J/MNRAS/521/289 XQR-30 quasars absorption systems properties (Davies+, 2023)
The XQR-30 metal absorber catalogue: 778 absorption systems spanning
2 ≲ z ≲ 6.5.
Davies R.L., Ryan-Weber E., D'odorico V., Bosman S.E.I., Meyer R.A.,
Becker G.D., Cupani G., Bischetti M., Sebastian A.M., Eilers A.-C.,
Farina E.P., Wang F., Yang J., Zhu Y.
<Mon. Not. R. Astron. Soc. 521, 289-313 (2023)>
=2023MNRAS.521..289D 2023MNRAS.521..289D (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Intergalactic medium ; Spectroscopy ; Molecular data ;
Optical ; Ultraviolet ; Infrared ; Redshifts ; Equivalent widths ;
Velocity dispersion ; References
Keywords: intergalactic medium - quasars: absorption lines - early Universe
Abstract:
Intervening metal absorption lines in the spectra of z ~> 6 quasars
are fundamental probes of the ionization state and chemical
composition of circumgalactic and intergalactic gas near the end of
the reionization epoch. Large absorber samples are required to
robustly measure typical absorber properties and to refine models of
the synthesis, transport, and ionization of metals in the early
Universe. The Ultimate XSHOOTER legacy survey of quasars at
z ∼ 5.8-6.6 (XQR-30) has obtained high signal-to-noise spectra of 30
luminous quasars, nearly quadrupling the existing sample of 12 high
quality z ∼ 6 quasar spectra. We use this unprecedented sample to
construct a catalogue of 778 systems showing absorption in one or more
of Mg II (360 systems), Fe II (184), C II (46), C IV (479), Si IV
(127), and N V (13) which span 2 ≲ z ≲ 6.5. This catalogue
significantly expands on existing samples of z ~> 5 absorbers,
especially for C IV and Si IV which are important probes of the
ionizing photon background at high redshift. The sample is 50 per cent
(90 per cent) complete for rest-frame equivalent widths W ~> 0.03 Å
(0.09 Å). We publicly release the absorber catalogue along with
completeness statistics and a python script to compute the absorption
search path for different ions and redshift ranges. This data set is a
key legacy resource for studies of enriched gas from the era of galaxy
assembly to cosmic noon, and paves the way for even higher redshift
studies with JWST and 30 m-class telescopes.
Description:
High redshift quasars are extremely valuable tools for studying the
properties of the Universe during the later stages of the epoch of
reionization (z ∼ 6). Intervening metal absorption lines in quasar
spectra encode the redshift, chemical content, and ionization state of
gas in and around galaxies along the line of sight. Over the last
decade, the increasing availability of z ~> 6 quasar spectra has
propelled our understanding of the Universe during its
infancy. Precision measurements of absorber properties at z ∼ 6 offer
another independent avenue to probe the reionization history of the
Universe. Finally, higher ionization species such as C IV and
Si IV probe enriched gas in galaxy halos and are therefore a unique
tracer of outflows in the early Universe. The Ultimate XSHOOTER legacy
survey of quasars at z ∼ 5.8-6.6 has obtained 30 high signal-to-noise
(S/N; => 10 per 10 km/s spectral pixel at 1285 Å rest-frame) quasar
spectra with the goal of characterizing the properties of the Universe
during the second half of reionization. This ESO large program
quadruples the existing sample of 12 archival spectra in the same
redshift range observed at comparable S/N and spectral resolution (∼
30 km/s).
The combined sample of 42 quasars (hereafter referred to as the
'enlarged XQR-30' or E-XQR-30 sample) provides the largest homogeneous
collection of high quality quasar spectra in the early Universe. The
catalogue was constructed using a combination of automated line
finding, custom filtering algorithms and visual inspection. The
majority of the spectra were obtained as part of XQR-30 which acquired
deep, medium resolution observations of 30 bright quasars at
5.8 ≲ z ≲ 6.6 using XSHOOTER. The other 12 spectra were sourced from
archival XSHOOTER observations of quasars in the same redshift and
magnitude range that have similar spectral resolution and S/N to the
XQR-30 spectra. The full sample is described in detail in D'Odorico et
al. (2023MNRAS.523.1399D 2023MNRAS.523.1399D). All 42 quasars were targeted based on their
redshift and magnitude, with no prior knowledge of intervening
absorber properties. The spectrum data are extracted with reduction
process is described in Becker et al. (2019ApJ...883..163B 2019ApJ...883..163B, Cat.
J/ApJ/883/163).
