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The Origins and Ionization Mechanisms of Warm Filaments in Cool Core Clusters

The Origins and Ionization Mechanisms of Warm Filaments in Cool Core Clusters. Michael McDonald Postdoctoral Associate - MIT Kavli Institute. In collaboration with: S. Veilleux (UMd), R. Mushotzky (UMd), D. Rupke (Rhodes), C. Reynolds (UMd). Agenda. Introduction

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The Origins and Ionization Mechanisms of Warm Filaments in Cool Core Clusters

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  1. The Origins and Ionization Mechanisms of Warm Filaments in Cool Core Clusters Michael McDonaldPostdoctoral Associate - MIT Kavli Institute In collaboration with:S. Veilleux (UMd), R. Mushotzky (UMd), D. Rupke (Rhodes), C. Reynolds (UMd)

  2. Agenda • Introduction • Multiphase gas, youngstars in cool core clusters • X-ray-Hα correlations • Evidence for ICM cooling • Global vs local influenceson Ha filaments • Hα filaments in the far-UV • Summary & Future Work Structure in Clusters and Groups of Galaxies in the Chandra Era

  3. 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 gascome from? • What is the ionizationsource? Perseus A, Conselice et al. 2001 Structure in Clusters and Groups of Galaxies in the Chandra Era

  4. Motivation & Sample Selection • Potential sources of gas: • Starburst/AGN wind • Stripped from infalling, gas-rich galaxies • X-ray cooling flow • Buoyant radio bubbles • Potential sources of heat: • Cosmic ray ionization • AGN • Young stellar populations • Conduction from ICM • Ionization by ICM X-rays • In order to isolate the source of cool gas and the ionization mechanism, we assembled a sample of cool core and non-cool core clusters. • 33 systems (23 clusters, 10 groups) • Full sample has X-ray (CXO), Hα (MMTF), optical (Magellan), and radio (FIRST/SUMSS) data. Structure in Clusters and Groups of Galaxies in the Chandra Era

  5. A Multiwavelength Database Structure in Clusters and Groups of Galaxies in the Chandra Era

  6. A Multiwavelength Database • Matching spatialresolution at X-ray (fwhm ~ 0.9”), Hα (fwhm~ 0.8”) and FUV (fwhm~0.5”) • Allows a direct spatialcomparison betweenthe hot, warm, andstar-forming phases • Correlation betweenX-ray and Hα morphology • Can properly separatecontributions fromthe nucleus (AGN) andfilaments (Optical) (X-ray) (Ha) Structure in Clusters and Groups of Galaxies in the Chandra Era

  7. RESULTS: X-ray – Ha Correlations THE WARM, IONIZED GAS IS A BYPRODUCT OF THE COOLING ICM! • Only see Hα in cool cores • Hα flux correlated w/ X-ray cooling rate LHα • Hα emission is constrained to within the X-ray cooling radius • Hot ICM is cooling more rapidly inregions w/ Hα emission by an order of magnitude kT (<100kpc) dM/dtspec Rcool (kpc) kTin/kTout nin/nout Kin/Kout tc,in/tc,out RHα (kpc) Structure in Clusters and Groups of Galaxies in the Chandra Era

  8. RESULTS: The Role of Environment • We examine thefrequency of Hαemission versus variousquantities at R2500 • Weak trends withmass, temperature • Stronger trends withgas fraction & entropy • Hα emission seen inlow-entropysystems with highgas mass fraction • The presence of warmgas is more dependenton the core properties than the global properties. kT2500 [keV] M2500 [1013 M] Fraction of Clusters w/ Hα Emission K2500 [102 keV cm2] fgas,2500 Structure in Clusters and Groups of Galaxies in the Chandra Era

  9. RESULTS: Star-forming Filaments STARS ARE FORMING OUT OF THE COOLING ICM AND PHOTO-IONIZING THE COOLING GAS! • 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 LFUV [erg/s/Hz] LHα [erg/s] SFE = SFR/(dM/dt) Structure in Clusters and Groups of Galaxies in the Chandra Era

  10. 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. Structure in Clusters and Groups of Galaxies in the Chandra Era

  11. 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. σv Structure in Clusters and Groups of Galaxies in the Chandra Era

  12. 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 [N II]/Hα Structure in Clusters and Groups of Galaxies in the Chandra Era

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