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.

The K20 survey. I. Disentangling old and dusty star-forming galaxies in the ERO population

Abstract: We present the results of VLT optical spectroscopy of a complete sample of 78 EROs with R-Ks\geq5 over a field of 52 arcmin^2. About 70% of the 45 EROs with Ks\leq19.2 have been spectroscopically identified with old passively evolving and dusty star-forming galaxies at 0.7

Spatially Resolved Millimeter Interferometry of SMM J02399–0136: A Very Massive Galaxy at z = 2.8*

Abstract: We report high-resolution millimeter mapping with the IRAM Plateau de Bure interferometer of rest-frame 335 ?m continuum and CO (3-2) line emission from the z = 2.8 submillimeter galaxy SMM J02399-0136. The continuum emission comes from a ~3'' diameter structure whose elongation is approximately east-west and whose centroid is coincident within the astrometric errors with the brightest X-ray and rest-UV peak (L1). The line data show that this structure is most likely a rapidly rotating disk. Its rotation velocity of ?420 km s-1 implies a total dynamical mass of ?3 ? 1011 sin?2 i h M? within an intrinsic radius of 8 h kpc, most of which is plausibly in the form of stars and gas. SMM J02399-0136 is thus a very massive system, whose formation at z ~ 3 is not easy to understand in current cold dark matter hierarchical merger cosmogonies.

The TRAPPIST survey of southern transiting planets. I. Thirty eclipses of the ultra-short period planet WASP-43 b

Abstract: We present twenty-three transit light curves and seven occultation light curves for the ultra-short period planet WASP -43 b, in addition to eight new measurements of the radial velocity of the star. Thanks to this extensive data set, we improve significantly t he parameters of the system. Notably, the largely improved precision on the stellar density (2.41± 0.08ρ⊙) combined with constraining the age to be younger than a Hubble time allows us to break the degeneracy of the stellar solution mentioned in the discovery paper. The resulting stellar mass and size are 0.717± 0.025 M⊙ and 0.667± 0.011 R⊙. Our deduced physical parameters for the planet are 2.034± 0.052 MJup and 1.036± 0.019 RJup. Taking into account its level of irradiation, the high dens ity of the planet favors an old age and a massive core. Our deduced orbital eccentricity, 0.0035 +0.0060 −0.0025 , is consistent with a fully circularized orbit. We detect th e emission of the planet at 2.09µm at better than 11-σ, the deduced occultation depth being 1560± 140 ppm. Our detection of the occultation at 1.19µm is marginal (790± 320 ppm) and more observations are needed to confirm it. We pla ce a 3-σ upper limit of 850 ppm on the depth of the occultation at∼0.9µm. Together, these results strongly favor a poor redistribu tion of the heat to the night-side of the planet, and marginally favor a model with no day-side temperature inversion.

The mean magnetic field modulus of Ap stars

Abstract: We present new measurements of the mean magnetic field modulus of a sample of Ap stars with spectral lines resolved into magnetically split components. We report the discovery of 16 new stars having this property. This brings the total number of such stars known to 42. We have performed more than 750 measurements of the mean field modulus of 40 of these 42 stars, between May 1988 and August 1995. The best of them have an estimated accuracy of . The availability of such a large number of measurements allows us to discuss for the first time the distribution of the field modulus intensities. A most intriguing result is the apparent existence of a sharp cutoff at the low end of this distribution, since no star with a field modulus (averaged over the rotation period) smaller than 2.8 kG has been found in this study. For more than one third of the studied stars, enough field determinations well distributed throughout the stellar rotation cycle have been achieved to allow us to characterize at least to some extent the variations of the field modulus. These variations are often significantly anharmonic, and it is not unusual for their extrema not to coincide in phase with the extrema of the longitudinal field (for the few stars for which enough data exist about the latter). This, together with considerations on the distribution of the relative amplitude of variation of the studied stars, supports the recently emerging evidence for markedly non-dipolar geometry and fine structure of the magnetic fields of most Ap stars. New or improved determinations of the rotation periods of 9 Ap stars have been achieved from the analysis of the variations of their mean magnetic field modulus. Tentative values of the period have been derived for 5 additional stars, and lower limits have been established for 10 stars. The shortest definite rotation period of an Ap star with magnetically resolved lines is 34, while those stars that rotate slowest appear to have periods in excess of 70 or 75 years. As a result of this study, the number of known Ap stars with rotation periods longer than 30 days is almost doubled. We briefly rediscuss the slow-rotation tail of the period distribution of Ap stars. This study also yielded the discovery of radial velocity variations in 8 stars. There seems to be a deficiency of binaries with short orbital periods among Ap stars with magnetically resolved lines.

Hubble Space Telescope ACS Multiband Coronagraphic Imaging of the Debris Disk around β Pictoris

Abstract: We present F435W (B), F606W (broad V), and F814W (broad I) coronagraphic images of the debris disk around β Pictoris obtained with the Hubble Space Telescope's Advanced Camera for Surveys. These images provide the most photometrically accurate and morphologically detailed views of the disk between 30 and 300 AU from the star ever recorded in scattered light. We confirm that the previously reported warp in the inner disk is a distinct secondary disk inclined by ~5° from the main disk. The projected spine of the secondary disk coincides with the isophotal inflections, or "butterfly asymmetry," previously seen at large distances from the star. We also confirm that the opposing extensions of the main disk have different position angles, but we find that this "wing-tilt asymmetry" is centered on the star rather than offset from it, as previously reported. The main disk's northeast extension is linear from 80 to 250 AU, but the southwest extension is distinctly bowed with an amplitude of ~1 AU over the same region. Both extensions of the secondary disk appear linear, but not collinear, from 80 to 150 AU. Within ~120 AU of the star, the main disk is ~50% thinner than previously reported. The surface brightness profiles along the spine of the main disk are fitted with four distinct radial power laws between 40 and 250 AU, while those of the secondary disk between 80 and 150 AU are fitted with single power laws. These discrepancies suggest that the two disks have different grain compositions or size distributions. The F606W/F435W and F814W/F435W flux ratios of the composite disk are nonuniform and asymmetric about both projected axes of the disk. The disk's northwest region appears 20%-30% redder than its southeast region, which is inconsistent with the notion that forward scattering from the nearer northwest side of the disk should diminish with increasing wavelength. Within ~120 AU, the m_(F435W) - m_(F606W) and m_(F435W) - m_(F814W) colors along the spine of the main disk are ~10% and ~20% redder, respectively, than those of β Pic. These colors increasingly redden beyond ~120 AU, becoming 25% and 40% redder, respectively, than the star at 250 AU. These measurements overrule previous determinations that the disk is composed of neutrally scattering grains. The change in color gradient at ~120 AU nearly coincides with the prominent inflection in the surface brightness profile at ~115 AU and the expected water-ice sublimation boundary. We compare the observed red colors within ~120 AU with the simulated colors of nonicy grains having a radial number density ∝r^(-3) and different compositions, porosities, and minimum grain sizes. The observed colors are consistent with those of compact or moderately porous grains of astronomical silicate and/or graphite with sizes ≳ 0.15-0.20 μm, but the colors are inconsistent with the blue colors expected from grains with porosities ≳ 90%. The increasingly red colors beyond the ice sublimation zone may indicate the condensation of icy mantles on the refractory grains, or they may reflect an increasing minimum grain size caused by the cessation of cometary activity.