When fitting the absorption lines it became apparent that some spectra
have significantly higher spectral resolution than the nominal value.
Concerning redshifts, we adopted the best quasar redshifts that were
available when the construction of the absorption line catalogue
commenced. The redshifts were taken from emission line measurements
where available (primarily [C II] λ158µm as well as CO,
Mg II, and Lyα + N V), or from the apparent start of the
Lyα forest. The tableb1.dat regroups redshifts and spectral
resolutions for the 42 quasars. Next as explained in section 3, the
absorption line catalogue xqr30abs.dat was constructed by performing
an automated search for candidate systems in each spectrum, filtering
the list of candidates using a combination of custom algorithms and
visual inspection, and fitting Voigt profiles to obtain the column
density, Doppler b parameter, equivalent widths and velocity of
individual absorption components. Many of the steps use routines from
astrocook application for identifying and fitting absorption systems
in quasar spectra. We also include Voigt profile fits and continuum
spectra for each 42 quasars. The final catalogue contains a total of
778 systems including 479 C IV absorbers, 360 Mg II absorbers, and
46 C II absorbers .
More, as described in section 3.2, we provide in tableb2.dat the
masked spectral regions used to better identify candidate metal
absorption systems. Also, during section 3.1 Continuum normalization,
a significant fraction of spectra show BAL features when processing of
BAL quasars, we attempt to adjust the continuum fit to follow the BAL
troughs because this increases the probability of recovering
underlying narrow absorption lines, wavelength spectral regions of BAL
signatures are available in tableb4.dat. Finally, as detailled in
section 4.1 Overview of results the movie.mp4 presents a visualisation
of absorber catalogue where each frame adds data for one additional
quasar.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tableb1.dat 47 42 Adopted quasars emission redshifts and spectral
resolutions for the XQR-30 and archival E-XQR-30
xqr30abs.dat 96 5512 The full metal absorber catalog containing
systems propertie for the 42 quasars sample
tableb2.dat 77 26 *Wavelength regions masked when performing the
initial automatic search for absorption systems
tableb4.dat 138 18 Wavelength regions in which BAL Broad Absorption
Line signatures were detected
conti/* . 42 PDF files per quasar showing the flux beginning
at observed wavelength of quasar Lya emission
line, error spectrum, and fitted continuum level
voigt/* . 42 PDF files per quasar showing Voigt profile fits
for each individual absorption systems
movie.mp4 512 405 *This is an animated version of figure 5 of the
section 4 as visualisation of absorber catalogue
--------------------------------------------------------------------------------
Note on tableb2.dat: The wavelength regions listed in this table were manually
masked during the initial system finding due to either strong absorption just
redward of the quasar Lyα emission line preventing the continuum level
from being accurately determined, or significant contamination by skylines or
telluric absorption (see discussion in Section 3.2). No spectral regions
were masked for the 16 quasars not included in this table.
Note on movie.mp4: The first frame shows only absorbers detected in the lowest
redshift quasar, and each subsequent frame adds data for one additional quasar,
sorted in ascending order of redshift.
--------------------------------------------------------------------------------
See also:
J/MNRAS/502/4009 : Sub-damped Lyman α systems in XQ-100 II
(Berg+, 2021)
J/MNRAS/499/5022 : MUSE Analysis of Gas around Galaxies II (Dutta+, 2020)
J/MNRAS/485/1961 : List of 22 MEGAFLOW fields (Zabl+, 2019)
J/MNRAS/462/3285 : XQ-100. X-shooter quasar spectra (Perrotta+, 2016)
J/MNRAS/460/2143 : HI size-mass relation of galaxies (Wang+, 2016)
J/MNRAS/435/1198 : z∼6 QSOs CIV doublet absorption systems (D'Odorico+,2013)
J/ApJ/932/76 : Lyβ dark gaps in z≲6 QSOs spectra (Zhu+, 2022)
J/ApJ/923/223 : VLT/X-SHOOTER & Keck/ESI spectra of z∼5 QSOs (Zhu+, 2021)
