J/ApJ/923/223 VLT/X-SHOOTER & Keck/ESI spectra of z∼5 QSOs (Zhu+, 2021)
Chasing the tail of cosmic reionization with dark gap statistics in the
Lyα forest over 5<z<6.
Zhu Y., Becker G.D., Bosman S.E.I., Keating L.C., Christenson H.M.,
Banados E., Bian F., Davies F.B., D'Odorico V., Eilers A.-C., Fan X.,
Haehnelt M.G., Kulkarni G., Pallottini A., Qin Y., Wang F., Yang J.
<Astrophys. J., 923, 223 (2021)>
=2021ApJ...923..223Z 2021ApJ...923..223Z
ADC_Keywords: Spectra, ultraviolet; QSOs; Redshifts; Optical;
Intergalactic medium
Keywords: Reionization ; Intergalactic medium ;
Quasar absorption line spectroscopy ; High-redshift galaxies
Abstract:
We present a new investigation of the intergalactic medium (IGM) near
the end of reionization using "dark gaps" in the Lyα forest.
Using spectra of 55 QSOs at zem>5.5, including new data from the
XQR-30 VLT Large Programme, we identify gaps in the Lyα forest
where the transmission averaged over 1 comoving h-1 Mpc bins falls
below 5%. Nine ultralong (L>80h-1Mpc) dark gaps are identified at
z<6. In addition, we quantify the fraction of QSO spectra exhibiting
gaps longer than 30h-1Mpc, F30, as a function of redshift. We
measure F30∼0.9, 0.6, and 0.15 at z=6.0, 5.8, and 5.6, respectively,
with the last of these long dark gaps persisting down to z∼5.3.
Comparing our results with predictions from hydrodynamical
simulations, we find that the data are consistent with models wherein
reionization extends significantly below redshift six. Models wherein
the IGM is essentially fully reionized that retain large-scale
fluctuations in the ionizing UV background at z≲6 are also
potentially consistent with the data. Overall, our results suggest
that signatures of reionization in the form of islands of neutral
hydrogen and/or large-scale fluctuations in the ionizing background
remain present in the IGM until at least z∼5.3.
Description:
This study is based on spectra of 55 QSOs at 5.5≲zem≲6.5 taken
with the X-Shooter spectrograph on the Very Large Telescope (VLT) and
the Echellette Spectrograph and Imager (ESI) on Keck. Of these,
23 X-Shooter spectra are from the XQR-30 VLT Large Programme
(D'Odorico+ arXiv:2305.05053).
In addition, we use 30 spectra reduced from archival X-Shooter and ESI
data, of which 27 are from the sample of Becker+ (2019, J/ApJ/883/163).
Recent deep (20hr) X-Shooter observations (PI: Fuyan Bian) of the
lensed z=6.5 QSO J0439+1634 are also included in the dark gaps
statistics.
Finally, we acquired a deep (7hr) ESI spectrum of SDSS J1250+3130.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 64 55 QSO spectra used in this work
table2.dat 85 1329 Properties of dark gaps
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See also:
J/ApJ/863/92 : LAE cand. at z∼5.7 in QSO J0148+0600 field (Becker+, 2018)
J/ApJ/883/163 : OI abs. search in Keck & VLT sp. of 199 QSOs (Becker+, 2019)
J/MNRAS/488/1035 : AGN UV luminosity function (Kulkarni+, 2019)
J/ApJ/873/35 : Gemini GNIRS NIR sp. of 50 QSOs at z≳5.7 (Shen+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Seq [1/55] Runing sequence number
4- 25 A22 --- QSO QSO designation
27- 32 F6.4 --- zem [5.5/6.6] QSO redshift
34 A1 --- r_zem zem reference (1)
36- 50 A15 --- Source Source of the spectrum used for dark gap
statistics (2)
52- 60 A9 --- Inst Instrument ("X-Shooter" or "ESI")
62- 64 I3 --- S/N [21/224] Continuum signal-to-noise ratio (3)
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Note (1): Redshift lines and their references as follows:
a = [CII]158um: Banados+ (2015ApJ...805L...8B 2015ApJ...805L...8B)
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)
h = [CII]158um: Maiolino+ (2005A&A...440L..51M 2005A&A...440L..51M)
i = [CII]158um: Mazzucchelli+ (2017ApJ...849...91M 2017ApJ...849...91M)
j = MgII: Shen+ (2019, J/ApJ/873/35)
k = [CII]158um: Venemans+ (2020ApJ...904..130V 2020ApJ...904..130V)
l = [CII]158um: Wang+ (2019ApJ...880....2W 2019ApJ...880....2W)
m = [CII]158um: Wang+ (2021ApJ...908...53W 2021ApJ...908...53W)
n = CO: Wang+ (2010ApJ...714..699W 2010ApJ...714..699W)
o = [CII]158um: Wang+ (2013ApJ...773...44W 2013ApJ...773...44W)
p = [CII]158um: Yang+ (2019ApJ...880....2W 2019ApJ...880....2W)
q = Apparent start of the Lyα forest: this work
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);
new observation = spectra from new observations;
archival (B19) = archival spectra used and reduced in B19
(Becker+ 2019, J/ApJ/883/163);
other archival = spectra from the public archives but not included in
B19.
Note (3): The estimated signal-to-noise ratios, which is calculated as the
median ratio of unabsorbed QSO continuum to noise per 30km/s near 1285Å
in the rest frame.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Seq [1/1329] Index of the dark gap
6- 27 A22 --- QSO QSO name
30- 34 F5.3 --- zBlue [4.6/6.5] Redshift of the dark gap's blue
end
36 A1 --- f_zBlue Flag on zBlue (1)
38- 42 F5.3 --- zRed [4.6/6.5] Redshift of the dark gap's red
end
44 A1 --- f_zRed Flag on zRed (1)
46- 47 A2 --- l_L [≥ ] Limit flag on L
48- 50 I3 1.475Mpc L [1/169] Dark gap length in comoving Mpc/h
52 A1 --- f_L Flag on L (1)
54- 55 A2 --- l_TauEff [≥ ] Limit flag on TauEff
56- 60 F5.3 --- TauEff [1.4/8.7] Effective opacity of the dark
gap
62- 66 F5.3 --- e_TauEff [0.01/0.5]? Uncertainty in TauEff
68- 85 A18 --- zMetalAbs Redshift(s) of metal absorber(s) in the
dark gap, if any
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Note (1): Flags as follows:
a = Dark gap starting at the blue edge of Lyman-alpha forest.
b = Dark gap ending at the red edge of Lyman-alpha forest.
c = Dark gap completely inside the buffer zone.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 01-Jun-2023