@article{17615, abstract = {Graham et al. have detected a 5.2 yr periodic optical variability of the quasar PG 1302-102 at redshift z = 0.3, which they interpret as the redshifted orbital period (1 + z)tbin of a putative supermassive black hole binary (SMBHB). Here, we consider the implications of a 3–8 times shorter orbital period, suggested by hydrodynamical simulations of circumbinary discs (CBDs) with nearly equal-mass SMBHBs (q ≡ M2/M1 ≳ 0.3). With the corresponding 2–4 times tighter binary separation, PG 1302 would be undergoing gravitational wave dominated inspiral, and serve as a proof that the BHs can be fuelled and produce bright emission even in this late stage of the merger. The expected fraction of binaries with the shorter tbin, among bright quasars, would be reduced by one to two orders of magnitude, compared to the 5.2 yr period, in better agreement with the rarity of candidates reported by Graham et al. Finally, shorter periods would imply higher binary speeds, possibly imprinting periodicity on the light curves from relativistic beaming, as well as measurable relativistic effects on the Fe K α line. The CBD model predicts additional periodic variability on time-scales of tbin and ≈0.5tbin, as well as periodic variation of broad line widths and offsets relative to the narrow lines, which are consistent with the observations. Future observations will be able to test these predictions and hence the binary+CBD hypothesis for PG 1302.}, author = {D'Orazio, D. J. and Haiman, Zoltán and Duffell, P. and Farris, B. D. and MacFadyen, A. I.}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {3}, pages = {2540--2545}, publisher = {Oxford University Press}, title = {{A reduced orbital period for the supermassive black hole binary candidate in the quasar PG 1302-102?}}, doi = {10.1093/mnras/stv1457}, volume = {452}, year = {2015}, } @article{17641, abstract = {In order to elucidate the origin of spin in both dark matter and baryons in galaxies, we have performed hydrodynamical simulations from cosmological initial conditions. We study atomic cooling haloes in the redshift range 100>z>9 with masses of order 109M⊙ at redshift z=10. We assume that the gas has primordial composition and that H2-cooling and prior star-formation in the haloes have been suppressed. We present a comprehensive analysis of the gas and dark matter properties of four halos with very low (λ≈0.01), low (λ≈0.04), high (λ≈0.06) and very high (λ≈0.1) spin parameter. Our main conclusion is that the spin orientation and magnitude is initially well described by tidal torque linear theory, but later on is determined by the merging and accretion history of each halo. We provide evidence that the topology of the merging region, i.e. the number of colliding filaments, gives an accurate prediction for the spin of dark matter and gas: halos at the center of knots will have low spin while those in the center of filaments will have high spin. The spin of a halo is given by λ≈0.05×(7.6/numberoffilaments)^5.1}, author = {Prieto, Joaquin and Jimenez, Raul and Haiman, Zoltán and González, Roberto E.}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {1}, pages = {784--802}, publisher = {Oxford University Press}, title = {{The origin of spin in galaxies: Clues from simulations of atomic cooling haloes}}, doi = {10.1093/mnras/stv1234}, volume = {452}, year = {2015}, } @article{17663, abstract = {Recently, Planck measured a value of the cosmic microwave background (CMB) optical depth due to electron scattering of τ=0.066±0.016. Here we show that this low value leaves essentially no room for an early partial reionisation of the intergalactic medium (IGM) by high-redshift Population III (Pop III) stars, expected to have formed in low-mass minihaloes. We perform semi-analytic calculations of reionisation which include the contribution from Pop II stars in atomic cooling haloes, calibrated with high-redshift galaxy observations, and Pop III stars in minihaloes with feedback due to Lyman-Werner (LW) radiation and metal enrichment. We find that without LW feedback or prompt metal enrichment (and assuming a minihalo escape fraction of 0.5) the Pop III star formation efficiency cannot exceed ∼a few×10−4, without violating the constraints set by Planck data. This excludes massive Pop III star formation in typical 106M⊙ minihaloes. Including LW feedback and metal enrichment alleviates this tension, allowing large Pop III stars to form early on before they are quenched by feedback. We find that the total density of Pop III stars formed across cosmic time is ≲104−5 M⊙ Mpc−3 and does not depend strongly on the feedback prescription adopted. Additionally, we perform a simple estimate of the possible impact on reionisation of X-rays produced by accretion onto black hole remnants of Pop III stars. We find that unless the accretion duty cycle is very low (≲0.01), this could lead to an optical depth inconsistent with Planck.