The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Joseph F. Hennawi - One of the best experts on this subject based on the ideXlab platform.
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p o niu a ena a luminous z 7 5 quasar hosting a 1 5 billion solar mass black hole
arXiv: Astrophysics of Galaxies, 2020Co-Authors: Jinyi Yang, Joseph F. Hennawi, Xiaohui Fan, Minghao Yue, Feige Wang, Frederick B Davies, Eduardo Banados, B P Venemans, Aaron J Barth, Fuyan BianAbstract:We report the discovery of a luminous quasar, J1007+2115 at $z=7.515$ ("Pōniuā'ena"), from our wide-field reionization-era quasar survey. J1007+2115 is the second quasar now known at $z>7.5$, deep into the reionization epoch. The quasar is powered by a $(1.5\pm0.2)\times10^9$ $M_{\odot}$ supermassive black hole (SMBH), based on its broad MgII emission-line profile from Gemini and Keck near-IR spectroscopy. The SMBH in J1007+2115 is twice as massive as that in quasar J1342+0928 at $z=7.54$, the current quasar redshift record holder. The existence of such a massive SMBH just 700 million years after the Big Bang significantly challenges models of the earliest SMBH growth. Model assumptions of Eddington-limited accretion and a radiative efficiency of 0.1 require a seed black hole of $\gtrsim 10^{4}$ $M_{\odot}$ at $z=30$. This requirement suggests either a massive black hole seed as a result of direct collapse or earlier periods of rapid black hole growth with hyper-Eddington accretion and/or a low radiative efficiency. We measure the damping wing signature imprinted by neutral hydrogen absorption in the intergalactic medium (IGM) on J1007+2115's Ly$\alpha$ line profile, and find that it is weaker than that of J1342+0928 and two other $z\gtrsim7$ quasars. We estimate an IGM volume-averaged neutral fraction $\langle x\rm_{HI}\rangle=0.39^{+0.22}_{-0.13}$. This range of values suggests a patchy reionization history toward different IGM sightlines. We detect the 158 $\mu$m [C II] emission line in J1007+2115 with ALMA; this line centroid yields a systemic redshift of $z=7.5149\pm0.0004$ and indicates a star formation rate of $\sim210$ $M_{\odot}$ yr$^{-1}$ in its host galaxy.
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quantitative constraints on the reionization history from the igm damping wing signature in two quasars at z 7
The Astrophysical Journal, 2018Co-Authors: Frederick B Davies, Joseph F. Hennawi, Xiaohui Fan, Zarija Lukic, Eduardo Banados, Roberto Decarli, Emanuele Paolo Farina, Chiara MazzucchelliAbstract:Author(s): Davies, FB; Hennawi, JF; Banados, E; Lukic, Z; Decarli, R; Fan, X; Farina, EP; Mazzucchelli, C; Rix, HW; Venemans, BP; Walter, F; Wang, F; Yang, J | Abstract: © 2018. The American Astronomical Society. All rights reserved. During reionization, neutral hydrogen in the intergalactic medium (IGM) imprints a damping wing absorption feature on the spectrum of high-redshift quasars. A detection of this signature provides compelling evidence for a significantly neutral universe, and enables measurements of the hydrogen neutral fraction x H i(z) at that epoch. Obtaining reliable quantitative constraints from this technique, however, is challenging due to stochasticity induced by the patchy inside-out topology of reionization, degeneracies with quasar lifetime, and the unknown unabsorbed quasar spectrum close to rest-frame Lyα. We combine a large-volume semi-numerical simulation of reionization topology with 1D radiative transfer through high-resolution hydrodynamical simulations of the high-redshift universe to construct models of quasar transmission spectra during reionization. Our state-of-the-art approach captures the distribution of damping wing strengths in biased quasar halos that should have reionized earlier, as well as the erosion of neutral gas in the quasar environment caused by its own ionizing radiation. Combining this detailed model with our new technique for predicting the quasar continuum and its associated uncertainty, we introduce a Bayesian statistical method to jointly constrain the neutral fraction of the universe and the quasar lifetime from individual quasar spectra. We apply this methodology to the spectra of the two quasars with the highest redshifts known, ULAS J1120+0641 and ULAS J1342+0928, and measure volume-averaged neutral fractions {xH 1}(Z = 7.09) = 0.48+0.26-0.26 and {xH 1}(Z = 7.54) = 0.60+0.20-0.23(posterior medians and 68% credible intervals) when marginalized over quasar lifetimes of 103 ≤ t q ≤ 108 yr.
