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 Evolution of AGN Host Galaxies: From Blue to Red and the Influence of Large-Scale Structures

Abstract: We present an analysis of 109 moderate-luminosity ( -->41.9 ≤ log L0.5–8.0 keV ≤ 43.7) AGNs in the Extended Chandra Deep Field-South survey, which is drawn from 5549 galaxies from the COMBO-17 and GEMS surveys having -->0.4 ≤ z≤ 1.1. These obscured or optically weak AGNs facilitate the study of their host galaxies since the AGNs provide an insubstantial amount of contamination to the galaxy light. We find that the color distribution of AGN host galaxies is highly dependent on (1) the strong color-evolution of luminous ( -->MV 0.63 ≤ z≤ 0.76, a regime dominated by sources in large-scale structures at -->z = 0.67 and -->z = 0.73, we observe a bimodality in the host galaxy colors. Galaxies hosting AGNs at -->z 0.8 preferentially have bluer (rest-frame -->U − V z 0.6 counterparts (many of which fall along the red sequence). The fraction of galaxies hosting AGNs peaks in the green valley ( -->0.5 0.63 ≤ z≤ 0.76. The AGN fraction in this redshift and color interval is 12.8% (compared to its field value of 7.8%) and reaches a maximum of 14.8% at -->U − V ~ 0.8. We further find that blue, bulge-dominated (Sersic index -->n > 2.5) galaxies have the highest fraction of AGN (21%) in our sample. We explore the scenario that the evolution of AGN hosts is driven by galaxy mergers and illustrate that an accurate assessment requires a larger area survey since only three hosts may be undergoing a merger with timescales 1 Gyr following a starburst phase.

The Northern HIPASS catalogue - data presentation, completeness and reliability measures

Abstract: The Northern HIPASS catalogue (NHICAT) is the northern extension of the HIPASS catalogue, HICAT. This extension adds the sky area between the declination (Dec.) range of +2 degrees 300 km s(-1). Sources with -300 < nu(hel) < 300 km s(-1) were excluded to avoid contamination by Galactic emission. In total, the entire HIPASS survey has found 5317 galaxies identified purely by their HI content. The full galaxy catalogue is publicly available at http://hipass.aus-vo.org.

Why do protoplanetary disks appear not massive enough to form the known exoplanet population

Abstract: When and how planets form in protoplanetary disks is still a topic of discussion. Exoplanet detection surveys and protoplanetary disk surveys are now providing results that are leading to new insights. We collect the masses of confirmed exoplanets and compare their dependence on stellar mass with the same dependence for protoplanetary disk masses measured in ∼1–3 Myr old star-forming regions. We recalculated the disk masses using the new estimates of their distances derived from Gaia DR2 parallaxes. We note that single and multiple exoplanetary systems form two different populations, probably pointing to a different formation mechanism for massive giant planets around very low-mass stars. While expecting that the mass in exoplanetary systems is much lower than the measured disk masses, we instead find that exoplanetary systems masses are comparable or higher than the most massive disks. This same result is found by converting the measured planet masses into heavy element content (core masses for the giant planets and full masses for the super-Earth systems) and by comparing this value with the disk dust masses. Unless disk dust masses are heavily underestimated, this is a big conundrum. An extremely efficient recycling of dust particles in the disk cannot solve this conundrum. This implies that either the cores of planets have formed very rapidly (<0.1–1 Myr) and a large amount of gas is expelled on the same timescales from the disk, or that disks are continuously replenished by fresh planet-forming material from the environment. These hypotheses can be tested by measuring disk masses in even younger targets and by better understanding if and how the disks are replenished by their surroundings.

The Ital-FLAMES survey of the Sagittarius dwarf spheroidal galaxy - I. Chemical abundances of bright RGB stars

Abstract: We present iron and α element (Mg, Ca, Ti) abundances for a sample of 15 Red Giant Branch stars belonging to the main body of the Sagittarius dwarf Spheroidal galaxy. Abundances have been obtained from spectra collected using the high resolution spectrograph FLAMES-UVES mounted at the VLT. Stars of our sample have a mean metallicity of [Fe/H] = -0.41 ± 0.20 with a metal-poor tail extending to [Fe/H] = -1.52. The α element abundance ratios are slightly subsolar for metallicities higher than [Fe/H]? -1, suggesting a slow star formation rate. The [α/Fe] of stars having [Fe/H] < -1 are compatible to what observed in Milky Way stars of comparable metallicity.

Directly determined linear radii and effective temperatures of exoplanet host stars

Abstract: We present interferometric angular sizes for 12 stars with known planetary companions, for comparison with 28 additional main-sequence stars not known to host planets. For all objects we estimate bolometric fluxes and reddenings through spectral-energy distribution (SED) fits, and in conjunction with the angular sizes, measurements of effective temperature. The angular sizes of these stars are sufficiently small that the fundamental resolution limits of our primary instrument, the Palomar Testbed Interferometer, are investigated at the sub-milliarcsecond level and empirically established based upon known performance limits. We demonstrate that the effective temperature scale as a function of dereddened (V − K)0 color is statistically identical for stars with and without planets. A useful byproduct of this investigation is a direct calibration of the TEFF scale for solarlike stars, as a function of both spectral type and (V − K)0 color, with an precision of ∆T (V−K)0 = 138 K over the range (V − K)0 = 0.0–4.0 and ∆T SpType = 105 K for the range F6V–G5V. Additionally, in an Appendix we provide SED fits for the 166 stars with known planets which have sufficient photometry available in the literature for such fits; this derived “XO-Rad” database includes homogeneous estimates of bolometric flux, reddening, and angular size.