Search results for "Extragalactic astronomy"
showing 10 items of 39 documents
XMM-Newton survey of the ELAIS-S1 field
2008
The formation and evolution of cosmic structures can be probed by studying the evolution of the luminosity function of the Active Galactic Nuclei (AGNs), galaxies and clusters of galaxies and of the clustering of the X-ray active Universe, compared to the IR-UV active Universe. To this purpose, we have surveyed with XMM-Newton the central ~0.6{deg}^2^ region of the ELAIS-S1 field down to flux limits of ~5.5x10^-16^erg/cm^2^/s (0.5-2keV, soft band, S), ~2x10^-15^erg/cm^2^/s (2-10keV, hard band, H), and ~4x10^-15^erg/cm^2^/s (5-10keV, ultra hard band, HH). We present here the analysis of the XMM-Newton observations, the number counts in different energy bands and the clustering properties of …
Sgr A* 1.3mm VLBI observations with the EHT in 2013
2019
We report results from very long baseline interferometric (VLBI) observations of the supermassive black hole in the Galactic center, Sgr A*, at 1.3mm (230GHz). The observations were performed in 2013 March using six VLBI stations in Hawaii, California, Arizona, and Chile. Compared to earlier observations, the addition of the APEX telescope in Chile almost doubles the longest baseline length in the array, provides additional uv coverage in the N-S direction, and leads to a spatial resolution of ~30 {mu}as (~3 Schwarzschild radii) for Sgr A*. The source is detected even at the longest baselines with visibility amplitudes of ~4%-13% of the total flux density. We argue that such flux densities …
CIG 96 deep optical and HI images
2018
Asymmetries in atomic hydrogen (HI) in galaxies are often caused by the interaction with close companions, making isolated galaxies an ideal framework to study secular evolution. The AMIGA project has demonstrated that isolated galaxies show the lowest level of asymmetry in their HI integrated profiles compared to even field galaxies, yet some present significant asymmetries. CIG 96 (NGC 864) is a representative case reaching a 16% level. Our aim is to investigate the HI asymmetries of the spiral galaxy CIG 96 and what processes have triggered the star-forming regions observed in the XUV pseudo-ring. We performed deep optical observations at CAHA1.23m, CAHA2.2m and VST (OmegaCAM wide-field …
REMARKS ON THE METHODS OF INVESTIGATIONS OF ALIGNMENT OF GALAXIES
2011
In the 1975 Hawley and Peebles gave the proposal to use three statistical tests for investigations of the galaxies orientation in the large structures. Nowadays, it has been considered as the standard method of searching for galactic alignments. In the present paper we analyzed the tests in details and proposed a few improvements. Basing on the improvements, the new method of analysis of the alignment of galaxies in clusters is proposed. The power of this method is demonstrated on the sample of 247 Abell clusters with at least 100 objects in each. The distributions of the position angles for galaxies in each cluster are analyzed using statistical tests: $\chi^2$, Fourier, autocorrelation an…
Intracluster Medium reheating by relativistic jets
2011
Galactic jets are powerful energy sources reheating the intra-cluster medium in galaxy clusters. Their crucial role in the cosmic puzzle, motivated by observations, has been established by a great number of numerical simulations missing the relativistic nature of these jets. We present the first relativistic simulations of the very long term evolution of realistic galactic jets. Unexpectedly, our results show no buoyant bubbles, but large cocoon regions compatible with the observed X-ray cavities. The reheating is more efficient and faster than in previous scenarios, and it is produced by the shock wave driven by the jet, that survives for several hundreds of Myrs. Therefore, the X-ray cavi…
Pinpointing the SMBH in NGC1052
2016
Supermassive black holes (SMBH) are essential for the production of jets in radio-loud active galactic nuclei (AGN). Theoretical models based on Blandford & Znajek (1977MNRAS.179..433B) extract the rotational energy from a Kerr black hole, which could be the case for NGC1052, to launch these jets. This requires magnetic fields on the order of 1000G to 10000G. We imaged the vicinity of the SMBH of the AGN NGC1052 with the Global Millimetre VLBI Array and found a bright and compact central feature that is smaller than 1.9 light days (100 Schwarzschild radii) in radius. Interpreting this as a blend of the unresolved jet bases, we derive the magnetic field at 1 Schwarzschild radius to lie betwe…
Sub-milliarcsecond imaging of 3C111
2020
Flares in radio-loud active galactic nuclei (AGNs) are thought to be associated with the injection of fresh plasma into the compact jet base. Such flares are usually strongest and appear earlier at shorter radio wavelengths. Hence, very long baseline interferometry (VLBI) at millimeter (mm)-wavelengths is the best-suited technique for studying the earliest structural changes of compact jets associated with emission flares. Aims. We study the morphological changes of the parsec-scale jet in the nearby (z=0.049) gamma-ray bright radio galaxy 3C 111 following a flare that developed into a major radio outburst in 2007. We analyse three successive observations of 3C 111 at 86 GHz with the Global…
MOJAVE. VI. Kinematic analysis of blazar jets
2012
We discuss the jet kinematics of a complete flux-density-limited sample of 135 radio-loud active galactic nuclei (AGNs) resulting from a 13 year program to investigate the structure and evolution of parsec-scale jet phenomena. Our analysis is based on new 2cm Very Long Baseline Array (VLBA) images obtained between 2002 and 2007, but includes our previously published observations made at the same wavelength, and is supplemented by VLBA archive data. In all, we have used 2424 images spanning the years 1994-2007 to study and determine the motions of 526 separate jet features in 127 jets. Cone search capability for table J/AJ/138/1874/agn (AGN sample)
22GHz image of 3C 273
2017
RadioAstron is a 10m orbiting radio telescope mounted on the Spektr-R satellite, launched in 2011, performing Space Very Long Baseline Interferometry (SVLBI) observations supported by a global ground array of radio telescopes. With an apogee of ~350000km, it is offering for the first time the possibility to perform as-resolution imaging in the cm-band. The RadioAstron Active Galactic Nuclei (AGN) polarization Key Science Project (KSP) aims at exploiting the unprecedented angular resolution provided by RadioAstron to study jet launching/collimation and magnetic-field configuration in AGN jets. The targets of our KSP are some of the most powerful blazars in the sky. We present observations at…
REFLEX Galaxy Cluster Survey catalogue
2004
We present the catalogue of the REFLEX Cluster Survey providing information on the X-ray properties, redshifts, and some identification details of the clusters in the REFLEX sample. The catalogue describes a statistically complete X-ray flux-limited sample of 447 galaxy clusters above an X-ray flux of 3x10^-12^erg/s/cm^2^ (0.1 to 2.4keV) in an area of 4.24ster in the southern sky. The cluster candidates were first selected by their X-ray emission in the ROSAT-All Sky Survey and subsequently spectroscopically identified in the frame of an ESO key programme. Previously described tests have shown that the sample is more than 90% complete and there is a conservative upper limit of 9% on the fra…