The ESO Nearby Abell Cluster Survey VI. Spatial distribution and kinematics of early- and late-type galaxies

P. A. M. de Theije; P. Katgert

Home/Archive/arXiv

arXiv · astro-ph/9811199

The ESO Nearby Abell Cluster Survey VI. Spatial distribution and kinematics of early- and late-type galaxies

P. A. M. de Theije·P. Katgert

View original source ↗Read source document ↗Export metadata ↓

Abstract

We used the galaxy spectra obtained in the ESO Nearby Abell Cluster Survey (ENACS) to separate early- and late-type galaxies in the ENACS clusters, by applying a Principal Component Analysis (PCA) in combination with an Artificial Neural Network (ANN). We represented the spectra by 15 Principal Components, which form the input for the ANN. The latter was trained with morphological types from Dressler, and its success rate was estimated from an independent testing set of galaxies. The success-rate for an early- (E+S0) vs. late-type (Sp+Irr) classification is close to 75 %; somewhat higher for the early-type galaxies, and somewhat lower for the late-type galaxies. Using the results of the PCA/ANN analysis ('spectral' galaxy types for 3798 galaxies, 57 % of which are of early type and 43 % of late type) we constructed a composite cluster of 2594 galaxies. The late-type galaxies appear to have a larger line-of-sight velocity dispersion and are less centrally concentrated than the early-type galaxies. The late-type galaxies with emission lines (OII, H-beta, OIII) in their spectra are mostly responsible for this difference. The properties of the late-type galaxies without emission lines are more like those of the early-type galaxies than like those of the late-type galaxies with emission lines. The interpretation of the large velocity dispersion and the extended distribution, in terms of fairly radial (possibly 'first-approach') orbits is probably linked primarily to the presence of emission-line gas and much less to galaxy type.

Explore related subjects

astro-ph

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

P. A. M. de Theije, P. Katgert. 1998-11-12. The ESO Nearby Abell Cluster Survey VI. Spatial distribution and kinematics of early- and late-type galaxies. https://arxiv.org/abs/astro-ph/9811199

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↗