February 2002 arXiv papers — page 26

Claus Kiefer

This is a brief introduction to quantum aspects of black holes, addressed at an astrophysics-oriented audience. The topics are: The laws of black-hole mechanics, Hawking radiation, interpretation of entropy, and primordial black holes.

P. Jablonka, J. Gorgas, P. Goudfrooij

We have conducted a spectroscopic analysis of the bulges of a sample of 31 spiral galaxies, spanning the Hubble sequence from S0 to Scd type, in order to study the radial distribution of their stellar population properties.

E. M. Puchnarewicz, R. Soria

When Beppo-SAX measured the 0.1--12 keV spectrum of RE J1034+396, observations in the optical, UV and EUV were also taken within a few weeks. This multiwavelength spectrum placed very strong constraints on its unusually hot big blue bump component, which has been attributed to a high (almost Eddington) rate of accretion onto a disk surrounding a low mass bla

L. Boirin, A. N. Parmar, D. Lumb, M. Orlandini

We have observed the soft X-ray transient XTE J0421+56 in quiescence with XMM-Newton. The observed spectrum is highly unusual being dominated by a broad feature at 6.5 keV and can be modeled by a strongly absorbed continuum. The spectra of X-ray transients observed so far are normally modeled using Advection Dominated Accretion Flow models, black-bodies, pow

H. -Th. Janka

Supermassive black holes are now realized to exist in the centers of most galaxies. The recent discoveries of luminous quasars at redshifts higher than 6 require that these black holes were assembled already when the Universe was less than a billion years old. They might originate from the collapse of supermassive stars, a scenario which could ensure a suffi

M. Scodeggio, G. Gavazzi, P. Franzetti, A. Boselli

As a result of a systematic NIR H-band (1.65 micron) imaging survey of normal galaxies in the local universe, we are able to measure in a highly homogeneous way photometric and structural properties for a sample of 1143 galaxies. We base our analysis on a quantitative structural parameter, the concentration index C_31, instead of relying on the galaxies'

Mark J. McCaughrean, Morten Andersen

We present a deep, high spatial resolution (0.35 arcsec FWHM), near-infrared (1-2.5 micron) imaging survey of the Eagle Nebula, M16, made with the VLT, centred on the famous elephant trunks. We compare these data with the existing HST optical images to search for evidence of ongoing or recent star formation in the trunks, and in particular in the 73 small ev

Andreas Burkert, Frank C. van den Bosch, Rob A. Swaters

The puzzling correlation between the spin parameter lambda of galactic disks and the disk-to-halo mass fraction fdisk is investigated. We show that such a correlation arises naturally from uncertainties in determining the virial masses of dark matter halos. This result leads to the conclusion that the halo properties derived from fits to observed rotation cu

Alexandre Refregier, Tzu-Ching Chang, David Bacon

We present a new approach to measure the shapes of galaxies, a fundamental task in observational astronomy. This approach is based on the decomposition of a galaxy image into a series of orthogonal basis functions, or `shapelets'. Our choice of basis functions, namely the Gauss-Hermite series, has a number of remarkable properties under distortions, conv

Jesper Rasmussen, Kristian Pedersen, Martin Gotz

We present preliminary results from our on-going study: Comparing and optimizing source detection procedures for XMM images. By constructing realistic spatial and spectral source distributions and ``observing'' these through the XMM Science Simulator we study how source characteristics and instrumental effects influence detection. We are currently un

V. I. Dokuchaev, Yu. N. Eroshenko

To account for the microlensing events observed in the Galactic halo, Gurevich, Zybin, and Sirota have proposed a model of gravitationally bound, noncompact objects with masses of 0.01-1M_\odot. These objects are formed in the expanding Universe from adiabatic density perturbations and consist of weakly interacting particles of dark matter, for example, neut

Fabio Gastaldello, Silvano Molendi

We make a detailed measurement of the metal abundance profiles and metal abundance ratios of the inner core of M87/Virgo observed by XMM-Newton during the PV phase. We use multi temperature models for the inner regions and we compare the plasma codes APEC and MEKAL. We confirm the strong heavy elements gradient previously found by ASCA and BeppoSAX, but also

V. I. Dokuchaev, Yu. N. Eroshenko

We consider the cosmological model in which a part of the Universe Ω_h\sim 10^-5 is in the form of primordial black holes with mass \sim 10^5M_\odot. These primordial black holes would be centers for growing protogalaxies which experienced multiple mergers with ordinary galaxies. This process of galaxies formation is accompanied by the merging of central bla

