69 research outputs found
The distance to NGC1316 (Fornax A): yet another curious case
The distance of NGC1316, the brightest galaxy in Fornax, is an interesting
test for the cosmological distance scale. First, because Fornax is the 2nd
largest cluster of galaxies at <~25 Mpc after Virgo and, in contrast to Virgo,
has a small line-of-sight depth; and second, because NGC1316 is the galaxy with
the largest number of detected SNeIa, giving the opportunity to test the
consistency of SNeIa distances internally and against other indicators.
We measure SBF mags in NGC1316 from ground and space-based imaging data,
providing a homogeneous set of measurements over a wide wavelength interval.
The SBF, coupled with empirical and theoretical calibrations, are used to
estimate the distance to the galaxy. We present the first B-band SBF
measurements of NGC1316 and use them together with the optical and near-IR SBF
data to analyze the properties of field stars.
Our distance modulus m-M=31.59 +-0.05(stat) +-0.14(sys), when placed in a
consistent Cepheid distance scale, agrees with the results from other
indicators. However, our result is ~17% larger than the most recent estimate
based on SNeIa. Possible explanations for this disagreement are the
uncertainties on internal extinction, or calibration issues. Concerning the
stellar population analysis, we confirm earlier results from other indicators:
the field stars in NGC1316 are dominated by a solar metallicity, intermediate
age component. A substantial mismatch exists between B-band SBF models and
data, a behavior that can be accounted for by an enhanced percentage of hot
horizontal branch stars.
Our study of the SBF distance to NGC1316, and the comparison with distances
from other indicators, raises some concern about the homogeneity between the
calibrations of different indicators. If not properly placed in the same
reference scale, significant differences can occur, with dramatic impact on the
cosmological distance ladder.Comment: 21 pages, 13 figures; A&A accepte
Autonomous Observations in Antarctica with AMICA
The Antarctic Multiband Infrared Camera (AMICA) is a double channel camera
operating in the 2-28 micron infrared domain (KLMNQ bands) that will allow to
characterize and exploit the exceptional advantages for Astronomy, expected
from Dome C in Antarctica. The development of the camera control system is at
its final stage. After the investigation of appropriate solutions against the
critical environment, a reliable instrumentation has been developed. It is
currently being integrated and tested to ensure the correct execution of
automatic operations. Once it will be mounted on the International Robotic
Antarctic Infrared Telescope (IRAIT), AMICA and its equipment will contribute
to the accomplishment of a fully autonomous observatory.Comment: 12 pages, 4 figures, Advances in Astronomy Journal, Special Issue
"Robotic Astronomy", Accepted 11 February 201
Final design and construction of the ERIS calibration unit
The Calibration Unit (CU) is a subsystem of the Enhanced Resolution Imager and Spectrograph (ERIS), the newgeneration instrument for the Cassegrain focus of the ESO UT4/VLT, aimed at performing AO-assisted imaging and medium resolution spectroscopy in the 1-5 micron wavelength range. The ERIS-CU is aimed to providing both focal plane artificial sources and uniform illumination over the 0.4 - 2.4 micron wavelengh range, for purposes of calibration and technical check of the SPIFFIER spectrograph, the NIX camera and the AO Module. Some challenging aspects emerged during the detailed design phase, mainly related to the need to cover such a broad wavelength range while ensuring adequate photon rates, excellent image quality and high Strehl. The technical solutions adopted to achieve the final design goals are presented and their implementation during the construction phase are shown and discussed
Design of the ERIS calibration unit
The Enhanced Resolution Imager and Spectrograph (ERIS) is a new-generation instrument for the Cassegrain focus of the ESO UT4/VLT, aimed at performing AO-assisted imaging and medium resolution spectroscopy in the 1-5 micron wavelength range. ERIS consists of the 1-5 micron imaging camera NIX, the 1-2.5 micron integral field spectrograph SPIFFIER (a modified version of SPIFFI, currently operating on SINFONI), the AO module and the internal Calibration Unit (ERIS CU). The purpose of this unit is to provide facilities to calibrate the scientific instruments in the 1-2.5 micron and to perform troubleshooting and periodic maintenance tests of the AO module (e.g. NGS and LGS WFS internal calibrations and functionalities, ERIS differential flexures) in the 0.5 - 1 μm range. The ERIS CU must therefore be designed in order to provide, over the full 0.5 - 2.5 μm range, the following capabilities: 1) illumination of both the telescope focal plane and the telescope pupil with a high-degree of uniformity; 2) artificial point-like and extended sources onto the telescope focal plane, with high accuracy in both positioning and FWHM; 3) wavelength calibration; 4) high stability of these characteristics. In this paper the design of the ERIS CU, and the solutions adopted to fulfill all these requirements, is described. The ERIS CU construction is foreseen to start at the end of 2016
