Download Summary of Talks at Growing Black Holes 2004 in Garching

Summary of Talks at Growing Black Holes 2004 in Garching
Session I Observations of SMBH in the Local Universe
1. Ralf Bender (USM/MPE Garching)
SMBH in Galaxy Centres
 ca. 40 Massive Dark Objects (MDOs) confirmed today
 but only for MW, NGC 4258 ( 3.9+-1.0e7) and possibly M31(9e7) SMBH nature
 principal methods: stellar velocity dispersion, gas dynamics, maser dynamics,
reverberation mapping, eccentric disks
 bulge-less S0 galaxies : no SMBHs ??  upper limit for M33 : 1500 M_sun
 anti-hierarchical formation : luminous AGN grew fast at high redshift, less luminous
AGN grew fast at lower z
2. Aaron Barth (California Institute of Technology) Intermediate-mass BH in Dwarf
Galaxies
 Is there a lower limit for the dark halo mass below which no MBH forms ?
 Problem : r_influence < 0.003’’ for sigma=40 km/sec and M_BH=e5
 using AGN activity : best case NGC4395 (Sd) sigma<30 km/sec and M_BH<e4..5
 Greene and Ho (astro-ph/0404110) : SDSS approach
 z<0.35 (Halpha still detectable)
 3200 Halpha broad emission line objects (all real Seyfert1)
 19 galaxies with M_BH < e6
 problems : sigma(SDSS)=70 km/sec only !
 LLAGN searches favour most active members of group
 preliminary results : 5/7 objects with sigma<60 km/sec fit onto M-sigma
relation
3. Stefanie Komossa (MPE Garching) Observational Evidence for Stellar Tidal
Disruption Events and SMBH formation
 Capture and disruption of Stars as mode of growing black holes (compared to
accretion and BH-BH mergers)
 observational evidence in NON-ACTIVE galaxies conspicuous X-ray flares (4 also
known in AGN, but nature not clear)
 examples :
NGC 5905 : soft X-ray flare of almost AGN luminosity, rapidly fading over
timescale of months
 RXJ 1242-1119 : point-like X-ray flare with an excess of a factor of 90 over
the B-band lum for the host, still fading and is down by x1500 from the peak
 common light curve with L = t^-5/3 ??
4. Guinevere Kauffman (MPA Garching) Accretion onto BH in the Local Universe
(SDSS view)
SDSS work on BH in the local universe :122,808 galaxies (14.5 < r < 17.77) from the
‘main’ galaxy sample
 Blanton et al 2003 show that the SDSS galaxy population is bimodal in color-color
space, clustering properties and structural parameters such as surface brightness vs. mass.
Also in stellar age as f(mass, structure), using the 4000A break and H delta indices.
Division represents blue and (old) red galaxies.
 In physical terms, the break is at 3e10 solar masses in stars, circular velocities of 120
km/s, concentration C=R90/R50=2.6
 In SDSS, they searched for weak emission features through a careful fitting and
removal of the stellar absorption features (which also yielded info. on the stellar
population/M-L-ratio and age properties). Thus they could infer the star formation
history.
Once they obtained emission-line strengths, they used the BPT diagram to classify
normal galaxies, LINERs, and AGNs. They had to allow for the contribution of the
stellar population, which they did by using [OIII] luminosities as a proxy of AGN
luminosity.
 Statistics : Overall fraction of AGN in the sample >50% for nearby L* galaxies at low
redshift. Fraction declines toward higher z (because of increasing stellar contamination
in the 3 arcsec fiber?)
 The AGNs are similar to the red galaxies in terms of structural properties. In terms of
stellar populations, the weak AGNs are like the old red galaxies, while the strong AGNs
have younger stellar populations. The hosts represent the high mass tail and high
concentration C (see above) tail of the population.
 Transformation to more physical quantities by assuming L([OIII]) to L(Bol) using
relation for Type 1 AGN, allowing for the unified model and star formation in the galaxy.
They use D4000/Hdelta to estimate a SFR from relations for normal galaxies. SigmaM_BH from Tremaine et al.
 Finding : lower mass black holes are the ones that are more active at the present time.
Characteristic BH mass overall in their sample is 1e8 solar masses. Furthermore, the low
mass BHs are growing faster at the present time (because they are more active).
(DOWNSIZING of BH growth)
 Volume averaged star formation rate is 1000 times the accretion rate on BHs. This
implies that even at the present day, SFR and activity rate are linked. The growth times
of both activities track each other closely. (meaning : also SFR has down-sized ?).
 For low mass BHs (1e7) half of the accreted mass comes from objects radiating within
factor of 3 of the Eddington limit. However, such objects are rare, 0.1% of the total BH
population  Implication : bright phase/duty cycle lasts about 1e7 years.
 Large-scale structure. Star-forming galaxies occur in lower-density regions. Similar
results for the AGNs. Stronger activity in lower-density regions. Thus the powerful
AGN fraction is higher in low density environments.
 Conclusions:
-
AGN live mostly in galaxies with M>1e10 solar masses.
-
AGN are in galaxies with structure similar to early-type galaxies.
-
LLAGN have stellar populations s similar to normal early-type. High-lum.
AGNs have much younger stellar populations and significant fraction have
recent starbursts.
-
LLAGN are more strongly clustered than high-lum AGNs.
5. Smita : Black hole growth and BH mass – bulge relations of AGNs.
 She starts with the BH – bulge relations of vel. disp. and mass. How did this arise and
does the relation for normal galaxies apply to AGNs?
 How do NLS1s relate to the normal AGN population? They seem to fall well below
the normal BH mass – sigma relation. Why ?

Do the BH masses for normal AGNs and NLS1s follow the same
relations? Apparently so.

How about the use of [OIII] as a surrogate? It seems to give similar
results for BLS1s and NLS1s. One does have to worry about the FeII
subtraction and [OIII] asymmetries in NLS1s, but they seem not to
affect the mass estimates.

