arXiv subjects

Martin Lopez-Corredoira

Publications and source records attributed to Martin Lopez-Corredoira.

At least 19 recordsLinked to original sources

arXiv2026

Towards Unveiling the Origins of the Milky Way Bulge through Multi-band-Messenger Sky Surveys

We analyze the structure and chemo-dynamical properties of the Galactic bulge using ab-type RR Lyrae stars (RRabs) from OGLE-IV and giant stars from APOGEE and Gaia. Orbital integration of 1,879 RRab variables reveals three populations: central bulge, inner bulge, and halo/disk contaminants. Inner bulge RRabs display bar-like kinematics, whereas central bulge stars show slower rotation and lower dispersion. APOGEE data for 28,188 stars confirm these kinematic trends and reveal a bimodal chemical distribution, indicating distinct formation pathways. Our results support a pseudo-bulge origin of the inner bulge through disk instability, with the overall morphology better described as boxy rather than X-shaped. Through the integration of multi-messenger, multi-band data, our collaboration aims to provide deeper insights into the physical properties and evolutionary history of the Galactic bulge.

astro-ph.GA↗

arXiv2026

Constraints on CMBR flux due to high-z dust emission

Gjergo & Kroupa (2025) have proposed a new foreground CMBR component produced by dust associated with the progenitor clouds at $z=15-20$ that led to the formation of massive early-type galaxies, calculating that a minimum of 1.4% and a maximum of 100% of the whole CMBR radiation would be produced by this mechanism. Here, I check how much dust emission is compatible with the spectrum of the CMBR monopole flux measurements within the corresponding errors. COBE-FIRAS monopole is fitted to different models with different dust emissivity spectral indexes ($β$) and dispersion of redshifts of the progenitor clouds ($σ_d$). Within the realistic values of $β\ge 0.5$, $σ_d\ge 0.8$, the contamination of CMBR flux by high $z$ dust should be $<1.3$% (95% CL).

astro-ph.CO↗

arXiv2024

Milky Way dark matter distribution or MOND test from vertical stellar kinematics with Gaia DR3

Vertical stellar kinematics+density can be used to trace the dark matter distribution [or the equivalent phantom mass in a Modified Newtonian Dynamics (MOND) scenario] through Jeans equations. In this paper, we want to improve this type of analysis by making use of the recent data of the 6D information from the Gaia-DR3 survey in the anticenter and the Galactic poles to obtain the dynamical mass distribution near plane regions, including extended kinematics over a wide region of 8 kpc$ R_\odot$, $z=1.05$ kpc: $Σ=28.7\pm 9.6$, $23.0\pm 5.7$, $16.9\pm 5.8$, $11.4\pm 6.6$ M$_\odot$ pc$^{-2}$, respectively, for $R=10,13,16,19$ kpc, compatible with visible matter alone. Larger error bars in comparison with previous works are not due to worse data or a more awkward technique but to a stricter modeling of the stellar distribution.

astro-ph.GA↗

arXiv2024

Underestimation of Hubble constant error bars: a historical analysis

An analysis of a historical compilation of Hubble-Lemaître constant values ($H_0$: 163 data points measured between 1976 and 2019) assuming the standard cosmological model gives a $χ^2$ value of the dispersion with respect to the weighted average of 580, much larger than the number of points, which has an associated probability that is very low. This means that Hubble tensions were always present in the literature, due either to the underestimation of statistical error bars associated with the observed parameter measurements, or to the fact that systematic errors were not properly taken into account in many of the measurements. The fact that the underestimation of error bars for $H_0$ is so common might explain the apparent 4.4-sigma discrepancy by Riess et al. As a matter of fact, more recent precise $H_0$ measurements with JWST data by Freedman et al. using standard candles in galaxies find there is no tension with CMBR data, possibly indicating that previously Riess et al. had underestimated their errors. Here we have carried out a recalibration of the probabilities. The tension of 4.4-$σ$, estimated between the local Cepheid-supernova distance ladder and cosmic microwave background (CMB) data, is indeed a 2.1-$σ$ tension in equivalent terms of a normal distribution, with an associated probability $P$ = 0.036 (1 in 28). This can be increased to an equivalent tension of 2.5-$σ$ in the worst cases of claimed 6-$σ$ tension, which may in any case happen as a random statistical fluctuation. If Hubble tensions were always present in the literature, and present day tensions are not more important than previous ones, why, then, is there so much noise and commotion surrounding Hubble tension after 2019? It is suggested here that this obeys a sociological phenomenon of ``groupthink''.

physics.hist-ph↗

arXiv2024

Galaxy Ages with Redshift z=2-4: Stellar Population Synthesis for Candidates in FourStar Galaxy Evolution Survey

