CONSTRAINTS ON QUASAR LIFETIMES AND BEAMING FROM THE He II Lyα FOREST

Furlanetto, Steven R.; Lidz, Adam

doi:10.1088/0004-637x/735/2/117

Cited by 20 publications

(32 citation statements)

References 43 publications

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“…For the fiducial parameters above, nH,out(R = 100 kpc) = 2 × 10 −4 cm −3 , so reaching a characteristic LLS density of nH ≈ 0.01 cm −3 requires clumping by a factor ∼ 50. The time for gas ejected from the galaxy to travel a distance R is t flow = R/vout ≈ 10 8 yr R 100 kpc v 1, 000 km s −1 −1 , (5) which for the fiducial parameters is comparable to the estimated lifetime of quasars (e.g., Martini 2004;Hopkins et al 2005;Furlanetto & Lidz 2011). Thus, quasars can in principle eject in their halos enough cool gas to explain the LLSs observed around them.…”

Section: Quasar-hosting Halosmentioning

confidence: 97%

Neutral hydrogen in galaxy haloes at the peak of the cosmic star formation history

Faucher-Giguère¹,

Hopkins²,

Kereš³

et al. 2015

Monthly Notices of the Royal Astronomical Society

170

197

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We use high-resolution cosmological zoom-in simulations from the FIRE project to make predictions for the covering fractions of neutral hydrogen around galaxies at z = 2 − 4. These simulations resolve the interstellar medium of galaxies and explicitly implement a comprehensive set of stellar feedback mechanisms. Our simulation sample consists of 16 main halos covering the mass range M h ≈ 10 9 − 6 × 10 12 M at z = 2, including 12 halos in the mass range M h ∼ 10 11 − 10 12 M corresponding to Lyman break galaxies (LBGs). We process our simulations with a ray tracing method to compute the ionization state of the gas. Galactic winds increase the HI covering fractions in galaxy halos by direct ejection of cool gas from galaxies and through interactions with gas inflowing from the intergalactic medium. Our simulations predict HI covering fractions for Lyman limit systems (LLSs) consistent with measurements around z ∼ 2 − 2.5 LBGs; these covering fractions are a factor ∼ 2 higher than our previous calculations without galactic winds. The fractions of HI absorbers arising in inflows and in outflows are on average ∼ 50% but exhibit significant time variability, ranging from ∼ 10% to ∼ 90%. For our most massive halos, we find a factor ∼ 3 deficit in the LLS covering fraction relative to what is measured around quasars at z ∼ 2, suggesting that the presence of a quasar may affect the properties of halo gas on ∼ 100 kpc scales. The predicted covering fractions, which decrease with time, peak at M h ∼ 10 11 − 10 12 M , near the peak of the star formation efficiency in dark matter halos. In our simulations, star formation and galactic outflows are highly time dependent; HI covering fractions are also time variable but less so because they represent averages over large areas.

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Section: Quasar-hosting Halosmentioning

confidence: 97%

Neutral hydrogen in galaxy haloes at the peak of the cosmic star formation history

Faucher-Giguère¹,

Hopkins²,

Kereš³

et al. 2015

Monthly Notices of the Royal Astronomical Society

170

197

View full text Add to dashboard Cite

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“…However, to ionize the gas, the quasar had to emit He iiionizing photons at least for the transverse light crossing time between the foreground quasar and the sightline (e.g. Jakobsen et al 2003;Worseck & Wisotzki 2006;Furlanetto & Lidz 2011). If we assume a simple lightbulb model in which the quasar turns on, shines with constant luminosity for some time and turns off again, it had to shine for at least the light crossing time to allow simultaneous observation of the quasar and the additional Figure 7) while the two others only include quasars above a minimum separation of Dprop > 15 Mly and > 25 Mly.…”

Section: Constraining the Quasar Episodic Lifetime Withmentioning

confidence: 99%

“…Since quasar orientation is random and only constrained to be unobscured towards Earth, one can in any case only expect a probabilistic answer (see e.g. Furlanetto & Lidz 2011). Determining how realistic it might be that three out of four foreground quasars do not illuminate the background sightline is an important question for future work.…”

