Abstract
The Hubble constant (
H
0
) tension between Type Ia supernovae (SNe Ia) and Planck measurements ranges from 4 to 6
σ
. To investigate this tension, we estimate
H
0
in the ΛCDM and
w
0
w
a
...CDM (cold dark matter) models by dividing the Pantheon sample, the largest compilation of SNe Ia, into 3, 4, 20, and 40 bins. We fit the extracted
H
0
values with a function mimicking the redshift evolution:
g
(
z
)
=
H
0
(
z
)
=
H
˜
0
/
(
1
+
z
)
α
, where
α
indicates an evolutionary parameter and
H
˜
0
=
H
0
at
z
= 0. We set the absolute magnitude of SNe Ia so that
H
0
=
73.5
km
s
−
1
Mpc
−
1
, and we fix fiducial values for
Ω
0
m
Λ
CDM
=
0.298
and
Ω
0
m
w
0
w
a
CDM
=
0.308
. We find that
H
0
evolves with redshift, showing a slowly decreasing trend, with
α
coefficients consistent with zero only from 1.2 to 2.0
σ
. Although the
α
coefficients are compatible with zero in 3
σ
, this however may affect cosmological results. We measure locally a variation of
H
0
(
z
=
0
)
−
H
0
(
z
=
1
)
=
0.4
km
s
−
1
Mpc
−
1
in three and four bins. Extrapolating
H
0
(
z
)
to
z
= 1100, the redshift of the last scattering surface, we obtain values of
H
0
compatible in 1
σ
with Planck measurements independent of the cosmological models and number of bins we investigated. Thus, we have reduced the
H
0
tension in the range from 54% to 72% for both cosmological models. If the decreasing trend of
H
0
(
z
)
is real, it could be due to astrophysical selection effects or to modified gravity.
The prompt emission mechanism of gamma-ray bursts (GRB) even after several decades remains a mystery. However, it is believed that correlations between observable GRB properties, given their huge ...luminosity/radiated energy and redshift distribution extending up to at least z 9, are promising possible cosmological tools. They also may help to discriminate among the most plausible theoretical models. Nowadays, the objective is to make GRBs standard candles, similar to supernovae (SNe) Ia, through well-established and robust correlations. However, differently from SNe Ia, GRBs span over several order of magnitude in their energetics, hence they cannot yet be considered standard candles. Additionally, being observed at very large distances, their physical properties are affected by selection biases, the so-called Malmquist bias or Eddington effect. We describe the state of the art on how GRB prompt correlations are corrected for these selection biases to employ them as redshift estimators and cosmological tools. We stress that only after an appropriate evaluation and correction for these effects, GRB correlations can be used to discriminate among the theoretical models of prompt emission, to estimate the cosmological parameters and to serve as distance indicators via redshift estimation.
ABSTRACT
The recent $\sim 4 \, \sigma$ Hubble constant, H0, tension is observed between the value of H0 from the cosmic microwave background (CMB) and Type Ia supernovae (SNe Ia). It is a decade ...since this tension is excruciating the modern astrophysical community. To shed light on this problem is key to consider probes at intermediate redshifts between SNe Ia and CMB and reduce the uncertainty on H0. Toward these goals, we fill the redshift gap by employing gamma-ray bursts (GRBs) and quasars (QSOs), reaching z = 9.4 and z = 7.6, respectively, combined with baryonic acoustic oscillations (BAO), and SNe Ia. To this end, we employ the ‘Dainotti GRB 3D relation’ among the rest-frame end time of the X-ray plateau emission, its corresponding luminosity, and the peak prompt luminosity, and the ‘Risaliti–Lusso’ QSO relation between ultraviolet and X-ray luminosities. We inquire the commonly adopted Gaussianity assumption on GRBs, QSOs, and BAO. With the joint sample, we fit the flat Λ Cold Dark Matter model with both the Gaussian and the newly discovered likelihoods. We also investigate the impact of the calibration assumed for Pantheon and Pantheon + SNe Ia on this analysis. Remarkably, we show that only GRBs fulfil the Gaussianity assumption. We achieve small uncertainties on the matter-density parameter ΩM and H0. We find H0 values compatible within 2σ with the one from the Tip of the Red Giant Branch. Finally, we show that the cosmological results are heavily biased against the arbitrary calibration choice for SNe Ia.