Thus narrow and broad-line objects do occupy distinct regions in the
M_BH – sigma plane.
 She finds that BH growth occurs during accretion phase in well-formed bulges. The
accretion rate starts high and declines with time. AGN approach the normal BH mass –
sigma at the end of the active phase. Some NLS1s lie close to the standard M sigma
relation.
 Separately, with Rik Williams work, they can divide the NLS1 objects according to
accretion rate, and some of them (the ones near the standard M-sigma relation) have low
accretion rates. Conversely, the NLS1s with high accretion rates lie below the standard
M-sigma relation.
 This should all be checked with more direct estimates of sigma, e.g., from the CaII
triplet, CO bandhead, or the fundamental plane relations. Also, should find the locus of
NLS1s on the mass-bulge luminosity plane.
 Niel asks if low and high accretion NLS1s are different at E < 1keV. She says yes
(low sigma NLS! Have lower alpha_x ??) Are there differences in their environments?
Not known, yet.
(Then Julian gets into it. Trumper correctly suggests they discuss the question over
lunch.)
6. Thomas Boller (MPE Garching) Measuring masses and accretion rates in rapidly
growing young NLS1s
Extension of Tanaka’s work.
 Typically, NLS1s accrete at super-Eddington rates. NLS1s have significant soft X-ray
excess at low H_beta FWHM. This is reminiscent of what happens in XRBs. He says
that XMM spectra of 1H0707-495 and IRAS13224-3809 have both soft X-ray excess and
a steep drop at higher energies than 7keV (due to neutral Fe absorption?). But no Fe
Kalpha emission.
 Partial covering factor? Further observations showed that the 7 keV drop moved to
higher energies with time in the former objects and occurred at 8 keV in the latter object.
This could be due to high velocity outflow or ionization effects.
 Their estimates show that NLS1s have moderate super-Eddington accretion rates (1020).
 Model of evolution for such a situation :
-
FWHM of the emission lines should increase significantly.
-
Furthermore, the ionizing continuum decreases (?) (thus leading to the soft Xray excess, (which should decline with time?).
-
Then the soft and hard power-law indices should decrease with time.
-
Furthermore, FeII emission should decrease with increasing time.
Simple picture : Assume all galaxies go through an AGN phase. Start with a 2e6 solar
mass BH. They find that a 0.1 solar mass/yr accretion rate will lead to a broad emission
line (8000 km/s) in about 1e8 yrs, thus turning NLS1s into BLS1s. This would also lead
to high-velocity outflows. Such high accretion rates imply that they live in gas-rich
environments.
 Note that a constraint for this approach is that the results not violate the X-ray
background. We do not know the accretion-rate history of NLS1s, which is also subject
to the same constraint.
 Suggests we should improve the NLS1 definition by basing it on physical parameters
(e.g. normalized accretion rate, m/m_dot)
 Q : Do all galaxies start with NLS1 phases ?
Session II Observations of SMBH at higher redshift
7. Xiaohui Fan (University of Arizona) The highest redshift quasars
 Exponential decline in #density with increasing z (<1 Gpc^-3 at z>6)
 M_BH 10^8..10 M_sun and M_Halo 10^13 M_sun : remarkably early in cosmic
history !
 Shape of luminosity function : low z -> ‘downsizing’ of BH activity (is this a
luminosity or an evolution effect ?) ; high z ? -> proposition of SDSS^2 (Southern Deep
Spectroscopic Survey) to find of order 100 (??) QSO at z>31
 Complete Ly alpha and beta absorption trough in 5 of 6 quasars with z > 6.1 = end of
reionisation epoch. Based on best estimate of high-z lum function, UV photons from
quasars are not enough to ionize universe, contribution from starbursts necessary
 Clustering. Tells us about bias factor of quasars and info. about DM halo. Also leads
to estimates of quasar lifetimes. At z < 2.5, SDSS clustering scale is about 7 Mpc. There
is now preliminary, tentative evidence for correlation length to increase with redshift.
 Spectra of emission lines in high z quasars & Continuum shape consistent with lower
z objects -> implication : rapid chemical enrichment near the quasar itself (although not
necessarily in the galaxy farther out). NV emission implies multiple generations of star
formation. Fe II emission might be from metal-free Pop III stars.
 BH mass estimates. Work of Vestergaard and Dietrich/Hamann shows the existence
of high-mass BHs at z=4. This implies very early formation of massive BHs in the
universe. The work of Fan et al. and McLure on the large samples implies that there may
be an upper limit of a few 1e10 solar masses. Interestingly, the most massive objects
don’t seem to have the highest accretion rates (rel. to Eddington).
 He points out that ALMA and Spitzer will give us the best way to study the dust in
high-z quasars and thus a way to probe the assembly of the objects. (at 100 microns AGN
contribution relatively unimportant, thus we see the host galaxies’ light).
With
equipment to date (IRAM and SCUBA) about 40% of radio-quiet obj. at z>4 are
detected at 1mm at 1 mJy level. Implies dust w. mass of 1e8 m sun or more and a high
SFR. E.g., the z=6.43 quasar has been detected, with an apparent dust mass of 1e8 to 9,
H_2 mass of 1e10, and SFR of 1e3/yr.  Conclusion : QSOs very likely to be sites of
massive SF.
-> High resolution CO observations of the object resolve it spatially into two peaks. It
also resolved in velocity space, with a CO line width of 280 km/s and a bulge mass
estimate of 1e10 solar masses within 2kpc, which is lower than expected from M sigma
relation. Is this object not fully assembled (into stars)? Did the BH form early?
 Summary : Strong evolution from z=3 to 6, relatively flat LF, quasars don’t do
reionisation, some evidence of clustering strength increasing with z, but no spectral
evolution with z. Evidence for high mass BHs at z=6. Is there an upper limit? Strong
star formation accompanies quasar (1000 solar masses/yr)
 Next – what is environment and nature of host galaxies for quasars at z>5? Spitzer,
ALMA. Expectation that first high lum quasar appeared at z=8-10
8. Niel Brandt (Penn State) : X-rays from the first massive black holes
 Now more than 100 X-ray obs. of quasars w. z>4.
 4-10 ksec observations with Chandra are sufficient for many purposes.
www.astro.psu.edu/users/neil/papers/highz-zray-detected.dat.
See
 There are 5 RQQ objects at z>4 with good X-ray spectra : No evolution in gamma
with redshift for RQQs, although there is considerable scatter. Also not much absorption.
 They have also plotted alpha_ox against luminosity to see what effects there may be.
Strateva et al. 2004 have found evidence for a correlation with luminosity but not redshift
for a sample of SDSS quasars with X-ray data (alpha steepens with increasing 2500 A
luminosity).
 Observations of RLQs and Blazars, which are all detected in X-rays. Jets seem to be
rare (not yet detected), in contrast to the predictions of the IC/CMB model.
 At high z, the CDFN survey can detect 1e43 erg/s quasars to z about 10. The CDFN
survey also contains a number of very optically weak sources (undetected to something
like 27th mag). Are they LLAGNs of some type ? (see astro-ph/0403646 for their list of
surveys)
 Stacking analyses of (non-AGN) LBGs at high-z is consistent with XRBs, etc. A new
population is not needed to explain XRB.
 Overall summary : AGN at z=4..6 not very different from low z AGN !
 Looking ahead, can expect to improve coverage at z>5, combine w. IR, submm, mm
surveys to reduce bias and selection effects. Will also study minority populations better
and go a lot deeper with Chandra. Also go to wider field surveys with Chandra and
XMM in the future.
9. Chris Willot (Herzberg Institute of Astronomy, Canada) The host haloes of the most
massive BHs at z>6
 Silk & Rees 1998 paper showed that feedback from the quasar on the surrounding
galaxy could affect the relation of the black hole to the surrounding galaxy.
 Simple model implies there should be a redshift dependence of the M_BH and galaxy
properties (M_BH/M_halo = gamma/3 * (1+z)^gamma/2 with gamma=5)
 He and collab. have obtained deep GMOS imaging in I and z bands of z=6.2 and 6.3
quasars. Data are complete to z=25.5. They can be used to select galaxy candidates at
the redshift of the quasars. They have about 4 candidates.
 Also running another survey with SCUBA , find overdensity of sources in the z>6
fields. Are they at the same redshift? Follow up with deep VLA map shows one object
to be a FRII source, one that may be associated with a galaxy, and possibly the quasar
itself.
 Summary: They don’t see an excess of LBGs in the quasar fields. Searching for any
galaxies that could be lensing the quasars (may have a candidate, but not talking about it
yet). Interestingly, they could get a Gemini AO observation of the FRII source because it
is next to a bright star.
10. Hans-Walter Rix (MPIA Heidelberg) The M_BH – B_bulge relations at different
epochs. Were they different at earlier times?
 Magorrian (1998) related the M_BH to M_Bulge. Using updated values, he and
Haering (2004) now find that sigma and M_Bulge correlate equally well. Local universe
with scatter of about 0.3 dex.
 For higher redshifts:
-
M_BH use luminosity AND emission-line relations (a la Marianne et al.).
-
For the bulge properties (M_Bulge in stars) use luminosity and age of
universe to make determinations of host properties. Or luminosity and colour
information. Or direct dynamical estimates for the stars (and the gas).
-
To estimate properties of the host galaxies at z >1, he and Peng use lensed
hosts (the CASTLES data). Need to simultaneously fit for the lensing model
and the 2-dim profile of the host. They obtain the host galaxy profile and
intrinsic H-band magnitude.
 For a given M_BH, the galaxies at high z are only 0.6 mag more lum at high z,
compared to the 1.2 or so mag expected from their younger ages. Fewer stars formed at
that time?
 Then they use sizes as a measure of the stellar mass and find that higher z objects
(bulges ?) have a M/L different by a factor of 5.
 from host rotation velocity : M_BH/M_Bulge increases with z (at 92% level
confidence ….for 1 object statistic!)
 Scorecard: Host lum. at z about 2-3 are too dim by a factor of 2-3. Likewise, the
hosts at high z are smaller than at z=0.
 Bottom line : “Hypothesis that M_BH/M_Bulge is constant throughout formation
process of all massive galaxies” is in TROUBLE.
11. Bernhard Brandl (Sterrewacht Leiden) Spitzer Space Telescope observations of
AGNs
 Brief instrument overview (IRAC, MIPS,IRS)
 What to see in AGN compared to starburst ?1
 He shows that starburst galaxies have strong PAH emission features at 11-14 microns
and have more continuum emission at 20-30 microns. Cen A shows silicate absorption at
10 microns, no significant PAH emission, conspicuous H_2 emission.
They have GTO time for 120 ULIRGs, with z out to 1. So far, data for 20 objects with
a range of properties, from hot dust to cool dust with many spectral features. Also a
range of strengths and widths of the CO feature in ULIRGs. U5101 shows Si absorption,
PAH emission, and AGN features [NeV], too, although the AGN is weak. Q : Hot dust
dominated = AGN, whereas PAH dominated = starburst ?
 3C184, a monster radio galaxy at z-0.994, is one example of a high-z radio galaxy. It
is very faint, but there is evidence for the [NeV], [NeIII] lines, which are signatures of an
AGN.
 They have also observed a high-z quasar that is gravitationally lensed and shows the
redshift Paschen alpha and beta. They can detect the z=6.4 quasar and are working to get
a spectrum of it. If L_FIR is completely due to SB, then SFR is enormous (3000
M_sun/year), M_H2 = 2*10^10 M_sun, L_FIR = 1.3*10^13 L_sun
12. Anton Koekemoer (Space Telescope Science Institute) First Spitzer observations of
extreme X-ray/optical objects. Low X/O objects are star-forming galaxies that
previously were only studied locally.
 CDF : lowest F_x/F_o objects seen for first time out to z=1 (EROS), focus in this talk
on highest F_x/F_o : EXOS !
 High X/O objects don’t seem to have any local counterparts. They have redder colors
in near IR than even EROs. (E.g., z-K of 3 to 6 <-> z-K of 2 for other AGN)
 They are studying them with Spitzer as part of the GOODS program. Using both
CDFS, CDFN. Spitzer detects all of them! They are red at all observable wavelengths,
except for one or two objects with flat or blue IRAC colors.
 Simple model to fit SED : Assume that they are obscured AGN and dominated by the
host. Use Charlot and Bruzual models and age-dependent reddening. One object is so
red that it is very hard to explain.
 Their best-fit redshifts are 2 – 5. Compare well with high-z Cristiani LF for moderate
luminosity AGN. The hosts seem to be of two types, 1) relatively dust free with old
stellar populations (t>1.5 Gyrs)  high F_x/F_o purely observational effect , 2) reddened
starbursts that seem to need an AGN component to account for the large X/O ratio. They
may have high accretion rates.
13. David Alexander (Cambridge) Accreting black holes in spectroscopically identified
SCUBA galaxies
 Combine X-ray and deep Keck spectra of SCUBA galaxies. Submm surveys will
yield ULIRGs at high z that outnumber local ones by a large amount (10^4 per arcmin^2)
due to negative K-correction
 Are they the progenitors of the local giant elliptical population? What will be the
relative contributions of starbursts and AGNs?
 The first correlation of X-ray and SCUBA sources was negative. Did that mean
Compton thick sources?
 But in the 2Ms CDFN catalogs there are X-ray detections of 17 of 20 SCUBA
sources. The redshifts have a broad peak around 1-3. Conservatively, 15 of the 20
sources have an AGN component. Most of them, about 80%, seem to have significant
obscuration. Many of them have enough X-ray counts to do spectral fitting. About half
are Compton thin; the other half are heavily absorbed or Compton thick. The bulk of the
sources are moderately luminous AGNs, like Seyferts.
 What powers them ? Starburst luminosity overall appears to dominate the bolometric
luminosity (<20% AGN contribution, compared to Elvis et al. higher L_FIR/L_x)
 Speculation : Do we see ‘obscured growth phase of the most massive BHs ? A
SCUBA pahse that later turns into the AGN dominated phase ?’
 He estimates SMBH accretion rates of 0.1 to 1 solar masses per year. The overall
picture of accretion rates and lifetimes seem to be consistent, as does much growth during
the obscured phase
Session III First SMBH and structure formation
14. Martin Rees (Institute of Astronomy, Cambridge) Merger history of galaxies, halos,
BHs
 Concept of merger trees : How far down in mass does the merger process go? Do
small halos at high z all contain black holes?
 Re-ionisation : At what redshift does the ionization fraction come down to 50%?
Need to detect ultra-high z objects such as small galaxies, gamma-ray bursts, or SN. Or
use CMB fluctuations (polarization) from WMAP.
 What about the fate of the first bound clumps of gas?

