ABSTRACT
We present the results of a model-independent investigation of the rest-frame UV spectra from a comprehensive sample of 394 quasars in the redshift range 1.5 ≤ z ≤ 7.5. We fit the main broad ...emission lines (BELs) in the rest-frame range 1280 Å ≤ λ ≤ 3000 Å (O i, C ii, Si iv, C iii, C iv, and Mg ii) with a lightly supervised spline fitting technique. Redshifts are derived from the peaks of each fitted BEL and used to compute relative velocity shifts. We show that our method gives unbiased velocity shifts and is insensitive to spectral resolution and instrumental parameters. It is found that the average blueshift of the C iv line with respect to several low-ionization lines in luminosity-matched samples does not significantly evolve over 1.5 ≤ z ≤ 6. However, the average blueshift increases significantly by a factor of ∼2.5 at z ≳ 6. We propose that this redshift evolution can be explained by C iv winds launched perpendicularly to an accretion disc with increased torus opacity at high redshift, coupled with a potential orientation-driven selection bias. Our results open new exciting avenues of investigation into young quasars in the reionization epoch.
ABSTRACT
We report the discovery of a double-peaked Lyman α profile in a galaxy at z = 6.803, A370p_z1, in the parallel Frontier Field of Abell 370. The velocity separation between the blue and red ...peaks of the Lyman α profile ($\Delta v=101_{-19}^{+38} (\pm 48)\, \rm km\, \rm s^{-1}$) suggests an extremely high escape fraction of ionizing photons $\gt 59(51){{\ \rm per\ cent}} (2\sigma)$. The spectral energy distribution indicates a young (50 Myr), star-forming ($12\pm 6 \, \rm {M}_\odot \rm {yr}^{-1}$) galaxy with an IRAC excess implying strong O iii + H β emission. On the basis of the high escape fraction measured, we demonstrate that A370p_z1 was solely capable of creating an ionized bubble sufficiently large to account for the blue component of its Lyman α profile. We discuss whether A370p_z1 may be representative of a larger population of luminous z ≃ 7 double-peaked Lyman α emitting sources with high escape fractions that self-ionized their surroundings without contributions from associated ultraviolet-fainter sources.
Abstract
We present Atacama Large Millimeter/submillimeter Array (ALMA) C
ii
158
μ
m and dust continuum observations of the
z
= 6.79 quasar J0109–3047 at a resolution of 0.″045 (∼300 pc). The dust ...and C
ii
emission are enclosed within a ∼500 pc radius, with the central beam (
r
< 144 pc) accounting for ∼25% (8%) of the total continuum (C
ii
) emission. The far-infrared (FIR) luminosity density increases radially from ∼5 × 10
11
L
⊙
kpc
−2
to a central value of ∼70 × 10
11
L
⊙
kpc
−2
(SFRD ∼50–700
M
⊙
yr
−1
kpc
−2
). The C
ii
kinematics are dispersion dominated with a constant velocity dispersion of 137 ± 6 km s
−1
. The constant dispersion implies that the underlying mass distribution is not centrally peaked, consistent with the expectations of a flat gas mass profile. The lack of an upturn in velocity dispersion within the central beam is inconsistent with a black hole mass greater than
M
BH
< 6.5 × 10
8
M
⊙
(2
σ
level), unless highly fine-tuned changes in the interstellar medium properties conspire to produce a decrease of the gas mass in the central beam comparable to the black hole mass. Our observations therefore imply either that (a) the black hole is less massive than previously measured, or (b) the central peak of the FIR and C
ii
emission are not tracing the location of the black hole, as suggested by the tentative offset between the near-infrared position of the quasar and the ALMA continuum emission.
Abstract
We quantify galaxy overdensities around three high-redshift quasars with known C
ii
158
μ
m
companions: PJ231–20 (
z
= 6.59), PJ308–21 (
z
= 6.24), and J0305–3150 (
z
= 6.61). Recent SCUBA2 ...imaging revealed the presence of 17 submillimeter galaxies (SMGs) with sky separations 0.′7 <
θ
< 2.′4 from these three quasars. We present ALMA Band 6 follow-up observations of these SCUBA2-selected SMGs to confirm their nature and redshift. We also search for continuum-undetected C
ii
158
μ
m
emitters in the ALMA pointings and make use of archival MUSE observations to search for Ly
α
emitters (LAEs) associated with the quasars. While most of the SCUBA2-selected sources are detected with ALMA in the continuum, no C
ii
158
μ
m
line emission could be detected, indicating that they are not at the quasar redshifts. Based on the serendipitous detection of CO 7–6 and C
i
809
μ
m
emission lines, we find that four SMGs in the field of PJ231–20 are at
z
∼ 2.4, which is coincident with the redshift of an Mg
ii
absorber in the quasar rest-frame UV spectrum. We report the discovery of two LAEs within <0.6 cMpc of PJ231–20 at the same redshift, indicating an LAE overdensity around this quasar. Taken together, these observations provide new constraints on the large-scale excess of Ly
α
- and C
ii
158
μ
m
-emitting galaxies around
z
> 6 quasars and suggest that only wide-field observations, such as MUSE, ALMA, or JWST mosaics, can reveal a comprehensive picture of large-scale structure around quasars in the first billion years of the universe.
