arXiv subjects

Ericson López

Publications and source records attributed to Ericson López.

11 recordsLinked to original sources

arXiv2025

Thermodynamics sheds light on the nature of dark matter galactic halos

In spherical symmetry, the gravitational potential is uniquely determined by the rotational velocity profile. Numerous galaxies exhibit a universal velocity profile from which a universal gravitational profile is inferred. When treating dark matter as either an ideal gas, a Fermi gas, or a Bose gas, only the latter can produce a gravitational profile consistent with observations, along with a temperature profile that decreases outward. This requires the mass of the boson to be below a certain threshold of $43\mbox{ eV}/c^2$. Additionally, ensuring that the speed of sound is less than the speed of light yields a lower bound on the boson's mass.

astro-ph.GA↗

arXiv2024

Preliminary Study on Dark Matter-Dominated Systems: Further Analysis for galactic dark matter halos with Pressure

Low surface brightness galaxies are an excellent laboratory where stars and baryonic matter act as tracers of the gravitational potential of the dark matter halo. If dark matter is modeled as a perfect fluid, then spherically symmetric and static dark matter halos in hydrostatic equilibrium demand that dark matter should have an intrinsic pressure that counteracts the gravitational attraction that the dark matter halo exerts on itself. This static fluid (dark matter-dominated system, where the presence of baryons is negligible) has a specific equation of state for each rotational velocity profile of the stars in galaxies. In this work, we study the dark matter equation of state needed for the self-gravitating object to produce a gravitational potential such that the tracers follow the Universal Rotational Velocity Profile for stars of spiral galaxies proposed by Persic et al. (1996) and analyze the properties of the self-gravitating structures that emerge from this equation of state.The resulting configurations explaining the observed rotational speeds are found to be unstable. We conclude that the halo is not in hydrostatic equilibrium, it is nonspherically symmetric, or it is not static if the universal velocity profile should be valid for fitting the rotational velocity curve of the galaxies.

astro-ph.GA↗

arXiv2019

Circular geodesics stability in a static black hole in new massive gravity

We study the existence and stability of circular geodesics in a family of asymptotically AdS static black holes in New Massive Gravity. We show that the existence of such geodesics is determined by the sign of the hair parameter. For a positive hair parameter the stability regions follow the usual pattern, with an innermost unstable null geodesic separated from the horizon, followed by a region of unstable timelike geodesics and then stable timelike geodesics extending in the asymptotic region.

gr-qc↗

arXiv2018

SS433 jet precession: infrared dispersion Doppler effect

In the infrared part of the electromagnetic spectrum, the relativistic dispersion theory is applied to the SS433 jets, to describe its dispersion properties. In particular, we here investigate the dispersion Doppler effect of the radiation in the relativistic cold plasma approximation for this micro-quasar. We find that the Doppler plasma line displacements in SS433 are affected by the plasma dispersion only in a narrow frequency band; in the far infrared (far-IR) one. As a consequence, although the shift $Z$ modulation due to the precession of the SS433 jets is well described by previous works in the optical range, it has to be corrected by plasma dispersion effects in the far-IR range.

astro-ph.HE↗

arXiv2018

Magnetic field constraint in the outskirts of spiral galaxies

Based on CO(2-1) public data, we study the monoxide oxygen gas excitation conditions and the magnetic field strength of NGC 2841, NGC 3077, NGC 3184, NGC 3351 spiral galaxies. For their galaxy outskirts, we found kinetic temperatures in the range of $35 - 38 ~K$, CO column densities $10^{15} - 10^{16} ~cm^{-2}$ and H2 masses of $4 ~10^6 - 6 ~ 10^8 M_\odot$. An H2 density 1$0^3 cm^{-3}$ is suitable to explain the 2 sigma upper limits of the CO(2-1) line intensity. We constrain the magnetic field strength for our sample of spiral galaxies and their outskirts, evaluating a simplified expression of the magneto-hydrodynamic force equation. Our estimations provide values for the magnetic field strength in the order of $6-31 ~μG$.

astro-ph.GA↗

arXiv2017

Isoperimetric surfaces and area-angular momentum inequality in a rotating black hole in New Massive Gravity

