X-ray sources as tracers of the large-scale structure in the Universe

We review the current status of studies of large-scale structure in the X-ray Universe. After motivating the use X-rays for cosmological purposes, we discuss the various approaches used on different angular scales including X-ray background multipoles, cross-correlations of the X-ray background with galaxy catalogues, clustering of X-ray selected sources and small-scale fluctuations and anisotropies in the X-ray background. We discuss the implications of the above studies for the bias parameter of X-ray sources, which is likely to be moderate for X-ray selected AGN and the X-ray background (~1-2). We finally outline how all-sky X-ray maps at hard X-rays and medium surveys with large sky coverage could provide important tests for the cosmological models.Comment: Invited review presented at the Workshop X-ray Astronomy'99: Stellar endpoints, AGN and the diffuse X-ray background (Astrophys Lett and Comm

H1320+551: A Seyfert 1.8/1.9 galaxy with an unabsorbed X-ray spectrum

We present new optical spectroscopic and XMM-Newton X-ray observations of the Active Galactic Nucleus H1320+551. The optical data (consistent with but of better quality than a previously published spectrum) show this source to be a Seyfert 1.8/1.9 galaxy at z=0.0653. The narrow line region is significantly reddened, with a Balmer decrement Ha/Hb~6 and the broad line region, with a barely detectable Hb broad component, shows a much pronnounced Balmer decrement (Ha/Hb>27). In spite of this, the EPIC-pn X-ray spectrum exhibits a power-law continuum with a soft excess that is well fitted by a black body, with no photoelectric absorption above the Galactic value. A Fe K emission line is also seen at a rest-frame energy ~6.5 keV with an equivalent width of ~400 eV, far too weak for the source being Compton-thick. Reconciling the optical and X-ray data requires the narrow line region being internally reddened but with small covering factor over the nuclear emission and the Balmer decrement of the broad line region being an intrinsic property rather than caused by reddening/absorption. The H1320+551 Seyfert 1.8/1.9 galaxy is not consistent with being an obscured Seyfert 1 nucleus, i.e., it does not match the basic AGN unified scheme hypothesis.Comment: 9 pages, 9 eps figures, to appear in MNRA

The Damping Tail of CMB Anisotropies

By decomposing the damping tail of CMB anisotropies into a series of transfer functions representing individual physical effects, we provide ingredients that will aid in the reconstruction of the cosmological model from small-scale CMB anisotropy data. We accurately calibrate the model-independent effects of diffusion and reionization damping which provide potentially the most robust information on the background cosmology. Removing these effects, we uncover model-dependent processes such as the acoustic peak modulation and gravitational enhancement that can help distinguish between alternate models of structure formation and provide windows into the evolution of fluctuations at various stages in their growth.Comment: 24pgs, aaspp4, 10 figs. included; supporting material (e.g. color figures) at http://www.sns.ias.edu/~whu/pub.htm

Zygomycosis in Two Hematologic Cases

Zygomycosis are invasive mould infections, rarely diagnosed in hematologic patients. Most of the cases published are in patients with prolonged neutropenia, along with other risk factors such as the use of prior broad-spectrum antibiotics (including new antifungal agents, such as voriconazole), diabetes mellitus (with or without ketoacidosis), malnutrition, iron overload (with or without the use of deferoxamine). These infections have poor prognosis due to the involvement of vital anatomic structures and late diagnosis. Until recent years, the treatment was based on high doses of amphotericin B plus surgical debridement. Here we present two patients with hematologic diseases (one with leukemia, the second with aplastic anemia) with an impaired immune system and the diagnosis of zygomycosis. The survival of one of them was mainly due to early diagnosis and surgical debridement; unfortunately the second was misdiagnosed as an extensive ecchymosis due to thrombocytopenia and died with CNS involvement

HST Observations of the Serendipitous X-ray Companion to Mrk 273: Cluster at z=0.46?

We have used HST I-band images to identify Mrk 273X, the very unusual high-redshift X-ray-luminous Seyfert 2 galaxy found by ROSAT in the same field-of-view as Mrk 273. We have measured the photometric properties of Mrk 273X and have also analyzed the luminosity distribution of the faint galaxy population seen in the HST image. The luminosity of the galaxy and the properties of the surrounding environment suggest that Mrk 273X is the brightest galaxy in a relatively poor cluster at a redshift near 0.46. Its off-center location in the cluster and the presence of other galaxy groupings in the HST image may indicate that this is a dynamically young cluster on the verge of merging with its neighboring clusters. We find that Mrk 273X is a bright featureless elliptical galaxy with no evidence for a disk. It follows the de Vaucouleurs (r^{1/4}) surface brightness law very well over a range of 8 magnitudes. Though the surface brightness profile does not appear to be dominated by the AGN, the galaxy has very blue colors that do appear to be produced by the AGN. Mrk 273X is most similar to the IC 5063 class of active galaxies --- a hybrid Sy 2 / powerful radio galaxy.Comment: Accepted for publication in the Astrophysical Journal. 8 pages, including 4 postscript figures. Uses emulateapj.sty and psfig.sty. Higher quality version of Figure 1 is available at http://rings.gsfc.nasa.gov/~borne/fig1-markgals.gi