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 optically unbiased gamma-ray burst host (tough) survey. I. Survey design and catalogs

Abstract: Long-duration gamma-ray bursts (GRBs) are powerful tracers of star-forming galaxies. We have defined a homogeneous subsample of 69 Swift GRB-selected galaxies spanning a very wide redshift range. Special attention has been devoted to making the sample optically unbiased through simple and well-defined selection criteria based on the high-energy properties of the bursts and their positions on the sky. Thanks to our extensive follow-up observations, this sample has now achieved a comparatively high degree of redshift completeness, and thus provides a legacy sample, useful for statistical studies of GRBs and their host galaxies. In this paper, we present the survey design and summarize the results of our observing program conducted at the ESO Very Large Telescope (VLT) aimed at obtaining the most basic properties of galaxies in this sample, including a catalog of R and Ks magnitudes and redshifts. We detect the host galaxies for 80% of the GRBs in the sample, although only 42% have Ks-band detections, which confirms that GRB-selected host galaxies are generally blue. The sample is not uniformly blue, however, with two extremely red objects detected. Moreover, galaxies hosting GRBs with no optical/NIR afterglows, whose identification therefore relies on X-ray localizations, are significantly brighter and redder than those with an optical/NIR afterglow. This supports a scenario where GRBs occurring in more massive and dusty galaxies frequently suffer high optical obscuration. Our spectroscopic campaign has resulted in 77% now having redshift measurements, with a median redshift of 2.14 ± 0.18. TOUGH alone includes 17 detected z> 2 Swift GRB host galaxies suitable for individual and statistical studies—a substantial increase over previous samples. Seven hosts have detections of the Lyα emission line and we can exclude an early indication that Lyα emission is ubiquitous among GRB hosts, but confirm that Lyα is stronger in GRB-selected galaxies than in flux-limited samples of Lyman break galaxies.

An HST optical-to-near-IR transmission spectrum of the hot Jupiter WASP-19b: detection of atmospheric water and likely absence of TiO

Abstract: We measure the transmission spectrum of WASP-19b from three transits using low-resolution optical spectroscopy from the Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS). The STIS spectra cover a wavelength range of 0.29-1.03 µm, with resolving power R = 500. The optical data are combined with archival near-infrared data from the HST Wide Field Camera 3 (WFC3) G141 grism, covering the wavelength range from 1.087 to 1.687 µm, with resolving power R = 130. We reach S/N levels between 3,000 and 11,000 in 0.1 µm bins when measuring the transmission spectra from 0.53-1.687 µm. WASP-19 is known to be a very active star, with the optical stellar flux varying by a few per cent over time. We correct the transit light curves for the effects of stellar activity using ground-based activity monitoring with the Cerro Tololo Inter-American Observatory (CTIO). While we were not able to construct a transmission spectrum using the blue optical data because of the presence of large occulted star spots, we were able to use the spot crossings to help constrain the mean stellar spot temperature. To search for predicted features in the hot-Jupiter atmosphere, in addition to the transmission spectrum we also define spectral indices for differential radius (�RP/R⋆) measurements to specifically search for the presence of TiO and alkali line features. Our measurements rule out TiO features predicted for a planet of WASP-19b’s equilibrium temperature (2050 K) in the transmission spectrum at the 2.7-2.9 σ confidence level, depending on atmospheric model formalism. The WFC3 transmission spectrum shows strong absorption features due to the presence of H2O, which is detected at the 4 σ confidence level between 1.1 and 1.4 µm. The transmission spectra results indicate that WASP-19b is a planet with no or low levels of TiO and without a high C/O ratio. The lack of observable TiO features are possibly due to rainout, breakdown from stellar activity or the presence of other absorbers in the optical.

