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.

Galaxy And Mass Assembly (GAMA): improved cosmic growth measurements using multiple tracers of large-scale structure

Abstract: We present the first application of a ‘multiple-tracer’ redshift-space distortion (RSD) analysis to an observational galaxy sample, using data from the Galaxy and Mass Assembly (GAMA) survey. Our data set is an r < 19.8 magnitude-limited sample of 178 579 galaxies covering the redshift interval z < 0.5 and area 180 deg2. We obtain improvements of 10–20 per cent in measurements of the gravitational growth rate compared to a single-tracer analysis, deriving from the correlated sample variance imprinted in the distributions of the overlapping galaxy populations. We present new expressions for the covariances between the auto-power and cross-power spectra of galaxy samples that are valid for a general survey selection function and weighting scheme. We find no evidence for a systematic dependence of the measured growth rate on the galaxy tracer used, justifying the RSD modelling assumptions, and validate our results using mock catalogues from N-body simulations. For multiple tracers selected by galaxy colour, we measure normalized growth rates in two independent redshift bins fσ8(z = 0.18) = 0.36 ± 0.09 and fσ8(z = 0.38) = 0.44 ± 0.06, in agreement with standard GR gravity and other galaxy surveys at similar redshifts

Supernova 2002bo: inadequacy of the single parameter description

Abstract: We present optical photometry and optical/near-infrared spectra of the type Ia SN 2002bo spanning epochs from -13 days before maximum B-band light to +102 days after. The pre-maximum optical coverage is particularly complete. The extinction de- duced from the observed colour evolution and from interstellar NaID absorption is quite high viz. E(B V ) = 0.43 ± 0.10. On the other hand, model matches to the observed spectra point to a lower reddening (E(B V ) � 0.30). In some respects, SN 2002bo behaves as a typical "Branch normal" type Ia supernova (SN Ia) at opti- cal and IR wavelengths. We find a B-band risetime of 17.9±0.5 days, am15(B) of 1.13±0.05, and a de-reddened MB = 19.41±0.42. However, comparison with other type Ia supernovae having similarm15(B) values indicates that in other respects SN 2002bo is unusual. While the optical spectra of SN 2002bo are very similar to those of SN 1984A (�m15(B) = 1.19), lower velocities and a generally more structured ap- pearance are found in SNe 1990N, 1994D and 1998bu. For supernovae havingm15(B) > 1.2, we confirm the variation of R(SiII) (Nugent et al. 1995) withm15(B). How- ever, for supernovae such as SN 2002bo, with lower values ofm15(B) the relation breaks down. Moreover, the evolution of R(SiII) for SN 2002bo is strikingly differ- ent from that shown by other type Ia supernovae. The velocities of SN 2002bo and 1984A derived from SII 5640u SiII 6355u and CaII H&K lines are either much higher and/or evolve differently from those seen in other normal SNe Ia events. Thus, while SN 2002bo and SN 1984A appear to be highly similar, they exhibit behaviour which is distinctly different from other SNe Ia having similarm15(B) values. We suggest that the unusually low temperature, the presence of high-velocity intermediate-mass elements and the low abundance of carbon at early times indicates that burning to Si penetrated to much higher layers than in more normal type Ia supernovae. This may be indicative of a delayed-detonation explosion.

Searching for cool core clusters at high redshift

Abstract: Aims. We investigate the detection of Cool Cores (CCs) in the distant galaxy cluster population with the purpose of measuring the CC fraction out to redshift 0.7 ≤ z 0.7, and should also be related to the shorter age of distant clusters, implying less time to develop a cool core.