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modeling the he ii transverse proximity effect constraints on quasar lifetime and obscuration
The Astrophysical Journal, 2018Co-Authors: Joseph F. Hennawi, Tobias M Schmidt, G Worseck, Frederick B Davies, Zarija Lukic, Jose OnorbeAbstract:Author(s): Schmidt, TM; Hennawi, JF; Worseck, G; Davies, FB; Lukic, Z; Onorbe, J | Abstract: © 2018. The American Astronomical Society. All rights reserved.. The He ii transverse proximity effect - enhanced He ii Lyα transmission in a background sightline caused by the ionizing radiation of a foreground quasar - offers a unique opportunity to probe the emission properties of quasars, in particular the emission geometry (obscuration, beaming) and the quasar lifetime. Building on the foreground quasar survey published in Schmidt et al., we present a detailed model of the He ii transverse proximity effect, specifically designed to include light travel time effects, finite quasar ages, and quasar obscuration. We post-process outputs from a cosmological hydrodynamical simulation with a fluctuating He ii ultraviolet background model, with the added effect of the radiation from a single bright foreground quasar. We vary the age t age and obscured sky fractions Ωobsc of the foreground quasar, and explore the resulting effect on the He ii transverse proximity effect signal. Fluctuations in intergalactic medium density and the ultraviolet background, as well as the unknown orientation of the foreground quasar, result in a large variance of the He ii Lyα transmission along the background sightline. We develop a fully Bayesian statistical formalism to compare far-ultraviolet He ii Lyα transmission spectra of the background quasars to our models, and extract joint constraints on t age and Ωobsc for the six Schmidt et al. foreground quasars with the highest implied He ii photoionization rates. Our analysis suggests a bimodal distribution of quasar emission properties, whereby one foreground quasar, associated with a strong He ii transmission spike, is relatively old (22 Myr) and unobscured (), whereas three others are either younger than 10 Myr or highly obscured ().
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Quasars probing quasars X: The quasar pair spectral database
The Astrophysical Journal Supplement Series, 2018Co-Authors: Joseph R. Findlay, Adam D. Myers, J. Xavier Prochaska, Joseph F. Hennawi, Michele Fumagalli, Stephanie Bartle, Ben Chehade, M. A. Dipompeo, Tom Shanks, Marie Wingyee LauAbstract:The rare close projection of two quasars on the sky provides the opportunity to study the host galaxy environment of a foreground quasar in absorption against the continuum emission of a background quasar. For over a decade the "Quasars probing quasars" series has utilized this technique to further the understanding of galaxy formation and evolution in the presence of a quasar at z>2, resolving scales as small as a galactic disc and from bound gas in the circumgalactic medium to the diffuse environs of intergalactic space. Presented here, is the public release of the quasar pair spectral database utilized in these studies. In addition to projected pairs at z>2, the database also includes quasar pair members at z
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quantitative constraints on the reionization history from the igm damping wing signature in two quasars at z 7
arXiv: Cosmology and Nongalactic Astrophysics, 2018Co-Authors: Frederick B Davies, Joseph F. Hennawi, Xiaohui Fan, Zarija Lukic, Eduardo Banados, Roberto Decarli, Emanuele Paolo Farina, Chiara MazzucchelliAbstract:During reionization, neutral hydrogen in the intergalactic medium (IGM) imprints a damping wing absorption feature on the spectrum of high-redshift quasars. A detection of this signature provides compelling evidence for a significantly neutral Universe, and enables measurements of the hydrogen neutral fraction $x_{\rm HI}(z)$ at that epoch. Obtaining reliable quantitative constraints from this technique, however, is challenging due to stochasticity induced by the patchy inside-out topology of reionization, degeneracies with quasar lifetime, and the unknown unabsorbed quasar spectrum close to rest-frame Ly$\alpha$. We combine a large-volume semi-numerical simulation of reionization topology with 1D radiative transfer through high-resolution hydrodynamical simulations of the high-redshift Universe to construct models of quasar transmission spectra during reionization. Our state-of-the-art approach captures the distribution of damping wing strengths in biased quasar halos that should have reionized earlier, as well as the erosion of neutral gas in the quasar environment caused by its own ionizing radiation. Combining this detailed model with our new technique for predicting the quasar continuum and its associated uncertainty, we introduce a Bayesian statistical method to jointly constrain the neutral fraction of the Universe and the quasar lifetime from individual quasar spectra. We apply this methodology to the spectra of the two highest redshift quasars known, ULAS J1120+0641 and ULAS J1342+0928, and measured volume-averaged neutral fractions $\langle x_{\rm HI} \rangle(z=7.09)=0.48^{+0.26}_{-0.26}$ and $\langle x_{\rm HI} \rangle(z=7.54)=0.60^{+0.20}_{-0.23}$ (posterior medians and 68% credible intervals) when marginalized over quasar lifetimes of $10^3 \leq t_{\rm q} \leq 10^8$ years.
Michael E Brown - One of the best experts on this subject based on the ideXlab platform.
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revised for ApJ Letters, January 16, 2004 Ices on the Surface of (50000) Quaoar
2014Co-Authors: Michael E Brown, Chadwick A TrujilloAbstract:The 1.4- 2.4 µm spectrum of the large Kuiper belt object (50000) Quaoar obtained at the Keck observatory shows distinct absorption features of crystalline H2O ice and CH4 and possibly other molecules. CH4 is unexpected on Quaoar because of its high volatility. The CH4 absorption is shifted slightly to shorter wavelengths than is expected for a pure ice, as has been seen on Pluto and Triton where it is attributed to the CH4 being in solution with N2 ice. N2 should not be stable on the surface of Quaoar and its spectral signature is not observed, so we hypothesize that the CH4 is trapped in another ice on the surface where it can survive in spite of its volatility. Additional telescopic and laboratory data are required in order to positively identify all of the features seen in the spectrum of Quaoar
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limits on Quaoar s atmosphere
arXiv: Earth and Planetary Astrophysics, 2013Co-Authors: Wesley C Fraser, Michael E Brown, Chad Trujillo, Andrew W Stephens, German Gimeno, Stephen Gwyn, J J KavelaarsAbstract:Here we present high cadence photometry taken by the Acquisition Camera on Gemini South, of a close passage by the $\sim540$ km radius Kuiper Belt Object, (50000) Quaoar, of a r'=20.2 background star. Observations before and after the event show that the apparent impact parameter of the event was $0.019\pm0.004$", corresponding to a close approach of $580\pm120$ km to the centre of Quaoar. No signatures of occultation by either Quaoar's limb or its potential atmosphere are detectable in the relative photometry of Quaoar and the target star, which were unresolved during closest approach. From this photometry we are able to put constraints on any potential atmosphere Quaoar might have. Using a Markov chain Monte Carlo and likelihood approach, we place pressure upper limits on sublimation supported, isothermal atmospheres of pure N$_2$, CO, and CH$_4$. For N$_2$ and CO, the upper limit surface pressures are 1 and 0.7 $\mu{bar}$ respectively. The surface temperature required for such low sublimation pressures is $\sim33$ K, much lower than Quaoar's mean temperature of $\sim44$ K measured by others. We conclude that Quaoar cannot have an isothermal N$_2$ or CO atmosphere. We cannot eliminate the possibility of a CH$_4$ atmosphere, but place upper surface pressure and mean temperature limits of $\sim138$ nbar and $\sim44$ K respectively.
