Relaxation and Feedback in Clusters of Galaxies

Relaxation and
Feedback in Clusters of
Galaxies
Kenneth W. Cavagnolo
Thesis Defense
Saturday, June 8, 2013

Collaborators
Megan Donahue
Mark Voit
Ming Sun
David Ventimiglia
Gus Evrard

What is a cluster of
galaxies?

NASA / TRACE

Robert Gendler (robgendlerastropixs.com)

NASA / ESA / STScI / AURA

NASA / ACS Team / Benitez et al.

Virgo Consortium / Volker Springel / Klaus Dolag / Splotch

100’s to 1000’s of
galaxies
Few Mpc in size
1013-1015 Msolar
85%-90% dark matter
15%-10% baryons
Most baryons not in
galaxies...
CFHT / Coelum Astronomia / Hawaiian Starlight
Perseus Cluster
Cluster Stats
NB: Mpc ~ 1019 km or ~3 million light years

Intracluster Medium
MACS J1423
Optical: NAOJ / Subaru / H. Ebeling
X-ray: NASA / CXC / IoA / S.Allen et al.

Intracluster Medium
(ICM)
ICM accounts for 75%-90% of
baryons
Hot: ≥ 10 million K
Diffuse: ≤ 10-1 cm-3
Luminous: 1042-1045 ergs s-1
> 1 billion times Lsolar
LQuasars > 1046 ergs s-1

How does ICM emit
X-rays?

Thermal Bremsstrahlung
NASA / CXC / D. Berry

Thermal Bremsstrahlung
23 million K (2 keV) bremsstrahlung spectrum
Flux[keV/cm2skeV]
Energy [keV]

Atomic Line Emission

Galactic
Absorption

Fe L-shell
Galactic
Absorption

Fe L-shell
Fe K-shellGalactic
Absorption

Observing X-rays
Chandra X-ray
Observatory
Angular res. 0.492″
Energy res. ~100 eV
Sensitivity peak ∼1.3 keV

Observing X-rays

“Tale of Two Cooling
Timescales”
Long cooling time (atmospheres)
Cosmology
Relaxation
Short cooling time (cores)
Galaxy Formation
Feedback

Why study clusters?
Cosmology:
Structure growth as tracer
Cluster number density
Dark matter & dark energy
Complications:
“Weighing” clusters
Cluster dynamic state
Abell 1185
CFHT / Coelum Astronomia / Hawaiian Starlight

Reiprich et al., 2002
Importance of Relaxation

Good news:

Good news:
Cluster observables related
directly to mass (assuming
equilibrium)
Relations are well
understood & well modeled

Good news:
equilibrium)
Relations are well
Bad news:

Good news:
equilibrium)
Relations are well
Bad news:
Many clusters are not in
equilibrium/relaxed
Precision cosmology
requires knowledge of
cluster dynamic state
Large dispersion

Mathiesen & Evrard, 2001
Hotter hard-band
temperatures
Line
of equality
Mathiesen & Evrard
2001 suggested metric
for measuring cluster
dynamic state
Spectroscopically
unresolved, cool,
merging subclusters
alter best-ﬁt cluster
“temperature”
Use bandpass
dependent temperatures
as measure of dynamic
state

ME01 prediction is quite simple to test
Broad-band temperature: 0.7-7.0 keV band
Hard-band temperature: 2.0-7.0 keV band
2.0 keV is in cluster rest frame
Deﬁne Hard-band to Broadband Ratio:
THBR =
T2.0−7.0
T0.7−7.0

Temperature Inhomogeneity
Collected clusters
from Chandra Data
Archive
6.5 Msec;
225 observations;
+190 clusters
Two apertures
selected:
R5000
R2500
Central 70 kpc
excised

Single-component
thermal plasma
Fixed absorbing NH
Metal abundance is free
Soft background ﬁt and
included during ﬁtting
Broadband
kTX = 7.4 ± 0.2 keV

Single-component
thermal plasma
Fixed absorbing NH
Cut Spectrum at
2.0rest keV and re-ﬁt

Single-component
thermal plasma
Fixed absorbing NH
Hard-band
kTX = 9.1 ± 0.5 keV

Single-component
thermal plasma
Fixed absorbing NH
Hard-band
kTX = 9.1 ± 0.5 keV
Repeat 190+ times...

