DOCSLIB.ORG

The Galaxy Evolution Explorer (GALEX). Its Legacy of UV Surveys, and Science Highlights

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Galaxy Evolution Explorer (GALEX). Its Legacy of UV Surveys, and Science Highlights The Galaxy Evolution Explorer (GALEX). Its legacy of UV surveys, and science highlights Luciana Bianchi Abstract FUV (λeff ∼ 1528A,˚ 1344-1786A)˚ and NUV (λeff ∼ The Galaxy Evolution Explorer (GALEX) imaged 2310A,˚ 1771-2831A).˚ It was operated with NASA sup- the sky in the Ultraviolet (UV) for almost a decade, port until 2012, then for a short time with support delivering the first sky surveys at these wavelengths. from private funding from institutions; it was decom- 1 Its database contains far-UV (FUV, λeff ∼ 1528A)˚ missioned on June 28, 2013. and near-UV (NUV, λeff ∼ 2310A)˚ images of most of GALEX's instrument consisted of a Ritchey-Chr´etien−type the sky, including deep UV-mapping of extended galax- telescope, with a 50 cm primary mirror and a focal ies, over 200 million source measurements, and more length of 299.8cm. Through a dichroic beam splitter, than 100,000 low-resolution UV spectra. The GALEX light was fed to the FUV and NUV detectors simul- archive will remain a long-lasting resource for statisti- taneusly. The FUV detector stopped working in May cal studies of hot stellar objects, QSOs, star-forming 2009; subsequent GALEX observations have only NUV galaxies, nebulae and the interstellar medium. It pro- imaging (Figure 1). vides an unprecedented road-map for planning future The GALEX field of view is ≈1.2◦ diameter (1.28/1.24◦, UV instrumentation and follow-up observing programs FUV/NUV), and the spatial resolution is ≈ 4.2/5.300 (Morrissey in the UV and at other wavelengths. et al. 2007). For each observation, the photon list We review the characteristics of the GALEX data, recorded by the two photon-counting micro-channel and describe final catalogs and available tools, that fa- plate detectors is used to reconstruct an FUV and an cilitate future exploitation of this database. We also NUV image, sampled with virtual pixels of 1.500 . From recall highlights from the science results uniquely en- the reconstructed image, the pipeline then derives a abled by GALEX data so far. sky background image, and performs source photome- Keywords Ultraviolet: surveys; Astronomical Data try. Sources detected in FUV and NUV images of the Bases: catalogs; Stars: post-AGB; Stars: White same observation are matched by the pipeline with a 00 Dwarfs; Galaxies: Milky Way; Ultraviolet: galaxies; 3 radius, to produce a merged list for each observation Ultraviolet: QSOs (Morrissey et al. 2007). To reduce localized response variations, in order to maximize photometric accuracy, each observation was 1 Introduction. GALEX instrument and data carried out with a 10 spiral dithering pattern. The sur- veys were accumulated by painting the sky with con- The Galaxy Evolution Explorer (GALEX), a NASA tiguous tiles, with series of such observations. A trailing Small Explorer Class mission, was launched on April 28, mode was instead used for the latest, privately-funded 2003 to perform the first sky-wide Ultraviolet surveys, observations, to cover some bright areas near the MW with both direct imaging and grism in two broad bands, plane. These latest data currently are not in the public archive. Luciana Bianchi Dept. of Physics & Astronomy, The Johns Hopkins University, 1GALEX was developed by NASA with contributions from the 3400 N. Charles St., Baltimore, MD 21218, USA Centre National d'Etudes Spatiales of France and the Korean http://dolomiti.pha.jhu.edu Ministry of Science and Technology. 2 At the end of the GALEX mission, the AIS survey were now reprocessed as part of the MAST effort to fi- was extended towards the Galactic plane, largely inac- nalize the database, therefore the final archive will con- cessible during the prime mission phase because of the tain a few more entries. Figure 1 shows the sky coverage many bright stars that violated high-countrate safety of all GALEX observations performed in both FUV and limits. A survey of the Magellanic Clouds (MC), also NUV (right), and in NUV regardless of FUV-detector previously unfeasible due to brightness limits, was com- status (left). The map does not include the last NUV pleted at the end, relaxing the initial count-rate saftey trailed observations (CLAUSE dataset). threshold. Because of the FUV detector's failure, these extensions include only NUV measurements (Figure 1). Much of this short review concerns GALEX's final 3 GALEX database and science catalogs data products (from the point of view of science applica- tions; technical documentation is available elsewhere), GALEX data can be obtained from the NASA MAST This choice, at the price of confining science results to archive at http://galex.stsci.edu. They include images a few highlights (Section 7), responds to various in- (direct