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A Possible New Test of the M BH -  Relation at Globular Cluster Masses

A Possible New Test of the M BH -  Relation at Globular Cluster Masses. Steve Zepf Michigan State University. Collaborators Arunav Kundu Tom Maccarone Katherine Rhode Gilles Bergond Stephen Shih Chris Waters.

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A Possible New Test of the M BH -  Relation at Globular Cluster Masses

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  1. A Possible New Test of the MBH -  Relation at Globular Cluster Masses Steve Zepf Michigan State University Collaborators Arunav Kundu Tom Maccarone Katherine Rhode Gilles Bergond Stephen Shih Chris Waters

  2. MBH -  is a key relation for galaxies. What happens at low masses corresponding to dwarfs and GCs? What does comparison of MBH -  at high and low masses say about relationship between BH growth and galaxy growth? Is the MBH -  relation one of the ways dwarfs and GCs differ? • Dwarfs tend to have too few stars near center for dynamical measurements (radio may be more promising). • GCs better, but still a problem. All Galactic GCs are consistent with MBH = 0 (M15 = 1000 +/- 1000 Msun, 47 Tuc 700 +/- 700 Msun). • Also, no black-hole X-ray binaries in globular clusters, even though many neutron-star XRBs in GCs.

  3. Black Holes and Globular Clusters Are BHs absent in GCs (ejection?,IMF?) or are they hiding? • Well-known handful of LMXBs in extragalactic GCs have LX well above LEdd for a neutron star, based on matching Chandra data for LMXBs with HST and ground-based spectroscopy of GCs (Irwin; Fabbiano & Kim; Kundu, Maccarone, & Zepf). • But…extragalactic GCs are not spatially resolved in X-ray data, thus multiple NS sources possible, even likely (KMZ07). This has been known for a long time. So has a solution (e.g. Kalogera, King & Rasio 2004) – Variability is an unambiguous indicator of a BH, since multiple NSs can’t conspire to vary together. • Nothing really seen in a AR Chandra study (Irwin 2006) but…

  4. A Black Hole in a Globular Cluster! Maccarone, Kundu, Zepf, & Rhode 2007 Nature - LX 4 x 1039 ergs/s LMXB in NGC 4472 - In a spectroscopically confirmed globular cluster - Metal-poor GC, 6.6’ from center (about 4 Re) Why Black Hole? • XMM observations show decrease in soft X-ray flux by a factor of 7 over 10,000s. Rules out multiple NSs! Presence in GC, and thus requirement of LMXB rules out other extant non-BH explanations. • Drop in LX almost all at low energies, suggests eclipsing blackbody emission from inner disk. Ingress time indicates precessing warped outer disk (Shih, Maccarone, Kundu, & Zepf 2007)

  5. XMM time series of NGC 4472 GC BH source, MKZR07

  6. A Black Hole in a Globular Cluster! Maccarone, Kundu, Zepf, & Rhode 2007 Nature - LX 4 x 1039 ergs/s LMXB in NGC 4472 - In a spectroscopically confirmed globular cluster - Metal-poor GC, 6.6’ from center (about 4 Re) Why Black Hole? • XMM observations show decrease in soft X-ray flux by a factor of 7 over 10,000s. Rules out multiple NSs! Presence in GC, and thus requirement of LMXB rules out other extant non-BH explanations. • Drop in LX almost all at low energies, suggests eclipsing blackbody emission from inner disk. Ingress time indicates precessing warped outer disk (Shih, Maccarone, Kundu, & Zepf 2007)

  7. Chandra observation 3.5 years earlier at high luminosity level. Shih, Maccarone, Kundu, & Zepf 2007, MNRAS, submitted

  8. A Black Hole in a Globular Cluster! Maccarone, Kundu, Zepf, & Rhode 2007 Nature - LX 4 x 1039 ergs/s LMXB in NGC 4472 - In a spectroscopically confirmed globular cluster - Metal-poor GC, 6.6’ from center (about 4 Re) Why Black Hole? • XMM observations show decrease in soft X-ray flux by a factor of 7 over 10,000s. Rules out multiple NSs! Presence in GC, and thus requirement of LMXB rules out other extant non-BH explanations. • Drop in LX almost all at low energies, suggests eclipsing blackbody emission from inner disk. Ingress time indicates precessing warped outer disk (Shih, Maccarone, Kundu, & Zepf 2007)

  9. • Separate work of ours using VLT FLAMES multifiber spectroscopy to study kinematics of GC system of NGC 4472. • Two independent fiber spectra of GC hosting the black hole. Spectral resolution R=6000, wavelength coverage 5000Å < λ < 5800Å. • Observed 5031.2 +/-0.3 Å is exactly the expected wavelength for [OIII] 5007 at the GC radial velocity of 1475 km/s. • Line has a FWHM of 4-6 Å, instrumental resolution 0.9Å  Velocity width of 200-350 km/s. • Rules out PNe and implicates BH XRB as the source of the power driving the [OIII] emission. [OIII] 5007 at refdshift of GC! Zepf, Maccarone, Bergond, Kundu, Rhode, & Salzer 2007, APJL, submitted

  10. Where does the line come from and what does it ultimately say about MBH ? [OIII] can either be collisionally or photoionized Possibility #1 – stellar mass black holes with mildly super-Eddington LX drive strong winds (e.g. Begelman, King, & Pringle 2006). This wind will shock into ISM of GC, classic shock solutions work with GC sizes of ~10pc and observed velocity width. Note sub-Eddington IMBHs will not drive such winds (Proga 2007). Possibility #2 – line is photoionized. Velocity width much greater than GC dispersion requires that this happen in accretion disk around BH. May work for IMBHs, although tricky to get enough mass at the right radius to make observed L[OIII] at right velocity. The broad lines seen in Galactic stellar mass BHs are higher ionization species, as expected from the small distance from the BH required to get the observed velocity.  Collisional likely stellar mass BH, photoionized likely IMBH

  11. MBH -  Relation • If the XRB is a stellar mass BH, it is very unlikely an IMBH is in the globular cluster. The BHs are the heaviest objects in the cluster and quickly relax to the center. There they either coalesce or are ejected. In a GC with an IMBH, any stellar mass BHs must spend most of their time in the outer regions of the GC. However, this is exactly *not* where the stellar dynamical interactions that make close accreting binaries with BH primaries occur. • So how to tell if BH XRB is an IMBH or stellar mass BH: • 1. collisional vs. photoionization 2. Imaging size of emission line nebula (10 pc > 0.1”) 2.5. Variability in emission line

  12. Conclusions 1. A black hole is confirmed in one globular cluster. (Maccarone, Kundu, Zepf, & Rhode 2007, Nature, 445, 183) 2. The variability that confirms the BH XRB in a globular cluster appears to be due to a warped accretion disk precessing into the line of sight (Shih, Maccarone, Kundu, & Zepf 2007, MNRAS, submitted) 3. Optical spectroscopy reveals [OIII] 5007 emission from the BH XRB system. May either be collisional or photoionization (Zepf et al. 2007, ApJL, submitted). 4. Collisional ionization would suggest a stellar mass BH, photoionization an IMBH. 5. If it is a stellar mass BH, the GC is unlikely to host an IMBH and would fall off of the extension of the MBH - relation. If it is an IMBH, it is the second confirmed IMBH in a globular cluster (see Ulvestead, Greene, & Ho 2007, arXiv:0704.1458 for G1) .

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