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.

High-resolution UVES/VLT spectra of white dwarfs observed for the ESO SN Ia progenitor survey (SPY). I. ?;??

Abstract: We have started a large survey for radial velocity variations in white dwarfs (PI R. Napiwotzki) with the aim of nding close double degenerates, which could be precursor systems for SNe Ia. The UVES spectrograph at the ESO VLT is used to obtain high resolution spectra with good S=N. During this project 1500 white dwarfs will be observed. This unique data set will also allow to derive atmospheric parameters and masses for the largest sample of white dwarfs ever analyzed in a homogenous way. In this paper we present a catalog of objects and report results for the rst sample of about 200 white dwarfs, many of which are spectroscopic conrmations of candidates from the HE, MCT, and EC surveys. Among the peculiar spectra we identify two new magnetic DA, one previously known magnetic DA, several DA with emission cores, in some cases due to a late-type companion, and two new DBA.

A spectroscopic atlas of the HgMn star HD 175640 (B9 V) $\lambda\lambda$ 3040–10 000 Å

Abstract: We present a high resolution spectral atlas of the HgMn star HD 175640 covering the 3040-10000 A region. UVES spectra observed with 90 000-110 000 resolving power and signal to noise ratio ranging from 200 to 400 are compared with a synthetic spectrum computed with the SYNTHE code (Kurucz 1993b). The model atmosphere is an ATLAS 12 model (Kurucz 1997) with parameters Ten = 12 000 K, log g = 3.95, ξ = 0 km s -1 . The stellar individual abundances in ATLAS 12 were derived from an iterative procedure. The starting atomic line lists downloaded from the Kurucz website have been improved and extended by examining different sources in the literature and by comparing the computed profiles with the observed spectrum. The high quality of the data allowed us to study the isotopic and hyperfine structure for several lines of Mn II, Ga II, Ba II, Pt II, Hg i, and Hg II. Numerous weak emission lines from Cr II and Ti II have been identified in the red part of the spectrum, starting at λ 5847 A. Two emission lines of C (mult. 10, mult. 9) have been observed for the first time. All Cr II and Ti II emission lines originate from the high excitation states (X low A 89 000 cm -1 for CrII and X low ≥ 62000 cm -1 for Ti II ) with large transition probabilities (log gf > -1.00). The synthetic spectrum superimposed on the observed spectrum as well as the adopted improved atomic line lists are available at the CDS and http://wwwuser.oat.ts.astro.it/castelli/stars.html.An extended discussion on each identified ion and related atomic data is available both on the quoted website and in an electronic Appendix to the paper.

Planck intermediate results - XI. The gas content of dark matter halos: the Sunyaev-Zeldovich-stellar mass relation for locally brightest galaxies

Abstract: We present the scaling relation between Sunyaev-Zeldovich (SZ) signal and stellar mass for almost 260,000 locally brightest galaxies (LBGs) selected from the Sloan Digital Sky Survey (SDSS). These are predominantly the central galaxies of their dark matter halos. We calibrate the stellar-to-halo mass conversion using realistic mock catalogues based on the Millennium Simulation. Applying a multi-frequency matched filter to the Planck data for each LBG, and averaging the results in bins of stellar mass, we measure the mean SZ signal down to M-* similar to 2 x 10(11) M-circle dot, with a clear indication of signal at even lower stellar mass. We derive the scaling relation between SZ signal and halo mass by assigning halo properties from our mock catalogues to the real LBGs and simulating the Planck observation process. This relation shows no evidence for deviation from a power law over a halo mass range extending from rich clusters down to M-500 similar to 2 x 10(13) M-circle dot, and there is a clear indication of signal down to M-500 similar to 4 x 10(12) M-circle dot. Planck's SZ detections in such low-mass halos imply that about a quarter of all baryons have now been seen in the form of hot halo gas, and that this gas must be less concentrated than the dark matter in such halos in order to remain consistent with X-ray observations. At the high-mass end, the measured SZ signal is 20 % lower than found from observations of X-ray clusters, a difference consistent with the magnitude of Malmquist bias effects that were previously estimated for the X-ray sample.

