arXiv subjects

Linhua Jiang

Publications and source records attributed to Linhua Jiang.

At least 91 records · Page 5Linked to original sources

arXiv2021

A Luminous Quasar at Redshift 7.642

Distant quasars are unique tracers to study the formation of the earliest supermassive black holes (SMBHs) and the history of cosmic reionization. Despite extensive efforts, only two quasars have been found at $z\ge7.5$, due to a combination of their low spatial density and the high contamination rate in quasar selection. We report the discovery of a luminous quasar at $z=7.642$, J0313$-$1806, the most distant quasar yet known. This quasar has a bolometric luminosity of $3.6\times10^{13} L_\odot$. Deep spectroscopic observations reveal a SMBH with a mass of $(1.6\pm0.4) \times10^9M_\odot$ in this quasar. The existence of such a massive SMBH just $\sim$670 million years after the Big Bang challenges significantly theoretical models of SMBH growth. In addition, the quasar spectrum exhibits strong broad absorption line (BAL) features in CIV and SiIV, with a maximum velocity close to 20% of the speed of light. The relativistic BAL features, combined with a strongly blueshifted CIV emission line, indicate that there is a strong active galactic nucleus (AGN) driven outflow in this system. ALMA observations detect the dust continuum and [CII] emission from the quasar host galaxy, yielding an accurate redshift of $7.6423 \pm 0.0013$ and suggesting that the quasar is hosted by an intensely star-forming galaxy, with a star formation rate of $\rm\sim 200 ~M_\odot ~yr^{-1}$ and a dust mass of $\sim7\times10^7~M_\odot$. Followup observations of this reionization-era BAL quasar will provide a powerful probe of the effects of AGN feedback on the growth of the earliest massive galaxies.

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arXiv2020

Discovery of a damped Ly$α$ galaxy at z $\sim$ 3 towards the quasar SDSS J011852+040644

We report the detection of the host galaxy of a damped Ly$α$ system (DLA) with log N(HI) $ [\rm cm^{-2}]$ = $21.0 \pm 0.10$ at $z \approx 3.0091$ towards the background quasar SDSS J011852+040644 using the Palomar Cosmic Web Imager (PCWI) at the Hale (P200) telescope. We detect Ly$α$ emission in the dark core of the DLA trough at a 3.3$σ$ confidence level, with Ly$α$ luminosity of $L_{\rm Lyα}$ $\rm = (3.8 \pm 0.8) \times 10^{42}\ erg\ s^{-1}$, corresponding to a star formation rate of $\gtrsim 2\ \rm M_{\odot}\ yr^{-1}$ (considering a lower limit on Ly$α$ escape fraction $f_{esc}^{Lyα} \sim 2\%$) as typical for Lyman break galaxies at these redshifts. The Ly$α$ emission is blueshifted with respect to the systemic redshift derived from metal absorption lines by $281 \pm 43$ km/s. The associated galaxy is at very small impact parameter of $\lesssim 12 \rm\ kpc$ from the background quasar, which is in line with the observed anticorrelation between column density and impact parameter in spectroscopic searches tracing the large-scale environments of DLA host galaxies.

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arXiv2020

A possible bright ultraviolet flash from a galaxy at redshift z ~ 11

In the optical sky, minutes-duration transients from cosmological distances are rare. Known objects that give rise to such transients include gamma-ray bursts (GRBs), the most luminous explosions in the universe that have been detected at redshift as high as z ~ 9.4. These high-redshift GRBs and their associated emission can be used to probe the star formation and reionization history in the era of cosmic dawn. Here we report a near-infrared transient with an observed duration shorter than 245 s coincident with the luminous star-forming galaxy GN-z11 at z ~ 11. The telluric absorption shown in the near-infrared spectrum indicates its origin from above the atmosphere. We can rule out the possibility of known man-made objects or moving objects in the Solar system based on the observational information and our current understanding of the properties of these objects. Since some long-duration GRBs are associated with a bright ultraviolet (UV) or optical flash, we investigate the possibility that the detected signal arose from a rest-frame UV flash associated with a long GRB from GN-z11. Despite the very low probability of being a GRB, we find that the spectrum, brightness, and duration of the transient are consistent with such an interpretation. Our result may suggest that long GRBs can be produced as early as 420 million years after the Big Bang.