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the mass orbit and tidal evolution of the Quaoar weywot system
Icarus, 2013Co-Authors: Michael E Brown, Wesley C Fraser, Konstantin Batygin, A H BouchezAbstract:Here we present new adaptive optics observations of the Quaoar–Weywot system. With these new observations we determine an improved system orbit. Due to a 0.39 day alias that exists in available observations, four possible orbital solutions are available with periods of ∼11.6, ∼12.0, ∼12.4, and ∼12.8 days. From the possible orbital solutions, system masses of 1.3–1.5 ± 0.1 × 10^(21) kg are found. These observations provide an updated density for Quaoar of 2.7–5.0 g cm^(−3). In all cases, Weywot’s orbit is eccentric, with possible values ∼0.13–0.16. We present a reanalysis of the tidal orbital evolution of the Quaoar–Weywot system. We have found that Weywot has probably evolved to a state of synchronous rotation, and has likely preserved its initial inclination over the age of the Solar System. We find that for plausible values of the effective tidal dissipation factor tides produce a very slow evolution of Weywot’s eccentricity and semi-major axis. Accordingly, it appears that Weywot’s eccentricity likely did not tidally evolve to its current value from an initially circular orbit. Rather, it seems that some other mechanism has raised its eccentricity post-formation, or Weywot formed with a non-negligible eccentricity.
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Quaoar a rock in the kuiper belt
arXiv: Earth and Planetary Astrophysics, 2010Co-Authors: Wesley C Fraser, Michael E BrownAbstract:Here we report WFPC2 observations of the Quaoar-Weywot Kuiper belt binary. From these observations we find that Weywot is on an elliptical orbit with eccentricity of 0.14 {\pm} 0.04, period of 12.438 {\pm} 0.005 days, and a semi-major axis of 1.45 {\pm} 0.08 {\times} 104 km. The orbit reveals a surpsingly high Quaoar-Weywot system mass of 1.6{\pm}0.3{\times}10^21 kg. Using the surface properties of the Uranian and Neptunian satellites as a proxy for Quaoar's surface, we reanalyze the size estimate from Brown and Trujillo (2004). We find, from a mean of available published size estimates, a diameter for Quaoar of 890 {\pm} 70 km. We find Quaoar's density to be \rho = 4.2 {\pm} 1.3 g cm^-3, possibly the highest density in the Kuiper belt.
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doi:10.1088/0004-637X/714/2/1547 Quaoar: A ROCK IN THE
2010Co-Authors: Kuiper Belt, Wesley C Fraser, Michael E BrownAbstract:Here we report Wide-Field Planetary Camera 2 observations of the Quaoar–Weywot Kuiper Belt binary. From these observations, we find that Weywot is on an elliptical orbit with an eccentricity of 0.14 ± 0.04, a period of 12.438 ± 0.005 days, and a semimajor axis of 1.45 ± 0.08 × 104 km. The orbit reveals a surprisingly high-Quaoar–Weywot system mass of (1.6 ± 0.3) × 1021 kg. Using the surface properties of the Uranian and Neptunian satellites as a proxy for Quaoar’s surface, we reanalyze the size estimate from Brown & Trujillo. We find, from a mean of available published size estimates, a diameter for Quaoar of 890 ± 70 km. We find Quaoar’s density to be ρ = 4.2 ± 1.3 gcm−3, possibly the highest density in the Kuiper Belt
Eduardo Banados - One of the best experts on this subject based on the ideXlab platform.
