Martin G. Haehnelt

University of Cambridge, Cambridge, England, United Kingdom

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Publications (161)558.5 Total impact

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    ABSTRACT: QSO near-zones are an important probe of the the ionization state of the IGM at z ~ 6-7, at the end of reionization. We present here high-resolution cosmological 3D radiative transfer simulations of QSO environments for a wide range of host halo masses, 10^{10-12.5} M_sun. Our simulated near-zones reproduce both the overall decrease of observed near-zone sizes at 6 < z < 7 and their scatter. The observable near-zone properties in our simulations depend only very weakly on the mass of the host halo. The size of the H II region expanding into the IGM is generally limited by (super-)Lyman Limit systems loosely associated with (low-mass) dark matter haloes. This leads to a strong dependence of near-zone size on direction and drives the large observed scatter. In the simulation centred on our most massive host halo, many sightlines show strong red damping wings even for initial volume averaged neutral hydrogen fractions as low as ~ 10^{-3}. For QSO lifetimes long enough to allow growth of the central supermassive black hole while optically bright, we can reproduce the observed near-zone of ULAS J1120+0641 only with an IGM that is initially neutral. Our results suggest that larger samples of z > 7 QSOs will provide important constraints on the evolution of the neutral hydrogen fraction and thus on how late reionization ends.
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    ABSTRACT: We calibrate here cosmological radiative transfer simulation with ATON/RAMSES with a range of measurements of the Lyman alpha opacity from QSO absorption spectra. We find the Lyman alpha opacity to be very sensitive to the exact timing of hydrogen reionisation. Models reproducing the measured evolution of the mean photoionisation rate and average mean free path reach overlap at z ~ 7 and predict an accelerated evolution of the Lyman alpha opacity at z > 6 consistent with the rapidly evolving luminosity function of Lyman alpha emitters in this redshift range. Similar to "optically thin" simulations our full radiative transfer simulations fail, however, to reproduce the high-opacity tail of the Lyman alpha opacity PDF at z > 5. We argue that this is due to spatial UV fluctuations in the post-overlap phase of reionisation on substantially larger scales than predicted by our source model, where the ionising emissivity is dominated by large numbers of sub-L* galaxies. We further argue that this suggests a significant contribution to the ionising UV background by much rarer bright sources at high redshift.
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    Harley Katz, Debora Sijacki, Martin G. Haehnelt
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    ABSTRACT: We study how runaway stellar collisions in high redshift, metal poor star clusters form very massive stars (VMSs) that can directly collapse to intermediate mass black holes (IMBHs). We follow the evolution of a pair of two neighboring high-redshift mini-halos which are expected to host central nuclear star clusters (NSCs) with very high resolution, cosmological hydrodynamical zoom-in simulations with the adaptive mesh refinement code RAMSES. One of the two mini-halos enriches the central NSC of the other mini-halo to a critical metallicity, sufficient for Pop. II star formation at redshift z~27. We then use the spatial configuration of the flattened, asymmetrical gas cloud forming in the RAMSES simulations at the core of the metal enriched halo to set the initial conditions for simulations of an initially non-spherical star cluster with the direct summation code NBODY6 which are compared to about 2000 NBODY6 simulations of spherical star clusters for a wide range of star cluster parameters. In this way we establish that the results of our modeling are robust to changes in the assumptions for stellar initial mass function, binary fraction, and degree of initial mass mass segregation. Most of our simulations result in the formation of VMSs. The final mass of the VMS that forms depends thereby strongly on the initial mass of the NSC as well as the initial central density. For the initial central densities suggested by our RAMSES simulations, VMSs with M_VMS>400 M_sun can form in clusters with stellar masses of ~10^4 M_sun and this can increase to well over 1000 M_sun for more massive and denser clusters. The high probability we find for forming a VMS in these halos at such an early cosmic time makes collisional runaway of Pop. II star clusters a promising channel for producing large numbers of high-redshift IMBHs that may act as the seeds of super-massive black holes.
