Transcript Particle astrophysics and cosmology at SLAC/KIPAC: Activities in high energy astrophysics Greg Madejski

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, highenergy, 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)
* Their mass/number density as a function of
time is an excellent probe of cosmological
parameters – best inferred via X-rays - but this
necessitates sensitive observations requiring
observatories such as Chandra
* This will be covered in more detail by S. Allen
* Gravitational lensing of background galaxies
provides an independent estimate of the cluster
mass, which generally (but not always!) agrees
with the X-ray data
* Much of the cutting-edge work with Hubble is
at KIPAC (Marshall, Allen, Peterson, Bradac, …)
– 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!) grays
* 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
Radio, optical and X-ray images of the jet in M 87
* 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, …)
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)
NEAR FUTURE (3 weeks!):
Astro-E2
* The future is (almost) here:
Next high energy astrophysics
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 nondispersive 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 Xray 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 Xray 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
telescopes have
direct heritage to
the completed
HEFT flight optics.
The 10m NuSTAR
mast is a direct
adaptation of the
60m mast
successfully flown
on SRTM.
NuSTAR
detector
modules are
the HEFT
flight units.
Orbit
525 km 0° inclination
Launch vehicle
Pegasus XL
Launch date
2009
Mission lifetime
3 years
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 Xray 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
Unit
Detector Assembly
Pulse-Shape
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”)
Radio
Infrared
Optical
X-rays
* Good example is the
Crab Nebula, one of the
brightest celestial
sources of X-rays and grays
* 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
Effective
Conceptual design of the SGD
(one module)
Bandpass: from ~ 50 keV to ~1 MeV
Abs. mode
Comp. mode
Polarization performance
of the SGD
10
1
10
100
Incident Energy (keV)
1000
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
Angular resolution (HPD)
FOV (20 keV)
Strong/weak src positioning
Spectral resolution
Timing resolution
6 - 80 keV
40 arcseconds
10 arcminutes
6 arcsec/10 arcsec
1 keV @ 60 keV
1 ms
Focal Length (deployed)
Spacecraft
Mission lifetime
Orbit
ToO response
Solar angle constraint
Observing efficiency (typ.)
10m
3-axis stablized
3 years
Near Earth equatorial
< 24 hours
20 deg (<10% of sky)
65%