ABSTRACT
Statistical analyses of measurements of the Hubble–Lemaître constant H0 (163 measurements between 1976 and 2019) show that the statistical error bars associated with the observed parameter ...measurements have been underestimated – or the systematic errors were not properly taken into account – in at least 15–20 per cent of the measurements. The fact that the underestimation of error bars for H0 is so common might explain the apparent discrepancy of values, which is formally known as the Hubble tension. Here we have carried out a recalibration of the probabilities with this sample of measurements. We find that thexσ deviation is indeed equivalent in a normal distribution to the xeqσ deviation in the frequency of values, where xeq = 0.83x0.62. Hence, a tension of 4.4σ, estimated between the local Cepheid–supernova distance ladder and cosmic microwave background (CMB) data, is indeed a 2.1σ tension in equivalent terms of a normal distribution of frequencies, with an associated probability P(>xeq) = 0.036 (1 in 28). This can be increased up to a equivalent tension of 2.5σ in the worst of the cases of claimed 6σ tension, which may occur anyway as a random statistical fluctuation.
The main foundations of the standard
Λ
CDM model of cosmology are that: (1) the redshifts of the galaxies are due to the expansion of the Universe plus peculiar motions; (2) the cosmic microwave ...background radiation and its anisotropies derive from the high energy primordial Universe when matter and radiation became decoupled; (3) the abundance pattern of the light elements is explained in terms of primordial nucleosynthesis; and (4) the formation and evolution of galaxies can be explained only in terms of gravitation within a inflation + dark matter + dark energy scenario. Numerous tests have been carried out on these ideas and, although the standard model works pretty well in fitting many observations, there are also many data that present apparent caveats to be understood with it. In this paper, I offer a review of these tests and problems, as well as some examples of alternative models.
The total red shift
z
might be recast as a combination of the expansion red shift and a static shift due to the energy–momentum tensor non-conservation of a photon propagating through ...Electro-Magnetic (EM) fields. If massive, the photon may be described by the de Broglie–Proca (dBP) theory which satisfies the Lorentz(-Poincaré) Symmetry (LoSy) but not gauge-invariance. The latter is regained in the Standard-Model Extension (SME), associated with LoSy Violation (LSV) that naturally dresses photons of a mass. The non-conservation stems from the vacuum expectation value of the vector and tensor LSV fields. The final colour (red or blue) and size of the static shift depend on the orientations and strength of the LSV and EM multiple fields encountered along the path of the photon. Turning to cosmology, for a zero
Ω
Λ
energy density, the discrepancy between luminosity and red shift distances of SNeIa disappears thanks to the recasting of
z
. Massive photons induce an effective dark energy acting ‘optically’ but not dynamically.
Aims. We derive the stellar rotation curve of the Galaxy in the range of Galactocentric radii of R = 4−16 kpc at different vertical heights from the Galactic plane of z between –2 and +2 kpc. With ...this we reach high Galactocentric distances in which the kinematics is poorly known due mainly to uncertainties in the distances to the sources. Methods. We used the PPMXL survey, which contains the USNO-B1 proper motions catalog cross–correlated with the astrometry and near-infrared photometry of the 2MASS Point Source Catalog. To improve the accuracy of the proper motions, we calculated the average proper motions of quasars to know their systematic shift from zero in this PPMXL survey, and we applied the corresponding correction to the proper motions of the whole survey, which reduces the systematic error. We selected from the color–magnitude diagram K vs. (J − K) the standard candles corresponding to red clump giants and used the information of their proper motions to build a map of the rotation speed of our Galaxy. Results. We obtain an almost flat rotation curve with a slight decrease for higher values of R or |z|. The most puzzling result is obtained for the farthest removed and most off-plane regions, that is, at R ≈ 16 kpc and |z| ≈ 2 kpc, where a significant deviation from a null average proper motion (~4 mas/yr) in the Galactic longitude direction for the anticenter regions can be directly translated into a rotation speed much lower than at the solar Galactocentric radius. In particular, we obtain an average speed of 82 ± 5(stat.) ± 58(syst.) km s-1 (assuming a solar Galactocentric distance of 8 kpc, and a circular/azimuthal velocity of 250 km s-1 for the Sun and of 238 km s-1 for the Local Standard of Rest), where the high systematic error bar is due mainly to the highest possible contamination of non-red clump giants and the proper motion systematic uncertainty. Conclusions. A scenario with a rotation speed lower than 150 km s-1 in these farthest removed and most off-plane regions of our explored zone is intriguing, and invites one to reconsider different possibilities for the dark matter distribution. However, given the high systematic errors, we cannot conclude about this. Hence, more measurements of the proper motions at high R and |z| are necessary to validate the exotic scenario that would arise if this low speed were confirmed.
