What are the essential ingredients
This presentation is the property of its rightful owner.
Sponsored Links
1 / 80

What are the essential ingredients of ultraluminous X-ray sources? PowerPoint PPT Presentation


  • 78 Views
  • Uploaded on
  • Presentation posted in: General

What are the essential ingredients of ultraluminous X-ray sources?. Roberto Soria (CfA & MSSL). Some ULX collaborators : M Cropper, C Copperwheat (MSSL), R Fender (Southampton), Z Kuncic, C Hung (Sydney), D Swartz (MSFC),

Download Presentation

What are the essential ingredients of ultraluminous X-ray sources?

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


What are the essential ingredients of ultraluminous x ray sources

What are the essential ingredients

of ultraluminous X-ray sources?

Roberto Soria (CfA & MSSL)

Some ULX collaborators: M Cropper, C Copperwheat (MSSL),

R Fender (Southampton), Z Kuncic, C Hung (Sydney), D Swartz (MSFC),

A Goncalves (Paris-M), M Pakull, F Grise’ (Strasbourg), R. Mushotzky (GSFC)


What are the essential ingredients of ultraluminous x ray sources

What we’d like to know about ULXs

  • Mass

  • No direct (kinematic) mass determination yet.

  • Two or three candidates perhaps feasible now.

2) How to gain a factor of ~ 50 in apparent Lx

with respect to stellar-mass BHs

Beamed (microblazars?)

Higher BH mass (IMBHs?)

Not beamed

Super-Eddington luminosity


What are the essential ingredients of ultraluminous x ray sources

Searching for common features

in the ULX population

“Soft-excess” in their X-ray spectra?

Signature of a cool disk? higher BH mass?


What are the essential ingredients of ultraluminous x ray sources

Holmberg II X-1 (Lx ~ 2E40 erg/s)

“soft excess”

Power law (G ~ 2)

kT ~ 0.15 keV


What are the essential ingredients of ultraluminous x ray sources

Holmberg II X-1 (Lx ~ 2E40 erg/s)


What are the essential ingredients of ultraluminous x ray sources

Searching for common features

in the ULX population

“Soft-excess” in their X-ray spectra?

Signature of a cool disk? higher BH mass?

Most bright ULXs (Lx ~ 1E40 erg/s) have it (Stobbart et al 06)

A few do not, pure power-law spectrum (Winter et al 06)

Evidence of IMBHs, M ~ 1000 Msun ?


What are the essential ingredients of ultraluminous x ray sources

“Soft-excess” interpretation is still unclear

See also poster by Soria, Goncalves & Kuncic

Cool disk emission

Smeared absorption lines

in fast, ionized outflow


What are the essential ingredients of ultraluminous x ray sources

Holmberg II X-1 (Lx ~ 2E40 erg/s)

Power law (G ~ 2.5)


What are the essential ingredients of ultraluminous x ray sources

Holmberg II X-1 (Lx ~ 2E40 erg/s)


What are the essential ingredients of ultraluminous x ray sources

Injected spectrum (power-law)

Emerging spectra with absorption

from ionized, fast-moving outflow

(v ~ 0.1 c, nH ~ 3E22)

Models by Goncalves et al.

References:

Gierlinski & Done (2004)

Crummy et al (2006)

Goncalves & Soria (2006)


What are the essential ingredients of ultraluminous x ray sources

“Soft-excess” interpretation is still unclear

See also poster by Soria, Goncalves & Kuncic

Standard disk around IMBH

Cool disk emission

Non-standard disk

Smeared absorption lines

in fast, ionized outflow

More generally: absorption + re-emission + reflection


What are the essential ingredients of ultraluminous x ray sources

Essential feature of X-ray spectra:

Dominated by non-thermal emission

Disk radiates only ~ 10-20% of output accretion power

Most power is efficiently transferred

from disk to upscattering medium (jet/corona)

Disk should be cooler than a standard SS disk

for a given BH mass


What are the essential ingredients of ultraluminous x ray sources

Chilled disk

Cooler than standard disk

because power is drained

from disk into jet+wind+corona

see also Z. Kuncic’s talk


What are the essential ingredients of ultraluminous x ray sources

Chilled disk

Cooler than standard disk

because power is drained

from disk into jet+wind+corona

see also Z. Kuncic’s talk

(Soria & Kuncic, in prep.)