imaging or grism) and associated photometry quiries and requests, timely as the almost entire (and from the pipeline, or extracted spectra. High-level sci- final) database is becoming available, and new tools, ence catalogs (HLSP) are also available, such as those which will support new investigations. described below, which greatly facilitate some investi- gations. Several objects have multiple measurements in the 2 GALEX surveys database, due to repeated observations of the same field, or overlap between fields. For studies involving GALEX has performed sky surveys with different depth UV-source counts, one needs to eliminate repeats, as and coverage (Morrissey et al. 2007, Bianchi 2009). well as artefacts. Therefore, we have constructed cata- The two detectors, FUV and NUV, observed simulta- logs of unique UV sources, eliminating duplicate mea- neously as long as the FUV detector was operational; surements of the same object. Separate catalogs were note however that there are occasional observations in which one of the two detectors was off (mostly FUV) constructed for AIS and MIS, because of the ∼2-3 mag due to brief shut-downs, even in the early part of the difference in depth. The most recent version of such mission, and in some observations the FUV and NUV catalogs is published by Bianchi et al. (2014a, here- exposure times differ (see Bianchi et al. 2014a, in par- after \BCS", see Appendix A); BCS also presented sky ticular their Table 1 and Fig. 2). maps showing density of UV sources with various cuts. The surveys with the largest area coverage are the A previous version, based on data release GR5, was All-Sky Imaging survey (AIS) and the Medium-depth published by Bianchi et al. (2011a, b), who extensively Imaging Survey (MIS). Exposure times slightly vary discuss criteria for constructing GALEX source cata- within each survey, around the respective nominal ex- logs and matched catalogs between GALEX and SDSS, posures of 100 sec for AIS (corresponding to a depth GSC2, and more. Earlier work on source classification of FUV∼20/NUV∼21 ABmag) and 1500 sec for MIS was presented by Bianchi et al. (2007, 2005), Bianchi (corresponding to a depth of ∼22.7 ABmag in both (2009). FUV and NUV). The Deep Imaging Survey (DIS) ac- In the GALEX database, the non-detection value for cumulated exposures of the order of several tens of the FUV magnitude, FUV =-999, means either that thousand of seconds in selected fields (for a 30,000 sec the detector was on but the source was too faint to exposure, the depth reached is ∼24.8/24.4 ABmag in be measured in FUV, of the FUV detector was off. In FUV/NUV). The \Nearby Galaxies Survey" (Bianchi order to examine and classify sources by colors, and rel- et al. 2003, Gil de Paz et al. 2007) covered initially 436 ative fraction of sources with different colors, Bianchi fields at MIS depth, but hundreds of additional nearby et al. (2014a, 2011a) restricted the catalogs to those galaxies were mapped by GALEX, as part of MIS or observations in which both detectors were exposed. In other surveys. Other observations were obtained for addition, these catalogs were conservatively restricted guest investigator (GI) programs, and for other tar- to measurements within the central 1◦ diameter of the geted regions such as, for example, the Kepler field. field of view, to exclude the outer rim, where distor- The GALEX database at the end of the mission tions prevent position and photometry of sources to be (2013, data release GR7) contained 214,449,551 source derived accurately, and counts from rim's spikes cause measurements, most of which (210,691,504) from obser- numerous artefacts to intrude the source list. For more vations with both detectors on. However, a small num- details we refer to the original BCS publication. ber of additional datasets obtained throughout the mis- The BCS catalogs include 28,707 AIS fields with sion, which were not previously included in the archive, both FUV and NUV exposed, covering a unique area 3 Fig. 1 Sky coverage, in Galactic coordinates, of the GALEX imaging. The surveys with the largest area coverage are AIS (blue) and MIS (green). Observations from other surveys are shown in black (figure adapted from Bianchi et al. 2014a). Data from the privately-funded observations at the end of the mission are not shown. Left: fields observed with at least the NUV detector on; right: fields observed with both FUV and NUV detectors on. The latter constitute the BCScat's. Fig. 2 Portion of a GALEX field with the stellar cluster NGC2420 (de Martino et al. 2008). Green circles mark sources detected with our photometry, the purple contours mark sources as defined by the GALEX pipeline. The right-side image is an enlargement of the crowded region. The left image also includes a section of the field’s outer edge, showing how numerous rim artefacts intrude photometric source detections. The rim is excluded from the BCS catalogs. Fig.