Observations of large amount of massive galaxies with relatively old populations found at high redshifts are challenging galaxy formation scenarios within standard cosmology. Precise determinations of the average age of these galaxies would be useful for the discussion of this problem. Here we carry out a better constraint of the age of 200 V-shaped SED non-AGN galaxies at redshifts $2 2.5$, we do not see a significant evolution of their average age, with all average ages of galaxies mostly remaining between 1 and 2 Gyr. Our research find that most massive galaxies ($\sim 10^{10} M_\odot$ ) are older (typically $>\sim 1$ Gyr old) and formed earlier than less massive galaxies in our sample.

astro-ph.GA↗

arXiv2023

History and Problems of the Standard Model in Cosmology

Since the beginning of the 20th century, a continuous evolution and perfection of what we today call the standard cosmological model has been produced, although some authors like to distinguish separate periods within this evolution. A possible historical division of the development of cosmology into six periods is: (1) the initial period (1917-1927); (2) the period of development (1927-1945); (3) the period of consolidation (1945-1965); (4) the period of acceptance (1965-1980); (5) the period of enlargement (1980-1998); and (6) the period of high-precision experimental cosmology (1998-now). The last period started with a epistemological optimism that has declined with time, and the expression "crisis in cosmology" is now stubbornly reverberating in the media. The initial expectation of removing the pending minor problems arising from the increased accuracy of measurements has backfired: the higher the precision with which the standard model tries to fit the data, the greater the number of tensions that arise, the problems proliferating rather than diminishing.

physics.hist-ph↗

arXiv2023

Mass models of the Milky Way and estimation of its mass from the GAIA DR3 data-set

We use data from the Gaia DR3 dataset to estimate the mass of the Milky Way (MW) by analyzing the rotation curve in the range of distances 5 kpc 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 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 $M_{vir}= (6.5 \pm 0.3) \times 10^{11} \; M_\odot$ with concentration parameter $c=14.5$, that is lower than what is typically reported. In the DMD case we find that the MW mass is $M_d = (1.6 \pm 0.5) \times 10^{11} \; M_\odot$ with a disk's characteristic radius of $R_d=17$ kpc.

astro-ph.GA↗

arXiv2022

Hubble tensions: a historical statistical analysis

Statistical analyses of the measurements of the Hubble-Lemaître constant $H_0$ (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\% of the measurements. The fact that the underestimation of error bars for $H_0$ is so common might explain the apparent discrepancy of values, which is formally known today as the Hubble tension. Here we have carried out a recalibration of the probabilities with this sample of measurements. We find that $xσ$ deviation is indeed equivalent in a normal distribution to $x_{\rm eq.}σ$s deviation in the frequency of values, where $x_{\rm eq.}=0.83x^{0.62}$. Hence, a tension of 4.4$σ$, estimated between the local Cepheid-supernova distance ladder and cosmic microwave background (CMB) data, is indeed a 2.1$σ$ tension in equivalent terms of a normal distribution of frequencies, with an associated probability $P(>x_{\rm eq.})=0.036$ (1 in 28). This can be increased up to a equivalent tension of 2.5$σ$ in the worst of the cases of claimed 6$σ$ tension, which may anyway happen as a random statistical fluctuation.

astro-ph.CO↗

arXiv2022

Alternative ideas in cosmology

Some remarkable examples of alternative cosmological theories are reviewed here, ranging from a compilation of variations on the Standard Model through the more distant quasi-steady-state cosmology, plasma cosmology, or universe models as a hypersphere, to the most exotic cases including static models. The present-day standard model of cosmology, Lambda-CDM, gives us a representation of a cosmos whose dynamics is dominated by gravity with a finite lifetime, large scale homogeneity, expansion and a hot initial state, together with other dark elements necessary to avoid certain inconsistencies with observations. There are however some models with characteristics that are close to those of the standard model but differing in some minor aspects: different considerations on CP violation, inflation, number of neutrino species, quark-hadron phase transition, baryonic or non-baryonic dark-matter, dark energy, nucleosynthesis scenarios, large-scale structure formation scenarios; or major variations like a inhomogeneous universe, Cold Big Bang, varying physical constants or gravity law, zero-active mass (also called `R_h=ct'), Milne, and cyclical models. At the most extreme distance from the standard model, the static models, a non-cosmological redshift includes `tired-light' hypotheses, which assume that the photon loses energy owing to an intrinsic property or an interaction with matter or light as it travels some distance, or other non-standard ideas. Our impression is that none of the alternative models has acquired the same level of development as Lambda-CDM in offering explanations of available cosmological observations. One should not, however, judge any theory in terms of the number of observations that it can successfully explain (ad hoc in many cases) given the much lower level of development of the alternative ones.

astro-ph.CO↗

arXiv2020

A Chi-Squared Analysis of the Measurements of Two Cosmological Parameters Over Time