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arXiv2020

Evidence for GN-z11 as a luminous galaxy at redshift 10.957

GN-z11 was photometrically selected as a luminous star-forming galaxy candidate at redshift z > 10 based on Hubble Space Telescope (HST) imaging data. Follow-up HST near-infrared grism observations detected a continuum break that was explained as the Ly-alpha break corresponding to z = 11.09 (+0.08-0.12). However, its accurate redshift remained unclear. Here we report a probable detection of three ultraviolet (UV) emission lines from GN-z11, which can be interpreted as the [C III] 1907, C III] 1909 doublet and O III] 1666 at z = 10.957+/-0.001 (when the Universe was only ~420 Myr old, or ~3% of its current age). This is consistent with the redshift of the previous grism observations, supporting GN-z11 as the most distant galaxy known to date. Its UV lines likely originate from dense ionized gas that is rarely seen at low redshifts, and its strong [C III] and C III] emission is partly due to an active galactic nucleus (AGN) or enhanced carbon abundance. GN-z11 is luminous and young, yet moderately massive, implying a rapid build-up of stellar mass in the past. Future facilities will be able to find the progenitors of such galaxies at higher redshift and probe the cosmic epoch in the beginning of re-ionization.

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arXiv2020

Strong Mg II and Fe II Absorbers at 2.2 < z < 6.0

We present a study of strong intervening absorption systems in the near-IR spectra of 31 luminous quasars at $z>5.7$. The quasar spectra were obtained with {\it Gemini} GNIRS that provide continuous wavelength coverage from $\sim$0.9 to $\sim$2.5 $μ$m. We detect 32 strong Mg II doublet absorbers with rest-frame equivalent width $W_r$ ($\lambda2796$) $>1.0$ Åat $2.2 < z < 6.0$. Each Mg II absorber is confirmed by at least two associated Fe II absorption lines in the rest-frame wavelength range of $\sim 1600-2600$ Å. We find that the comoving line density ($dN/dX$) of the strong Fe II-bearing Mg II absorbers decreases towards higher redshift at $z>3$, consistent with previous studies. Compared with strong Mg II absorbers detected in damped Ly$α$ systems at 2 $<z<$ 4, our absorbers are potentially less saturated and show much larger rest-frame velocity widths. This suggests that the gas traced by our absorbers are potentially affected by galactic superwinds. We analyze the {\it Hubble Space Telescope} near-IR images of the quasars and identify possible associated galaxies for our strong absorbers. There are a maximum of two galaxy candidates found within 5" radius of each absorber. The median F105W-band magnitude of these galaxy candidates is 24.8 mag, which is fainter than the $L^*$ galaxy luminosity at $z\sim$ 4. By using our observed $dN/dX$ of strong Mg II absorbers and galaxy candidates median luminosity, we suggest that at high redshift, strong Mg II absorbers tend to have a more disturbed environment but smaller halo size than that at $z <$ 1.

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arXiv2020

The Infrared Medium-deep Survey. VIII. Quasar Luminosity Function at $z\sim5$

Faint $z\sim5$ quasars with $M_{1450}\sim-23$ mag are known to be the potentially important contributors to the ultraviolet ionizing background in the post-reionization era. However, their number density has not been well determined, making it difficult to assess their role in the early ionization of the intergalactic medium (IGM). In this work, we present the updated results of our $z\sim5$ quasar survey using the Infrared Medium-deep Survey (IMS), a near-infrared imaging survey covering an area of 85 deg$^{2}$. From our spectroscopic observations with the Gemini Multi-Object Spectrograph (GMOS) on the Gemini-South 8 m Telescope, we discovered eight new quasars at $z\sim5$ with $-26.1\leq M_{1450} \leq -23.3$. Combining our IMS faint quasars ($M_{1450}>-27$ mag) with the brighter Sloan Digital Sky Survey (SDSS) quasars ($M_{1450}<-27$ mag), we derive the $z\sim5$ quasar luminosity function (QLF) without any fixed parameters down to the magnitude limit of $M_{1450}=-23$ mag. We find that the faint-end slope of the QLF is very flat ($α=-1.2^{+1.4}_{-0.6}$), with a characteristic luminosity of $M^{*}_{1450}=-25.8^{+1.4}_{-1.1}$ mag. The number density of $z\sim5$ quasars from the QLF gives an ionizing emissivity at 912 $\unicode{x212B}$ of $ε_{912}=(3.7$--$7.1)\times10^{23}$ erg s$^{-1}$ Hz$^{-1}$ Mpc$^{-3}$ and an ionizing photon density of $\dot{n}_{\rm ion}=(3.0$--$5.7)\times10^{49}$ Mpc$^{-3}$ s$^{-1}$. These results imply that quasars are responsible for only 10-20% (up to 50% even in the extreme case) of the photons required to completely ionize the IGM at $z\sim5$, disfavoring the idea that quasars alone could have ionized the IGM at $z\sim5$.

