The Rest-Frame Extreme Ultraviolet Spectral Properties of QSOs

Abstract

We use a sample of 332 Hubble Space Telescope spectra of 184 QSOs with z > 0.33 to study the typical ultraviolet spectral properties of QSOs, with emphasis on the ionizing continuum. Our sample is nearly twice as large as that of Zheng et al. (1997) and provides much better spectral coverage in the extreme ultraviolet (EUV). The overall composite continuum can be described by a power law with index alpha_EUV = -1.76 +/- 0.12 (f_nu ~ nu^alpha) between 500 and 1200 Angstroms. The corresponding results for subsamples of radio-quiet and radio-loud QSOs are alpha_EUV = -1.57 +/- 0.17 and alpha_EUV = -1.96 +/- 0.12, respectively. We also derive alpha_EUV for as many individual objects in our sample as possible, totaling 39 radio-quiet and 40 radio-loud QSOs. The typical individually measured values of alpha_EUV are in good agreement with the composites. We find no evidence for evolution of alpha_EUV with redshift for either radio-loud or radio-quiet QSOs. However, we do find marginal evidence for a trend towards harder EUV spectra with increasing luminosity for radio-loud objects. An extrapolation of our radio-quiet QSO spectrum is consistent with existing X-ray data, suggesting that the ionizing continuum may be represented by a single power law. The resulting spectrum is roughly in agreement with models of the intergalactic medium photoionized by the integrated radiation from QSOs.

14 pages using emulateapj, 15 figures, accepted for publication in ApJ

References in corpus (2)

• Composite Quasar Spectra From the Sloan Digital Sky Survey
• Resolving the Structure of Ionized Helium in the Intergalactic Medium with the Far Ultraviolet Spectroscopic Explorer

