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Register a new userThree Lyman-alpha emitting galaxies within a quasar proximity zone at z=5.8
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Sarah Elena Ivana Bosman
Publication date
2019
fields
Physics
and research's language is
English
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Quasar proximity zones at $z>5.5$ correspond to over-dense and over-ionized environments. Galaxies found inside proximity zones can therefore display features which would otherwise be masked by absorption in the IGM. We demonstrate the utility of this quasar-galaxy synergy by reporting the discovery of the first three `proximate Lyman-$alpha$ emitters (LAEs) within the proximity zone of quasar J0836 at $z=5.802$ (textit{Aerith A, B} and textit{C}). textit{Aerith A}, located behind the quasar with an impact parameter $D_perp = 278$ pkpc, provides the first detection of a Lyman-$alpha$ transverse proximity effect. We model the transmission and show it constrains the onset of J0836s quasar phase to $0.2 text{Myr}<t<20text{Myr}$ in the past. The second object, textit{Aerith B} at a distance $D=750$ pkpc from the quasar, displays a bright, broad double-peaked lal emission line. Based on relations calibrated at $zleq3$, the peak separation implies a low ionizing $f_{text{esc}} lesssim 1%$, the most direct such constraint on a reionization-era galaxy. We fit the Ly-$alpha$ line with an outflowing shell model, finding a completely typical central density $text{log N}_{text{HI}}/text{cm}^{-2} = 19.3_{-0.2}^{+0.8}$, outflow velocity $v=16_{-11}^{+4}$ km s$^{-1}$, and gas temperature $text{log} T/text{K} = 3.8_{-0.7}^{+0.8}$ compared to $2<z<3$ analogue LAEs. Finally, we detect an emission line at $lambda=8177$ AA in object textit{Aerith C} which, if it is lal at $z=5.726$, would correspond closely with the end of the quasars proximity zone ($Delta z<0.02$ from the boundary) and suggests the quasar influences the IGM up to $sim85$ cMpc away, making it the largest quasar proximity zone. Via the analyses conducted here, we illustrate how proximate LAEs offer unique insight into the ionizing properties of both quasars and galaxies during the epoch of reionization.
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Bright quasars, observed when the Universe was less than one billion years old (z>5.5), are known to host massive black holes (~10$^{9}$ M$_{odot}$), and are thought to reside in the center of massive dark matter overdensities. In this picture, overdensities of galaxies are expected around high redshift quasars. However, observations based on the detection of Lyman Break Galaxies (LBGs) around these quasars do not offer a clear picture: this may be due to the uncertain redshift constraints of LBGs, which are selected through broad-band filters only. To circumvent such uncertainties, we here perform a search for Lyman Alpha Emitting galaxies (LAEs) in the field of the quasar PSO J215.1512-16.0417 at z~5.73, through narrow band, deep imaging with FORS2 at the VLT. We study an area of 37 arcmin$^{2}$, i.e. ~206 comoving Mpc$^{2}$ at the redshift of the quasar. We find no evidence for an overdensity of LAEs in the quasar field with respect to blank field studies. Possible explanations for these findings include that our survey volume is too small, or that the strong ionizing radiation from the quasar hinders galaxy formation in its immediate proximity. Another possibility is that these quasars are not situated in the dense environments predicted by some simulations.
Distant luminous quasars provide important information on the growth of the first supermassive black holes, their host galaxies and the epoch of reionization. The identification of quasars is usually performed through detection of their Lyman-$alpha$ line redshifted to $sim$ 0.9 microns at z>6.5. Here, we report the discovery of a very Lyman-$alpha$ luminous quasar, PSO J006.1240+39.2219 at redshift z=6.618, selected based on its red colour and multi-epoch detection of the Lyman-$alpha$ emission in a single near-infrared band. The Lyman-$alpha$-line luminosity of PSO J006.1240+39.2219 is unusually high and estimated to be 0.8$times$10$^{12}$ Solar luminosities (about 3% of the total quasar luminosity). The Lyman-$alpha$ emission of PSO J006.1240+39.2219 shows fast variability on timescales of days in the quasar rest frame, which has never been detected in any of the known high-redshift quasars. The high luminosity of the Lyman-$alpha$ line, its narrow width and fast variability resemble properties of local Narrow-Line Seyfert 1 galaxies which suggests that the quasar is likely at the active phase of the black hole growth accreting close or even beyond the Eddington limit.
We present IRAM PdBI observations of the CO(3-2) and CO(5-4) line transitions from a Ly-alpha blob at z~2.7 in order to investigate the gas kinematics, determine the location of the dominant energy source, and study the physical conditions of the molecular gas. CO line and dust continuum emission are detected at the location of a strong MIPS source that is offset by ~1.5 from the Ly-alpha peak. Neither of these emission components is resolved with the 1.7 beam, showing that the gas and dust are confined to within ~7kpc from this galaxy. No millimeter source is found at the location of the Ly-alpha peak, ruling out a central compact source of star formation as the power source for the Ly-alpha emission. Combined with a spatially-resolved spectrum of Ly-alpha and HeII, we constrain the kinematics of the extended gas using the CO emission as a tracer of the systemic redshift. Near the MIPS source, the Ly-alpha profile is symmetric and its line center agrees with that of CO line, implying that there are no significant bulk flows and that the photo-ionization from the MIPS source might be the dominant source of the Ly-alpha emission. In the region near the Ly-alpha peak, the gas is slowly receding (~100km/s) with respect to the MIPS source, thus making the hyper-/superwind hypothesis unlikely. We find a sub-thermal line ratio between two CO transitions, I_CO(5-4)/I_CO(3-2)=0.97+/-0.21. This line ratio is lower than the average values found in high-z SMGs and QSOs, but consistent with the value found in the Galactic center, suggesting that there is a large reservoir of low-density molecular gas that is spread over the MIPS source and its vicinity.
We present a study of ~100 high redshift (z~2-4) extremely strong damped Lyman-alpha systems (ESDLA, with N(HI)>0.5x10^22 cm^-2) detected in quasar spectra from the Baryon Oscillation Spectroscopic Survey SDSS-III DR11. 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(HI) 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 lines 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 Lya emission with <L>~(0.6+/-0.2)x10^42 erg/s 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). [truncated]
We present the results of a high-spatial-resolution study of the line emission in a sample of z=3.1 Lyman-Alpha-Emitting Galaxies (LAEs) in the Extended Chandra Deep Field-South. Of the eight objects with coverage in our HST/WFPC2 narrow-band imaging, two have clear detections and an additional two are barely detected (~2-sigma). The clear detections are within ~0.5 kpc of the centroid of the corresponding rest-UV continuum source, suggesting that the line-emitting gas and young stars in LAEs are spatially coincident. The brightest object exhibits extended emission with a half-light radius of ~1.5 kpc, but a stack of the remaining LAE surface brightness profiles is consistent with the WFPC2 point spread function. This suggests that the Lyman Alpha emission in these objects originates from a compact (<~2 kpc) region and cannot be significantly more extended than the far-UV continuum emission (<~1 kpc). Comparing our WFPC2 photometry to previous ground-based measurements of their monochromatic fluxes, we find at 95% (99.7%) confidence that we cannot be missing more than 22% (32%) of the Lyman Alpha emission.
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