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    ABSTRACT: We combine high resolution hydrodynamical simulations with an intermediate resolution, dark matter only simulation and an analytical model for the growth of ionized regions to estimate the large scale distribution and redshift evolution of the visibility of Ly$\alpha$ emission in $6 \leq z\leq 8$ galaxies. The inhomogeneous distribution of neutral hydrogen during the reionization process results in significant fluctuations in the Ly$\alpha$ transmissivity on large scales, and is sensitive not only to the ionized fraction of the intergalactic medium by volume and amplitude of the local ionizing background, but also to the relative velocity shift of the Ly$\alpha$ emission line due to resonant scattering. We reproduce a decline in the space density of Ly$\alpha$ emitting galaxies as rapid as observed with a volume-weighted neutral fraction of $\sim 30$ (50) per cent at $z=7$ ($z=8$), and a typical Ly$\alpha$ line velocity offset of $100\rm\,km\,s^{-1}$ redward of systemic at $z=6$ which decreases toward higher redshift. The latest preliminary (12/2014) Planck results indicate such a recent end to reionization is no longer disfavoured by constraints from the cosmic microwave background.
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    Tiago Costa, Debora Sijacki, Martin G. Haehnelt
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    ABSTRACT: Observations of the emission from spatially extended cold gas around bright high-redshift QSOs reveal surprisingly large velocity widths exceeding 2000 km s^(-1), out to projected distances as large as 30 kpc. The high velocity widths have been interpreted as the signature of powerful AGN-driven outflows. Naively, these findings appear in tension with hydrodynamic models in which AGN-driven outflows are energy-driven and thus very hot with typical temperatures T = 10^6-7 K. Using the moving-mesh code Arepo, we perform 'zoom-in' cosmological simulations of a z = 6 QSO and its environment, following black hole growth and feedback via energy-driven outflows. In the simulations, the QSO host galaxy is surrounded by a clumpy circum-galactic medium pre-enriched with metals due to supernovae-driven galactic outflows. As a result, part of the AGN-driven hot outflowing gas can cool radiatively, leading to large amounts (> 10^9 M_sun) of cold gas comoving with the hot bipolar outflow. This results in velocity widths of spatially extended cold gas similar to those observed. We caution, however, that gas inflows, random motions in the deep potential well of the QSO host galaxy and cooling of supernovae-driven winds contribute significantly to the large velocity width of the cold gas in the simulations, complicating the interpretation of observational data.
    Monthly Notices of the Royal Astronomical Society Letters 11/2014; 448(1). DOI:10.1093/mnrasl/slu193 · 5.52 Impact Factor
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    ABSTRACT: We compare cosmological hydrodynamical simulations combined with the homogeneous metagalactic UV background (UVB) of Haardt & Madau (2012) (HM2012) to observations of the Lyman-alpha forest that are sensitive to the thermal and ionization state of the intergalactic medium (IGM). The transition from optically thick to thin photoheating predicted by the simple one-zone, radiative transfer model implemented by HM2012 predicts a thermal history that is in remarkably good agreement with the observed rise of the IGM temperature at z~3 if we account for the expected evolution of the volume filling factor of HeIII. Our simulations indicate that there may be, however, some tension between the observed peak in the temperature evolution and the rather slow evolution of the HeII opacities suggested by recent Hubble Space Telescope/COS measurements. The HM2012 UVB also underpredicts the metagalactic hydrogen photoionization rate required by our simulations to match the observed opacity of the forest at z>4 and z<2.