Mass-to-Light Ratios of Field Early-Type Galaxies at z ~ 1 from Ultradeep Spectroscopy: Evidence for Mass-dependent Evolution

Abstract: We present an analysis of the fundamental plane for a sample of 27 field early-type galaxies in the redshift range 0.6 0.95. The galaxies in this sample have high signal-to-noise ratio spectra obtained at the Very Large Telescope and high-resolution imaging from the HST Advanced Camera for Surveys. From comparison with lower redshift data, we find that the mean evolution of the mass-to-light ratio (M/L) of our sample is Delta 1n (M/LB) = (-1.74 +/- 0.16) z, with a large galaxy-to-galaxy scatter. The strong correlation between M/L and rest-frame color indicates that the observed scatter is not due to measurement errors, but due to intrinsic differences between the stellar populations of the galaxies, such that our results can be used as a calibration for converting luminosities of high-redshift galaxies into masses. This pace of evolution is much faster than the evolution of cluster galaxies. However, we find that the measured M/L evolution strongly depends on galaxy mass. For galaxies with masses M > 2 x 10(11) M circle dot, we find no significant difference between the evolution of field and cluster galaxies: Delta 1n (M/L-B) = (-1.20 +/- 0.18) z for field galaxies and Delta 1n (M/L-B) (-1.12 +/- 0.06) z for cluster galaxies. The relation between the measured M/ L evolution and mass is partially due to selection effects, as the galaxies are selected by luminosity, not mass. We calculate the magnitude of this effect for the subsample of galaxies with masses higher than M = 6 x 10(10) M circle dot: the uncorrected value of the evolution is Delta 1n (M/LB) (-1.54 +/- 0.16) z, whereas the corrected value is (-1.43 +/- 0.16) z. However, even when taking selection effects into account, we still find a relation between M/ L evolution and mass, which is most likely caused by a lower mean age and a larger intrinsic scatter for low-mass galaxies. Results from lensing early-type galaxies, which are mass selected, show a very similar trend with mass. This, combined with our findings, provides evidence for downsizing, i.e., for the proposition that low-mass galaxies are younger than high-mass galaxies. Previous studies of the rate of evolution of field early-type galaxies found a large range of mutually exclusive values. We show that these differences are largely caused by the differences between fitting methods: most literature studies are consistent with our result and with one another when using the same method. Finally, five of the early-type galaxies in our sample have AGNs. There is tentative evidence that the stellar populations in these galaxies are younger than those of galaxies without AGNs.

OGLE-2005-BLG-071Lb, THE MOST MASSIVE M DWARF PLANETARY COMPANION?

Abstract: We combine all available information to constrain the nature of OGLE-2005-BLG-071Lb, the second planet discovered by microlensing and the first in a high-magnification event. These include photometric and astrometric measurements from the Hubble Space Telescope, as well as constraints from higher order effects extracted from the ground-based light curve, such as microlens parallax, planetary orbital motion, and finite-source effects. Our primary analysis leads to the conclusion that the host of Jovian planet OGLE-2005-BLG-071Lb is an M dwarf in the foreground disk with mass M = 0.46 ± 0.04 Msun, distance Dl = 3.2 ± 0.4 kpc, and thick-disk kinematics vLSR ~ 103 km s‑1. From the best-fit model, the planet has mass Mp = 3.8 ± 0.4 MJupiter, lies at a projected separation r⊥ = 3.6 ± 0.2AU from its host, and so has an equilibrium temperature of T ~ 55 K, that is, similar to Neptune. A degenerate model gives similar planetary mass Mp = 3.4 ± 0.4 MJupiter with a smaller projected separation, r⊥ = 2.1 ± 0.1AU, and higher equilibrium temperature, T ~ 71 K. These results from the primary analysis suggest that OGLE-2005-BLG-071Lb is likely to be the most massive planet yet discovered that is hosted by an M dwarf. However, the formation of such high-mass planetary companions in the outer regions of M dwarf planetary systems is predicted to be unlikely within the core-accretion scenario. There are a number of caveats to this primary analysis, which assumes (based on real but limited evidence) that the unlensed light coincident with the source is actually due to the lens, that is, the planetary host. However, these caveats could mostly be resolved by a single astrometric measurement a few years after the event.