The nuclear radio structure of X-ray bright AGN

The physical nature of the X-ray/radio correlation of AGN is still an unsolved question. High angular resolution observations are necessary to disentangle the associated energy dynamics into nuclear and stellar components. We present MERLIN/EVN 18cm observations of 13 X-raying AGN. The sample consists of Seyfert 1, Narrow Line Seyfert 1, and LINER-like galaxies. We find that for all objects the radio emission is unresolved and that the radio luminosities and brightness temperatures are too high for star formation to play an important role. This indicates that the radio emission in these sources is closely connected to processes that occur in the vicinity of the central massive black hole, also where the X-ray emission is believed to originate in.Comment: 5 pages, 3 figures, submitted to "The Universe under the Microscope - Astrophysics at High Angular Resolution", Bad Honnef, German

Near infrared imaging of the broad absorption line quasar BAL QSO 0134+3253

In this paper we present near infrared (NIR) imaging data of the host galaxy of the broad absorption line quasar (BALQ) at z=2.169, serendipitously found close to 3C48. The data were obtained with the ESO-VLT camera ISAAC during period 67. We find extended, rest-frame optical emission around the BALQ after subtracting a scaled stellar point spread function from the quasar nucleus in J, H, and Ks. The extended rest-frame optical emission can be interpreted as an approximately 2 Gyr old stellar population composing the host galaxy of the BALQ or a stellar population of similar age associated with an intermediate (z=1.667) absorption system spectroscopically identified by Canalizo & Stockton (1998) simultaneously. The rest-frame-UV emission on the other hand is dominated by a young, 500 Myr old stellar population. The UV/optical colors resemble a mixture of the two populations, of which the young one accounts for about 80%. Assuming that the residual emission is located at the BALQ redshift, we find that the host galaxy has a resolved flux of about 10% of the BALQ flux. The physical scale is quite compact, typical for radio quiet QSOs or Lyman break galaxies at these redshifts, indicating that the systems are still in the process of forming.Comment: 14 pages, referee style, 6 figures, 4 tables, accepted for publication in A&

The nuclear radio structure of X-ray bright AGN

The physical nature of the X-ray/radio correlation of AGN is still an unsolved question. High angular resolution observations are necessary to disentangle the associated energy dynamics into nuclear and stellar components. We present MERLIN/EVN 18cm observations of 13 X-raying AGN. The sample consists of Seyfert 1, Narrow Line Seyfert 1, and LINER-like galaxies. We find that for all objects the radio emission is unresolved and that the radio luminosities and brightness temperatures are too high for star formation to play an important role. This indicates that the radio emission in these sources is closely connected to processes that occur in the vicinity of the central massive black hole, also where the X-ray emission is believed to originate in.Comment: 5 pages, 3 figures, submitted to "The Universe under the Microscope - Astrophysics at High Angular Resolution", Bad Honnef, German

The nuclear radio structure of X-ray bright AGN

The physical nature of the X-ray/radio correlation of AGN is still an unsolved question. High angular resolution observations are necessary to disentangle the associated energy dynamics into nuclear and stellar components. We present MERLIN/EVN 18cm observations of 13 X-raying AGN. The sample consists of Seyfert 1, Narrow Line Seyfert 1, and LINER-like galaxies. We find that for all objects the radio emission is unresolved and that the radio luminosities and brightness temperatures are too high for star formation to play an important role. This indicates that the radio emission in these sources is closely connected to processes that occur in the vicinity of the central massive black hole, also where the X-ray emission is believed to originate in.Comment: 5 pages, 3 figures, submitted to "The Universe under the Microscope - Astrophysics at High Angular Resolution", Bad Honnef, German

Compact radio emission from z~0.2 X-ray bright AGN

Radio and X-ray emission of AGN appears to be correlated. The details of the underlying physical processes, however, are still not fully understood, i.e., to what extent is the X-ray and radio emission originating from the same relativistic particles or from the accretion-disk or corona or both. We study the cm radio emission of an SDSS/ROSAT/FIRST matched sample of 13 X-raying AGN in the redshift range 0.11< z < 0.37 at high angular resolution with the goal of searching for jet structures or diffuse, extended emission on sub-kpc scales. We use MERLIN at 18 cm for all objects and Western EVN at 18 cm for four objects to study the radio emission on scales of ~500 pc and ~40 pc for the MERLIN and EVN observations, respectively. The detected emission is dominated by compact nuclear radio structures. We find no kpc collimated jet structures. The EVN data indicate for compact nuclei on 40 pc scales, with brightness temperatures typical for accretion-disk scenarios. Comparison with FIRST shows that the 18 cm emission is resolved out up to 50% by MERLIN. Star-formation rates based on large aperture SDSS spectra are generally too small to produce considerable contamination of the nuclear radio emission. We can, therefore, assume the 18 cm flux densities to be produced in the nuclei of the AGN. Together with the ROSAT soft X-ray luminosities and black hole mass estimates from the literature, our sample objects follow closely the Merloni et al. (2003) fundamental plane relation, which appears to trace the accretion processes. Detailed X-ray spectral modeling from deeper hard X-ray observations and higher angular resolution at radio wavelengths are required to further proceed in the disentangling of jet and accretion related processes.Comment: 15 pages, 7 figures, submitted to A&