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arXiv2020

Discovery of an Enormous Ly$α$ nebula in a massive galaxy overdensity at $z=2.3$

Enormous Ly$α$ Nebulae (ELANe), unique tracers of galaxy density peaks, are predicted to lie at the nodes and intersections of cosmic filamentary structures. Previous successful searches for ELANe have focused on wide-field narrowband surveys, or have targeted known sources such as ultraluminous quasi-stellar-objects (QSOs) or radio galaxies. Utilizing groups of coherently strong Ly$α$ absorptions (CoSLAs), we have developed a new method to identify high-redshift galaxy overdensities and have identified an extremely massive overdensity, BOSS1441, at $z=2-3$ (Cai et al. 2016a). In its density peak, we discover an ELAN that is associated with a relatively faint continuum. To date, this object has the highest diffuse Ly$α$ nebular luminosity of $L_{\rm{nebula}}=5.1\pm0.1\times10^{44}$ erg s$^{-1}$. Above the 2$σ$ surface brightness limit of SB$_{\rm{Lyα}}= 4.8\times10^{-18}$ erg s$^{-1}$ cm$^{-2}$ arcsec$^{-2}$, this nebula has an end-to-end spatial extent of 442 kpc. This radio-quiet source also has extended \civ\ $\lambda1549$ and \heii\ $\lambda1640$ emission on $\gtrsim30$ kpc scales. Note that the Ly$α$, \heii\ and \civ\ emission all have double-peaked line profiles. Each velocity component has a full-width-half-maximum (FWHM) of $\approx700 - 1000$ km s$^{-1}$. We argue that this Ly$α$ nebula could be powered by shocks due to an AGN-driven outflow or/and photoionization by a strongly obscured source.

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arXiv2020

The Sloan Digital Sky Survey Reverberation Mapping Project: How Broad Emission Line Widths Change When Luminosity Changes

Quasar broad emission lines are largely powered by photoionization from the accretion continuum. Increased central luminosity will enhance line emissivity in more distant clouds, leading to increased average distance of the broad-line-emitting clouds and decreased averaged line width, known as the broad-line region (BLR) "breathing". However, different lines breathe differently, and some high-ionization lines, such as C IV, can even show "anti-breathing" where the line broadens when luminosity increases. Using multi-year photometric and spectroscopic monitoring data from the Sloan Digital Sky Survey Reverberation Mapping project, we quantify the breathing effect ($Δ$log W=$αΔ$log L) of broad H$α$, H$β$, Mg II, C IV, and C III] for statistical quasar samples over $z\approx 0.1-2.5$. We found that H$β$ displays the most consistent normal breathing expected from the virial relation ($α\sim-0.25$), Mg II and H$α$ on average show no breathing ($α\sim 0$), and C IV (and similarly C III] and Si IV mostly shows anti-breathing ($α>0$). The anti-breathing of C IV can be well understood by the presence of a non-varying core component in addition to a reverberating broad-base component, consistent with earlier findings. The deviation from canonical breathing introduces extra scatter (a luminosity-dependent bias) in single-epoch virial BH mass estimates due to intrinsic quasar variability, which underlies the long argued caveats of C IV single-epoch masses. Using the line dispersion instead of FWHM leads to less, albeit still substantial, deviations from canonical breathing in most cases. Our results strengthen the need for reverberation mapping to provide reliable quasar BH masses, and quantify the level of variability-induced bias in single-epoch BH masses based on various lines.