    Monthly Notices of the Royal Astronomical Society 10/2014; 450(4). DOI:10.1093/mnras/stv773 · 5.23 Impact Factor
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    ABSTRACT: We examine the kinematic structure of Damped Lyman-alpha Systems (DLAs) in a series of cosmological hydrodynamic simulations using the AREPO code. We are able to match the distribution of velocity widths of associated low ionisation metal absorbers substantially better than earlier work. Our simulations produce a population of DLAs dominated by halos with virial velocities around 70 km/s, consistent with a picture of relatively small, faint objects. In addition, we reproduce the observed correlation between velocity width and metallicity and the equivalent width distribution of SiII. Some discrepancies of moderate statistical significance remain; too many of our spectra show absorption concentrated at the edge of the profile and there are slight differences in the exact shape of the velocity width distribution. We show that the improvement over previous work is mostly due to our strong feedback from star formation and our detailed modelling of the metal ionisation state.
    Monthly Notices of the Royal Astronomical Society 07/2014; 447(2). DOI:10.1093/mnras/stu2542 · 5.23 Impact Factor
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    Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series; 06/2014
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    Tiago Costa, Debora Sijacki, Martin G. Haehnelt
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    ABSTRACT: We employ hydrodynamical simulations using the moving-mesh code AREPO to investigate the role of energy and momentum input from Active Galactic Nuclei (AGN) in driving large-scale galactic outflows. We start by reproducing analytic solutions for both energy- and momentum-driven outflowing shells in simulations of a spherical isolated dark matter potential with gas in hydrostatic equilibrium and with no radiative cooling. We confirm that for this simplified setup, galactic outflows driven by a momentum input rate of order L_Edd/c can establish an M_BH - sigma relation with slope and normalisation similar to that observed. We show that momentum input at a rate of L_Edd/c is however insufficient to drive efficient outflows once cooling and gas inflows as predicted by cosmological simulations at resolved scales are taken into account. We argue that observed large-scale AGN-driven outflows are instead likely to be energy-driven and show that such outflows can reach momentum fluxes exceeding 10 L_Edd/c within the innermost 10 kpc of the galaxy. The outflows are highly anisotropic, with outflow rates and a velocity structure found to be inadequately described by spherical outflow models. We verify that the hot energy-driven outflowing gas is expected to be strongly affected by metal-line cooling, leading to significant amounts (>10^9 M_sun) of entrained cold gas.
    Monthly Notices of the Royal Astronomical Society 06/2014; 444(3). DOI:10.1093/mnras/stu1632 · 5.23 Impact Factor
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    ABSTRACT: We examine the abundance, clustering and metallicity of Damped Lyman-$\alpha$ Absorbers (DLAs) in hydrodynamic cosmological simulations using the moving mesh code AREPO. We incorporate models of supernova and AGN feedback, and molecular hydrogen formation. We compare our simulations to the column density distribution function at $z=3$, the total DLA abundance at $z=2-4$, the measured DLA bias at $z=2$ and DLA metallicities at $z=2-4$. Our preferred models produce populations of DLAs in good agreement with most of these observations, except the DLA abundance at $z < 3$, which we show requires stronger feedback in $10^{11-12} h^{-1} M_\odot$ mass halos. While the DLA population probes a range of halo masses, we find the cross-section is dominated by halos of mass $10^{10.5} h^{-1} M_\odot$ at $z=3$ and $10^{11} h^{-1} M_\odot$ at $z=2$. Simulations without feedback are in strong tension with all these observables, indicating a need for strong stellar feedback at $z=2-4$ independently of the star formation threshold. We demonstrate that DLAs are a powerful probe of the physical processes that shape galaxy formation, in particular supernova feedback processes. As DLAs arise from gas at a lower density than the star formation threshold, the information they provide is complementary to that contained in the stellar component of galaxies.
    Monthly Notices of the Royal Astronomical Society 05/2014; 445(3). DOI:10.1093/mnras/stu1923 · 5.23 Impact Factor
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    Luke A. Barnes, Martin G. Haehnelt
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    ABSTRACT: We discuss the recent BOSS measurement of a rather high bias factor for the host galaxies/haloes of Damped Lyman-alpha Absorbers (DLAs), in the context of our previous modelling of the physical properties of DLAs within the {\Lambda}CDM paradigm. Joint modelling of the column density distribution, the velocity width distribution of associated low ionization metal absorption, and the bias parameter suggests that DLAs are hosted by galaxies with dark matter halo masses in the range 10.5 < log Mv < 13, with a rather sharp cutoff at the lower mass end, corresponding to viral velocities of ~90 km/s. The observed properties of DLAs appear to suggest very efficient (stellar) feedback in haloes with masses/virial velocities below the cutoff and a large retained baryon fraction (> 35%) in haloes above the cutoff.