J/ApJ/883/163 : OI abs. search in Keck and VLT spectra of 199 QSOs
(Becker+, 2019)
J/ApJ/794/156 : MgII/FeII absorption profile for 0.3<z<1.4 galaxies
(Rubin+, 2014)
J/ApJ/788/119 : Properties of the highly ionized gas of quasars
(Lehner+, 2014)
J/ApJ/761/112 : High-redshift MgII absorption QSOs with FIRE
(Matejek+, 2012)
J/ApJS/227/11 : PS1 z>5.6 quasars follow-up (Banados+, 2016)
J/ApJS/221/2 : Keck+Magellan survey for LLSs. III. (Prochaska+, 2015)
J/other/Nat/605.244 : XQR-30 quasars sample (Bischetti+, 2022)
Byte-by-byte Description of file: tableb1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- QSO Quasar name identifier
17- 22 F6.4 --- z Emission redshift (z)
24- 28 I5 --- Rvis Spectral resolution for VIS 559.5-1024 nm
wavelengths (RVIS)
30- 34 I5 --- Rnir Spectral resolution for NIR 1024-2480 nm
wavelengths (RNIR)
36- 43 A8 --- Sample Archival quasars sample name of XSHOOTER either
XQR-30 or enlarged E-XQR-30
45- 47 A3 --- r_z Literature reference of the redshift z (Ref) (1)
--------------------------------------------------------------------------------
Note (1): Literature references are as follows:
1 = Bosman et al. (2018MNRAS.479.1055B 2018MNRAS.479.1055B)
2 = Wang et al. (2010ApJ...714..699W 2010ApJ...714..699W)
3 = Zhu et al. (2021ApJ...923..223Z 2021ApJ...923..223Z)
4 = D'Odorico et al. (2023MNRAS.523.1399D 2023MNRAS.523.1399D),
5 = Kurk et al. (2007ApJ...669...32K 2007ApJ...669...32K)
6 = Banados et al. (2016ApJS..227...11B 2016ApJS..227...11B, Cat. J/ApJS/227/11)
7 = Becker et al. (2015MNRAS.447.3402B 2015MNRAS.447.3402B)
8 = Decarli et al. (2018ApJ...854...97D 2018ApJ...854...97D)
9 = Wang et al. (2013ApJ...773...44W 2013ApJ...773...44W)
10 = Carnall et al. (2015MNRAS.451L..16C 2015MNRAS.451L..16C)
11 = Carilli et al. (2010ApJ...714..834C 2010ApJ...714..834C)
12 = Eilers et al. (2021ApJ...914...74E 2021ApJ...914...74E)
13 = Wang et al. (2016MNRAS.460.2143W 2016MNRAS.460.2143W, Cat. J/MNRAS/460/2143)
14 = Venemans et al. (2020ApJ...904..130V 2020ApJ...904..130V)
15 = Yang et al. (2019ApJ...880..153Y 2019ApJ...880..153Y)
16 = Reed et al. (2019MNRAS.487.1874R 2019MNRAS.487.1874R)
17 = Banados et al. (2015ApJ...805L...8B 2015ApJ...805L...8B)
18 = Mazzucchelli et al. (2017ApJ...849...91M 2017ApJ...849...91M)
We adopted the best redshift measurements that were available when
commencing construction of the absorption line catalogue. The
redshifts are consistent with those published in D'Odorico et al.
(2023MNRAS.523.1399D 2023MNRAS.523.1399D) to within 300 km/s and these small differences
do not have any significant impact on the final data set. The
spectral resolution values are estimated using seeing measurements
as described in Section 2.2.2.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: xqr30abs.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- QSO Quasar name identifier (QsoID)
17- 18 I2 --- SystID ? System identifier number as described in
sect. 3.7 components are grouped into systems
following a method similar to that described
in D'Odorico et al. (2022MNRAS.512.2389D 2022MNRAS.512.2389D)
(SystemID) (1)
20- 22 A3 --- CompID Absorption component whcih are grouped into
system, CompID consisting of a system number
and a component label (ComponentID) (2)
24- 30 F7.5 --- z Optical-depth-weighted mean redshift systems
or Voigt profile redshift components (z) (3)
32- 41 A10 --- El Ion or species with the associated transition
wavelength in nm (Species)
43- 47 F5.3 0.1nm EW ? Rest frame equivalent width measurement (W)
49- 55 F7.3 0.1nm e_EW ? Error of EW (dW)
57 A1 --- f_EW Flag reported for each transition in each
system (W_flag) (4)
59- 63 F5.2 [cm-2] logN ? Column density measurement (logN)
65- 68 F4.2 [cm-2] e_logN ? Error of logN (dlogN)
70- 71 A2 --- f_logN Flag reported for both systems and individual
components (logN_flag) (5)
73- 75 I3 km/s dv90 ? The velocity interval enclosing 90 per cent
of the absorption optical depth as in sect.
3.8 defined in Prochaska & Wolfe
(1997ApJ...487...73P 1997ApJ...487...73P) (v90)
77- 81 F5.1 km/s b ? The b Doppler parameter measurement of the
absorption (b)
83- 87 F5.1 km/s e_b ? Error of b parameter (db) ?