If 1e4 solar masses, virial temp is 50K, there is no cooling, and no star
formation.

At 1e6 solar masses, T_vir = 1000 K : cooling by molecular gas can
occur, as does star formation.

At 1e8 solar masses, molecules are not needed for clumping and star
formation to occur.
 First generation of stars included some very massive stars, which would produce UV
radiation and also BH remnants up to 100 plus solar masses. But there is a gap until 250
solar masses owing to the pair-production instability. At higher masses there can be BH
formation again. (cf. also Marc’s Stellar Interior Class -> fate of z=0 stars paper)
 These early 1e3 solar mass BHs could accrete quite efficiently. (Comparison :
Accretion 1 baryon -> 1.5e6 UV-photons <-> 1e5 photons from 1 baryon in massive
stars)
 But how fast can they grow? Depends on the accretion efficiency, and to get 1e6 to
1e9 masses at z > 5, lower efficiency (advection dominated flows). Begelman 1978
paper. But there have been questions about winds and circulation patterns inhibiting
growth.
He says the low efficiency accretion is plausible for BH masses below 1e6 solar
masses. The Soltan argument implies that the big BHs gain most of their mass by
efficient accretion. (eps = aggr. Mass of BH in GN/emission of all AGN out to z=3;
eps>0.1 for accretion onto massive BHs at recent epochs, massive BH gain >50% of
mass by efficient accretion, but BH at high z could grow to 1e6 M_sun via inefficient
accretion)
 Mergers? Tight binary BHs undergo 3-body interactions with stars to get closer and
eventually merge. Similar effect can occur for binary BHs in dense gas environment.
 Problems – ejections of BHs via interactions with a 3rd can slow the process via
ejections. Or there could be a recoil resulting from gravitational waves that would
disrupt the merging. Conclusion : Hierarchical build-up cannot start too early.
Other questions:
-- Fate of Pop III remnants in dwarf galaxies. Need to have enough seeds to form
eventually massive BHs.
-- Could a 1e6 solar mass BH form in one go? A post-Newtonian instability
could occur in a 1e6 M_sun very massive star that would cause it to collapse before
nuclear fusion began. (i.e 1e6 M_sun is a special mass : above it NO main-sequence
possible). But could this assembly of gas come about without fragmentation? Yes if
cooling were inhibited, a greater concentration, extra opacity, weak magnetic fields.
-- He suggests building on the 1960s work on VMOs (very massive objects).
Fowler, Feynman, Shapiro, et al.
 Sunyaev asks why he didn’t mention the collapse of dense stellar clusters. Answer –
shortage of time. It is a possibility that needs more work. More encouraging than it used
to be thought.
15. Volker Bromm (Harvard) Formation of the first SMBHs
 Cosmic History : From Simplicity to Complexity <- main transition stage : Formation
of First Stars
 We now believe the first stars formed about 1e6 years (z about 20) after Big Bang, 1 st
quasars, 1e9 years. How did the first massive BHs form? Stellar seeds? 1e6 initial BHs?
Need to understand cooling paths in the early universe. In the absence of metals, H_2
is the only effective coolant at T less than 1e4 deg.
 He and Lars are now using a particle based SPH approach:

Start with 1e6 solar mass halo objects at z about 20. For H_2, the Jeans
mass is about 1000 solar masses (T_min about 200K, N_crit about 1e4).