Giovanni Carraro, Leo Girardi, Paola Marigo

We report on $UBVRI$ CCD photometry of two overlapping fields in the region of the intermediate-age open cluster NGC 2158 down to V=21. By analyzing Colour-Colour (CC) and Colour-Magnitude Diagrams (CMD) we infer a reddening $E_{B-V}= 0.55\pm0.10$, a distance of $3600 \pm 400$ pc, and an age of about 2 Gyr. Synthetic CMDs performed with these parameters (but

T. P. Roberts, M. R. Goad, M. J. Ward, R. S. Warwick

The advanced capabilities of the Chandra and XMM-Newton observatories mean that, for the first time, the detailed study of the brightest point-like X-ray sources in nearby galaxies outside of the local group is a realistic aim. Here, we present the results of a Chandra ACIS-S study of two of the nearest and brightest sources in the rare ultraluminous (L(X) >

V. K. Gupta, Vinita Tuli, Ashok Goyal

We study the effect of quark and nuclear matter mixed phase on the radial oscillation modes of neutron stars. For this study we have considered recent models from two classes of equations of state namely the relativistic mean field theoretical models and models based on realistic nucleon-nucleon interactions incorporating relativistic corrections and three b

Roberto Soria, Mat Page, Kinwah Wu

We carried out a multiwavelenght study of the black-hole candidate LMC X-3 with XMM-Newton. The system showed a transition to a low-hard state, in which the X-ray spectrum was well fitted by a simple power law. It then returned to a high-soft state, characterised by a strong disk-blackbody component. The line-of-sight absorption column density is <~ 4 x 10^{

Roberto Soria, Kinwah Wu

We have studied the face-on, barred spiral M83 (NGC 5236) with Chandra. Eighty-one point sources are detected (above 3.5-sigma) in the ACIS S3 image: 15 of them are within the inner 16 arcsec region (starburst nucleus, resolved for the first time with Chandra), and 23 within the inner 60 arcsec (including the bar). The luminosity distributions of the sources

Ivanio Puerari, Margarita Valdez-Gutierrez, Margarita Rosado

We have analyzed Halpha Fabry-Perot interferograms of NGC 5457 (M101) in order to calculate the rotation curve. We have also isolated a sample of 263 HII regions and we determined for each one its radial velocity and velocity dispersion. The rotation curve agrees with previous determinations and the mass derived from it is 9.8E10 solar mass. The distribution

K. Werner, J. L. Deetjen, S. Dreizler, T. Rauch

The determination of effective temperatures of very hot central stars (Teff>70000K) by model atmosphere analyses of optical H and He line profiles is afflicted with considerable uncertainty, primarily due to the lack of neutral helium lines. Ionization balances of metals, accessible only with UV lines, allow more precise temperature estimates. The potential

Aya Bamba, Hiroshi Murakami, Atsushi Senda, Shin-ichiro Takagi

This paper reports the diffuse X-ray features around the Galactic center observed with Chandra. We confirm the ASCA and Ginga discoveries of the large-scale thin-thermal plasma with strong lines in the Galactic center region. In addition, many small clumps of emission lines from neutral (6.4 keV line) to He-like (6.7 keV line) irons are discovered. The 6.4 k

Katsuji Koyama, Masaru Ueno, Aya Bamba, Ken Ebisawa

AX J1843.8-0352 is a new X-ray SNR identified to the radio complex G28.6-0.1 with the ASCA satellite. Chandra discovered two distinct components from this SNR: non-thermal and thin thermal X-ray emissions. The non-thermal component is fitted with a power-law spectrum of photon index 2.0. The morphology is complicated, but roughly an elliptical shape with a m

Michael S. Turner

Over the past three years we have determined the basic features of the Universe -- spatially flat; accelerating; comprised of 1/3 a new form of matter, 2/3 a new form of energy, with some ordinary matter and a dash of massive neutrinos; and apparently born from a burst of rapid expansion during which quantum noise was stretched to astrophysical size seeding

Michael S. Turner

Over the past three years we have determined the basic features of our Universe. It is spatially flat; accelerating; comprised of 1/3 a new form of matter, 2/3 a new form of energy, with some ordinary matter and a dash of massive neutrinos; and it apparently began from a great burst of expansion (inflation) during which quantum noise was stretched to astroph

Wendy L. Freedman

New, large, ground and space telescopes are contributing to an exciting and rapid period of growth in observational cosmology. The subject is now far from its earlier days of being data-starved and unconstrained, and new data are fueling a healthy interplay between observations and experiment and theory. I briefly review here the status of measurements of a