Load more

Recommended publications
  • REVIEW ARTICLE the NASA Spitzer Space Telescope
    REVIEW OF SCIENTIFIC INSTRUMENTS 78, 011302 ͑2007͒ REVIEW ARTICLE The NASA Spitzer Space Telescope ͒ R. D. Gehrza Department of Astronomy, School of Physics and Astronomy, 116 Church Street, S.E., University of Minnesota, Minneapolis, Minnesota 55455 ͒ T. L. Roelligb NASA Ames Research Center, MS 245-6, Moffett Field, California 94035-1000 ͒ M. W. Wernerc Jet Propulsion Laboratory, California Institute of Technology, MS 264-767, 4800 Oak Grove Drive, Pasadena, California 91109 ͒ G. G. Faziod Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138 ͒ J. R. Houcke Astronomy Department, Cornell University, Ithaca, New York 14853-6801 ͒ F. J. Lowf Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, Arizona 85721 ͒ G. H. Riekeg Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, Arizona 85721 ͒ ͒ B. T. Soiferh and D. A. Levinei Spitzer Science Center, MC 220-6, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125 ͒ E. A. Romanaj Jet Propulsion Laboratory, California Institute of Technology, MS 264-767, 4800 Oak Grove Drive, Pasadena, California 91109 ͑Received 2 June 2006; accepted 17 September 2006; published online 30 January 2007͒ The National Aeronautics and Space Administration’s Spitzer Space Telescope ͑formerly the Space Infrared Telescope Facility͒ is the fourth and final facility in the Great Observatories Program, joining Hubble Space Telescope ͑1990͒, the Compton Gamma-Ray Observatory ͑1991–2000͒, and the Chandra X-Ray Observatory ͑1999͒. Spitzer, with a sensitivity that is almost three orders of magnitude greater than that of any previous ground-based and space-based infrared observatory, is expected to revolutionize our understanding of the creation of the universe, the formation and evolution of primitive galaxies, the origin of stars and planets, and the chemical evolution of the universe.
    [Show full text]
  • In-Flight PSF Calibration of the Nustar Hard X-Ray Optics
    In-flight PSF calibration of the NuSTAR hard X-ray optics Hongjun Ana, Kristin K. Madsenb, Niels J. Westergaardc, Steven E. Boggsd, Finn E. Christensenc, William W. Craigd,e, Charles J. Haileyf, Fiona A. Harrisonb, Daniel K. Sterng, William W. Zhangh aDepartment of Physics, McGill University, Montreal, Quebec, H3A 2T8, Canada; bCahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA; cDTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby, Denmark; dSpace Sciences Laboratory, University of California, Berkeley, CA 94720, USA; eLawrence Livermore National Laboratory, Livermore, CA 94550, USA; fColumbia Astrophysics Laboratory, Columbia University, New York NY 10027, USA; gJet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA; hGoddard Space Flight Center, Greenbelt, MD 20771, USA ABSTRACT We present results of the point spread function (PSF) calibration of the hard X-ray optics of the Nuclear Spectroscopic Telescope Array (NuSTAR). Immediately post-launch, NuSTAR has observed bright point sources such as Cyg X-1, Vela X-1, and Her X-1 for the PSF calibration. We use the point source observations taken at several off-axis angles together with a ray-trace model to characterize the in-orbit angular response, and find that the ray-trace model alone does not fit the observed event distributions and applying empirical corrections to the ray-trace model improves the fit significantly. We describe the corrections applied to the ray-trace model and show that the uncertainties in the enclosed energy fraction (EEF) of the new PSF model is ∼<3% for extraction ′′ apertures of R ∼> 60 with no significant energy dependence.