Final mass of a Jeans mass clump depends on accretion from dust-free
envelope. The accretion process in Pop. III can be much more rapid
than at present time (because the gas temp is higher : dust free
environment !). Can get up to 500 solar masses in 3e6 yrs (in absence
of feedback effects). Or get to 100 solar masses in Kelvin Helmholtz
time. See paper by Heger et al 2002 about the death of the first stars for
summary of the fate of stars vs. initial mass. (here again : Mass
gap/island from 100-259 M_sun due to pair-production instabilities no
BH formed  very effective metal enrichment of ISM/IGM)
 Bromm et al. have considered the effect of the first SN in the universe. Could seed the
early universe efficiently with heavy elements -> dramatic effect on star formation :
fragmentation of gas clumps now possible and formation of low(er)-mass stars. Critical
abundance is Z of a few by 1e-4 solar. This would occur around redshift 12 to 20.
 Other idea : Form first QSO by direct collapse of primordial gas cloud (Loeb & Rasio,
1994, ApJ 432) -> if T_vir = 1e4 K cooling possible via ATOMIC hydrogen AND
enough UV photons to destroy H2 (=conditions in Dwarf Galaxies’ nuclei). This could
collapse 1e6 M_sun into a 1pc^3 volume (not yet a BH). But there is the question of
whether it would fragment during its own collapse or not.
He closes by noting that SWIFT will have the capability of observing GRBs at z
beyond 15 from the first SN.
16. Nicola Menci ( INAF, Rome) Role of interactions in triggering formation of BHs
and starbursts.
 He and collaborators have been developing models for merging that include a lot of
physics and the semi-analytic approach.
 They find that the star formation rates in bigger galaxies peaked at earlier times than
in smaller galaxies, consistent with the evolution we seem to be seeing now.
 Their models underestimate the SFR in massive galaxies at z > 4. Also, the steep
observed decline of quasar activity after z=2 is not reproduced by HC models.
 This has led to them incorporating the effects of mergers and disruptions on the
feeding of the central BH as a way of enhancing the activity. They can achieve a pretty
good fit to the evolution of the quasar LF. They also can match pretty well the LBG
results of Steidel et al.
They do pretty well in matching X-ray data, too.
However, there are still problems to work out.
17. Volker Springel (MPA Garching) Cosmological hydrodynamical simulations and
the growth of supermassive black holes.
 Observation of M-sigma suggest similarity in growth -> Suggests that feedback of
AGN on its host galaxy (as a means of self-regulation of growth, cf. Margorian) could
help solve many puzzles, such as the absence of cooling flows in clusters of galaxies,
cluster scaling relations like Lx-T relations, why ellipticals are so gas poor, etc.
 To date galaxy simulations have not normally included effects of black hole growth.
It is a hard problem, and people have been busy enough trying to understand the effects
of stellar feedback or the cooling catastrophe and ensuing overproduction of stars). He
and Hernquist have developed a multiphase subresolution model of the ISM to help with
some of these problems and develop an effective equation of state.
 Here, he and Tiziana model BHs simple as sink particles and parameterize the
accretion rate to model the growth of black holes. For feedback, they use a standard
radiative efficiency of 0.1 and assume that the feedback is a fraction of the quasar
luminosity. They can do a quite high resolution simulation of a BH in a disk galaxy in 3
dim. (Very nice model)
 Recognise 3 phases of BH growth: Bondi, Eddington, and slow, feedback regulated.
This leads to several by 1e6 solar mass BHs in 1.5 Gyr.
-- In the Bondi-growth phase, small seed BHs will not grow fast enough to be
useful.
--Major mergers have a big effect on the available “fuel.”
 Fabulous simulations of mergers (of 2 disk galaxies), including star formation, BH
merging and cleaning out of central gas. This can lead to BHs of a few by 1e7 solar
masses. Also : tidal toques extract angular momentum and nuclear starburst follow
 Comparing mergers with and without central BHs, in the latter case, 90% of gas turns
into stars and only 0.05% gets expelled. With BHs, half becomes stars, 1/3 expelled from
halo. The BHs get within 100 pc at a Gyr or so. The final hardening of the BH binaries
cannot be followed in the simulations.
-> The feedback also has an effect on the distribution of stars in the center and helps
avoid the central spike that was a problem in the Mihos, Hernquist work.
 Another consequence of BH feedback is that it cleans out the gas from the galaxy and
terminates star-formation activity. It also produces the r to the ¼ profile. Finally, it gives
a path for eventual BH merging.
 Remarks on merger simulations : Short timescales for accretion processes and SF;
remnants very gas-poor with low, diffuse X-ray emission; QSO outflows seem important
 Overview at : www.mpa-garching.mpg.de/galform/virgo/index.shtml
www.virgo.dur.ac.uk/index.html
or
18. Tiziana de Matteo (MPA Garching) Part II of this work
 M-sigma relation and evolution of quasars based on a self-consistent treatment of
BHs in SPH simulations of galaxy formation (Gadget)
 Consider two cases: 1) BHs in isolated galaxies and mergers, 2) BHs in
cosmological simulations.
 BH fueling is linked to spheroid formation. Model: BH in galaxy center as a sink
particle, able to swallow other galaxy particles, simple accretion (BH immersed in
medium with rho and T) and feedback parameterization.
 In the isolated galaxy model, SFR decreases with time and the gas gets hotter.
The BH accretion rate goes up with the galaxy mass. If no feedback, can get very
massive BHs and galaxies run out of gas quickly.
 (Remember that they are modeling the rate of gas inflow to the center and
assuming it gets accreted. As Krolik and Blandford noted, the details of the
accretion mechanism (transport and magnetic fields) will matter a lot.)
 Reproduction of the M-sigma relation (i.e. ‘toy’ with right slope) for both isolated
and merger models. The feedback is important to their success. For merger
models : no central cusp of cold gas seen !
 In the cosmological simulations they use a box of 33 Mpc and 2 by 216^3
particles. Seem to get pretty good agreement with both M-sigma and current
density of BHs in local universe.
 Rees : ‘That seems like a lot of action below z=1. How does that fit into the
downsizing’ picture that emerges from observations ?’
19. Piero Madau ( Unversity of California Observatory) Dynamics and Evolution of
earliest seed BHs
 Main questions: Was link between SMBHs established primordially? What is role of
feedback from quasars? What about relativistic effects? What about assembly history?
How to grow 1e9 mass BHs by z=6.4? (Would take just about all the available time and
still require 150 solar mass seed BHs : when assuming L(z=6.4 SDSS QSOs) = L_Edd ->
t_growth = 7*1e8 years)  open question : to get 1e6..7 or 1e9 ???
 Good spectra for CIV absorbers up to z of 5 now available : little evolution of
Omega_CIV with redshift, implies pregalactic enrichment of ISM.
 Note : mass density of seed BHs at z=20 is 0.2% of present day SMBHs and in this
model with gas accretion tripling the mass in every major merger Omega_SMBH = 0.6%
at z=14. I.e. small, but still measurable : UV ionizing flux > L_PopIII !
 He also says that the miniquasars at high z can help re-ionize the universe. The effect
of X-rays from the miniquasars is to heat the surrounding gas (1e4), not ionize it (‘Jeans
smoothing’ : only 5% of X-rays contribute).
 He can fit the quasar LF at different redshifts reasonably well based on assuming that
the accretion goes as delta m prop to sigma to the 5th power.
 Major mergers : t_dyn_frict < 1/H -> BHs into centres  minor mergers : not all
BHs sink to centers as t_dyn_frict > 1/H (‘wandering BHs’)
 Triple BH interactions can yield scattering of the intruder (if its mass is lower than the
others) or recoil of the binary and ejection of the most massive BH (if intruder mass is
high). However, they are only about 10% of the cases.
 He has also calculated the spin properties of the BHs, which appear to be needed to
account for the Soltan argument, i.e., to give high efficiency accretion.
 cf. Heger & Woosley, 2002ApJ...567..532H)
20. Abraham Loeb (Harvard) Birth and dynamics of black holes in galaxies.
 Formation of quasar seeds (MBHs): Simple model for accreting BHs at early cosmic
times. Probing reionization with accreting BHs. Dynamics of BHs.
 Seeds: SF without metals -> expect : high-mass stars favoured. But :Start with objects
where atomic cooling dominates and H_2 is suppressed : expect bigger nuclei to form,
with masses about 1e6 solar masses (e.g., Bromm, earlier today and earlier work by
Eisenstein, Loeb, and further back, to Zeldovich et al) as gas clumps can NOT fragment;
result : formation of SMBH at once !
 Alternative seeds are supermassive stars that need fast rotation to be stabilized against
general relativistic instability. They could be probed via (early) gamma-ray bursts.
 Simple model: Self-regulated growth of SMBHs. Occurs when energy emitted by the
BH in a dynamical time matches that of the binding energy of the gas in the host galaxy
(L_em * t_dyn = 3/2 M_gas * sigma^2). This also produces a match with the BH and
galaxy bulge correlations (M_BH – sigma^5 and M_Bh/M_stars = sigma^2 *(1+z)^3/2)
 He also gets a match with quasar clustering properties and their lifetimes (about 4 by
1e7 years * (eps/0.1)/(L/L_Edd) = t_lifetime = M/M_dot). This in turn leads to size of
ionization sphere around the quasar.
 Gamma-ray burst afterglows are better probes of high-z universe than quasars because
the quasars have a significant impact on their surroundings. The GRBs are believed to
reside in lower-mass halos (M_ion = 4*1e4 M_sun * E/10^51 erg).
 Dynamics of BHs and stars in galactic nuclei : How can stars get so close to BH ? (cf.
Genzel et al in Sgr A* !)

He suggests that winds from the stars near the GC provide the fueling of
the Sgr A* BH.

Finally, he says there should be many neutron stars near Sgr A* and
they should be useful probes.

BHs in galactic centers will wander around because of Brownian
motion-type encounters with stars in the innermost region. However,
one of the audience members said that another group does not
reproduce their results.
21. Zoltan Haiman (Columbia) The growth of the earliest SBHs and their contribution
to reionisation
 Roles of BHs in the reionization history of universe: pretty complex and seems to start
around z=20, according to WMAP.
 Complex picture :

The relatively hot IGM at z=4 (20,000 deg) implies that it could not
have been ionized in one shot at z=17, for example.

Gunn-Peterson troughs in the z=6 quasars do not imply that the universe
was very neutral at that point.

Existence of a Stromgren sphere around the z=6.28 quasar shows that
the quasar ionized the IGM down to z=6.18. The Stromgren sphere
radius is about 6 Mpc in physical size.
 What are the sources of reionization?

DM halos occur at z=20-30. Photoionization is a natural mechanism,
either by stars or BHs.

However, the number of known quasars at z=6 are too few to account
for the observed degree of ionization.

Sources could be the first generation of stars. Metal-free massive stars
have harder spectra, yield more ionizing photons.

Seed BHs could boost by x10 the number of photons, and the spectra
would be harder than for more massive BHs.

Decaying particles.
 Gravitational lensing could be up to 100% for some cases at z=6. This places a mild
limit on the number of lower mass BHs. A better constraint comes from the SXRB. It
would be overproduced if quasars produced 10 photons/H atom, however a ‘preionisation’ up to 50% at z=15 by LLAGN is still allowed
 Papers/Authors on QSO feedback at high z : H2 feedback (Oh & Haiman 2003),
Photoheating (Thoul & Weinberg 96, Haiman & Holder 2003), Metal-pollution feedback
: Change from PopIII->PopII (Cen 2003)
22. Stuart Wyithe (Melbourne) Calibrating the BH and halo mass relation with high-z
quasars.
 Model assumptions :

Accretion at Eddington rate

Local M_BH – V_c relation works at high z

BH growth is regulated by feedback over the dynamical time

Quasars are associated with major mergers of galaxies (one quasar
episode per merger).

