@article{17733, abstract = {We use three-dimensional hydrodynamic simulations to investigate the effects of a transient photoionizing ultraviolet (UV) flux on the collapse and cooling of pregalactic clouds. These clouds have masses in the range 10^5 -10^7 M_sun, form at high redshifts (z>18), are assumed to lie within the short-lived cosmological HII regions around the first generation of stars. In addition, we study the combined effects of this transient UV flux and a persistent Lyman-Werner (LW) background from distant sources. In the absence of a LW background, we find that a critical specific intensity of J_UV ~ 0.1 x 10^-21 ergs s^-1 cm^-2 Hz^-1 sr^-1 demarcates a transition from net negative to positive feedback for the halo population. A weaker UV flux stimulates subsequent star formation inside the fossil HII regions, by enhancing the H_2 molecule abundance. A stronger UV flux significantly delays star-formation by reducing the gas density, and increasing the cooling time, at the centers of collapsing halos. At a fixed J_UV, the sign of the feedback also depends strongly on the density of the gas at the time of UV illumination. Regardless of the whether the feedback is positive or negative, we find that once the UV flux is turned off, its impact stars to diminish after ~30% of the Hubble time. In the more realistic case when a LW background is present, with J_LW > 0.01 x 10^-21 ergs s^-1 cm^-2 Hz^-1 sr^-1, strong suppression persists down to the lowest redshift (z=18) in our simulations. Finally, we find evidence that heating and photoevaporation by the transient UV flux renders the ~10^6 M_sun halos inside fossil HII regions more vulnerable to subsequent H_2 photo-dissociation by a LW background.}, author = {Mesinger, Andrei and Bryan, Greg L. and Haiman, Zoltán}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {2}, pages = {835--851}, publisher = {American Astronomical Society}, title = {{Ultraviolet radiative feedback on high‐redshift protogalaxies}}, doi = {10.1086/506173}, volume = {648}, year = {2006}, } @article{17742, abstract = {The primordial gas in the earliest dark matter halos, collapsing at redshifts around z=20, with masses M_halo=10^6 M_sun, and virial temperatures T_vir<10^4K, relied on the presence of molecules for cooling. Several theoretical studies have suggested that gas contraction and star-formation in these minihalos was suppressed by radiative, chemical, thermal, and dynamical feedback processes. The recent measurement by the Wilkinson Microwave Anisotropy Probe (WMAP) of the optical depth to electron scattering, tau=0.09+/-0.03, provides the first empirical evidence for this suppression. The new WMAP result is consistent with vanilla models of reionization, in which ionizing sources populate cold dark matter (CDM) halos down to a virial temperature of T_vir=10^4K. On the other hand, we show that in order to avoid overproducing the optical depth, the efficiency for the production of ionizing photons in minihalos must have been about an order of magnitude lower than expected and lower than the efficiency in large halos that can cool via atomic hydrogen (T_vir > 10^4K). This conclusion is insensitive to assumptions about the efficiency of ionizing photon production in the large halos, as long as reionization ends by z=6, as required by the spectra of bright quasars at z<6. Our conclusion is strengthened if the clumping of the ionized gas evolves with redshift, as suggested by semi-analytical predictions and three-dimensional numerical simulations.}, author = {Haiman, Zoltán and Bryan, Greg L.}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {1}, pages = {7--11}, publisher = {American Astronomical Society}, title = {{Was star formation suppressed in high‐redshift minihalos?}}, doi = {10.1086/506580}, volume = {650}, year = {2006}, } @article{17744, abstract = {We present Monte Carlo calculations of Lyman alpha (Lya) radiative transfer through collapsing gas clouds, representing proto-galaxies that are caught in the process of their assembly. Such galaxies produce Lya flux over an extended solid angle from a spatially extended Lya emissivity and/or from scattering effects. We study the effect of the gas distribution and kinematics, and of the Lya emissivity profile, on the emergent spectrum and surface brightness distribution. The emergent Lya spectrum is typically double-peaked and asymmetric. In practice, the blue peak is significantly enhanced and the red peak, in most cases, will be undetectable. The resulting effective blueshift, combined with scattering in the intergalactic medium, will render extended Lya emission from collapsing protogalaxies difficult to detect beyond redshift z=4. The surface brightness distribution is typically flat, and a strong wavelength dependence of its slope (with preferential flattening at the red side of the line) would be a robust indication that Lya photons are being generated (rather than just scattered) in a spatially extended region around the galaxy. We also find that for self-ionized clouds whose effective Lya optical depth is less than 10^3, infall and outflow models can produce nearly identical spectra and surface brightness distributions, and are difficult to distinguish from one another. The presence of deuterium with a cosmic abundance may produce a narrow but detectable dip in the spectra of systems with moderate hydrogen column densities, in the range 10^18-10^20 cm^-2. Finally, we present a new analytic solution for the emerging Lya spectrum in the limiting case of a static uniform sphere, extending previous solutions for static plane-parallel slabs.