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arXiv2020

The Magellan M2FS Spectroscopic Survey of High-Redshift Galaxies: A Sample of 260 Ly$α$ Emitters at Redshift $z\approx5.7$

We present a spectroscopic survey of Ly$α$ emitters (LAEs) at $z\approx5.7$ using the multi-object spectrograph M2FS on the Magellan Clay telescope. This is part of a high-redshift galaxy survey carried out in several well-studied deep fields. These fields have deep images in multiple UV/optical bands, including a narrow NB816 band that has allowed an efficient selection of LAE candidates at $z\approx5.7$. Our sample consists of 260 LAEs and covers a total effective area of more than two square degrees on the sky. This is so far the largest (spectroscopically confirmed) sample of LAEs at this redshift. We use the secure redshifts and narrowband photometry to measure Ly$α$ luminosities. We find that these LAEs span a Ly$α$ luminosity range of $\sim 2\times10^{42} - 5\times10^{43}$ erg s$^{-1}$, and include some of the most luminous galaxies known at $z \ge 5.7$ in terms of Ly$α$ luminosity. Most of them have rest-frame equivalent widths between 20 and 300 Å, and more luminous Ly$α$ emission lines tend to have broader line widths. We detect a clear offset of $\sim20$ Å between the observed Ly$α$ wavelength distribution and the NB816 filter transmission curve, which can be explained by the intergalactic medium absorption of continua blueward of Ly$α$ in the high-redshift spectra. This sample is being used to study the Ly$α$ luminosity function and galaxy properties at $z\approx5.7$.

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arXiv2020

A Spectroscopic Survey of Ly$α$ Emitters at $z\approx3.1$ over $\sim$1.2 Deg$^2$

We present a spectroscopic survey of Ly$α$ emitters (LAEs) at $z\approx3.1$ in the Subaru MM-Newton Deep Survey Field. This field has deep imaging data in a series of broad and narrow bands, including two adjacent narrow bands NB497 and NB503 that have allowed us to efficiently select LAE candidates at $z\approx3.1$. Using spectroscopic observations on MMT Hectospec and Magellan M2FS, we obtained a sample of 166 LAEs at $z\approx3.1$ over an effective area of $\sim$1.2 deg$^2$, including 16 previously known LAEs. This is so far the largest (spectroscopically confirmed) sample of LAEs at this redshift. We make use of the secure redshifts and multi-band data to measure spectral properties such as Ly$α$ luminosity and rest-frame UV slope. We derive a robust Ly$α$ luminosity function (LF) that spans a luminosity range from $\sim10^{42.0}$ to $>10^{43.5}$ erg s$^{-1}$. Significant overdense and underdense regions are detected in our sample, but the area coverage is wide enough to largely suppress the effect from such cosmic variance. Our Ly$α$ LF is generally consistent with those from previous studies at $z \sim 3.1$. At the brightest end of the LF, there is a tentative detection of a density excess that is not well described by the Schechter function. The comparison with the LFs at other redshifts suggests that the Ly$α$ LF does not show significant evolution at $2<z<5$. Finally, we build the composite spectra of the LAEs and detect the NVI and CIV doublet emission lines at significance of $\sim 4 σ$, suggesting very hard radiation fields in (some of) these LAEs.

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arXiv2020

SCUBA2 High Redshift Bright Quasar Survey: Far-infrared Properties and Weak-line Features

We present a submillimetre continuum survey ('SCUBA2 High rEdshift bRight quasaR surveY', hereafter SHERRY) of 54 high redshift quasars at $5.6 3.5σ$). The new SHERRY detections indicate far-infrared (FIR) luminosities of $\rm 3.5\times10^{12}$ to $\rm 1.4\times10^{13}$ $L_{\odot}$, implying extreme star formation rates of 90 to 1060 $M_{\odot}$ yr$^{-1}$ in the quasar host galaxies. Compared with $z =$ 2$-$5 samples, the FIR luminous quasars ($L_{\rm FIR} > 10^{13}\,L_{\odot}$) are more rare at $z \sim 6$. The optical/near-infrared (NIR) spectra of these objects show 11% (6/54) of the sources have weak Ly$α$, emission line features, which may relate to different sub-phases of the central active galactic nuclei (AGNs). Our SCUBA2 survey confirms the trend reported in the literature that quasars with submillimeter detections tend to have weaker ultraviolet (UV) emission lines compared to quasars with nondetections. The connection between weak UV quasar line emission and bright dust continuum emission powered by massive star formation may suggest an early phase of AGN-galaxy evolution, in which the broad line region is starting to develop slowly or is shielded from the central ionization source, and has unusual properties such as weak line features or bright FIR emission.

