30,255 research outputs found
Gamma-ray bursts, supernovae Ia, and baryon acoustic oscillations: A binned cosmological analysis
No full textAbstract
Cosmological probes at any redshift are necessary to reconstruct consistently the cosmic history. Studying properly the tension on the Hubble constant, H0, obtained by supernovae type Ia (SNe Ia) and the Planck measurements of the cosmic microwave background radiation would require complete samples of distance indicators at any epoch. Gamma-ray bursts (GRBs) are necessary for the aforementioned task because of their huge luminosity that allows us to extend the cosmic ladder to very high redshifts. However, using GRBs alone as standard candles is challenging, because their luminosity varies widely. To this end, we choose a reliable correlation for GRBs with a very small intrinsic scatter: the so-called fundamental plane correlation for GRB afterglows corrected for selection biases and redshift evolution. We choose a well defined sample: the platinum sample, composed of 50 long GRBs. To further constrain the cosmological parameters, we use baryon acoustic oscillations (BAOs) given their reliability as standard rulers. Thus, we have applied GRBs, SNe Ia, and BAOs in a binned analysis in redshifts so that the GRB contribution is fully included in the last redshift bin, which reaches z = 5. We use the fundamental plane correlation (also known as the 3D Dainotti relation), together with SNe Ia and BAOs, to constrain H0 and the density matter today, ΩM. This methodology allows us to assess the role of GRBs combined with SNe Ia and BAOs. We have obtained results for H0 and ΩM using GRBs+SNe Ia+BAOs with better precision than SNe Ia alone for every bin, thus confirming the beneficial role of BAOs and GRBs added together. In addition, consistent results between GRBs+SNe Ia+BAOs are obtained when compared with SNe Ia+BAOs, showing the importance of GRBs since the distance ladder is extended up to z = 5 with a similar precision obtained with other probes without including GRBs.</jats:p
Towards a new model-independent calibration of Gamma-Ray Bursts
No full textCurrent data on baryon acoustic oscillations and Supernovae of Type Ia (SNIa) cover up to z∼2.5. These low-redshift observations play a very important role in the determination of cosmological parameters and have been widely used to constrain the ΛCDM and models beyond the standard, such as the ones with open curvature. To extend this investigation to higher redshifts, Gamma-Ray Bursts (GRBs) stand out as one of the most promising observables. In spite of being transient, they are extremely energetic and can be used to probe the universe up to z∼9.4. They exhibit characteristics that suggest they are potentially standardizable candles and this allows their use to extend the distance ladder beyond SNIa. The use of GRB correlations is still a challenge due to the spread in their intrinsic properties. One of the correlations that can be employed for the standardization is the fundamental plane relation between the peak prompt luminosity, the rest-frame end time of the plateau phase, and its corresponding luminosity, also known as the three-dimensional Dainotti correlation. In this work, we propose an innovative method of calibration of the Dainotti relation which is independent of cosmology. We employ state-of-the-art data on Cosmic Chronometers (CCH) at z≲2 and use the Gaussian Processes Bayesian reconstruction tool. To match the CCH redshift range, we select 20 long GRBs in the range 0.553≤z≤1.96 from the Platinum sample, which consists of well-defined GRB plateau properties that obey the fundamental plane relation. To ensure the generality of our method, we verify that the choice of priors on the parameters of the Dainotti relation and the modeling of CCH uncertainties and covariance have negligible impact on our results. Moreover, we consider the case in which the redshift evolution of the physical features of the plane is accounted for. We find that the use of CCH allows us to identify a sub-sample of GRBs that adhere even more closely to the fundamental plane relation, with an intrinsic scatter of σint=0.20−0.05+0.03 obtained in this analysis when evolutionary effects are considered. In an epoch in which we strive to reduce uncertainties on the variables of the GRB correlations in order to tighten constraints on cosmological parameters, we have found a novel model-independent approach to pinpoint a sub-sample that can thus represent a valuable set of standardizable candles. This allows us to extend the cosmic distance ladder presenting a new catalog of calibrated luminosity distances up to z=5
Gamma-ray burst data strongly favor the three-parameter fundamental plane (Dainotti) correlation relation over the two-parameter one
No full textGamma-ray bursts (GRBs), observed to redshift , are potential probes
of the largely unexplored part of the early Universe. Thus,
finding relevant relations among GRB physical properties is crucial. We find
