Evidence for Intermediate Mass Black Holes The Case of ESO 243-49 HLX-1 Sean Farrell | Sydney...

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 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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› 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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› 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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› 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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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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› 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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Athena vs XMM-Newton

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› 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


HST Imaging of HLX-1

In Sept 2010 we obtained HST observations of HLX-1 in 6 bands (Farrell et al. in prep)

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Composite 6-band HST image (Farrell et al. 2011, in prep)

HLX-1


UVOT uvw2

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Bkg galaxies

HST Near-UV

Why Hubble is necessary…HST Far-UV


Hα

VLT FORS2 2-D spectrum

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Wavelength (Å)

Fλ

(pho

tons

/cm

2 /s/

Å)


› 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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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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› 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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› 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 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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› 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)

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Composite 6-band HST image (Farrell et al. 2011, in prep)

HLX-1


Evidence for Intermediate Mass Black Holes The Case of ESO 243-49 HLX-1 Sean Farrell | Sydney...

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