What are the essential ingredients of ultraluminous x ray sources

Searching for common features

in the ULX population

Jets, outflows?

Radio cores: not detectable yet (< 0.1 mJy)

Resolved jets: not detectable yet

Radio lobes: likely detection in a few sources

Energy in lobes >~ 1E52 erg

Size ~ 50-70 pc

Typical fluxes ~ 0.1-0.2 mJy at 5 GHz


What are the essential ingredients of ultraluminous x ray sources

Radio lobes of a ULX

in NGC 5408

(Soria, Fender et al 2006)

Subaru B + ATCA 5 GHz

CFHT Ha + ATCA 5 GHz


What are the essential ingredients of ultraluminous x ray sources

Searching for common features

in the ULX population

Jets, outflows?

Radio cores: not detectable yet (< 0.1 mJy)

Resolved jets: not detectable yet

Radio lobes: likely detection in a few sources

Optical nebulae: observed in many bright ULXs

sizes ~ 50-400 pc

X-ray photoionized or collisionally ionized?


What are the essential ingredients of ultraluminous x ray sources

HST/ACS

Optical nebulae

Jet lobes?

NGC 1313 X-2

(Pakull, Grise & Motch 2006)

ULX

Hot spot?

(hot ring?)

Star

30 pc

MF16 “SNR” + ULX, in NGC 6946

(Swartz et al 2006, in prep)

= 80 pc


What are the essential ingredients of ultraluminous x ray sources

Searching for common features

in the ULX population

Jets, outflows?

Likely to be essential ingredient

but more evidence needed


What are the essential ingredients of ultraluminous x ray sources

Searching for common features

in the ULX population

Young host environment?

Not essential for fainter ULXs (Lx <~ 3E39 erg/s)

Essential for brighter ULXs (Lx >~ 1E40 erg/s)

Only found in spiral & irregular galaxies

“Young” = less than 50 Myr

Donor = OB star transferring gas on its nuclear timescale


What are the essential ingredients of ultraluminous x ray sources

Searching for common features

in the ULX population

Starburst environment?

Some ULXs are in starburst galaxies

(eg, Cartwheel, Antennae, Mice)

Some are in very quiet corners

of nuclear starburst or starforming galaxies

(eg, NGC 7714, M83, M99)

Some are in tidal dwarfs with little star formation

(eg, Ho II, Ho IX)

NOT AN ESSENTIAL INGREDIENT

but some association


What are the essential ingredients of ultraluminous x ray sources

Searching for common features

in the ULX population

Super star-clusters?

Suggested as site of IMBH formation

via O-star coalescence (Portegies Zwart et al; Rasio et al)

But inconsistent with ULX observations

(except for M82 X-1)

Most ULXs found in OB associations or

open clusters, with masses <~ a few 1000 Msun

NOT AN ESSENTIAL INGREDIENT


What are the essential ingredients of ultraluminous x ray sources

Searching for common features

in the ULX population

Colliding or tidally interacting systems?

Galaxy-galaxy collisions

(eg, ULXs in Antennae, Mice, Cartwheel, NGC 4485/90, NGC 7714/15)

Satellite dwarf – galaxy collisions

(eg ULX in NGC 4559)

HI cloud – disk collisions

(eg ULX in M99)

Tidal dwarfs and tails

(eg ULXs in Ho II, Ho IX)


What are the essential ingredients of ultraluminous x ray sources

Searching for common features

in the ULX population

Colliding or tidally interacting systems?