89- 92 A4 --- Samp Flag of the sample constructed as string flag
of Y or N answer to 4 questions (SampleFlags)
(6)
94 A1 --- Prim Flag indicating whether the system is part of
the primary sample as discussed in section 6.2
(PrimarySample)
96 A1 --- PorI Flag indicating whether the absorption system
is proximate P or intervening I
(ProximateOrIntervening) (7)
--------------------------------------------------------------------------------
Note (1): For each ion in each absorption system, we provide the total log N
and Δv90 as well as the total W of each transition. We also
list the log N, Δv90 and b parameter of each individual Voigt
profile component.
Note (2): As explicited in section 3.6, components with the same ID were fit
using the same z and b parameter.
Note (3): We do not quote errors on the redshifts which are typically on the
order of 10-5.
Note (4): Measurements for ions detected at < 3σ are flagged as upper
limits (U). This quantity is not reported for individual components.
Note (5): Flag indicate upper limits for ions detected at < 3σ, 'U'),
saturated profiles (optical depth τ>2; 'S'), and ions for which
log N had to be fit for different transitions independently ('M';
as seen in Section 3.6).
Note (6): Sample flags indicating whether (a) the system was found by the
automatic line finder (Section 3.2) ?, (b) the system was classified
as real by at least 3/5 expert checkers (Section 3.5)? , (c) the
relevant transitions lie in spectral regions free of significant
sky contamination (Section 3.2)? , and (d) the relevant transitions
lie in regions free of BAL features (Section 4.3)?.
Does the absorption lie outside of masked wavelength regions ?
Does the absorption lie outside of BAL regions ?
Note (7): As seen in section 3.9, proximate (also known as 'associated' or
'intrinsic') absorbers are traditionally defined to lie within
∼ 5000 km/S of the quasar redshift. Due to their close proximity
to the quasar, such absorbers may have different ionization states
or metal abundance patterns to the underlying absorber population.
For this reason, it is important to distinguish between intervening
and proximate absorbers when investigating e.g. the evolution of
absorber properties over cosmic time. We classify all systems that
have velocity offsets between -10000 km/s and +5000 km/S from the
quasar redshift as proximate absorbers. However, we note that the
data published with this paper enable users to calculate the
velocity offset of each absorber and apply a different velocity
threshold if desired.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tableb2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- QSO Quasar name identifier
17- 21 F5.1 nm LyaMin ? Lyα minimum wavelength of the masked
region
23- 27 F5.1 nm LyaMax ? Lyα maximum wavelength of the masked
region
29- 32 I4 nm TellYmin ? Telluric(Y) minimum wavelength of the
masked region
34- 37 I4 nm TelYmax ? Telluric(Y) maximum wavelength of the
masked region
39- 42 I4 nm TelJ-Hmin ? Telluric(J-H) minimum wavelength of the
masked region
44- 47 I4 nm TelJ-Hmax ? Telluric(J-H) maximum wavelength of the
masked region
49- 52 I4 nm TelH-Kmin ? Telluric(H-K) minimum wavelength of the
masked region
54- 57 I4 nm TelH-Kmax ? Telluric(H-K) maximum wavelength of the
masked region
59- 62 I4 nm TelK1min ? First Telluric(K) minimum wavelength of
the masked region
64- 67 I4 nm TelK1max ? First Telluric(K) maximum wavelength of
the masked region
69- 72 I4 nm TelK2min ? Second Telluric(K) minimum wavelength of
the masked region
74- 77 I4 nm TelK2max ? Second Telluric(K) maximum wavelength of
the masked region
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tableb4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- QSO Quasar name identifier
17- 19 A3 --- CIV CIV name ion species
21- 38 F18.13 0.1nm CIVwmin Minimum transition wavelength of the CIV
40- 57 F18.13 0.1nm CIVwmax Maximum transition wavelength of the CIV
59- 62 A4 --- SiIV SiIV name ion species
64- 80 F17.13 0.1nm SiIVwmin ? Minimum transition wavelength of the SiIV
82- 99 F18.13 0.1nm SiIVwmax ? Maximum transition wavelength of the SiIV
101-102 A2 --- NV NV name ion species
104-120 F17.13 0.1nm NVwmin ? Minimum transition wavelength of the NV
122-138 F17.13 0.1nm NVwmax ? Maximum transition wavelength of the NV
--------------------------------------------------------------------------------
History:
From electronic version of the journal
License: CC-BY-4.0
(End) Luc Trabelsi [CDS] 21-May-2026