Time-dependent behaviour of Lyman α photon transfer in a high-redshift optically thick medium

Xu, W.; Wu, Xiang-Ping; Fang, Li‐Zhi

doi:10.1111/j.1365-2966.2011.19539.x

Cited by 8 publications

(7 citation statements)

References 46 publications

(77 reference statements)

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“…Roy et al 2010). Roy et al (2010) and Xu et al (2011) have studied the Ly α response of spherical Damped Ly α haloes (DLAs; constant hydrogen density and temperature) to an ionizing flash of finite duration. The effect of dust on the escape times is negligible (Yang et al 2011b).…”

Section: Agn Duty Cycles and Delayed Ly α Responsementioning

confidence: 99%

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About AGN ionization echoes, thermal echoes and ionization deficits in low-redshift Lyα blobs

Schirmer

Malhotra

Levenson

et al. 2016

Mon. Not. R. Astron. Soc.

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We report the discovery of 14 Lyman-α blobs (LABs) at z ∼ 0.3, existing at least 4 − 7 billion years later in the Universe than all other LABs known. Their optical diameters are 20 − 70 kpc, and GALEX data imply Ly α luminosities of (0.4 − 6.3) × 10 43 erg s −1 . Contrary to high-z LABs, they live in low-density areas. They are ionized by AGN, suggesting that cold accretion streams as a power source must deplete between z = 2 and z = 0.3. We also show that transient AGN naturally explain the ionization deficits observed in many LABs: Their Ly α and X-ray fluxes decorrelate below 10 6 years because of the delayed escape of resonantly scattering Ly α photons. High Ly α luminosities do not require currently powerful AGN, independent of obscuration. Chandra X-ray data reveal intrinsically weak AGN, confirming the luminous optical nebulae as impressive ionization echoes. For the first time, we also report mid-infrared thermal echoes from the dusty tori. We conclude that the AGN have faded by 3 − 4 orders of magnitude within the last 10 4−5 years, leaving fossil UV, optical and thermal radiation behind. The host galaxies belong to the group of previously discovered Green Bean galaxies (GBs). Gemini optical imaging reveals smooth spheres, mergers, spectacular outflows and ionization cones. Because of their proximity and high flux densities, GBs are perfect targets to study AGN feedback, mode switching and the Ly α escape. The fully calibrated, coadded optical FITS images are publicly available.

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Section: Agn Duty Cycles and Delayed Ly α Responsementioning

confidence: 99%

“…The analyses of Roy et al (2010) and Xu et al (2011) were performed for spherical DLAs with high τ ≥ 10 6−7 . LABs are complex objects as witnessed by their vast range of morphologies, both for our low-z LABs as well as those at high redshift.…”

Section: Agn Duty Cycles and Delayed Ly α Responsementioning

confidence: 99%

About AGN ionization echoes, thermal echoes and ionization deficits in low-redshift Lyα blobs

Schirmer

Malhotra

Levenson

et al. 2016

Mon. Not. R. Astron. Soc.

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“…Accordingly, during their quasar phases, the AGN fill the LABs with Lyα photons; the latter are trapped because of resonant scattering and released only gradually. The observable Lyα light curve is thus a very damped response to the AGN's ionizing light curve (Roy et al 2010;Xu et al 2011). Effectively, the Lyα and X-ray light curves are decorrelated.…”

mentioning

confidence: 99%

NuSTAR Hard X-Ray Data and Gemini 3D Spectra Reveal Powerful AGN and Outflow Histories in Two Low-redshift Lyα Blobs

Kawamuro

Schirmer

Turner

et al. 2017

ApJ

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We have shown that Lyman-α blobs (LABs) may still exist even at z ∼ 0.3, about 7 billion years later than most other LABs known (Schirmer et al. 2016). Their luminous Lyα and [O iii] emitters at z ∼ 0.3 offer new insights into the ionization mechanism. This paper focuses on the two X-ray brightest LABs at z ∼ 0.3, SDSS J0113+0106 (J0113) and SDSS J1155−0147 (J1155), comparable in size and luminosity to 'B1', one of the best-studied LABs at z 2. Our NuSTAR hard X-ray (3-30 keV) observations reveal powerful active galactic nuclei (AGN) with L 2−10 keV = (0.5-3) × 10 44 erg s −1 . J0113 also faded by a factor of ∼ 5 between 2014 and 2016, emphasizing that variable AGN may cause apparent ionization deficits in LABs. Joint spectral analyses including Chandra data constrain column densities of N H = 5.123 cm −2 (J0113) and N H = 6.0. J0113 is likely buried in a torus with a narrow ionization cone, but ionizing radiation is also leaking in other directions as revealed by our Gemini/GMOS 3D spectroscopy. The latter shows a bipolar outflow over 10 kpc, with a peculiar velocity profile that is best explained by AGN flickering. X-ray analysis of J1155 reveals a weakly absorbed AGN that may ionize over a wide solid angle, consistent with our 3D spectra. Extinction corrected [O iii] log-luminosities are high, ∼ 43.6. The velocity dispersions are low, ∼ 100-150 km s −1 , even at the AGN positions. We argue that this is a combination of high extinction hiding the turbulent gas, and previous outflows that have cleared the escape paths for their successors.