The NGC 404 Nucleus: Star Cluster and Possible Intermediate Mass Black Hole

Abstract: We examine the nuclear morphology, kinematics, and stellar populations in nearby S0 galaxy NGC 404 using a combination of adaptive optics assisted near-IR integral-field spectroscopy, optical spectroscopy, and Hubble Space Telescope imaging. These observations enable study of the NGC 404 nucleus at a level of detail possible only in the nearest galaxies. The surface brightness profile suggests the presence of three components: a bulge, a nuclear star cluster (NSC), and a central light excess within the cluster at radii < 3 pc. These components have distinct kinematics with modest rotation seen in the NSC and counter-rotation seen in the central excess. Molecular hydrogen emission traces a disk with rotation nearly orthogonal to that of the stars. The stellar populations of the three components are also distinct, with half of the mass of the NSC having ages of ~1 Gyr (perhaps resulting from a galaxy merger), while the bulge is dominated by much older stars. Dynamical modeling of the stellar kinematics gives a total NSC mass of 1.1 × 107 M ☉. Dynamical detection of a possible intermediate-mass black hole (BH) is hindered by uncertainties in the central stellar mass profile. Assuming a constant mass-to-light ratio, the stellar dynamical modeling suggests a BH mass of <1 × 105 M ☉, while the molecular hydrogen gas kinematics are best fitted by a BH with a mass of 4.5+3.5 –2.0 × 105 M ☉. Unresolved and possibly variable dust emission in the near-infrared and active galactic nucleus-like molecular hydrogen emission-line ratios do suggest the presence of an accreting BH in this nearby LINER galaxy.

The Impact of Galaxy Interactions on Active Galactic Nucleus Activity in zCosmos

Abstract: Close encounters between galaxies are expected to be a viable mechanism, as predicted by numerical simulations, by which accretion onto supermassive black holes can be initiated. To test this scenario, we construct a sample of 562 galaxies (M_* > 2.5 × 10^(10) M_☉) in kinematic pairs over the redshift range 0.25 2 × 10^(42) erg s^(–1)) detected by Chandra. We find a higher fraction of an AGN in galaxies in pairs relative to isolated galaxies of similar stellar mass. Our result is primarily due to an enhancement of AGN activity, by a factor of 1.9 (observed) and 2.6 (intrinsic), for galaxies in pairs of projected separation less than 75 kpc and line-of-sight velocity offset less than 500 km s^(–1). This study demonstrates that close kinematic pairs are conducive environments for black hole growth, either indicating a causal physical connection or an inherent relation, such as, to enhanced star formation. In the Appendix, we describe a method for estimating the intrinsic fractions of galaxies (either in pairs or the field) hosting an AGN with confidence intervals, and an excess fraction in pairs. We estimate that 17.8^(+8.4)_(–7.4)% of all moderate-luminosity AGN activity takes place within galaxies undergoing early stages of interaction that leaves open the question as to what physical processes are responsible for fueling the remaining ~80% that may include late-stage mergers.

Planck early results. XX. New light on anomalous microwave emission from spinning dust grains

Abstract: Anomalous microwave emission (AME) has been observed by numerous experiments in the frequency range ~10–60 GHz. Using Planck maps and multi-frequency ancillary data, we have constructed spectra for two known AME regions: the Perseus and ρ Ophiuchi molecular clouds. The spectra are well fitted by a combination of free-free radiation, cosmic microwave background, thermal dust, and electric dipole radiation from small spinning dust grains. The spinning dust spectra are the most precisely measured to date, and show the high frequency side clearly for the first time. The spectra have a peak in the range 20–40 GHz and are detected at high significances of 17.1σ for Perseus and 8.4σ for ρ Ophiuchi. In Perseus, spinning dust in the dense molecular gas can account for most of the AME; the low density atomic gas appears to play a minor role. In ρ Ophiuchi, the ~30 GHz peak is dominated by dense molecular gas, but there is an indication of an extended tail at frequencies 50–100 GHz, which can be accounted for by irradiated low density atomic gas. The dust parameters are consistent with those derived from other measurements. We have also searched the Planck map at 28.5 GHz for candidate AME regions, by subtracting a simple model of the synchrotron, free-free, and thermal dust. We present spectra for two of the candidates; S140 and S235 are bright Hii regions that show evidence for AME, and are well fitted by spinning dust models.