    Monthly Notices of the Royal Astronomical Society 03/2014; 440(3). DOI:10.1093/mnras/stu445 · 5.23 Impact Factor
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    John A. Regan, Peter H. Johansson, Martin G. Haehnelt
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    ABSTRACT: We have performed high-resolution numerical simulations with the hydrodynamical AMR code Enzo to investigate the formation of massive seed black holes in a sample of six dark matter haloes above the atomic cooling threshold. The aim of this study is to illustrate the effects of varying the maximum refinement level on the final object formed. The virial temperatures of the simulated haloes range from $\rm{T} \sim 10000\ \rm{K} - 16000\ \rm{K}$ and they have virial masses in the range $\rm{M} \sim 2 \times 10^7 \rm{M_{\odot}}$ to $\rm{M} \sim 7 \times 10^7 \rm{M_{\odot}}$ at $z \sim 15$. The outcome of our six fiducial simulations is both generic and robust. A rotationally supported, marginally gravitationally stable, disk forms with an exponential profile. The mass and scale length of this disk depends strongly on the maximum refinement level used. Varying the maximum refinement level by factors between 1 / 64 to 256 times the fiducial level illustrates the care that must be taken in interpreting the results. The lower resolution simulations show tentative evidence that the gas may become rotationally supported out to 20 pc while the highest resolution simulations show only weak evidence of rotational support due to the shorter dynamical times for which the simulation runs. The higher resolution simulations do, however, point to fragmentation at small scales of the order of $\sim 100$ AU. In the highest resolution simulations a central object of a few times $10^2\ \rm{M_{\odot}}$ forms with multiple strongly bound, Jeans unstable, clumps of $\sim 10\ \rm{M_{\odot}}$ and radii of 10 - 20 AU suggesting the formation of dense star clusters in these haloes.
    Monthly Notices of the Royal Astronomical Society 12/2013; 439(1). DOI:10.1093/mnras/stu068 · 5.23 Impact Factor
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    ABSTRACT: Low ionization metal absorption due to OI has been identified as an important probe of the inter-/circumgalactic medium at the tail-end of reionization. We use here high-resolution hydrodynamic simulations to interpret the incidence rate of OI absorbers at z~6. For plausible assumptions about the photo-ionization rate due to the meta-galactic UV background and the self-shielding of optically thick absorbers, our modelling reproduces the equivalent width distribution and incidence rate of the observations by Becker et al. (2011) with a model where the weak OI absorbers have typical HI column densities in the range of sub-DLAs, densities of 80 times the mean baryonic density and metallicities of about 1/500 th solar. This is similar to the metallicity inferred at similar overdensities at z~3, suggesting that the metal enrichment of the CGM has already progressed considerably by z~6. The apparently rapid evolution of the incidence rates for OI absorption over 5<z<6 mirrors that of LLSs at lower redshift and is mainly due to the rapid decrease of the meta-galactic photo-ionization rate at z>5. Assuming the same metallicity-density relation inferred at z~6, we predict the incidence rate of OI absorbers at z=7-8 to continue to rise rapidly with increasing redshift as the IGM becomes more neutral. If the distribution of metals extends to lower density regions, OI absorbers will allow the metal enrichment of the increasingly neutral filamentary structures of the cosmic web to be probed.
