Clusters of Galaxies with Athena
Judith Croston
University of Southampton &
University of Cambridge Institute of Continuing Education
On behalf of the Athena Hot Universe Science Working Group:
Reiprich, Fabian, Ohashi, Pointecouteau, Allen, Ota, Ettori, Pratt, Eckert, Croston,
Sanders, McNamara, Kaastra, Finoguenov + many topical panel members
Athena: the hot and energetic
Universe
•  How does ordinary matter assemble into
the structures that we see today?
•  How do black holes grow and shape the
Universe?
The hot Universe
•  How do baryons in groups and clusters
accrete and dynamically evolve in dark matter
haloes?
•  What drives the chemical and
thermodynamical evolution of the Universe’s
largest structures?
•  What is the interplay of galaxy, supermassive
black holes, and intergalactic gas evolution in
groups and clusters?
•  Where are the missing baryons at low redshift
and what is their physical state?
Athena basics
Current generation X-ray mirrors
Silicon pore optics
X-IFU
•  Large array of multiplexed Transition Edge Sensors
(TES): 5’x5’ FOV, 2.5 eV spectral resolution
WFI
•  Array of DEFPET sensors, 40’ x 40’ FOV
From Ariel V to Athena…
Mitchell+ 1976
Croston, Sanders+ 2013
Evolution of galaxy groups and
clusters
(sub-panel led by Pointecouteau, Allen, Ota)
•  How and when was the energy contained
in the hot intracluster medium generated?
•  When and how were the largest baryon
reservoirs in galaxy clusters chemically
enriched?
•  When did the first collapsed haloes retain
a hot gaseous atmosphere?z
How was the energy contained in
the ICM at low z generated?
How was the energy contained in
the ICM at low z generated?
How was the energy contained in
the ICM at low z generated?
Evolution of chemical enrichment
Courtesy J. de Plaa (in Pointecouteau, Reiprich+ 2013)
The earliest galaxy groups
Fabian et al. 2009
Distinguishing groups and
Inverse Compton emission at
high z – sound familiar?
Astrophysics of galaxy groups and
clusters
(sub-panel led by Ettori, Pratt, Eckert)
•  How do diffuse hot baryons accrete and
dynamically evolve in the dark matter
potential?
•  How and when was the energy in the ICM
generated and distributed?
•  When are where are heavy elements
produces and how are they circulated?
Bulk motions and gas turbulence
Ettori, Pratt+ 2013
Thermodynamics of
cluster outskirts
100ks WFI observation determines kT, Z to within 3% and 18%, respectively
Ettori, Pratt+ 2013
Abundances and SNe yields
Abundances and SNe yields
AGN feedback in galaxy groups and
clusters
(sub-panel led by Croston, Sanders, McNamara)
•  How is the energy from jets dissipated and
distributed throughout cluster/group hot gas
atmospheres?
•  How does feedback operate to regulate gas
cooling and AGN fuelling?
•  What is the cumulative impact of powerful radio
galaxies on the evolution of baryons from the
cluster formation epoch to the present time?
How is the energy from jets dissipated
& distributed?
Measure temperature to <1.5% and velocity broadening measured to
10-20 km/s on scales < 10 kpc in 20-30 nearby systems, and scales of <50
kpc in hundreds of clusters and groups
250 ks X-IFU
observations of
Cygnus A- and
Hydra A-like
clusters (Heinz et
al. 2010)
Velocity, age and
jet power can be
measured from
spatially resolved
line structure
across cavities
and shells.
WFI-simulated core of a cluster at z=0.05, based on simulations of Morsony
+ 2010, applying unsharp masking.
WFI capable of detecting and characterizing ripples and sound waves in
several tens of groups and clusters over wide range of mass and jet power,
allowing mechanical energy to be related to environment and AGN
properties.
Quantifying feedback and cooling
20-ks X-IFU spectrum of the centre of Centaurus cluster. Cooling rate
measurements below 4MK achievable with 500x greater efficiency than
XMM-RGS (based on Sanders et al. 2008)
Assessing jet impact
50-ks WFI (l) and X-IFU observations of Centaurus A: dynamics of strong shocks
in nearby objects can be measured for the first time (vs measured to <10% properties based on Croston et al. 2009)
What is the cumulative impact of radio
galaxies on hot gas atmospheres?
Simulated WFI temperature map for
a powerful radio galaxy driving a
strong shocks in 2keV groups at
z=0.1 (left, 20 ks) – from simulations
of Hardcastle & Krause (2013).
Dynamics and energy input of large
samples will test numerical models of
source evolution, allowing impact on
entropy distributions, scaling laws
etc. to be determined.
Missing baryons and WHIM
(sub-panel led by Kaastra, Finoguenov)
•  Where are the baryons missing from the cosmic
budget at z~0? Do they trace the filaments of
the cosmic web?
•  What is their physical state and composition?
•  How does feedback by galaxy winds and AGN
affect the location and physical state of these
baryons?
Current picture
Nicastro et al. 2013
Athena X-IFU simulation of a filalment seen in emission and absorption (1 Ms)Kaastra,
Finoguenov+ 2013
Get involved!
•  Applications for the Athena science
working groups have been reopened:
http://fs6.formsite.com/ATHENA2028/
form4/index.html
WHIM observing strategies
•  Detection of 200 filaments in absorption (150 from
blazars, 50 from GRB). 15 GRB fields follow-up for
emission. Comparison to SDSS density fields.
•  • Serendipitous detection of WHIM emission in
every >100 ks XIFU observation
•  • 100 ks depth XIFU survey of 1 deg2 (10 Ms) – line
profiles of halos
– Baryons in the calibrated LSS
– Statistical studies of WHIM kinematics
•  – Same strategy as in z~10 QSO Fe-line
tomography. – Identification of X-ray ghosts
•  • Missing metals at z~3 in absorption (GRBs)