J/A+A/689/A109 Quasars as standard candles. VI. (Trefoloni+, 2024)
Quasars as standard candles.
VI. Spectroscopic validation of the cosmological sample.
Trefoloni B., Lusso E., Nardini E., Risaliti G., Marconi A., Bargiacchi G.,
Sacchi A., Pietrini P., Signorini M.
<Astron. Astrophys. 689, A109 (2024)>
=2024A&A...689A.109T 2024A&A...689A.109T (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Spectra, optical ; Spectra, ultraviolet
Keywords: galaxies: active - quasars: general -
quasars: supermassive black holes
Abstract:
A sample of quasars has been recently assembled to investigate the
non-linear relation between their monochromatic luminosities at
2500Å, and 2keV and to exploit quasars as a new class of
'standardized candles'. The use of this technique for cosmological
purposes relies on the non-evolution with redshift of the UV-optical
spectral properties of quasars, as well as on the absence of possible
contaminants such as dust extinction and host galaxy contribution. We
address these possible issues by analysing the spectral properties of
our cosmological quasar sample. We produced composite spectra in
different bins of redshift and accretion parameters (black hole mass,
bolometric luminosity), to investigate any possible evolution of the
spectral properties of the continuum of the composites with these
parameters. We found a remarkable similarity amongst the various
stacked spectra. Apart from the well known evolution of the emission
lines with luminosity (i.e. the Baldwin effect) and black hole mass
(i.e. the virial relation), the overall shape of the continuum,
produced by the accretion disc, does not show any statistically
significant trend with black-hole mass (MBH), bolometric luminosity
(Lbol), or redshift (z). The composite spectrum of our quasar sample
is consistent with negligible levels of both intrinsic reddening (with
a colour excess E(B-V)≲0.01) and host galaxy emission (less than 10%)
in the optical. We tested whether unaccounted dust extinction could
explain the discrepancy between our cosmographic fit of the
Hubble-Lemaitre diagram and the concordance {LAMBDA}CDM model. The
average colour excess required to solve the tension should increase
with redshift up to unphysically high values (E(B-V)~=0.1 at z>3) that
would imply that the intrinsic emission of quasars is much bluer and
more luminous than ever reported in observed spectra. The similarity
of quasar spectra across the parameter space excludes a significant
evolution of the average continuum properties with any of the explored
parameters, confirming the reliability of our sample for cosmological
applications. Lastly, dust reddening cannot account for the observed
tension between the Hubble--Lemaitre diagram of quasars and the
{LAMBDA}CDM model.
Description:
In this sixth paper of the series, we presented a thorough analysis of
the average spectral properties of 2316 sources with available SDSS
data from the sample described in Lusso et al. (2020A&A...642A.150L 2020A&A...642A.150L,
Cat. J/A+A/642/A150). Our main aims were to investigate the possible
evolution of the UV optical properties with redshift, and to study the
possible systematic effects (e.g. host galaxy contamination, dust
extinction) that could undermine the validity of quasars as standard
candles. To this end, we built spectral composites in the parameter
space defined by MBH, Lbol, and redshift to investigate how the
spectral properties of the cosmological sample vary as a function of
the key accretion parameters and cosmic time.
tabled1.dat contains all the average accretion parameters of the bins
in which the parameter space is divided, as well as the spectral
properties of the composites.
spcomp.dat contains the composite spectrum in Fig. 3 of the paper.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tabled1.dat 283 37 *Relevant quantities for each bin of the
parameter space
spcomp.dat 67 4172 Composite spectrum in Fig. 3 of the paper
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Note on tabled1.dat: all the average accretion parameters of the bins in which
the parameter space is divided, as well as the spectral properties of the
composites.
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See also:
J/A+A/642/A150 : Quasars as standard candles. III. (Lusso+, 2020)
J/A+A/663/L7 : Quasars as high-redshift standard candles (Sacchi+, 2022)
Byte-by-byte Description of file: tabled1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- Bin Bin of the parameter space,
denoted as described in Sec. 3.1
5- 7 I3 --- Nobj Number of sources in the bin
9- 26 F18.15 [Msun] logMBH Average mean of the black hole mass of the
sources in the bin
28- 45 F18.16 [Msun] e_logMBH Uncertainty on the mean logarithm of the
black hole mass of the sources in the bin
47- 64 F18.15 [10-7W] logLbol Mean logarithm of the bolometric luminosity
of the sources in the bin
66- 83 F18.16 [10-7W] e_logLbol Uncertainty on the mean logarithm of the
bolometric luminosity of the sources
in the bin
85-103 F19.16 [-] loglEdd Mean logarithm of Eddington ratio of the
sources in the bin
105-122 F18.16 [-] e_loglEdd Uncertainty on the mean logarithm of the
Eddington ratio of the sources in the bin
124-142 F19.16 --- alpha Slope of the continuum of the composite
spectrum, αλ
144-161 F18.16 --- e_alpha Uncertainty on the slope of the continuum of
the composite spectrum
163-180 F18.16 --- F2500 Normalised monochromatic flux at 2500Å of
the composite spectrum
182-202 F21.19 --- e_F2500 Uncertainty on the normalised monochromatic
flux at 2500Å of the composite spectrum
204-222 F19.16 --- dalpha {DELTA}α parameter for each composite
spectrum evaluated as described in Sec. 4.3
224-245 E22.14 --- e_dalpha Uncertainty on the {DELTA}α parameter
for each composite spectrum evaluated
as described in Sec. 4.3
247-264 F18.16 --- gamma Average photometric photon index in the bin
266-283 F18.16 --- e_gamma Uncertainty on the average photometric
photon index in the bin
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Byte-by-byte Description of file: spcomp.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 F18.13 0.1nm lambda Wavelength
20- 40 F21.19 --- NFlux Flux normalised at 2200Å
42- 62 F21.19 --- e_NFlux Uncertainty on the flux normalised at 2200Å
64- 67 I4 --- Nobj Number of objects per spectral channel
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Acknowledgements:
Bartolomeo Trefoloni, bartolomeo.trefoloni(at)unifi.it
References:
Lusso & Risaliti, Paper I 2017A&A...602A..79L 2017A&A...602A..79L
Salvestrini et al., Paper II 2019A&A...631A.120S 2019A&A...631A.120S
Lusso et al., Paper III 2020A&A...642A.150L 2020A&A...642A.150L, Cat. J/A+A/642/A150
Signorini et al., Paper IV 2023A&A...676A.143S 2023A&A...676A.143S
Signorini et al., Paper V 2024A&A...687A..32S 2024A&A...687A..32S
(End) Patricia Vannier [CDS] 21-Aug-2024