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“…It shows that the double peaked frequency profile of the Lyα photon emergent from an optically thick medium generally does not follow the time-independent solutions of the P-F equation (Fang 2009;Roy et al 2009aRoy et al , 2009bRoy et al , 2009cRoy et al , 2010. The solver has also been used to calculate time-dependent features: 1) the timescale of the formation of the W-F effect; 2) the light-curve of a flash source surrounded by optically thick halo; 3) the dependence of the Lyα photon escape coefficient on the redshifts of sources; 4) the effects of dust on the double-peak profile of the emergent Lyα photons (Roy et al 2009a(Roy et al , 2009b(Roy et al , 2009c(Roy et al , 2010Yang et al 2011;Xu et al 2011). These features have not been seen with previous methods.…”

Section: Introductionmentioning

confidence: 99%

“…Monte Carlo (MC) simulations are also popular in solving the transfer of resonant photons (e.g. Loeb & Rybicki 1999;Zheng & Miralda-Escude 2002;Tasitsiomi 2006;Verhamme et al 2006;Laursen & Sommer-Larsen 2007;Pierleoni et al 2009;Xu & Wu 2010;Xu et al 2011). …”

Section: Introductionmentioning

confidence: 99%

Angular Distribution of Ly(alpha) Resonant Photons Emergent from Optically Thick Medium

Yang¹,

Roy²,

Shu³

et al. 2012

Self Cite

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We investigate the angular distribution of Lyα photons transferring in or emergent from an optically thick medium. Since the evolutions of specific intensity I in the frequency space and the angular space are coupled from each other, we first develop the WENO numerical solver in order to find the time-dependent solutions of the integrodifferential equation of I in the space of frequency and angular simultaneously. We show first that the solutions with the Eddington approximation, which assume I to be linearly dependent on the angular variable µ, yield similar frequency profiles of the photon flux as that without the Eddington approximation. However, the solutions of the µ distribution evolution are significantly different from that given by Eddington approximation. First, the angular distribution of I are found to be substantially dependent on the frequency of photons. For photons with the resonant frequency ν 0 , I contains only a linear term of µ. For photons with frequency at the double peaks of the flux, the µ-distribution is highly anisotropic, in which most photons are in the direction of radial forward. Moreover, either at ν 0 or at the double peaks, the µ distributions actually are independent of the initial µ distribution of photons of the source. This is because the photons with frequency either of ν 0 or of the double peaks have undergone the process of forgetting their initial conditions due to the resonant scattering. We also show that the optically thick medium is a collimator of photons at the double peaks. Photons from the double peaks form a forward beam with very small spread angle. TR-2012-049. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S) SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release; distribution unlimited 13. SUPPLEMENTARY NOTES ABSTRACTWe investigate the angular distribution of Lyα photons transferring in or emergent from an optically thick medium. Since the evolutions of specific intensity I in the fre-quency space and the angular space are coupled from each other, we first develop the WENO numerical solver in order to find the time-dependent solutions of the integro-differential equation of I in the space of frequency and angular simultaneously. We show first that the solutions with the Eddington approximation, which assume I to be linearly dependent on the angular variable μ, yield similar frequency profiles of the photon flux as that without the Eddington approximation. However, the solutions of the μ distribution evolution are significantly different from that given by Eddington approximation. First, the angular distribution of I are found to be substantially de-pendent on the frequency of photons. For photons with the resonant frequency ν0, I contains only a linear term of μ. For photons with frequency at the double peaks of the flux, the μ-distribution is highly anisotropic, in which most photons are in the direc-tion of radial forward. Moreover, either ...

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Time-dependent behaviour of Lyman α photon transfer in a high-redshift optically thick medium

Cited by 8 publications

References 46 publications

About AGN ionization echoes, thermal echoes and ionization deficits in low-redshift Lyα blobs

About AGN ionization echoes, thermal echoes and ionization deficits in low-redshift Lyα blobs

NuSTAR Hard X-Ray Data and Gemini 3D Spectra Reveal Powerful AGN and Outflow Histories in Two Low-redshift Lyα Blobs

Angular Distribution of Ly(alpha) Resonant Photons Emergent from Optically Thick Medium

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