}, author = {Dijkstra, Mark and Haiman, Zoltán and Spaans, Marco}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {1}, pages = {14--36}, publisher = {American Astronomical Society}, title = {{Lyα radiation from collapsing protogalaxies. I. Characteristics of the emergent spectrum}}, doi = {10.1086/506243}, volume = {649}, year = {2006}, } @article{17766, abstract = {It has been shown that in an idealized galaxy cluster survey, containing ≳10,000 clusters, statistical errors on dark energy and other cosmological parameters would be at the percent level. Furthermore, through ``self-calibration,'' parameters describing the mass-observable relation and cosmology could be simultaneously determined, although at a loss in accuracy by about an order of magnitude. Here we examine an alternative approach to self-calibration, in which a parameterized ab initio physical model is used to compute theoretical mass-observable relations from the cluster structure. As an example, we use a modified-entropy (``preheating'') model of the intracluster medium, with the history and magnitude of entropy injection as unknown input parameters. Using a Fisher matrix approach, we evaluate the expected simultaneous statistical errors on cosmological and cluster model parameters. We find that compared to a phenomenological parameterization of the mass-observable relation, our physical model yields significantly tighter constraints in both surveys and offers substantially improved synergy when the two surveys are combined. In a mock X-ray survey, we find statistical errors on the dark energy equation of state are a factor of 2 tighter than the phenomenological model, with Δw0 ~ 0.08 and its evolution, Δwa ≡ -Δdw/da ~ 0.23, with corresponding errors of Δw0 ~ 0.06 and Δwa ~ 0.17 from a mock Sunyaev-Zel'dovich (SZ) survey, both with Ncl ~ 2.2 × 104 clusters, while simultaneously constraining cluster model parameters to ≲10%. When the two surveys are combined, the constraints tighten to Δw0 ~ 0.03 and Δwa ~ 0.1, a 40% improvement over adding the individual experiment errors in quadrature and a factor of 2 improvement over the phenomenological model. This suggests that parameterized physical models of cluster structure would be useful when extracting cosmological constraints from SZ and X-ray cluster surveys.}, author = {Younger, Joshua D. and Haiman, Zoltán and Bryan, Greg L. and Wang, Sheng}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {1}, pages = {27--42}, publisher = {American Astronomical Society}, title = {{Breaking cosmological degeneracies in galaxy cluster surveys with a physical model of cluster structure}}, doi = {10.1086/508646}, volume = {653}, year = {2006}, } @article{17776, abstract = {The gravitational waves (GW) emitted during the coalescence of supermassive black holes (SMBHs) in the mass range 10^4-10^7 M_sun will be detectable out to high redshifts with LISA. We calculate the size and orientation of the three-dimensional error ellipse in solid angle and redshift within which the LISA event could be localized using the GW signatures alone. We take into account uncertainties in LISA's measurements of the luminosity distance and direction to the source, in the background cosmology, in weak gravitational lensing magnification due to inhomogeneities along the line of sight, and potential source peculiar velocities. We find that weak lensing errors exceed other sources of uncertainties by nearly an order of magnitude. Under the plausible assumption that BH mergers are accompanied by gas accretion leading to Eddington-limited quasar activity, we then compute the number of quasars that would be found in a typical LISA error volume, as a function of BH mass and redshift. We find that low redshifts offer the best opportunities to identify quasar counterparts to cosmological standard sirens, and that the LISA error volume will typically contain a single near-Eddington quasar at z=1. This will allow a straightforward test of the hypothesis that BH mergers are accompanied by bright quasar activity and, if the hypothesis proves correct, will guarantee the identification of a unique quasar counterpart. This would yield unprecedented tests of the physics of SMBH accretion, and offer an alternative method to precisely constrain cosmological parameters.