اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدConcerns about the reliability of publicly available SNe Ia data
319
0
0.0
(
0
)
تأليف
Mohamed Rameez
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
I highlight several concerns regarding the consistency of Type Ia supernova data in the publicly available Pantheon and JLA compilations. The measured heliocentric redshifts (zhel) of $sim$150 SNe Ia as reported in the Pantheon catalogue are significantly discrepant from those in JLA - with 58 having differences amounting to between 5 and 137 times the quoted measurement uncertainty. The discrepancy seems to have been introduced in the process of rectifying a previously reported issue. The Pantheon catalogue until very recently had the redshifts of all SNe Ia up to z $sim$ 0.3 modified under the guise of peculiar velocity corrections - although there is no information on peculiar velocities at such high redshifts. While this has reportedly been rectified on Github by removing peculiar velocity corrections for z > 0.08, the impact of this on the published cosmological analysis of the Pantheon catalogue is not stated. In JLA, the effect of these corrections is to significantly bias the inferred value of $Omega_{Lambda}$ towards higher values, while the equivalent effect on Pantheon cannot be ascertained due to the unavailability of the individual components of the covariance matrix in the public domain. I provide Jupyter notebooks and URLs in order to allow the reader to ascertain the veracity of these assertions.
قيم البحث
اقرأ أيضاً
We present a simple, physically-motivated model to interpret consistently the emission from galaxies at ultraviolet, optical and infrared wavelengths. We combine this model with a Bayesian method to obtain robust statistical constraints on key parame
ters describing the stellar content, star formation activity and dust content of galaxies. Our model is now publicly available via a user-friendly code package, MAGPHYS at www.iap.fr/magphys. We present an application of this model to interpret a sample of ~1400 local (z<0.5) galaxies from the H-ATLAS survey. We find that, for these galaxies, the diffuse interstellar medium, powered mainly by stars older than 10 Myr, accounts for about half the total infrared luminosity. We discuss the implications of this result to the use of star formation rate indicators based on total infrared luminosity.
Here we present a method to combine half-hourly publicly available electrical generation and interconnector operational data for Great Britain to create a timeseries that approximates its electrical demand. We term the calculated electrical demand ES
PENI that is an acronym for Elexon Sum Plus Embedded Net Imports. The method adds value to the original data by combining both transmission and distribution generation data into a single dataset and adding ISO 8601 compatible datetimes to increase interoperability with other timeseries data. Data cleansing is undertaken by visually flagging data errors and then using simple linear interpolation to impute values to replace the flagged data. Publishing the method allows it to be further enhanced or adapted and to be considered and critiqued by a wider community. In addition, the published raw and cleaned data is a valuable resource that saves researchers considerable time in repeating the steps presented in the method to prepare the data for further analysis. The data is a public record of the decarbonisation of Great Britains electrical system since late 2008, widely seen as an example of rapid decarbonisation of an electrical system away from fossil fuel generation to lower carbon sources.
Context. The solar chromosphere is the interface between the solar surface and the solar corona. Modelling of this region is difficult because it represents the transition from optically thick to thin radiation escape, from gas-pressure domination to
magnetic-pressure domination, from a neutral to an ionised state, from MHD to plasma physics, and from near-equilibrium (LTE) to non-equilibrium conditions. Aims. Our aim is to provide the community with realistic simulations of the magnetic solar outer atmosphere. This will enable detailed comparison of existing and upcoming observations with synthetic observables from the simulations, thereby elucidating the complex interactions of magnetic fields and plasma that are crucial for our understanding of the dynamic outer atmosphere. Methods. We used the radiation magnetohydrodynamics code Bifrost to perform simulations of a computational volume with a magnetic field topology similar to an enhanced network area on the Sun. Results. The full simulation cubes are made available online. The general properties of the simulation are discussed, and limitations are discussed.
We present an analysis of high precision V light curves (LC) for 18 local Type Ia Supernovae, SNe Ia, as obtained with the same telescope and setup at the Las Campanas Observatory (LCO). This homogeneity provides an intrinsic accuracy a few hundreds
of a magnitude both with respect to individual LCs and between different objects. Based on the Single Degenerate Scenario, SD, we identify patterns which have been predicted by model calculations as signatures of the progenitor and accretion rate which change the explosion energy and the amount of electron capture, respectively. Using these templates as principle components and the overdetermined system of SN pairs, we reconstruct the properties of progenitors and progenitor systems. All LCO SNe Ia follow the brightness decline relation but 2001ay. After subtraction of the two components, the remaining scatter is reduced to 0.01-0.03m. Type SNe Ia seem to originate from progenitors with Main Sequence masses of 3Mo with the exception of two subluminous SNe Ia with < 2Mo. The component analysis indicates a wide range of accretion rates in the progenitor systems closing the gap to accretion induced collapses (AIC). SN1991t-like objects show differences in $dm15$ but no tracers of our secondary parameters. This may point to a different origin such as DD-Scenario or the Pulsating Delayed Detonations. SN2001ay does not follow the decline relation. It can be understood in the framework of C-rich WDs, and this group may produce an anti-Phillips relation. We suggest that this may be a result of a common envelope phase and mixing during central He burning as in SN1987A.
The Hubble constant ($H_0$) tension between Type Ia Supernovae (SNe Ia) and Planck measurements ranges from 4 to 6 $sigma$. To investigate this tension, we estimate $H_{0}$ in the $Lambda$CDM and $w_{0}w_{a}$CDM 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: $g(z)={H_0}(z)=tilde{H}_0/(1+z)^alpha$, where $alpha$ indicates an evolutionary parameter and $tilde{H}_0=H_0$ at $z=0$. We set the absolute magnitude of SNe Ia so that $H_0=73.5,, textrm{km s}^{-1},textrm{Mpc}^{-1}$, and we fix fiducial values for $Omega_{0m}^{Lambda CDM}=0.298$ and $Omega_{0m}^{w_{0}w_{a}CDM}=0.308$. We find that $H_0$ evolves with redshift, showing a slowly decreasing trend, with $alpha$ coefficients consistent with zero only from 1.2 to 2.0 $sigma$. Although the $alpha$ coefficients are compatible with 0 in 3 $sigma$, this however may affect cosmological results. We measure locally a variation of $H_0(z=0)-H_0(z=1)=0.4, textrm{km s}^{-1},textrm{Mpc}^{-1}$ in 3 and 4 bins. Extrapolating ${H_0}(z)$ to $z=1100$, the redshift of the last scattering surface, we obtain values of $H_0$ compatible in 1 $sigma$ with Planck measurements independently of cosmological models and number of bins we investigated. Thus, we have reduced the $H_0$ tension from $54%$ to $72%$ for the $Lambda$CDM and $w_{0}w_{a}$CDM models, respectively. If the decreasing trend of $H_0(z)$ is real, it could be due to astrophysical selection effects or to modified gravity.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
