X-ray Observations of Galaxies&

X-ray Binary Populations of Elliptical Galaxies NGC 4365

G. FabbianoCfA

NGC 3379

Outline

• I. Preamble – X-ray observations of galaxies

• II. XRB populations of elliptical galaxies– Issues & history– Landscape– New results from very deep Chandra

observations

Chandra X-ray Observations of Galaxies

• X-ray source populations• The hot ISM (e.g. the Antennae)

– Plasma properties

– Metal enrichment

– Hot outflows

• Quiescent SMBHs and their environment– BH-galaxy feedback

NGC 4038/9Fabbiano et al 2003

M 83Soria & Wu 2002

The Milky WayWang et al 2002

Hot ISM: the Antennae

• A deep view

Baldi et al 2004astro-ph 0410192

Deep Chandra – diffuse emission

Baldi et al 2006a, b

Hot ISM: the Antennae

• Copious and complex hot ISM– Cooling times 107-8 yrs– Masses 105-6 Msol

• Temperatures in the range 0.3 – 0.7keV – 3-7 times those of the Galactic

hot ISM

• Very high pressures– 10-100 that of solar neighborhood

Hot ISM: the AntennaeSee papers by A. Baldi et al

Spatially variable enrichment

•Red- Fe

•Green – Mg

•Blue - Si

Sub-solar abundanceskT1~0.2keV, kT2~0.6keVVery high abundances

kT~0.3keV

0.4-2 --solar abundanceskT~0.6keV, strong power-law

FeMg

Si

20

5 Ne

Mg

20

Ne

Element ratios in the Antennae (Baldi et al 2006)

Ratios consistent with SNII yields, except for depleted Si

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SNII

SNIa

Superwinds, large scale expansion, formation of hot halos in E galaxies

The Antennae

??M82 The Antennae

Quiescent SMBHs

Why are most SMBH quiescent?

• Similar BH masses to AGN• Much fainter: How faint? • Obscured AGNs?• Lack of fuel?• Low inefficient accretion

state? • Interaction with the ISM

– Fuel– Outflows / feedback– Remnants of past activity?

Tremaine et al 2002

Why are QGN Quiescent (if not absorbed)?

Low Radiative Efficiency Low Accretion Rate?

Observable with Chandra Limited by gas available:Hot and cool ISM, Bondi limit Observable with Chandra

Lx~10-8–10-7LEdd

ADAF: r << 0.1standard disk: r ~ 0.1

Model-dependent:

Lbol = (1-PKE)f LX = r M c2.

Jet power

Bolometric correction

R. Soria

NGC 821: high resolution & long exposures• Isolated E galaxy with old

stellar population• D~24 Mpc• Nuclear SMBH - inactive

– MSMBH = 8.7 107 M

– LEdd ~ 1 1046 erg/s

• First observed with Chandra in 2002 (39~ks, Fabbiano et al 2004)– 11 sources (LX > 1.21038 erg/s)

– Fuzzy, S-shaped central emission

• Nuclear emission?

• Hot ISM to fuel the SMBH?

230 ks - Pellegrini et al 2007a, b

Astrometry, Chandra & Hubble, using GC sources

• S1, S2, S4 are not point-like• S2 is at the nucleus

– LX~61038 erg/s– Point-like AGN

• LX<2.81038 erg/s (0.3-8 keV)

• LX/LEdd<2.510-8

– Hard emission~1.5, NH~NHGal.

X-ray colors consistent with LMXB spectra

230 ks - Pellegrini et al 2007a, b

41 sources within D25

–LX > 31037 erg/s

Bkg AGN

LMXB XLF

Is there hot ISM to feed the SMBH?

• LMXBs, stellar light, diffuse X-ray emission follow each other closely

• Cleaned diffuse emission spectrum consistent with LMXBs

• Diffuse X-ray emission dominated by (or totally due to) LMXBs

Stellar light

• Nucleus fed by cold ISM– Stellar outgassing

• Hot ISM swept away by past nuclear activity?

Is there fuel to feed the SMBH?• Numerical simulations of the hot ISM evolution in NGC821 show

that the bulk of gas is expelled by SN (Pellegrini et al 2007)– Include dark and stellar mass– Stellar mass loss rates appropriate for the NGC821 population– LSN from observed SNIa rates (Cappellaro et al 1999)

• A small accumulation M’~ a few 10-5 M / yr at the nucleus (not enough to build the SMBH)– Lacc~M’ c2~(1-4)1041 erg/s > Lbol (SED)~a few 1039 erg/s– The SMBH is still underluminous!