SIGNIFICANT
NET SKEWING

SIGNIFICANT
NET SKEWING
Interesting, but is this
related to cluster dynamic
state?

Relaxed and Unrelaxed
Distinguish between relaxed and unrelaxed
clusters using complementary indicators
(A) Presence of cool core: quantiﬁable
using data
(B) Mergers: individual study too time
consuming, consult literature

Assume presence
of cool core (CC)
relates to relaxation
Deﬁne a cool core
cluster:
If Tdec < 1 @ 2σ,
cool core
Otherwise, non-cool
T50 kpc
~Tcluster
Tdec =
T50
Tcluster

CC CLUSTERS
“PREFER”
LOWER THBR

What about merger
systems?
Cull out THBR > 1.1
@ 1σ clusters
Are these mergers?
What of those
unstudied systems?Yepes / Hoeft / UAM

MOSTLY NCC MERGERS;
BUT NOT 1:1
CORRESPONDENCE

Temperature inhomogeneity is detected &
quantiﬁable
THBR “knows” about state of cluster core
Highest THBR values associated with mergers
Calibrate between THBR and relaxation using
simulations?
Is THBR useful tool for quantifying scatter in
mass-observables?

Temperature inhomogeneity is detected &
quantiﬁable
THBR “knows” about state of cluster core
Highest THBR values associated with mergers
Calibrate between THBR and relaxation using
simulations?
Is THBR useful tool for quantifying scatter in
mass-observables?
ASK DAVID VENTIMIGLIA AT HIS DEFENSE?

Galaxy Labs, Inc.:
ICM “records” feedback
Function of black holes /AGN
Star formation in big galaxies
Complications:
Theory & observation don’t
agree on massive galaxy
properties
Details of feedback poorly
understood
X-ray: NASA / CXC / UVic. / A.Mahdavi et al.
Optical / Lensing: CFHT / UVic. / A.Mahdavi et al
Abell 520
Why study clusters?

Importance of Feedback
Zwicky 3146
“The Most Massive Cooling Flow”
Edge et al., 1994
˙M > 1200 M⊙ yr−1
Edge et al., 1994
Let us consider simple
cluster model...
Without heating, models
predict large deposition of
cool gas into core
BCG properties
inconsistent with this
model
AND...

TX <
1
3
Tvirial
Peterson et al., 2001, 2003
X-ray spectroscopy
disproves simple
cooling-ﬂow model
No
gas
Also, not enough
mass in cooled by-
products
Molecular gas
Emission line nebulae
Young stars

Galaxy population also
says there is more to
story
Theory & observation
do not fully agree on
galaxy properties
Massive galaxies too
blue & too bright
All factors point to
halted cooling
Learn about high-z
processes via low-z
feedback in cores
Croton et al., 2006
NO
FEEDBACKWITHFEEDBACK

What could possibly be
heating the cores of
clusters?

X-ray: NASA / CXC / Blanton
Abell 2052

X-ray: NASA / CXC / Wilson & Young
Radio: NRAO
Abell 2052
Cygnus A

Radio: NRAO
X-ray: NASA / CXC / SAO
Radio: NRAO / Greg Taylor
Abell 2052
Cygnus A
Hydra A

Radio: NRAO
X-ray: NASA / CXC / SAO
Radio: NRAO / Greg Taylor
X-ray: NASA / CXC / IoA / Fabian et al.
Abell 2052
Cygnus A
Hydra A
Abell 426

Take a “close to the data” approach:
Study cooling ICM & cluster cores
Better understand feedback
Create broad, varied cluster sample from
Chandra archive
Conduct study of ICM entropy... entropy?