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resolving the radio emission from the quasar p172 18 at z 6 82
The Astronomical Journal, 2021Co-Authors: Emmanuel Momjian, Eduardo Banados, C L Carilli, Fabian Walter, Chiara MazzucchelliAbstract:We present high angular resolution imaging of the quasar PSO J172.3556+18.7734 at $z=6.82$ with the Very Long Baseline Array (VLBA). This source currently holds the record of being the highest redshift radio-loud quasar. These observations reveal a dominant radio source with a flux density of $398.4 \pm 61.4~\mu$Jy at 1.53 GHz, a deconvolved size of $9.9 \times 3.5$ mas ($52.5 \times 18.6$ pc), and an intrinsic brightness temperature of ($4.7 \pm 0.7) \times 10^7$ K. A weak unresolved radio extension from the main source is also detected at $\sim~3.1\sigma$ level. The total flux density recovered with the VLBA at 1.53 GHz is consistent with that measured with the Very Large Array (VLA) at a similar frequency. The quasar is not detected at 4.67 GHz with the VLBA, suggesting a steep spectral index with a limit of $\alpha^{1.53}_{4.67} < -$1.55. The quasar is also not detected with the VLBA at 7.67 GHz. The overall characteristics of the quasar suggest that it is a very young radio source similar to lower redshift Gigahertz Peaked Spectrum radio sources, with an estimated kinematic age of $\sim~10^3$ years. The VLA observations of this quasar revealed a second radio source in the field $23\rlap{.}{''}1$ away. This radio source, which does not have an optical or IR counterpart, is not detected with the VLBA at any of the observed frequencies. Its non-detection at the lowest observed VLBA frequency suggests that it is resolved out, implying a size larger than ~$0\rlap{.}{''}17$. It is thus likely situated at lower redshift than the quasar.
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x ray observations of a c ii bright z 6 59 quasar companion system
The Astrophysical Journal, 2020Co-Authors: Xiaohui Fan, Eduardo Banados, Roberto Decarli, Emanuele Paolo Farina, Chiara Mazzucchelli, Thomas Connor, Daniel Stern, E LussoAbstract:We present deep Chandra observations of PSO J231.6576$-$20.8335, a quasar at redshift z=6.59 with a nearby (${\sim}8$ proper kpc) companion galaxy. ALMA observed both the quasar and companion to be bright in [C II], and the system has significant extended Ly$\alpha$ emission around the quasar, suggesting that a galaxy merger is ongoing. Unlike previous studies of two similar systems, and despite observing the system with Chandra for 140 ks, we do not detect the companion in X-rays. The quasar itself is detected, but only $13.3^{+4.8}_{-3.7}$ net counts are observed. From a basic spectral analysis, the X-ray spectrum of the quasar is soft (hardness ratio of $\mathcal{HR} = -0.60_{-0.27}^{+0.17}$, power-law index of $\Gamma=2.6^{+1.0}_{-0.9}$), which results in a rest-frame X-ray luminosity comparable to other bright quasars ($L_{2-10} = 1.09^{+2.20}_{-0.70}\times 10^{45}\ \textrm{erg}\ \textrm{s}^{-1}$) despite the faint observed X-ray flux. We highlight two possible interpretations of this result: the quasar has a steep value of $\Gamma$ -- potentially related to observed ongoing Eddington accretion -- thereby pushing much of the emission out of our observed band, or the quasar has a more normal spectrum ($\Gamma{\sim}2$) but is therefore less X-ray luminous ($L_{2-10} \sim 0.6 \times 10^{45}\ \textrm{ erg}\ \textrm{ s}^{-1}$).
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p o niu a ena a luminous z 7 5 quasar hosting a 1 5 billion solar mass black hole
arXiv: Astrophysics of Galaxies, 2020Co-Authors: Jinyi Yang, Joseph F. Hennawi, Xiaohui Fan, Minghao Yue, Feige Wang, Frederick B Davies, Eduardo Banados, B P Venemans, Aaron J Barth, Fuyan BianAbstract:We report the discovery of a luminous quasar, J1007+2115 at $z=7.515$ ("Pōniuā'ena"), from our wide-field reionization-era quasar survey. J1007+2115 is the second quasar now known at $z>7.5$, deep into the reionization epoch. The quasar is powered by a $(1.5\pm0.2)\times10^9$ $M_{\odot}$ supermassive black hole (SMBH), based on its broad MgII emission-line profile from Gemini and Keck near-IR spectroscopy. The SMBH in J1007+2115 is twice as massive as that in quasar J1342+0928 at $z=7.54$, the current quasar redshift record holder. The existence of such a massive SMBH just 700 million years after the Big Bang significantly challenges models of the earliest SMBH growth. Model assumptions of Eddington-limited accretion and a radiative efficiency of 0.1 require a seed black hole of $\gtrsim 10^{4}$ $M_{\odot}$ at $z=30$. This requirement suggests either a massive black hole seed as a result of direct collapse or earlier periods of rapid black hole growth with hyper-Eddington accretion and/or a low radiative efficiency. We measure the damping wing signature imprinted by neutral hydrogen absorption in the intergalactic medium (IGM) on J1007+2115's Ly$\alpha$ line profile, and find that it is weaker than that of J1342+0928 and two other $z\gtrsim7$ quasars. We estimate an IGM volume-averaged neutral fraction $\langle x\rm_{HI}\rangle=0.39^{+0.22}_{-0.13}$. This range of values suggests a patchy reionization history toward different IGM sightlines. We detect the 158 $\mu$m [C II] emission line in J1007+2115 with ALMA; this line centroid yields a systemic redshift of $z=7.5149\pm0.0004$ and indicates a star formation rate of $\sim210$ $M_{\odot}$ yr$^{-1}$ in its host galaxy.