    [Show full text]
  • Tiny "Chipsat" Spacecra Set for First Flight
    7/24/2019 Tiny "Chipsat" Spacecraft Set for First Flight - Scientific American Subscribe S P A C E Tiny "Chipsat" Spacecra Set for First Flight Launch in July will test new way to explore the solar system—and beyond By Nicola Jones, Nature magazine on June 1, 2016 A rearward view of the International Space Station. Credit: NASA/Crew of STS-132 On 6 July, if all goes to plan, a pack of about 100 sticky-note-sized ‘chipsats’ will be launched up to the International Space Station for a landmark deployment. During a brief few days of testing, the minuscule satellites will transmit data on their energy load and orientation before they drift out of orbit and burn up in Earth’s atmosphere. https://www.scientificamerican.com/article/tiny-chipsat-spacecraft-set-for-first-flight/ 1/6 7/24/2019 Tiny "Chipsat" Spacecraft Set for First Flight - Scientific American The chipsats, flat squares that measure just 3.2 centimetres to a side and weigh about 5 grams apiece, were designed for a PhD project. Yet their upcoming test in space is a baby step for the much-publicized Breakthrough Starshot mission, an effort led by billionaire Yuri Milner to send tiny probes on an interstellar voyage. “We’re extremely excited,” says Brett Streetman, an aerospace engineer at the non- profit Charles Stark Draper Laboratory in Cambridge, Massachusetts, who has investigated the feasibility of sending chipsats to Jupiter’s moon Europa. “This will give flight heritage to the chipsat platform and prove to people that they’re a real thing with real potential.” The probes are the most diminutive members of a growing family of small satellites.
    [Show full text]
  • Cosmic Origins Newsletter, September 2016, Vol. 5, No. 2
    National Aeronautics and Space Administration Cosmic Origins Newsletter September 2016 Volume 5 Number 2 Summer 2016 Cosmic Origins Program Inside this Issue Update Summer 2016 Cosmic Origins Program Update ............................1 Mansoor Ahmed, COR Program Manager Hubble Reveals Stellar Fireworks in ‘Skyrocket’ Galaxy ................2 Message from the Astrophysics Division Director .........................2 Susan Neff, COR Program Chief Scientist Light Echoes Give Clues to Protoplanetary Disk ............................3 Far-IR Surveyor Study Status .............................................................5 Welcome to the September 2016 Cosmic Origins (COR) newslet- LUVOIR Study Status .........................................................................5 ter. In this issue, we provide updates on several activities relevant to Strategic Astrophysics Technology (SAT) Selections the COR Program objectives. Some of these activities are not under for ROSES-2015 ...................................................................................6 the direct purview of the program, but are relevant to COR goals, Technology Solicitations to Enable Astrophysics Discoveries ......6 therefore we try to keep you informed about their progress. Cosmic Origins Suborbital Program: Balloon Program – BETTII ................................................................7 In January 2016, Paul Hertz (Director, NASA Astrophysics) News from SOFIA ...............................................................................8 presented his
    [Show full text]
  • Abstract Observation Overview Nustar HXR Imaging Microflare