Abstract
Quasar proximity zones at
correspond to overdense and overionized environments. Galaxies found inside proximity zones can therefore display features that would otherwise be masked by ...absorption in the intergalactic medium. We demonstrate the utility of this quasar-galaxy synergy by reporting the discovery of the first three “proximate Ly
α
emitters” (LAEs) within the proximity zone of quasar J0836+0054 at
z
= 5.795 (Aerith A, B, and C). Aerith A, located behind the quasar with an impact parameter
pkpc, provides the first detection of an Ly
α
transverse proximity effect. We model the transmission and show that it constrains the onset of J0836's quasar phase to
in the past. The second object, Aerith B at a distance
pkpc from the quasar, displays a bright and broad double-peaked Ly
α
emission line. The peak separation implies a low ionizing
. We fit the Ly
α
line with an outflowing shell model, finding a typical central density
, outflow velocity
km s
−1
, and gas temperature
compared to
analog LAEs. We detect object Aerith C via an Ly
α
emission line at
z
= 5.726. This corresponds with the edge of the quasar’s proximity zone (
), suggesting that the proximity zone is truncated by a density fluctuation. Via the analyses conducted here, we illustrate how proximate LAEs offer unique insight into the ionizing properties of both quasars and galaxies during hydrogen reionization.
ABSTRACT
The presence of excess scatter in the Ly-α forest at z ∼ 5.5, together with the existence of sporadic extended opaque Gunn-Peterson troughs, has started to provide robust evidence for a late ...end of hydrogen reionization. However, low data quality and systematic uncertainties complicate the use of Ly-α transmission as a precision probe of reionization’s end stages. In this paper, we assemble a sample of 67 quasar sightlines at z > 5.5 with high signal-to-noise ratios of >10 per ≤15 km s−1 spectral pixel, relying largely on the new XQR-30 quasar sample. XQR-30 is a large program on VLT/X-Shooter which obtained deep (SNR > 20 per pixel) spectra of 30 quasars at z > 5.7. We carefully account for systematics in continuum reconstruction, instrumentation, and contamination by damped Ly-α systems. We present improved measurements of the mean Ly-α transmission over 4.9 < z < 6.1. Using all known systematics in a forward modelling analysis, we find excellent agreement between the observed Ly-α transmission distributions and the homogeneous-UVB simulations Sherwood and Nyx up to z ≤ 5.2 (<1σ), and mild tension (∼2.5σ) at z = 5.3. Homogeneous UVB models are ruled out by excess Ly-α transmission scatter at z ≥ 5.4 with high confidence (>3.5σ). Our results indicate that reionization-related fluctuations, whether in the UVB, residual neutral hydrogen fraction, and/or IGM temperature, persist in the intergalactic medium until at least z = 5.3 (t = 1.1 Gyr after the big bang). This is further evidence for a late end to reionization.
We report new Northern Extended Millimeter Array observations of the C ii158 μm, N ii205 μm, and O i146 μm atomic fine structure lines (FSLs) and dust continuum emission of J1148+5251, a z = 6.42 ...quasar, which probe the physical properties of its interstellar medium (ISM). The radially averaged C ii158 μm and dust continuum emission have similar extensions (up to $\theta ={2.51}_{-0.25}^{+0.46}\ \mathrm{arcsec}$, corresponding to $r={9.8}_{-2.1}^{+3.3}\ \mathrm{kpc}$, accounting for beam convolution), confirming that J1148+5251 is the quasar with the largest C ii158 μm-emitting reservoir known at these epochs. Moreover, if the C ii158 μm emission is examined only along its NE–SW axis, a significant excess (>5.8σ) of C ii158 μm emission (with respect to the dust) is detected. The new wide-bandwidth observations enable us to accurately constrain the continuum emission, and do not statistically require the presence of broad C ii158 μm line wings that were reported in previous studies. We also report the first detection of the O i146 μm and (tentatively) N ii205 μm emission lines in J1148+5251. Using FSL ratios of the C ii158 μm, N ii205 μm, O i146 μm, and previously measured C i369 μm emission lines, we show that J1148+5251 has similar ISM conditions compared to lower-redshift (ultra)luminous infrared galaxies. CLOUDY modeling of the FSL ratios excludes X-ray-dominated regions and favors photodissociation regions as the origin of the FSL emission. We find that a high radiation field (103.5–4.5 G0), a high gas density (n ≃ 103.5–4.5 cm−3), and an H i column density of 1023 cm−2 reproduce the observed FSL ratios well.
ABSTRACT
We present improved results of the measurement of the correlation between galaxies and the intergalactic medium transmission at the end of reionization. We have gathered a sample of 13 ...spectroscopically confirmed Lyman-break galaxies (LBGs) and 21 Lyman-α emitters (LAEs) at angular separations 20 arcsec ≲ θ ≲ 10 arcmin (∼0.1–4 pMpc at z ∼ 6) from the sightlines to eight background z ≳ 6 quasars. We report for the first time the detection of an excess of Lyman-α transmission spikes at ∼10–60 cMpc from LAEs (3.2σ) and LBGs (1.9σ). We interpret the data with an improved model of the galaxy–Lyman-α transmission and two-point cross-correlations, which includes the enhanced photoionization due to clustered faint sources, enhanced gas densities around the central bright objects and spatial variations of the mean free path. The observed LAE(LBG)–Lyman-α transmission spike two-point cross-correlation function (2PCCF) constrains the luminosity-averaged escape fraction of all galaxies contributing to reionization to $\langle f_{\rm esc} \rangle _{M_{\rm UV}\lt -12} = 0.14_{-0.05}^{+0.28}\, (0.23_{-0.12}^{+0.46})$. We investigate if the 2PCCF measurement can determine whether bright or faint galaxies are the dominant contributors to reionization. Our results show that a contribution from faint galaxies ($M_{\rm UV} \gt -20 \, (2\sigma)$) is necessary to reproduce the observed 2PCCF and that reionization might be driven by different sub-populations around LBGs and LAEs at z ∼ 6.
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