}, author = {Kocsis, Bence and Frei, Zsolt and Haiman, Zoltán and Menou, Kristen}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {1}, pages = {27--37}, publisher = {American Astronomical Society}, title = {{Finding the electromagnetic counterparts of cosmological standard sirens}}, doi = {10.1086/498236}, volume = {637}, year = {2006}, } @article{17794, abstract = {We model the number of detectable supernovae (SNe) as a function of redshift at different flux thresholds, making use of the observed properties of local SNe, such as their light curves, fiducial spectra, and peak magnitude distributions. We assume that the star formation rate (SFR) at high redshift traces the formation rate of dark matter halos. We obtain a rate of 0.4-2.3 SNe arcmin^-2 yr^-1 at z ≳ 5 at the near-infrared (4.5 μm) flux density threshold of 3 nJy (achievable with the James Webb Space Telescope [JWST] in a 10^5 s integration). In a hypothetical 1 yr survey, it should be possible to detect up to several thousand SNe per unit redshift at z ~ 6. We discuss the possible application of such a large sample of distant SNe as a probe of the epoch of reionization. By heating the intergalactic medium (IGM) and raising the cosmological Jeans mass, the process of reionization can suppress star formation in low-mass galaxies. This could have produced a relatively sharp drop in the SN rate around the redshift of reionization (zre). We quantify the detectability of this feature in future surveys of distant SNe by varying the redshift and duration of reionization, as well as its impact on the SFR in low-mass halos, which results in different redshifts, widths, and sizes of the drop in the expected SFR. We find that the drop can be detected out to zre ~ 13, as long as (1) the reionization history contains a relatively rapid feature that is synchronized over different regions to within Δz ≲ 1-3, (2) the star formation efficiency in halos that dominate reionization is epsilon* ~ 10%, and (3) reionization significantly suppresses the star formation in low-mass halos. Depending on the details of (1)-(3), this could be achieved with a survey lasting less than 2 weeks. Detecting this signature would also help elucidate the feedback mechanism that regulates reionization.}, author = {Mesinger, Andrei and Johnson, Benjamin D. and Haiman, Zoltán}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {1}, pages = {80--90}, publisher = {American Astronomical Society}, title = {{The redshift distribution of distant supernovae and its use in probing reionization}}, doi = {10.1086/498294}, volume = {637}, year = {2006}, } @article{18727, abstract = {Gravitational lensing can amplify the apparent brightness of distant sources. Images that are highly magnified are often part of multiply imaged systems, but we consider the possibility of having large magnifications without additional detectable images. In rare but nonnegligible situations, lensing can produce a single highly magnified image; this phenomenon is mainly associated with massive cluster-scale halos (≳1013.5 M☉). Alternatively, lensing can produce multiply imaged systems in which the extra images are either unresolved or too faint to be detectable. This phenomenon is dominated by galaxies and lower mass halos (≲1012 M☉) and is very sensitive to the inner density profile of the halos. Although we study the general problem, we customize our calculations to four quasars at redshift z ≈ 6 in the Sloan Digital Sky Survey (SDSS), for which Richards et al. (2004) have ruled out the presence of extra images down to an image splitting of Δθ = 0farcs3 and a flux ratio of f = 0.01. We predict that 9%-29% of all z ≈ 6 quasars that are magnified by a factor of μ > 10 would lack detectable extra images, with 5%-10% being true singly imaged systems. The maximum of 29% is reached only in the unlikely event that all low-mass (≲1010 M☉) halos have highly concentrated (isothermal) profiles. In more realistic models in which dwarf halos have flatter (Navarro-Frenk-White) inner profiles, the maximum probability is ~10%. We conclude that the probability that all four SDSS quasars are magnified by a factor of 10 is ≲10-4. The only escape from this conclusion is if there are many (>10) multiply imaged z ≈ 6 quasars in the SDSS database that have not yet been identified, which seems unlikely. In other words, lensing cannot explain the brightnesses of the z ≈ 6 quasars, and models that invoke lensing to avoid having billion-solar-mass black holes in the young universe are not viable.