that the Platinum GRB data compilation, with 50 long GRBs (with relatively flat
plateaus and no flares) in the redshift range , and the
LGRB95 data compilation, with 95 long GRBs in , as well
as the 145 GRB combination of the two, strongly favor the three-dimensional
(3D) fundamental plane (Dainotti) correlation relation (between the peak prompt
lumininosity, the luminosity at the end of the plateau emission, and its rest
frame duration) over the two-dimensional one (between the luminosity at the end
of the plateau emission and its duration). The 3D Dainotti correlations in the
three data sets are standardizable. We find that while LGRB95 data have
% larger intrinsic scatter parameter values than the better-quality
Platinum data, they provide somewhat tighter constraints on cosmological-model
and GRB-correlation parameters, perhaps solely due to the larger number of data
points, 95 versus 50. This suggests that when compiling GRB data for the
purpose of constraining cosmological parameters, given the quality of current
GRB data, intrinsic scatter parameter reduction must be balanced against
reduced sample size.Comment: 20 pages, 8 figures. MNRAS accepted version. K-corrections now
correctly accounted for. GRB data tables now included, including an updated
version of the data table of MNRAS, 512, 439 (2022), arXiv:2201.05245. No
changes in the qualitative conclusions of either pape
Slope evolution of GRB correlations and cosmology
No full textGamma-ray bursts (GRBs) observed up to redshifts z > 9.4 can be used as possible probes to test cosmological models. Here we show how changes of the slope of the luminosity –break time correlation in GRB afterglows, hereafter the LT correlation, affect the determination of the cosmological parameters. With a simulated data set of 101 GRBs with a central value of the correlation slope that differs on the intrinsic one by a factor, we find an overestimated value of the matter density parameter, , compared to the value obtained with Type Ia supernovae, while the Hubble constant, , best-fitting value is still compatible in 1σ compared to other probes. We show that this compatibility of fh0 is due to the large intrinsic scatter associated with the simulated sample. Instead, if we consider a subsample of high-luminosity GRBs (High L), we find that the evaluation of both and is not more compatible in and is underestimated by 13 per cent. However, the High L sample choice reduces dramatically the intrinsic scatter of the correlation, thus possibly identifying this sample as the standard canonical ‘GRBs’ confirming previous results presented by Dainotti et al. Here, we consider the LT correlation as an example, but this reasoning can also be extended for all other GRB correlations. In the literature so far, GRB correlations are not corrected for redshift evolution and selection biases; therefore, we are not aware of their intrinsic slopes and consequently how far the use of the observed correlations can influence the derived ‘best’ cosmological settings. Therefore, we conclude that any approach that involves cosmology should take into consideration only intrinsic correlations and not the observed ones
Nonparametric study of the evolution of the cosmological equation of state with SNeIa, BAO, and high-redshift GRBs
No full textWe study the dark energy equation of state as a function of redshift in a nonparametric way, without imposing any a priori w (z) (ratio of pressure over energy density) functional form. As a check of the method, we test our scheme through the use of synthetic data sets produced from different input cosmological models that have the same relative errors and redshift distribution as the real data. Using the luminosity-time correlation for gamma-ray burst (GRB) X-ray afterglows (the Dainotti et al. correlation), we are able to utilize GRB samples from the Swift satellite as probes of the expansion history of the universe out to z 10. Within the assumption of a flat Friedmann-Lemaître-Robertson-Walker universe and combining supernovae type Ia (SNeIa) data with baryonic acoustic oscillation constraints, the resulting maximum likelihood solutions are close to a constant w = –1. If one imposes the restriction of a constant w , we obtain w = -0.99 0.06 (consistent with a cosmological constant) with the present-day Hubble constant as and density parameter as , while nonparametric w (z) solutions give us a probability map that is centered at and . Our chosen GRB data sample with a full correlation matrix allows us to estimate the amount, as well as quality (errors), of data needed to constrain w (z) in the redshift range extending an order of magnitude beyond the farthest SNeIa measured
High-redshift cosmology by Gamma-Ray Bursts: An overview
