J/ApJ/932/76 Lyβ dark gaps in z≲6 QSOs spectra (Zhu+, 2022)
Long dark gaps in the Lyβ forest at z<6: evidence of ultra-late
reionization from XQR-30 spectra.
Zhu Y., Becker G.D., Bosman S.E.I., Keating L.C., D'Odorico V.,
Davies R.L., Christenson H.M., Banados E., Bian F., Bischetti M., Chen H.,
Davies F.B., Eilers A.-C., Fan X., Gaikwad P., Greig B., Haehnelt M.G.,
Kulkarni G., Lai S., Pallottini A., Qin Y., Ryan-Weber E.V., Walter F.,
Wang F., Yang J.
<Astrophys. J., 932, 76 (2022)>
=2022ApJ...932...76Z 2022ApJ...932...76Z
ADC_Keywords: Intergalactic medium; QSOs; Redshifts; Spectra, optical;
Spectra, infrared
Keywords: Reionization ; Intergalactic medium ;
Quasar absorption line spectroscopy ; High-redshift galaxies
Abstract:
We present a new investigation of the intergalactic medium near
reionization using dark gaps in the Lyβ forest. With its lower
optical depth, Lyβ offers a potentially more sensitive probe to
any remaining neutral gas compared to the commonly used Lyα
line. We identify dark gaps in the Lyβ forest using spectra of
42 QSOs at zem>5.5, including new data from the XQR-30 VLT Large
Programme. Approximately 40% of these QSO spectra exhibit dark gaps
longer than 10h-1Mpc at z∼5.8. By comparing the results to
predictions from simulations, we find that the data are broadly
consistent both with models where fluctuations in the Lyα forest
are caused solely by ionizing ultraviolet background fluctuations and
with models that include large neutral hydrogen patches at z<6 due to
a late end to reionization. Of particular interest is a very long
(L=28h-1Mpc) and dark (τeff≳6) gap persisting down to z∼5.5 in
the Lyβ forest of the z=5.85 QSO PSO J025-11. This gap may
support late reionization models with a volume-weighted average
neutral hydrogen fraction of <xHI≫∼5% by z=5.6. Finally, we infer
constraints on <xHI> over 5.5≲z≲6.0 based on the observed Lyβ
dark gap length distribution and a conservative relationship between
gap length and neutral fraction derived from simulations. We find
<xHI>≤0.05, 0.17, and 0.29 at z∼5.55, 5.75, and 5.95, respectively.
These constraints are consistent with models where reionization ends
significantly later than z=6.
Description:
Our sample includes 42 out of the 43 spectra of QSOs at
5.77≲zem≲6.31 that were used for Paper I (Zhu+ 2021, J/ApJ/923/223;
see also Becker+ 2019, J/ApJ/883/163).
The spectra are taken with the Echellette Spectrograph and Imager
(ESI) on Keck and the X-Shooter spectrograph on the Very Large
Telescope (VLT).
Among these, 19 X-Shooter spectra are from the XQR-30 VLT large
program (D'Odorico+ 2023MNRAS.523.1399D 2023MNRAS.523.1399D).
