Search Publications
Evolution since z = 1 of the Morphology-Density Relation for Galaxies
Smith, Graham P.; Treu, Tommaso; Ellis, Richard S. +2 more
We measure the morphology-density relation of galaxies at z=1 across the full 3 orders of magnitude in projected galaxy density available in low-redshift studies. Our study adopts techniques that are comparable with those applied at lower redshifts, allowing a direct investigation of how the morphological segregation of galaxies has evolved over t…
The unresolved hard X-ray background: the missing source population implied by the Chandra and XMM-Newton deep fields
Alexander, D. M.; Bauer, F. E.; Brandt, W. N. +6 more
We extend our earlier work on X-ray source stacking in the deep XMM-Newton observation of the Lockman Hole, to the 2-Ms Chandra Deep Field North (CDF-N) and the 1-Ms Chandra Deep Field South (CDF-S). The XMM-Newton work showed the resolved fraction of the X-ray background (XRB) to be ~80-100 per cent at <~ 2keV but this decreased to only ~50 pe…
INTEGRAL observations of recurrent fast X-ray transient sources
Hill, A. B.; Bird, A. J.; Ubertini, P. +9 more
Fast X-ray Transients (FXTs) are believed to be non-recurrent bright X-ray sources lasting less than a day and occuring at serendipitous positions, they can best be detected and discovered by instruments having a sufficiently wide field of view and high sensitivity. The IBIS/ISGRI instrument onboard INTEGRAL is particularly suited to detect new or…
A Deep Chandra Survey of the Globular Cluster 47 Tucanae: Catalog of Point Sources
Heinke, C. O.; Cohn, H. N.; Lugger, P. M. +5 more
We have detected 300 X-ray sources within the half-mass radius (2.79 arcmin) of the globular cluster 47 Tucanae in a deep (281 ks) Chandra exposure. We perform photometry and simple spectral fitting for our detected sources and construct luminosity functions, X-ray color-magnitude, and color-color diagrams. Eighty-seven X-ray sources show variabil…
Multicomponent decompositions for a sample of S0 galaxies
Salo, Heikki; Laurikainen, Eija; Buta, Ronald
We have estimated the bulge-to-total (B/T) light ratios in the Ks band for a sample of 24 S0, S0/a and Sa galaxies by applying a two-dimensional multicomponent decomposition method. For the disc an exponential function is used, the bulges are fitted by a Sérsic R1/n function and the bars and ovals are described either by a Sé…
How large are the bars in barred galaxies?
Erwin, Peter
I present a study of the sizes (semimajor axes) of bars in disc galaxies, combining a detailed R-band study of 65 S0-Sb galaxies with the B-band measurements of 70 Sb-Sd galaxies from Martin (1995). As has been noted before with smaller samples, bars in early-type (S0-Sb) galaxies are clearly larger than bars in late-type (Sc-Sd) galaxies; this is…
Local Helioseismology
Gizon, Laurent; Birch, Aaron C.
We review the current status of local helioseismology, covering both theoretical and observational results. After a brief introduction to solar oscillations and wave propagation through in-homogeneous media, we describe the main techniques of local helioseismology: Fourier-Hankel decomposition, ring-diagram analysis, time-distance helioseismology,…
Discovery of an X-Ray-luminous Galaxy Cluster at z=1.4
Böhringer, H.; Rosati, P.; Schwope, A. +4 more
We report the discovery of a massive, X-ray-luminous cluster of galaxies at z=1.393, the most distant X-ray-selected cluster found to date. XMMU J2235.3-2557 was serendipitously detected as an extended X-ray source in an archival XMM-Newton observation of NGC 7314. VLT FORS2 R- and z-band snapshot imaging reveals an overdensity of red galaxies in …
Super-Helium-rich Populations and the Origin of Extreme Horizontal-Branch Stars in Globular Clusters
Joo, Seok-Joo; Han, Sang-Il; Ree, Chang H. +7 more
Recent observations for the color-magnitude diagrams (CMDs) of the massive globular cluster ω Centauri have shown that it has a striking double main sequence (MS), with a minority population of bluer and fainter MS stars well separated from a majority population of MS stars. Here we confirm, with the most up-to-date Y2 isochrones, that …
Keck Spectroscopy of Distant GOODS Spheroidal Galaxies: Downsizing in a Hierarchical Universe
Treu, Tommaso; van Dokkum, Pieter G.; Ellis, Richard S. +1 more
We analyze the evolution of the fundamental plane for 141 field spheroidal galaxies in the redshift range 0.2<z<1.2, selected morphologically to a magnitude limit F850LP=22.43 in the northern field of the Great Observatories Origins Deep Survey. For massive galaxies, we find that the bulk of the star formation was completed prior to z=2. How…