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exploring reionization era quasars iv discovery of six new z gtrsim 6 5 quasars with des vhs and unwise photometry
arXiv: Astrophysics of Galaxies, 2018Co-Authors: Jinyi Yang, Xiaohui Fan, Minghao Yue, Feige Wang, Eduardo Banados, Fuyan Bian, Linhua Jiang, Yuri BeletskyAbstract:This is the fourth paper in a series of publications aiming at discovering quasars at the epoch of reionization. In this paper, we expand our search for $z\sim 7$ quasars to the footprint of the Dark Energy Survey (DES) Data Release One (DR1), covering $\sim 5000$ deg$^2$ of new area. We select $z\sim 7$ quasar candidates using deep optical, near-infrared (near-IR) and mid-IR photometric data from the DES DR1, the VISTA Hemisphere Survey (VHS), the VISTA Kilo-degree Infrared Galaxy (VIKING) survey, the UKIRT InfraRed Deep Sky Surveys -- Large Area Survey (ULAS) and the unblurred coadds from the Wide-field Infrared Survey Explore ($WISE$) images (unWISE). The inclusion of DES and unWISE photometry allows the search to reach $\sim$ 1 magnitude fainter, comparing to our $z \gtrsim 6.5$ quasar survey in the northern sky (Wang et al. 2018). We report the initial discovery and spectroscopic confirmation of six new luminous quasars at $z>6.4$, including an object at $z=7.02$, the fourth quasar yet known at $z>7$, from a small fraction of candidates observed thus far. Based on the recent measurement of $z \sim 6.7 $ quasar luminosity function using the quasar sample from our survey in the northern sky, we estimate that there will be $\gtrsim$ 55 quasars at $z > 6.5$ at $M_{1450} < -24.5$ in the full DES footprint.
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exploring reionization era quasars iii discovery of 16 quasars at 6 4 lesssim z lesssim 6 9 with desi legacy imaging surveys and ukirt hemisphere survey and quasar luminosity function at z sim6 7
arXiv: Astrophysics of Galaxies, 2018Co-Authors: Feige Wang, Xiaohui Fan, Jan Torge Schindler, Minghao Yue, Jinyi Yang, Joseph R. Findlay, Eduardo Banados, Fuyan Bian, Linhua Jiang, Frederick B DaviesAbstract:This is the third paper in a series aims at finding reionzation-era quasars with the combination of DESI Legacy imaging Surveys (DELS) and near-infrared imaging surveys, such as the UKIRT Hemisphere Survey (UHS), as well as the Wide-field Infrared Survey Explore ($WISE$) mid-infrared survey. In this paper, we describe the updated quasar candidate selection procedure, report the discovery of 16 quasars at $6.4\lesssim z \lesssim6.9$ from area of $\sim$13,020 deg$^2$, and present the quasar luminosity function (QLF) at $z\sim6.7$. The measured QLF follows $\Phi(L_{1450})\propto L_{1450}^{-2.35}$ in the magnitude range $27.6
Chiara Mazzucchelli - One of the best experts on this subject based on the ideXlab platform.
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resolving the radio emission from the quasar p172 18 at z 6 82
The Astronomical Journal, 2021Co-Authors: Emmanuel Momjian, Eduardo Banados, C L Carilli, Fabian Walter, Chiara MazzucchelliAbstract:We present high angular resolution imaging of the quasar PSO J172.3556+18.7734 at $z=6.82$ with the Very Long Baseline Array (VLBA). This source currently holds the record of being the highest redshift radio-loud quasar. These observations reveal a dominant radio source with a flux density of $398.4 \pm 61.4~\mu$Jy at 1.53 GHz, a deconvolved size of $9.9 \times 3.5$ mas ($52.5 \times 18.6$ pc), and an intrinsic brightness temperature of ($4.7 \pm 0.7) \times 10^7$ K. A weak unresolved radio extension from the main source is also detected at $\sim~3.1\sigma$ level. The total flux density recovered with the VLBA at 1.53 GHz is consistent with that measured with the Very Large Array (VLA) at a similar frequency. The quasar is not detected at 4.67 GHz with the VLBA, suggesting a steep spectral index with a limit of $\alpha^{1.53}_{4.67} < -$1.55. The quasar is also not detected with the VLBA at 7.67 GHz. The overall characteristics of the quasar suggest that it is a very young radio source similar to lower redshift Gigahertz Peaked Spectrum radio sources, with an estimated kinematic age of $\sim~10^3$ years. The VLA observations of this quasar revealed a second radio source in the field $23\rlap{.}{''}1$ away. This radio source, which does not have an optical or IR counterpart, is not detected with the VLBA at any of the observed frequencies. Its non-detection at the lowest observed VLBA frequency suggests that it is resolved out, implying a size larger than ~$0\rlap{.}{''}17$. It is thus likely situated at lower redshift than the quasar.
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x ray observations of a c ii bright z 6 59 quasar companion system
The Astrophysical Journal, 2020Co-Authors: Xiaohui Fan, Eduardo Banados, Roberto Decarli, Emanuele Paolo Farina, Chiara Mazzucchelli, Thomas Connor, Daniel Stern, E LussoAbstract:We present deep Chandra observations of PSO J231.6576$-$20.8335, a quasar at redshift z=6.59 with a nearby (${\sim}8$ proper kpc) companion galaxy. ALMA observed both the quasar and companion to be bright in [C II], and the system has significant extended Ly$\alpha$ emission around the quasar, suggesting that a galaxy merger is ongoing. Unlike previous studies of two similar systems, and despite observing the system with Chandra for 140 ks, we do not detect the companion in X-rays. The quasar itself is detected, but only $13.3^{+4.8}_{-3.7}$ net counts are observed. From a basic spectral analysis, the X-ray spectrum of the quasar is soft (hardness ratio of $\mathcal{HR} = -0.60_{-0.27}^{+0.17}$, power-law index of $\Gamma=2.6^{+1.0}_{-0.9}$), which results in a rest-frame X-ray luminosity comparable to other bright quasars ($L_{2-10} = 1.09^{+2.20}_{-0.70}\times 10^{45}\ \textrm{erg}\ \textrm{s}^{-1}$) despite the faint observed X-ray flux. We highlight two possible interpretations of this result: the quasar has a steep value of $\Gamma$ -- potentially related to observed ongoing Eddington accretion -- thereby pushing much of the emission out of our observed band, or the quasar has a more normal spectrum ($\Gamma{\sim}2$) but is therefore less X-ray luminous ($L_{2-10} \sim 0.6 \times 10^{45}\ \textrm{ erg}\ \textrm{ s}^{-1}$).