}, author = {Keeton, Charles R. and Kuhlen, Michael and Haiman, Zoltán}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {2}, pages = {559--573}, publisher = {American Astronomical Society}, title = {{Gravitational lensing magnification without multiple imaging}}, doi = {10.1086/427722}, volume = {621}, year = {2005}, } @article{18738, abstract = {Gravitational lensing can amplify the apparent brightness of distant sources. Images that are highly magnified are often part of multiply imaged systems, but we consider the possibility of having large magnifications without additional detectable images. In rare but nonnegligible situations, lensing can produce a single highly magnified image; this phenomenon is mainly associated with massive cluster-scale halos (≳1013.5 M☉). Alternatively, lensing can produce multiply imaged systems in which the extra images are either unresolved or too faint to be detectable. This phenomenon is dominated by galaxies and lower mass halos (≲1012 M☉) and is very sensitive to the inner density profile of the halos. Although we study the general problem, we customize our calculations to four quasars at redshift z ≈ 6 in the Sloan Digital Sky Survey (SDSS), for which Richards et al. (2004) have ruled out the presence of extra images down to an image splitting of Δθ = 0farcs3 and a flux ratio of f = 0.01. We predict that 9%-29% of all z ≈ 6 quasars that are magnified by a factor of μ > 10 would lack detectable extra images, with 5%-10% being true singly imaged systems. The maximum of 29% is reached only in the unlikely event that all low-mass (≲1010 M☉) halos have highly concentrated (isothermal) profiles. In more realistic models in which dwarf halos have flatter (Navarro-Frenk-White) inner profiles, the maximum probability is ~10%. We conclude that the probability that all four SDSS quasars are magnified by a factor of 10 is ≲10-4. The only escape from this conclusion is if there are many (>10) multiply imaged z ≈ 6 quasars in the SDSS database that have not yet been identified, which seems unlikely. In other words, lensing cannot explain the brightnesses of the z ≈ 6 quasars, and models that invoke lensing to avoid having billion-solar-mass black holes in the young universe are not viable.}, author = {Keeton, Charles R. and Kuhlen, Michael and Haiman, Zoltán}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {2}, pages = {559--573}, publisher = {American Astronomical Society}, title = {{Gravitational lensing magnification without multiple imaging}}, doi = {10.1086/427722}, volume = {621}, year = {2005}, } @article{17715, abstract = {At redshifts beyond z>6, as the mean fraction of neutral hydrogen x_HI in the intergalactic medium (IGM) increases, the line flux of Lyman alpha (Lya) emitters can be significantly suppressed, which can result in a decrease in the observed number of emitters at a given Lya flux. However, cosmological HII regions surrounding the Lya emitting galaxies alleviate these effects. We use simple models of the Lya line suppression that incorporate the presence of HII regions to predict the overall effect of the Lya absorption on the Lya luminosity function. We find, in agreement with other recent studies, that unless ionizing sources are unusually strongly clustered, a fully neutral IGM may be inconsistent with the large abundance of confirmed z=6.5 Lya emitters. However, the presence of local HII regions prohibits placing a tight constraint on the mean neutral fraction. We find x_HI < 0.25; the presence of strong winds and/or the clustering of ionizing sources would further weaken this constraint. We conclude that the evolution of the Lya LF is consistent with reionization occurring near this redshift. Finally, we suggest that a measurement of observed Lya line width as a function of the Lya luminosity, in a future, larger sample of Lya emitters, may serve as a robust diagnostic of the neutral fraction in the IGM.}, author = {Haiman, Zoltán and Cen, Renyue}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {2}, pages = {627--631}, publisher = {American Astronomical Society}, title = {{Constraining reionization with the evolution of the luminosity function of Lyα emitting galaxies}}, doi = {10.1086/428645}, volume = {623}, year = {2005}, } @article{17720, abstract = {We revisit the possibility of detecting an extrasolar planet around a background star as it crosses the fold caustic of a foreground binary lens. During such an event, the planet's flux can be magnified by a factor of ~100 or more. The detectability of the planet depends strongly on the orientation of its orbit relative to the caustic. If the source star is inside the intercaustic region, detecting the caustic-crossing planet is difficult against the magnified flux of its parent star. In the more favorable configuration, when the star is outside the intercaustic region when the planet crosses the caustic, a close-in Jupiter-like planet around a Sun-like star at a distance of 8 kpc is detectable in 8 minute integrations with a 10 m telescope at maximal signal-to-noise ratio (S/N) ~15 for phase angle ϕ ~ 10°. In this example, we find further that the presence of methane, at its measured abundance in Jupiter, and/or water, sodium, and potassium, at the abundances expected in theoretical atmosphere models of close-in Jupiters, could be inferred from a nondetection of the planet in strong broad absorption bands at 0.6-1.4 μm caused by these compounds, accompanied by a S/N ~ 10 detection in adjacent bands. We conclude that future generations of large telescopes might be able to probe the composition of the atmospheres of distant extrasolar planets.