We study the existence and stability of isoperimetric surfaces in a family of rotating black holes in New Massive Gravity. We show that the stability of such surfaces is determined by the sign of the hair parameter. We use the isoperimetric surfaces to find a geometric inequality between the area and the angular momentum of the black hole, conjecturing geometric inequalities for more general black holes.

gr-qc↗

arXiv2017

The HI Distribution Observed toward a Halo Region of the Milky Way

We use observations of the neutral atomic hydrogen (HI) 21-cm emission line to study the spatial distribution of the HI gas in a 80$\degree\times~$90$\degree$ region of the Galaxy halo. The HI column densities in the range of \mbox{3--11$\times$10$^{20}$ cm$^{-2}$} have been estimated for some of the studied regions. In our map---obtained with a spectral sensitivity of $\sim$2 K---we do not detect any HI 21-cm emission line {above 2$σ$} at Galactic latitudes higher than $\sim${46}$\degree$. {This report summarizes our contribution presented at the conference on the origin and evolution of barionic Galaxy halos}.

astro-ph.GA↗

arXiv2017

Upper Limits to Magnetic Fields in the Outskirts of Galaxies

Based on CO(2-1) public data, we study the monoxide oxygen gas excitation conditions and the magnetic field strength of four spiral galaxies. For the galaxy outskirts, we found kinetic temperatures in the range of $\lesssim$35--38 K, CO column densities $\lesssim 10^{15}$--$10^{16}$ cm$^{-2}$, and H$_2$ masses $\lesssim 4\times 10^6$--$6\times10^8$ M$_\odot$. An H$_2$ density $\lesssim 10^3$ cm$^{-3}$ is suitable to explain the 2$σ$ upper limits of the CO(2-1) line intensity. We constrain the magnetic field strength for our sample of spiral galaxies and their outskirts by using their masses and H$_2$ densities to evaluate a simplified magneto-hydrodynamic equation. Our estimations provide values for the magnetic field strength on the order of $\lesssim$6--31 {$\upmu$G}.

astro-ph.GA↗

arXiv2017

Dust Deficiency in the Interacting Galaxy NGC 3077

Using 70 $μ$ m observations taken with the PACS instrument of the Herschel space telescope, the dust content of the nearby and interacting spiral galaxy NGC 3077 has been compared with the dust content of the isolated galaxies such as NGC 2841, NGC 3184 and NGC 3351. The dust content has allowed us to derive dust-to-gas ratios for the four spiral galaxies of our sample. We find that NGC 2841, NGC 3184 and NGC 3351 have dust masses of 6.5-9.1 $\times$ 10$^7$ M$\odot$, which are a factor of $\sim$10 higher than the value found for NGC 3077. This result shows that NGC 3077 is a dust deficient galaxy, as was expected, because this galaxy is affected by tidal interactions with its neighboring galaxies M81 and M82. NGC 3077 reveals a dust-to-gas ratio of 17.5%, much higher than the average ratio of 1.8% of the isolated galaxies, evidencing that NGC 3077 is also deficient in H$_2$+HI gas. Therefore, it seems that, in this galaxy, gas has been stripped more efficiently than dust.

astro-ph.GA↗

arXiv2017

An Extreme Rotating Black Hole in New Massive Gravity Theory

New Massive Gravity is an alternative theory to General Relativity that is used to describe the gravitational field in a (2+1)-dimensional spacetime. Black hole solutions have been found in this theory, in particular an asymptotically anti-de Sitter rotating black hole. We analyse some features of this solution as its event horizon, black hole area and distance to the horizon, specially in the rotating extreme case, showing that they have shared features with extreme black holes in 4-dimensional General relativity. This limit case is interesting in the search of geometric inequalities as the ones found for the Kerr black hole in (3+1)-General Relativity.

gr-qc↗

arXiv2013

First Magdas Equipment In Ecuador

The Magnetic Data Acquisition System (MAGDAS) was installed in the protected Jerusalem Park in Malchingui-Ecuador in October of 2012, under the joint collaboration between Kyushu University of Japan and the Quito Astronomical Observatory of the National Polytechnic School of Ecuador. In this paper, we describe the installation process and present the preliminary data obtained with the MAGDAS equipment. The behavior of the four components, D, H, Z and F allow us to see the importance of having the Ecuador station where the magnetic field has not been systematically measured before, in valuable contribution to study of the equatorial atmosphere.

physics.space-ph↗