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quantitative constraints on the reionization history from the igm damping wing signature in two quasars at z 7
The Astrophysical Journal, 2018Co-Authors: Frederick B Davies, Joseph F. Hennawi, Xiaohui Fan, Zarija Lukic, Eduardo Banados, Roberto Decarli, Emanuele Paolo Farina, Chiara MazzucchelliAbstract:Author(s): Davies, FB; Hennawi, JF; Banados, E; Lukic, Z; Decarli, R; Fan, X; Farina, EP; Mazzucchelli, C; Rix, HW; Venemans, BP; Walter, F; Wang, F; Yang, J | Abstract: © 2018. The American Astronomical Society. All rights reserved. During reionization, neutral hydrogen in the intergalactic medium (IGM) imprints a damping wing absorption feature on the spectrum of high-redshift quasars. A detection of this signature provides compelling evidence for a significantly neutral universe, and enables measurements of the hydrogen neutral fraction x H i(z) at that epoch. Obtaining reliable quantitative constraints from this technique, however, is challenging due to stochasticity induced by the patchy inside-out topology of reionization, degeneracies with quasar lifetime, and the unknown unabsorbed quasar spectrum close to rest-frame Lyα. We combine a large-volume semi-numerical simulation of reionization topology with 1D radiative transfer through high-resolution hydrodynamical simulations of the high-redshift universe to construct models of quasar transmission spectra during reionization. Our state-of-the-art approach captures the distribution of damping wing strengths in biased quasar halos that should have reionized earlier, as well as the erosion of neutral gas in the quasar environment caused by its own ionizing radiation. Combining this detailed model with our new technique for predicting the quasar continuum and its associated uncertainty, we introduce a Bayesian statistical method to jointly constrain the neutral fraction of the universe and the quasar lifetime from individual quasar spectra. We apply this methodology to the spectra of the two quasars with the highest redshifts known, ULAS J1120+0641 and ULAS J1342+0928, and measure volume-averaged neutral fractions {xH 1}(Z = 7.09) = 0.48+0.26-0.26 and {xH 1}(Z = 7.54) = 0.60+0.20-0.23(posterior medians and 68% credible intervals) when marginalized over quasar lifetimes of 103 ≤ t q ≤ 108 yr.
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dust emission in an accretion rate limited sample of z 6 quasars
arXiv: Astrophysics of Galaxies, 2018Co-Authors: B P Venemans, Xiaohui Fan, Eduardo Banados, Roberto Decarli, Emanuele Paolo Farina, Fabian Walter, F Bertoldi, Chiara MazzucchelliAbstract:We present Atacama Large Millimeter Array 1mm observations of the rest-frame far-infrared (FIR) dust continuum in 27 quasars at redshifts 6.0 3sigma in all quasar host galaxies with flux densities at ~1900GHz in the rest-frame of 0.12 10^12 L_sun. The estimated dust masses are M_dust = 10^7-10^9 M_sun. If the dust is heated only by star formation, then the star formation rates in the quasar host galaxies are between 50 and 2700 M_sun/yr. In the framework of the host galaxy-black hole coevolution model a correlation between ongoing black hole growth and star formation in the quasar host galaxy would be expected. However, combined with results from the literature to create a luminosity-limited quasar sample, we do not find a strong correlation between quasar UV luminosity (a proxy for ongoing black hole growth) and FIR luminosity (star formation in the host galaxy). The absence of such a correlation in our data does not necessarily rule out the coevolution model, and could be due to a variety of effects (including different timescales for black hole accretion and FIR emission).
