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 diameters of $\alpha$ Centauri A and B - A comparison of the asteroseismic and VINCI/VLTI views

Abstract: We compare the first direct angular diameter measurements obtained on our closest stellar neighbour, Centauri, to recent model diameters constrained by asteroseismic observations. Using the VINCI instrument installed at ESO's VLT Interferometer (VLTI), the angular diameters of the two main components of the system, Cen A and B, were measured with a relative precision of 0.2% and 0.6% respectively. Particular care has been taken in the calibration of these measurements, considering that VINCI is estimating the fringe visibility using a broadband K filter. We obtain uniform disk angular diameters for Cen A and B ofUD(A) = 8:314 0:016 mas andUD(B) = 5:856 0:027 mas, and limb darkened angular diameters ofLD(A)= 8:511 0:020 mas andLD(B)= 6:001 0:034 mas. Combining these values with the parallax from Soderhjelm (1999), we derive linear diameters of D(A)= 1:224 0:003 D and D(B)= 0:863 0:005 D. These values are compatible with the masses published by Thevenin et al. (2002) for both stars.

Detection of Rotation in a Binary Microlens: PLANET Photometry of MACHO 97-BLG-41*

Abstract: We analyze PLANET collaboration data for MACHO 97-BLG-41, the only microlensing event observed to date in which the source transits two disjoint caustics. The PLANET data, consisting of 46 V -band and 325 I-band observations from —ve southern observatories, span a period from the initial alert until the end of the event. Our data are incompatible with a static binary lens, but are well —tted by a rotating binary lens of mass ratio q \ 0.34 and angular separation d B 0.5 (in units of the Einstein ring radius), in which the binary separation changes in size by dd \( 0.070 ^ 0.009 and in orientation by during the 35.17 days between the separate caustic transits. We use this measurement, dh \ 5i.61^ 0i.36 combined with other observational constraints, to derive the —rst kinematic estimate of the mass, dis- tance, and period of a binary microlens. The relative probability distributions for these parameters peak at a total lens mass M D 0.3 (M-dwarf binary system), lens distance kpc, and binary period M _ D L D 5.5 P D 1.5 yr. The robustness of our model is demonstrated by its striking agreement with MACHO/ GMAN data that cover several sharp features in the light curve not probed by the PLANET obser- vations, and which did not enter our modeling procedure in any way. Available data sets thus indicate that the light curve of MACHO 97-BLG-41 can be modeled as a source crossing two caustics of a physi- cally realistic rotating binary. Thus, contrary to a recent suggestion, the additional eUects of a postulated planetary companion to the binary lens are not required. Subject headings: binaries: generalgravitational lensingplanetary systems

The Sins/zC-Sinf survey of z ~ 2 galaxy kinematics: evidence for powerful active galactic nucleus-driven nuclear outflows in massive star-forming galaxies

Abstract: We report the detection of ubiquitous powerful nuclear outflows in massive (≥1011 M ☉) z ~ 2 star-forming galaxies (SFGs), which are plausibly driven by an active galactic nucleus (AGN). The sample consists of the eight most massive SFGs from our SINS/zC-SINF survey of galaxy kinematics with the imaging spectrometer SINFONI, six of which have sensitive high-resolution adaptive optics-assisted observations. All of the objects are disks hosting a significant stellar bulge. The spectra in their central regions exhibit a broad component in Hα and forbidden [N II] and [S II] line emission, with typical velocity FWHM ~ 1500 km s–1, [N II]/Hα ratio ≈ 0.6, and intrinsic extent of 2-3 kpc. These properties are consistent with warm ionized gas outflows associated with Type 2 AGN, the presence of which is confirmed via independent diagnostics in half the galaxies. The data imply a median ionized gas mass outflow rate of ~60 M ☉ yr–1 and mass loading of ~3. At larger radii, a weaker broad component is detected but with lower FWHM ~485 km s–1 and [N II]/Hα ≈ 0.35, characteristic for star formation-driven outflows as found in the lower-mass SINS/zC-SINF galaxies. The high inferred mass outflow rates and frequent occurrence suggest that the nuclear outflows efficiently expel gas out of the centers of the galaxies with high duty cycles and may thus contribute to the process of star formation quenching in massive galaxies. Larger samples at high masses will be crucial in confirming the importance and energetics of the nuclear outflow phenomenon and its connection to AGN activity and bulge growth.

Abundant H(2)D+ in the pre-stellar core L1544

Abstract: We have detected the 372 GHz line of ortho-H2D + towards the pre-stellar core L1544. The strongest emission (Tmb1 K) occurs at the peak of the millimeter continuum emission, while measurements at oset positions indicate that H 2D + is confined within 20 00 , where CO is highly depleted. The derived H2D + abundance of10 9 is comparable with previous estimates of the electron abundance in the core, which suggests that H2D + is the main molecular ion in the central 20 00 (2800 AU) of L1544. This confirms the expectations that H 2D + is dramatically enhanced in gas depleted of molecules other than H2 .T he measured abundance even exceeds the present model predictions by about a factor ten. One possibility is that all CNO-bearing neutral species, including atomic oxygen, are almost completely (>98%) frozen within a radius of2800 AU.

Hubble Space Telescope and Ground-based Observations of Type Ia Supernovae at Redshift 0.5: Cosmological Implications

Abstract: We present observations of the Type Ia supernovae (SNe) 1999M, 1999N, 1999Q, 1999S, and 1999U, at redshift z ≈ 0.5. They were discovered in early 1999 with the 4.0 m Blanco telescope at Cerro Tololo Inter-American Observatory by the High-z Supernova Search Team (HZT) and subsequently followed with many ground-based telescopes. SNe 1999Q and 1999U were also observed with the Hubble Space Telescope. We computed luminosity distances to the new SNe using two methods and added them to the high-z Hubble diagram that the HZT has been constructing since 1995. The new distance moduli confirm the results of previous work. At z ≈ 0.5, luminosity distances are larger than those expected for an empty universe, implying that a "cosmological constant," or another form of "dark energy," has been increasing the expansion rate of the universe during the last few billion years. Combining these new HZT SNe Ia with our previous results and assuming a ΛCDM cosmology, we estimate the cosmological parameters that best fit our measurements. For a sample of 75 low-redshift and 47 high-redshift SNe Ia with MLCS2k2 (Jha and coworkers) luminosity calibration we obtain Ω_M = 0.79^(+0.15)_(-0.18) and Ω_Λ = 1.57^(+0.24)_(-0.32) (1 σ uncertainties) if no constraints are imposed, or Ω_M = 0.29^(+0.06)_(-0.05) if Ω_M + Ω_Λ = 1 is assumed. For a different sample of 58 low-redshift and 48 high-redshift SNe Ia with luminosity calibrations done using the PRES method (a generalization of the Δ_m_15 method), the results are Ω_M = 0.43^(+0.17)_(-0.19) and Ω_Λ = 1.18^(+0.27)_(-0.28) (1 σ uncertainties) if no constraints are imposed, or Ω_M = 0.18^(+0.05)_(-0.04) if Ω_M + Ω_Λ = 1 is assumed.