European Southern Observatory

About: European Southern Observatory is a facility organization based out in Garching bei München, Germany. It is known for research contribution in the topics: Galaxy & Stars. The organization has 3594 authors who have published 16157 publications receiving 823095 citations. The organization is also known as: The European Southern Observatory，ESO & ESO.

A correlation between the heavy element content of transiting extrasolar planets and the metallicity of their parent stars

Abstract: Context. Nine extrasolar planets with masses between 110 and 430M⊕ are known to transit their star. The knowledge of their masses and radii allows an estimate of their composition, but uncertainties on equations of state, opacities and possible missing energy sources imply that only inaccurate constraints can be derived when considering each planet separately. Aims. We seek to better understand the composition of transiting extrasolar planets by considering them as an ensemble, and by comparing the obtained planetary properties to that of the parent stars. Methods. We use evolution models and constraints on the stellar ages to derive the mass of heavy elements present in the planets. Possible additional energy sources like tidal dissipation due to an i nclined orbit or to downward kinetic energy transport are considered. Results. We show that the nine transiting planets discovered so far belong to a quite homogeneous ensemble that is characterized by a mass of heavy elements that is a relatively steep function of the s tellar metallicity, from less than 20 earth masses of heavy elements around solar composition stars, to up to∼ 100 M⊕ for three times the solar metallicity (the precise values be ing model-dependant). The correlation is still to be ascertained however. Statistical tests imply a worst-ca se 1/3 probability of a false positive. Conclusions. Together with the observed lack of giant planets in close orbits around metal-poor stars, these results appear to imply t hat heavy elements play a key role in the formation of close-in giant planets. The large masses of heavy elements inferred for planets orbiting metal rich stars was not anticipated by planet formation models and shows the need for alternative theories including migration and subsequent collection of planetesimals.

Galaxy and Mass Assembly (GAMA): the GAMA galaxy group catalogue (G3Cv1)

Abstract: Using the complete Galaxy and Mass Assembly I (GAMA-I) survey covering ∼142 deg2 to rAB= 194, of which ∼47 deg2 is to rAB= 198, we create the GAMA-I galaxy group catalogue (G3Cv1), generated using a friends-of-friends (FoF) based grouping algorithm Our algorithm has been tested extensively on one family of mock GAMA lightcones, constructed from Λ cold dark matter N-body simulations populated with semi-analytic galaxies Recovered group properties are robust to the effects of interlopers and are median unbiased in the most important respects G3Cv1 contains 14 388 galaxy groups (with multiplicity ≥2), including 44 186 galaxies out of a possible 110 192 galaxies, implying ∼40 per cent of all galaxies are assigned to a group The similarities of the mock group catalogues and G3Cv1 are multiple: global characteristics are in general well recovered However, we do find a noticeable deficit in the number of high multiplicity groups in GAMA compared to the mocks Additionally, despite exceptionally good local spatial completeness, G3Cv1 contains significantly fewer compact groups with five or more members, this effect becoming most evident for high multiplicity systems These two differences are most likely due to limitations in the physics included of the current GAMA lightcone mock Further studies using a variety of galaxy formation models are required to confirm their exact origin The G3Cv1 catalogue will be made publicly available as and when the relevant GAMA redshifts are made available at http://wwwgama-surveyorg

Extragalactic Results from the Infrared Space Observatory

Abstract: ▪ Abstract More than a decade ago the IRAS satellite opened the realm of external galaxies for studies in the 10 to 100 μm band and discovered emission from tens of thousands of normal and active galaxies With the 1995–1998 mission of the Infrared Space Observatory1, the next major steps in extragalactic infrared astronomy became possible: detailed imaging, spectroscopy, and spectrophotometry of many galaxies detected by IRAS, as well as deep surveys in the mid- and far-IR The spectroscopic data reveal a wealth of detail about the nature of the energy source(s) and about the physical conditions in galaxies ISO's surveys for the first time explore the infrared emission of distant, high-redshift galaxies ISO's main theme in extragalactic astronomy is the role of star formation in the activity and evolution of galaxies

Photometry and Spectroscopy of the Type IIP SN 1999em from Outburst to Dust Formation