    Monthly Notices of the Royal Astronomical Society 10/2013; 438(2). DOI:10.1093/mnras/stt2324 · 5.23 Impact Factor
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    ABSTRACT: Building on the experience of the high-resolution community with the suite of VLT high-resolution spectrographs, which has been tremendously successful, we outline here the (science) case for a high-fidelity, high-resolution spectrograph with wide wavelength coverage at the E-ELT. Flagship science drivers include: the study of exo-planetary atmospheres with the prospect of the detection of signatures of life on rocky planets; the chemical composition of planetary debris on the surface of white dwarfs; the spectroscopic study of protoplanetary and proto-stellar disks; the extension of Galactic archaeology to the Local Group and beyond; spectroscopic studies of the evolution of galaxies with samples that, unlike now, are no longer restricted to strongly star forming and/or very massive galaxies; the unraveling of the complex roles of stellar and AGN feedback; the study of the chemical signatures imprinted by population III stars on the IGM during the epoch of reionization; the exciting possibility of paradigm-changing contributions to fundamental physics. The requirements of these science cases can be met by a stable instrument with a spectral resolution of R~100,000 and broad, simultaneous spectral coverage extending from 370nm to 2500nm. Most science cases do not require spatially resolved information, and can be pursued in seeing-limited mode, although some of them would benefit by the E-ELT diffraction limited resolution. Some multiplexing would also be beneficial for some of the science cases. (Abridged)
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    ABSTRACT: We present new measurements of the thermal state of the intergalactic medium (IGM) at z~2.4 derived from absorption line profiles in the Lyman-alpha forest. We use a large set of high-resolution hydrodynamical simulations to calibrate the relationship between the temperature-density relation in the IGM and the distribution of HI column densities, N_HI, and velocity widths, b_HI, of discrete Lyman-alpha forest absorbers. This calibration is then applied to the measurement of the lower cut-off of the b_HI-N_HI distribution recently presented by Rudie et al. (2012). We infer a power-law temperature-density relation, T=T_0\Delta^(\gamma-1), with a temperature at mean density, T_0=[1.00^+0.32_-0.21] x10^4 K and slope (\gamma-1)=0.54\pm 0.11. The slope is fully consistent with that advocated by the analysis of Rudie et al. (2012); however, the temperature at mean density is lower by almost a factor of two, a difference due primarily to an adjustment in the relationship between column density and physical density assumed by these authors. These new results bring the b_HI-N_HI cut-off constraint into excellent agreement with the recent temperature measurements of Becker et al. (2011), based on the curvature of the transmitted flux in the Lyman-alpha forest. The fact that independent analyses using different techniques constrain IGM temperatures to less than 30 per cent and are mutually consistent suggests that the thermal state of the IGM at this redshift is now reasonably well characterised, at least over the range of densities probed by these methods. Future works using these and other techniques should be able to further clarify the thermal structure and evolution of the IGM at a level of precision sufficient to deliver new insights into cosmic reionisation and the properties of ionising sources.
    Monthly Notices of the Royal Astronomical Society 08/2013; 438(3). DOI:10.1093/mnras/stt2374 · 5.23 Impact Factor
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    Tiago Costa, Debora Sijacki, Michele Trenti, Martin G. Haehnelt
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    ABSTRACT: We employ cosmological hydrodynamical simulations to investigate models in which the supermassive black holes (BHs) powering luminous z ~ 6 QSOs grow from massive seeds. We simulate at high resolution 18 fields sampling regions with densities ranging from the mean cosmic density all the way to the highest sigma peaks in the Millennium simulation volume. Only in the most massive halos, BHs can grow to masses up to ~ 10^9 Msun by z ~ 6 without invoking super-Eddington accretion. Accretion onto the most massive BHs becomes limited by thermal AGN feedback by z ~ 9-8 with further BH growth proceeding in short Eddington limited bursts. Our modelling suggests that current flux-limited surveys of QSOs at high redshift preferentially detect objects at their peak luminosity and therefore miss a substantial population of QSOs powered by similarly massive BHs but with low accretion rates. To test whether the required host halo masses are consistent with the observed galaxy environment of z ~ 6 QSOs, we produce realistic rest-frame UV images of our simulated galaxies. Without strong stellar feedback, our simulations predict numbers of bright galaxies larger than observed by a factor ten or more. Supernova-driven galactic winds reduce the predicted numbers to a level consistent with observations indicating that stellar feedback was already very efficient at high redshifts. We have further investigated the effect of thermal AGN feedback on the surrounding gas. Our adopted AGN feedback prescription drives mostly energy-driven highly anisotropic outflows with gas speeds of >= 1000 km/s to distances of >= 10 kpc consistent with observations. The spatially extended thermal X-ray emission around bright QSOs powered by these outflows can exceed by large factors the emission expected without AGN feedback and is an important diagnostic of the mechanism whereby AGN feedback energy couples to surrounding gas.