ICM Entropy
Nature.Wallpaperme.com

ICM Entropy
Consider entropy as a
state variable:
dS =
dQ
T

ICM Entropy
state variable:
dS =
dQ
T
Ideal gas equation of state:
P = Kρ5/3

ICM Entropy
state variable:
dS =
dQ
T
Recast using observables:
K =
TX
n
2/3
elec
P = Kρ5/3

ICM Entropy
state variable:
dS =
dQ
T
K =
TX
n
2/3
elec
P = Kρ5/3
True thermo entropy:
s =
3
2
k ln K + s0

ICM Entropy
state variable:
dS =
dQ
T
K =
TX
n
2/3
elec
P = Kρ5/3
dK
dr
≥ 0
True thermo entropy:
s =
3
2
k ln K + s0

DM halo properties and entropy
structure dictate X-ray observables
Shock heating and cooling will alter
entropy distribution
Entropy will retain information about
feedback
Entropy may also hold clues about
how feedback operates
Study entropy in cluster cores…
ICM Entropy

ICM Entropy
Mined Chandra
Data Archive (CDA)
Inspected or
analyzed *every*
cluster obs in CDA
8.2 Msec;
302 observations;
233 “clusters”
Make full-body of
work publicly
available
The ACCEPT Collection

Deriving ICM Entropy
Extract surface
brightness
Emergent X-rays
indicative of gas density:
Assume spherical
symmetry
Deproject emission
Convert surface
brightness to density
ﬀ ∝ ρ2
T1/2

Extract temperature
proﬁle
Minimum three annuli
with 2500 counts each
Fit spectra with single-
component, absorbed,
thermal model
No spectral
deprojection: time
consuming, not
signiﬁcant

2D Maps from Schuecker et al., 2004
Coma Cluster
TX nelec

2D Maps from Schuecker et al., 2004
Coma Cluster
K =
TX
n
2/3
elec

Fit models to K(r):
K(r) = K0 + K100

r
100 kpc
α
K(r) = K100

r
100 kpc
α

Fit models to K(r):
K(r) = K0 + K100

r
100 kpc
α
K(r) = K100

r
100 kpc
α
Repeat 230+ times...

ACCEPT Entropy
Proﬁles

Non-Zero Core Entropy

Entropy proﬁles deviate
from power-law

from power-law
Converge to pure
cooling model at large
radii

from power-law
Converge to pure
radii
Non-zero core entropy
consistent with
episodic heating

from power-law
Converge to pure
radii
Non-zero core entropy
consistent with
episodic heating
Is there more here than
meets the eye?

K0 distribution is
bimodal

Central cooling
time 1 Gyr

Does star formation “know”
about K0?
Select robust tracer like Hα:
UV ionizing radiation from O
and B stars
Turbulent mixing layers?
Conduction interfaces?
Regardless, Hα indicates T ~
104 K gas
Scour the literature…
InstituteforAstronomy/L.Cowieetal.
Feedback-K0 Relations
Abell 1795

Hα loves low
entropy

Entropy
threshold?

Do AGN “know” about K0?
Select robust tracer like radio
emission:
Assumed to be sign of AGN
Radio relics/ghosts, halos,
lobes… mostly AGN related
Query NVSS and SUMSS
Sidestep resolution issues
with redshift cut

Do AGN “know” about K0?
Select robust tracer like radio
emission:
Assumed to be sign of AGN
Radio relics/ghosts, halos,
lobes… mostly AGN related
Query NVSS and SUMSS
Sidestep resolution issues
with redshift cut
NRAO / AUI / Taylor
3C 353

Radio loves low
entropy too!

Entropy threshold
is back

Entropy threshold
is back
Common threshold suggests
common mechanism, like thermal
electron conduction
(Voit et al., 2008)

So where does that
leave us…
Entropy Lifecycle
(speculative)

1045 AGN

NASA / CXC / NRAO / Kraft et al.
Centaurus A
1045 AGN

NASA / CXC / NRAO / McNamara et al.
MS 0735
ConductiveStability
E 1061 AGN

Mergers
1E0657
NASA / CXC / Markevitch et al.

Conclusions
Hard-band to broadband temperature ratio
correlates with cluster dynamic state
ICM entropy properties consistent with AGN
feedback models
Characteristic entropy threshold for feedback
activity

Relaxation and Feedback in Clusters of Galaxies

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