The aim of this analysis was to determine whether or not the given error bars truly represented the dispersion of values in a historical compilation of two cosmological parameters: the amplitude of mass fluctuations ($σ_8$) and Hubble's constant ($H_0$) parameters in the standard cosmological model. For this analysis, a chi-squared test was executed on a compiled list of past measurements. It was found through analysis of the chi-squared ($χ^2$) values of the data that for $σ_8$ (60 data points measured between 1993 and 2019 and $χ^2$ between 182.4 and 189.0) the associated probability Q is extremely low, with $Q = 1.6 \times 10^{-15}$ for the weighted average and $Q = 8.8 \times 10^{-15}$ for the best linear fit of the data. This was also the case for the $χ^2$ values of $H_0$ (163 data points measured between 1976 and 2019 and $χ^2$ between 480.1 and 575.7), where $Q = 1.8 \times 10^{-33}$ for the linear fit of the data and $Q = 1.0 \times 10^{-47}$ for the weighted average of the data. The general conclusion was 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 20\% of the measurements. The~fact that the underestimation of error bars for $H_0$ is so common might explain the apparent 4.4$σ$ discrepancy formally known today as the Hubble tension.

astro-ph.CO↗

arXiv2020

Relationship between rotation curves and matter distribution in spiral galaxy discs

Feng & Gallo (2011) developed a numerical method of deriving rotation curves from the density distribution and, in particular, the inverse problem while considering just a self-gravitating disc and the thin disc approximation. Our first aim here is to reproduce the same analysis and expand it with various ideas and examples. The main obstacles to building this numerical implementation are certain singularities. We try to fix the instabilities using different methods. Moreover, we add a final chapter extending the problem and its method to a third dimension through the perpendicular to the galactic plane. The dark halo (whose density is usually represented by a nearby spherical distribution) is supposed to support the outer parts of the rotation curves of spiral galaxies. Here, however, we work only with a self-gravitation disc. To treat this topic we first calculate the disc density distribution from measured rotation curve data of the Milky Way. We then compare this distribution with the observed exponential stellar density, and the difference is attributed to a dark disc. This representation of Feng & Gallo of the Galaxy with a dark disc instead of a dark halo is controversial. When we analyse the effect of flares on rotation curves, the thin disc approximation fails, and we need to introduce a vertical dimension to measure and predict the effects of the flare through different heights. Just by spreading the mass perpendicularly to the plane -- without adding any further mass -- the flare provokes no severe changes on the rotation curve. The flare mainly provokes a faster velocity decrease in the outer part of the Galaxy ($r\gtrsim 14$ kpc). But we also have obtained a slight velocity increase in the first kiloparsecs after the starting point of the flare.

astro-ph.GA↗

arXiv2019

Edwin P. Hubble, astropolítico

Rather than offering chronologically ordered encyclopedic knowledge of a lifetime, only some of the most striking events of the existence of this well-known scientist are here pointed out. Sections: Life; Man of laws; Interest in philosophy; Astronomer, astrophysicist, cosmologist; The discovery of the expansion of the Universe; Reasonable doubt about the expansion; The astropolitician. Apart from his scientific ideas of cosmological scope, his worldview has been that of a pragmatic thinker with training in law, who converts science into a large company and the scientific hypothesis into a convenient truth that deserves to be defended and arrogated, although deep down it is known that such reasons are not exclusive or original and that there are also reasons to defend the opposite thing. ------ Más que ofrecer un conocimiento enciclopédico cronológicamente ordenado de toda una vida, señalaré solamente algunos de los eventos más llamativos de la existencia del ampliamente reconocido científico. Secciones: Vida; Hombre de leyes; Interés por la filosofía; Astrónomo, astrofísico, cosmólogo; El descubrimiento de la expansión del Universo; Duda razonable sobre la expansión; El astropolítico. Aparte de sus ideas científicas de alcance cosmológico, su cosmovisión ha sido la de un pensador pragmático con formación de abogado, que convierte la ciencia en una gran empresa y la hipótesis científica en una verdad conveniente que merece defenderse y arrogarse, aunque en el fondo se sepa que no son exclusivas ni originales tales razones y que hay también razones para defender lo contrario.

physics.hist-ph↗

arXiv2019

Kinematics and dynamics of the Galactic disc

The Milky Way disc presents a warp, a flare, lopsidedness and other deviations from a purely axisymmetrical double exponential density component, both for the stellar and the gas component. Moreover, recent large-scale extended kinematics maps of Gaia data have shown significant departures from circularity in the mean orbits with radial Galactocentric velocities between -20 and +20 km/s and vertical velocities between -10 and +10 km/s, asymmetries northern/southern and other anomalies. The observed features are sensitive to internal and external forces, especially at the largest Galactocentric distances. Here we review some of the Galactic dynamics hypotheses that explain these anomalies: either in terms of gravitational interaction, magnetic fields, accretion of intergalactic matter or others. The gravitational interaction may be among the different components of the Galaxy or between the Milky Way and another companion galaxy. The accretion of intergalactic matter may be either into the halo, with a later gravitational interaction between the misaligned halo and the disc, or directly onto the disc. Most of the relevant observations are explained in terms of the accretion of intergalactic matter onto a disc that is far from a simple stationary configuration in rotational equilibrium. Other hypotheses only partially explain some observations.

