evidence for intermediate mass black holes the case of eso 243-49 hlx-1 sean farrell | sydney...
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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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The Case of ESO 243-49 HLX-1
› 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
Outline:
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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)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
HLX-1
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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
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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)
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
~380 d? ~380 d
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The Case of ESO 243-49 HLX-1
Belloni (2010) Servillat et al. (2011)
~0.03LED
~0.8LED
~1.0LED
LED ~ 1.1 x 1042 erg s-1, MBH ~ 8,500 M
See Poster B25 by Mathieu Servillat
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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)
PLACE CHART HERE
X-ray spectral state transitions of HLX-1
Thermal plasma contribution from host galaxy nucleus
Servillat et al. (2011)
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The Case of ESO 243-49 HLX-1
› 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
13-09-10
04-12-10
See Poster B30 by Natalie Webb
Webb et al. (2011)
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FUV NUV C
V I HH
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)
UVOT uvw2
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Bkg galaxies
HST Near-UV
Why Hubble is necessary…HST Far-UV
The Case of ESO 243-49 HLX-1
Hα
VLT FORS2 2-D spectrum
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Wavelength (Å)
Fλ
(pho
tons
/cm
2 /s/
Å)
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
HST SED fitted with stellar population models
Farrell et al. (2011)
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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
Farrell et al. (2011)
Stellar population
X-ray
NIR/optical/UV
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The Case of ESO 243-49 HLX-1
› 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
Summary & Conclusions:
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The Case of ESO 243-49 HLX-1
› 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, Ramesh Narayan, Yucong Zhu (Harvard-Smithsonian CfA, USA)
› Neil Gehrels (NASA GSFC, USA)
› Shane Davis (CITA, Canada)
› Tom Maccarone, Christian Knigge (University of Southampton, UK)
› Klaas Wiersema (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)
Thank you to all my collaborators:
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L vs Tdisk of a sample of ULXs from Kajava & Poutanen (2009)
The Case of ESO 243-49 HLX-1
The Soft Thermal Excess in ULX Spectra
For Shakura-Sunyaev α-discs: Ldisk ~ Tin
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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-discServillat et al. (2011)
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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
The Black Hole Fundamental Plane
HLX-1
106 M sun
101 M sun
102 M sun
103 M sun
104 M sun
105 M sun
HLX-1
€
Log(LX ) =1.41Log(LR ) − 0.87Log(MBH ) − 5.01
HLX-1?
HLX-1
Adapted from Merloni et al. (2003)