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Particle astrophysics and cosmology at SLACKIPAC--Activities in high energy astrophysics

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Particle astrophysics and cosmology at SLACKIPAC--Activities in high energy astrophysics Powered By Docstoc
					    Particle astrophysics and cosmology at
                   SLAC/KIPAC:
     Activities in high energy astrophysics
                               Greg Madejski
                        Stanford Linear Accelerator Center and
          Kavli Institute for Particle Astrophysics and Cosmology (KIPAC)


* KIPAC is the "new kid on the block" at SLAC, but very active in research

* KIPAC's charter is research in particle astrophysics and cosmology

* This presentation is mainly about the current/past scientific accomplishments
     and future projects (Astro-E2, PoGO, NuSTAR, NeXT) with emphasis on the
     synergy with SLAC's mission
Current space-based
astrophysics missions   • KIPAC members are
                          engaged in a broad
                          range of research
                          activities, mainly in
                          cosmology, high-
                          energy, and particle
                          astrophysics using
                          data from archival
                          and current
                          missions, but also
                          plans for future
                          endeavors

                        • This includes superb
                          facilities such as
                          Chandra, Hubble,
                          XMM-Newton, and
                          other missions
      Clusters of galaxies as cosmological probes




* Clusters of galaxies are largest gravitationally
bound and relaxed structures in the Universe;
intra-cluster gas is a source of X-ray emission
(Above: Abell 2029)
                                                     * Gravitational lensing of background galaxies
* Their mass/number density as a function of         provides an independent estimate of the cluster
time is an excellent probe of cosmological           mass, which generally (but not always!) agrees
parameters – best inferred via X-rays - but this     with the X-ray data
necessitates sensitive observations requiring
observatories such as Chandra                        * Much of the cutting-edge work with Hubble is
                                                     at KIPAC (Marshall, Allen, Peterson, Bradac, …)
* This will be covered in more detail by S. Allen    – and will continue with the JDEM data (talk by
                                                     P. Marshall)
       Supernovae and their remnants
                             * “Heavy” elements in the Universe were all
                               “cooked” in stars and ejected into
                               the interstellar space via supernovae

                             * Neutron stars left behind the explosion
                               gradually cool, radiating thermal continuum
                               with temperatures measurable via X-ray
                               spectroscopy

                             * Measurements of the flux + distance
                              (=luminosity) and neutron star surface
                              temperature determine radius and thus
                              with mass measuremets (from binary
                               properties) provide hints to determine
                               the equation of state

                             * Much of this research is done at KIPAC
                               (S. Kahn, W. Ho, M.-F. Gu, A. Spitkovsky,
                               R. Romani, M. Sako)




Kepler’s supernova remnant
                  Connections to GLAST
• Besides GLAST, introduced in the presentation by E. Bloom and
  discussed extensively in subsequent talks, KIPAC is involved in several
  new space-based missions, mainly funded by NASA or international
  collaborations
• Much of the data from those missions will be important to unraveling the
  details of the GLAST data
• A coherent picture of physics operating in those sources requires data
  over broad band of photon energies
• In particular, for variable sources - simultaneous observations will be
  essential
• Among the most important (but also competitive) will be observations in
  the X-ray band – unfortunately, one object at a time - so it is good that
  we are involved in Astro-E2, PoGO, NuSTAR, NeXT, …
• In all cases, funds towards hardware development are mainly from
  NASA but also from other countries (Sweden, Japan, France, ...)
Connection to GLAST: g-rays in perspective
* Any single band (g-ray, X-ray, radio, optical) is only
         a small part of the electromagnetic spectrum
* Studying astronomical sources across all spectral ranges can reveal very
         rich physical phenomena and is necessary for the “complete picture”
* Examples are broad-band spectra of active galaxies




 Mkn 421: data from Macomb et al. 1995)           3C279 (data from Wehrle et al. 1998)
           Connection to GLAST: jets in active galaxies
                                                     * The most numerous celestial g-ray emitters
                                                         on the sky are jet-dominated active
                                                         galaxies
                                                     * This occurs when the relativistic jet points
                                                         close to the line of sight and dominates
                                                         the observed flux which can extend to
                                                         the highest observable energy (TeV!) g-
                                                         rays
                                                     * Jets are common in active galaxies – and
                                                          radiate in radio, optical and X-ray
                                                          wavelengths, but their origin and
                                                          structure are poorly known

