J/ApJ/852/22 Lyα forest power spectrum at 1.8≤z≤3.4 (Walther+, 2018)
A new precision measurement of the small-scale line-of-sight power spectrum of
the Lyα forest.
Walther M., Hennawi J.F., Hiss H., Onorbe J., Lee K.-G., Rorai A.,
O'Meara J.
<Astrophys. J., 852, 22 (2018)>
=2018ApJ...852...22W 2018ApJ...852...22W
ADC_Keywords: QSOs ; Spectra, optical ; Redshifts ; Intergalactic medium
Keywords: cosmology: observations ; dark ages, reionization, first stars ;
intergalactic medium ; quasars: absorption lines
Abstract:
We present a new measurement of the Lyα forest power spectrum at
1.8<z<3.4 using 74 Keck/HIRES and VLT/UVES high-resolution,
high-signal-to-noise-ratio quasar spectra. We developed a custom
pipeline to measure the power spectrum and its uncertainty, which
fully accounts for finite resolution and noise and corrects for the
bias induced by masking missing data, damped Lyα absorption
systems, and metal absorption lines. Our measurement results in
unprecedented precision on the small-scale modes k>0.02s/km,
inaccessible to previous SDSS/BOSS analyses. It is well known that
these high-k modes are highly sensitive to the thermal state of the
intergalactic medium, but contamination by narrow metal lines is a
significant concern. We quantify the effect of metals on the small-
scale power and find a modest effect on modes with k<0.1s/km. As a
result, by masking metals and restricting to k<0.1s/km, their impact
is completely mitigated. We present an end-to-end Bayesian
forward-modeling framework whereby mock spectra with the same noise,
resolution, and masking as our data are generated from Lyα
forest simulations. These mock spectra are used to build a custom
emulator, enabling us to interpolate between a sparse grid of models
and perform Markov chain Monte Carlo fits. Our results agree well with
BOSS on scales k<0.02s/km, where the measurements overlap. The
combination of the percent-level low-k precision of BOSS with our
5%-15% high-k measurements results in a powerful new data set for
precisely constraining the thermal history of the intergalactic
medium, cosmological parameters, and the nature of dark matter.
Description:
Our measurement of the power spectrum was performed using 38
high-resolution quasar spectra (see Table 1) from Dall'Aglio+
(2008A&A...491..465D 2008A&A...491..465D) observed with the Ultraviolet and Visual Echelle
Spectrograph (UVES) at the Very Large Telescope (VLT), and 36 spectra
(see Table 2) from the Keck Observatory Database of Ionized Absorption
toward Quasars (KODIAQ) project (Lehner+ 2014, J/ApJ/788/119) observed
with the High Resolution Echelle Spectrometer (HIRES) at Keck. For the
latter, we used the highest S/N (signal-to-noise ratio) part of DR1
(O'Meara+ 2015, J/AJ/150/111) and additional data beyond DR1 (mostly
early reductions of objects in DR2; O'Meara+ 2017, J/AJ/154/114)
reduced in the same way.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 29 38 VLT/UVES spectra from Dall'Aglio+ (2008A&A...491..465D 2008A&A...491..465D)
used for our analysis
table2.dat 29 36 keck/HIRES spectra from KODIAQ (O'Meara+ 2015,
J/AJ/150/111) used for our analysis
table5.dat 35 198 Measured flux power spectrum after masking metals and
removing the window function due to masking
table6.dat 35 198 Measured flux power spectrum without masking of metals
and after removing the window function due to masking
table7.dat 257 198 Correlation matrix for elements the measurement in
Table 5
table8.dat 257 198 Correlation matrix for elements the measurement in
Table 6