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arXiv2020

A Carbon-enhanced Lyman Limit System: Signature of the First Generation of Stars?

We present the study of a Lyman limit system (LLS) at $z_{\rm abs}$ = 1.5441 towards quasar J134122.50+185213.9 observed with VLT X-shooter. This is a very peculiar system with strong C I absorption seen associated with a neutral hydrogen column density of log $N$(H I) (cm$^{-2}$) = 18.10, too small to shield the gas from any external UV flux. The low ionization absorption lines exhibit a simple kinematic structure consistent with a single component. Using CLOUDY models to correct for ionization, we find that the ionization parameter of the gas is in the range $-$ 4.5 $<$ log $U$ $<$ $-$4.2 and the gas density $-$1.5 $<$ log $n$(H) (cm$^{-3}$) $<$ $-$1.2. The models suggest that carbon is overabundant relative to iron, [C/Fe] $>$ +2.2 at [Fe/H] $\sim$ $-$1.6. Such a metal abundance pattern is reminiscent of carbon-enhanced metal-poor stars detected in the Galaxy halo. Metal enrichment by the first generation of supernovae provides a plausible explanation for the inferred abundance pattern in this system.

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arXiv2020

Limits to Rest-Frame Ultraviolet Emission From Far-Infrared-Luminous z~6 Quasar Hosts

We report on a Hubble Space Telescope search for rest-frame ultraviolet emission from the host galaxies of five far-infrared-luminous $z\simeq{}6$ quasars and the $z=5.85$ hot-dust free quasar SDSS J0005-0006. We perform 2D surface brightness modeling for each quasar using a Markov-Chain Monte-Carlo estimator, to simultaneously fit and subtract the quasar point source in order to constrain the underlying host galaxy emission. We measure upper limits for the quasar host galaxies of $m_J>22.7$ mag and $m_H>22.4$ mag, corresponding to stellar masses of $M_\ast<2\times10^{11}M_\odot$. These stellar mass limits are consistent with the local $M_{\textrm{BH}}$-$M_\ast$ relation. Our flux limits are consistent with those predicted for the UV stellar populations of $z\simeq6$ host galaxies, but likely in the presence of significant dust ($\langle A_{\mathrm{UV}}\rangle\simeq 2.6$ mag). We also detect a total of up to 9 potential $z\simeq6$ quasar companion galaxies surrounding five of the six quasars, separated from the quasars by 1.4''-3.2'', or 8.4-19.4 kpc, which may be interacting with the quasar hosts. These nearby companion galaxies have UV absolute magnitudes of -22.1 to -19.9 mag, and UV spectral slopes $β$ of -2.0 to -0.2, consistent with luminous star-forming galaxies at $z\simeq6$. These results suggest that the quasars are in dense environments typical of luminous $z\simeq6$ galaxies. However, we cannot rule out the possibility that some of these companions are foreground interlopers. Infrared observations with the James Webb Space Telescope will be needed to detect the $z\simeq6$ quasar host galaxies and better constrain their stellar mass and dust content.

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arXiv2020

The Sloan Digital Sky Survey Reverberation Mapping Project: Photometric g and i Light Curves

The Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) program monitors 849 active galactic nuclei (AGN) both spectroscopically and photometrically. The photometric observations used in this work span over four years and provide an excellent baseline for variability studies of these objects. We present the photometric light curves from 2014 to 2017 obtained by the Steward Observatory's Bok telescope and the CFHT telescope with MegaCam. We provide details on the data acquisition and processing of the data from each telescope, the difference imaging photometry used to produce the light curves, and the calculation of a variability index to quantify each AGN's variability. We find that the Welch-Stetson J-index provides a useful characterization of AGN variability and can be used to select AGNs for further study.

