Search results for "GALAXIES"
showing 10 items of 341 documents
Outflows from AGN: Kinematics of the Narrow-Line and Coronal-Line Regions in Seyfert Galaxies
2011
As part of an extensive study of the physical properties of active galactic nuclei (AGN) we report high spatial resolution near-IR integral-field spectroscopy of the narrow-line region (NLR) and coronal-line region (CLR) of seven Seyfert galaxies. These measurements elucidate for the first time the two-dimensional spatial distribution and kinematics of the recombination line Br{\gamma} and high-ionization lines [Sivi], [Alix] and [Caviii] on scales <300 pc from the AGN. The observations reveal kinematic signatures of rotation and outflow in the NLR and CLR. The spatially resolved kinematics can be modeled as a combination of an outflow bicone and a rotating disk coincident with the molecula…
Sub-parsec scale imaging of Centaurus A
2010
At a distance of about 3.8 Mpc, the radio galaxy Centaurus A is the closest active galaxy. Therefore it is a key target for studying the innermost regions of active galactic nuclei (AGN). VLBI observations conducted within the framework of the TANAMI program enable us to study the central region of the Cen A jet with some of the highest linear resolutions ever achieved in an AGN. This region is the likely origin of the gamma-ray emission recently detected by the Fermi Large Area Telescope (LAT). TANAMI monitors a sample of radio and gamma-ray selected extragalactic jets south of -30 degrees declination at 8.4 GHz and 22.3 GHz with the Australian Long Baseline Array (LBA) and the transoceani…
The GLASS-JWST Early Release Science Program. III. Strong lensing model of Abell 2744 and its infalling regions
2023
We present a new high-precision, JWST-based, strong lensing model for the galaxy cluster Abell 2744 at $z=0.3072$. By combining the deep, high-resolution JWST imaging from the GLASS-JWST and UNCOVER programs and a Director's Discretionary Time program, with newly obtained VLT/MUSE data, we identify 32 multiple images from 11 background sources lensed by two external sub-clusters at distances of ~160" from the main cluster. The new MUSE observations enable the first spectroscopic confirmation of a multiple image system in the external clumps. Moreover, the re-analysis of the spectro-photometric archival and JWST data yields 27 additional multiple images in the main cluster. The new lens mode…
Relic galaxies: Where are they?
2016
The finding that massive galaxies grow with cosmic time fired the starting gun for the search of objects which could have survived up to the present day without suffering substantial changes (neither in their structures, neither in their stellar populations). Nevertheless, and despite the community efforts, up to now only one firm candidate to be considered one of these relics is known: NGC 1277. Curiously, this galaxy is located at the centre of one of the most rich near galaxy clusters: Perseus. Is its location a matter of chance? Should relic hunters focus their search on galaxy clusters? In order to reply this question, we have performed a simultaneous and analogous analysis using simul…
The influence of stellar objects mass distribution on their gravitational fields
2019
We study the influence of the astronomical objects masses randomness on the distribution function of their gravitational fields. Based on purely theoretical arguments and comparison with extensive data, collected from observations and numerical simulations, we have shown that while mass randomness does not alter the non-Gaussian character of the gravitational fields distribution, it changes the dependencies of mean angular momenta of galaxies and clusters on their richness. The specific form of above dependence is determined by the interplay of mass distribution character and different assumptions about cluster morphology. We trace the influence of masses distribution on the time evolution …
Some observational aspects of the orientation of galaxies
2011
We investigated the sample of galaxies belonging to the Tully groups of galaxies. We analyzed the orientation of galaxies inside the group. We did not found significant deviation from isotropy both in orientation of position angles and angles $\delta_D$ and $\eta$ giving the spatial orientation of galaxy planes. Moreover we analyzed consequences of different approximation of "true shape" of galaxies and showed possible influence of this problem for investigation of spatial orientation of galaxies. Implications of the obtained results for theory of galaxy formation was discussed as well.
The large-scale environment from cosmological simulations II: The redshift evolution and distributions of baryons
2019
Following Cui et al. 2018 (hereafter Paper I) on the classification of large-scale environments (LSE) at z = 0, we push our analysis to higher redshifts and study the evolution of LSE and the baryon distributions in them. Our aim is to investigate how baryons affect the LSE as a function of redshift. In agreement with Paper I, the baryon models have negligible effect on the LSE over all investigated redshifts. We further validate the conclusion obtained in Paper I that the gas web is an unbiased tracer of total matter -- even better at high redshifts. By separating the gas mainly by temperature, we find that about 40 per cent of gas is in the so-called warm-hot intergalactic medium (WHIM). …
Limits on the Mass and Abundance of Primordial Black Holes from Quasar Gravitational Microlensing
2017
The idea that dark matter can be made of intermediate-mass primordial black holes in the $10M_\odot \lesssim M \lesssim 200M_\odot$ range has recently been reconsidered, particularly in the light of the detection of gravitational waves by the LIGO experiment. The existence of even a small fraction of dark matter in black holes should nevertheless result in noticeable quasar gravitational microlensing. Quasar microlensing is sensitive to any type of compact objects in the lens galaxy, to their abundance, and to their mass. We have analyzed optical and X-ray microlensing data from 24 gravitationally lensed quasars to estimate the abundance of compact objects in a very wide range of masses. We…
Radio data and synchrotron emission in consistent cosmic ray models
2011
It is well established that phenomenological two-zone diffusion models of the galactic halo can very well reproduce cosmic-ray nuclear data and the observed antiproton flux. Here, we consider lepton propagation in such models and compute the expected galactic population of electrons, as well as the diffuse synchrotron emission that results from their interaction with galactic magnetic fields. We find models in agreement not only with cosmic ray data but also with radio surveys at essentially all frequencies. Requiring such a globally consistent description strongly disfavors very large ($L\gtrsim 15$ kpc) and, even stronger, small ($L\lesssim 1$ kpc) effective diffusive halo sizes. This has…
Wavelet analysis of baryon acoustic structures in the galaxy distribution
2011
Baryon Acoustic Oscillations (BAO) are a feature imprinted in the density field by acoustic waves travelling in the plasma of the early universe. Their fixed scale can be used as a standard ruler to study the geometry of the universe. BAO have been previously detected using correlation functions and power spectra of the galaxy distribution. In this work, we present a new method for the detection of the real-space structures associated with this feature. These baryon acoustic structures are spherical shells with a relatively small density contrast, surrounding high density central regions. We design a specific wavelet adapted to the search for shells, and exploit the physics of the process b…