Hintze Centre for Astrophysical Surveys

Abstract:

Within the VLT instrumentation program, the second generation instrument ERIS (Enhanced Resolution Imager and Spectrograph) combines two key scientifically successful elements of the VLT first generation instrumentation program: It consists of a full renovation of the integral field spectrograph SPIFFI and a new near-IR camera NIX, implementing the most scientifically important imaging modes offered so far by NACO (imaging in the J to M bands, astrometry, Sparse Aperture Masking and Apodizing Phase Plate (APP) coronagraphy). Both diffraction limited sub-systems of ERIS make use of the latest AO technologies with the newly installed AOF (AO Facility) Deformable Secondary Mirror with 1170 actuators and a new laser guide star system. We will describe the changes that will be implemented, give a summary of what SINFONI is currently achieving, and present what to expect from the performance upgrade. With instruments becoming more complex and therefore increasing development times, we describe the challenges to improve image quality, spectral and spatial resolution on the same focus of a VLT UT, which could become valuable lessons for the extension of the life of actual instruments and of future ones. We will address the impact of the aging of the instrument and what critical parts to consider in the design in view of future upgrades, to possibly extend the performances, capabilities and lifetime at lower development costs.

Abstract:

The connection between accretion and jet production in accreting white dwarf binary systems, especially dwarf novae, is not well understood. Radio wavelengths provide key insights into the mechanisms responsible for accelerating electrons, including jets and outflows. Here we present densely-sampled radio coverage, obtained with the Arcminute MicroKelvin Imager Large Array, of the dwarf nova SS Cyg during its February 2016 anomalous outburst. The outburst displayed a slower rise (3 days mag^-1) in the optical than typical ones, and lasted for more than 3 weeks. Rapid radio flaring on timescales <1 hour was seen throughout the outburst. The most intriguing behavior in the radio was towards the end of the outburst where a fast, luminous (“giant”), flare peaking at ~20 mJy and lasting for 15 minutes was observed. This is the first time that such a flare has been observed in SS Cyg, and insufficient coverage could explain its non-detection in previous outbursts. These data, together with past radio observations, are consistent with synchrotron emission from plasma ejection events as being the origin of the radio flares. However, the production of the giant flare during the declining accretion rate phase remains unexplained within the standard accretion-jet framework and appears to be markedly different to similar patterns of behavior in X-ray binaries.

Abstract:

We study trends in the slope of the total mass profiles and dark matter fractions within the central half-light radius of 258 early-type galaxies, using data from the volume-limited ATLAS3D survey. We use three distinct sets of dynamical models, which vary in their assumptions and also allow for spatial variations in the stellar mass-to-light ratio, to test the robustness of our results. We confirm that the slopes of the total mass profiles are approximately isothermal, and investigate how the total mass slope depends on various galactic properties. The most statistically significant correlations we find are a function of either surface density, Σe, or velocity dispersion, σe. However there is evidence for a break in the latter relation, with a nearly universal logarithmic slope above log10[σe/(km s−1)] ∼ 2.1 and a steeper trend below this value. For the 142 galaxies above that critical σe value, the total mass–density logarithmic slopes have a mean value 〈γ΄〉 = −2.193 ± 0.016 (1σ error) with an observed rms scatter of only σγ′=0.168±0.015. Considering the observational errors, we estimate an intrinsic scatter of σγ′intr≈0.15. These values are broadly consistent with those found by strong lensing studies at similar radii and agree, within the tight errors, with values recently found at much larger radii via stellar dynamics or H I rotation curves (using significantly smaller samples than this work).

Abstract:

The LOFAR Two-metre Sky Survey (LoTSS) is a deep 120–168 MHz imaging survey that will eventually cover the entire northern sky. Each of the 3170 pointings will be observed for 8 h, which, at most declinations, is sufficient to produce ~5″ resolution images with a sensitivity of ~100 μJy/beam and accomplish the main scientific aims of the survey, which are to explore the formation and evolution of massive black holes, galaxies, clusters of galaxies and large-scale structure. Owing to the compact core and long baselines of LOFAR, the images provide excellent sensitivity to both highly extended and compact emission. For legacy value, the data are archived at high spectral and time resolution to facilitate subarcsecond imaging and spectral line studies. In this paper we provide an overview of the LoTSS. We outline the survey strategy, the observational status, the current calibration techniques, a preliminary data release, and the anticipated scientific impact. The preliminary images that we have released were created using a fully automated but direction-independent calibration strategy and are significantly more sensitive than those produced by any existing large-area low-frequency survey. In excess of 44 000 sources are detected in the images that have a resolution of 25″, typical noise levels of less than 0.5 mJy/beam, and cover an area of over 350 square degrees in the region of the HETDEX Spring Field (right ascension 10h45m00s to 15h30m00s and declination 45°00′00″ to 57°00′00″).