Leonard Burtscher | TU Delft Repository

LLAMA: The M_BH-σ_⋆ relation of the most luminous local AGNs

Journal article (2020) - Turgay Caglar, Leonard Burtscher, Bernhard Brandl, Jarle Brinchmann, Richard I. Davies, Erin K. S. Hicks, Michael Koss, Ming-Yi Lin, Witold Maciejewski, More authors...

Context. The MBH-relation is considered a result of coevolution between the host galaxies and their supermassive black holes. For elliptical bulge hosting inactive galaxies, this relation is well established, but there is still discussion concerning whether active galaxies follow the same relation. Aims. In this paper, we estimate black hole masses for a sample of 19 local luminous active galactic nuclei (AGNs; LLAMA) to test their location on the MBH- relation. In addition, we test how robustly we can determine the stellar velocity dispersion in the presence of an AGN continuum and AGN emission lines, and as a function of signal-to-noise ratio. Methods. Supermassive black hole masses (MBH) were derived from the broad-line-based relations for Hff, H, and Pa emission line profiles for Type 1 AGNs. We compared the bulge stellar velocity dispersion () as determined from the Ca II triplet (CaT) with the dispersion measured from the near-infrared CO (2-0) absorption features for each AGN and find them to be consistent with each other. We applied an extinction correction to the observed broad-line fluxes and we corrected the stellar velocity dispersion by an average rotation contribution as determined from spatially resolved stellar kinematic maps. Results. The Hff-based black hole masses of our sample of AGNs were estimated in the range 6:34 > log MBH > 7:75 M and the CaT estimates range between 73 > CaT > 227 km s1. From the so-constructed MBH relation for our Type 1 AGNs, we estimate the black hole masses for the Type 2 AGNs and the inactive galaxies in our sample. Conclusions.We find that our sample of local luminous AGNs is consistent with the MBH- relation of lower luminosity AGNs and inactive galaxies, after correcting for dust extinction and the rotational contribution to the stellar velocity persion. ...

Towards a physical understanding of the thermal background in large ground-based telescopes

Conference paper (2020) - Leonard Burtscher, Ioannis Politopoulos, Sergio Fernández-Acosta, Tibor Agocs, Mario van den Ancker, Roy van Boekel, Bernhard Brandl, Hans-Ulrich Käufl, Eric Pantin, More authors...

Ground-based thermal-infrared observations have a unique scientific potential, but are also extremely challenging due to the need to accurately subtract the high thermal background. Since the established techniques of chopping and nodding need to be modified for observations with the future mid-infrared ELT imager and spectrograph (METIS), we investigate the sources of thermal background subtraction residuals. Our aim is to either remove or at least minimise the need for nodding in order to increase the observing efficiency for METIS. To this end we need to improve our knowledge about the origin of chop residuals and devise observing methods to remove them most efficiently, i.e. with the slowest possible nodding frequency. Thanks to dedicated observations with VLT/VISIR and GranTeCan/CanariCam, we have successfully traced the origin of three kinds of chopping residuals to (1) the entrance window, (2) the spiders and (3) other warm emitters in the pupil, in particular the VLT M3 mirror cell in its parking position. We conclude that, in order to keep chopping residuals stable over a long time (and therefore allow for slower nodding cycles), the pupil illumination needs to be kept constant, i.e. (imaging) observations should be performed in pupil-stabilised, rather than field-stabilised mode, with image de-rotation in the post-processing pipeline. This is now foreseen as the default observing concept for all METIS imaging modes. ...

Inverse Chop Addition: Thermal IR Background Subtraction without Nodding

Journal article (2019) - A. G. M. Pietrow, L. Burtscher, B. Brandl

Due to the large size and mass of the secondary mirror on next generation extremely large telescopes it will not be possible to provide classical chopping and nodding as is used during mid-IR observations today. As a solution to this we propose an alternative approach to thermal background reduction called `inverse chop addition`. Here we use the symmetries of the thermal background to replace nodding, which allows us to get nearly identical background reductions while only using a special chopping pattern. The performance of this method was tested during technical time observations on VLT/VISIR. With this method, a higher observational efficiency can be obtained than with `classical chopping and nodding`, while achieving equally good reduction results. These results suggest that `inverse-chop addition` could be a good alternative for classical chopping and nodding on both current and next generation ground-based facilities. ...

Status of the mid-IR ELT imager and spectrograph (METIS)

Conference paper (2018) - Bernhard R. Brandl, Olivier Absil, Tibor Agócs, Felix Bettonvil, Leonard Burtscher, Ewine Van Dishoeck, Dirk Lesman, More Authors...

The Mid-Infrared ELT Imager and Spectrograph (METIS) is one of three first light instruments on the ELT. It will provide high-contrast imaging and medium resolution, slit-spectroscopy from 3 - 19um, as well as high resolution (R ∼ 100,000) integral field spectroscopy from 2.9-5.3μm. All modes observe at the diffraction limit of the ELT, by means of adaptive optics, yielding angular resolutions of a few tens of milliarcseconds. The range of METIS science is broad, from Solar System objects to active galactic nuclei (AGN). We will present an update on the main science drivers for METIS: circum-stellar disks and exoplanets. The METIS project is now in full steam, approaching its preliminary design review (PDR) in 2018. In this paper we will present the current status of its optical, mechanical and thermal design as well as operational aspects. We will also discuss the challenges of building an instrument for the ELT, and the required technologies. ...

The calibration unit of the mid-infrared E-ELT instrument METIS

Conference paper (2018) - Nicola Baccichet, Lucas Labadie, Adrian Glauser, Bernhard Brandl, Felix Bettonvil, Jeff Lynn, Andreas Eckart, Steffen Rost, Christian Straubmeier, Michael Wiest, Leonard Burtscher, Tibor Agócs, Willem Jellema, Ronald Roelfsema, Roy van Boekel

We present the preliminary design of the calibration unit of the future E-ELT instrument METIS. This independent subunit is mounted externally to the main cryostat of METIS and will function both as calibration reference for science observations, as well as verification and alignment tool during the AIT phase. In this paper, we focus on describing its preliminary layout and foreseen functionalities, based on the performance requirements defined at system level and the constraints imposed by warm IR background. We discuss the advantage of employing an integrating sphere as common radiation emitter, leading to a novel and versatile design, where the source's spatio-spectral properties can be varied with high fidelity and repeatability. By combining only few tuneable sources and mechanisms we show how a large instrument such as METIS can be calibrated and tested, without the need of a complex cold calibration unit. ...