Use the quasar correlation function as an indicator of the halo mass in
which it resides.
 Argues that BHs occupy a larger fraction of a galaxy’s mass at earlier times.
 Gets good agreement between his model and z>2 quasars.
 Model overpredicts number of luminous quasars at z<2, but is OK below L*.
One of his conclusions is that the dynamical time scale of a galaxy may be the origin
of the quasar lifetime.
23. Roberto Gilli (INAF Arcetri) Spatial Clustering of X-ray selected AGN in the CDFs
 Hope : New insights into the properties of the obscured and low-lum sources. Very
high surface density of X-ray sources, 3-4 x 1e3 is helpful in this case.
 The redshift distribution in CDFS is very spiky, 2/3 of sources are in two peaks at 0.67
and 0.73. He can estimate the spatial correlation function.
 They also classified the sources by hardness ratio and luminosity, adopting 1e42 erg/s
as dividing line between starbursts and AGNs.
 The clustering amplitude in CDFS is about twice that of CDFN, probably because of
the two groups.
 Indeed, if the two groups are removed from CDFS, then the amplitudes are about the
same and roughly consistent with those for early-type galaxies at the same redshifts.
24. Luigi Danese ( SISSA Italy) From first Galaxies to QSOs
 A Physical Model of the co-evolution of QSOs and their spheroidal hosts. (Seems to
represent the semi-analytic model camp)
 Motivation : Most massive galaxies are in place by z=1 and have old stars.
Furthermore, most massive BHs were active earlier.
 In the Granato et al. models for a 1e13 mass halo, the SFR peaks at t=10^8.5 yrs and
drops precipitously. So does the accretion rate for the central BH. But this is masked by
dust. He says that one of their previous assumptions is now predicted by the model.
 They can also reproduce the local galaxy luminosity function and local BH mass
function.
 Number of testable predictions, e.g., 20% of 24 micron sources with S > 100 micro Jy
should be dusty spheroids at high z, X-ray emission from SCUBA galaxies, absorption
lines around high-z QSOs should have at least solar metal abundances. Massive galaxies
abundant at z=3, will have massive BHs.
 Suggestion of phases : SCUBA -> QSO -> EROS -> Local E/S0 Galaxies ?
Session IV The Case of Sgr A*
25. Reinhard Genzel (MPE Garching) The supermassive black hole in the Galactic
Center
 Cover 4 topics : Star formation in central parsec, testing BH paradigm with stellar
orbits, properties of stellar cusp, flares and BH spin
 What about the “blue” stars near the center ? The stellar distribution peaks on the
position of the GC.
 They now have spectra of 500 to 1000 stars, some giants and supergiants. Also
somewhat younger late-type stars (2800 deg AGB stars). Finally some stars show P Cyg
profiles of He and H and are very young and luminous. Even WR stars, such as WN5
and WC. The hot stars account for the energetics of the GC region. The S2 star is an
O8/9V star. So how did these stars form?
 Dynamics. Now have proper motions for about 1000 stars. See Ott et al. 2004. The
motions of the old and young stars are very different. The young stars show evidence for
rotation, in the “wrong” direction in their radial velocity diagram. There seem to be two
independent systems, clockwise and counterclockwise rotation, nearly perpendicular to
each other. The two systems formed within one or two million years of each other.
 How did these massive stars get into the central cusp? Stars more than 2 solar masses
had to form in the central region. Not enough time for them to migrate in. Did they form
in place? Or, did a young, massive star cluster sink into the center? A “helper” black
hole of intermediate mass could shuttle stars into central region. Various scattering
mechanisms have been proposed.
 Stellar proper motions in central 45 light days (1 arcsec). NACO has 40 mas
resolution. There is an IR counterpart now seen at the position of SgrA*. One star
achieved a motion of 8000 km/s for a short time. S2 passed within 17 light hours of the
GC. It has e=0.88, P=15 yrs. Its distance is 8 kpc.
 They still get a mass of 3e6 solar masses for the BH. The proper motion of the GC IR
source is < 400 km/s. From radio, it is less than 2 to 20 km/s.
 Central densities. The stellar cusp has a density of 1e8-9 solar masses/pc^3. The limit
on the central source is now about 1e22, or even greater. The evidence for a BH is really
strong.
 The S2 orbit allows an extended mass of about 3-7e5 solar masses. This will produce
a precession of the orbit that should be measurable in the next few years.
 The radio limit on the angular size of SgrA* is now about 1 AU. It is unusually
underluminous at 1e-9 Ledd. There are, however, X-ray flares on scale of 10 min to 2
hrs. The source has now been visible in the IR. There is some evidence of a 17 min
periodicity in the variability, which would be evidence for a spinning BH.
26. Andreas Eckart (Universitaet zu Koeln) Simultaneous NIR and X-ray observations
of SgrA*
 First attempt with seeing limited IR and X-ray obs. were not very successful in IR
because of low angular resolution. Now, with NACO, they can do much better.
 The NIR and X-ray flares are simultaneous to within 10-15 min.
 Activity also seen by BIMA at 3.4mm.
27. Mark Morris (UCLA) IR and radio observations of the GC
 Keck for astrometry and IR fluxes, OVRO for 3mm brightness.
 Confusion limit at 2.2 microns within 0.2 arcsec is 16-17 mag.
 Speckle imaging with 0.14sec exposures and shift and add technique. This gives high
angular resolution but doesn’t go as deep as AO.
They get results similar to Genzel et al. Interestingly, the spectroscopic data of the
German group and the proper motion yield a new estimate of the distance to the GC. The
two groups get 8 to 8.5 kpc with an uncertainty of 0.5 kpc.
 Note also that 2003 was first season to have a clear view of SgrA*. It was previously
blended/blocked by the coincidence with a bright star, which has now moved away from
the central source. In mid-IR, dust emission in direction of GC is prominent and makes
SgrA* hard to see.
 Time variations on few hour time scale are seen w. OVRO.
28. Frederick Baganof (MIT). Chandra observations of the GC
590 ksec exposure, detect 2300 sources, great variety of objects.
 Most are stars in nuclear bulge. White dwarfs. Some SNR related phenomena.
 There are four X-ray sources in the central 0.4 arcsec, including SgrA*. They think
that SgrA* is within the SNR seen toward the east.
 He and collaborators have done an extensive multiwavelength monitoring program for
flaring.
 They do resolve SgrA* and find its size consistent with the Bondi radius. The profile
at larger scales is consistent with diffuse emission from surrounding stars.
29. James Moran (Harvard-Smithsonian)
 SMA, Mauna Kea, 300 – 1300 micron, 8 antennae, 6-m diameter.
monitoring SgrA*.
Have been
 Measured polarization, which is 5.5% at PA=69 deg.
 Data seem consistent with a rotation measure caused by a screen plus variations,
either from the central source or changes in the screen.
Session V : Interaction of SMBHs with their environment
30. David Merritt (Rochester Institute of Technology) Interactions of BHs and
surrounding stars and dark matter.
 Adiabatic growth and collisionless cusps. Final profile depends on initial conditions.
Often quoted as r to –3/2 but that’s for an isothermal model. Steeper profiles could easily
be predicted, but don’t match real galaxies.
 How about collisional cusps? Bahcall and Wolf 1976. Seems to fit better.
 Dark matter. Start with a NFW profile, grow SMBH adiabatically, allow heating by
stars. Get a profile like r to –1.5.
 Why do we care? Some dark matter candidates might produce TeV gamma rays near
galactic center that would be observable.
 What are the natural feeding rates of stars? If orbits are replenished, then 1 star per
100 yrs in a typical galaxy with sigma of 200 km/s. But that’s a big if. Need two-body
interactions to scatter stars into the right orbits to be captured by the BH. Early theory
was worked out for globular clusters, which are relaxed. Centers of galaxies are not
relaxed. Nonetheless, the predicted rates scaled for galaxies don’t seem way off.
 What about chaotic loss cones, which would arise from triaxial or disky spiral
galaxies? The capture rates could approach that of the collisional model above.
 What about mergers of galaxies (and BHs)? Seems attractive, but numerical
calculations for the scattering of stars depends on the number of stars, and more stars lead
to longer merging times. There seem to be a variety of uncertainties.
 Cusp destruction in mergers. Alistair Graham has been fitting Sersic profiles to
galaxies and finds that some have deficits in the centers. The deficit corresponds to about
twice the mass of the black hole.
 On the other hand, binary BHs can clear out stars from the center of a galaxy. This
would lower the feeding rates. It takes about a relaxation time to refill the orbits near the
center.
 Brownian motion (gravitational). SMBH wanders due to random impulses from
nearby stars.
 Finally, there could be gravitational wave recoil in the final stages of a merger. Some
chance it could affect the behavior in the center of the galaxy.
-> There seem to be many dynamical problems that need to be worked out in the future.
Rest of session is missing ! Talks :
31. Sergei Nayakshin Condensation, Star Formation and accretion in quasars and Sgr A*
32. Gijs Verdoes-Kleijn ISM Dynamics around Black Holes in Neraby Radio Galaxies
33. Thomas Beckert The Evolution of the Dusty Vail around AGN
Session VI : Physics of Accretion Discs
Missing completely.
34. Marek Abramowitz Super-Eddington Accretion
35. Julian Krolik BH Spin-Up via Accretion
36. Yasuo Tanaka NLSy1 Galaxies : Growing BH with high accretion rate ?
37. Daniel Proga Accretion of Low Angular Momentum Material onto Bs
38. Maryam Modjaz Probing the Magnetic Field in the Accretion Disk of NGC 4258
Session VII : BH-BH mergers and Gravitational Waves
39. Sterl Phinney (California Institute of Technology) BH astrophysics from
Gravitational Waves
 Overview of LISA :3 spacecraft separated by 5e6 km. It will detect both polarization
modes. The beam pattern is very broad, not directional.
 Detection of many sources AT ONCE (analogy : many speakers in one room talking
in different languages).Will use Doppler modulation caused by orbital motion of
spacecraft around sun to determine positions.
 Sources will include:

galactic white dwarf binaries

supermassive and intermediate mass black holes merging (however :
17dimensional variable/parameter space  difficulty in getting
templates !)

compact objects being accreted by SMBHs.

Phase transitions from early universe (collision of walls of regions
where electro-weak symmetry breaks down)
 White dwarfs will serve as calibrating sources, also will be source of confusion.
About 1e4 will be detectable.
 Merging SMBHs : 3 phases (Inspiraling, Merging and Ringdown).Will be detectable
out to z of about 30 and masses down to 1e5. But upper mass limit will be about 1e7.
Expected merger rate (mrger-tree model dependent !) for > 1e6 mass BGs is about 1/yr.
Merger rate for 1e4 BHs might be 1/day (too high for Sterl, would confuse other
programs).
 As an aside, LISA will be a good dark energy probe because it will yield distance
determinations to 0.4%
 Stars coming within 10-15 r_g of the galactic center BH will produce detectable
signals for LISA (after all : up to few M_sun changing direction within 15 minutes at
speed of light !)
 Probe of Kerr solutions of GR and BH “structure”. Inspiral of smaller objects onto
BHs will probe the geometry near the BH (“Bothrodesy”). But this gets computationally
very intensive.
40. Bernard Schutz (Albert Einstein Institute, Golm) The Art and Science of Black
Hole Mergers.
 Problem : How to get BHs close enough so that gravitational radiation and
coalescence will occur in a Hubble time. Basically, they have to come within a few
hundred AU for 1e6 BHs. But to be observable, they have to get within a few r_g.
 The main effects are scale-free, i.e., they are not f(mass).
 Three phases: inspiral, last stable orbit and merger, ringdown. Have to be treated
numerically because very nonlinear problems. At the same time, the mergers provide
tests of GR. We would like to know the energy radiated in the merger and the angular
momentum of the merger product. Also the linear momentum (recoil).
 Inspiraling : Post-Newtonian approach useful and known; Ringdown know
analytically; Merger phase most problematic : “Last stable orbit” problem
 Issues in the latter :

Need something like 1e12 grid points. Mesh resolution of 0.01M. Yet
need the outer boundary has to be at 100M.