astro-ph.GA↗

arXiv2018

Nonaxisymmetric models of galaxy velocity maps

Galaxy velocity maps often show the typical pattern of a rotating disk, consistent with the dynamical model where emitters rotate in circular orbits around the galactic center. The simplest template used to fit these maps consists in the rotating disk model (RDM) where the amplitude of circular velocities is fixed by the observed velocity profile along the kinematic axis. A more sophisticated template is the rotating tilted-ring model (RTRM) that takes into account the presence of warps and allows a radius-dependent orientation of the kinematic axis. In both cases, axisymmetry is assumed and residuals between the observed and the model velocity fields are interpreted as noncircular motions. We show that if a galaxy is not axisymmetric, there is an intrinsic degeneracy between a rotational and a radial velocity field. We then introduce a new galaxy template, the radial ellipse model (REM), that is not axisymmetric and has a purely radial velocity field with an amplitude that is correlated with the major axis of the ellipse. We show that best fits to the observed two-dimensional velocity fields of 28 galaxies extracted from the THINGS sample with both the REM and the RDM give residuals with similar amplitudes, where the REM residuals trace nonradial motions. Best fits obtained with the RTRM, because of its larger number of free parameters, give the smallest residuals: however, we argue that this does not necessarily imply that the RTRM gives the most accurate representation of a galaxy velocity field. Instead, we show that this method is not able to disentangle between circular and radial motions for the case of nonaxisymmetric systems. Finally, we consider the physical motivation of the REM, and discuss how the interpretation of galactic dynamics changes if one assumes that the main component of a galaxy velocity field is modeled as a RDM/RTRM or as a REM.

astro-ph.GA↗

arXiv2018

Problems with the dark matter and dark energy hypotheses, and alternative ideas

Two exotic elements have been introduced into the standard cosmological model: non-baryonic dark matter and dark energy. The success in converting a hypothesis into a solid theory depends strongly on whether we are able to solve the problems in explaining observations with these dark elements and whether the solutions of these problems are unique within the standard paradigm without recourse to alternative scenarios. We have not achieved that success yet because of numerous inconsistencies, mainly on galactic scales, the non-detection so far of candidate particles for dark matter, and the existence of many alternative hypotheses that might substitute the standard picture to explain the cosmological observations. A review of some ideas and facts is given here.

astro-ph.CO↗

arXiv2018

Reply to the claim by van Dokkum et al. for a galaxy not containing dark matter

The following is a short comment on the recent claim made by van Dokkum and collaborators about the existence of a low surface brightness galaxy, NGC1052-DF2, not containing dark matter. A discovery used by the authors to both reject proposals of a failure of Newtonian dynamics in the low acceleration regime (e.g., MOND), and prove the dark matter hypothesis is correct. It is shown here that the claim in untenable.

astro-ph.GA↗

arXiv2017

Evidence of a truncated spectrum in the angular correlation function of the cosmic microwave background

The lack of large-angle correlations in the fluctuations of the cosmic microwave background (CMB) conflicts with predictions of slow-roll inflation. But though probabilities (< 0.24%) for the missing correlations disfavor the conventional picture at > 3 sigma, factors not associated with the model itself may be contributing to the tension. Here we aim to show that the absence of large-angle correlations is best explained with the introduction of a non-zero minimum wavenumber k_min for the fluctuation power spectrum P(k). We assume that quantum fluctuations were generated in the early Universe with a well-defined power spectrum P(k), though with a cutoff k_min not equal to 0. We then re-calculate the angular correlation function of the CMB and compare it with Planck observations. The Planck 2013 data rule out a zero k_min at a confidence level exceeding 8 sigma. Whereas purely slow-roll inflation would have stretched all fluctuations beyond the horizon, producing a P(k) with k_min=0---and therefore strong correlations at all angles---a k_min > 0 would signal the presence of a maximum wavelength at the time (t_dec) of decoupling. This argues against the basic inflationary paradigm---perhaps even suggesting non-inflationary alternatives---for the origin and growth of perturbations in the early Universe. In at least one competing cosmology, the R_h=ct universe, the inferred k_min corresponds to the gravitational radius at t_dec.

astro-ph.CO↗

arXiv2017

Absence of an X-shaped Structure in the Milky Way Bulge Using Mira Variable Stars

The stellar density distribution of the bulge is analyzed through one of its tracers. We use oxygen-rich Miras variables from the Catchpole et al. (2016) 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.

astro-ph.GA↗