Essential or very important ingredient


What are the essential ingredients of ultraluminous x ray sources

The Antennae

Examples of ULXs

formed in colliding events

NGC 4559


What are the essential ingredients of ultraluminous x ray sources

M99 (Soria & Wong 2006)

XMM EPIC image (0.2-12 keV)

HI contours over R image

LX ~ 2 1040 erg/s

(see poster by Soria & Wong)


What are the essential ingredients of ultraluminous x ray sources

High-velocity cloud collision with M99 gas disk

Only a coincidence?


What are the essential ingredients of ultraluminous x ray sources

Searching for common features

in the ULX population

Low-metallicity environment?

Mounting evidence but no systematic study yet

(eg, ULXs in Cartwheel, Ho II, NGC 4559, NGC 5408, 1 Zw 18)

More massive BH remnants expected from

metal-poor O stars (Mwind ~ Z0.5-0.8)

.

Probably a very important ingredient


What are the essential ingredients of ultraluminous x ray sources

My (biased) conclusions:

I: NATURE OF (MOST) ULXs

Simplest model still consistent with the data:

BH masses ~ 30 – 100 Msun (upper limit of stellar processes)

Age of the accreting systems < 50 Myr (OB donor)


What are the essential ingredients of ultraluminous x ray sources

II: (SPECULATIVE) FORMATION PROCESS

Triggered star formation(eg, ram p from cloud/galaxy collisions)

Dynamical collapse of molecular clumps

(as opposed to turbulent fragmentation)

Fast gas accretion and protostellar mergers

in a dense protocluster core

(clump mass ~ a few 1000 Msun, much smaller than a super cluster)

Massive stellar progenitor, Mstar ~ 200 Msun

if metal abundance is low

BH with a mass ~ 50-100 Msun


What are the essential ingredients of ultraluminous x ray sources

Externally-triggered dynamical collapse

of a molecular clump in the Milky Way

Total mass ~ 1700 Msun

Infall rate ~ 10-3 Msun/yr

Infall timescale ~ 1.7 105 yr

CMM3 has 40 Msun, still accreting & merging

35 Msun

40 Msun

15 Msun

Peretto et al. (2006)


What are the essential ingredients of ultraluminous x ray sources

Very massive stars from clustered

star formation exist in the Milky Way & LMC:

Pistol star: initial mass ~ 200 Msun

(but too metal rich to collapse into a BH)

R145 in 30 Dor: M sin3i= (140 +/- 37) Msun


What are the essential ingredients of ultraluminous x ray sources

III. POWER BUDGET

Accretion rate up to ~ 10 times Eddington

Luminosity near or a few times Eddington

Disk radiates only < 20% of the output power

Disks are cooler than standard SS

Kin. power available for outflows and jets

Can BHs have steady jets when accreting

at or above Eddington?

ULXs could be test cases for QSO super-Edd

accretion and feedback models at high redshift


What are the essential ingredients of ultraluminous x ray sources

A finis si’.

Mersi’ che i l’eve scota’.


What are the essential ingredients of ultraluminous x ray sources

Black hole masses in ULXs

Optical counterparts too faint for direct

mass-function determinations

X-ray Luminosity function cuts off at ~ 3 x 1040 erg/s

Eddington limit suggests M ~ 30 - 200 Msun

Higher masses (~ 103Msun) speculated from

X-ray timing and spectral studies


What are the essential ingredients of ultraluminous x ray sources

BH mass from X-ray spectral models

Galactic X-ray binaries generally show:

power-law component + thermal disk component

Flatter (G ~ 1.5) when LX <~ 0.01 LEdd

Steeper (G ~ 2.5) when LX ~ LEdd

4

4

LX ~ Tin R2 ~ Tin M2

- 4

Lmax ~ LEdd ~ M ~ Tin


What are the essential ingredients of ultraluminous x ray sources

X-ray spectrum of NGC4559 X7 (XMM)

Power-law (G~ 2.3)

Tbb ~ 0.12 keV


What are the essential ingredients of ultraluminous x ray sources

X-ray spectrum of NGC4559 X7 (XMM)


