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Evidence for Intermediate Mass Black Holes

Evidence for Intermediate Mass Black Holes. The Case of ESO 243-49 HLX-1. Sean Farrell | Sydney Institute for Astronomy ( SIfA ), The University of Sydney, Australia . In collaboration with: Natalie Webb (IRAP) | Didier Barret (IRAP) | Mathieu Servillat ( CfA ) | Olivier Godet (IRAP).

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Evidence for Intermediate Mass Black Holes

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  1. Evidence for Intermediate Mass Black Holes The Case of ESO 243-49 HLX-1 Sean Farrell | Sydney Institute for Astronomy (SIfA), The University of Sydney, Australia In collaboration with: Natalie Webb (IRAP) | Didier Barret (IRAP) | Mathieu Servillat (CfA) | Olivier Godet (IRAP)

  2. The Case of ESO 243-49 HLX-1 Outline: • The discovery of ESO 243-49 HLX-1 • Confirming the redshift with the VLT • X-ray variability with XMM-Newton, Chandra & Swift • Radio observations with the Australian Telescope Compact Array • The UV/optical/near-IR counterpart with Hubble • Summary & conclusions

  3. The Case of ESO 243-49 HLX-1 • HLX-1 discovered coincident with edge-on spiral galaxy ESO 243-49 (Farrell et al. 2009) • At galaxy distance of ~100 Mpc, max. unabsorbed 0.2 – 10 keV Lx = 1.1 x 1042 erg s-1 • Previous record held by ULX in Cartwheel galaxy: Lx ~ 1041 erg s-1(e.g. Gao et al. 2003) • Large-scale variability with possible spectral state changes observed, ruling out multiple sources (Godet et al. 2009) HLX-1 VLT R-band image of the galaxy ESO 243-49 with the position of HLX-1 indicated by the white circle (Farrell et al., 2009, Nature, 460, 73) Discovery of the Brightest ULX

  4. The Case of ESO 243-49 HLX-1 • Faint (R~24 mag) optical counterpart detected within Chandra error circle(Soria et al. 2010) • Follow-up spectroscopy with VLT detected Hα in emission at redshift consistent with host galaxy (Wiersema et al. 2010) Above: VLT I-band images of ESO 243-49 before (top) and after (bottom) subtraction of the diffuse galaxy light. Right: FORS2 spectra, red = HLX-1, blue = background, black = bkg subtracted Confirming the redshift

  5. The Case of ESO 243-49 HLX-1 • Significant variability by a factor of ~50 observed • Light curve follows Fast Rise Exponential Decay (FRED) profile • Timescale incompatible with thermal-viscous disc instability model • Radiation-pressure disc instability may be possible (physics still controversial; Hirose et al. 2009a,b) • Modulated mass-transfer due to tidal stripping of companion star in eccentric orbit more likely(Lasota et al. 2011) ~380 d? ~380 d Swift X-ray Telescope (XRT) Light Curve of HLX-1 Godet et al. 2009; Lasota et al. (2011); Servillat et al. (2011) X-ray variability

  6. The Case of ESO 243-49 HLX-1 Belloni (2010) Servillat et al. (2011) ~1.0LED ~0.8LED See Poster B25 by Mathieu Servillat ~0.03LED LED ~ 1.1 x 1042 erg s-1, MBH ~ 8,500 M

  7. The Case of ESO 243-49 HLX-1 • HLX-1 observe to transition between high/soft, soft intermediate, and low/hard states • Temperature varies as Ldisc ~ T4, consistent with geometrically thin optically thick disc • Fitting thermally dominated spectra with relativistic models (BHSPEC, KERRBB, KERRDISK) constrains mass to ~103 < MBH < 105 M(Davis et al. 2011; Godet et al. 2011) Thermal plasma contribution from host galaxy nucleus X-ray spectral state transitions of HLX-1 Servillat et al. (2011)

  8. The Case of ESO 243-49 HLX-1 Athena vsXMM-Newton

  9. The Case of ESO 243-49 HLX-1 13-09-10 • Observed HLX-1 with ATCA following transition from low/hard to high/soft state • Detected 40 μJy point source at X-ray position (4.2σ when compared to background flux; Webb et al. 2011) • Follow-up observation ~3 months later failed to detect radio emission • Variability rules out radio nebula • Radio emission most likely associated with jet-ejection event • Using fundamental plane relation (e.g. Fender et al. 2009), mass constrained to < 105 M See Poster B30 by Natalie Webb 04-12-10 Webb et al. (2011)

