On the Search for Quasar Light Echoes

Abstract

The UV radiation from a quasar leaves a characteristic pattern in the distribution of ionized hydrogen throughout the surrounding space. This pattern or light echo propagates through the intergalactic medium at the speed of light, and can be observed by its imprint on the Ly-alpha forest spectra of background sources. As the echo persists after the quasar has switched off, it offers the possibility of searching for dead quasars, and constraining their luminosities and lifetimes. We outline a technique to search for and characterize these light echoes. To test the method, we create artificial Ly-alpha forest spectra from cosmological simulations at z=3, apply light echoes and search for them. We show how the simulations can also be used to quantify the significance level of any detection. We find that light echoes from the brightest quasars could be found in observational data. With absorption line spectra of 100 redshift z~3-3.5 quasars or galaxies in a 1 square degree area, we expect that ~10 echoes from quasars with B band luminosities L_B=3x10^45 ergs/s exist that could be found at 95% confidence, assuming a quasar lifetime of ~10^7 yr. Even a null result from such a search would have interesting implications for our understanding of quasar luminosities and lifetimes.

9 pages, 7 figures, ApJ in press

References in corpus (38)

• First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Determination of Cosmological Parameters
• Unified Schemes for Radio-Loud Active Galactic Nuclei
• Energy input from quasars regulates the growth and activity of black holes and their host galaxies
• Modeling feedback from stars and black holes in galaxy mergers
• The Cosmic Evolution Survey (COSMOS) -- Overview
• GADGET: A code for collisionless and gasdynamical cosmological simulations
• Radiative Transfer in a Clumpy Universe: II. The Utraviolet Extragalactic Background
• An Observational Determination of the Bolometric Quasar Luminosity Function
• The SDSS Quasar Survey: Quasar Luminosity Function from Data Release Three
• Galaxies and Intergalactic Matter at Redshift z~3: Overview
• The Lyman Alpha Forest in the Spectra of QSOs
• The Low Redshift Lyman Alpha Forest in Cold Dark Matter Cosmologies
• Gravitational Collapse of Small-Scale Structure as the Origin of the Lyman Alpha Forest
• The Lyman-alpha Forest in the Cold Dark Matter Model
• Recovery of the Power Spectrum of Mass Fluctuations from Observations of the Lyman-alpha Forest
• The thermal history of the intergalactic medium
• Metallicity of the intergalactic medium using pixel statistics. II. The distribution of metals as traced by C IV
• The Opacity of the Lyman Alpha Forest and Implications for Omega_{baryon} and the Ionizing Background
• A Physical Model for the Origin of Quasar Lifetimes
• P3M-SPH simulations of the Lyman-alpha Forest
• Measuring the cosmological constant with redshift surveys
• The Direct Detection of Lyman-Continuum Emission from Star-forming Galaxies at z~3
• The Palomar Distant Cluster Survey: I. The Cluster Catalog
• A Multi-Species Model for Hydrogen and Helium Absorbers in Lyman-Alpha Forest Clouds
• Constraining the Topology of the Universe
• The evolution of faint AGN between z~1 and z~5 from the COMBO-17 survey
• Quasars Probing Quasars I: Optically Thick Absorbers Near Luminous Quasars
• Damped Lyman-alpha and Lyman Limit Absorbers in the Cold Dark Matter Model
• A Uniform Analysis of the Ly-alpha forest at z = 0 - 5: II. Measuring the mean intensity of the extragalactic ionizing background using the proximity effect
• Ionizing radiation fluctuations and large-scale structure in the Lyman-alpha forest
• Intergalactic Helium Absorption in Cold Dark Matter Models
• Properties of High-Redshift Lyman Alpha Clouds I. Statistical Analysis of the SSG Quasars
• The Transverse Proximity Effect: A Probe to the Environment, Anisotropy, and Megayear Variability of QSOs
• Quasars in the COSMOS Field
• Constraints on the UV metagalactic emissivity using the LyA forest
• The bispectrum of the Lyman-alpha forest at z~2-2.4 from a Large sample of UVES QSO Absorption Spectra (LUQAS)
• Measuring the Radiative Histories of QSOs with the Transverse Proximity Effect
• The apparent shape of the "Strömgren sphere'' around the highest-redshift QSOs with Gunn-Peterson troughs

Cited by in corpus (17)

• The transverse proximity effect in the z ~ 2 Lyman-alpha forest suggests QSO episodic lifetimes of ~1 Myr
• Three Lyman-alpha emitting galaxies within a quasar proximity zone at z=5.8
• Detecting and Characterizing Young Quasars II: Four Quasars at $z\sim 6$ with Lifetimes $<10^4$ years
• Statistical Detection of the HeII Transverse Proximity Effect: Evidence for Sustained Quasar Activity for $>$25 Million Years
• Metal Absorption Systems in Spectra of Pairs of QSOs
• Modeling the HeII Transverse Proximity Effect: Constraints on Quasar Lifetime and Obscuration
• Quasars Probing Quasars IX. The Kinematics of the Circumgalactic Medium Surrounding z ~ 2 Quasars
• Mapping quasar light echoes in 3D with Lyα forest tomography
• The triply-ionized carbon forest from eBOSS: cosmological correlations with quasars in SDSS-IV DR14
• Simulating MOS science on the ELT: Ly$\alpha$ forest tomography
• The Assembly of Black Hole Mass and Luminosity Functions of High-redshift Quasars via Multiple Accretion Episodes
• Observational Evidence for Large-Scale Gas Heating in a Galaxy Protocluster at z=2.30
• Ionization bias and the ghost proximity effect near $z\gtrsim 6$ quasars in the shadow of proximate absorption systems
• Probing Large-scale UV Background Inhomogeneity Associated with Quasars using Metal Absorption
• Photometric IGM Tomography: Efficiently Mapping Quasar Light Echoes with Deep Narrow Band Imaging
• A unique window into the Epoch of Reionisation: A double-peaked Lyman-$\alpha$ emitter in the proximity zone of a quasar at $z\sim 6.6$
• Prospects for constraining quasar ages with fiber spectrographs: quasar-induced Ly$\alpha$ emission from the intergalactic medium