NICMOS

X-Ray Source Populations

See Fabbiano 2006, ARAA

X-ray Binaries - the main component • HMXB - Young

– Early type star donor– Wind or Roche lobe

overflow– Short lifetimes

~107 yrs

• LMXB - Old– Late type star donor– Roche lobe overflow– Long lifetimes

~109-10 yrs

Neutron star Or

Black Hole

Tracer of star

formation

Tracer of mass

Advantages• External galaxies provide `cleaner’ samples

– Distances uncertain for Galactic XRB – Extinction a major problem

• Associate XRB with stellar populations• Find and study `extreme’ sources

– ULXs

Approaches

• X-ray colors / spectra

• Variability / spectral variability

• Association with optical / radio counterparts

• X-ray Luminosity Functions

An X-ray color-color diagram

Prestwich et al 2003

HMXB

LMXB

SNR

Studying the evolution of XRBs with XLFs

XLF different in different stellar populations

Younger populations, flatter XLFs

M81 - arms

Old disk

M81 – Swartz et al 2003

Willner et al 2004 – Spitzer/UVM81 – Chandra -Tennant et al 2001

Studying the evolution of XRBs with XLFs

XLF different in different stellar populations

Younger populations, flatter XLFs

Belczynski et al, 2004

Comparing observed with synthetic XLFNGC 1569

200 Myr

10 Myrs

The HMXB and LMXB XLF in the Galaxy (Grimm, Gilfanov & Sunyaev 2002)

XLF and Star Formation

• Lx ~FIR correlations in Sc-Irr (e.g., Fabbiano et al 1988; Fabbiano & Shapley 2002)

• XLF ~ SFR in actively star forming galaxies (Grimm, Gilfanov & Suniaev 2003)

– Universal XLF cumulative Slope -0.6

The XLF of the AntennaeZezas et al 2007

Coadded observation

ULX

• 120 sources• Cumulative XLF slope ~-0.5

How do LMXBs form? - Debated since 1975…

• Evolution of native field binaries (see Verbunt & van den

Heuvel 1995)?(Piro & Bildsten 2002, King 2002, Ivanova &

Kalogera 2006) – E.g. semi-detached binaries with

large unstable disks and giant donors

– Recurrent transients (recurrence time >100yr, outburst 1-100 yr)

• Transients [1 + 4 candidates] detected in NGC5128 ( Kraft et al 2001)

• Formation in GCs (efficient two-body encounters; Clark

1975, Katz 1975; Fabian et al 1975)?• Ultra-compact NS-WD binaries

(Bildsten & Deloye 2004)– White dwarf orbiting NS– 5-10 min orbit– Short lifetime 107

– Transient at the LX 1037 erg s-1

– LX < ~2 1038 erg s-1

• High luminosity BH binaries(Kalogera, King & Rasio 2004)

– Should be rare– Possibly persistent (if from capture)

High-resolution imaging, sensitive, time-monitoring

Light-curves, XLFs

Question: Do all form in GC then disperse in the Field (J. Grindlay)?

XLFs -norm. (LX,gal.) driven by stellar mass

Gilfanov 2004

• Similar XLF shapes (LMXBs of M.W., spirals, ellipticals)

• Normalization is function of global stellar massLX(>1037erg/s) = (8.0 +/- 0.5) x 1039 erg/s per 1011 M

• It also depends on the GC content of a galaxy(Kim & Fabbiano 2004)

LX(LMXBs)~M*…but…

LMXBs in GCs• Detected widely with Chandra/Hubble• What makes a GC generate an LMXB?

– Lots’ of discussion (see Fabbiano 2006 ARAA)

– Metallicity (age?) (Red GCs more likely to have LMXBs -see papers by Kundu, Maccarone, Zepf….)

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– Structural Characteristics • denser (), more compact (rc) and higher encounter rate () GC

tend to be X-ray sources (Jordan et al 2004:M87; Sivakoff et al 2007: survey; Jordan et al 2007: CenA)

• ..but there is some controversy…

•We are understanding more aboutLMXB GC formation, but….

•Are GC and field LMXBs different populations?

•Are there any ‘telling’ differences suggesting different evolution?

