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

04/18/23 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

04/18/23 Structure in Clusters and Groups of Galaxies in the Chandra Era 4

Potential sources of heat:• Cosmic ray ionization• AGN• Young stellar

populations• Conduction from ICM• Ionization by ICM X-rays

A Multiwavelength Database

04/18/23 Structure in Clusters and Groups of Galaxies in the Chandra Era 5

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

04/18/23 Structure in Clusters and Groups of Galaxies in the Chandra Era 6

A Multiwavelength Database

(Optical) (X-ray) (Ha)

RESULTS: X-ray – Ha Correlations

04/18/23 Structure in Clusters and Groups of Galaxies in the Chandra Era 7

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

04/18/23 Structure in Clusters and Groups of Galaxies in the Chandra Era 8

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

04/18/23 Structure in Clusters and Groups of Galaxies in the Chandra Era 9

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

04/18/23 Structure in Clusters and Groups of Galaxies in the Chandra Era 12

[N II]/Hα