Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · astro-ph/0609209

Properties of RR Lyrae stars in the inner regions of the Large Magellanic Cloud. II. The extended sample

J. Borissova·D. Minniti·M. Rejkuba·D. Alves
View original source ↗Read source document ↗Export metadata ↓

Abstract

All galaxies that have been adequately examined so far have shown an extended stellar halo. To search for such a halo in the LMC we have obtained low-resolution spectra for 100 LMC RR Lyrae stars, of which 87 are in the field and 13 in the clusters NGC1835 and NGC2019. We measured radial velocities for 87 LMC RR Lyrae stars, and metallicities for 78 RR Lyrae stars, nearly tripling the previous sample. These targets are located in 10 fields covering a wide range of distances, out to 2.5 degrees from the center of the LMC. Our main result is that the mean velocity dispersion for the LMC RR Lyrae stars is 50+-2km/s. This quantity does not appear to vary with distance from the LMC center. The metallicity shows a Gaussian distribution, with mean [Fe/H]=-1.53+-0.02dex, and dispersion 0.20 dex in the Harris metallicity scale, confirming that they represent a very homogeneous metal-poor population. There is no dependence between the kinematics and metallicity of the field RR Lyrae star population. Using good quality low-resolution spectra from FORS1, FORS2 and GEMINI-GMOS we have found that field RR Lyrae stars in the LMC show a large velocity dispersion and that this indicate the presence of old and metal-poor stellar halo. All the evidence so far for the halo, however, is from the spectroscopy of the inner LMC regions, similar to the inner flattened halo in our Galaxy. Further study is necessary to confirm this important result.

Explore related subjects

astro-ph

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

J. Borissova, D. Minniti, M. Rejkuba, D. Alves. 2006-09-07. Properties of RR Lyrae stars in the inner regions of the Large Magellanic Cloud. II. The extended sample. https://doi.org/10.1051/0004-6361%3A20054132

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Frame covariance of CMBR lensing in the exact 1+3 covariant radiation hierarchy

The exact $1+3$ covariant Boltzmann hierarchy for the cosmic microwave background contains acceleration, shear and vorticity couplings whose coefficients grow linearly in $\ell$. We show that all are the multipole form of the aberration operator in the photon Liouville equation. Under a change of threading, this operator shifts by the along-ray generator of a Lorentz boost. The acceleration coupling of $\ell$ to $\ell\pm1$ and the shear coupling of $\ell$ to $\ell\pm2$ are therefore frame-covariant descriptions of the same operator, related by an algebraic, pointwise relabelling of direction. With emitter and observer frames fixed, the observed sky is independent of the intermediate threading at every $\ell$. We derive this in $1+3$ covariant and gauge-invariant variables without constructing second-order gauge-invariant variables. The $O(ε^2\ell)$ content is gravitational lensing, as known in metric variables. Linearisation about a Friedmann--Lemaître--Robertson--Walker background removes these couplings, requiring lensing to be reinstated from the geodesic equation. Keeping the threading arbitrary makes frame covariance explicit and places observer aberration in the same operator. In the Newtonian threading we compute both halves of the deflection: the equivalence-principle contribution enters through aberration, while the spatial-curvature contribution arises from free streaming on perturbed spatial sections and reduces to the same operator. The lensing efficiency follows from the direction derivative. The angular-power-spectrum contribution is quartic in the potential: for a deflection statistically independent of the source, the two fourth-order terms carrying $\ell^2$ cancel where the spectrum is smooth on the deflection scale, and lensing redistributes power without adding ensemble variance.

astro-ph↗
arXiv2026

Cosmic Conundrums with Quantum Corrections

Darh energy was discovered over 25 years ago and we do not have an explanation of it. Dark matter comprises 95% of matter in the universe and we still don't know what it is. The Webb telescope has been finding fully formed galaxies with massive black holes millions of times the mass of the sun in the early universe and we don't have any explanation. A quantum density limitation will be used to solve these and other outstanding problems.

astro-ph↗
arXiv2026

On binary pulsars and the force of gravity

The energy-momentum budget of the astrophysical systems can be studied by the exact local conservation equation derived by Landau and Lifshitz. We show that a similar equation is valid for the Einstein-Cartan gravity. We reanalyze a binary pulsar system using the Landau-Lifshitz conservation equation and show that the orbital period change rate can be completely understood as a curvature backreaction process. Taking into account the detailed theoretical and observational research of relativistic binary pulsar systems, especially the system of Hulse and Taylor, we conclude that general relativity and astrophysical observations rule out the existence of gravitational radiation. We comment upon the LIGO GW events and their alternative explanation, as well as the recent pulsar timing arrays data.

astro-ph↗