Search Publications
Low-luminosity active galactic nuclei: are they UV faint and radio loud?
Maoz, Dan
Low-luminosity active galactic nuclei (AGNs) are perceived to be radio loud and devoid of a `big blue bump', indicating a transition from a radiatively efficient, geometrically thin, accretion disc in high-luminosity AGNs, to a geometrically thick, radiatively inefficient accretion flow at low luminosities and accretion rates. I revisit the issue …
Magnetic hydrogen atmosphere models and the neutron star RX J1856.5-3754
Ho, Wynn C. G.; Kaplan, David L.; Chang, Philip +2 more
RX J1856.5-3754 is one of the brightest nearby isolated neutron stars (INSs), and considerable observational resources have been devoted to it. However, current models are unable to satisfactorily explain the data. We show that our latest models of a thin, magnetic, partially ionized hydrogen atmosphere on top of a condensed surface can fit the en…
Discovery of multiple Lorentzian components in the X-ray timing properties of the Narrow Line Seyfert 1 Ark 564
Papadakis, I. E.; Page, M. J.; Uttley, P. +4 more
We present a power spectral analysis of a 100-ks XMM-Newton observation of the Narrow Line Seyfert 1 galaxy Ark 564. When combined with earlier RXTE and ASCA observations, these data produce a power spectrum covering seven decades of frequency which is well described by a power law with two very clear breaks. This shape is unlike the power spectra…
The properties and evolution of a K-band selected sample of massive galaxies at z ~ 0.4-2 in the Palomar/DEEP2 survey
Papovich, C.; Georgakakis, A.; Nandra, K. +11 more
We present the results of a study on the properties and evolution of massive (M* > 1011Msolar) galaxies at z ~ 0.4-2 utilizing Keck spectroscopy, near-infrared Palomar imaging, and Hubble, Chandra and Spitzer data covering fields targeted by the DEEP2 galaxy spectroscopic survey. Our sample is K-band selected an…
TeV light curve of PSR B1259-63/SS2883
Aharonian, F.; Khangulyan, D.; Hnatic, S. +1 more
The inverse Compton (IC) scattering of ultrarelativistic electrons accelerated at the pulsar wind termination shock is generally believed to be responsible for TeV gamma-ray signal recently reported from the binary system PSR B1259-63/SS2883. While this process can explain the energy spectrum of the observed TeV emission, the gamma-ray fluxes dete…
Lyman-break galaxies at z ~ 5 - I. First significant stellar mass assembly in galaxies that are not simply z ~ 3 LBGs at higher redshift
Lehnert, Matthew D.; Förster Schreiber, Natascha M.; Bremer, Malcolm N. +2 more
We determine the ensemble properties of z ~ 5 Lyman-break galaxies (LBGs) selected as V-band dropouts to iAB < 26.3 in the Chandra Deep Field-South using their rest-frame UV-to-visible spectral energy distributions. By matching the selection and performing the same analysis that has been used for z ~ 3 samples, we show clear differen…
Kinematics and stellar populations of the dwarf elliptical galaxy IC 3653
Afanasiev, V. L.; Chilingarian, I. V.; Sil'Chenko, O. K. +1 more
We present the first 3D observations of a diffuse elliptical galaxy (dE). The good quality data (S/N up to 40) reveal the kinematical signature of an embedded stellar disc, reminiscent of what is commonly observed in elliptical galaxies, though similarity of their origins is questionable. Colour map built from Hubble Space Telescope Advanced Camer…
High-resolution imaging of the anomalous flux ratio gravitational lens system CLASS B2045+265: dark or luminous satellites?
McKean, J. P.; Blandford, R. D.; Thompson, D. +6 more
The existence of flux ratio anomalies between fold and cusp images in galaxy-scale strong-lens systems has led to an interpretation based on the presence of a high mass fraction of cold dark matter (CDM) substructures around galaxies, as predicted by numerical N-body simulations. These substructures can cause large perturbations of the image magni…
The effect of stellar-mass black holes on the structural evolution of massive star clusters
Davies, M. B.; Mackey, A. D.; Wilkinson, M. I. +1 more
We present the results of realistic N-body modelling of massive star clusters in the Magellanic Clouds, aimed at investigating a dynamical origin for the radius-age trend observed in these systems. We find that stellar-mass black holes, formed in the supernova explosions of the most massive cluster stars, can constitute a dynamically important pop…
Hierarchical star formation in M33: fundamental properties of the star-forming regions
Bastian, N.; Gutermuth, R.; Gieles, M. +4 more
Star formation within galaxies appears on multiple scales, from spiral structure, to OB associations, to individual star clusters, and often substructure within these clusters. This multitude of scales calls for objective methods to find and classify star-forming regions, regardless of spatial size. To this end, we present an analysis of star-form…