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.

Two distinct ancient components in the Sculptor dwarf spheroidal galaxy: First results from the dwarf abundances and radial velocities team

Abstract: We have found evidence for the presence of two distinct ancient stellar components (bothgreater than or equal to10 Gyr old) in the Sculptor dwarf spheroidal galaxy. We used the ESO Wide Field Imager in conjunction with the Very Large Telescope/FLAMES spectrograph to study the properties of the resolved stellar population of Sculptor out to and beyond the tidal radius. We find that two components are discernible in the spatial distribution of horizontal branch stars in our imaging and in the [Fe/H] and v(hel) distributions for our large sample of spectroscopic measurements. They can be generally described as a "metal-poor" component ([Fe/H]-1.7). The metal-poor stars are more spatially extended than the metal-rich stars, and they also appear to be kinematically distinct. These results provide insight into the formation processes of small systems in the early universe and the conditions found there. Even this simplest of galaxies appears to have had a surprisingly complex early evolution.

The Bulk of the Cosmic Infrared Background Resolved by ISOCAM

Abstract: Deep extragalactic surveys with ISOCAM revealed the presence of a large density of faint mid-infrared (MIR) sources. We have computed the 15m integrated galaxy light produced by these galaxies above a sensitivity limit of 50 Jy. It sets a lower limit to the 15m extragalactic background light of (2:4 0:5) nW m 2 sr 1 .T he redshift distribution of the ISOCAM galaxies is inferred from the spectroscopically complete sample of galaxies in the Hubble Deep Field North (HDFN). It peaks around z 0.8 in agreement with studies in other elds. The rest-frame 15m and bolometric infrared (8{1000m) luminosities of ISOCAM galaxies are computed using the correlations that we establish between the 6.75, 12, 15m and infrared (IR) luminosities of local galaxies. The resulting IR luminosities were double-checked using radio (1.4 GHz) flux densities from the ultra-deep VLA and WSRT surveys of the HDFN on a sample of 24 galaxies as well as on a sample of 109 local galaxies in common between ISOCAM and the NRAO VLA Sky Survey (NVSS). This comparison shows for the rst time that MIR and radio luminosities correlate up to z 1. This result validates the bolometric IR luminosities derived from MIR luminosities unless both the radio-far infrared (FIR) and the MIR-FIR correlations become invalid around z 1. The fraction of IR light produced by active nuclei was computed from the cross-correlation with the deepest X-ray surveys from the Chandra and XMM-Newton observatories in the HDFN and Lockman Hole respectively. We nd that at most 20% of the 15m integrated galaxy light is due to active galactic nuclei (AGNs) unless a large population of AGNs was missed by Chandra and XMM-Newton. About 75% of the ISOCAM galaxies are found to belong to the class of luminous infrared galaxies (LIR 10 11 L). They exhibit star formation rates of the order of100 M yr 1 . The comoving density of infrared light due to these luminous IR galaxies was more than 40 times larger at z 1 than today. The contribution of ISOCAM galaxies to the peak of the cosmic infrared background (CIRB) at 140m was computed from the MIR-FIR correlations for star forming galaxies and from the spectral energy distribution of the Seyfert 2, NGC 1068, for AGNs. We nd that the galaxies unveiled by ISOCAM surveys are responsible for the bulk of the CIRB, i.e. (16 5) nW m 2 sr 1 as compared to the (25 7) nW m 2 sr 1 measured with the COBE satellite, with less than 10% due to AGNs. Since the CIRB contains most of the light radiated over the history of star formation in the universe, this means that a large fraction of present-day stars must have formed during a dusty starburst event similar to those revealed by ISOCAM.