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arXiv2020

Pōniuā'ena: A Luminous $z=7.5$ Quasar Hosting a 1.5 Billion Solar Mass Black Hole

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$α$ 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 $μ$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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arXiv2020

Metal enrichment in the circumgalactic medium and Lyα haloes around quasars at z $\sim$3

Deep observations have detected extended Ly$α$ emission nebulae surrounding tens of quasars at redshift 2 to 6. However, the metallicity of such extended haloes is still poorly understood. We perform a detailed analysis on a large sample of 80 quasars at $z\sim3$ based on MUSE-VLT data. We find clear evidence of extended emission of the UV nebular lines such as CIV or HeII for about 20$\%$ of the sample, while CIII] is only marginally detected in a few objects. By stacking the cubes we detect emission of CIV, HeII and CIII] out to a radius of about 45 kpc. CIV and HeII show a radial decline much steeper than Ly$α$, while CIII] shows a shallower profile similar to Ly$α$ in the inner 45 kpc. We infer that the average metallicity of the circumgalactic gas within the central 30-50~kpc is $\sim$0.5 solar, or even higher. However, we also find evidence of a component of the Ly$α$ haloes, which has much weaker metal emission lines relative to Ly$α$. We suggest that the high metallicity of the circumgalactic medium within the central 30-50 kpc is associated with chemical pre-enrichment by past quasar-driven outflows and that there is a more extended component of the CGM that has much lower metallicity and likely associated with near-pristine gas accreted from the intergalactic medium. We show that our observational results are in good agreement with the expectations of the FABLE zoom-in cosmological simulations.

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arXiv2020

A Significantly Neutral Intergalactic Medium Around the Luminous z=7 Quasar J0252-0503

Luminous $z\ge7$ quasars provide direct probes of the evolution of supermassive black holes (SMBHs) and the intergalactic medium (IGM) during the epoch of reionization (EoR). The Ly$α$ damping wing absorption imprinted by neutral hydrogen in the IGM can be detected in a single EoR quasar spectrum, allowing the measurement of the IGM neutral fraction towards that line of sight. However, damping wing features have only been detected in two $z>7$ quasars in previous studies. In this paper, we present new high quality optical and near-infrared spectroscopy of the $z=7.00$ quasar DES J025216.64--050331.8 obtained with Keck/NIRES and Gemini/GMOS. By using the MgII single-epoch virial method, we find that it hosts a $\rm (1.39\pm0.16) \times10^{9} ~M_\odot$ SMBH accreting at an Eddington ratio of $λ_{\rm Edd}=0.7\pm0.1$, consistent with the values seen in other luminous $z\sim 7$ quasars. Furthermore, the Ly$α$ region of the spectrum exhibits a strong damping wing absorption feature. The lack of associated metal absorption in the quasar spectrum indicates that this absorption is imprinted by a neutral IGM. Using a state-of-the-art model developed by Davies et al., we measure a volume-averaged neutral hydrogen fraction at $z=7$ of $\langle x_{\rm HI} \rangle = 0.70^{+0.20}_{-0.23} (^{+0.28}_{-0.48})$ within 68% (95%) confidence intervals when marginalizing over quasar lifetimes of $10^3\le t_{\rm Q}\le10^8$ yr. This is the highest IGM neutral fraction yet measured using reionization-era quasar spectra.

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arXiv2020

The Lyman Continuum Escape Fraction of Galaxies and AGN in the GOODS Fields

We present our analysis of the LyC emission and escape fraction of 111 spectroscopically verified galaxies with and without AGN from $2.26<z<4.3$. We extended our ERS sample from Smith et al. (2018; arXiv:1602.01555) with 64 galaxies in the GOODS North and South fields using WFC3/UVIS F225W, F275W, and F336W mosaics we independently drizzled using the HDUV, CANDELS, and UVUDF data. Among the 17 AGN from the 111 galaxies, one provided a LyC detection in F275W at $m_{AB}=23.19$ mag (S/N $\simeq$ 133) and $GALEX$ NUV at $m_{AB}=23.77$ mag (S/N $\simeq$ 13). We simultaneously fit $SDSS$ and $Chandra$ spectra of this AGN to an accretion disk and Comptonization model and find $f_{esc}$ values of $f_{esc}^{F275W}\simeq 28^{+20}_{-4}$% and $f_{esc}^{NUV}\simeq 30^{+22}_{-5}$%. For the remaining 110 galaxies, we stack image cutouts that capture their LyC emission using the F225W, F275W, and F336W data of the GOODS and ERS samples, and both combined, as well as subsamples of galaxies with and without AGN, and $all$ galaxies. We find the stack of 17 AGN dominate the LyC production from $\langle z\rangle\simeq 2.3-4.3$ by a factor of $\sim$10 compared to all 94 galaxies without AGN. While the IGM of the early universe may have been reionized mostly by massive stars, there is evidence that a significant portion of the ionizing energy came from AGN.

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