such as searching planets around other stars. It is a powerful instrument for searching for planets around other stars. CIAO's infrared detector and optics are kept cool within a large vacuum container. Cooled Mid Infrared Camera and Spectrometer (COMICS) COMICS detects mid-infrared light between 10 and 20 μm. It can used to investigate the formation of planetary systems, starbursts in external galaxies, and the nature of interstellar dust particles. Faint Object Camera And Spectrograph (FOCAS) FOCAS is Subaru's workhorse instrument for high-sensitivity optical observations. It is equipped with a multi-slit system which allows spectra of up to 100 objects to be taken simultaneously. This is a powerful capability when measuring the distances to faint galaxies near the edge of the Universe. Subaru Prime Focus Camera (Suprime-Cam) Suprime-Cam mounts at Subaru's prime focus where the field of view is 30 arcmin, equivalent to the diameter of the full moon. By simultaneously imaging such a large field, we can efficiently perform studies of the formation and evolution of galaxies and the structure of the Universe. Suprime-Cam can also be used to search for Kuiper Belt objects (small bodies at the edge of the Solar System). It is a digital camera with a total of 80 million pixels, using 10 CCDs with 4096 x 2048 pixels each. High Dispersion Spectrograph (HDS) HDS splits light into its constituent colors with an accuracy of 1 part in 100,000. With this precision, we can investigate the evolution of elemental abundances by observing old stars, and learn about the physical and chemical state of intergalactic gas from quasar absorption line studies. 10 http://www.naoj.org/ August 2006 Bogdan Popescu

  21. Subaru Telescope10 OH-Airglow Suppressor (OHS) By eliminating infrared light emitted by OH airglow in the upper atmosphere, OHS achieves the high sensitivity required to obtain spectra of faint objects such as distant galaxies and brown dwarfs. Adaptive Optics (AO) The Subaru telescope has achieved an angular resolution of 0.2 arcsec at wavelength of 2 μm by minimizing air turbulence inside the enclosure. This resolution is, however, still limited by atmospheric turbulence. With the Adaptive Optics system, which can compensate for the distorted wavefront very rapidly, the light can be focused still further, limited only by the diameter of the primary mirror. For many observations, this limit of 0.06 arcsec exceeds the resolution of the Hubble Space Telescope. Each of Subaru's seven instruments detects light in either the optical or the infrared. Instruments like FOCAS and IRCS function as both a camera and a spectrograph. HDS specializes in high resolution spectroscopy. Instruments with different fields of view or special features optimized for particular scientific targets sometimes have overlapping wavelength and resolution coverage. 10 http://www.naoj.org/ August 2006 Bogdan Popescu

  22. CFHT (Canada-France-Hawaii Telescope)11 WIRCam - the CFHT wide-field infrared camera (20'x20', 0.3" pixels) General Characteristics: Total field of view 20'x20' Plate scale 0.30 arcsec/pixel Filters Y, J, H, K', and a small selection of narrow band filters Location Prime Focus Guiding On chip sensing, and ~5hz tip-tilt plate Detector format (2x2)x(2048x2048) Spectral range 0.85-2.5µm Mean quantum efficiency (detector only) >65 % Readout time (full frame, CDS mode) <1.5 seconds Detector material HgCdTe Readout Direct readout (4 channels per individual detector, 16 total) Pixel pitch 18µm Filling factor 100 % Operating temperature 80 K (cryogenerator) Readout noise < 20 e-/pixel (goal) Full well capacity 100.000 e- Orientation on the sky North up, within 2 degrees 11 http://www.cfht.hawaii.edu/ August 2006 Bogdan Popescu

  23. ESO VLT12 The ESO Very Large Telescope (VLT) at the Paranal Observatory (Atacama, Chile) is the world's largest and most advanced optical telescope. It comprises four 8.2-m reflecting Unit Telescopes and several moving 1.8-m Auxiliary Telescopes, the light beams of which can be combined in the VLT Interferometer (VLTI) . With its unprecedented optical resolution and unsurpassed surface area, the VLT produces extremely sharp images and can record light from the faintest and most remote objects in the Universe.The large telescopes are named ANTU, KUEYEN , MELIPAL and YEPUN. 12 http://www.eso.org/outreach/ut1fl/ August 2006 Bogdan Popescu