What are the essential ingredients of ultraluminous x ray sources

G ~ 2.0

Disk kTin ~ 0.13 keV


What are the essential ingredients of ultraluminous x ray sources

Disk kTin ~ 1.9 keV

kTphot ~ 0.27 keV


What are the essential ingredients of ultraluminous x ray sources

LX

(erg/s)

1042

1041

Lx = LEdd

Hot-disk model

1000 Msun

1040

1039

15 Msun

IMBH model

GBHs

1038

5 Msun

Tin

0.1

1

0.2

2

(keV)


What are the essential ingredients of ultraluminous x ray sources

IMBH model

Miller, Fabian & Miller (2004)

Feng & Kaaret (2005)

kTin ~ 0.12 – 0.15 keV

M >~ 1000 Msun

LX ~ 0.05 – 0.2 LEdd

Hot-disk model

Stobbart, Roberts & Wilms (2006)

kTin ~ 1.5 – 2.5 keV

M <~ 10 Msun

LX ~ 10 LEdd


What are the essential ingredients of ultraluminous x ray sources

PROBLEMS:

IMBH model

similar to NLSy1

kTin ~ 0.12 – 0.15 keV

M >~ 1000 Msun

LX ~ 0.05 – 0.2 LEdd

requires exotic

formation processes

why do they

never reach LEdd?

Hot-disk model

kTin ~ 1.5 – 2.5 keV

M <~ 10 Msun

LX ~ 10 LEdd


What are the essential ingredients of ultraluminous x ray sources

PROBLEMS:

IMBH model

similar to NLSy1

kTin ~ 0.12 – 0.15 keV

M >~ 1000 Msun

LX ~ 0.05 – 0.2 LEdd

requires exotic

formation processes

why do they

never reach LEdd?

Hot-disk model

kTin ~ 1.5 – 2.5 keV

M <~ 10 Msun

LX ~ 10 LEdd

ad hoc (esp. ~ 10 keV)

standard SS disk should

not survive at 10 LEdd !


What are the essential ingredients of ultraluminous x ray sources

Alternative model: broad absorption

G ~ 2.8


What are the essential ingredients of ultraluminous x ray sources

Summary I

Unwise to estimate BH masses from X-ray spectra

“Soft excess” may be due to absorption

New spectral state? (for ULXs and NLSy1?)

.

Steep pl + absorption

in fast, dense outflow

M

Very high (steep pl)

High/soft (disk)

Low/hard (flat pl)


What are the essential ingredients of ultraluminous x ray sources

ULX radio counterparts: proof of IMBHs?

“fundamental plane” of BH activity

(Merloni, Heinz & DiMatteo 2004; Fender et al 2004)


What are the essential ingredients of ultraluminous x ray sources

Few ULXs have a radio counterpart

M82 (Kording et al 2005)

Holmberg II (Miller, Mushotzky & Neff 2005)

NGC 5408 (Kaaret et al 2003; Soria, Fender et al 2006)

NGC 7424 (Soria, Kuncic et al 2006)

NGC 6946 (Swartz et al 2006, in prep)


What are the essential ingredients of ultraluminous x ray sources

NGC 5408 (zoomed in)

Coincidence between:

X-ray (~1E40 erg/s)

Radio (~ 0.3 mJy at 5 GHz)

Ha(~1E36 erg/s)


What are the essential ingredients of ultraluminous x ray sources

Comparison with X-ray and radio luminosities of Galactic BHs


What are the essential ingredients of ultraluminous x ray sources

However:

Steep radio spectrum (thin synchrotron)

Same value in 2000 and 2004

Marginally resolved (radius ~ 30 pc)

More likely radio emission from lobes, not core

Core = X-rays, flat radio spectrum (if present)

Traces the instantaneous accretion state

Lobes = steep radio spectrum

Trace the integrated jet power over ~ 0.1 Myr


What are the essential ingredients of ultraluminous x ray sources

Radio lobes or supernova remnant?

