Search Publications
The XMM-Newton Bright Serendipitous Survey: First Extragalactic Results
Wolter, Anna; Maccacaro, Tommaso; Braito, Valentina +3 more
We present here some initial results from the ongoing XMM-Newton bright serendipitous survey. The survey is aimed at selecting and spectroscopically identifying a large and statistically representative sample of bright (fx ≳ 7× 10‑14 c.g.s) serendipitous X-ray sources in the 0.5–4.5 keV energy band (BSS) and a complementary (…
Mid-Infrared properties of Early-type galaxies
Madden, S. C.; Vigroux, L.; Xilouris, E. M.
We have conducted a survey of early-type galaxies using the ISOCAMinstrument on board the Infrared Space Observatory (ISO)in order to probe their dustcontent. We present Mid-Infrared photometric properties for a sampleof 20 galaxies observed at 4.5, 7 and 15 µ$m. Using diagnosticcolor-color diagrams, we can delineate the different Mid-Infrar…
Galaxy Threshing and Ultra-Compact Dwarfs in the Fornax Cluster
Ferguson, Henry C.; Phillipps, Steven; Drinkwater, M. J. +3 more
We have discovered a new type of galaxy in the Fornax Cluster: `ultra-compact' dwarfs (UCDs). The UCDs are unresolved in ground-based imaging and have spectra typical of old stellar systems. Although the UCDs resemble overgrown globular clusters, based on VLT UVES echelle spectroscopy, they appear to be dynamically distinct systems with higher int…
The Sun's Distance from the Galactic Plane
Branham, R. L., Jr.
Use is made of 93,106 parallaxes from the Hipparcos catalog, with a mixture of spectrum-luminosity classes, to derive the position of the Galactic plane. The reduction technique, mixed total least squares-least squares, takes into account the errors in the parallaxes, and the condition that the direction cosines of the Galactic pole have unit Eucl…
Photometric study of the binary system NN Del
Gómez-Forrellad, J. M.; Sánchez-Bajo, F.; Corbera-Subirana, M. +2 more
We present the results of the differential V light curve analysis of NN Del. We show that NN Del is an EA eclipsing binary system with a period of 99.27 days and a highly eccentric orbit. Photometric solutions obtained using the Russell and the Wilson-Devinney models seem to indicate that both components are very similar in radii and luminosities …
Photometric studies of very metal-deficient blue compact dwarf galaxies: the exponential ionized gas halo of IZw18
Thuan, T. X.; Izotov, Y. I.; Papaderos, P. +4 more
Using HST and ground-based optical and NIR imaging data, we investigate whether the blue compact dwarf (BCD) galaxy I Zw 18 possesses an extended low-surface brightness (LSB) old stellar population underlying its star-forming (SF) regions. We show that the exponential intensity decrease observed in the filamentary LSB envelope of the BCD out to 18…
Tidal dwarfs in the M81 group: the second generation?
Sarajedini, A.; Geisler, D.; Guhathakurta, P. +8 more
We present a quantitative star formation history derivation of the four suspected tidal dwarf galaxies in the M 81 group: Holmberg IX, BK3N,Arp-loop (A0952+69) and Garland using HST/WFPC2 images of these galaxies. We construct a library of synthetic Colour-Magnitude Diagrams(CMDs) based on theoretical isochrones and data-derived determinations of …
The extended structure of the Phoenix dwarf galaxy
Aparicio, Antonio; Hidalgo, Sebastian L.; MartÍnez-Delgado, David
The surface brightness profile in the V band of the Phoenix dwarf galaxy shows two stellar components: an inner one, which contains all the young stars of the galaxy, and an outer one predominantly populated by red stars. Deep color-magnitude diagrams (CMDs), based on Hubble Space Telescope (HST) observations and reaching the oldest turn-offs, are…
The resolved red giant branches of E/S0 galaxies
Hopp, Ulrich; Schulte-Ladbeck, Regina E.; Drozdovsky, Igor O. +1 more
Formation paradigms for massive galaxies have long centered around two antipodal hypotheses – the monolithic-collapse and the accretion/merger scenarios. Empirical data on the stellar contents of galaxy halos is crucial in order to develop galaxy formation and assembly scenarios which have their root in observations, rather than in numerical simul…
Tests and constraints on theories of galaxy formation and evolution
Thompson, Rodger I.
Tests and constraints on current theories of galaxy formation and evolution are presented. They are derived from observations of the Northern Hubble Deep Field with WFPC2 and NICMOS. Photometric redshifts, extinctions and spectral energy distributions are calculated for all objects in the field. The tests and constraints are derived from the outpu…