Transcript Document

High energy Astrophysics
Cosmology and extragalactic
astronomy
Mat Page
Mullard Space Science Lab, UCL
15. Cosmology and High
Energy Astrophysics in the
future
Slide 2
15. High energy astrophysics in
the future
• This lecture:
• Future missions and observatories:
– What they are
XEUS+Con-X -> IXO ->ATHENA->ATHENA(+)
SKA
EUSO
Euclid
– What they do
– What they will tell us
XEUS
Slide 3
• X-ray Evolving Universe Spectroscopy mission
• Dreamed up in 1995
• “The future of European high energy
astrophysics”
• Most sensitive X-ray observatory ever
• 2 spacecraft: mirror module separate from
detector spacecraft
Slide 4
Initial concept:
• 6 m2 collecting area at 1 keV
– (c.f. XMM 0.25 m2)
• Spatial resolution of < 2 arcseconds
• Spectral resolution of 1-10 eV between
50eV and 30 keV (better than XMM RGS,
and imaging rather than gratings!)
Slide 5
Growth on ISS
• After initial 4-6 years, the mirror
spacecraft docks with the international
space station.
• New mirror segments added to give 30 m2
collecting area at 1 keV
• New detector spacecraft launched with
the next generation of detectors
Slide 6
Slide 7
Slide 9
New concept
• With space shuttle grounded, space
station was no longer an advantage.
– XEUS looked like a dead turkey :(
• Rapidly rethought!
• New technology mirrors use ‘micropore
optics’, glass with tiny (mirror) holes like
a microchannel plate.
• Much larger mirror now possible for
same weight.
• No ISS assembly required.
Slide 8
Revised concept
2005
Slide 10
Objectives:
• Detecting the first massive black holes
• Finding the first galaxy groups and
tracing their evolution to today’s clusters
• Evolution of the heavy element
abundances
• Absorption line spectroscopy of the
intergalactic medium
What did I think it would do?
Slide 11
• Crucial aspect in my mind is the
spectroscopy.
• Better spectral resolution than XMM with
imaging rather than grating instruments – can
go much fainter
• 100 times the XMM collecting area with
grown mirrors
• Spectroscopy of not just the brightest X-ray
sources.
• We may have been thinking a bit too big – the
observatory is supposed to do everything!
– Americans could have beaten us to some
important parts of the science with Con-X
Slide 12
Constellation-X
Slide 13
Slide 14
Constellation X
• Launch 4 identical spacecraft to build up the
collecting area rather than launching 1 big
spacecraft
• If one goes wrong, the whole mission is only
set back a bit (i.e. it has a high level of
redundancy).
• About 6 times the collecting area of XMM
– more at harder energies
• Similar spatial resolution to XMM
– bit like launching a fleet of XMMs
• < 10 eV resolution from 6-10 keV
Slide 15
What would it do?
• High resolution spectroscopy of Fe lines,
particularly relativistic lines in AGN.
• Absorption lines from the interstellar medium
• X-ray astronomy in general. Bigger and better
than XMM
• Not as big, poorer spatial resolution than
XEUS
Slide 16
XEUS + Con-X merged to become International
X-ray Observatory in 2009
• Large X-ray observatory, launch date ~2025(+).
• Will pick up highly obscured AGN directly from
their X-ray emission.
• Single spacecraft, extendable optical bench,
25m long
• Like a giant XMM-Newton with a cryogenic
spectrometer.
• 2011: US decadal survey didn’t rank IXO high
enough that they are likely to have money for it:
IXO was dead.
• ESA hastily went back to studying a European
only mission.
Slide 17
March 2011: Athena
• Large X-ray observatory, launch date ~2025(+).
• Single spacecraft 12m long – very similar spacecraft
dimensions and layout as XMM-Newton
• Key science objectives: strong gravity (relativistic iron
lines) and detecting distant AGN.
• Like XMM-Newton with a
larger collecting area split
between 2 telescopes and
a cryogenic spectrometer.
• ESA down-selection for L1
mission April 2012.
• Lost out to JUICE.
Slide 18
March 2013 on: Athena+
• The call for science themes for the next 2 large ESA
missions is out: launches in 2028, 2034.
• X-ray community proposed a new large X-ray observatory,
codenamed Athena+.
• 2 m2 collecting area, cryo spectrometer, wide-field imager.
• Spatial resolution will be between 2 and 5 arcseconds.
• Key science will be intergalactic warm gas, outflows from
AGN. “Most of the baryons and the hot Universe” was what
I advocated as the emphasis of the case.
• Announcement November 2013. “Hot and energetic
Universe” theme accepted as ESA’s L2 mission.
