Xray Emission from Ellipticals and Clusters of Galaxies

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X-ray Emission from Ellipticals and Clusters of
Galaxies
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Summary of Results

• Isolated Es SOs have a substantial ISM in hot
  gas ? spatially extended X-ray emission
• Lx 1040 1042 ergs s-1 (in
  E0.5-4.5 keV)
• Tx 107 K
• ne10-3 cm-3
• Mgas 109 - 1010 M

Virgo E NGC 4697 Sarazin 2000
Chandra X-ray Image
optical
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• Groups of Galaxies Clusters of Galaxies have
  hot intra-cluster gas
• Groups Lx 1042 1044 erg s-1
• Tx few x 107 K
• Mgas 1012 1013 M
• Rich clusters Lx 1043 1045 erg s-1
• Tx 107-108 K
• ne 10-2 10-3
  cm-3
• Mgas 1014 M
• Observed out to
  R1-2 MPC
• metallicity 0.4
  solar in Fe

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• -- Emission is thermal bremsstrahlung from
  hydrogen helium
• -- Mgas 10 total mass
• -- Mgas 1-6x M(stars)
• -- X-rays trace gravitational potential in the
  cluster
• -- hot ICM is potentially a large fraction of
  all baryons

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Topics

• X-ray emission tutorial
• X-ray missions instrumentation
• Cluster images ? gravitational potential
• M(gas), M(total)
• Interaction between ICM and galactic ISM
• Abundances
• Cooling flows
• Origin of ICM
• Evolution of ICM with redshift

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X-ray emission tutorial

• Emission is optically thin, free-free (thermal
  bremsstrahlung) continuum collisionally
  excited line emission
• (1) Emissivity for thermal bremsstrahlung (see
  e.g. Rybicki Lightman)

Where ne, ni number density of electrons,
ions gff Gaunt factors
Z charge of ion X-ray spectrum declines
exponentially at high energy Emissivity depends
upon T, which complicates inversion
of Sx to get n Sx n2
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• Collisionally excited line emission
• Prominent lines at T106 -107 K
• At T108 K, only see a complex at 6.7 keV,
• blend of Fe24, Fe25 Ni
• Raymond-Smith Code
• Raymond Smith 1977 ApJS 35, 419
• Made simplifying approximations because in
  1977, X-ray spectra had very low resolution
• MEKAL code (Mewe et al 1995)
• CFA group (Brickhouse et al) Revisions

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Cluster ICM Spectra as a function of
temperature (Raymond-Smith) From Sarazin (1988)
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X-ray Missions

• Uhuru (SAS-1) 1970-1973
• Proportional counters, 2-20 keV
• Spatial Resolution 30 arcmin
• 300 X-ray sources

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Einstein Observatory (HEAO-B) 1978-1981 0.2
3.5 keV IPC (Imaging Proportional Counter)
FOV 75x75, Spatial resolution 1, ?E/E 1
HRI (High Resolution Imager) Spatial
Resolution 2, 25 fov, No energy resolution
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EXOSAT (ESA) 1983 1986 0.05 20 keV
1800 pointings GINGA (Japan) 1987-1991 1x2
deg Proportional Counters 1-37 keV ROSAT
1990-1998 German/US/UK 0.1-2.5 keV
All sky survey pointings PSPC Position
Sensitive Proportional Counter 30 spatial
resopution ?E/E 0.4 HRI 2 spatial
resolution ASCA (Japan) 1993-2000 0.4-10
keV Spatial Resolution 3 Gas Imaging
Spectrometer ?E/E 8 at 5.9 keV BeppoSax
(Italy) 1996-2003 0.1-200 keV
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Chandra (AXAF) 1999- 0.1 10 keV ACIS
CCD Array HRI Gratings 0.5 spatial
resolution very low background
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XMM-Newton (ESA) 2000 EPIC CCD Array
0.1-15keV 6 spatial resolution Grating
simultaneous background flares Astro-E
(Japan) First launch 2000 Astro-E2 launch
2005 Array of microcalorimeters ?E 10eV
Astro E2
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The Future Constellation-X (NASA)
Next big NASA mission after JWST? 4
identical satellites w/ microcalorimeters
High spectral resolution, low spatial
resolution XEUS (ESA) Initially, big
facility built near the space station In
conceptual design phase
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Simulated Con-X observation of a high redshift
cluster of galaxies
A simulated 50 ks observation of a cluster of
galaxies with an X-ray temperature of 4 keV at z
0.8. A Type II supernova abundance distribution
was assumed. The abundances are determined to 10
accuracy for Si, S, and Fe and to 20 accuracy
for Ne and Mg.
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X-ray surface brightness distribution traces the
cluster potential, gives the best measure of
the dynamical state of the cluster
smooth, symmetrical emission ? dynamically
relaxed clumpy, irregular emission ?
unrelaxed, collapsing for first time
e- e- coupling time
e- ion coupling
dynamical crossing time for cluster
sound crossing time
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Selection of Einstein Observatory images
of Clusters (contours) on DSS images
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ROSAT Coma cluster
ROSAT Abell 3328
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ROSAT Large fraction of present-day clusters
are clumpy, i.e. collapsing for first
time ? O low White 1993
Nature 366,429 David, Jones Forman
1995 ApJ 445, 578 Fukugita, Hogan
Peebles 1998 ApJ 503, 518

• Chandra XMM
• ? Wealth of substructure, even in relaxed
  clusters
• Temperature, abundance inhomogeneities
• Holes or Bubbles coincident with radio lobes
• Sharp edges, interpreted as shock fronts

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Abell 2125 Chandra
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Cluster Mass determinations
Fabricant Gorenstein 1983 ApJ 267, 535
Derive the gravitational potential within which
the X-ray gas sits Assume hydrostatic
equilibrium and spherical symmetry
Where the gas pressure
And M(r) mass of galaxy or cluster within
radius r µ mean molecular weight
mH mass of the hydrogen atom
Then
Deproject Sx(r) ? ?gas(r) ? MICM(r) Measure
T(r) ? deproject ? M(r)
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Adopt ß-models to deproject ?gas
Cavaliere Fusco-Femiano 1976
rccore radius
More realistic ? distributions, e.g. Navarro,
Frenk White (1997) CDM halos Give similar
results (Ettori Fabian 1999)
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Analysis of Chandra data for Abell 2052Blanton,
Sarazin McNamara 2003 ApJ 585, 227
Z0.035 cluster with radio source 3C317 in
central elliptical ACIS 36ksec
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X-ray surface brightness and beta model fit
Cooling flow
ß model
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Fe K line
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Tx versus R Solid points deprojected
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M(total)
M(gas)
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Temperature map
Abundance map
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Radio source (contours) Superimposed on X-ray
image