No full textSeveral correlations among Gamma-Ray Bursts (GRBs) quantities, both in the prompt and afterglow emissions, have been established during the last decades, thus enabling the standardization of GRBs as cosmological probes. Since GRBs are observed up to redshift z∼9, they represent a valuable tool to fill in the gap of information on the Universe evolution between the farthest type Ia supernovae and the Cosmic Microwave Background Radiation and to shed new light on the current challenging cosmological tensions. Without claiming for completeness, here we describe the state of the art of GRB correlations, their theoretical interpretations, and their cosmological applications both as standalone probes and in combination with other probes. In this framework, we pinpoint the importance of correcting the correlations for selection biases and redshift evolution to derive intrinsic relations, the assets of combining probes at different scales, and the need for the employment of the appropriate cosmological likelihood to precisely constrain cosmological parameters. Furthermore, we emphasize the benefits of the cosmographic approach to avoid any cosmological assumptions and the valuable applications of machine learning techniques to reconstruct GRB light curves and predict unknown GRB redshifts. Finally, we stress the relevance of all these factors, along with future observations, to definitely boost the power of GRBs in cosmology
Maria Bersani
No full textLa voce illustra la biografia e l'apporto letterario dato da Maria Bersani alla letteratura per l'infanziaThe headword explains the biography and the contribution of the author Maria Bersani to the children's literatur
The Scavenger Hunt for Quasar Samples to Be Used as Cosmological Tools
No full textAlthough the Λ Cold Dark Matter model is the most accredited cosmological model, information at high redshifts (z) between type Ia supernovae (z=2.26) and the Cosmic Microwave Background (z=1100) is crucial to validate this model further. To this end, we have discovered a sample of 1132 quasars up to z=7.54 exhibiting a reduced intrinsic dispersion of the relation between ultraviolet and X-ray fluxes, δF=0.22 vs. δF=0.29 (24% less), than the original sample. This gold sample, once we correct the luminosities for selection biases and redshift evolution, enables us to determine the matter density parameter ΩM with a precision of 0.09. Unprecedentedly, this quasar sample is the only one that, as a standalone cosmological probe, yields such tight constraints on ΩM while being drawn from the same parent population of the initial sample
Reducing the uncertainty on the Hubble constant up to 35\% with an improved statistical analysis: different best-fit likelihoods for Supernovae Ia, Baryon Acoustic Oscillations, Quasars, and Gamma-Ray Bursts
No full textCosmological models and their parameters are widely debated, especially about
whether the current discrepancy between the values of the Hubble constant,
, obtained by type Ia supernovae (SNe Ia), and the Planck data from the
Cosmic Microwave Background Radiation could be alleviated when alternative
cosmological models are considered. Thus, combining high-redshift probes, such
as Gamma-Ray Bursts (GRBs) and Quasars (QSOs), together with Baryon Acoustic
Oscillations (BAO) and SNe Ia is important to assess the viability of these
alternative models and if they can cast further light on the Hubble tension. In
this work, for GRBs, we use a 3-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 3D Dainotti fundamental plane relation.
Regarding QSOs, we use the Risaliti-Lusso relation among the UV and X-ray
luminosities for a sample of 2421 sources. We correct both the QSO and GRB
relations by accounting for selection and evolutionary effects with a reliable
statistical method. We here use both the traditional Gaussian likelihoods
() and the new best-fit likelihoods () to infer
cosmological parameters of a non-flat CDM and flat CDM models. We
obtain for all the parameters reduced uncertainties, up to for ,
when applying the new likelihoods in place of the Gaussian ones. Our
results remain consistent with a flat CDM model, although with a shift
of the dark energy parameter toward and a curvature density
parameter toward .Comment: Accepted for publication at Ap
Optical and X-ray GRB Fundamental Planes as Cosmological Distance Indicators
No full textGamma-Ray Bursts (GRBs), can be employed as standardized candles, extending
the distance ladder beyond Supernovae Type Ia (SNe Ia, ). We
standardize GRBs using the 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 assuming a flat
CDM 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 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 standalone probes to
achieve a comparable precision on 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
errorbars 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 lightcurve reconstruction and the estimates of
GRB redhifts when z is unknown) compared to the current sample, with errorbars
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.Comment: 31 pages, 17 figures, 10 table
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