• Athena (“+” dropped now) anticipated for launch in 2028
(now only 14 years away, and with 18 years now passed
since original XEUS concept in 1996).
Slide 19
Slide 20
Square Kilometer Array
• Huge array of radio telescopes.
• Earlier design of 30, 200m diameter radio
telescopes now exchanged for design with
hundreds of dishes.
• Will stretch over 8 African countries and into
Australia
• Synthesized aperture of 1000 km
• Collecting area of 106 m2
• Should be able to see 1 deg2 at 0.1 arcsecond
resolution.
Slide 21
Square Kilometre Array
Slide 22
Square Kilometre Array
Slide 23
SKA science
• The dawn of galaxies and the reionization of the
Universe, seen in 21cm absorption and
emission.
• Measurements of gazillions of redshifts using
21cm line to make incredibly detailed
cosmological surveys.
• milliarcsecond imaging of radio galaxy cores
with orders of magnitude better sensitivity
• Supernova remnants in starburst galaxies out to
100 Mpc
• Will generate (and have to process) more data
per year than the entire Earth does at present.
Slide 24
LOFAR right now.
• While SKA is being planned, there is already
a small prototype called the LOw Frequency
ARray (LOFAR).
• Main centre is in Holland, but antennas are
located in other countries as well, including
the UK, to extend baselines and improve
resolution.
• UCL has bought into the observatory,
collaboratively between MSSL and Physics
and Astronomy.
Slide 25
LOFAR central array.
Extreme Universe Space
Observatory (EUSO)
Slide 26
• Experiment to observe ultra-high energy
cosmic rays
• Rather than looking up at the atmosphere
from the Earth’s surface, EUSO looks down
from above the dark Earth
• huge sky area ~ 160 000 km2.
• Images ultraviolet fluorescence from
atmospheric nitrogen in extensive air showers
• Sited on ISS (in original proposal at least).
• Should detect ~1000 events with > 1020 eV
energy per year
Slide 27
Slide 28
What will it tell us?
• Where do ultrahigh energy cosmic rays
come from?
• Are there celestial UHECR ‘sources’?
• Is there a maximum cosmic ray energy?
• Are there high energy cosmic neutrinos?
Slide 29
Just like the
fluorescence
imagers of Auger
observatory
HIRES, AGASA,
etc but from above
rather than from
below
Slide 30
Euclid
• The acceleration of the Universe is a very
puzzling thing.
• What is this ‘dark energy’ associated with
the vacuum?
• Is it Einstein’s cosmological constant?
• A “new” and very big question for
astronomers and physicists.
Slide 33
Euclid
•
•
•
•
•
ESA “Medium” mission selected in October 2011.
Will study dark energy using
Weak lensing
Baryon acoustic oscillations
Carries optical and infrared imaging, infrared
spectroscopy.
Slide 34
Euclid
• Its near-IR imaging will go far deeper than VISTA or
any other ground-based imaging survey because of the
reduced background and lack of atmospheric
absorption. The IR imaging isn’t at HST resolution – it
isn’t for weak lensing, but for photometric redshifts.
• It will also take near-IR spectra of > 107 galaxies to
measure baryon acoustic oscillations.
• Extremely precise tests of dark energy compared to
anything that has come before.
Slide 35
Euclid
• Weak lensing is at the core of
Euclid. In essence, Euclid will
have a wide field optical imager
with spatial resolution similar to
the HST, but with an
exceptionally carefully controlled
point spread function.
• Only a 1.2m telescope, but it will
take HST-like images of at least
half of the extragalactic sky.
• Visible imager consortium led by
Mark Cropper of MSSL.
• Extremely ambitious.
Slide 36
Euclid
• US participation in Euclid has been on and off several
times. Overall, (arguably) not a positive interaction.
• US decadal plan indicated number 1 priority would be
a dark energy mission more ambitious than Euclid to
come soon after – WFIRST.
• But NASA was (is?) in big trouble with the cost overrun
of JWST. It doesn’t look likely that WFIRST will be
launched less than 5 years after Euclid.
• Europe has a really superb opportunity to lead the way
in addressing astronomy’s biggest mystery .
Some key points:
Slide 37
• Athena could identify the first quasars and measure the warm
intergalactic medium (i.e. most of baryons).
• The Square kilometer array could enable super-high resolution
imaging of radio galaxies and measure galaxy redshifts through
21cm line back into the epoch of reionization.
• EUSO (or something similar) could identify what and where the
highest energy cosmic rays come from better than any of its
predecessors.
• Euclid will probe dark energy to a precision much better than
achieved today, to address questions like: is there a
cosmological constant, or is dark energy different?