ABSTRACT
Gamma-ray bursts (GRBs), can be employed as standardized candles, extending the distance ladder beyond Type Ia supernovae (SNe Ia, z = 2.26). We standardize GRBs using the three-dimensional ...(3D) Fundamental Plane relation (the Dainotti relation) among the rest-frame end time of the X-ray plateau emission, its corresponding luminosity, and the peak prompt luminosity. Combining SNe Ia and GRBs, we constrain ΩM = 0.299 ± 0.009 assuming a flat Λ cold dark matter (ΛCDM) cosmology with and without correcting GRBs for selection biases and redshift evolution. Using a 3D optical Dainotti correlation, we find this sample is as efficacious in the determination of ΩM as the X-ray sample. We trimmed our GRB samples to achieve tighter planes to simulate additional GRBs. We determined how many GRBs are needed as stand-alone probes to achieve a comparable precision on ΩM to the one obtained by SNe Ia only. We reach the same error measurements derived using SNe Ia in 2011 and 2014 with 142 and 284 simulated optical GRBs, respectively, considering the error bars on the variables halved. These error limits will be reached in 2038 and in 2047, respectively. Using a doubled sample (obtained by future machine learning approaches allowing a light-curve reconstruction and the estimates of GRB redshifts when z is unknown) compared to the current sample, with error bars halved we will reach the same precision as SNe Ia in 2011 and 2014, now and in 2026, respectively. If we consider the current SNe precision, this will be reached with 390 optical GRBs by 2054.
To find out the astrophysical processes responsible for gamma-ray burst (GRB), it is crucial to discover and understand the relations between their observational properties. This work was performed ...in the GRB rest frames using a sample of 62 long Swift GRBs with known redshifts. Following the earlier analysis of the correlation between afterglow luminosity (L*a) and break time (T*a), we extend it to correlations between the afterglow and the prompt emission GRB physical parameters. We find a tight physical scaling between the mentioned afterglow luminosity L*a and the prompt emission mean luminosity 〈L*p〉45≡E
iso/T*45. The distribution, with the Spearman correlation coefficient reaching 0.95 for the most accurately fitted subsample, scales approximately as L*a∝〈L*p〉0.7
45. We have also analysed correlations of L*a with several prompt emission parameters, including the isotropic energy E
iso and the peak energy in the νF
ν spectrum, E
peak. As a result, we obtain significant correlations also between these quantities, discovering that the highest correlated GRB subsample in the afterglow analysis leads also to the highest prompt-afterglow correlations. Such events can be considered to form a sample of standard GRBs for astrophysics and cosmology.
Abstract
Gamma-ray Bursts (GRBs) are the most explosive phenomena in the universe after the big bang. A large fraction of GRB lightcurves (LCs) shows X-ray plateaus. We perform the most comprehensive ...analysis of all GRBs (with known and unknown redshifts) with plateau emission observed by The Neil Gehrels Swift Observatory from its launch until 2019 August. We fit 455 LCs showing a plateau and explore whether these LCs follow closure relations, relations between the temporal and spectral indices of the afterglow, corresponding to two distinct astrophysical environments and cooling regimes within the external forward shock (ES) model, and find that the ES model works for the majority of cases. The most favored environments are a constant-density interstellar or wind medium with slow cooling. We also confirm the existence of the fundamental plane relation between the rest-frame time and luminosity at the end of the plateau emission and the peak prompt luminosity for this enlarged sample, and test this relation on groups corresponding to the astrophysical environments of our known redshift sample. The plane becomes a crucial discriminant corresponding to these environments in terms of the best-fitting parameters and dispersions. Most GRBs for which the closure relations are fulfilled with respect to astrophysical environments have an intrinsic scatter
σ
compatible within 1
σ
of that of the “Gold” GRBs, a subset of long GRBs with relatively flat plateaus. We also find that GRBs satisfying closure relations indicating a fast cooling regime have a lower
σ
than ever previously found in literature.