--------------------------------------------------------------------------------
See also:
J/ApJ/457/102 : Lya Forest spectra simulation analysis. I. (Dobrzycki+ 1996)
J/ApJS/163/80 : Lyα forest power spectrum from the SDSS (McDonald+, 2006)
J/ApJ/728/23 : GALEX UV-bright high-redshift quasars (Worseck+, 2011)
J/A+A/559/A85 : 1D Lya forest power spectrum (Palanque-Delabrouille+, 2013)
J/ApJ/788/119 : Properties of the highly ionized gas of quasars (Lehner+, 2014)
J/ApJ/803/34 : z∼4-10 galaxies from HST legacy fields (Bouwens+, 2015)
J/ApJ/814/40 : Nearby galaxy filaments with UV obs. (Wakker+, 2015)
J/AJ/150/111 : KODIAQ DR1 (O'Meara+, 2015)
J/MNRAS/448/3167 : z≳5 AGN in Chandra Deep Field-South (Weigel+, 2015)
J/AJ/154/114 : KODIAQ DR2 (O'Meara+, 2017)
J/ApJ/837/106 : UV bckgd photoionization & photoheating rates (Onorbe+, 2017)
http://koa.ipac.caltech.edu/applications/KODIAQ/ : KODIAQ archive home page
Byte-by-byte Description of file: table[12].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- Name Object name
17 A1 --- f_Name [abc] Flag on Name (1)
19- 23 F5.3 --- zQSO [2.1/3.8] Quasar redshift
25- 29 F5.1 --- S/N [24.6/172] Median S/N per 6km/s
--------------------------------------------------------------------------------
Note (1): Flag as follows:
a = Objects are part of KODIAQ DR2, but a pre-DR2 reduction has been used.
b = Objects are not part of KODIAQ DR1 or DR2, but reduced in the same way.
c = Objects are part of KODIAQ DR1, but a pre-DR1 reduction has been used.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table[56].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 F5.3 --- z [1.8/3.4] Redshift
7- 15 E9.3 s/km k [0.002/0.4] Mode
17- 25 E9.3 --- k.P(k)/pi [0.0002/0.2] Power spectrum
27- 35 E9.3 --- e_k.P(k)/pi [3.6e-05/0.03] Statistical uncertainty in kPk/pi
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table[78].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 F5.3 --- z [1.8/3.4] Redshift
7- 15 E9.3 s/km k [0.002/0.4] Mode
17- 26 E10.3 --- R1_j [-0.22/1] Column 1 of the correlation matrix
28- 37 E10.3 --- R2_j [-0.19/1] Column 2 of the correlation matrix
39- 48 E10.3 --- R3_j [-0.2/1] Column 3 of the correlation matrix
50- 59 E10.3 --- R4_j [-0.2/1] Column 4 of the correlation matrix
61- 70 E10.3 --- R5_j [-0.21/1] Column 5 of the correlation matrix
72- 81 E10.3 --- R6_j [-0.22/1] Column 6 of the correlation matrix
83- 92 E10.3 --- R7_j [-0.18/1] Column 7 of the correlation matrix
94-103 E10.3 --- R8_j [-0.16/1] Column 8 of the correlation matrix
105-114 E10.3 --- R9_j [-0.15/1] Column 9 of the correlation matrix
116-125 E10.3 --- R10_j [-0.13/1] Column 10 of the correlation matrix
127-136 E10.3 --- R11_j [-0.13/1] Column 11 of the correlation matrix
138-147 E10.3 --- R12_j [-0.14/1] Column 12 of the correlation matrix
149-158 E10.3 --- R13_j [-0.18/1] Column 13 of the correlation matrix
160-169 E10.3 --- R14_j [-0.19/1] Column 14 of the correlation matrix
171-180 E10.3 --- R15_j [-0.17/1] Column 15 of the correlation matrix
182-191 E10.3 --- R16_j [-0.20/1] Column 16 of the correlation matrix
193-202 E10.3 --- R17_j [-0.22/1] Column 17 of the correlation matrix
204-213 E10.3 --- R18_j [-0.22/1] Column 18 of the correlation matrix
215-224 E10.3 --- R19_j [-0.2/1] Column 19 of the correlation matrix
226-235 E10.3 --- R20_j [-0.14/1] Column 20 of the correlation matrix
237-246 E10.3 --- R21_j [-0.1/1] Column 21 of the correlation matrix
248-257 E10.3 --- R22_j [-0.09/1] Column 22 of the correlation matrix
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 20-Jul-2018