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• Extreme UV QSOs
• Serendipitous AGN in the XMM-Newton fields of Markarian 205 and QSO 0130-403
• Uncovering the Spectral Energy Distribution in Active Galaxies Using High Ionization Mid-infrared Emission Lines
• Extinction properties of lensing galaxies
• An Ultraviolet Survey of Low-Redshift Partial Lyman-Limit Systems with the HST Cosmic Origins Spectrograph
• The Kast Ground Based UV Spectral Survey of 79 QSOs at Redshift 2 for Lyman Alpha Forest and Metal Absorption
• An Apparent Redshift Dependence of Quasar Continuum: Implication for Cosmic Dust Extinction?
• A Highly Magnified Gravitationally Lensed Red QSO at z = 2.5 with a Significant Flux Ratio Anomaly
• Helium Reionization Simulations. I. Modeling Quasars as Radiation Sources
• He II optical depth and UV escape fraction of galaxies
• A quasar hiding behind two dusty absorbers. Quantifying the selection bias of metal-rich, damped Lyman-alpha absorption systems
• On the Location and Composition of the Dust in the MCG-6-30-15 Warm Absorber
• Constraining the Gravitational Lensing of $z\gtrsim 6$ Quasars from their Proximity Zones
• Fossil Ionized Bubbles Around Dead Quasars During Reionization
• The Extreme Red Excess in Blazar Ultraviolet Broad Emission Lines
• Ultraviolet and X-ray Variability of the Seyfert 1.5 Galaxy Markarian 817
• Evidence of the Dynamics of Relativistic Jet Launching in Quasars
• Discovery of Two Spectroscopically Peculiar, Low-Luminosity Quasars at z~4
• Spectroscopy of the spatially-extended Lya emission around a QSO at z=6.4
• ELDAR, a new method to identify AGN in multi-filter surveys: the ALHAMBRA test-case
• The Relativistic Jet-Accretion Flow-Wind Connection in Mrk\,231
• Photometric Properties of the Most Massive High-Redshift Galaxies
• Energy distribution of individual quasars from far-UV to X-rays: I. Intrinsic UV hardness and dust opacities
• The Race Between Stars and Quasars in Reionizing Cosmic Hydrogen
• Highly Ionized Collimated Outflow from HE 0238 - 1904
• Calibrating Milky Way dust extinction using cosmological sources
• Photoionization models for extreme Ly$\alpha$ $\lambda$1216 and HeII $\lambda$1640 ratios in quasar halos, and PopIII vs AGN diagnostics
• The Extreme Ultraviolet Deficit and Magnetically Arrested Accretion in Radio Loud Quasars
• The luminosity dependence of quasar UV continuum slope: dust extinction scenario
• Connecting Low- and High-Redshift Weak Emission-Line Quasars via HST Spectroscopy of Ly$\alpha$ Emission
• VLT spectropolarimetry of two powerful radio galaxies at z~1.4: UV continuum, emission-line properties and the nature of high-redshift dust
• The Mass and Absorption Columns of Galactic Gaseous Halos II -- The High Ionization State Ions
• Metal enrichment by radiation pressure in active galactic nucleus outflows -- theory and observations
• The Extreme Ultraviolet Variability of Quasars
• The impact of temperature fluctuations on the large-scale clustering of the Ly$\alpha$ forest
• Multi-Epoch Observations of the Redwing Excess in the Spectrum of 3C279
• A Multi-wavelength Analysis of Binary-AGN Candidate PSO J334.2028+01.4075
• Ionizing radiation from AGNs at z>3.3 with the Subaru Hyper Suprime-Cam Survey and the CFHT Large Area U-band Deep Survey (CLAUDS)
• A Limit Relation between Black Hole Mass and H$\beta$ Width: Testing Super-Eddington Accretion in Active Galactic Nuclei
• Looking at quasars through galaxies
• Clumping factors of HII, HeII and HeIII
• Detecting the Highest Redshift (z > 8) QSOs in a Wide, Near Infrared Slitless Spectroscopic Survey
• Non-Sobolev modelling of radiation pressure driven flows in Active Galactic Nuclei
• Active Galactic Nuclei Selected from GALEX Spectroscopy: The Ionizing Source Spectrum at z~1
• Mapping the low surface brightness Universe in the UV band with Lya emission from IGM filaments
• On the emission lines in active galactic nuclei with relativistic jets
• Extremely metal-poor Lyman limit system at z = 2.917 toward the quasar HE 0940-1050
• Semi-numeric simulations of helium reionization and the fluctuating radiation background
• A Candidate Dual QSO at Cosmic Noon
• Revisiting the Completeness and the Luminosity Function in High-Redshift Low-Luminosity Quasar Surveys
• The relativistic jet of the $\gamma$-ray emitting narrow-line Seyfert 1 galaxy PKS J1222$+$0413
• Enhanced Detectability of Pre-reionization 21-cm Structure
• Constraints on the densities and temperature of Seyfert 2 NLR
• The EUV variability of the luminous QSO HS 1700+6416
• New Clues to Jet Launching: The inner disks in radio loud quasars may be more stable
• Constraining UV Continuum Slopes of Active Galactic Nuclei With CLOUDY Models of Broad Line Region EUV Emission Lines
• Hubble Space Telescope Ultraviolet Spectroscopy of Fourteen Low-Redshift Quasars
• uGMRT search for cold gas at z~1-1.4 towards red quasars
• Eddington accreting Black Holes in the Epoch of Reionization
• Continuum reverberation mapping of MCG 08-11-011
• Evolution of the Lyman-alpha Halos around High-Redshift Radio Galaxies
• The Extreme Ultraviolet Deficit - Jet Connection in the Quasar 1442+101
• PKS 1018-42: A Powerful Kinetically Dominated Quasar
• Joint Survey Processing I: Compact oddballs in the COSMOS field -- low-luminosity Quasars at z > 6?
• Estimating the Jet Power of Mrk\,231 During the 2017-2018 Flare