}, author = {Visbal, Eli and Haiman, Zoltán and Bryan, Greg L.}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {4}, pages = {4457--4467}, publisher = {Oxford University Press}, title = {{Limits on population III star formation in minihaloes implied by Planck}}, doi = {10.1093/mnras/stv1941}, volume = {453}, year = {2015}, } @article{17685, abstract = {We propose an observational test for gravitationally recoiling supermassive black holes (BHs) in active galactic nuclei, based on a correlation between the velocities of BHs relative to their host galaxies, |\Delta v|, and their obscuring dust column densities, \Sigma_{dust} (both measured along the line of sight). We use toy models for the distribution of recoil velocities, BH trajectories, and the geometry of obscuring dust tori in galactic centres, to simulate 2.5x10^5 random observations of recoiling quasars. BHs with recoil velocities comparable to the escape velocity from the galactic centre remain bound to the nucleus, and do not fully settle back to the centre of the torus due to dynamical friction in a typical quasar lifetime. We find that |\Delta v| and \Sigma_ {dust} for these BHs are positively correlated. For obscured (\Sigma_{dust}>0) and for partially obscured (0<\Sigma_{dust}<~2.3 g/m^2) quasars with |\Delta v|>=45 km/s, the sample correlation coefficient between log10(|\Delta v|) and \Sigma_{dust} is r_{45} = 0.28+/-0.02 and r_{45} = 0.13+/-0.02, respectively. Allowing for random +/-100 km/s errors in |\Delta v| unrelated to the recoil dilutes the correlation for the partially obscured quasars to r_{45} = 0.026+/-0.004 measured between |\Delta v| and \Sigma_{dust}. A random sample of >~3,500 obscured quasars with |\Delta v|>=45 km/s would allow rejection of the no-correlation hypothesis with 3 sigma significance 95% of the time. Finally, we find that the fraction of obscured quasars, F_{obs}(|\Delta v|), decreases with |\Delta v| from F_{obs}(<10 km/s)>~0.8 to F_{obs}(>10^3 km/s)<~0.4. This predicted trend can be compared to the observed fraction of type II quasars, and can further test combinations of recoil, trajectory, and dust torus models.}, author = {Raffai, P. and Haiman, Zoltán and Frei, Z.}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {1}, pages = {484--492}, publisher = {Oxford University Press}, title = {{A statistical method to search for recoiling supermassive black holes in active galactic nuclei}}, doi = {10.1093/mnras/stv2371}, volume = {455}, year = {2015}, } @article{17694, abstract = {Constraining the properties of Population III (Pop III) stars will be very challenging because they reside in small galaxies at high redshift which will be difficult to directly detect. In this paper, we suggest that intensity mapping may be a promising method to study Pop III stars. Intensity mapping is a technique proposed to measure large-scale fluctuations of galaxy line emission in three dimensions without resolving individual sources. This technique is well suited for observing many faint galaxies because it can measure their cumulative emission even if they cannot be directly detected. We focus on intensity mapping of He ii recombination lines. These lines are much stronger in Pop III stars than Pop II stars because the harder spectra of Pop III stars are expected to produce many He ii ionizing photons. Measuring the He ii 1640 Å intensity mapping signal, along with the signals from other lines such as Lyα, Hα, and metal lines, could give constraints on the initial mass function (IMF) and star formation rate density of Pop III stars as a function of redshift. To demonstrate the feasibility of these observations, we estimate the strength of the Pop III He ii 1640 Å intensity mapping signal from z = 10–20. We show that at z ≈ 10, the signal could be measured accurately by two different hypothetical future instruments, one which cross-correlates He ii 1640 Å with CO(1–0) line emission from galaxies and the other with 21 cm emission from the intergalactic medium.}, author = {Visbal, Eli and Haiman, Zoltán and Bryan, Greg L.}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {3}, pages = {2506--2513}, publisher = {Oxford University Press}, title = {{Looking for Population III stars with He ii line intensity mapping}}, doi = {10.1093/mnras/stv785}, volume = {450}, year = {2015}, } @article{11582, abstract = {We have observed a sample of typical z ∼ 1 star-forming galaxies, selected from the HiZELS survey, with the new K-band Multi-Object Spectrograph (KMOS) near-infrared, multi-integral field unit instrument on the Very Large Telescope (VLT), in order to obtain their dynamics and metallicity gradients. The majority of our galaxies have a metallicity gradient consistent with being flat or negative (i.e. higher metallicity cores than outskirts). Intriguingly, we find a trend between metallicity gradient and specific star formation rate (sSFR), such that galaxies with a high