Calibration of Gamma-Ray Bursts as Cosmological Distance Indicators Using Cosmic Chronometers

Khái niệm cốt lõi

This research proposes a novel, model-independent method for calibrating Gamma-Ray Bursts (GRBs) as cosmological distance indicators using Cosmic Chronometers (CCH) data and Gaussian Processes, potentially enabling the extension of the cosmic distance ladder to higher redshifts.

Tóm tắt

• Bibliographic Information: Favalea, A., Dainotti, M.G., Gómez-Valent, A., & Migliaccio, M. (2024). Towards a new model-independent calibration of Gamma-Ray Bursts. High Energy Astrophysics.

• Research Objective: This study aims to develop a model-independent method for calibrating the Dainotti correlations of GRBs using CCH data and Gaussian Processes to determine if they can be reliably used as cosmological distance indicators.

• Methodology: The researchers utilize a sample of 20 long GRBs from the Platinum sample, which exhibit well-defined plateau phases, within the redshift range of 0.553 ≤ z ≤ 1.96. They employ state-of-the-art CCH data and a Gaussian Processes Bayesian reconstruction tool to reconstruct the luminosity distance at the GRB redshifts. This reconstructed distance is then used to calibrate both the 3D and 2D Dainotti relations, taking into account the redshift evolution of the correlation parameters. The robustness of the method is tested by considering different priors on the Dainotti relation parameters and the impact of the covariance of the reconstructed luminosity distance.

• Key Findings: The study finds that using CCH data allows for the identification of a sub-sample of GRBs that adhere more closely to the fundamental plane relation, with an intrinsic scatter of σint = 0.20+0.03 −0.05 when considering evolutionary effects. The analysis also suggests that the peak prompt luminosity might not be essential for using the Dainotti relation as a cosmological tool, as the constraint on the parameter 'b' is compatible with zero at 68% C.L.

• Main Conclusions: The researchers demonstrate a novel model-independent approach for pinpointing a sub-sample of GRBs that can serve as valuable standardizable candles. This method allows for the extension of the cosmic distance ladder by providing a new catalog of calibrated luminosity distances up to z = 5.

• Significance: This research contributes significantly to the field of GRB cosmology by offering a new, model-independent calibration method that can potentially mitigate the circularity problem and reduce systematic biases. The ability to calibrate GRBs at higher redshifts opens up new avenues for investigating the expansion history of the universe and addressing cosmological tensions.

• Limitations and Future Research: The study acknowledges the limitations of the current sample size and encourages further investigation with larger and more comprehensive GRB datasets. Future research could also explore the impact of different kernel selections in the Gaussian Process reconstruction and investigate the potential of combining this calibration method with other cosmological probes.

Thống kê

The Platinum sample consists of 50 long GRBs with well-defined morphological features, including plateaus with an inclination < 41°, lasting > 500s, and with no flares.
The study uses a subset of 20 GRBs from the Platinum sample within the redshift range of 0.553 ≤ z ≤ 1.96, coinciding with the redshift coverage of the CCH data.
The CCH data comprises 33 data points in the redshift range of 0.07 < z < 1.965.
The analysis employs a Matérn32 kernel for the Gaussian Process reconstruction and considers both Gaussian and flat priors on the Dainotti relation parameters.
The study achieves convergence in the Monte Carlo Markov Chain analysis using a large number of walkers (∼220 for the 3D relation and ∼140 for the 2D relation) and a large number of steps in the parameter space (nsteps = 6·10^5).

Trích dẫn

"Exploring higher z requires observing more luminous objects than SNIa. This can be the case not only of QSOs, which reach up to z ∼7.5 (Banados et al., 2018), but also of Gamma-Ray Bursts (GRBs), the most intense explosions in the universe after the Big Bang."
"The great advantage of the use of GRBs is their coverage at much higher redshifts than SNIa and BAO."
"In this work, we aim to present a novel model-agnostic method to understand whether low-redshift calibrators can univocally determine the correlation parameters of GRBs, in order to use them as distance indicators."
"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."

Thông tin chi tiết chính được chắt lọc từ

Towards a new model-independent calibration of Gamma-Ray Bursts

by Aria... lúc arxiv.org 10-16-2024

https://arxiv.org/pdf/2402.13115.pdf

Yêu cầu sâu hơn

How might the increasing availability of data from future surveys like the Vera Rubin Observatory impact the calibration and use of GRBs as cosmological tools?

The increasing availability of data from future surveys like the Vera Rubin Observatory, formerly known as the Large Synoptic Survey Telescope (LSST), holds immense potential to revolutionize the calibration and use of Gamma-Ray Bursts (GRBs) as cosmological tools. This transformation will be driven by the unprecedented depth, breadth, and temporal cadence of the LSST survey, enabling several key advancements:

Increased Sample Size and Redshift Range: The LSST is anticipated to discover a significantly larger number of GRBs, potentially an order of magnitude higher than currently known, and extend the redshift range of observable GRBs. This expanded dataset will be invaluable for refining existing GRB correlations, reducing statistical uncertainties, and testing the validity of these relations over a wider cosmological epoch.

Improved Understanding of GRB Progenitors: The LSST's ability to rapidly identify and study the afterglows of GRBs will be crucial in constraining the properties of their progenitor systems. By linking GRB properties to their progenitors, we can better understand the intrinsic scatter in GRB correlations and potentially identify sub-classes of GRBs with tighter relations, leading to more precise cosmological measurements.