Abstract
Currently, the Λ cold dark matter model, which relies on the existence of cold dark matter and a cosmological constant Λ, best describes the universe. However, we lack information in the ...high-redshift (
z
) region between Type Ia supernovae (SNe Ia; up to
z
= 2.26) and the cosmic microwave background (
z
= 1100), an interval crucial to test cosmological models and their possible evolution. We have defined a sample of 983 quasars up to
z
= 7.54 with a reduced intrinsic dispersion
δ
= 0.007, which determines the matter density parameter Ω
M
with the same precision of SNe Ia. Although previous analysis have used quasars as cosmological tools, this is the first time that high-redshift sources, in this case quasars, as standalone cosmological probes yield such tight constraints on Ω
M
. Our results show the importance of correcting cosmological relationships for selection biases and redshift evolution and how the choice of a golden sample reduces considerably the intrinsic scatter. This proves the reliability of quasars as standard cosmological candles.
Abstract
Originating from neutron star–neutron star or neutron star–black hole mergers, short gamma-ray bursts (SGRBs) are the first electromagnetic emitters associated with gravitational waves ...(GWs). This association makes the determination of SGRB formation rate (FR) a critical issue. We determine the true SGRB FR and its relation to the cosmic star formation rate (SFR). This can help in determining the expected GW rate involving small mass mergers. We present nonparametric methods for the determination of the evolutions of the luminosity function (LF) and the FR using SGRBs observed by Swift, without any assumptions. These are powerful tools for small samples, such as our sample of 68 SGRBs. We combine SGRBs with and without extended emission (SEE), assuming that both descend from the same progenitor. To overcome the incompleteness introduced by redshift measurements we use the Kolmogorov–Smirnov (KS) test to find flux thresholds yielding a sample of sources with a redshift drawn from the parent sample including all sources. Using two subsamples of SGRBs with flux limits of 4.57 × 10
−7
and 2.15 × 10
−7
erg cm
−2
s
−1
with respective KS
p
= (1, 0.9), we find a 3
σ
evidence for luminosity evolution (LE), a broken power-law LF with significant steepening at
L
∼ 10
50
erg s
−1
, and an FR evolution that decreases monotonically with redshift (independent of LE and the thresholds). Thus, SGRBs may have been more luminous in the past with an FR delayed relative to the SFR as expected in the merger scenario.
ABSTRACT
Cosmological models and their corresponding parameters are widely debated because of the current discrepancy between the results of the Hubble constant, H0, obtained by SNe Ia, and the ...Planck data from the cosmic microwave background radiation. Thus, considering high redshift probes like gamma-ray bursts (GRBs) is a necessary step. However, using GRB correlations between their physical features to infer cosmological parameters is difficult because GRB luminosities span several orders of magnitude. In our work, we use a three-dimensional relation between the peak prompt luminosity, the rest-frame time at the end of the X-ray plateau, and its corresponding luminosity in X-rays: the so-called 3D Dainotti fundamental plane relation. We correct this relation by considering the selection and evolutionary effects with a reliable statistical method, obtaining a lower central value for the intrinsic scatter, σint = 0.18 ± 0.07 (47.1 per cent) compared to previous results, when we adopt a particular set of GRBs with well-defined morphological features, called the platinum sample. We have used the GRB fundamental plane relation alone with both Gaussian and uniform priors on cosmological parameters and in combination with SNe Ia and BAO measurements to infer cosmological parameters like H0, the matter density in the universe (ΩM), and the dark energy parameter w for a wCDM model. Our results are consistent with the parameters given by the Lambda cold dark matter model but with the advantage of using cosmological probes detected up to z = 5, much larger than the one observed for the furthest SNe Ia.
PDF