sSFR tend to have relatively metal poor centres, a result which is strengthened when combined with data sets from the literature. This result appears to explain the discrepancies reported between different high-redshift studies and varying claims for evolution. From a galaxy evolution perspective, the trend we see would mean that a galaxy's sSFR is governed by the amount of metal-poor gas that can be funnelled into its core, triggered either by merging or through efficient accretion. In fact, merging may play a significant role as it is the starburst galaxies at all epochs, which have the more positive metallicity gradients. Our results may help to explain the origin of the fundamental metallicity relation, in which galaxies at a fixed mass are observed to have lower metallicities at higher star formation rates, especially if the metallicity is measured in an aperture encompassing only the central regions of the galaxy. Finally, we note that this study demonstrates the power of KMOS as an efficient instrument for large-scale resolved galaxy surveys.}, author = {Stott, John P. and Sobral, David and Swinbank, A. M. and Smail, Ian and Bower, Richard and Best, Philip N. and Sharples, Ray M. and Geach, James E. and Matthee, Jorryt J}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: abundances, galaxies: evolution, galaxies: kinematics and dynamics}, number = {3}, pages = {2695--2704}, publisher = {Oxford University Press}, title = {{A relationship between specific star formation rate and metallicity gradient within z ∼ 1 galaxies from KMOS-HiZELS}}, doi = {10.1093/mnras/stu1343}, volume = {443}, year = {2014}, } @article{11583, abstract = {Candidate galaxies at redshifts of z ∼ 10 are now being found in extremely deep surveys, probing very small areas. As a consequence, candidates are very faint, making spectroscopic confirmation practically impossible. In order to overcome such limitations, we have undertaken the CF-HiZELS survey, which is a large-area, medium-depth near-infrared narrow-band survey targeted at z = 8.8 Lyman α (Lyα) emitters (LAEs) and covering 10 deg2 in part of the SSA22 field with the Canada–France–Hawaii Telescope (CFHT). We surveyed a comoving volume of 4.7 × 106 Mpc3 to a Lyα luminosity limit of 6.3 × 1043舁erg舁s−1. We look for Lyα candidates by applying the following criteria: (i) clear emission-line source, (ii) no optical detections (ugriz from CFHTLS), (iii) no visible detection in the optical stack (ugriz > 27), (iv) visually checked reliable NBJ and J detections and (v) J − K ≤ 0. We compute photometric redshifts and remove a significant amount of dusty lower redshift line-emitters at z ∼ 1.4 or 2.2. A total of 13 Lyα candidates were found, of which two are marked as strong candidates, but the majority have very weak constraints on their spectral energy distributions. Using follow-up observations with SINFONI/VLT, we are able to exclude the most robust candidates as LAEs. We put a strong constraint on the Lyα luminosity function at z ∼ 9 and make realistic predictions for ongoing and future surveys. Our results show that surveys for the highest redshift LAEs are susceptible of multiple contaminations and that spectroscopic follow-up is absolutely necessary.}, author = {Matthee, Jorryt J and Sobral, David and Swinbank, A. M. and Smail, Ian and Best, P. N. and Kim, Jae-Woo and Franx, Marijn and Milvang-Jensen, Bo and Fynbo, Johan}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution, galaxies: high-redshift, cosmology: observations, dark ages, reionization, first stars}, number = {3}, pages = {2375--2387}, publisher = {Oxford University Press}, title = {{A 10 deg2 Lyman α survey at z=8.8 with spectroscopic follow-up: Strong constraints on the luminosity function and implications for other surveys}}, doi = {10.1093/mnras/stu392}, volume = {440}, year = {2014}, } @article{17614, abstract = {The first generation of stars produces a background of Lyman–Werner (LW) radiation which can photodissociate molecular hydrogen, increasing the mass of dark matter haloes required to host star formation. Previous studies have determined the critical mass required for efficient molecular cooling with a constant LW background. However, the true background is expected to increase rapidly at early times. Neglecting this evolution could underestimate star formation in small haloes that may have started to cool in the past when the LW intensity was much lower. Background evolution is a large source of uncertainty in pre-reionization predictions of the cosmological 21cm signal, which can be observed with future radio telescopes. To address this, we perform zero-dimensional one-zone calculations that follow the density, chemical abundances, and temperature of gas in the central regions of dark matter haloes, including hierarchical growth and an evolving LW background. We begin by studying the physics of haloes subjected to a background that increases exponentially with redshift. We find that when the intensity increases more slowly than JLW(z)∝10−z/5, cooling in the past is a relatively small effect. We then self-consistently compute the cosmological LW background over z = 15–50 and find that cooling in the past due to an evolving background has a modest impact. Finally, we compare these results to three-dimensional hydrodynamical cosmological simulations with varying LW histories. While only a small number of haloes were simulated, the results are consistent with our one-zone calculations.