The Origins and Ionization Mechanisms of Warm Filaments in Cool Core ClustersMichael McDonaldPostdoctoral Associate - MIT Kavli Institute
In collaboration with:
S. Veilleux (UMd), R. Mushotzky (UMd), D. Rupke (Rhodes), C. Reynolds (UMd)
Agenda
04/21/23 2Structure in Clusters and Groups of Galaxies in the Chandra Era
Introduction The presence of warm, ionized gas has been noted
in the cores of several cooling flow clusters to date.
• Typically radial filamentscentered on the BCG
• Surface brightness istoo high by orders ofmagnitude to be ICMcooling through 104 K.
• Unanswered questions:• Where did the gas
come from?• What is the ionization
source?
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Perseus A, Conselice et al. 2001
Motivation & Sample Selection Potential sources of gas:
• Starburst/AGN wind• Stripped from infalling,
gas-rich galaxies• X-ray cooling flow• Buoyant radio bubbles
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Potential sources of heat:• Cosmic ray ionization• AGN• Young stellar
populations• Conduction from ICM• Ionization by ICM X-rays
A Multiwavelength Database
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Observatory
Obs Type
Wavelength
Source/Ref
CXO Phot+Spec X-ray Archive
HST Phot Far UV McDonald+11b
GALEX Phot Near UV Archive
MMTF Phot Hα McDonald+10,11a,b
MMTF Phot ~ 6700 Å McDonald+10,11a,b
Magellan Spec ~ 4000-8000 Å McDonald in prep.
Keck Spec ~ 4000-8000 Å McDonald in prep.
2MASS Phot Near IR Archive
Spitzer Phot Near-mid IR Archive
Herschel Phot+Spec Mid-far IR McDonald in prep.
CARMA Phot+Spec Sub-mm McDonald in prep.
VLA Phot 1.4 GHz Archive
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A Multiwavelength Database
(Optical) (X-ray) (Ha)
RESULTS: X-ray – Ha Correlations
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LH
α
kT (<100kpc) dM/dtspec
RHα (kpc)
Rco
ol (
kpc)
kTin/kTout nin/nout Kin/Kout tc,in/tc,out
THE WARM, IONIZED GAS
IS A BYPRODUCT
OF THE COOLING
ICM!
RESULTS: The Role of Environment
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We examine thefrequency of Hαemission versus variousquantities at R2500
• Weak trends withmass, temperature
• Stronger trends withgas fraction & entropy• Hα emission seen in
low-entropysystems with highgas mass fraction
• The presence of warmgas is more dependenton the core properties than the global properties.
kT2500 [keV] M2500 [1013 M]
K2500 [102 keV cm2] fgas,2500
Fra
ctio
n o
f C
lus
ters
w/ H
α E
mis
sio
n
RESULTS: Star-forming Filaments
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Ha emission is spatially correlated w/ clumpy FUV emission (HST)
Ha flux is correlated w/ FUV flux and is consistent w/ ongoing star formation
SFR is correlated w/ X-ray cooling rate* average efficiency of ~15% isconsistent w/ Universal baryon fraction
STARS ARE FORMING
OUT OF THE COOLING ICM
AND PHOTO-IONIZING THE
COOLING GAS!
SFE = SFR/(dM/dt)LHα [erg/s]
LF
UV [
erg
/s/H
z]
Summary Warm (104 K), Hα-emitting gas is a byproduct of the cooling
intracluster medium• McDonald et al. (2010)
• Hα mass is correlated with the X-ray cooling rate• Warm gas only seen in clusters with cool cores• Hα filaments live in regions cooling an order of
magnitude faster than surrounding ICM
The presence of multiphase gas is only weakly dependent on the global mass/temperature of the cluster, and strongly dependent on entropy gas fraction• McDonald et al. (2011a)
In ~ 2/3 of cases, the Hα filaments are star-formation-heated• McDonald et al. (2011b)
• Strong correlation between FUV and Hα flux and morphology• Mid-IR, UV and Hα-determined star formation rates are consistent
with a conversion of 15% of the X-ray cooling flow into stars.
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A Sneak Peak… McDonald et al. (2011; in prep)
• Combining long-slit spectroscopy from Keck & Magellan w/ Hα imaging to produce pseudo-2D spectra
• E.g., spatial distributionof velocity dispersion
• Extended, thinfilaments havenarrow emissionlines
• Nuclei and “disturbed”filaments havesignificantly broaderlines.
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σv
A Sneak Peak… McDonald et al. (2011; in prep)
• E.g., spatial distributionof [N II]/Hα ratio
• Filaments with UVemission have low[N II]/Hα ratios
• Nuclei and systemswithout UV emissionhave [N II]/Hα ratiosand UV/Hα ratiosconsistent with fastshocks
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[N II]/Hα