}, author = {Spiegel, David S. and Zamojski, Michel and Gersch, Alan and Donovan, Jennifer and Haiman, Zoltán}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {1}, pages = {478--486}, publisher = {American Astronomical Society}, title = {{Can we probe the atmospheric composition of an extrasolar planet from its reflection spectrum in a high‐magnification microlensing event?}}, doi = {10.1086/430696}, volume = {628}, year = {2005}, } @article{17731, abstract = {In cosmological structure formation models, massive non-linear objects in the process of formation, such as galaxy clusters, are surrounded by large-scale shocks at or around the expected virial radius. Direct observational evidence for such virial shocks is currently lacking, but we show here that their presence can be inferred from future, high resolution, high-sensitivity observations of the Sunyaev-Zel'dovich (SZ) effect in galaxy clusters. We study the detectability of virial shocks in mock SZ maps, using simple models of cluster structure (gas density and temperature distributions) and noise (background and foreground galaxy clusters projected along the line of sight, as well as the cosmic microwave background anisotropies). We find that at an angular resolution of 2'' and sensitivity of 10 micro K, expected to be reached at ~ 100 GHz frequencies in a ~ 20 hr integration with the forthcoming ALMA instrument, virial shocks associated with massive M ~ 10^15 M_Sun clusters will stand out from the noise, and can be detected at high significance. More generally, our results imply that the projected SZ surface brightness profile in future, high-resolution experiments will provide sensitive constraints on the density profile of cluster gas.}, author = {Kocsis, Bence and Haiman, Zoltán and Frei, Zsolt}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {2}, pages = {632--649}, publisher = {American Astronomical Society}, title = {{Can virialization shocks be detected around galaxy clusters through the Sunyaev‐Zel’dovich effect?}}, doi = {10.1086/427975}, volume = {623}, year = {2005}, } @article{17737, abstract = {Cosmological models that include suppression of the power spectrum of density fluctuations on small scales exhibit an exponential reduction of high-redshift, non-linear structures, including a reduction in the rate of gamma ray bursts (GRBs). Here we quantify the constraints that the detection of distant GRBs would place on structure formation models with reduced small-scale power. We compute the number of GRBs that could be detectable by the Swift satellite at high redshifts (z > 6), assuming that the GRBs trace the cosmic star formation history, which itself traces the formation of non-linear structures. We calibrate simple models of the intrinsic luminosity function of the bursts to the number and flux distribution of GRBs observed by the Burst And Transient Source Experiment (BATSE). We find that a discovery of high-z GRBs would imply strong constraints on models with reduced small-scale power. For example, a single GRB at z > 10, or 10 GRBs at z > 5, discovered by Swift during its scheduled two-year mission, would rule out an exponential suppression of the power spectrum on scales below R_c=0.09 Mpc (exemplified by warm dark matter models with a particle mass of m_x=2 keV). Models with a less sharp suppression of small-scale power, such as those with a red tilt or a running scalar index, n_s, are more difficult to constrain, because they are more degenerate with an increase in the power spectrum normalization, sigma_8, and with models in which star-formation is allowed in low-mass minihalos. We find that a tilt of \delta n_s ~ 0.1 is difficult to detect; however, an observed rate of 1 GRB/yr at z > 12 would yield an upper limit on the running of the spectral index, alpha = d(n_s)/d(ln k) > -0.05.