Molecular excitation and differential gas-phase depletions in the ic 5146 dark cloud

Abstract: We present a combined near-infrared and molecular line study of a 25' × 8' area in the northern streamer of the IC 5146 cloud. Using the technique pioneered by Lada and coworkers, we construct a Gaussian-smoothed map of the infrared extinction with the same resolution as the molecular line observations in order to examine correlations of integrated intensities and molecular abundances with extinction for C17O, C34S, and N2H+. We find that over a visual extinction range of 0-40 mag, there is good evidence for the presence of differential gas-phase depletions in the densest portions of IC 5146. Both CO and CS exhibit a statistically significant (factor of ~3) abundance reduction near AV ~ 12 mag, while, in direct contrast, at the highest extinctions (AV > 10 mag), N2H+ appears relatively undepleted. Moreover, for AV < 4 mag, there exists little or no N2H+. This pattern of depletions is consistent with the predictions of chemical theory. Through the use of a time- and depth-dependent chemical model, we show that the near-uniform or rising N2H+ abundance with extinction is a direct result of a reduction in its destruction rate at high extinction because of the predicted and observed depletion of CO molecules. The observed abundance threshold for N2H+, A ~ 4 mag, is examined in the context of this same model, and we demonstrate how this technique can be used to test the predictions of depth-dependent chemical models. Finally, we find that cloud density gradients can have a significant effect on the excitation and detectability of high dipole moment molecules, which are typically far from local thermodynamic equilibrium. Density gradients also cause chemical changes since reaction rates and depletion timescales are density-dependent. Accounting for such density/excitation gradients is crucial to a correct determination and proper interpretation of molecular abundances.

Planck intermediate results: XXIX. All-sky dust modelling with Planck, IRAS, and WISE observations

Abstract: We present all-sky modelling of the high resolution Planck, IRAS, and WISE infrared (IR) observations using the physical dust model presented by Draine & Li in 2007 (DL, ApJ, 657, 810). We study the performance and results of this model, and discuss implications for future dust modelling. The present work extends the DL dust modelling carried out on nearby galaxies using Herschel and Spitzer data to Galactic dust emission. We employ the DL dust model to generate maps of the dust mass surface density ΣMd, the dust optical extinction AV, and the starlight intensity heating the bulk of the dust, parametrized by Umin. The DL model reproduces the observed spectral energy distribution (SED) satisfactorily over most of the sky, with small deviations in the inner Galactic disk and in low ecliptic latitude areas, presumably due to zodiacal light contamination. In the Andromeda galaxy (M31), the present dust mass estimates agree remarkably well (within 10%) with DL estimates based on independent Spitzer and Herschel data. We compare the DL optical extinction AV for the diffuse interstellar medium (ISM) with optical estimates for approximately 2 × 105 quasi-stellar objects (QSOs) observed inthe Sloan Digital Sky Survey (SDSS). The DL AV estimates are larger than those determined towards QSOs by a factor of about 2, which depends on Umin. The DL fitting parameter Umin, effectively determined by the wavelength where the SED peaks, appears to trace variations in the far-IR opacity of the dust grains per unit AV, and not only in the starlight intensity. These results show that some of the physical assumptions of the DL model will need to be revised. To circumvent the model deficiency, we propose an empirical renormalization of the DL AV estimate, dependent of Umin, which compensates for the systematic differences found with QSO observations. This renormalization, made to match the AV estimates towards QSOs, also brings into agreement the DL AV estimates with those derived for molecular clouds from the near-IR colours of stars in the 2 micron all sky survey (2MASS). The DL model and the QSOs data are also used to compress the spectral information in the Planck and IRAS observations for the diffuse ISM to a family of 20 SEDs normalized per AV, parameterized by Umin, which may be used to test and empirically calibrate dust models. The family of SEDs and the maps generated with the DL model are made public in the Planck Legacy Archive.