Abstract: We present photometry and spectra of the Type IIP supernova 1999em in NGC 1637 from several days after the outburst till day 642. The radioactive tail of the recovered bolometric light curve of SN 1999em indicates that the amount of the ejected 5 6 Ni is 0.02 M O .. The Ha and HeI 10 830-A lines at the nebular epoch show that the distribution of the bulk of 5 6 Ni can be represented approximately by a sphere of 5 6 Ni with a velocity of 1500 km s - 1 , which is shifted towards the far hemisphere by about 400 km s - 1 . The fine structure of the Ha at the photospheric epoch reminiscent of the 'Bochum event' in SN 1987A is analysed in terms of two plausible models: bipolar 5 6 Ni jets and non-monotonic behaviour of the Ha optical depth combined with the one-sided 5 6 Ni ejection. The late-time spectra show a dramatic transformation of the [O I] 6300-A line profile between days 465 and 510, which we interpret as an effect of dust condensation during this period. Late-time photometry supports the dust formation scenario after day 465. The [O I] line profile suggests that the dust occupies a sphere with velocity 800 km s - 1 and optical depth >> 10. The latter exceeds the optical depth of the dusty zone in SN 1987A by more than 10 times. Use is made of the Expanding Photosphere Method to estimate the distance and the explosion time, D 7.83 Mpc and t 0 ≃ 1999 October 24.5 UT, in accord with observational constraints on the explosion time and with other results of detailed studies of the method. The plateau brightness and duration combined with the expansion velocity suggest a pre-supernova radius of 120-150 R O ., ejecta mass of 10-11 M O . and explosion energy of (0.5-1) x 10 5 1 erg. The ejecta mass combined with the neutron star and a conservative assumption about mass loss implies the main sequence progenitor of M m s 12-14 M O .. The derived mass range is in agreement with the upper limit to the mass found using pre-supernova field images by Smartt et al. From the [OI] 6300, 6364 A doublet luminosity we infer the oxygen mass to be a factor four lower than in SN 1987A which is consistent with the estimated SN 1999em progenitor mass according to nucleosynthesis and stellar evolution theory. We note a 'second-plateau' behaviour of the light curve after the main plateau at the beginning of the radioactive tail. This feature seems to be common to SNe IIP with low 5 6 Ni mass.

Resolving the complex structure of the dust torus in the active nucleus of the Circinus galaxy

Abstract: Aims. To test the dust torus model for active galactic nuclei directly, we study the extent and morphology of the nuclear dust distribution in the Circinus galaxy using high resolution interferometric observations in the mid-infrared. Methods. Observations were obtained with the MIDI instrument at the Very Large Telescope Interferometer. The 21 visibility points recorded are dispersed with a spectral resolution of λ/δλ ≈ 30 in the wavelength range from 8 to 13 µm. To interpret the data we used a stepwise approach of modelling with increasing complexity. The final model consists of two black body Gaussian distributions with dust extinction. Results. We find that the dust distribution in the nucleus of Circinus can be explained by two components, a dense and warm disk-like component of 0.4 pc size and a slightly cooler, geometrically thick torus component with a size of 2.0 pc. The disk component is oriented perpendicular to the ionisation cone and outflow and seems to show the silicate feature at 10 µm in emission. It coincides with a nuclear maser disk in orientation and size. From the energy needed to heat the dust, we infer a luminosity of the accretion disk of Lacc = 10 10 L� , which corresponds to 20% of the Eddington luminosity of the nuclear black hole. We find that the interferometric data are inconsistent with a simple, smooth and axisymmetric dust emission. The irregular behaviour of the visibilities and the shallow decrease of the dust temperature with radius provide strong evidence for a clumpy or filamentary dust structure. We see no evidence for dust reprocessing, as the silicate absorption profile is consistent with that of standard galactic dust. We argue that the collimation of the ionising radiation must originate in the geometrically thick torus component. Conclusions. Based on a great leap forward in the quality and quantity of interferometric data, our findings confirm the presence of a geometrically thick, torus-like dust distribution in the nucleus of Circinus, as required in unified schemes of Seyfert galaxies. Several aspects of our data require that this torus is irregular, or “clumpy”.