  10. The Case of ESO 243-49 HLX-1 HST Imaging of HLX-1 In Sept 2010 we obtained HST observations of HLX-1 in 6 bands (Farrell et al. in prep) FUV NUV C H V I H

  11. The Case of ESO 243-49 HLX-1 HLX-1 11 Composite 6-band HST image (Farrell et al. 2011, in prep)

  12. The Case of ESO 243-49 HLX-1 Bkg galaxies VLT FORS2 2-D spectrum HST Near-UV Hα Why Hubble is necessary… HST Far-UV UVOT uvw2

  13. The Case of ESO 243-49 HLX-1 • Fitted HST data with Maraston (2005) simple stellar population models • X-ray spectrum indicates contribution from accretion disc, so treat UV points as upper limits • Age, Z, and Av are degenerate, but SED most consistent with young population • Ages >>100 Myr not consistent with SED Fλ (photons/cm2/s/Å) HST SED fitted with stellar population models Wavelength (Å) Farrell et al. (2011)

  14. The Case of ESO 243-49 HLX-1 Broad-band Spectral Energy Distribution Fitting • X-ray & UV bands described by irradiated disc model • Red optical & H-band data not consistent  need stellar population • Disc temp consistent with ~10,000 Mblack hole • FUV luminosity of 7 x 1039 erg s-1 inconsistent with beamed emission from stellar mass black hole NIR/optical/UV Stellar population X-ray Farrell et al. (2011)

  15. The Case of ESO 243-49 HLX-1 Summary & Conclusions: • X-ray luminosity of HLX-1 varies from ~10 – 400 times Eddington limit of 20 M black hole • Spectral hysteresis observed very similar to Galactic black hole binaries • Transient radio emission from jet ejection event  first detection of jets from a ULX • Mass estimates from Eddington scaling, accretion disc continuum fitting, and jet flare luminosity all support MBH ~ 104 M • Broad-band SED fitting indicates disc emission dominates X-ray & UV bands, with young stellar population accounting for redder emission • UV disc luminosity and disc irradiation rule out beaming • Derived stellar ages inconsistent with globular cluster, instead implying HLX-1 could be nucleus of stripped dwarf galaxy accreted by ESO 243-49

  16. The Case of ESO 243-49 HLX-1 Thank you to all my collaborators: • Natalie Webb, Didier Barret, Olivier Godet, Dacheng Lin (IRAP, France) • Jean-Pierre Lasota (IAP, France/Jagiellonian University, Poland) • Guillaume Dubus (IPAG, France/IAP, France) • Mathieu Servillat, RameshNarayan, Yucong Zhu (Harvard-Smithsonian CfA, USA) • Neil Gehrels (NASA GSFC, USA) • Shane Davis (CITA, Canada) • Tom Maccarone, Christian Knigge (University of Southampton, UK) • KlaasWiersema (University of Leicester, UK) • Claudia Maraston, Janine Pforr (Portsmouth University, UK) • Andrew Gosling, Ian Heywood (Oxford University, UK) • Samantha Oates (MSSL, UK) • Tal Alexander (Weismann Institute of Science, Israel) • Emil Lenc (CSIRO Astronomy & Space Science, Australia)

  17. The Case of ESO 243-49 HLX-1 The Soft Thermal Excess in ULX Spectra For Shakura-Sunyaevα-discs: Ldisk~ Tin4 However, for most ULXs: Ldisk~ Tin-3.5 Soft component for bulk of ULXs most likely from outflow such as disc-wind HLX-1 soft excess varies as predicted for an α-disc Servillat et al. (2011) L vsTdiskof a sample of ULXs from Kajava & Poutanen (2009)

  18. The Case of ESO 243-49 HLX-1 • Black hole binaries emit radio flares during transition from L/H  H/S (e.g. Fender et al. 2009) • Flare radio emission can be ~10 times non-flare luminosity • Applying same scaling to HLX-1 gives M ~104 M, • Radio detection gives conservative upper limit of 105 M Adapted from Merloni et al. (2003) HLX-1 HLX-1 101Msun HLX-1? 102Msun 103Msun HLX-1 104Msun 105Msun 106Msun The Black Hole Fundamental Plane

  19. The Case of ESO 243-49 HLX-1 HLX-1 Composite 6-band HST image (Farrell et al. 2011, in prep)

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