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

Mon. Not. R. Astron. Soc.

et al. 2015

We report long-slit spectroscopic observations of the quasar SDSS J082303.22+052907.6 (z CIV ∼3.1875), whose Broad Line Region (BLR) is partly eclipsed by a strong damped Lyman-α (DLA; logN (HI)=21.7) cloud. This allows us to study the Narrow Line Region (NLR) of the quasar and the Lyman-α emission from the host galaxy. Using cloudy models that explain the presence of strong NV and PV absorption together with the detection of SiII * and OI * * absorption in the DLA, we show that the density and the distance of the cloud to the quasar are in the ranges 180 < n H < 710 cm −3 and 580 > r 0 >230 pc, respectively. Sizes of the neutral(∼2-9pc) and highly ionized phases (∼3-80pc) are consistent with the partial coverage of the CIV broad line region by the CIV absorption from the DLA (covering factor of ∼0.85). We show that the residuals are consistent with emission from the NLR with CIV/Lyman-α ratios varying from 0 to 0.29 through the profile. Remarkably, we detect extended Lyman-α emission up to 25kpc to the North and West directions and 15kpc to the South and East. We interpret the emission as the superposition of strong emission in the plane of the galaxy up to 10kpc with emission in a wind of projected velocity ∼500km s −1 which is seen up to 25kpc. The low metallicity of the DLA (0.27 solar) argues for at least part of this gas being in-falling towards the AGN and possibly being located where accretion from cold streams ends up.

Section: Elemental Abundancesmentioning

confidence: 76%

Section: Discussionmentioning

confidence: 99%

Section: Qso Blr Lyman-α Emission and Covering Factormentioning

confidence: 99%

Section: Concluding Remarkmentioning

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Section: Introductionmentioning

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See 3 more Smart Citations

A coronagraphic absorbing cloud reveals the narrow-line region and extended Lyman α emission of QSO J0823+0529

Fathivavsari

Mon. Not. R. Astron. Soc.

et al. 2015

A connection between extremely strong damped Lyman-αsystems and Lyman-αemitting galaxies at small impact parameters

Pâris

et al. 2014

A&A

107

We present a study of ∼100 high redshift (z ∼ 2−4) extremely strong damped Lyman-α systems (ESDLA, with N(H i) ≥ 0.5 × 10 22 cm −2 ) detected in quasar spectra from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey (SDSS-III) Data Release 11. We study the neutral hydrogen, metal, and dust content of this elusive population of absorbers and confirm our previous finding that the high column density end of the N(H i) frequency distribution has a relatively shallow slope with power-law index −3.6, similar to what is seen from 21-cm maps in nearby galaxies. The stacked absorption spectrum indicates a typical metallicity ∼1/20th solar, similar to the mean metallicity of the overall DLA population. The relatively small velocity extent of the low-ionisation lines suggests that ESDLAs do not arise from large-scale flows of neutral gas. The high column densities involved are in turn more similar to what is seen in DLAs associated with gamma-ray burst afterglows (GRB-DLAs), which are known to occur close to star-forming regions. This indicates that ESDLAs arise from a line of sight passing at very small impact parameters from the host galaxy, as observed in nearby galaxies. This is also supported by simple theoretical considerations and recent high-z hydrodynamical simulations. We strongly substantiate this picture by the first statistical detection of Ly α emission with L ESDLA (Ly α) (0.6 ± 0.2) × 10 42 erg s −1 in the core of ESDLAs (corresponding to about 0.1 L at z ∼ 2−3), obtained through stacking the fibre spectra (of radius 1 corresponding to ∼8 kpc at z ∼ 2.5). Statistical errors on the Ly α luminosity are of the order of 0.1 × 10 42 erg s −1 but we caution that the measured Ly α luminosity may be overestimated by ∼35% due to sky light residuals and/or FUV emission from the quasar host and that we have neglected flux-calibration uncertainties. We estimate a more conservative uncertainty of 0.2 × 10 42 erg s −1 . The properties of the Ly α line (luminosity distribution, velocity width and velocity offset compared to systemic redshift) are very similar to that of the population of Lyman-α emitting galaxies (LAEs) with L LAE (Ly α) ≥ 10 41 erg s −1 detected in long-slit spectroscopy or narrow-band imaging surveys. By matching the incidence of ESDLAs with that of the LAEs population, we estimate the high column density gas radius to be about r gas = 2.5 kpc, i.e., significantly smaller than the radius corresponding to the BOSS fibre aperture, making fibre losses likely negligible. Finally, the average measured Ly α luminosity indicates a star-formation rate consistent with the Schmidt-Kennicutt law, SFR (M yr −1 ) ≈ 0.6/ f esc , where f esc < 1 is the Ly α escape fraction. Assuming the typical escape fraction of LAEs, f esc ∼ 0.3, the Schmidt-Kennicutt law implies a galaxy radius of about r gal ≈ 2.5 kpc. Finally, we note that possible overestimation of the Ly α emission would result in both smaller r gas and r gal . Our results support a close association between LAEs and stro...

A ~6 Mpc overdensity atz≃ 2.7 detected along a pair of quasar sight lines: filament or protocluster?

Finley

et al. 2014

A&A

Self Cite

Simulations predict that gas in the intergalactic medium (IGM) is distributed in filamentary structures that connect dense galaxy clusters and form the cosmic web. These structures of predominantly ionized hydrogen are difficult to observe directly due to their lack of emitting regions. We serendipitously detected an overdensity of log N(H i) > 18.0 absorbers at z 2.69 along the lines of sight toward a pair of background quasars. Three main absorption regions spanning ∼2000 km s −1 (corresponding to 6.4 h 70 −1 Mpc proper) are coincident in the two lines of sight, which are separated by ∼90 h 70 −1 kpc transverse proper distance. Two regions have [Fe/H] < −1.9 and correspond to mild overdensities in the IGM gas. The third region is a sub-DLA with [Fe/H] = −1.1 that is probably associated with a galaxy. We discuss the possibility that the lines of sight probe along the length of a filament or intercept a galaxy protocluster.