    Monthly Notices of the Royal Astronomical Society 07/2013; 439(2). DOI:10.1093/mnras/stu101 · 5.23 Impact Factor
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    ABSTRACT: We present updated constraints on the free-streaming of warm dark matter (WDM) particles derived from an analysis of the Lya flux power spectrum measured from high-resolution spectra of 25 z > 4 quasars obtained with the Keck High Resolution Echelle Spectrometer (HIRES) and the Magellan Inamori Kyocera Echelle (MIKE) spectrograph. We utilize a new suite of high-resolution hydrodynamical simulations that explore WDM masses of 1, 2 and 4 keV (assuming the WDM consists of thermal relics), along with different physically motivated thermal histories. We carefully address different sources of systematic error that may affect our final results and perform an analysis of the Lya flux power with conservative error estimates. By using a method that samples the multi-dimensional astrophysical and cosmological parameter space, we obtain a lower limit mwdm > 3.3 keV (2sigma) for warm dark matter particles in the form of early decoupled thermal relics. Adding the Sloan Digital Sky Survey (SDSS) Lya flux power spectrum does not improve this limit. Thermal relics of masses 1 keV, 2 keV and 2.5 keV are disfavoured by the data at about the 9sigma, 4sigma and 3sigma C.L., respectively. Our analysis disfavours WDM models where there is a suppression in the linear matter power spectrum at (non-linear) scales corresponding to k=10h/Mpc which deviates more than 10% from a LCDM model. Given this limit, the corresponding "free-streaming mass" below which the mass function may be suppressed is 2x10^8 Msun/h. There is thus very little room for a contribution of the free-streaming of WDM to the solution of what has been termed the small scale crisis of cold dark matter.
    Physical review D: Particles and fields 06/2013; 88(4). DOI:10.1103/PhysRevD.88.043502 · 4.86 Impact Factor
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    ABSTRACT: A spectroscopically detected Lyman alpha emitting halo at redshift 3.216 in the GOODS-N field is found to reside at the convergence of several Lyman alpha filaments. HST images show that some of the filaments are inhabited by galaxies. Several of the galaxies in the field have pronounced head-tail structures, which are partly aligned with each other. The blue colors of most tails suggest the presence of young stars, with the emission from at least one of the galaxies apparently dominated by high equivalent width Lyman alpha. Faint, more diffuse, and similarly elongated, apparently stellar features, can be seen over an area with a linear extent of at least 90 kpc. The region within several arcseconds of the brightest galaxy exhibits spatially extended emission by HeII, NV and various lower ionization metal lines. The gas-dynamical features present are strongly reminiscent of ram-pressure stripped galaxies, including evidence for recent star formation in the stripped contrails. Spatial gradients in the appearance of several galaxies may represent a stream of galaxies passing from a colder to a hotter intergalactic medium. The stripping of gas from the in-falling galaxies, in conjunction with the occurrence of star formation and stellar feedback in the galactic contrails suggests a mechanism for the metal enrichment of the high redshift intergalactic medium that does not depend on long-range galactic winds, at the same time opening a path for the escape of ionizing radiation from galaxies.