• Constraining broad-line regions from time lags of broad emission lines relative to radio emission
• A Search for H I Lyman $\alpha$ Counterparts to Ultra-Fast X-ray Outflows
• Spatial Correlations in the Helium-Ionizing Background
• The HeI 584 A Forest as a Diagnostic of Helium Reionization
• Covering factors of the dusty obscurers in radio-loud and radio-quiet quasars
• The Nature of the UV/X-Ray Absorber in PG 2302+029
• Combined constraints on intergalactic dust from quasar colours and the soft X-ray background
• The emission line spectrum of the UV deficient quasar Ton 34: evidence of shock excitation?
• The Detection of Diffuse Extended Structure in 3C~273: Implications for Jet Power
• Composite spectra of quasars with different UV spectral index
• Cosmological radiative transfer for the line-of-sight proximity effect
• Infrared Colours and Spectral Energy Distributions of Hard X-ray Selected Obscured and Compton-thick AGN
• Euclid preparation. Observational expectations for redshift z<7 active galactic nuclei in the Euclid Wide and Deep surveys
• Optical and near-infrared spectroscopy of quasars at $z>6.5$: public data release and composite spectrum
• Technique for detecting warm-hot intergalactic gas in quasar UV spectra
• The Highly Self-Absorbed Blazar, PKS\,1351$-$018
• Stellar population and dust extinction in an ultraluminous infrared galaxy at z=1.135
• The X-Rays wind connection in PG 2112+059
• The near-infrared SED of blue quasars: what drives the evolution of the dusty torus?
• Cosmic reionization of hydrogen and helium: contribution from both mini-quasars and stars
• HYPERION: broad-band X-ray-to-near-infrared emission of Quasars in the first billion years of the Universe
• The broad OVI absorber at z = 3.02 toward CTQ 325
• Pair Cascades at the Edge of the Broad-Line Region Shaping the Gamma-Ray Spectrum of 3C 279
• The Powerful Jet and Gamma-Ray Flare of the Quasar PKS 0438$-$436
• Deep CFHT Y-band Imaging of VVDS-F22 Field: II. Quasar Selection and Quasar Luminosity Function
• Quasar spectral energy distribution in EUV restored from associated absorbers: indications to the HeII opacity of the quasar accretion disk wind
• A search for cosmological anisotropy using the Lyman alpha forest from SDSS quasar spectra
• PKS 1622-253: A Weakly Accreting, Powerful Gamma Ray Source
• The Composite Spectral Energy Distribution of Quasars is Surprisingly Universal Since Cosmic Noon
• The Extreme Ultraviolet Spectra of Low Redshift Radio Loud Quasars
• The optical luminosity function of LOFAR radio-selected quasars at $1.4\le z\le 5.0$ in the NDWFS-Boötes field
• NuSTAR observations of a heavily X-ray obscured AGN in the dwarf galaxy J144013+024744
• The unusual UV continuum of quasar Ton 34 and the possibility of crystalline dust absorption
• Development of Hydrogen and Helium Proximity Zones around Quasars
• Quasars' Optical Polarization and Balmer Edge Feature Revealed by Ultra-Violet, and Polarized Visible to Near Infrared Emissions
• Spectral Energy Distribution Variations of Nearby Seyfert Galaxies During AGN Watch Monitoring Programs
• Constraining X-ray emission of magnetically arrested disk (MAD) by radio-loud AGNs with extreme ultraviolet (EUV) deficit
• Large scale environmental bias of the QSO line of sight proximity effect
• The Energetics of Launching the Most Powerful Jets in Quasars: A Study of 3C82
• Ultraviolet background fluctuations with clustered sources
• Extremely strong DLAs at high redshift: Gas cooling and H${}_2$ formation
• Towards modelling Ghostly DLAs
• Stochastic Absorption of the Light of Background Sources due to Intergalactic Neutral Hydrogen I. Testing different line-number evolution models via the cosmic flux decrement
• On the Metallicities and Kinematics of the Circumgalactic Media of Damped Ly$\alpha$ Systems at $z\sim 2.5$
• Quasar 3C298: a test-case for meteoritic nanodiamond 3.5 microns emission
• Simulating the epoch of Helium Reionization in photon-conserving semi-numerical code SCRIPT
• Constraining the ratio of median pixel optical depth profile around z ~ 4 quasars using the longitudinal proximity effect
• Spectral Signatures of Quasar Ages at z~3
• Active Galaxies in the UV
• Physical conditions in high$-$z optically thin C III absorbers: Origin of cloud sizes and associated correlations
• Exploratory Study of Transverse Proximity Effect around BAL Quasars
• The Kinetically Dominated Quasar 3C~418
• The Energetics of the Central Engine in the Powerful Quasar, 3C298
• Nanodiamond dust and the energy distribution of quasars
• Physical conditions and redshift evolution of optically thin C III absorbers: Low-z sample
• The FRII Broad Line Seyfert 1 Galaxy: PKSJ 1037-2705
• Observing the influence of growing black holes on the pre-reionization IGM
• Optimized Spectral Energy Distribution for Seyfert Galaxies
• A universal 21 cm signature of growing massive black holes in the early Universe
• The effect of helium reionization on the Lyman-alpha forest hydrogen flux statistics
• Euclid: Discovery of 31 new quasars at $6.6<z<7.8$
• Early Stages of Dusty Tori: The First Infrared Spectra from a Highly Multiscale Quasar Simulation
• Ultra-luminous high-redshift quasars from SkyMapper -- II. New quasars and the bright end of the luminosity function
• Probing Reionization with the Cosmological Proximity Effect and High-Redshift Supernovae Rates
• The Contribution of AGN Accretion Disks to Hydrogen Reionization