Also need 50-80 variables per grid point.

Nonlinear, highly coupled equations.

Small timestep (signal speed = c)

Have to avoid problems near the singularity or cut it out.

Boundary conditions are not known at the outer edge of the grid.

The equations involve 4 constraints plus 6 dynamical. Infinite number
of ways to formulate an initial-value scheme and identify dynamical
variables. This has a big effect on the stability of codes. Coordinate
freedom can also affect stability.

Finally, how should the output be interpreted? Visualized? Understand
instabilities?

How to assure the validity of the results? Convergence is the main test
used by the groups. Comparison of calculations done be separate
groups.
 Initial data continue to be a problem. The Discovery Channel simulation of a year ago
was quite instructive. Visually attractive but Bernard has doubts about the validity of the
merger itself, which occurred in about half an orbit.
41. Scott Hughes (MIT) How BHs get their kicks : Radiation recoil in binary BHs
 In binary systems, the smaller object is moving faster, and its gravitational radiation is
more beamed. This asymmetric radiation emission (which is a generic feature of any
radiation, not just gravitational) imparts linear momentum to the system.
 In gravitational wave case, need very fast motion for effect to have measurable
consequences very late in binary black hole coalescence.
 Result depends only on the mass ratio of the components.
 First estimates (Fitchett et al.) indicated that velocities of order 1500 km/s could
occur, but they were not done using enough GR, so it’s not clear if they are correct.
 Scott and colleagues are developing a better approximation. They use perturbation
theory (very unequal masses in the binary) and figure out a way to extend results to more
realistic conditions.
 While they still have unsolved problems in their approach, they think that the 1500
km/s recoil is much too large. More like 100-200 km/s instead of 1500.
42. Karsten Danzmann (MP Gravitational Physics & Hannover) LISA & LISA
Pathfinder
 Status report of the instruments (launch expected 2007/2008)
 Space mission absolutely needed since on earth we hit the wall of ‘gravity
disturbances’ at f<1e-3 Hertz (falling leaves, tracks vibrating due to train traffic,….)
 Arm size : 5e6 km = compromise between : larger arms better reduction of effect of
spurious forces (‘shakes’) on arms, smaller arms shorten round-trip light travel-time
 angular resolution expected at 1’’
 Diffraction after reflection : 0.7 W emitted -> received 70 pW !
 currently technology tests with test masses of Au-Pt-alloy with vanishing magnetic
susceptibility
 Solar radiation light-pressure = main problem : ‘drag free shielding needed’
 Costs for LISA Pathfinder expected at 160 Mio. $
 Question from audience : Why not change arm length during mission ? Thrusters
thrown away at parking so far. However, idea is being discussed seriously.
43. Stelios Kazantzidis (Zuerich) SMBH dynamics during assembly of galaxies
 Overview of mechanism to grow BHs and their implementation into numerical
simulations (Gas Accretion, Tidal Disruption/Capture of Stars, Mergers)
 Introduction to GASOLINE code simulating mergers of spiral galaxies with various
components (1e5 particles of DM, stars and gas with various coolants and SF recipe,
finally BH at center; resolution 100pc for galaxies, 30 pc for BH environment)
 General result : Radiative cooling strong enough to create baryonic dominance in
central few kpc and formation of very massive nuclear disks that might fuel the cetral
BHs
Session VIII : Jets, Outflows and QSO feedback
44. Andrew King (Leicester) Outflows as origin of M_sigma relation and SMBH
environments
 His involvement started with Ken Pounds work on outflows from some narrow-line
quasars and the realization that the outflow mass rate was comparable to Eddington value
(i.e. M_dot_out * v_out = L_edd/c roughly). They then went on to suggest that a
system’s response to super-Eddington accretion is to expel a significant amount of
material.
 The galactic version of this are the ULXs. Several are surrounded by large nebulae.
The size of the nebulae implies large energy input. Hypernovae? – or outflow.
 What is relevance to growth of black holes? Soltan (1982), Yu & Tremaine (2002)
argument shows that most of mass is assembled by luminous accretion. Probably need to
grow on Salpeter timescale. Would be accompanied by significant outflow.
 In turn, the outflows have a significant effect on the surrounding galaxy which absorbs
most of the outflow momentum and energy. E.g., PG1211+143 (accreting at 1 solar
mass/yr for 5e7 yr) could have deposited 10^60 ergs of mechanical energy <-> binding
energy of bulge 10^59 ergs.
 If one assumes that the mechanical energy of the outflow is the same as given by
Eddington, then the equations simplify. Once the outflows become comparable to sigma,
the hole grows until mass is 1.5e8 sigma_200^4 and things work pretty well.
 Skepticism :

Assumption of spherical geometry, which observations show is not the
case.

Why and how is the disk accretion cut off ?

What happens to the swept-up gas?
 This picture would have most of the mass growth in super-Eddington phases. But
little of that is observed. They would be obscured or at high z.
Missed Talks :
45. Sebastian Heinz The importance of outflows for BH growth
46. Laura Maraschi Properties of Jets at Different Scales
47. Marek Sikora Are Quasar jets matter or Poynting Flux dominated ?
48. Mitchell Begelmann (JILA, Colorado) AGN feedback
 Strong reasons to believe in outflows, both observationally and theoretically: 3C48
radio emission and X-ray holes coincide, jets and BAL outflows (in X-rays). Inefficient
accretion (ADIOS) and radiative accretion w. magnetized corona and winds. Could yield
a kinetic output of > 0.01 M_BH c^2. He suggests it could even be 10% of the rest
energy.
 Matter cannot escape galaxies as easily as radiation, but he also points out that one gm
of accreted mass could accelerate 200,000 gm of material to the escape velocity of the
galaxy. So feedback should be very important.
 Galaxy clusters give us labs for looking at all this:

The cooling flow problem. In some clusters, the prediction was that
there should be a cooling catastrophe near the center. But Chandra data
show no evidence for a mass dropout or severe temperature drop near
the centers of clusters.

The cluster entropy problem. Lx is predicted to go as T^2, but is
observed to go as T^3.
 Is AGN feedback the answer? Observations show the cluster heating to be distributed
widely. An entropy floor is manifest on large scales. It is needed to avoid the cooling
catastrophe. Also, it is pretty gentle, not shocks, for example.
 Radio galaxies’ jets are expected to evolve through three stages: momentum-driven,
energy-driven (both supersonic and overpressured), and then buoyancy-driven (subsonic,
gentle). The latter would produce “effervescent” heating. The buoyant gas rises
subsonically through pressure gradients and does pdV work as it expands thus quenching
thecooling flow. It does not mix with cluster gas, produces X-ray halos. Eventually the
work has to be converted to heat in a way we don’t understand yet.
 Because of the complexity of the problem, simulations are needed model the effects in
a convincing way. Use FLASH code (with collaborators).
 Isotropization? There is a mushroom cloud effect and unsteady injection. Cool rims
result from entrainment of lower temperature gas. Also, the X-ray holes become filled
with radio emission, or not, depending on the galaxy.
The bubbles tend to stabilize the cooling of the gas. They can also quench the cooling
flows if there is reasonable feedback. They can explain the cluster entropy problem.
 General conclusion : AGN can provide gentle heating of gas in clusters.
49. William Forman (Harvard) Outbursts from SMBHs and their impact on the hot
gas in elliptical galaxies
 Perseus cluster is one of the classic cases of cooling flows and attendant problems.
Shows the ripples and X-ray holes.
 M87 is five times closer and has spectacularly good data. Shows a cooling flow of 1020 solar masses per year. Has a bright central region in X-rays (100ks ACIS
observation), arms, jet, and a counter-jet cavity. It has a radio “budding” bubble.
Formation time is about 4e6 years. There is a 17 kpc arc. Overall evidence for repetitive
outbursts from AGN nucleus. Energy in shocks is greater than enthalpy in the hot gas.
The gas in the arms is relatively cool.
 Cen A is the nearest active galaxy at 3.4 Mpc. Has a spectacular jet, opposing bubble,
250 point sources. Diffuse emission has a kT of about 0.3 keV. Radio contours show
interaction of X-ray plasma and radio bubble.
 NGC4636 has a strange X-ray structure in an otherwise normal Virgo elliptical. Has
double pin-wheel like structure. Only has a small, weak, radio source now at center. On
a larger scale it shows a sharp edge and classic cold front.
 Chandra has observed about 100 ellipticals. X-ray emission from the nuclei has been
detected from 80% of galaxies. Note nest of compact X-ray sources in N3379. Diffuse
X-ray emission is also common, probably from hot gas, although could be compact
sources in some cases. They estimate that Lnuclear/Ledd is about 1e-4 to –9 for the
sample (i.e., low). Only massive galaxies have very extended coronae, but some massive
galaxies do not have coronae. Finally, some massive galaxies have little hot gas.
50. Sergey Sazonov (MPA Garching) Radiative Feedback from QSO & Growth of
SMBHs
 Motivation : 1. Ellipticals are gas-poor. 2. Ellipticals contain central SMBHs and obey
M_BH/sigma relation.  Is there a link ? Can the radiative heating of the ISM by QSOs
play a \n important role ?
Method : Take ‘average’ AGN SED and look at effects of ‘heating’
 AGN radiation will heat single(?) ISM above T_vir when below certain density and
above certain radius (where t_cool > t_dyn), i.e. AGN can be significant source of
heating within few kpc
 Is this a possible origin of the M_BH/sigma relation ? 1. Start with gas/stellar mass
content of 1%. 2. BH grows and gas content diminishes. 3. If M_gas/M_stars < 1%
cooling can’t keep up wit heating and transition to gas over T_vir 4. Further growth of
BH is terminated by feedback. ….next four or five arguments escaped my attention…
 Conclusions :

Final stage of BH growth (=AGN phase) immediately follows starburst.