 All-sky map from the EGRET experiment               * The correlation of the variability of the X-ray
                                                         and g-ray flux (see below) should be key
                                                         to determine the content of the jet – is it
                                                         particle- or magnetic field dominated?
                                                         (R. Blandford, T. Kamae, GM, …)




Radio, optical and X-ray images of the jet in M 87
   Connection to GLAST: SN remnants as sources of high energy g- and cosmic-rays




  Tycho’s supernova remnant (Chandra X-ray image)   SNR RXJ1713 HESS TeV data, Aharonian et al. 2004

* Some supernova remnants show regions (near the rims) with X-ray spectra that are clearly
    non-thermal as well as strong TeV emission -> relativistic non-thermal particles
* The particle acceleration is best explained as occurring in shocks resulting from
    interaction of SN “blast wave” with the interstellar medium via Fermi process
* This is the best explanation for the origin of the Galactic Cosmic rays
* GLAST should see many such SNR and X-ray data will help in interpretation
* Current work at SLAC/KIPAC is by T. Kamae, S. Digel, J. Cohen-Tanugi, N. Karlsson – see
    the next talk
   Future “non-DOE” projects - overview
• Most imminent is the Japanese-US X-ray / soft gamma-ray
  astronomy mission Astro-E2, which will be launched in 3 weeks (!)
• Several of us (T. Kamae, S. Kahn, GM) are involved in planning of
  the observation program for that mission (and Tune Kamae, the next
  speaker, invented one of Astro-E2 instruments!)
• More in the future, several of us are co-investigators of the Small
  Explorer mission NuSTAR (Fiona Harrison/Caltech, PI; Bill Craig,
  GM are co-investigators) – launch will be 2009
• Locally, we are developing an X-ray polarimeter PoGO for
  astrophysical observations (T. Kamae is the spokesperson)
• We are also co-developing (with ISAS/Tokyo) a detector for
  the NeXT, a planned US/Japanese satellite (likely launch 2013;
  local leader is Hiro Tajima)
                          * The future is (almost) here:
NEAR FUTURE (3 weeks!):
                          Next high energy astrophysics
      Astro-E2
                          satellite, joint Japanese – US
                          mission Astro-E2 will be
                          launched soon
                          * Astro-E2 will have multiple
                          instruments:
                          * X-ray calorimeter (0.3 – 10 keV)
                          will feature the best energy
                          resolution yet at the Fe K line
                          region, also good resolution for
                          extended sources (gratings can’t
                          do those!) - but the cryogen will
                          last only ~3 years
                          * Four CCD cameras (0.3 – 10
                          keV, lots of effective area) to
                          monitor X-ray sources when the
                          cryogen expires
                          * Hard X-ray detector, sensitive
                          from 5 keV up to 700 keV
                    Future projects: Astro-E2
•   Astro-E2 will feature a unique detector, a non-
    dispersive cryogenic detector (running at
    0.6o K) capable of high spectral resolution
    studies of extended celestial sources
•   One of main goals of Astro-E2 is understanding
    the details of clusters of galaxies
•   Clusters are strong X-ray emitters, and the X-
    ray emitting gas must be held in place with
    gravity due to the mass of both luminous and
    dark matter
•   Total content of clusters provides another,
    powerful avenue to determine the cosmological
    parameters, but the physics of clusters (are
    they fully formed, or still assembling from
    individual galaxies?) needs high resolution X-
    ray spectroscopy
•   This high spectral resolution will allow
    measuring the level of turbulence of the X-ray
    emitting gas
An example of a cluster where turbulence should be strong: data from
Markevitch et al. (X-ray data: 2004, 2005) and Clowe et al. (lensing data: 2004)
         A bit further off in the future: NuSTAR
  NuSTAR was recently selected for extended study, with the
     goal for launch in 2009 (Fiona Harrison/Caltech, PI)

It’s the first focusing
    mission above 10 keV
       (up to 80 keV)

brings unparalleled
      sensitivity,
      angular resolution, and
      spectral resolution
    to the hard x-ray band



 and opens an entirely new region of the electromagnetic
  spectrum for sensitive study: it will bring to hard X-ray
astrophysics what Einstein brought to soft X-ray astronomy
                      Hardware details of NuSTAR
NuSTAR is based on existing hardware developed in the 9 year HEFT program
                                                                                Based on the
                                                                                Spectrum
                                                                                Astro SA200-S
                                                                                bus, the
                                                                                NuSTAR
                                                                                spacecraft has
                                                                                extensive
                                                                                heritage.
                                                                                NuSTAR will be
                                                                                launched into
                                                                                an equatorial
                                                                                orbit from
                                                                                Kwajalein.