}, author = {Visbal, Eli and Haiman, Zoltán and Terrazas, Bryan and Bryan, Greg L. and Barkana, Rennan}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {1}, pages = {107--114}, publisher = {Oxford University Press}, title = {{High-redshift star formation in a time-dependent Lyman–Werner background}}, doi = {10.1093/mnras/stu1710}, volume = {445}, year = {2014}, } @article{17637, abstract = {Supermassive stars (SMSs; >10^5 Msun) formed in the first protogalaxies with virial temperature T_vir>10^4 K are expected to collapse into seeds of supermassive black hole (SMBHs) in the high-redshift universe (z>7). Fragmentation of the primordial gas is, however, a possible obstacle to SMS formation. We discuss the expected properties of a compact, metal-free, marginally unstable nuclear protogalactic disk, and the fate of the clumps formed in the disk by gravitational instability. Interior to a characteristic radius R_f=few*10^{-2} pc, the disk fragments into massive clumps with M_c~30 Msun. The clumps grow via accretion and migrate inward rapidly on a timescale of ~10^4 yr, which is comparable or shorter than the Kelvin-Helmholz time >10^4 yr. Some clumps may evolve to zero-age main sequence stars and halt gas accretion by radiative feedback, but most of the clumps can migrate inward and merge with the central protostar before forming massive stars. Moreover, we found that dust-induced-fragmentation in metal-enriched gas does not modify these conclusions unless Z> 3*10^{-4} Zsun, because clump migration below this metallicity remains as rapid as in the primordial case. Our results suggest that fragmentation of a compact, metal--poor disk can not prevent the formation of a SMS.}, author = {Inayoshi, Kohei and Haiman, Zoltán}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {2}, pages = {1549--1557}, publisher = {Oxford University Press}, title = {{Does disc fragmentation prevent the formation of supermassive stars in protogalaxies?}}, doi = {10.1093/mnras/stu1870}, volume = {445}, year = {2014}, } @article{17642, abstract = {The presence of quasars at redshifts z > 6 indicates the existence of supermassive black holes (SMBHs) as massive as a few times 10^9 Msun, challenging models for SMBH formation. One pathway is through the direct collapse of gas in T_{vir} > 10^4 K halos; however, this requires the suppression of H_2 cooling to prevent fragmentation. In this paper, we examine a proposed new mechanism for this suppression which relies on cold-mode accretion flows leading to shocks at high densities (n > 10^4 cm^{-3}) and temperatures (T > 10^4 K). In such gas, H_2 is efficiently collisionally dissociated. We use high-resolution numerical simulations to test this idea, demonstrating that such halos typically have lower temperature progenitors, in which cooling is efficient. Those halos do show filamentary flows; however, the gas shocks at or near the virial radius (at low densities), thus preventing the proposed collisional mechanism from operating. We do find that, if we artificially suppress H_2 formation with a high UV background, so as to allow gas in the halo center to enter the high-temperature, high-density "zone of no return", it will remain there even if the UV flux is turned off, collapsing to high density at high temperature. Due to computational limitations, we simulated only three halos. However, we demonstrate, using Monte Carlo calculations of 10^6 halo merger histories, that a few rare halos could assemble rapidly enough to avoid efficient H_2 cooling in all of their progenitor halos, provided that the UV background exceeds J_{21} ~ few at redshifts as high as z ~ 20}, author = {Fernandez, Ricardo and Bryan, Greg L. and Haiman, Zoltán and Li, Miao}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {4}, pages = {3798--3807}, publisher = {Oxford University Press}, title = {{H2 suppression with shocking inflows: Testing a pathway for supermassive black hole formation}}, doi = {10.1093/mnras/stu230}, volume = {439}, year = {2014}, } @article{17645, abstract = {The rapid decline in the number of strong Lyman Alpha (Lya) emitting galaxies at z > 6 provides evidence for neutral hydrogen in the IGM, but is difficult to explain with plausible models for reionization. We demonstrate that the observed reduction in Lya flux from galaxies at z > 6 can be explained by evolution in the escape fraction of ionizing