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
qsos.dat 64 42 List of targets; table added by CDS from
Paper I (Zhu+ 2021, J/ApJ/923/223)
fig3.dat 66 195 Observed Lyβ dark gaps
(Data behind Figure 3)
fig1/* . 42 Individual spectra and continuum fits
(Data behind Figure 1; high-resolution images)
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See also:
J/ApJ/863/92 : LAE cand. at z∼5.7 in the QSOJ0148+0600 field (Becker+, 2018)
J/ApJ/883/163 : OI abs. search in Keck & VLT sp. of 199 QSOs (Becker+, 2019)
J/ApJ/905/51 : X-SHOOTER/ALMA QSOs. I. NIR sp. (Schindler+, 2020)
J/MNRAS/506/4389 : Thermal parameters of the IGM at 2≤z≤4 (Gaikwad+, 2021)
J/ApJ/923/223 : VLT/X-SHOOTER & Keck/ESI spectra of z∼5 QSOs (Zhu+, 2021)
http://xqr30.inaf.it/ : XQR-30 homepage
Byte-by-byte Description of file: qsos.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 22 A22 --- QSO QSO name
24- 29 F6.4 --- zem [5.77/6.31] QSO redshift
31 A1 --- r_zem Reference on zem (1)
33- 47 A15 --- Source Source of the spectrum used for dark gap
statistics (2)
49- 57 A9 --- Inst Instrument ("ESI" or "X-Shooter")
59- 61 I3 --- S/N [21/152] Signal-to-noise ratio
63- 64 I2 --- File Subset number in Figure 1 file names;
column added by CDS
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Note (1): Redshift lines and their references as follows:
b = Apparent start of the Lyα forest: Becker+ (2019, J/ApJ/883/163)
c = CO: Carilli+ (2007ApJ...666L...9C 2007ApJ...666L...9C)
d = [CII]158um: Decarli+ (2018ApJ...854...97D 2018ApJ...854...97D)
e = [CII]158um: Eilers+ (2020ApJ...900...37E 2020ApJ...900...37E)
f = MgII: Jiang+ (2007AJ....134.1150J 2007AJ....134.1150J)
g = MgII: Kurk+ (2007ApJ...669...32K 2007ApJ...669...32K)
j = MgII: Shen+ (2019, J/ApJ/873/35)
k = [CII]158um: Venemans+ (2020ApJ...904..130V 2020ApJ...904..130V)
n = CO: Wang+ (2010ApJ...714..699W 2010ApJ...714..699W)
o = [CII]158um: Wang+ (2013ApJ...773...44W 2013ApJ...773...44W)
q = Apparent start of the Lyα forest (Zhu+ 2021, J/ApJ/923/223)
Note (2): Sources of the spectra are as follows:
XQR-30 = spectra from the XQR-30 program
(D'Odorico+ 2023MNRAS.523.1399D 2023MNRAS.523.1399D); 19 occurrences
new observation = spectra from new observations in Zhu+ 2021, J/ApJ/923/223
(1 occurrence)
archival (B19) = archival spectra used and reduced in B19
(Becker+ 2019, J/ApJ/883/163); 20 occurrences
other archival = spectra from the public archives but not included in B19;
2 occurrences
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Byte-by-byte Description of file: fig3.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Seq [1/195] Index of the dark gap
6- 27 A22 --- QSO QSO name
30- 34 F5.3 --- zBlue [5.44/6.02] Redshift of the dark gap's blue end
36 A1 --- f_zBlue [a] Flag on zBlue (1)
38- 42 F5.3 --- zRed [5.45/6.11] Redshift of the dark gap's red end
44 A1 --- f_zRed [b] Flag on zRed (1)
46- 47 A2 --- l_L [≥] Limit flag on L
48- 49 I2 1.475Mpc L [1/39] Dark gap length in comoving Mpc/h
52 A1 --- f_L [c] Flag on L (1)
54- 55 A2 --- l_TauEff [≥] Limit flag on TauEff
56- 60 F5.3 --- TauEff [3.2/6.8] Effective opacity of the dark gap
62- 66 F5.3 --- e_TauEff [0.1/0.5]? Uncertainty in TauEff
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Note (1): Flag as follows:
a = Dark gap starting at the blue edge of Lyman-beta forest.
b = Dark gap ending at the red edge of Lyman-beta forest.
c = Dark gap completely inside the buffer zone.
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History:
From electronic version of the journal for Data behind Figures 1 and 3.
Table 1 of Paper I. (Zhu+ 2021, J/ApJ/923/223) retrieved from VizieR.
References:
Zhu et al. Paper I. 2021ApJ...923..223Z 2021ApJ...923..223Z Cat. J/ApJ/923/223
D'Odorico et al. XQR-30 sample. 2023MNRAS.523.1399D 2023MNRAS.523.1399D
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 17-Mar-2025