The three NuSTAR      The 10m NuSTAR                       Orbit              525 km 0° inclination
telescopes have       mast is a direct     NuSTAR          Launch vehicle     Pegasus XL
direct heritage to    adaptation of the    detector
                                           modules are     Launch date        2009
the completed         60m mast
HEFT flight optics.   successfully flown   the HEFT        Mission lifetime   3 years
                      on SRTM.             flight units.
                                                           Coverage           Full sky
                  Science goals of NuSTAR
• NuSTAR’ s improvement in sensitivity of a factor of 1000 over the
  previous missions will be accomplished by the use of focusing hard X-
  ray optics (using multi-coating) - this reduces background dramatically!
• Focal plane detectors will be pixilated CdZnTe sensors
• Precursor to this mission, HEFT, was flown last month with spectacular
  results
• KIPAC will be involved in calibration of the X-ray optics, via funds from
  NASA, mainly at Stanford's main campus (Physics Dept.) but also in the
  interpretation of the data
• The main goals of NuSTAR are:
• (1) to unravel the details of the Cosmic X-ray Background, which is most
  intense at ~ 30 keV, in the middle of NuSTAR's bandpass
• (2) to measure the nuclear lines from elements produced in supernova
  explosions, and
• (3) to provide simultaneous observations of the variable hard g-ray
  sources detected by the hundreds (literally) by GLAST
         NuSTAR goals: Origin of the Cosmic X-ray Background Spectrum



                                         Revnivtsev et al., 2003 RXTE


Slide from
G. Hasinger


                                                           XMM LH resolved
                                                           Worsley et al. 2004




                                                                          data from Gilli 2003
E<2 keV XRB resolved to be a sum of many active galaxies (Chandra, XMM); at E>5 keV still lots of work...
              Heavily obscured AGN “hiding in the dust”:
     Important ingredient of the Cosmic X-ray Background?
•The origin of the diffuse Cosmic X-ray Background is one of the key questions
           of high energy astrophysics research
•Spectrum of the CXB is hard, cannot be due to unobscured AGN (“Seyfert 1s”)
           -> but it (presumably) can be due to superposition of AGN with a broad range
              of absorption in addition to a range of Lx, z


         RXTE PCA + HEXTE data                               Chandra Observatory data




         Example: absorbed (“Seyfert 2”) active galaxy NGC 4945
    New experiment under our leadership: PoGO
•   Another, even more "local" effort (led by Tune Kamae) is an instrument to
    measure the polarization of celestial hard X-ray / soft gamma-ray sources
•   Only one (not very sensitive) X-ray polarimeter was ever flown in space (about
    30 years ago!) and detected only one polarized X-ray source (Crab Nebula)
•   The detector for this experiment - known as PoGO or Polarized Gamma-ray
    Observer - relies on detection of the incident as well as the scattered gamma-ray
    with scintillating material
•   It is a well-type phoswitch detector, where the background can be determined
    and accounted for via anti-coincidence / rise time, and a narrow field of view
•   This experiment will be flown on a balloon in ~ 2008, and is being developed by
    an international collaboration, with funds coming from NASA, Sweden, as well
    as from KIPAC "seed funds"
•   In a 6-hour flight PoGO will measure the change of the polarization angle from
    the Crab as a function of the pulse phase, constraining severely location of
    accelerated particles, responsible for the X-ray/g-ray emission
•   Future, possibly long-duration flights will target a variety of sources such as
    active galaxies and pulsars studied by GLAST, accreting black holes, etc. –
    mainly to learn about the geometry of the emitting region in celestial sources
  Conceptual Design of the PoGO Instrument:
Polarimeter sensitive in the ~ 25 – 100 keV band




            (a)                                  (b)                                  (c)