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quantitative constraints on the reionization history from the igm damping wing signature in two quasars at z 7
arXiv: Cosmology and Nongalactic Astrophysics, 2018Co-Authors: Frederick B Davies, Joseph F. Hennawi, Xiaohui Fan, Zarija Lukic, Eduardo Banados, Roberto Decarli, Emanuele Paolo Farina, Chiara MazzucchelliAbstract:During reionization, neutral hydrogen in the intergalactic medium (IGM) imprints a damping wing absorption feature on the spectrum of high-redshift quasars. A detection of this signature provides compelling evidence for a significantly neutral Universe, and enables measurements of the hydrogen neutral fraction $x_{\rm HI}(z)$ at that epoch. Obtaining reliable quantitative constraints from this technique, however, is challenging due to stochasticity induced by the patchy inside-out topology of reionization, degeneracies with quasar lifetime, and the unknown unabsorbed quasar spectrum close to rest-frame Ly$\alpha$. We combine a large-volume semi-numerical simulation of reionization topology with 1D radiative transfer through high-resolution hydrodynamical simulations of the high-redshift Universe to construct models of quasar transmission spectra during reionization. Our state-of-the-art approach captures the distribution of damping wing strengths in biased quasar halos that should have reionized earlier, as well as the erosion of neutral gas in the quasar environment caused by its own ionizing radiation. Combining this detailed model with our new technique for predicting the quasar continuum and its associated uncertainty, we introduce a Bayesian statistical method to jointly constrain the neutral fraction of the Universe and the quasar lifetime from individual quasar spectra. We apply this methodology to the spectra of the two highest redshift quasars known, ULAS J1120+0641 and ULAS J1342+0928, and measured volume-averaged neutral fractions $\langle x_{\rm HI} \rangle(z=7.09)=0.48^{+0.26}_{-0.26}$ and $\langle x_{\rm HI} \rangle(z=7.54)=0.60^{+0.20}_{-0.23}$ (posterior medians and 68% credible intervals) when marginalized over quasar lifetimes of $10^3 \leq t_{\rm q} \leq 10^8$ years.
Frederick B Davies - One of the best experts on this subject based on the ideXlab platform.
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p o niu a ena a luminous z 7 5 quasar hosting a 1 5 billion solar mass black hole
arXiv: Astrophysics of Galaxies, 2020Co-Authors: Jinyi Yang, Joseph F. Hennawi, Xiaohui Fan, Minghao Yue, Feige Wang, Frederick B Davies, Eduardo Banados, B P Venemans, Aaron J Barth, Fuyan BianAbstract:We report the discovery of a luminous quasar, J1007+2115 at $z=7.515$ ("Pōniuā'ena"), from our wide-field reionization-era quasar survey. J1007+2115 is the second quasar now known at $z>7.5$, deep into the reionization epoch. The quasar is powered by a $(1.5\pm0.2)\times10^9$ $M_{\odot}$ supermassive black hole (SMBH), based on its broad MgII emission-line profile from Gemini and Keck near-IR spectroscopy. The SMBH in J1007+2115 is twice as massive as that in quasar J1342+0928 at $z=7.54$, the current quasar redshift record holder. The existence of such a massive SMBH just 700 million years after the Big Bang significantly challenges models of the earliest SMBH growth. Model assumptions of Eddington-limited accretion and a radiative efficiency of 0.1 require a seed black hole of $\gtrsim 10^{4}$ $M_{\odot}$ at $z=30$. This requirement suggests either a massive black hole seed as a result of direct collapse or earlier periods of rapid black hole growth with hyper-Eddington accretion and/or a low radiative efficiency. We measure the damping wing signature imprinted by neutral hydrogen absorption in the intergalactic medium (IGM) on J1007+2115's Ly$\alpha$ line profile, and find that it is weaker than that of J1342+0928 and two other $z\gtrsim7$ quasars. We estimate an IGM volume-averaged neutral fraction $\langle x\rm_{HI}\rangle=0.39^{+0.22}_{-0.13}$. This range of values suggests a patchy reionization history toward different IGM sightlines. We detect the 158 $\mu$m [C II] emission line in J1007+2115 with ALMA; this line centroid yields a systemic redshift of $z=7.5149\pm0.0004$ and indicates a star formation rate of $\sim210$ $M_{\odot}$ yr$^{-1}$ in its host galaxy.
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exploring reionization era quasars iii discovery of 16 quasars at 6 4 lesssim z lesssim 6 9 with desi legacy imaging surveys and ukirt hemisphere survey and quasar luminosity function at z sim6 7
arXiv: Astrophysics of Galaxies, 2018Co-Authors: Feige Wang, Xiaohui Fan, Jan Torge Schindler, Minghao Yue, Jinyi Yang, Joseph R. Findlay, Eduardo Banados, Fuyan Bian, Linhua Jiang, Frederick B DaviesAbstract:This is the third paper in a series aims at finding reionzation-era quasars with the combination of DESI Legacy imaging Surveys (DELS) and near-infrared imaging surveys, such as the UKIRT Hemisphere Survey (UHS), as well as the Wide-field Infrared Survey Explore ($WISE$) mid-infrared survey. In this paper, we describe the updated quasar candidate selection procedure, report the discovery of 16 quasars at $6.4\lesssim z \lesssim6.9$ from area of $\sim$13,020 deg$^2$, and present the quasar luminosity function (QLF) at $z\sim6.7$. The measured QLF follows $\Phi(L_{1450})\propto L_{1450}^{-2.35}$ in the magnitude range $27.6
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quantitative constraints on the reionization history from the igm damping wing signature in two quasars at z 7
The Astrophysical Journal, 2018Co-Authors: Frederick B Davies, Joseph F. Hennawi, Xiaohui Fan, Zarija Lukic, Eduardo Banados, Roberto Decarli, Emanuele Paolo Farina, Chiara MazzucchelliAbstract:Author(s): Davies, FB; Hennawi, JF; Banados, E; Lukic, Z; Decarli, R; Fan, X; Farina, EP; Mazzucchelli, C; Rix, HW; Venemans, BP; Walter, F; Wang, F; Yang, J | Abstract: © 2018. The American Astronomical Society. All rights reserved. During reionization, neutral hydrogen in the intergalactic medium (IGM) imprints a damping wing absorption feature on the spectrum of high-redshift quasars. A detection of this signature provides compelling evidence for a significantly neutral universe, and enables measurements of the hydrogen neutral fraction x H i(z) at that epoch. Obtaining reliable quantitative constraints from this technique, however, is challenging due to stochasticity induced by the patchy inside-out topology of reionization, degeneracies with quasar lifetime, and the unknown unabsorbed quasar spectrum close to rest-frame Lyα. We combine a large-volume semi-numerical simulation of reionization topology with 1D radiative transfer through high-resolution hydrodynamical simulations of the high-redshift universe to construct models of quasar transmission spectra during reionization. Our state-of-the-art approach captures the distribution of damping wing strengths in biased quasar halos that should have reionized earlier, as well as the erosion of neutral gas in the quasar environment caused by its own ionizing radiation. Combining this detailed model with our new technique for predicting the quasar continuum and its associated uncertainty, we introduce a Bayesian statistical method to jointly constrain the neutral fraction of the universe and the quasar lifetime from individual quasar spectra. We apply this methodology to the spectra of the two quasars with the highest redshifts known, ULAS J1120+0641 and ULAS J1342+0928, and measure volume-averaged neutral fractions {xH 1}(Z = 7.09) = 0.48+0.26-0.26 and {xH 1}(Z = 7.54) = 0.60+0.20-0.23(posterior medians and 68% credible intervals) when marginalized over quasar lifetimes of 103 ≤ t q ≤ 108 yr.