}, author = {Mesinger, Andrei and Perna, Rosalba and Haiman, Zoltán}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {1}, pages = {1--10}, publisher = {American Astronomical Society}, title = {{Constraints on the small‐scale power spectrum of density fluctuations from high‐redshift gamma‐ray bursts}}, doi = {10.1086/428770}, volume = {623}, year = {2005}, } @article{17761, abstract = {We explore the possibility of resolving an image of a damped Lyα (DLA) system in absorption against an extended, diffuse, background X-ray source. Typical columns of neutral hydrogen in DLA systems are high enough to block out up to ~30% of the soft X-ray flux at an observed photon energy of 0.5 keV, and we find that ~1% of the area of extended X-ray sources at z ≳ 1 have their 0.5 keV flux reduced by at least 20% because of intervening DLA systems. We discuss the observability of such absorption and find that ≳300 photons per angular resolution element are required in the 0.3-8 keV band for its detection and in order to distinguish it from intrinsic surface brightness fluctuations. For the surface brightness of the currently known high-redshift extended X-ray sources, this requires an integration time of a few megaseconds on Chandra, if the maps are smoothed spatially to ≈2'' resolution. The exact required integration time depends on the DLA system's column density, metallicity, and, most strongly, its redshift. Current X-ray telescopes are likely to detect DLA systems with N < 10^22 cm^-2 only out to z ≈ 2.3. The availability of DLA systems with a suitably high column density for a silhouette detection is currently poorly known. We suggest that at low redshifts archival data of bright X-ray point sources may be useful in constraining the high-N end of the column density distribution. We briefly discuss an alternative strategy of searching for extended X-ray sources behind known DLA systems. Although with current X-ray telescopes the detections are challenging, they will be within the reach of a routine observation with a next generation X-ray telescope, such as the X-Ray Evolving Universe Spectrometer (XEUS) or Generation-X, and will deliver novel constraints on the nature of protogalaxies.}, author = {Dijkstra, Mark and Haiman, Zoltán and Scharf, Caleb}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {1}, pages = {85--93}, publisher = {American Astronomical Society}, title = {{On detecting the X‐ray silhouette of a damped Lyα system}}, doi = {10.1086/428766}, volume = {624}, year = {2005}, } @article{17774, abstract = {We present grism spectra taken with the Advanced Camera for Surveys (ACS) to identify 29 red sources with (i775 - z850) ≥ 0.9 in the Hubble Ultra Deep Field (HUDF). Of these, 23 are found to be galaxies at redshifts between z = 5.4 and 6.7, identified by the break at 1216 Å due to intergalactic medium (IGM) absorption; two are late-type dwarf stars with red colors; and four are galaxies with colors and spectral shapes similar to dust-reddened or old galaxies at redshifts z ≈ 1-2. This constitutes the largest uniform, flux-limited sample of spectroscopically confirmed galaxies at such faint fluxes (z850 ≤ 27.5). Many are also among the most distant spectroscopically confirmed galaxies (at redshifts up to z = 6.7). We find a significant overdensity of galaxies at redshifts z = 5.9 ± 0.2. Nearly two-thirds of the galaxies in our sample (15/23) belong to this peak. Taking into account the selection function and the redshift sensitivity of the survey, we get a conservative overdensity of at least a factor of 2 along the line of sight. The galaxies found in this redshift peak are also localized in the plane of the sky in a nonrandom manner, occupying about half of the ACS chip. Thus the volume overdensity is a factor of 4. The star formation rate derived from detected sources in this overdense region is sufficient to reionize the local IGM.}, author = {Malhotra, S. and Rhoads, J. E. and Pirzkal, N. and Haiman, Zoltán and Xu, C. and Daddi, E. and Yan, H. and Bergeron, L. E. and Wang, J. and Ferguson, H. C. and Gronwall, C. and Koekemoer, A. and Kuemmel, M. and Moustakas, L. A. and Panagia, N. and Pasquali, A. and Stiavelli, M. and Walsh, J. and Windhorst, R. A. and di Serego Alighieri, S.}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {2}, pages = {666--679}, publisher = {American Astronomical Society}, title = {{An overdensity of galaxies at z= 5.9 ± 0.2 in the Hubble Ultra Deep Field confirmed using the ACS grism}}, doi = {10.1086/430047}, volume = {626}, year = {2005}, } @article{17781, abstract = {We have discovered an extended Lyα plume (UDF 5225) associated with a compact source at redshift z ≈ 5.4 in slitless spectroscopic data from the Grism ACS Program for Extragalactic Science (GRAPES) project. The spatial extent of the emission is about 6 × 1.5 kpc (1'' × 0farcs25). Combining our grism data and the broadband images from the Hubble Ultra Deep Field (UDF) images, we find a Lyα line flux of ~2.2 × 10^-17 ergs cm^-2 s^-1 and surface brightness ~7 × 10^-17ergs cm^-2 s-1 arcsec^-2. The UDF images show diffuse continuum emission associated with UDF 5225, including three embedded knots. The morphology of UDF 5225 is highly suggestive of a galaxy in assembly. It is possible that the prominent Lyα emission from this object is due to an active nucleus, and that we are seeing the simultaneous growth through accretion of a galaxy and its central black hole. Follow-up observations at higher spectral resolution could test this hypothesis.