photons, f_esc. We find that the median observed drop in the fraction of galaxies showing strong Lya emission, as well as the observed evolution of the Lya luminosity function both follow from a small increase in f_esc of Delta f_esc ~ 0.1 from f_esc ~ 0.6 at z ~ 6. This high escape fraction may be at odds with current constraints on the ionising photon escape fraction, which favor smaller values of f_esc < 20%. However, models that invoke a redshift evolution of f_ esc that is consistent with these constraints can suppress the z~7 Lya flux to the observed level, if they also include a small evolution in global neutral fraction of Delta x_HI ~ 0.2. Thus, an evolving escape fraction of ionising photons can be a plausible part of the explanation for evolution in the Lya emission of high redshift galaxies. More generally, our analysis also shows that the drop in the Lya fraction is quantitatively consistent with the observed evolution in the Lya luminosity functions of Lya Emitters.}, author = {Dijkstra, Mark and Wyithe, Stuart and Haiman, Zoltán and Mesinger, Andrei and Pentericci, Laura}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {4}, pages = {3309--3316}, publisher = {Oxford University Press}, title = {{Evolution in the escape fraction of ionizing photons and the decline in strong Lyα emission from z > 6 galaxies}}, doi = {10.1093/mnras/stu531}, volume = {440}, year = {2014}, } @article{17650, abstract = {High-redshift quasar observations imply that supermassive black holes (SMBHs) larger than ∼109 M⊙ formed before z=6. That such large SMBHs formed so early in the Universe remains an open theoretical problem. One possibility is that gas in atomic cooling halos exposed to strong Lyman-Werner (LW) radiation forms 104−106 M⊙ supermassive stars which quickly collapse into black holes. We propose a scenario for direct collapse black hole (DCBH) formation based on synchronized pairs of pristine atomic cooling halos. We consider halos at very small separation with one halo being a subhalo of the other. The first halo to surpass the atomic cooling threshold forms stars. Soon after these stars are formed, the other halo reaches the cooling threshold and due to its small distance from the newly formed galaxy, is exposed to the critical LW intensity required to form a DCBH. The main advantage of this scenario is that synchronization can potentially prevent photoevaporation and metal pollution in DCBH-forming halos. Since the halos reach the atomic cooling threshold at nearly the same time, the DCBH-forming halo is only exposed to ionizing radiation for a brief period. Tight synchronization could allow the DCBH to form before stars in the nearby galaxy reach the end of their lives and generate supernovae winds. We use N-body simulations to estimate the abundance of DCBHs formed in this way. The largest source of uncertainty in our estimate is the initial mass function (IMF) of metal free stars formed in atomic cooling halos. We find that even for tight synchronization, the density of DCBHs formed in this scenario could explain the SMBHs implied by z=6 quasar observations. Metal pollution and photoevaporation could potentially reduce the abundance of DCBHs below that required to explain the observations in other models that rely on a high LW flux.}, author = {Visbal, Eli and Haiman, Zoltán and Bryan, Greg L.}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {1}, pages = {1056--1063}, publisher = {Oxford University Press}, title = {{Direct collapse black hole formation from synchronized pairs of atomic cooling haloes}}, doi = {10.1093/mnras/stu1794}, volume = {445}, year = {2014}, } @article{17624, abstract = {A near-equal-mass binary black hole (BH) can clear a central cavity in a circumbinary accretion disc; however, previous works have revealed accretion streams entering this cavity. Here we use 2D hydrodynamical simulations to study the accretion streams and their periodic behaviour. In particular, we perform a suite of simulations, covering different binary mass ratios q = M2/M1 in the range 0.003 ≤ q ≤ 1. In each case, we follow the system for several thousand binary orbits, until it relaxes to a stable accretion pattern. We find the following results: (i) the binary is efficient in maintaining a low-density cavity. However, the time-averaged mass accretion rate into the cavity, through narrow coherent accretion streams, is suppressed by at most a factor of a few compared to a disc with a single BH with the same mass; (ii) for q ≳ 0.05, the accretion rate is strongly modulated by the binary, and depending on the precise value of q, the power spectrum of the accretion rate shows either one, two or three distinct periods; and (iii) for q ≲ 0.05, the accretion rate becomes steady, with no time variations. Most binaries produced in galactic mergers are expected to have q ≳ 0.05. If the luminosity of these binaries tracks their accretion rate, then a periodogram of their light curve could help in their identification, and to constrain their mass ratio and disc properties.