Feedback limits BH growth.

Slope and normalisation of M_BH/sigma relation can be reproduced
WITHOUT free parameters.

Caveat : Use of multi-phase ISM not implemented yet.
51. Pierluigi Monaco (DAUT Trieste) Feedback from QSO in galaxy formation
 simple models of ISM with input of AGN X-ray radiation lead to higher abundance of
hot phases (in comparison to models without AGN) which means subsequently removal
of ISM from galaxy (while some material collapses to center eventually triggering
nuclear SF and more BH mass accretion)
 future implementation into full blown models (including mergers etc…) need to
follow
 main conclusions : 1. AGN able to perturb ISM which changes feeback details 2.
Triggering of wind which can quench late star-formation in ellipticals.
Session IX : AGN Evolution and the X-ray Background
52. Andrew Fabian (Cambridge) The hard X-ray Background
 AGN believed to make up most of the X-ray background. It peaks at about 20 keV.
Gamma at 2-10keV is 1.4. The background is largely resolved at a few keV, but not at
higher energies.
There are still questions about the normalization of the XRB at the 20-30% level. Or,
recent values are that much higher.
 Setti & Woltjer (1989) showed that the shape of the XRB requires absorbed sources.
Indeed, the majority of the sources must be absorbed.
Typical unabsorbed type 1 AGN spectrum is a power law out to 100keV with an
enhancement from reflection source at around 20 keV.
Fabian & Isawa 1999 showed that about 85% of sources must be absorbed. They now
think 70% is a better estimate. (Check their paper).
Absorbed AGN are common : The three nearest AGN, N4945, Circinus galaxy, Cen A,
all have NH>1e23, with the first two having NH>1.5e24 (Compton thick). Locally, type
2 Seyferts outnumber type 1s by at least factor of 3-4. (Where does he get these
numbers?) There are some distant, but powerful Type II AGN examples (NGC6240,
IRAS09104).
 Very likely a more complex geometry than the simple unification torus model is
required. Also, star-formation in surrounding gas helps keep it inflated so has high
covering factor.
 Soltan argument leads to density of black holes. Need to know bolometric
corrections, efficiency, and mean redshift of quasars (eps *(1+z_mean) = eta *
rho_BH_mean * c^2 where eps = background energy density <- measure I_v and assume
bolometric correction)
 Fabian, Isawa, then Elvis et al 2002, suggested efficiencies at least 0.1, maybe 0.15.
But Yu, Tremaine results seems to require even higher efficiencies. What is the
problem?
 Chandra, XMM deep surveys resolve most of the XRB in the 2-5keV band. Many
faint sources are absorbed, but NH<1e23. Dominant contribution in L(2-10 keV) comes
from sources at z=0.8 and L_x < 1e44 ergsec^-1. But where are the Compton-thick
sources?
 The ASCA (Ueda) and HELLAS (Fiore et al) results seem consistent with radiation
coming from z=0.8 sources. But the sources are lower luminosity, <3e44. Then have to
worry about the bolometric correction being different, e.g., lower, around 15. This
reduces the inferred density of BHs to 4-5e5. See Marconi et al astro-ph/0311619 and
Fabian et al astro-ph/0304122.  Proposition : Most absorbed AGN are NOT quasars,
but Seyferts.
 Fabian, Worsley are working to see if the resolved sources in the Chandra, XMM deep
fields stack to make up the observed XRB spectrum (see astro-ph/04…?). Fraction of
resolved sources decreases with increasing energies : 0-2keV >90%, 8keV <=50%.
Missing components have –high column densities –low luminosities. Their point is that
the missing component looks a lot like a Compton thick source at z=1, for example.
 However : bright sources, which are softer, are excluded from the deep surveys. They
use all this to argue that the missing sources must be absorbed significantly.
 He says these sources would be detectable by Chandra in 10Msec.
 His census for the BH density:

unobscured AGNs give us 2-3,

obscured Compton-thin : 2

Compton thick sources 0.1-1 (all in units of 1e5 solar masses/Mpc^3)
 He thinks we need a better estimate of BH density locally before arguing for a high
efficiency.
 Proposition for future research : Important to carry out a detailed census of absorbed
AGN, including Compton-thick ones. (Note :N4945 was classified as a starburst at all
wavelengths except for hard X-rays). Identify the missing hard X-ray AGN and establish
their red-shift distribution.
 EXIST is a GCl so an important mission.
 While Spitzer should add to this, it is hard to distinguish SBs and AGNs.
53. Guenther Hasinger (MPE Garching) When supermassive BHs were growing –
clues from deep X-ray surveys
--> See Gilli 2003 for summary of XRB measurements. His work and that of Worsley
seems to agree pretty well and show same behaviour above 5keV. There are many
ongoing surveys that contribute to all this.
--> Advantage of XMM is that it gives better spectra of the resolved background sources.
They can see the FeKalpha line in the background sources.
--> His group continues to work with VLT and Keck to get the needed optical
spectroscopy. However, the COMBO17 results are very helpful, and GOODS is also
contributing. Incompleteness reduced to about 5%. See Koekemoer et al. for the
optically faint X-ray sources.
--> See Zheng 0406482 for new work on CDFS z distributions.
--> CDFS 202 continues to be the prototype for type 2 quasars (‘Rosetta Stone’). But
how many more are there? It and NGC6245 have consistent SEDs in the emitted frame
(and consistent luminosities). A new one is CDFS 263.
--> The type 2 fraction of quasars increases with decreasing luminosity, not surprisingly.
This has to be allowed for in modeling the XRB. (cf. Ueda et al. 2003)
--> Their ‘multi-cone survey’ compilation now has about 1000 sources from 8 different
surveys. Five are ROSAT based, 1 XMM, 2 Chandra. Only 75 sources are unidentified.
The whole Hubble-diagram (L_x versus z) is covered with these surveys.
--> They see LDDE, i.e., the XLFs at low and z=2 are quite different.
--> When they look at the space and luminosity density as f(z), they see that the lower
lum. objects have peaks at lower z. (‘Seyferts come into the picture considerably later’).
He notes that it is too simple to use average redshifts to estimate the BH density. High-z
decline seen in X-rays at all luminosities.
--> Hasinger, Miyaji, and Schmidt are working on the luminosity functions and their
evolution. Seem to have good agreement with the Menci model (04). No agreement with
the Wyithe, Loeb models.
--> What about evolution at high lum. and high z? Silverman and Champ show evidence
for decline at z>2.5, although their ids are still incomplete. But the decline is less steep
than seen in the optical surveys. He thinks that selection effects account for the
difference (notice that majority of X-ray selected AGN not detectable optically : 1/10
ratio).
--> He compares the SDSS/ROSAT data against the deeper ROSAT/XMM/Chandra
results and notes that Lx is not directly proportional to Lopt in the faint sources. He
thinks that this is due to selection effects. They note the host dilution effects on optical
mag. at low z/low lum. However, when he shows his plots of alphaOX against Lx, the
results are not so clear to me/us.
--> He also thinks the Boyle et al. LFs turn over because they miss the low-lum AGNs
due to dilution effects in the data.
--> Summary :

Majority of AGN are not detectable optically.

Type 2 quasars are found, their fraction decreases with increasing
luminosity.

He thinks we need different modes of BH accretion. E.g. Major
mergers, tidal capture. He notes four modes of accretion: swallowing
small chunks of matter (‘snack-mode’), swallowing stars, accretion
disk, and BH mergers (Komossa et al. 2003). He says DUO, Lobster,
and Rosita will be able to detect many capture events.
--> He also thinks that wider field surveys, but still deep, are needed to make progress
(Extended Deep Field South, Cosmos XMM)
54. Meg Urry (Yale) GOODS Discovery of a ignificant Population of Hidden AGN
--> Hints :

Explains hard X-ray background.