  Conceptual design of the instrument (number of units will be greater than shown here): a) Isometric
  view; (b) View from the front of the instrument; (c) Vertical cross-section of the instrument. The
  proposed instrument will have ~200-400 units and L1 + L2 in (c) will be ~60cm.
        Design of PoGO: Trigger Strategy
   Trigger and Pulse-Shape-Discrimination: L0, L1, L2




1 inch PMT
                                                Pulse-Shape
 Unit             Detector Assembly             Discrimination
        Crab Nebula in the radio, IR, optical, and X-rays

                                                 * Some supernova
                                                 remnants are powered by
                                                 the rotational energy of
                                                 the neutron star, left after
                                                 the supernova explosion
                                                 (“pulsar”)
                                                 * Good example is the
                                                 Crab Nebula, one of the
Radio                        Infrared            brightest celestial
                                                 sources of X-rays and g-
               Optical                  X-rays
                                                 rays
                                                 * The entire broad-band
                                                 emission from the
                                                 remnant is non-thermal
                                                 * It is best explained as
                                                 synchrotron radiation by
                                                 particles energized by the
                                                 pulsar (crucial test is via
                                                 polarization! – PoGO is in
                                                 the works)
                    Even farther in the future…
•   Future - what are we planning beyond GLAST, Astro-E2, NuSTAR, PoGO?
•   Obvious synergy with SLAC is to use the expertise relevant to particle detectors
    in an astrophysical setting
•   One instrument we are heavily involved in is a med-range g-ray detector, which
    will use a silicon strip tracker to determine the energy and direction of the
    incident photon
•   This detector will provide data in the poorly explored med--range g-ray band,
    with the main goal on understanding the structure of black holes - how is the
    gravitational energy converted into radiation?
•   This instrument, the Soft Gamma-ray Detector is likely to fly on a Japanese - US
    mission NEXT, planned for ~ 2013
•   The Soft Gamma-ray Detector is a joint Japanese - US effort, led at SLAC /
    KIPAC by Hiro Tajima; on the US side, we applied to NASA for funds for
    development
•   Even farther in the future – we are involved in the detector work for EXIST, the
    all-sky hard X-ray monitor under development at Harvard/Smithsonian Center for
    Astrophysics
    Conceptual design and performance of the Soft Gamma-ray
                            Detector




                                                                   Example of a 20 ks observation of
                                                                   the black-hole binary system Cyg X-1,
                                                                   in two spectral states; yellow area
                                                                   is the expected background
                                                100
                                                                                   Abs. mode
                                                                                   Comp. mode
Conceptual design of the SGD
         (one module)
                                    Effective




Bandpass: from ~ 50 keV to ~1 MeV               10                                                 Polarization performance
                                                                                                   of the SGD

                                                 1
                                                      10            100                     1000
                                                           Incident Energy (keV)
     Backup slide: Connection to GLAST: g-rays in
                     perspective


• Any single band
  (g-ray, X-ray, radio,
  optical) is only a
  small part of the
  electromagnetic
  spectrum

• Studying
  astronomical sources
  across all spectral
  ranges can reveal
  very rich physical
  phenomena and is
  necessary for the
  “complete picture”
          Connection to GLAST: jets in active galaxies cont’d
•   Presumably all AGN have the same
    basic ingredients: a black hole
    accreting galaxian gas via disk-like
    structure
•   Some active galaxies contain a
    relativistically boosted jet pointing at
    us: this origin of this jet must be
    connected to the fueling of the black
    hole
•   The correlation of the variability of the
    X-ray and g-ray flux should be key to
    determine the content of the jet – is it
    particle- or magnetic field dominated?
    (R. Blandford, T. Kamae, GM, …)




                                                         Diagram from Padovani and Urry

                                    3C279 data:
                                    Wehrle et al. 1996
Backup slide: NuSTAR Key Parameter Overview

      Energy range                  6 - 80 keV
      Angular resolution (HPD)      40 arcseconds
      FOV (20 keV)                  10 arcminutes
      Strong/weak src positioning   6 arcsec/10 arcsec
      Spectral resolution           1 keV @ 60 keV
      Timing resolution             1 ms

      Focal Length (deployed)       10m
      Spacecraft                    3-axis stablized
      Mission lifetime              3 years
      Orbit                         Near Earth equatorial
      ToO response                  < 24 hours
      Solar angle constraint        20 deg (<10% of sky)
      Observing efficiency (typ.)   65%

				
Lingjuan Ma Lingjuan Ma MS
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