}, author = {D'Orazio, Daniel J. and Haiman, Zoltán and MacFadyen, Andrew}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {4}, pages = {2997--3020}, publisher = {Oxford University Press}, title = {{Accretion into the central cavity of a circumbinary disc}}, doi = {10.1093/mnras/stt1787}, volume = {436}, year = {2013}, } @article{17646, abstract = {Structures in Warm Dark Matter (WDM) models are exponentially suppressed below a certain scale, characterized by the dark matter particle mass, mx. Since structures form hierarchically, the presence of collapsed objects at high-redshifts can set strong lower limits on mx. We place robust constraints on mx using recent results from the {\it Swift} database of high-redshift gamma-ray bursts (GRBs). We parameterize the redshift evolution of the ratio between the cosmic GRB rate and star formation rate (SFR) as ∝(1+z)α, thereby allowing astrophysical uncertainties to partially mimic the cosmological suppression of structures in WDM models. Using a maximum likelihood estimator on two different z>4 GRB subsamples (including two bursts at z>8), we constrain mx≳1.6-1.8 keV at 95% C.L., when marginalized over a flat prior in α. We further estimate that 5 years of a SVOM-like mission would tighten these constraints to mx≳2.3 keV. Our results show that GRBs are a powerful probe of high-redshift structures, providing robust and competitive constraints on mx.}, author = {de Souza, R. S. and Mesinger, A. and Ferrara, A. and Haiman, Zoltán and Perna, R. and Yoshida, N.}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {4}, pages = {3218--3227}, publisher = {Oxford University Press}, title = {{Constraints on warm dark matter models from high-redshift long gamma-ray bursts}}, doi = {10.1093/mnras/stt674}, volume = {432}, year = {2013}, } @article{17653, abstract = {Observations of quasars at redshifts z > 6 reveal that 10^9 Msol supermassive black holes (SMBHs) had already formed when the Universe was < 0.9 Gyr old. One hypothesis for the origins of these SMBHs is that they grew from the remnants of the first generation of massive stars, which formed in low-mass (~ 10^5 to 10^6 Msol) dark matter minihaloes at z > 20. This is the regime where baryonic streaming motions--the relative velocities of baryons with respect to dark matter in the early Universe--most strongly inhibit star formation by suppressing gas infall and cooling. We investigate the impact of this effect on the growth of the first SMBHs using a suite of high-fidelity, ellipsoidal-collapse Monte Carlo merger-tree simulations. We find that the suppression of seed BH formation by the streaming motions significantly reduces the number density of the most massive BHs at z > 15, but the residual effect at lower redshifts is essentially negligible. The streaming motions can reduce by a factor of few the number density of the most luminous quasars at z ~ 10-11, where such objects could be detected by the James Webb Space Telescope. We conclude, with minor theoretical caveats, that baryonic streaming motions are unlikely to pose a significant additional obstacle to the formation of the observed high-redshift quasar SMBHs. Nor do they appreciably affect the heating and reionization histories of the Universe or the merger rates of nuclear BHs in the mass and redshift ranges of interest for proposed gravitational-wave detectors.}, author = {Tanaka, Takamitsu L. and Li, Miao and Haiman, Zoltán}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {4}, pages = {3559--3567}, publisher = {Oxford University Press}, title = {{The effect of baryonic streaming motions on the formation of the first supermassive black holes}}, doi = {10.1093/mnras/stt1553}, volume = {435}, year = {2013}, } @article{17683, abstract = {When a sufficiently massive satellite (or secondary) black hole is embedded in a gas disc around a (primary) supermassive black hole, it can open an empty gap in the disc. A gap-opening secondary close to the primary will leave an imprint in the broad component of the Fe Kα emission line, which varies in a unique and predictable manner. If the gap persists into the innermost disc, the effect consists of a pair of dips in the broad line which ripple blue-ward and red-ward from the line centroid energy, respectively, as the gap moves closer to the primary. This ripple effect could be unambiguously detectable and allow an electromagnetic monitoring of massive black hole mergers as they occur. As the mass ratio of the secondary to primary black hole increases to q ≳ 0.01, we expect the gap to widen, possibly clearing a central cavity in the inner disc, which shows up in the broad Fe Kα line component. If the secondary stalls at ≥ 102rg in its in-migration, due to low corotating gas mass, a detectable ripple effect occurs in the broad line component on the disc