Not easy to distinguish or disentangle the two

(eg, SS433 has SNR + jet lobes)

Leptonic jet model in NGC 5408:

E ~ 3 1051 erg

PJ ~ 7 1038 erg/s over 1.5 105 yr

Expansion velocity ~ 80 km/s

A SN model (= 99% relativistic protons)

would requireE ~ 3 1052 erg

(A hypernova, perhaps?)


What are the essential ingredients of ultraluminous x ray sources

NGC 7424 (d ~ 12 Mpc)

(Soria, Kuncic, Broderick & Ryder 2006)


What are the essential ingredients of ultraluminous x ray sources

ULX-2


What are the essential ingredients of ultraluminous x ray sources

State transition

low/hard high/soft

5 1038 7 1039 erg/s

(with thermal plasma)

Age = 8 +/- 2 Myr

Point-like (< 60 pc) radio source

Index ~ - 0.6 (thin synchrotron)

LR ~ 3 x Cas A

Radio lobe or young SNR?

(Soria et al 2006b)


What are the essential ingredients of ultraluminous x ray sources

Summary II

We are starting to find ULX radio counterparts

Radio lobes (FR2 microquasars?) or SNR?

Many ULX radio lobes may have been misclassified

as SNRs if the central X-ray source is off

Ratio of ULX radio lobes / “fossil” radio lobes

may give us clues on the X-ray duty cycle

Radio/ULX associations useful to determine

power budget = radiative vs mechanical output

(also important for estimating feedback from early quasars)


What are the essential ingredients of ultraluminous x ray sources

Part III:

speculations on ULX formation


What are the essential ingredients of ultraluminous x ray sources

IMBH formation in a young super-star-cluster?

Dynamical friction

106 Msun cluster

Mass segregation

Runaway core-collapse

1000 Msun BH

Stellar collisions/mergers in the core

Short-lived, very massive star (~1000 Msun)

Hypernova or direct collapse into IMBH

Numerical simulations by Portegies Zwart et al

and by Gurkan, Rasio et al.


What are the essential ingredients of ultraluminous x ray sources

Problem:

most ULXs are not in super-star-clusters

Near OB stars but not inside a bound cluster

Have their parent clusters dispersed?

Tidal disruption: always too slow (>~ 50 Myr)

SN disruption: perhaps….but there are no signs

of the dispersed super clusters

Were they ejected?

Inconsistent with IMBH, would require low BH mass

(eg, Zezas et al 2002; Belczynski et al 2005)


What are the essential ingredients of ultraluminous x ray sources

106 Msun super star clusters

with 1000 Msun BHs

Rarely found

Probably not needed

We only need M ~ 30 -- 200 Msun


What are the essential ingredients of ultraluminous x ray sources

Suggestion:

IMBHs formed in smaller proto-clusters,

not super clusters (Soria 2005)

Ionized gas

protostars

Neutral gas

cluster

t ~ 0.5 Myr

OB assoc

protocluster

(eg, Kroupa & Boily, 2002-2004; Geyer & Burkert 2001)


What are the essential ingredients of ultraluminous x ray sources

sh < 10 km/s

M ~ 103.5 -- 105 Msun

Ideal conditions for

forming progenitor “star” with M ~ 100 -- 300 Msun

dispersing the protocluster (binding energy <~ 1052 erg)

Combination of accretion (large-scale gas inflow)

+ coalescence in the protocluster core?


What are the essential ingredients of ultraluminous x ray sources

Dense proto-clusters ideal for coalescence

Stellar captures and mergers are favoured

by proto-stellar disks / envelopes

Collision cross section enhanced

at low velocity dispersion (gravitational focussing)

Collision rates & maximum BH mass

enhanced at high density

Merging BHs: most difficult

Merging O stars: somewhat easier

Merging protostars, molecular cores: easiest


What are the essential ingredients of ultraluminous x ray sources

Two regimes for coalescence + IMBH formation?