}, author = {Rhoads, James E. and Panagia, Nino and Windhorst, Rogier A. and Malhotra, Sangeeta and Pirzkal, Norbert and Xu, Chun and Strolger, Louis Gregory and Bergeron, Louis E. and Daddi, Emanuele and Ferguson, Harry and Gardner, Jonathan P. and Gronwall, Caryl and Haiman, Zoltán and Koekemoer, Anton and Kummel, Martin and Moustakas, Leonidas A. and Pasquali, Anna and Riess, Adam and di Serego Alighieri, Sperello and Stiavelli, Massimo and Tsvetanov, Zlatan and Vernet, Joel and Walsh, Jeremy and Yan, Haojing}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {2}, pages = {582--586}, publisher = {American Astronomical Society}, title = {{A redshift z≈ 5.4 Lyα emitting galaxy with linear morphology in the GRAPES/Hubble Ultra Deep Field}}, doi = {10.1086/427622}, volume = {621}, year = {2005}, } @article{17811, abstract = {The z = 10 galaxy recently discovered by Pello and coworkers has a strong Lyα emission line that does not appear to have the expected asymmetry with more transmission on the red side. The blue wing of a Lyα line originating at high redshift should be strongly suppressed by resonant hydrogen absorption along the line of sight, an expectation borne out by the observed asymmetric shapes of the existing sample of Lyα-emitting sources at lower redshifts (3 < z < 6.7). The observed line is inconsistent with the galaxy being embedded in a fully neutral intergalactic medium (IGM) and having no receding peculiar velocity relative to the surrounding absorbing gas at the 95.0%-98.8% confidence level. Absorption on the blue side of the line of the Pello et al. source could be reduced if the IGM in the vicinity of the galaxy is highly ionized, but we show that this requires an unrealistically high ionizing emissivity. We suggest instead that the Lyα-emitting gas is receding relative to the surrounding gas with a velocity of ≳35 km s-1, which reduces the inconsistency confidence level to less than 76.0%-94.5%. We find that with this velocity shift, the observed strength and shape of the line is more consistent with the galaxy being surrounded by its own Strömgren sphere embedded in a fully neutral IGM. More generally, we predict that at any given redshift, the bright Lyα emitters with broader lines would exhibit stronger asymmetry than fainter ones. Bright galaxies with symmetric Lyα lines may be signposts for groups and clusters of galaxies, within which they can acquire random velocities comparable to or larger than their line widths.}, author = {Cen, Renyue and Haiman, Zoltán and Mesinger, Andrei}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {1}, pages = {89--94}, publisher = {American Astronomical Society}, title = {{Implications of the Lyα Emission Line from a Candidate z = 10 Galaxy}}, doi = {10.1086/425243}, volume = {621}, year = {2005}, } @article{18742, abstract = {Recent improved determinations of the mass density ρBH of supermassive black holes (SMBHs) in the local universe have allowed accurate comparisons of ρBH with the amount of light received from past quasar activity. These comparisons support the notion that local SMBHs are "dead quasars" and yield a value epsilon ≳ 0.1 for the average radiative efficiency of cosmic SMBH accretion. BH coalescences may represent an important component of the quasar mass assembly and yet not produce any observable electromagnetic signature. Therefore, ignoring gravitational wave (GW) emission during such coalescences, which reduces the amount of mass locked into remnant BHs, results in an overestimate of epsilon. Here we put constraints on the magnitude of this bias. We calculate the cumulative mass loss to GWs experienced by a representative population of BHs during repeated cosmological mergers, using loss prescriptions based on detailed general relativistic calculations. Despite the possibly large number of mergers in the assembly history of each individual SMBH, we find that near-equal mass mergers are rare; therefore, the cumulative loss is likely to be modest, amounting at most to a 20% increase in the inferred epsilon value. Thus, recent estimates of epsilon ≳ 0.1 appear robust. The space interferometer LISA should provide empirical constraints on the dark side of quasar evolution by measuring the masses and rates of coalescence of massive BHs to cosmological distances.