viscous time-scale as the inner disc drains and the outer disc is dammed. If the secondary maintains an accretion disc within a central cavity, due to dam bursting or leakage, a periodic ‘see-saw’ oscillation effect is exhibited in the observed line profile. Here, we demonstrate the range of ripple effect signatures potentially detectable with Astro-H and IXO/Athena, and oscillation effects potentially detectable with XMM–Newton or LOFT for a wide variety of merger and disc conditions, including gap width (or cavity size), disc inclination angle and emissivity profile, damming of the accretion flow by the secondary, and a minidisc around the satellite black hole. A systematic study of ripple effects would require a telescope effective area substantially larger than that planned for IXO/Athena. Future mission planning should take this into account. Observations of the ripple effect and periodic oscillations can be used to provide an early warning of gravitational radiation emission from the AGN. Once gravitational waves consistent with massive black hole mergers are detected, an archival search for the Fe Kα ripple effect or periodic oscillations will help in localizing their origin.}, author = {McKernan, B. and Ford, K. E. S. and Kocsis, B. and Haiman, Zoltán}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {2}, pages = {1468--1482}, publisher = {Oxford University Press}, title = {{Ripple effects and oscillations in the broad Fe Kα line as a probe of massive black hole mergers}}, doi = {10.1093/mnras/stt567}, volume = {432}, year = {2013}, } @article{17684, abstract = {We have performed cosmo-hydro simulations using the RAMSES code to study atomic cooling (ACHs) haloes at z=10 with masses 5E7Msun<~M<~2E9Msun. We assume primordial gas and H2-cooling and prior star-formation have been suppressed. We analysed 19 haloes (gas and DM) at a resolution of ~10 (proper) pc, selected from a total volume of ~2E3 (comoving) Mpc3. This is the largest statistical hydro-sim. study of ACHs at z>10 to date. We examine the morphology, angular momentum (AM), thermodynamic, and turbulence of these haloes, in order to assess the prevalence of disks and supermassive black holes (SMBHs). We find no correlation between either the magnitude or the direction of the AM of the gas and its parent DM halo. Only 3 haloes form rotationally supported cores. Two of the most massive haloes form massive, compact overdense blobs. These blobs have an accretion rate ~0.5 Msun/yr (at a distance of 100 pc), and are possible sites of SMBH formation. Our results suggest that the degree of rotational support and the fate of the gas in a halo is determined by its large-scale environment and merger history. In particular, the two haloes forming blobs are located at knots of the cosmic web, cooled early on, and experienced many mergers. The gas in these haloes is lumpy and highly turbulent, with Mach N. >~ 5. In contrast, the haloes forming rotationally supported cores are relatively more isolated, located midway along filaments, cooled more recently, and underwent fewer mergers. Thus, the gas in these haloes is less lumpy and less turbulent (Mach <~ 4), and could retain most of its AM. The remaining 14 haloes have intermediate properties. If verified in a larger sample of haloes and with additional physics, our results will have implications for observations of the highest-redshift galaxies and quasars with JWST.}, author = {Prieto, Joaquin and Jimenez, Raul and Haiman, Zoltán}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {3}, pages = {2301--2325}, publisher = {Oxford University Press}, title = {{Gas infall into atomic cooling haloes: On the formation of protogalactic discs and supermassive black holes at z > 10}}, doi = {10.1093/mnras/stt1730}, volume = {436}, year = {2013}, } @article{17613, abstract = {We study the interaction of a supermassive black hole (SMBH) binary and a standard radiatively efficient thin accretion disk. We examine steady-state configurations of the disk and migrating SMBH system, self-consistently accounting for tidal and viscous torques and heating, radiative diffusion limited cooling, gas and radiation pressure, and the decay of the binary's orbit. We obtain a "phase diagram" of the system as a function of binary parameters, showing regimes in which both the disk structure and migration have a different character. Although massive binaries can create a central gap in the disk at large radii, the tidal barrier of the secondary causes a significant pile-up of gas outside of its orbit, which can lead to the closing of the gap. We find that this spillover occurs at an orbital separation as large as ~200 M_7^{-1/2} gravitational radii, where M = 10^7 M_7 Msun is the total binary mass. If the secondary is less massive than ~10^6 Msun, then the gap is closed before gravitational waves (GWs) start dominating the orbital decay. In this regime, the disk is still strongly