Multi-wavelength Counterparts and Host Galaxy Studies: The LSST's wide field of view and multi-wavelength capabilities will enable the identification and characterization of host galaxies for a larger number of GRBs. This will allow for a more comprehensive understanding of the environments in which GRBs occur and their potential impact on GRB properties. Additionally, the LSST's ability to obtain deep, multi-band photometry of GRB host galaxies will facilitate accurate redshift measurements, further enhancing their utility as distance indicators.

Time-Domain Cosmology with GRBs: The LSST's high cadence observations will be particularly beneficial for studying the temporal evolution of GRB afterglows. This will provide crucial insights into the physics of GRB jets and their interaction with the surrounding medium. Moreover, the LSST's ability to detect and monitor transient events will enable the discovery of new types of GRBs or related phenomena, potentially revealing new avenues for cosmological exploration.

In summary, the Vera Rubin Observatory's vast dataset will be transformative for GRB cosmology. By increasing the sample size, improving our understanding of GRB progenitors and host galaxies, and enabling detailed time-domain studies, the LSST will pave the way for using GRBs as precision cosmological tools, shedding light on fundamental questions about the expansion history and evolution of the Universe.

Could there be alternative explanations, beyond the magnetar model, for the observed correlations in the GRB data, and how might these affect the interpretation of the results?

While the magnetar model provides a compelling explanation for the observed correlations in GRB data, particularly the plateau phase, alternative explanations exist and warrant consideration. These alternatives could potentially impact the interpretation of GRB correlations and their use as cosmological tools. Some prominent alternative scenarios include:

Accretion Disk Winds: Instead of a magnetar, the central engine powering the GRB could be a black hole accreting material from a surrounding disk. Powerful winds launched from this accretion disk could interact with the external medium, producing the observed plateau emission. The specific correlations predicted by this model would depend on the details of the wind launching and interaction, potentially differing from the magnetar scenario.

Fallback Accretion: In this scenario, material ejected during the initial GRB explosion falls back onto the central compact object, either a black hole or a neutron star. This fallback accretion can produce long-lasting emission, potentially explaining the plateau phase. The correlations arising from this model would be governed by the fallback rate and the properties of the central object, potentially leading to different predictions compared to the magnetar model.

Dust Scattering Echoes: The observed plateau emission could be the result of light from the initial GRB pulse scattered by dust in the surrounding environment. This scattered light would arrive at the observer with a delay, mimicking a plateau. The correlations in this case would be related to the dust distribution and properties, potentially differing from intrinsic correlations associated with the GRB itself.

Multiple Component Jets: The GRB jet might not be a single, homogeneous entity but rather composed of multiple components with varying Lorentz factors and energy distributions. Interaction between these components or their interaction with the external medium could give rise to complex light curves, including plateaus, and potentially produce correlations that are not easily explained by a single-component jet model.

The existence of these alternative explanations highlights the need for further investigation and a cautious approach when interpreting GRB correlations. If the observed correlations are primarily driven by environmental factors or complex jet dynamics rather than intrinsic properties of the central engine, their use as cosmological tools might be limited.
To disentangle these possibilities, it is crucial to obtain more detailed observations of GRBs, particularly at early times and across a wide range of wavelengths. Additionally, sophisticated numerical simulations are essential for modeling different GRB scenarios and comparing their predictions with observations. By carefully considering alternative explanations and refining our understanding of GRB physics, we can better assess the reliability of GRB correlations and their potential for probing the Universe.

If GRBs prove to be reliable distance indicators at high redshifts, what fundamental questions about the early universe might we be able to answer?

If GRBs are definitively proven to be reliable distance indicators at high redshifts, they hold the potential to unlock answers to some of the most fundamental questions about the early Universe, pushing the boundaries of our cosmological understanding:

Unveiling the Epoch of Reionization: GRBs offer a unique opportunity to probe the era of reionization, a crucial phase in the early Universe when neutral hydrogen atoms were reionized by the first stars and galaxies. By tracing GRBs at increasingly high redshifts, we can map the ionization state of the intergalactic medium over cosmic time, providing insights into the nature and evolution of the first luminous sources.

Constraining the Expansion History of the Universe: GRBs, as potential standard candles, can be used to construct a Hubble Diagram extending to very high redshifts. This would allow us to probe the expansion history of the Universe in a redshift range sparsely populated by other distance indicators like Type Ia supernovae. This data would be invaluable for constraining cosmological models, particularly those aiming to explain the late-time acceleration of the Universe and the nature of dark energy.

Testing Fundamental Physics: The extreme energies and distances involved in GRBs make them ideal laboratories for testing fundamental physics. By studying the propagation of GRB photons over cosmological distances, we can search for potential deviations from the predictions of General Relativity, such as variations in the speed of light or violations of Lorentz invariance. These tests could provide hints of new physics beyond the Standard Model.

Probing the First Stars and Galaxies: GRBs are thought to be associated with the deaths of massive stars, making them potential tracers of star formation in the early Universe. By studying the properties of GRB host galaxies at high redshifts, we can gain insights into the formation and evolution of the first stars and galaxies, providing crucial information about the early stages of galaxy assembly.

Understanding the Nature of Dark Matter: The distribution of dark matter in the early Universe could have influenced the formation and evolution of GRB host galaxies. By studying the clustering properties of GRBs at high redshifts, we can potentially constrain the properties of dark matter and its role in shaping the large-scale structure of the Universe.

In conclusion, GRBs, as reliable distance indicators at high redshifts, hold immense promise for unraveling the mysteries of the early Universe. By providing a new window into this crucial epoch, GRBs can help us address fundamental questions about the expansion history, the nature of dark matter and dark energy, the physics of the first stars and galaxies, and the validity of fundamental physics on cosmological scales.