Section: Absence Of Transmission Spikes For Largementioning

confidence: 99%

“…Since quasars are bright but rare sources, it is expected that He ii reionization is a very patchy process. The general picture is that quasars create ionized bubbles around them which expand with time, and eventually overlap to form the relatively homogeneous UV background that keeps the IGM in photoionization equi-librium up to the present day (Bolton et al 2006;Furlanetto & Oh 2008;McQuinn 2009;Furlanetto & Dixon 2010;Furlanetto & Lidz 2011;Haardt & Madau 2012;Meiksin & Tittley 2012;Compostella et al 2013Compostella et al , 2014.…”

Section: Introductionmentioning

confidence: 99%

“…Syphers & Shull (2014) claim a transverse proximity effect for another quasar 34 Mly away from the Q 0302−003 sightline, but this case is degenerate with the proximity effect of Q 0302−003 itself. In the limited sample of He ii spectra and foreground quasars Furlanetto & Lidz (2011) see indications against very long (t Q > 10 8 yr) and very short (t Q < 3 × 10 6 yr) quasar lifetimes, by simply counting He ii transmission spikes under the assumption that they are associated with foreground quasars.…”

Section: Introductionmentioning

confidence: 99%

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Statistical Detection of the He ii Transverse Proximity Effect: Evidence for Sustained Quasar Activity for >25 Million Years

Schmidt

Worseck

Prochaska

et al. 2017

ApJ

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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 morphology of quasar-driven He ii reionization. We conduct a comprehensive spectroscopic survey to find z ∼ 3 quasars in the foreground of 22 background quasar sightlines with HST /COS He ii Lyα transmission spectra. With our two-tiered survey strategy, consisting of a deep pencil-beam survey and a shallow wide-field survey, we discover 131 new quasars, which we complement with known SDSS/BOSS quasars in our fields. Using a restricted sample of 66 foreground quasars with inferred He ii photoionization rates greater than the expected UV background at these redshifts (Γ HeII QSO > 5 × 10 −16 s −1 ) we perform the first statistical analysis of the He ii transverse proximity effect. Our results show qualitative evidence for a large object-to-object variance: among the four foreground quasars with the highest Γ HeII QSO only one (previously known) quasar is associated with a significant He ii transmission spike. We perform a stacking analysis to average down these fluctuations, and detect an excess in the average He ii transmission near the foreground quasars at 3σ significance. This statistical evidence for the transverse proximity effect is corroborated by a clear dependence of the signal strength on Γ HeII QSO . Our detection places a purely geometrical lower limit on the quasar lifetime of t Q > 25 Myr. Improved modeling would additionally constrain quasar obscuration and the mean free path of He ii-ionizing photons.

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Evolution of Warped Accretion Disks in Active Galactic Nuclei. I. Roles of Feeding at the Outer Boundaries

Wang

Cheng

et al. 2013

ApJ

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We investigate the alignment processes of spinning black holes and their surrounding warped accretion disks in a frame of two different types of feeding at the outer boundaries. We consider (1) fixed flows in which gas is continually fed with a preferred angular momentum, and (2) free flows in which there is no gas supply and the disks diffuse freely at their outer edges. As expected, we find that for the cases of fixed flows the black hole disk systems always end up aligning on timescales of several 10 6 yr, irrespective of the initial inclinations. If the initial inclination angles are larger than π/2, the black hole accretion transits from retrograde to prograde fashion, and the accreted mass onto the black holes during these two phases is comparable. On the other hand, for the cases of free flows, both alignments and anti-alignments can occur, depending on the initial inclinations and the ratios of the angular momentum of the disks to that of the black holes. In such cases, the disks will be consumed within timescales of 10 6 yr by black holes accreting at the Eddington limit. We propose that there is a close connection between the black hole spin and the lifetime for which the feeding persists, which determines the observable episodic lifetimes of active galactic nuclei. We conclude that careful inclusion of the disk feeding at the outer boundaries is crucial for modeling the evolution of the black hole spin.

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CONSTRAINTS ON QUASAR LIFETIMES AND BEAMING FROM THE He II Lyα FOREST

Cited by 20 publications

References 43 publications

Neutral hydrogen in galaxy haloes at the peak of the cosmic star formation history

Neutral hydrogen in galaxy haloes at the peak of the cosmic star formation history

Statistical Detection of the He ii Transverse Proximity Effect: Evidence for Sustained Quasar Activity for >25 Million Years

Evolution of Warped Accretion Disks in Active Galactic Nuclei. I. Roles of Feeding at the Outer Boundaries

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