perturbed, but the piled-up gas continuously overflows as in a porous dam, and crosses inside the secondary's orbit. The corresponding migration rate, which we label Type 1.5, is slower than the usual limiting cases known as Type I and II migration. Compared to an unperturbed disk, the steady-state disk in the overflowing regime is up to several hundred times brighter in the optical bands. Surveys such as PanSTARRS or LSST may discover the periodic variability of this population of binaries. Our results imply that the circumbinary disks around SMBHs can extend to small radii during the last stages of their merger, when they are detectable by LISA, and may produce coincident electromagnetic (EM) emission similar to active galactic nuclei (AGN).}, author = {Kocsis, Bence and Haiman, Zoltán and Loeb, Abraham}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {3}, pages = {2680--2700}, publisher = {Oxford University Press}, title = {{Gas pile-up, gap overflow and Type 1.5 migration in circumbinary discs: Application to supermassive black hole binaries}}, doi = {10.1111/j.1365-2966.2012.22118.x}, volume = {427}, year = {2012}, } @article{17660, abstract = {Many astrophysical binaries, from planets to black holes, exert strong torques on their circumbinary accretion discs, and are expected to significantly modify the disc structure. Despite the several decade long history of the subject, the joint evolution of the binary + disc system has not been modelled with self-consistent assumptions for arbitrary mass ratios and accretion rates. Here, we solve the coupled binary–disc evolution equations analytically in the strongly perturbed limit, treating the azimuthally averaged angular momentum exchange between the disc and the binary and the modifications to the density, scaleheight, and viscosity self-consistently, including viscous and tidal heating, diffusion limited cooling, radiation pressure and the orbital decay of the binary. We find a solution with a central cavity and a migration rate similar to those previously obtained for Type II migration, applicable for large masses and binary separations, and near-equal mass ratios. However, we identify a distinct new regime, applicable at smaller separations and masses, and mass ratio in the range 10−3 ≲ q ≲ 0.1. For these systems, gas piles up outside the binary's orbit, but rather than creating a cavity, it continuously overflows as in a porous dam. The disc profile is intermediate between a weakly perturbed disc (producing Type I migration) and a disc with a gap (with Type II migration). However, the migration rate of the secondary is typically slower than both Type I and Type II rates. We term this new regime ‘Type 1.5’ migration.}, author = {Kocsis, Bence and Haiman, Zoltán and Loeb, Abraham}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {3}, pages = {2660--2679}, publisher = {Oxford University Press}, title = {{Gas pile-up, gap overflow and Type 1.5 migration in circumbinary discs: General theory}}, doi = {10.1111/j.1365-2966.2012.22129.x}, volume = {427}, year = {2012}, } @article{17674, abstract = {The power spectrum of cosmic infrared background (CIB) anisotropies is sensitive to the connection between star formation and dark matter haloes over the entire cosmic star formation history. Here we develop a model that associates star‐forming galaxies with dark matter haloes and their subhaloes. The model is based on a parametrized relation between the dust‐processed infrared luminosity and (sub)halo mass. By adjusting three free parameters, we attempt to simultaneously fit the four frequency bands of the Planck measurement of the CIB anisotropy power spectrum. To fit the data, we find that the star formation efficiency must peak on a halo mass scale of ≈5 × 10^12 M⊙ and the infrared luminosity per unit mass must increase rapidly with redshift. By comparing our predictions with a well‐calibrated phenomenological model for shot noise, and with a direct observation of source counts, we show that the mean duty cycle of the underlying infrared sources must be near unity, indicating that the CIB is dominated by long‐lived quiescent star formation, rather than intermittent short ‘starbursts’. Despite the improved flexibility of our model, the best simultaneous fit to all four Planck channels remains relatively poor. We discuss possible further extensions to alleviate the remaining tension with the data. Our model presents a theoretical framework for a future joint analysis of both background anisotropy and source count measurements.}, author = {Shang, Cien and Haiman, Zoltán and Knox, Lloyd and Oh, S. Peng}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {4}, pages = {2832--2845}, publisher = {Oxford University Press}, title = {{Improved models for cosmic infrared background anisotropies: New constraints on the infrared galaxy population}}, doi = {10.1111/j.1365-2966.2012.20510.x}, volume = {421}, year = {2012}, }