    Imaging and Spectroscopy of Six NuSTAR MicroFlares SH11D-2898 Contact: J. Duncan1, L. Glesener1, I. Hannah2, D. Smith3, B. Grefenstette4 (1Univ, of Minnesota; 2Univ. of Glasgow; 3UC Santa Cruz; 4California Institute of Technology) [email protected] Abstract MicroFlare Time Evolution Hard X-ray (HXR) emission in solar flares originates from regions of high temperature plasma, as well as from non-thermal particle populations [1]. Both of these sources of HXR radiation make solar observation in this band important for study of • NuSTAR observed 6 MicroFlares during this observation. Time evolution is shown in both raw and normalized NuSTAR flare energetics. NuSTAR is the first HXR telescope with direct focusing optics, giving it a dramatic increase in sensitivity countsLivetime acrosscorrection several applied energy ranges for each flare. Counts are livetime-corrected (NuSTAR livetime ranged from 1-14%). Livetime correction applied over previous indirect imaging methods. Here we present NuSTAR observation of six microflares from one solar active Livetime correction applied 5 5 6 5×10 4×10 2.0 10 5 × 4×10 5 region during a period of several hours on May 29th, 2018. In conjunction with simultaneous data from SDO/AIA, data 3×10 5 2-4 keV 2-4 keV 6 3×10 1.5 10 Orbit1, Flare B 4-6 keV 2×105 4-6 keV × 5 counts 2 10 2-4 keV × Orbit1, Flare A 6-8 keV counts Orbit1, Flare C 6-8 keV from this observation has been used to create flare-time images showing the spatial extent of HXR emission. Additionally, 5 5 1 10 1×10 8-10 keV × 8-10 keV 6 4-6 keV 1.0×10 (Left) Estimated GOES A5 flare, with 0 0 1.2 1.2 16:07 16:08 16:09 16:10 16:11 16:46 16:48 16:50 16:52 16:54 NuSTAR lightcurves show time evolution in four different HXR energy ranges over the course of each flare.
    [Show full text]
  • Build a Spacecraft Activity
    UAMN Virtual Family Day: Amazing Earth Build a Spacecraft SMAP satellite. Image: NASA. Discover how scientists study Earth from above! Scientists use satellites and spacecraft to study the Earth from outer space. They take pictures of Earth's surface and measure cloud cover, sea levels, glacier movements, and more. Materials Needed: Paper, pencil, craft materials (small recycled boxes, cardboard pieces, paperclips, toothpicks, popsicle sticks, straws, cotton balls, yarn, etc. You can use whatever supplies you have!), fastening materials (glue, tape, rubber bands, string, etc.) Instructions: Step 1: Decide what you want your spacecraft to study. Will it take pictures of clouds? Track forest fires? Measure rainfall? Be creative! Step 2: Design your spacecraft. Draw a picture of what your spacecraft will look like. It will need these parts: Container: To hold everything together. Power Source: To create electricity; solar panels, batteries, etc. Scientific Instruments: This is the why you launched your satellite in the first place! Instruments could include cameras, particle collectors, or magnometers. Communication Device: To relay information back to Earth. Image: NASA SpacePlace. Orientation Finder: A sun or star tracker to show where the spacecraft is pointed. Step 3: Build your spacecraft! Use any craft materials you have available. Let your imagination go wild. Step 4: Your spacecraft will need to survive launching into orbit. Test your spacecraft by gently shaking or spinning it. How well did it hold together? Adjust your design and try again! Model spacecraft examples. Courtesy NASA SpacePlace. Activity adapted from NASA SpacePlace: spaceplace.nasa.gov/build-a-spacecraft/en/ UAMN Virtual Early Explorers: Amazing Earth Studying Earth From Above NASA is best known for exploring outer space, but it also conducts many missions to investigate Earth from above.