Dissecting the host galaxies of Active Galactic Nuclei at high angular resolution

The work presented here is concerned with issues related to the interplay of galaxy structure and the accretion phenomenon onto supermassive black holes (SMBH), i.e. active galactic nuclei (AGN). There is statistical evidence for a coevolution of SMBHs and the galaxy bulges they reside in. The detailed knowledge of the involved physical processes, however, is still far from being satisfactory. In order to test and improve theoretical models of how this coevolution is arising, high angular resolution observations of the host galaxies of AGN are necessary. Imaging and spectroscopy of the innermost region of galaxies have the power to reveal information on the structure, the chemical composition, and the dynamics of stars and gas in the presence of an SMBH, and allow us to separate energetic signatures related either to star formation or to the accretion onto the SMBH. Considering such observations over cosmological distances (redshifts) -- i.e. looking into the past because of the finite light-travel time -- we are also able to assess evolutionary effects on the beforementioned properties. Such types of observations have now become possible with the advent of adaptive optics (AO) systems, which overcome the limitations of angular resolution imposed by the Earth's turbulent atmosphere. The first part of this thesis presents methods to derive samples of galaxies, suitable for high angular resolution studies. These samples are based on large area sky surveys at different wavelengths, since only panchromatic information allows us to select samples homogeneously for detailed follow-up observations. The main focus lies on visible (Sloan Digital Sky Survey) and X-ray (ROSAT All Sky Survey) wavelengths. Within the framework of the (German Astrophysical) Virtual Observatory [(GA)VO], such large databases can be mined efficiently. From a sample of X-ray bright AGN, near-infrared, AO-assisted, spatially-resolved spectroscopy of an AGN with SINFONI at the Very Large Telescope (European Southern Observatory, ESO) will be presented. In particular, the results show the importance of star formation/SMBH feedback in terms of nuclear outflows that have been uncertain from previous coarse multiwavelength survey observations. These observations of X-raying AGN will be complemented by the near-infrared imaging study of a high redshift (when the Universe was only about one quarter of its present age) AGN with ISAAC at the ESO VLT. The host galaxy of this bright AGN appears to be an example of the class of objects, known to be the progenitors of the population of present-day most massive elliptical galaxies. This places nuclear activity and and massive galaxies in an evolutionary context

Ends in digraphs

AbstractIn this paper a sort of end concept for directed graphs is introduced and examined. Two one-way infinite paths are called equivalent iff there are infinitely many pairwise disjoint paths joining them. An end of an undirected graph is an equivalence class with respect to this relation. For two one-way infinite directed paths U and V define: (a) U⩽V iff there are infinitely many pairwise disjoint directed paths from U to V; (b) U ∼ V iff U ⩽ V and V ⩽ U. The relation ⩽ is a quasiorder, and hence ∼ is an equivalence relation whose classes are called ends. Furthermore, ⩽ induces a partial order on the set of ends of a digraph. In the main section, necessary and sufficient conditions are presented for an abstract order to be representable by the end order of a digraph

An anti-CD30 immunocytokine with combined IL-2 and IL-12 domains enhances anti-tumour immunity

Classical Hodgkin’s lymphoma is one of the most curable cancers today. However, non-responders, tumour relapses and long-term toxicities of the treatment make it necessary to look for alternative drugs. In this study, we have generated a novel immunocytokine that aims to overcome the misguided TH2 immune response in Hodgkin’s lymphoma by targeting CD30 on the surface of the malignant Hodgkin-Reed-Sternberg cells, and by combining IL-2 and IL-12 domains in one molecule. This immunocytokine induces resting natural killer cells to specific lysis of CD30⁺ tumour cells, exhibits superior cytokine activity compared to immunocytokines with a single cytokine domain, and inhibits tumour growth in immunocompetent mice