}, author = {Menou, Kristen and Haiman, Zoltán}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {1}, pages = {130--134}, publisher = {American Astronomical Society}, title = {{On the dark side of quasar evolution}}, doi = {10.1086/423951}, volume = {615}, year = {2004}, } @article{17717, abstract = {We demonstrate that constraints on cosmological parameters from the distribution of clusters as a function of redshift (dN/dz) are complementary to accurate angular diameter distance (D_A) measurements to clusters, and their combination significantly tightens constraints on the energy density content of the Universe. The number counts can be obtained from X-ray and/or SZ (Sunyaev-Zel'dovich effect) surveys, and the angular diameter distances can be determined from deep observations of the intra-cluster gas using their thermal bremsstrahlung X-ray emission and the SZ effect. We combine constraints from simulated cluster number counts expected from a 12 deg^2 SZ cluster survey and constraints from simulated angular diameter distance measurements based on the X-ray/SZ method assuming a statistical accuracy of 10% in the angular diameter distance determination of 100 clusters with redshifts less than 1.5. We find that Omega_m can be determined within about 25%, Omega_Lambda within 20%, and w within 16%. We show that combined dN/dz + D_A constraints can be used to constrain the different energy densities in the Universe even in the presence of a few percent redshift dependent systematic error in D_A. We also address the question of how best to select clusters of galaxies for accurate diameter distance determinations. We show that the joint dN/dz + D_A constraints on cosmological parameters for a fixed target accuracy in the energy density parameters are optimized by selecting clusters with redshift upper cut--offs in the range 0.5 < z < 1.}, author = {Molnar, Sandor M. and Haiman, Zoltán and Birkinshaw, Mark and Mushotzky, Richard F.}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {1}, pages = {22--27}, publisher = {American Astronomical Society}, title = {{Constraints on the energy content of the universe from a combination of galaxy cluster observables}}, doi = {10.1086/380295}, volume = {601}, year = {2004}, } @article{17725, abstract = {A bright quasar residing in a dense and largely neutral intergalactic medium (IGM) at high redshifts (z > 6) will be surrounded by a large cosmological Stromgren sphere. The quasar's spectrum will then show a sharp increase in resonant Lyman line absorption at wavelengths approaching and shorter than that corresponding to the Stromgren sphere's boundary along the line of sight. We show here that simultaneously considering the measured absorption in two or more hydrogen Lyman lines can provide the dynamical range required to detect this feature. We model broad and robust features of the Lyman alpha and Lyman beta regions of the spectrum of the z=6.28 quasar SDSS J1030+0524, using a hydrodynamical simulation. From the steep wavelength-dependence of the inferred absorption opacity, we detect the boundary of the Stromgren sphere at a proper distance of 6.0 +/- 0.2 Mpc away from the source redshift. From the spectrum alone, we also find that beyond this distance, cosmic hydrogen turns nearly neutral, with a neutral fraction of x_HI > 0.2, and that the ionizing luminosity of this quasar is in the range (5.2 +/- 2.5) times 10^{56} photons/sec. The method presented here, when applied to future quasars, can probe the complex topology of overlapping ionized regions, and can be used to study the details of the reionization process.}, author = {Mesinger, Andrei and Haiman, Zoltán}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {2}, pages = {L69--L72}, publisher = {American Astronomical Society}, title = {{Evidence of a cosmological Strömgren surface and of significant neutral hydrogen surrounding the quasar SDSS J1030+0524}}, doi = {10.1086/423935}, volume = {611}, year = {2004}, } @article{17728, abstract = {The cosmic ultraviolet (UV) ionizing background impacts the formation of dwarf galaxies in the low-redshift universe (z=3) by suppressing gas infall into galactic halos with circular velocities up to v(circ)=75 km/s. Using a one-dimensional, spherically symmetric hydrodynamics code (Thoul & Weinberg 1995), we examine the effect of an ionizing background on low-mass galaxies forming at high redshifts (z>10). We find that the importance of photoionization feedback is greatly reduced, because (1) at high redshift, dwarf-galaxy sized objects can self-shield against the ionizing background, (2) collisional cooling processes at high redshift are more efficient, (3) the amplitude of the ionizing background at high redshift is lower, and (4) the ionizing radiation turns on when the perturbation that will become the dwarf galaxy has already grown to a substantial overdensity. We find that because of these reasons, gas can collect inside halos with circular velocities as low as v(circ)=10 km/s. This result has important implications for the reionization history of the universe.}, author = {Dijkstra, Mark and Haiman, Zoltán and Rees, Martin J. and Weinberg, David H.}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {2}, pages = {666--675}, publisher = {American Astronomical Society}, title = {{Photoionization feedback in low‐mass galaxies at high redshift}}, doi = {10.1086/380603}, volume = {601}, year = {2004}, }