Texp=337 ks D= 10.6 Mpc LB = 1.3 1010 L

NGC 3379 - Deep Chandra ACIS Monitoring

• Little hot gaseous emission, to optimize faint LMXB detection

N. Brassington, D.-W. Kim, A. Zezas - CfAL. Angelini - GSFCR. Davies - OxfordJ. Gallagher - Wisconsin V. Kalogera, T. Fragos - NorthwesternA. King - LeicesterS. Pellegrini - Bologna G. Trinchieri - Milano, BreraS. Zepf, A. Kundu - MichiganS. Blake - Southampton

LMXBs in NGC3379Brassington et al 2007

• 132 sources • 98 within D25

NGC 3379 - Field LMXB variability• Comparing the 5 observations, ~65% of

(132 detected) sources are variable• Different types of long-term variability

observed, both in flux and spectrum

Variable

NGC 3379 - Transients

• Luminous field LMXB are expected to be transients

• 15/98 sources (~D25) are field candidate transients (+ 3 in GCs)

– 4 on 6 months flares (detected in 1 or two consecutive times)

– 2 on for > 5 years– 7 on for > 2 days– 2 on for > 4 months

• Persistent sources could be transients with on-time >5yr

2001 2002 2003 2004 2005 2006

> 15% of LMXBs are transient

S128

NGC 3379 - Transient S128

• Maximum LX~2 1039 erg s-1 • Spectrum at maximum is unusually hard• Ionized absorber? Eddington-driven

Outflow?• Ultraluminous (ULX) state of accretion

disks?– Soria et al 2007, NGC1365 X-1– Feng & Kaaret 2007, NGC 1313 X-2

• If that’s the case, S128 could be a neutron star binary

High/soft (TD)

Ultraluminous

Low/hard

Very high (SPL)

R. Soria 2007 Increasing

Accretion rate

• The high luminosity XLFs of GC and Field LMXBs are the same (Kim E. et al 2006)– Consistent with (but not proving) similar origin

• Does this similarity extends to lower luminosities?

Field and GC LMXB XLFs

---GC-LMXBs

---field-LMXBs

1038

?

Low luminosity Field and GC LMXB XLFs

GC-LMXB

7 97

17

26

62

0

10

20

30

40

50

60

70

1 2

Exposure Time

No. of sources

LMXB in WFPC2 field

GC-LMXB

• XLFs of GC-LMXB and field-LMXB appear to differ below 1037 erg s-1

• There is a relative lack of GC-LMXBs

• Similar to M31 (Voss & Gilfanov 2007)

detected

expected

30 ks, LX ~21037 337 ks, LX ~21036

LMXB-G

CLM

XB-Field

KMZ 2007

LMXB-Field

LMXB-G

C

M31 NGC 3379

KS test P = 0.2%

NGC 4278

16 Mpc, LB~1.61010L

Chandra ACIS

470 ks

Field and GC LMXB XLFs in NGC4278preliminary results

The GC XLF appears relatively depleted at low LX

Field - 43 LMXBs GC - 37 LMXBs

Why do Field and GC XLFs differ at low LX?

• Do we detect multiple LMXBs in a given GC at the high LX end?– This may artificially deplete the low

luminosity XLF

• NO - variability demonstrates these are single luminous sources

• Are GC BH LMXBs persistent capture binaries?(Kalogera, King & Rasio 2004)

– At these luminosities field LMXBs would be transients, so field XLF depleted

• Sources with LX>1038 erg s-1 vary, but are persistent

• Are low luminosity (<1037 erg s-1) LMXB-GC transient ultracompact binaries ?(Bildsten and Deloye 2004)

– Two transients just above 1037 erg s-1

Different evolution for GC and Field LMXBsand possibly for high and low luminosity GC LMXBs

Summary

• XRB give a direct detection of the end-point of binary evolution in different stellar populations

– With Chandra we now detect populations of XRBs in galaxies– With Hubble XRBs can be associated with stellar and GC counterparts – XRB populations differ depending on the age, metallicity and structural

characteristics of the associated stellar populations / systems– LMXB are formed both in the stellar field and in GCs

• Hot ISM and its metal content are uniquely detected in X-rays– Getting the full picture of the multiphase ISM– Vector for the dispersion of elements outside the parent galaxy

• Active and now Silent nuclear SMBHs can be studied– Accretion processes, fuel– Galaxy feedback