A BeppoSAX observation of the z=2.34 quasar PKS2149−306 produced a strong signal in the high energy PDS instrument up to a maximum observed energy of nearly 50 keV, 150 keV in the quasar frame. The Beppo-SAX spectrum spans almost 3 decades (0.3−150 keV, quasar frame) and shows an extremely hard (α=0.4±0.05) X-ray spectrum above 3 keV (comparable to XJB the X-ray background slope), and either a ...

We have derived the quasar luminosity function assuming that the quasar activity is driven by a thermal-viscous unstable accretion disk around a supermassive black hole. The instabilities produce large amplitude, long-term variability of a single source. We take a light curve of a single source and calculate the luminosity function, from the function of time it spends at each luminosity. Convol...

We study the link between quasars and the red galaxy population using a model for the self-regulated growth of supermassive black holes in mergers involving gas-rich galaxies. In this picture, mergers drive nuclear inflows of gas, fueling starbursts and obscured quasars until feedback energy from black hole growth expels the surrounding gas, rendering the quasar briefly visible as a bright opti...

We present an evolutionary model for starbursts, quasars, and spheroidal galaxies in which the growth of supermassive black holes plays a dominant role. In this picture, mergers between gas-rich galaxies drive nuclear inflows of gas, producing intense starbursts and feeding the growth of supermassive black holes. During this phase, the black hole is heavily obscured (a “buried” quasar), but fee...

The red quasar 3C212 (z = 1.049) is one of the most distant and most luminous AGN which has shown evidence of an X-ray warm absorber. In order to further investigate this unusual quasar, we used Chandra/ACIS-S to observe 3C212 for 19.5 ksec, resulting in a net detection of ∼ 4000 counts. The Chandra data confirm the presence of an excess absorbing column NH ≈ 4 × 10 21 cm at the quasar redshift...

We investigate the host galaxy and environment properties of a sample of 400 low z (<0.5) quasars that were imaged in the SDSS Stripe82. We can detect and study the properties of the host galaxy for more than 75% of the data sample. We discover that quasar are mainly hosted in luminous galaxies of absolute magnitude M − 3 < M(R) < M∗1 and that in the quasar environments the galaxy number densit...

As storage capacities increase, finding and organizing data becomes increasingly challenging. Conventional approaches to organization for file systems fail to effectively provide for the needs of petascale storage, because hierarchical namespaces do not scale and must rely on ad hoc utilities. Previous solutions do not incorporate relationships as search terms, nor were they designed for today’...

Your thesaurus codes are: missing; you have not inserted them ASTRONOMY AND ASTROPHYSICS The first XMM-Newton spectrum of a high redshift quasar-PKS 0537−286. Abstract. We present XMM-Newton observations of the high redshift (z = 3.104), radio-loud quasar PKS 0537−286. The EPIC CCD cameras provide the highest signal-to-noise spectrum of a high-z quasar to date. The EPIC observations show that P...

We investigate the environments of quasars such as number distribution of galaxies using a semi-analytic model which includes both galaxy and quasar formations based on the hierarchical clustering scenario. We assume that a supermassive black hole is fueled by accretion of cold gas and that it is a source of quasar activity during a major merger of the quasar host galaxy with another galaxy. Th...

We present an investigation of quasar colour-redshift parameter space in order to search for radio-quiet red quasars and to test the ability of a variant of the KX quasar selection method to detect quasars over a full range of colour without bias. This is achieved by combining IRIS2 imaging with the complete Fornax Cluster Spectroscopic Survey to probe parameter space unavailable to other surve...