    [Show full text]
  • Nustar Observatory Guide
    NuSTAR Guest Observer Program NuSTAR Observatory Guide Version 3.2 (June 2016) NuSTAR Science Operations Center, California Institute of Technology, Pasadena, CA NASA Goddard Spaceflight Center, Greenbelt, MD nustar.caltech.edu heasarc.gsfc.nasa.gov/docs/nustar/index.html i Revision History Revision Date Editor Comments D1,2,3 2014-08-01 NuSTAR SOC Initial draft 1.0 2014-08-15 NuSTAR GOF Release for AO-1 Addition of more information about CZT 2.0 2014-10-30 NuSTAR SOC detectors in section 3. 3.0 2015-09-24 NuSTAR SOC Update to section 4 for release of AO-2 Update for NuSTARDAS v1.6.0 release 3.1 2016-05-10 NuSTAR SOC (nusplitsc, Section 5) 3.2 2016-06-15 NuSTAR SOC Adjustment to section 9 ii Table of Contents Revision History ......................................................................................................................................................... ii 1. INTRODUCTION ................................................................................................................................................... 1 1.1 NuSTAR Program Organization ..................................................................................................................................................................................... 1 2. The NuSTAR observatory .................................................................................................................................... 2 2.1 NuSTAR Performance ........................................................................................................................................................................................................
    [Show full text]
  • + New Horizons
    Media Contacts NASA Headquarters Policy/Program Management Dwayne Brown New Horizons Nuclear Safety (202) 358-1726 [email protected] The Johns Hopkins University Mission Management Applied Physics Laboratory Spacecraft Operations Michael Buckley (240) 228-7536 or (443) 778-7536 [email protected] Southwest Research Institute Principal Investigator Institution Maria Martinez (210) 522-3305 [email protected] NASA Kennedy Space Center Launch Operations George Diller (321) 867-2468 [email protected] Lockheed Martin Space Systems Launch Vehicle Julie Andrews (321) 853-1567 [email protected] International Launch Services Launch Vehicle Fran Slimmer (571) 633-7462 [email protected] NEW HORIZONS Table of Contents Media Services Information ................................................................................................ 2 Quick Facts .............................................................................................................................. 3 Pluto at a Glance ...................................................................................................................... 5 Why Pluto and the Kuiper Belt? The Science of New Horizons ............................... 7 NASA’s New Frontiers Program ........................................................................................14 The Spacecraft ........................................................................................................................15 Science Payload ...............................................................................................................16
    [Show full text]
  • Building the Coolest X-Ray Satellite
    National Aeronautics and Space Administration Building the Coolest X-ray Satellite 朱雀 Suzaku A Video Guide for Teachers Grades 9-12 Probing the Structure & Evolution of the Cosmos http://suzaku-epo.gsfc.nasa.gov/ www.nasa.gov The Suzaku Learning Center Presents “Building the Coolest X-ray Satellite” Video Guide for Teachers Written by Dr. James Lochner USRA & NASA/GSFC Greenbelt, MD Ms. Sara Mitchell Mr. Patrick Keeney SP Systems & NASA/GSFC Coudersport High School Greenbelt, MD Coudersport, PA This booklet is designed to be used with the “Building the Coolest X-ray Satellite” DVD, available from the Suzaku Learning Center. http://suzaku-epo.gsfc.nasa.gov/ Table of Contents I. Introduction 1. What is Astro-E2 (Suzaku)?....................................................................................... 2 2. “Building the Coolest X-ray Satellite” ....................................................................... 2 3. How to Use This Guide.............................................................................................. 2 4. Contents of the DVD ................................................................................................. 3 5. Post-Launch Information ........................................................................................... 3 6. Pre-requisites............................................................................................................. 4 7. Standards Met by Video and Activities ...................................................................... 4 II. Video Chapter 1
    [Show full text]
  • Nustar and XMM-Newton Observations of the Hard X-Ray Spectrum of Centaurus A
    Downloaded from orbit.dtu.dk on: Sep 27, 2021 NuSTAR and XMM-Newton Observations of the Hard X-Ray Spectrum of Centaurus A Fürst, F.; Müller, C.; Madsen, K. K.; Lanz, L.; Rivers, E.; Brightman, M.; Arevalo, P.; Balokovi, M.; Beuchert, T.; Boggs, S. E. Total number of authors: 31 Published in: The Astrophysical Journal Link to article, DOI: 10.3847/0004-637X/819/2/150 Publication date: 2016 Document Version Publisher's PDF, also known as Version of record Link back to DTU Orbit Citation (APA): Fürst, F., Müller, C., Madsen, K. K., Lanz, L., Rivers, E., Brightman, M., Arevalo, P., Balokovi, M., Beuchert, T., Boggs, S. E., Christensen, F. E., Craig, W. W., Dauser, T., Farrah, D., Graefe, C., Hailey, C. J., Harrison, F. A., Kadler, M., King, A., ... Zhang, W. W. (2016). NuSTAR and XMM-Newton Observations of the Hard X-Ray Spectrum of Centaurus A. The Astrophysical Journal, 819(2), [150]. https://doi.org/10.3847/0004- 637X/819/2/150 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
    [Show full text]
  • Software Error Doomed Japanese Hitomi Spacecraft!