Local AGN unification (from polarization)

More likely in Early Universe.
--> Her take on CDF-N is that the redshifts of X-ray sources are too low, ratio of
obscured to unobscured sources is too low.
--> Idea behind GOODS for her : finding obscured AGN in quasar epoch at z=2..3,not
found in UV-Optical, thus need far-IR and X-ray.
--> They have observed about 500 GOODS AGNs. Look for paper by Ezequiel Treister
et al. on astro-ph. They put in 3 to 1 ratio of obscured to unobscured sources at all
redshifts. Use hard X-ray luminosity function and evolution of Ueda et al.
--> Overall they seem to get reasonable agreement between their model and the z
distribution of GOODS AGN. She thinks that a number of X-ray sources are also missed
because of obscuration.
--> Model approach : 1. Grid of AGN spectra (L_x, N_H from SDSS types and
absorption models) 2. Hard X-ray LF and evolution for type 1 (from Ueda) 3. Geometry
(simplest case : torus) --> Calculate : 1. z distribution 2. optical magnitudes 3. expected
Spitzer flux --> Model predicts large # of high-z obscure sources, but magnitude cut at
R<24 mag introduces ‘missing factors’, but sources should be observable in IR.
--> Then the Spitzer observations show IR bright objects, as she expected. In her view,
the 3:1 ratio holds at all redshifts.
--> interesting paper mentioned : VanDuyne et al. 2004 for AGN seeds
55. Andrea Comastri (INAF) Heavily obscured accreting BH (in hard X-ray surveys)
 HELLAS2/XMM collaboration.
 Try to get SXLF and HXLF (which gives an almost unbiased view of obscured
AGN).
 Points out need to sample L-z plane over wide range, including deep and shallow
surveys w. optical and IR followup.
 He notes that about 20% of sources in deep fields have X/O > 10 (see Koekemoer
talk, EROS). Likely to be highly obscured. Bulk of this population is beyond the
normal spectroscopic limit of 24. They were able to get spectra of 13 high X/O
sources, found 8 type 2 quasars. IR observations show them to have R-K>5, i.e.,
EROs. 7 of 10 are z about1 to 1.5 massive ellipticals hosting an obscured source.
So a good way to find type 2 quasars is to observe EROs with high X/O ratio.
 They make BH mass estimates from the normal galaxy luminosity relation. Get
masses from around 1e8 to 3e9 and L/Ledd from 0.01 up to about 0.1. For the
non-broad line AGN, there is a relation between LX and X/O, which they use to
estimate redshifts.
 They go on to estimate X-ray luminosity functions and their evolution.
 They also find some evidence for an increase of absorbing column density with
redshift.
 There should be a significant number of obscured luminous sources at high
redshift.
 Summary :

Luminous obscured sources are efficiently discovered by combining
hard X-ray surveys with near IR observations.

The X/O ratio is an indicator of luminosity (redshift), implying
extremely faint sources in deep fields.

L and z dependence of N_H distribution of obscured sources.

Hard X-ray data are really needed.
56. Alessandro Marconi (INAF) Local SMBHs as Relics of AGN
--> There is a mismatch between local BH mass function (from M_BH – L_Bul or sigma)
and the mass function of AGN relics (from continuity equations and bolometric
correction)
--> How do we estimate the local BHMF from MBH and Faber Jackson relation. Check
LF obtained from M-sigma relation and M-luminosity relation. They are rather different.
But if one allows properly for the intrinsic dispersion of the relations and the zero point
issues, the results are now more consistent.
--> Use continuity equation to estimate the relic BHMF. This needs the bolometric
luminosity, which requires good bolometric corrections. For consistency the reprocessed
IR radiation has to be removed. Their approach gives a better match between the relic
MF and that derived for the local BHMF from normal galaxies.
--> They have to apply XRB constraints. Ueda et al. included missing Compton-thick
sources. Again, they get good agreement. This leads to efficiency estimates epsilon
around 0.1 and Eddington ratios of 0.1 to 1.
--> This would seem to argue against merging being important for the BHMF.
--> They go on to study when BHs acquired their mass. Massive BHs grow to half their
mass by z=2. Lower mass ones take longer, down to z<1. (‘Anti-hierarchical growth of
BHs’)
--> They also get lifetimes of order 1e8 years. (7-14*10^3 Salpeter times)
--> Conclusions:

Get good agreement between local BHMF and AGN relic function.

Merging does not seem important or does not significantly change the
relic BH mass.

Growth is anti-hierarchical.

BHs seem to grow at reasonable efficiency and Eddington luminosity.

Local BHs grew during AGN phases.
--> Their paper : MNRAS 2003/4 ??
57. Andrea Merloni (MPA) The Anti-Hierarchical Growth of SMBHs
 Use the radio to X-ray relation to get the black hole mass function. From the
XLF, RLF, and the local BHMF, can get the accretion history depending on
accretion efficiency, accretion rate, and bolometric correction.
 He finds that the small BHs are the ones that grow at low redshift.
 The average accretion rate in the universe is decreasing with increasing time.
 He also finds that most of the mass growth occurred with radiatively efficient
accretion.
 Lifetimes : Gets about 1e8 years for the low-z sources.
 Simultaneous growth of BH and galaxies. Using an estimate of the radiative
efficiency and the Magorrian relation, gets a simple parameterization for the
stellar mass and SFR. And it gives not a bad fit to the observed data. Finds that
the M_BH/M_sph increases with redshift. Bears on the M-sigma relation.
 Anti-hierarchical fashion from 0<z<3.5 : BHMF dominated by higher mass
objects at earlier times
 Interesting papers : Merloni 2004, Heckman et al. 2004, Small & Blandford 1992
58. Hagai Netzer (Tel Aviv) Mass, accretion and BH evolution at high z
--> Measuring mass and accretion rate for individual sources has become major industry.
--> How is it done in detail ? Reminds us that the mass estimates are based on the Kaspi
et al. correlation of the radius of the BLR and continuum luminosity. People combine
this correlation with emission line widths to estimate masses. Again, the main and best
correlation is based on Hbeta (which, of course, shifts into the IR for higher z)
--> He reports on new IR measures of Hbeta of luminous quasars at z of 2.5 and 3.5.
Compares with the Boroson Green sample of low z quasars. Finds a few BH masses
exceeding 1e10. Note also that the high z sources have high accretion rates, L/L_Edd.
There new accretion rate estimates do not depend on M_BH or L.
--> By the way, he notes that NLS1s mess up the NV/CIV relation with luminosity that
Hamann Ferland had.
--> Main new idea : accretion rate influences other quantities, such as the metallicity of
the gas in the immediate vicinity of the AGN (higher accretion rate --> higher
metallicities ?)
--> Growth time and BH evolution : in his opinion, episodes of high growth are required
for all AGN at all redshifts -> metal content of emission line gas goes through cycles of
…?…(unclear) --> Starbursts ?
Conclusions :

Large M and high accretion rate at high z –

new : accretion rate correlations (with redshift e.g.)

long growth times of low accretion rate BHs suggest episodic metal
enrichment

existence of clear X-ray signature of merging BH systems (? Relation to
rest?)
59. Roger Blandford (KIPAC) On the Evolution of BHs and their host galaxies : The
Black Hole Manifesto

Economic policy – cosmology. Notes the progress in the relations
between mass, sigma, etc. The field has been transformed in the last
decade or so from the qualitative to the quantitative.

Social policy – births. How and when were seed black holes formed?
Real need for rare 3e9 M_sun BHs early on.

Social policy – childhood. Is there a standard evolutionary sequence?
Relation to nuclear starburst. Obscured (Type 2) sources. What about
the production of radio sources? Dusty outflows from overfed disks?

Social policy – marriages. Binary black holes. Will be the best and
most interesting LISA sources. Formidable relativity challenge. Is
marriage consummated? Effect on gas and fueling? Effect on stars ?
Recoils. Newtonian and radiative. (Classical Menage a trois – situation)

Agricultural policy – the feeding. Growing black holes. Hole growth
must be radiatively efficient to account for AGN luminosity density.
Duty cycle for growth may be 0.005. Overall, his guess is that stars are
a relatively minor contributor to the growth. But the gas supply may be
too large (1000 solar masses/yr). Recall Blandford 1986, Small &
Blandford 1992, understood that the big black holes grew first, then
smaller ones later. Since then, the changes in cosmology and
understanding of cosmology have had a big impact. Now we are
working to relate the black hole mass to surrounding galaxy/bulge.
Market : demand-limited, not supply-driven !

Energy policy – Black holes. Reminds us that all this provides a test of
GR in ways that have not been possible, especially of strong gravity.
Also that rotating BHs could yield up to 29% of rest mass in available
energy. Physics of ergosphere very important. Infalling gas can
“deficit spend”. He thinks that the electromagnetic effects are now
addressable by simulations.Are all BHs just Kerr-metric objects with
mass and spin as only quantity ? BHs are not the event-horizon, they are
the strongly curved space-time itself.

Energy Policy – Accretion I . He thinks accretion is understandable.
High mass supply. Adiabatic flow with photon trapping. Released
binding energy is carried off in a wind with initial power of about 0.1 m
c^2, velocities of 0.03 to 0.1 c. (BALQs). He thinks most growth
occurs in the high mass supply phase. Also the highest luminosity. This
phase controls feedback. Black Holes are GREEN (energetically
efficient).

Energy policy – Accretion II : Intermediate supply rate. Radiative
release of energy. Thin disk.

Energy policy – Accretion III: In the low mass supply case, accretion
also adiabatic because of poor electron-ion coupling. Get thick
magnetized disks. Most power released electromagnetically from
horizon-ergosphere inner disk. Large spin gives us FRIIs, small spin,
FRIs.

Economic policy - the XRB. 40keV spectral break is a challenge. Fe
absorption at 7 keV, most sources at low z. Compton thick population?
Nonthermal sources? Relate to gamma ray background.

Economic policy II – Grand Unified Theory : subcritical accretion ->
dormant AGN, critical accretion -> QSO, Seyferts, BALQ

Economic policy III - Disposal of radio-active waste. Why do jets
form? To carry off the surplus energy. How do they form?
Electromagnetically, in his view. He thinks the very thin jets are
electrical currents. How do they propagate and how are they collimated
?

Domestic policy. AGN are now recognized to be important in galaxy
formation.

Foreign policy. Cluster heating by AGN. X-ray sonograms. Are they
really sound waves? Do they really damp? Do they solve the problems
of cooling flow? Are they powerful enough? Re-ionisation problem ?

Campaign promises. All the future, promised missions, now uncertain.