M >~105.5 Msun

M <~ 105 Msun

sh < 10 km/s

sh >~ 10 km/s

tcc <~ 0.5 Myr

tcc <~ 3 Myr

IMBH formation

in unbound proto-cluster

IMBH formation

in bound cluster

ULX in a sparse OB assoc

(size >~ 100 pc)

with expanding gas nebula

ULX in a cluster

(size <~ 3 pc)


What are the essential ingredients of ultraluminous x ray sources

Additional advantage

of the proto-cluster scenario

Same physical process that creates massive

[O + O] binaries, progenitors of BH HMXBs

ULXs = high-luminosity end of HMXBs

up to ~ 100-200 Msun


What are the essential ingredients of ultraluminous x ray sources

Protoclusters

near the Cone nebula

(Peretto, Andre’ & Belloche 2006)

Near-IR contours + 1.2mm continuum


What are the essential ingredients of ultraluminous x ray sources

Peretto, Andre’ & Belloche (2006)


What are the essential ingredients of ultraluminous x ray sources

Two necessary ingredients for a massive BH:

1

Supersonic global inflows in protoclusters

(as opposed to random turbulent motion)

An external trigger may cause

compression and dynamical collapse

2

Small mass loss from progenitor star

before SN core-collapse

Low metal abundance (~ 0.1 solar)

reduces mass loss in stellar winds


What are the essential ingredients of ultraluminous x ray sources

Importance of low metal abundance

Heger et al (2003)


What are the essential ingredients of ultraluminous x ray sources

Galaxy collisions, cloud-disk collisions

(often) starbursts,

large number of

HMXBs

Triggered star formation

Denser protoclusters,

dynamical collapse,

high-mass stars

ULXs, upper end

of HMXB distribution


What are the essential ingredients of ultraluminous x ray sources

Observational evidence for ULXs in SSCs?

ULX in a young super-star-cluster in M82

Lx varying from ~ 1039 to 1041 erg/s

Mbh ~ 1000 Msun Mcl ~ 4 105 Msun

Portegies Zwart et al, Nature, 2004


What are the essential ingredients of ultraluminous x ray sources

Near clusters but not in one

ULX in the starburst dwarf NGC 5408

with Lx ~ 1040 erg/s

Near B stars but not in a cluster

Kaaret et al 2003

Soria et al 2004


What are the essential ingredients of ultraluminous x ray sources

Near OB stars but not in a super-star-cluster

ULX in the dwarf galaxy NGC 5204

Liu et al 2004


What are the essential ingredients of ultraluminous x ray sources

Not in super-star-clusters

ULX in the starburst dwarf NGC5408

with Lx ~ 1040 erg/s

Two ULXs in NGC4559 with Lx ~ 1 – 4 1040 erg/s


What are the essential ingredients of ultraluminous x ray sources

NGC4559 X-10: near OB stars, no super cluster

A few B stars

but no big clusters

Cropper et al 2005

Soria et al 2005


What are the essential ingredients of ultraluminous x ray sources

Antennae: lots of ULXs, displaced from clusters

ULXs are displaced from SSCs by ~ 100 – 300 pc

Zezas, Fabbiano et al 2002


What are the essential ingredients of ultraluminous x ray sources

Massive proto-stellar mergers

proto-cluster disruption

Explosive expulsion of gas

Binding energy of the gas in a 105Msun cluster

~ a few 1050 -- 1051 erg

Single SN releases ~ 1051 erg

Merger of 100 + 100 Msun stars

releases ~ 1051 erg

(Bally & Zinnecker 2005)


What are the essential ingredients of ultraluminous x ray sources

Not in clusters

4 ULXs in the colliding galaxies NGC 7714 / 7715

with Lx ~ 2 – 8 1040 erg/s

2 are in clusters, 2 are not

Smith et al 2005, AJ, 129, 1350


What are the essential ingredients of ultraluminous x ray sources

NGC4559 X-7: near OB stars, no super cluster

A few B stars

but no SSCs

Soria et al 2005


  • Login