    Software error doomed Japanese Hitomi spacecraft! ! Space agency declares the astronomy satellite a loss.! ! Japan’s flagship Hitomi astronomical satellite, which launched successfully on 17 February but tumbled out of control five weeks later, may have been doomed by a basic engineering error. Confused about how it was oriented in space and trying to stop itself from spinning, Hitomi's software apparently fired a thruster jet in the wrong direction — accelerating rather than slowing the craft's rotation.! ! http://www.nature.com/news/software-error-doomed-japanese-hitomi- spacecraft-1.19835! 1! Gamma-Ray Bursts- Longair 22.7! • Are bright flashes of γ-rays- for a short period of time (<100 sec )! • fluxes of ~0.1-100 photon/cm2/sec/keV emitted primarily in the 20-500 keV band.! – Distribution is isotropic on the sky! • Because of these properties it took ~30 years from their discovery (1967) to their identification! – They are at very large distances (z up to 8 (!)) with apparent luminosities of 3x1054 erg/sec! – Rate is ~10-7/yr/galaxy ! • What are they??- short timescales imply compact object ; what could the 2 33 energy reservoir be- Mc implies M~10 gms~ Msun if total conversion of mass into energy How does all this energy end up as γ-rays ?! – Location of long γRBs is in and near star forming regions in smallish galaxies- associated with star formation! – a few γRBs have been associated with a type Ic supernova! 2! 3! Gamma-Ray Bursts ! • Cosmic γ-ray bursts (GRBs) were first reported in 1973 by Klebesadel et al (l973) but were first seen
    [Show full text]
  • The Spitzer Space Telescope and the IR Astronomy Imaging Chain
    Spitzer Space Telescope (A.K.A. The Space Infrared Telescope Facility) The Infrared Imaging Chain Fundamentals of Astronomical Imaging – Spitzer Space Telescope – 8 May 2006 1/38 The infrared imaging chain Generally similar to the optical imaging chain... 1) Source (different from optical astronomy sources) 2) Object (usually the same as the source in astronomy) 3) Collector (Spitzer Space Telescope) 4) Sensor (IR detector) 5) Processing 6) Display 7) Analysis 8) Storage ... but steps 3) and 4) are a bit more difficult! Fundamentals of Astronomical Imaging – Spitzer Space Telescope – 8 May 2006 2/38 The infrared imaging chain Longer wavelength – need a bigger telescope to get the same resolution or put up with lower resolution Fundamentals of Astronomical Imaging – Spitzer Space Telescope – 8 May 2006 3/38 Emission of IR radiation Warm objects emit lots of thermal infrared as well as reflecting it Including telescopes, people, and the Earth – so collection of IR radiation with a telescope is more complicated than an optical telescope Optical image of Spitzer Space Telescope launch: brighter regions are those which reflect more light IR image of Spitzer launch: brighter regions are those which emit more heat Infrared wavelength depends on temperature of object Fundamentals of Astronomical Imaging – Spitzer Space Telescope – 8 May 2006 4/38 Atmospheric absorption The atmosphere blocks most infrared radiation Need a telescope in space to view the IR properly Fundamentals of Astronomical Imaging – Spitzer Space Telescope – 8 May 2006 5/38
    [Show full text]