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modeling the he ii transverse proximity effect constraints on quasar lifetime and obscuration
The Astrophysical Journal, 2018Co-Authors: Joseph F. Hennawi, Tobias M Schmidt, G Worseck, Frederick B Davies, Zarija Lukic, Jose OnorbeAbstract:Author(s): Schmidt, TM; Hennawi, JF; Worseck, G; Davies, FB; Lukic, Z; Onorbe, J | Abstract: © 2018. The American Astronomical Society. All rights reserved.. The He ii transverse proximity effect - enhanced He ii Lyα transmission in a background sightline caused by the ionizing radiation of a foreground quasar - offers a unique opportunity to probe the emission properties of quasars, in particular the emission geometry (obscuration, beaming) and the quasar lifetime. Building on the foreground quasar survey published in Schmidt et al., we present a detailed model of the He ii transverse proximity effect, specifically designed to include light travel time effects, finite quasar ages, and quasar obscuration. We post-process outputs from a cosmological hydrodynamical simulation with a fluctuating He ii ultraviolet background model, with the added effect of the radiation from a single bright foreground quasar. We vary the age t age and obscured sky fractions Ωobsc of the foreground quasar, and explore the resulting effect on the He ii transverse proximity effect signal. Fluctuations in intergalactic medium density and the ultraviolet background, as well as the unknown orientation of the foreground quasar, result in a large variance of the He ii Lyα transmission along the background sightline. We develop a fully Bayesian statistical formalism to compare far-ultraviolet He ii Lyα transmission spectra of the background quasars to our models, and extract joint constraints on t age and Ωobsc for the six Schmidt et al. foreground quasars with the highest implied He ii photoionization rates. Our analysis suggests a bimodal distribution of quasar emission properties, whereby one foreground quasar, associated with a strong He ii transmission spike, is relatively old (22 Myr) and unobscured (), whereas three others are either younger than 10 Myr or highly obscured ().
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quantitative constraints on the reionization history from the igm damping wing signature in two quasars at z 7
arXiv: Cosmology and Nongalactic Astrophysics, 2018Co-Authors: Frederick B Davies, Joseph F. Hennawi, Xiaohui Fan, Zarija Lukic, Eduardo Banados, Roberto Decarli, Emanuele Paolo Farina, Chiara MazzucchelliAbstract:During reionization, neutral hydrogen in the intergalactic medium (IGM) imprints a damping wing absorption feature on the spectrum of high-redshift quasars. A detection of this signature provides compelling evidence for a significantly neutral Universe, and enables measurements of the hydrogen neutral fraction $x_{\rm HI}(z)$ at that epoch. Obtaining reliable quantitative constraints from this technique, however, is challenging due to stochasticity induced by the patchy inside-out topology of reionization, degeneracies with quasar lifetime, and the unknown unabsorbed quasar spectrum close to rest-frame Ly$\alpha$. We combine a large-volume semi-numerical simulation of reionization topology with 1D radiative transfer through high-resolution hydrodynamical simulations of the high-redshift Universe to construct models of quasar transmission spectra during reionization. Our state-of-the-art approach captures the distribution of damping wing strengths in biased quasar halos that should have reionized earlier, as well as the erosion of neutral gas in the quasar environment caused by its own ionizing radiation. Combining this detailed model with our new technique for predicting the quasar continuum and its associated uncertainty, we introduce a Bayesian statistical method to jointly constrain the neutral fraction of the Universe and the quasar lifetime from individual quasar spectra. We apply this methodology to the spectra of the two highest redshift quasars known, ULAS J1120+0641 and ULAS J1342+0928, and measured volume-averaged neutral fractions $\langle x_{\rm HI} \rangle(z=7.09)=0.48^{+0.26}_{-0.26}$ and $\langle x_{\rm HI} \rangle(z=7.54)=0.60^{+0.20}_{-0.23}$ (posterior medians and 68% credible intervals) when marginalized over quasar lifetimes of $10^3 \leq t_{\rm q} \leq 10^8$ years.