    Monthly Notices of the Royal Astronomical Society 05/2013; 441(1). DOI:10.1093/mnras/stu528 · 5.23 Impact Factor
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    ABSTRACT: We study the X-ray emission from NGC 1277, a galaxy in the core of the Perseus cluster, for which van den Bosch et al. have recently claimed the presence of an ultramassive black hole (UMBH) of mass 1.7× 10^{10}{ M_{{⊙}}}, unless the initial mass function of the stars in the stellar bulge is extremely bottom heavy. The X-rays originate in a power-law component of luminosity 1.3× 10^{40}{ erg s^{-1} } embedded in a 1 keV thermal minicorona which has a half-light radius of about 1.3 kpc, typical of many early-type galaxies in rich clusters of galaxies. If Bondi accretion operated on to the UMBH from the minicorona with a radiative efficiency of 10 per cent, then the object would appear as a quasar with luminosity 10^{46}{ erg s^{-1} }, a factor of almost 106 times higher than observed. The accretion flow must be highly radiatively inefficient, similar to past results on M87 and NGC 3115. The UMBH in NGC 1277 is definitely not undergoing any significant growth at the present epoch. We note that there are three UMBH candidates in the Perseus cluster and that the inferred present mean mass density in UMBHs could be 10^5{ M_{{⊙}}} Mpc^{-3}, which is 20-30 per cent of the estimated mean mass density of all BHs. We speculate on the implied growth of UMBHs and their hosts, and discuss the possibility that extreme active galactic nucleus feedback could make all UMBH host galaxies have low stellar masses at redshifts around 3. Only those which end up at the centres of groups and clusters later accrete large stellar envelopes and become brightest cluster galaxies. NGC 1277 and the other Perseus core UMBH, NGC 1270, have not, however, been able to gather more stars or gas owing to their rapid orbital motion in the cluster core.
    Monthly Notices of the Royal Astronomical Society 04/2013; 431(1):L38-L42. DOI:10.1093/mnrasl/slt004 · 5.23 Impact Factor
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    ABSTRACT: In this third paper in a series on the nature of extended, asymmetric Lyman alpha emitters at z ~ 3 we report the discovery, in an ultra-deep, blind, spectroscopic long-slit survey, of a Lyman alpha emitting halo around a QSO at redshift 3.045. The QSO is a previously known, obscured AGN. The halo appears extended along the direction of the slit and exhibits two faint patches separated by 17 proper kpc in projection from the QSO. Comparison of the 2-dimensional spectrum with archival HST ACS images shows that these patches coincide spatially with emission from a peculiar, dumbbell-shaped, faint galaxy. The assumptions that the Lyman alpha emission patches are originating in the galaxy and that the galaxy is physically related to the QSO are at variance with photometric estimates of the galaxy redshift. We show, however, that a population of very young stars at the redshift of the QSO may fit the existing rest frame broad band UV photometry of the galaxy. If this scenario is correct then the symmetry of the galaxy in continuum and Lyman alpha emission, the extension of the QSO's Lyman alpha emission in its direction, and the likely presence of a young stellar population in close proximity to a (short-lived) AGN suggest that this may be an example of AGN feedback triggering external star formation in high redshift galaxies.
    Monthly Notices of the Royal Astronomical Society 02/2013; 431(1). DOI:10.1093/mnrasl/slt010 · 5.23 Impact Factor

Publication Stats

6k Citations
558.50 Total Impact Points

Institutions

  • 1993–2015
    • University of Cambridge
      • Institute of Astronomy
      Cambridge, England, United Kingdom
  • 2012
    • The Astronomical Observatory of Brera
      Merate, Lombardy, Italy
  • 2004–2010
    • Cancer Research UK Cambridge Institute
      Cambridge, England, United Kingdom
  • 2002–2006
    • Imperial College London
      Londinium, England, United Kingdom
  • 2005
    • Cambridge Healthtech Institute
      Needham, Massachusetts, United States
  • 1995–2002
    • Max Planck Institute for Astrophysics
      Arching, Bavaria, Germany
  • 1999
    • University of Illinois, Urbana-Champaign
      Urbana, Illinois, United States