Evidence for overdensity around quasars from the proximity effect

Guimarães, R.; Petitjean, P.; Rollinde, Emmanuel; Carvalho, R. R. de; Djorgovski, S. G.; Srianand, R.; Aghaee, A.; Castro, S.

doi:10.1111/j.1365-2966.2007.11624.x

Cited by 51 publications

(98 citation statements)

References 71 publications

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“…This is to avoid contamination of the study by proximate effects such as the presence of overdensities around quasars (e.g. Rollinde et al 2005;Guimarães et al 2007). From this fit we could identify the candidates with log N(H i) − error ≥ 19.5.…”

Section: Identification Of Damped and Sub-damped Lyman-α Systemsmentioning

confidence: 99%

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Damped and sub-damped Lyman-α absorbers in z > 4 QSOs

Guimarães¹,

Petitjean

Carvalho

et al. 2009

A&A

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We present the results of a survey of damped (DLA, log N(H i) > 20.3) and sub-damped Lyman-α systems (19.5 < log N(H i) < 20.3) at z > 2.55 along the lines-of-sight to 77 quasars with emission redshifts in the range 4 < z em < 6.3. Intermediate resolution (R ∼ 4300) spectra were obtained with the Echellette Spectrograph and Imager (ESI) mounted on the Keck telescope. A total of 100 systems with log N(H i) > 19.5 were detected of which 40 systems are damped Lyman-α systems for an absorption length of ΔX = 378. About half of the lines of sight of this homogeneous survey have never been investigated for DLAs. We study the evolution with redshift of the cosmological density of the neutral gas and find, consistent with previous studies at similar resolution, that Ω DLA,H I decreases at z > 3.5. The overall cosmological evolution of Ω H I shows a peak around this redshift. The H i column density distribution for log N(H i) ≥ 20.3 is fitted, consistent with previous surveys, with a single power-law of index α ∼ −1.8 ± 0.25. This power-law overpredicts data at the high-end and a second, much steeper, power-law (or a gamma function) is needed. There is a flattening of the function at lower H i column densities with an index of α ∼ −1.4 for the column density range log N(H i) = 19.5−21. The fraction of H i mass in sub-DLAs is of the order of 30%. The H i column density distribution does not evolve strongly from z ∼ 2.5 to z ∼ 4.5.

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Section: Identification Of Damped and Sub-damped Lyman-α Systemsmentioning

confidence: 99%

“…The continuum was automatically fitted (Aracil et al 2004;Guimarães et al 2007) and the spectra were normalized. We checked the normalization for all lines-of-sight and manually corrected for local defects especially in the vicinity of the Lyman-α emission lines and when the Lyman-α forest is strongly blended.…”

Section: Observation and Data Reductionmentioning

confidence: 99%

Damped and sub-damped Lyman-α absorbers in z > 4 QSOs

Guimarães¹,

Petitjean

Carvalho

et al. 2009

A&A

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“…Measurements of quasar clustering, which is more pronounced at higher redshifts (Croom et al 2005), indicate that a quasar is likely to be part of a group of galaxies. It has also been shown that an overdensity of neutral gas is present within ∼10 Mpc of the quasar (Guimarães et al 2007;Font-Ribera et al 2013). Not surprisingly, the incidence of DLAs within 3000 km s −1 of the quasar is ∼2-4 times higher than that of intervening DLAs (Ellison et al 2010).…”

Section: The Effect Of Clustering Near Quasarsmentioning

confidence: 99%

A glance at the host galaxy of high-redshift quasars using strong damped Lyman-αsystems as coronagraphs

Finley

Petitjean

Pâris

et al. 2013

A&A

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We searched quasar spectra from the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS) for the rare occurrences where a strong damped Lyman-α absorber (DLA) blocks the Broad Line Region emission from the quasar and acts as a natural coronagraph to reveal narrow Lyα emission from the host galaxy. We define a statistical sample of 31 DLAs in Data Release 9 (DR9) with log N(H i) ≥ 21.3 cm −2 located at less than 1500 km s −1 from the quasar redshift. In 25% (8) of these DLAs, a strong narrow Lyα emission line is observed with flux ∼25 × 10 −17 erg s −1 cm −2 on average. For DLAs without this feature in their troughs, the average 3-σ upper limit is <0.8 × 10 −17 erg s −1 cm −2 . Our statistical sample is nearly 2.5 times larger than the anticipated number of intervening DLAs in DR9 within 1 500 km s −1 of the quasar redshift. We also define a sample of 26 DLAs from DR9 and DR10 with narrow Lyα emission detected and no limit on the H i column density to better characterize properties of the host galaxy emission. Analyzing the statistical sample, we do not find substantial differences in the kinematics, metals, or reddening for the two populations with and without emission detected. The highly symmetric narrow Lyα emission line profile centered in the HI trough indicates that the emitting region is separate from the absorber. The luminosity of the narrow Lyα emission peaks is intermediate between that of Lyα emitters and radio galaxies, implying that the Lyα emission is predominantly due to ionizing radiation from the AGN. Galaxies neighboring the quasar host are likely responsible for the majority (>75%) of these DLAs, with only a minority (<25%) arising from H i clouds located in the AGN host galaxy.

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“…We used a flux-bisecting algorithm to measure the observed emission- Guimarães et al (2007). The method uses the QSO's observed V-magnitude (18.5) and emission-line redshift z em , assumes an intrinsic QSO spectral slope of −0.5 (where F ν ∝ ν α ), and corrects for Galactic extinction using the value E(B − V) = 0.048 found toward Q0841+129 from the maps of Schlegel et al (1998).…”

Section: Emission-line Redshift and Specific Luminosity Of Q0841+129mentioning

confidence: 99%

High-ion absorption in the proximate damped Ly-αsystem toward Q0841+129

Ledoux¹,

Petitjean²,

Srianand³

et al. 2011

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We present VLT/UVES spectroscopy of the quasar Q0841+129, whose spectrum shows a proximate damped Ly-α (PDLA) absorber at z = 2.47621 and a proximate sub-DLA at z = 2.50620, both lying close in redshift to the QSO itself at z em = 2.49510 ± 0.00003. This fortuitous arrangement, with the sub-DLA acting as a filter that hardens the QSO's ionizing radiation field, allows us to model the ionization level in the foreground PDLA, and provides an interesting case-study on the origin of the high-ion absorption lines Si iv, C iv, and O vi in DLAs. The high ions in the PDLA show at least five components spanning a total velocity extent of ≈160 km s −1 , whereas the low ions exist predominantly in a single component spanning just 30 km s −1 . We examine various models for the origin of the high ions. Both photoionization and turbulent mixing layer models are fairly successful at reproducing the observed ionic ratios after correcting for the non-solar relative abundance pattern, though neither model can explain all five components. We show that the turbulent mixing layer model, in which the high ions trace the interfaces between the cool PDLA gas and a hotter phase of shock-heated plasma, can explain the average high-ion ratios measured in a larger sample of 12 DLAs.

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Evidence for overdensity around quasars from the proximity effect

Cited by 51 publications

References 71 publications

Damped and sub-damped Lyman-α absorbers in z > 4 QSOs

Damped and sub-damped Lyman-α absorbers in z > 4 QSOs

A glance at the host galaxy of high-redshift quasars using strong damped Lyman-αsystems as coronagraphs

High-ion absorption in the proximate damped Ly-αsystem toward Q0841+129

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