The HIPASS catalogue: ΩH i and environmental effects on the H i mass function of galaxies

Abstract: We use the catalogue of 4315 extragalactic HI 21-cm emission-line detections from the HI Parkes All Sky Survey (HIPASS) to calculate the most accurate measurement of the HI mass function (HIMF) of galaxies to date. The completeness of the HIPASS sample is well characterized, which enables an accurate calculation of space densities. The HIMF is fitted with a Schechter function with parameters α = -1.37 ± 0.03 ± 0.05, log(M*HIM⊙) = 9.80 ± 0.03 ± 0.03 h-275, and θ* = (6.0 ± 0.8 ± 0.6) × 10-3 h375 Mpc-3 dex-1 (random and systematic uncertainties at 68 per cent confidence limit), in good agreement with calculations based on the HIPASS Bright Galaxy Catalogue, which is a complete, but smaller, sub-sample of galaxies. The cosmological mass density of HI in the local Universe is found to be ωHI = (3.5 ± 0.4 ± 0.4) × I0-4h-175. This large homogeneous sample allows us to test whether the shape of the HIMF depends on local galaxy density. We find tentative evidence for environmental effects in the sense that the HIMF becomes steeper toward higher density regions, ranging from α ≈ - 1.2 in the lowest density environments to α ≈ - 1.5 in the highest density environments probed by this blind HI survey. This effect appears stronger when densities are measured on larger scales. © 2005 RAS.

Planck 2013 results. XVII. Gravitational lensing by large-scale structure

Abstract: On the arcminute angular scales probed by Planck, the cosmic microwave background (CMB) anisotropies are gently perturbed by gravitational lensing. Here we present a detailed study of this e_ect, detecting lensing independently in the 100, 143, and 217 GHz frequency bands with an overall significance of greater than 25_.We use the temperature-gradient correlations induced by lensing to reconstruct a (noisy) map of the CMB lensing potential, which provides an integrated measure of the mass distribution back to the CMB last-scattering surface. Our lensing potential map is significantly correlated with other tracers of mass, a fact which we demonstrate using several representative tracers of large-scale structure. We estimate the power spectrum of the lensing potential, finding generally good agreement with expectations from the best-fitting _CDM model for the Planck temperature power spectrum, showing that this measurement at z = 1100 correctly predicts the properties of the lower-redshift, latertime structures which source the lensing potential. When combined with the temperature power spectrum, our measurement provides degeneracy breaking power for parameter constraints; it improves CMB-alone constraints on curvature by a factor of two and also partly breaks the degeneracy between the amplitude of the primordial perturbation power spectrum and the optical depth to reionization, allowing a measurement of the optical depth to reionization which is independent of large-scale polarization data. Discarding scale information, our measurement corresponds to a 4% constraint on the amplitude of the lensing potential power spectrum, or a 2% constraint on the root-mean-squared amplitude of matter fluctuations at z _ 2.

Frequency of solar-like systems and of ice and gas giants beyond the snow line from high-magnification microlensing events in 2005-2008

Abstract: We present the first measurement of the planet frequency beyond the "snow line," for the planet-to-star mass-ratio interval –4.5 200) microlensing events during 2005-2008. The sampled host stars have a typical mass M_(host) ~ 0.5 M_⊙, and detection is sensitive to planets over a range of planet-star-projected separations (s ^(–1)_(max)R_E, s_(max)R_E), where R_E ~ 3.5 AU(M_(host)/M_⊙)^(1/2) is the Einstein radius and s_(max) ~ (q/10^(–4.3))^(1/3). This corresponds to deprojected separations roughly three times the "snow line." We show that the observations of these events have the properties of a "controlled experiment," which is what permits measurement of absolute planet frequency. High-magnification events are rare, but the survey-plus-follow-up high-magnification channel is very efficient: half of all high-mag events were successfully monitored and half of these yielded planet detections. The extremely high sensitivity of high-mag events leads to a policy of monitoring them as intensively as possible, independent of whether they show evidence of planets. This is what allows us to construct an unbiased sample. The planet frequency derived from microlensing is a factor 8 larger than the one derived from Doppler studies at factor ~25 smaller star-planet separations (i.e., periods 2-2000 days). However, this difference is basically consistent with the gradient derived from Doppler studies (when extrapolated well beyond the separations from which it is measured). This suggests a universal separation distribution across 2 dex in planet-star separation, 2 dex in mass ratio, and 0.3 dex in host mass. Finally, if all planetary systems were "analogs" of the solar system, our sample would have yielded 18.2 planets (11.4 "Jupiters," 6.4 "Saturns," 0.3 "Uranuses," 0.2 "Neptunes") including 6.1 systems with two or more planet detections. This compares to six planets including one two-planet system in the actual sample, implying a first estimate of 1/6 for the frequency of solar-like systems.