Context. A number of recent papers have claimed the discovery of an X-shape structure in the bulge of our Galaxy in the population of the red clumps. Aims. We endeavor to analyze the stellar density ...of bulge stars in the same regions using a different stellar population that is characteristic of the young bulge (≲ 5 Gyr). Particularly, we use F0-F5 main-sequence stars with distances derived through photometric parallax. Methods. We extract these stars from extinction-corrected color-magnitude diagrams in the near-infrared of VISTA-VVV data in some bulge regions and calculate the densities along the line of sight. We take the uncertaintity in the photometric parallax and the contamination of other sources into account, and we see that these errors do not avoid the detection of a possible double peak along some lines of sight as expected for a X-shape bulge if it existed. Results. Only a single peak in the density distribution along the line of sight is observed, so apparently there is no X-shape structure for this population of stars. Nonetheless, the effects of the dispersion of absolute magnitudes in the selected population might be an alternative explanation, although in principle these effects are insufficient to explain this lack of double peak according to our calculations. Conclusions. The results of the present paper do not demonstrate that previous claims of X-shaped bulge using only red clump stars are incorrect, but there are apparently some puzzling questions if we want to maintain the validity of both the red-clump results and the results of this paper.
Abstract
We use data from the Gaia DR3 data set to estimate the mass of the Milky Way (MW) by analyzing the rotation curve in the range of distances 5 to 28 kpc. We consider three mass models: The ...first model adds a spherical dark matter (DM) halo, following the Navarro–Frenk–White (NFW) profile, to the known stellar components. The second model assumes that DM is confined to the Galactic disk, following the idea that the observed density of gas in the Galaxy is related to the presence of a more massive DM disk (DMD), similar to the observed correlation between DM and gas in other galaxies. The third model only uses the known stellar-mass components and is based on the Modified Newton Dynamics (MOND) theory. Our results indicate that the DMD model is comparable in accuracy to the NFW and MOND models and fits the data better at large radii where the rotation curve declines but has the largest errors. For the NFW model, we obtain a virial mass
M
vir
= (6.5 ± 0.3) × 10
11
M
⊙
with concentration parameter
c
= 14.5, which is lower than what is typically reported. In the DMD case, we find that the MW mass is
M
d
= (1.6 ± 0.5) × 10
11
M
⊙
with a disk’s characteristic radius of
R
d
= 17 kpc.
The stellar density distribution of the bulge is analyzed through one of its tracers. We use oxygen-rich Mira variables from the Catchpole et al. survey and OGLE-III survey as standard candles. The ...average age of these stars is around 9 Gyr. The population traced by Mira variables matches a boxy bulge prediction, not an X-shaped one, because only one peak is observed in the density along the analyzed lines of sight, whereas the prediction of an X-shape gives two clear peaks.
ABSTRACT
In order to investigate the potential Hubble tension, we compile a catalogue of 216 measurements of the Hubble–Lemaître constant H0 between 2012 and 2022, which includes 109 ...model-independent measurements and 107 ΛCDM model-based measurements. Statistical analyses of these measurements show that the deviations of the results with respect to the average H0 are far larger than expected from their error bars if they follow a Gaussian distribution. We find that xσ deviation is indeed equivalent in a Gaussian distribution to xeqσ deviation in the frequency of values, where xeq = 0.72x0.88. Hence, a tension of 5σ, estimated between the Cepheid-calibrated type Ia supernovae and cosmic microwave background (CMB) data, is indeed a 3σ tension in equivalent terms of a Gaussian distribution of frequencies. However, this recalibration should be independent of the data whose tension we want to test. If we adopt the previous analysis of data of 1976–2019, the equivalent tension is reduced to 2.25σ. Covariance terms due to correlations of measurements do not significantly change the results. None the less, the separation of the data into two blocks with H0 < 71 and H0 ≥ 71 km s−1 Mpc−1 finds compatibility with a Gaussian distribution for each of them without removing any outlier. These statistical results indicate that the underestimation of error bars for H0 remain prevalent over the past decade, dominated by systematic errors in the methodologies of CMB and local distance ladder analyses.
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