  24. ESO VLT / VIMOS13 VLT / VIMOS (VIsible MultiObject Spectrograph) VIMOS is a visible (360 to 1000 nm) wide field imager and multi- object spectrograph mounted on the Nasmyth focus B of UT3 Melipal. The instrument is made of four identical arms with each a field of view of 7' x 8' with a 0.205" pixel size and a gap between each quadrant of ~2'. Each arm is equipped with 6 grisms providing a spectral resolution range from ~200-2500 and with one EEV CCD 4k x 2k. VIMOS operates in three different modes: Imaging (IMG), Multi-Object Spectroscopy (MOS), and with Integral Field Unit (IFU). * IMG: Imaging is possible in UBVRIz filters in a 4 x 7' x 8' field of view. * MOS: Multi-object spectroscopy is carried out using masks (one per quadrant) prepared in Paranal using a laser cutting Mask Manufacturing Unit. Depending on the grism used, the spectral resolution varies from 200 to 2500, and the observable range is from 360 to 1000 nm. The maximum number of slits per mask (quadrant) varies from ~40 at R=2500 to ~150-200 at R=200, for a field of view of 4 x 7' x 8'. * IFU: VIMOS is also equipped with an integral field unit made of 6400 fibers. The scale on the sky can be changed from 0.67" per fiber to 0.33" per fiber and the integral field unit can cover up 13"x 13" up to 54"x54" on sky depending on spectral resolution and spatial magnification. Spectral resolution and coverage are similar to MOS 13 http://www.eso.org/instruments/vimos/ August 2006 Bogdan Popescu

  25. Gemini Observatory14 The Gemini Observatory consists of twin 8-meter optical/infrared telescopes located on two of the best sites on our planet for observing the universe. Together these telescopes can access the entire sky. The Gemini South telescope is located at almost 9,000’ elevation on a mountain in the Chilean Andes called Cerro Pachan. Cerro Pachan shares resources with the adjacent SOAR Telescope and the nearby telescopes of the Cerro Tololo Inter-American Observatory. The Frederick C. Gillett Gemini North Telescope is located on Hawaii's Mauna Kea as part of the international community of observatories that have been built to take advantage of the superb atmospheric conditions on this long dormant volcano that rises almost 14,000' into the dry, stable air of the Pacific. The Gemini Observatory’s international headquarters is located in Hilo, Hawaii. Both of the Gemini telescopes have been designed to take advantage of the latest technology and thermal controls to excel in a wide variety of optical and infrared capabilities. One example of this is the unique Gemini coating chamber that uses "sputtering" technology to apply protected silver coatings on the Gemini mirrors to provide unprecedented infrared performance. 14 http://www.gemini.edu/ August 2006 Bogdan Popescu

  26. Gemini Observatory14 Gemini’s aggressive instrument program keeps the observatory at the cutting edge of astronomical research. By incorporating technologies such as laser guide stars, Multi-Conjugate Adaptive Optics and multi-object spectroscopy, astronomers in the Gemini partnership have access to the latest tools for exploring the universe. Gemini was built and is operated by a partnership of 7 countries including the United States, United Kingdom, Canada, Chile, Australia, Brazil and Argentina. Any astronomer in each partner country can apply for time on Gemini with is allocated in accordance with the amount of financial support provided by each country. 14 http://www.gemini.edu/ August 2006 Bogdan Popescu

  27. Gemini / GMOS (Gemini Multi-Object Spectrograph)15 MAIN MODES * Direct imaging * Long-slit spectroscopy * Multi-slit spectroscopy using custom-made masks * Integral field spectroscopy BASIC SPECIFICATIONS Wavelength range 0.36-1.1 microns (with a design capability to 1.8 microns) Field of View 5.5 x 5.5 arcmin  Detector array of 3 CCDs: each 4608x2048 13.5um pixels Scale 0.07 arcsec/pixel Filters Two wheels with 11 slots + 1 clear aperture each. Initial filter set is SDSS g' r' i' z'.  Gratings Grating turret holds 3 interchangeable gratings and one mirror. Initially 6 gratings for 2 GMOSs Resolving power R up to 10,000 with 0.25 arcsec slits  Slit Masks Up to 600 slits per mask, minimum slit width = 0.2 arcsec  " Straight or curved slits possible  " Maximum slit length = 5.5 arcmin  Integral Field Unit 0.2 arcsec sampling over 50 square arcsec field SCIENTIFIC DRIVERS Since the GMOS spectrographs are common-user instruments, there are many scientific drivers, eg: * Surveys of faint galaxies which require not only high efficiency but also the ability to arrange slits in multiple tiers to increase the multiplex gain. * Surveys of dark matter in low mass galactic systems which require the ability to measure radial velocities to 1 - 2 km/s and multi-object capability so that complete stellar systems can be surveyed in one observation. * Two-dimensional (integral field) spectroscopy of intermediate-redshift objects on scales similar to that of the Hubble Space Telescope to study kinematics, star formation and to obtain accurate distance estimates. 15 http://www.roe.ac.uk/atc/projects/gmos/main.html August 2006 Bogdan Popescu

  28. Links http://www.physics.uc.edu/~popescu/ August 2006 Bogdan Popescu

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