European X-ray Calorimeter Utrecht, 25-26 October 2004
(Some) astrophysical drivers for ahigh-resolution imaging X-ray
spectrometerXavier Barcons
Instituto de Física de Cantabria (CSIC-UC)
European X-ray Calorimeter Utrecht, 25-26 October 2004
Science context
• The missing baryons: studies of the Warm and Hot Intergalactic Medium (WHIM)
• Black hole growth rate and spin evolution: measurement of the Fe line profile at different redshifts
• Accretion disk precession: binary black holes?
European X-ray Calorimeter Utrecht, 25-26 October 2004
The Warm and Hot Intergalactic Medium
European X-ray Calorimeter Utrecht, 25-26 October 2004
Main goals of WHIM studies
• Measure baryon density as a function of z (missing baryons), comparing with cold (Lyman- cloud) component.
• Chemical evolution of the Universe (groups/clusters and strong systems).
• Heating mechanisms (photoionisation, gravitational heating etc.)
• Determine cosmological distribution (filaments)
European X-ray Calorimeter Utrecht, 25-26 October 2004
The Warm & Hot IGM
• Large fraction of baryons at T~105-107 K
• IGM hotter towards low redshift (baryons falling onto potential wells)
• Extra heating might be present due to star formation & AGNs Davé et al 2002
European X-ray Calorimeter Utrecht, 25-26 October 2004
Thermal history of WHIM
Davé et al (2001)
European X-ray Calorimeter Utrecht, 25-26 October 2004
T and ion column density(Fang, Bryan & Canizares 2002)
European X-ray Calorimeter Utrecht, 25-26 October 2004
The expected column density distribution
Fang & Canizares (2000)
Expect tens of O-VIIIabsorbers per unit z with
N>1015 cm-2
European X-ray Calorimeter Utrecht, 25-26 October 2004
Doppler parameters: thermal width and turbulence
•Typical Doppler paramb~100-200 km s-1
•Larger values for stronger systems (groupsand clusters)
Fang, Byan & Canizares 2002
European X-ray Calorimeter Utrecht, 25-26 October 2004
Sensitivity: equivalent width detection limit
Rule of thumb:
For a S/N>10 spectrum, sampled to 2-3 channelsper resolution element, narrow absorption lines canbe detected with an equivalent width as small as a fraction of a channel width.
EW 0.1 eV (5 mA@ 0.5 keV) is a realistic limit for XEUS, if equipped with a
1eV-resolution spectrograph
European X-ray Calorimeter Utrecht, 25-26 October 2004
Sensitivity:expected S/N ratio
S(0.5-4.5)=10-13 cgs:10 sources/deg2
<z>~ 0.5-1.0
XEUS+STJ=2, NHI=2 1020 cm-2
Resolution ~1 eV
Exposure time ~ 100 ks
No background
European X-ray Calorimeter Utrecht, 25-26 October 2004
Sensitivity
Curve of growth for OVIII
2 eV1 eV½ eV
European X-ray Calorimeter Utrecht, 25-26 October 2004
Fe line diagnostics in distant AGN
European X-ray Calorimeter Utrecht, 25-26 October 2004
Lockman Hole800 ks XMM-Newton observation
XEUS should be able to determine redshifts and study Fe lines individually
Average rest-frame spectra show relativistic Fe-lines
type-1 AGNEW~700eV
Streblyanskaya et al., 2004
type-2 AGNEW~500eV
European X-ray Calorimeter Utrecht, 25-26 October 2004
Fe line profile in distant AGN
• A relativistic Fe line profile provides information on the innermost parts of the accretion disk and, eventually, on the SMBH itself (spin)
• Assume:– Concurrence cosmology
– L(0.5-2)=1044 erg s-1, =1.9
– Laor profile, incl=30º, Rmin=10, Rmax=400, =2.
– EW=300 eV
– 1 Ms exposure
European X-ray Calorimeter Utrecht, 25-26 October 2004
z=1 z=2
z=3 z=5 Spectralresolution
European X-ray Calorimeter Utrecht, 25-26 October 2004
Evolution of SMBH spin
• Fe line profile potentially testable out to z~3-5 for typical type 1 AGNs, but requires long exposures
• NFI’s can do better than WFI, but only one object at a time.
• Study of samples to that level of detail very unlikely
European X-ray Calorimeter Utrecht, 25-26 October 2004
Binary SMBHsand disk precession
European X-ray Calorimeter Utrecht, 25-26 October 2004
XEUS tests of binary SMBHs
• Super-massive Black Holes in galaxy centres + mergers implies binary SMBHs.
• Evidence from long-term variability in the BL Lac OJ 287 (Sillanpää et al 1988) and others.
• Binary SMBHs might be stable over very long periods (Valtaoja et al 1989)
Mergers might play animportant role in SMBH
growth along cosmic history
European X-ray Calorimeter Utrecht, 25-26 October 2004
Jet precession in 3C273
• Jet precession from VLBI long-term monioring (Abraham & Romero 1999)
Model fitsto 16 year Jet precession
European X-ray Calorimeter Utrecht, 25-26 October 2004
A binary SMBH in 3C273?
• Romero et al (1999) find that the jet precession does likely arise from precession in the accretion disk.
• Effects on the Fe line profile:– Azhimutally averaged
– Orbital period ~105 s
Incl=8º-14º
Incl=56º-62º
European X-ray Calorimeter Utrecht, 25-26 October 2004
Accretion disk precession
• Causes:– Binary SMBH, one dominating X-ray emission.
– Non-aligned SMBH spin and accretion disk axis not aligned Accretion disk precession due to the close SMBH
• The relativistic Fe emission line will change as a result of a change in inclination angle:– Shape (especially blue edge)
– Intensity
European X-ray Calorimeter Utrecht, 25-26 October 2004
Simulations
• L(2-10)= 6.25 x 1045 erg s-1, =1.6, z=0.158
• Fe line with EW=200 eV (Yaqoob & Serlemitsos 2000)
• Simulations with various inclination angles and BH angular momenta (Schwarzschild and maximally rotating Kerr
• Disk emissivity profile r-2.5
European X-ray Calorimeter Utrecht, 25-26 October 2004
XEUS/TES vs CONX/Calorimeter100 ks, inclination angles separated 4º
Sharp blue edge of Fe lineStrongly dependent on inclination
European X-ray Calorimeter Utrecht, 25-26 October 2004
Results
• XEUS/TES delivers inclination angle with precission 0.3º (90% confidence) in 100 ks.
• CONSTELLATION-X/2eV delivers inclination angle with precission 1º (90% confidence) in 100 ks.
• Spectral resolution essential• Effective area necessary to test fainter
sourcesSee Torres, Romero, Barcons & Yun (2004, ApJL, astro-ph/0308300)
European X-ray Calorimeter Utrecht, 25-26 October 2004
Do we need a CIS for this science?
• Imaging spectrometers– Point and extended
sources
– Degraded redshift sensitivity
– High efficiency
• Gratings– Point sources only
– Flat redshift sensitivity (/~constant)
– Moderate efficiency
High spectral resolution certainly needed in thefull 0.2-8 keV bandpass: 2 different instruments
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