ELT-HIRES the High Resolution Spectrograph for the ELT: the IFU-SCAO module
We present the results from the phase A study of ELT-HIRES, an optical-infrared High Resolution Spectrograph for ELT, which has just been completed by a consortium of 30 institutes from 12 countries forming a team of about 200 scientists and engineers. The top science cases of ELT-HIRES will be the detection of life signatures from exoplanet atmospheres, tests on the stability of Nature's fundamental couplings, the direct detection of the cosmic acceleration. However, the science requirements of these science cases enable many other groundbreaking science cases. The baseline design, which allows to fulfil the top science cases, consists in a modular fiber- fed cross-dispersed echelle spectrograph with two ultra-stable spectral arms providing a simultaneous spectral range of 0.4-1.8 μm at a spectral resolution of 100,000. The fiber-feeding allows ELT-HIRES to have several, interchangeable observing modes including a SCAO module and a small diffraction-limited IFU
Design and status of the NGS WFS of MAORY
MAORY is the first-light multi-conjugate AO facility of the E-ELT, providing a >30% Strehl ratio (evaluated inK band, median seeing conditions) over the MICADO 53 ×53 arcsec FoV and ensuring an overall sky coverageof 50%. MAORY will implement 3 NGS WFS having a double functionality: sensing the atmospheric low-ordermodes (LO-WFS) and de-trending the LGS WFS measurements (Ref-WFS).To maximize the AO sky-coverage the preliminary design of the LO-WFS foresees a 2×2 subapertures Shack-Hartmann sensor working in the H band, where the partial AO-correction regime and the low-noise detectorsbased on APD technology will enhance the WFS sensitivity. The Reference WFS will measure at slow rate(1÷10 s) the first ∼100 modes of the atmospheric aberration and it will correct the LGS measurements that areaffected by the Sodium layer drifts. The Ref-WFS will be a 10×10 SH making use of a CCD220-based detector.Hence it will work at visibile wavelenghts, using the same NGS of the LO-WFS.We present here the results of a study aimed to find the best design solutions for the MAORY NGS WFSin preparation of the project preliminary design review of scheduled in February 2018. We describe first theoutput of numerical simulations to find the best compromise between the working bandwidth and sampling of theLO-WFS and the sky-coverage corresponding to the expected performance. Then we describe the arrangementfor the NGS WFS module, hosted on top of the MICADO cryostat, analyzing the static and dynamic propertiesof the NGS module structure. Finally we present the opto-mechanical layout for the NGS WFS and its degreesof freedom
Control electronics of the ERIS AO and CU subsystems
The Adaptive Optics module and the Calibration Unit of the Enhanced Resolution Imager and Spectrograph (ERIS) share a similar Instrument Control Electronics (ICE). The architecture was designed according to the ESO standards and specifications. The large number of functions of these two complex subsystems are ensured by the automation software running on a Beckhoff PLC based control system. This paper describes the AO and CU design, their Instrument Control Electronics, main functions of the two subsystems and the activities performed during the first period of the MAIV phase
Status of the preliminary design of the NGS WFS subsystem of MAORY
The Natural Guide Star (NGS) Wavefront Sensor (WFS) sub-system of MAORY implements 3 Low-Order and Reference (LOR) WFS needed by the Multi-Conjugate Adaptive Optics (MCAO) system. Each LOR WFS has 2 main purposes: first, to sense the fast low-order modes that are affected by atmospheric anisoplanatism and second, to de-trend the LGS measurements from the slow spatial and temporal drifts of the Sodium layer. These features require to implement 2 different WFS sharing the same NGS and optical breadboard but being respectively a 2×2 Shack-Hartman Sensor (SHS) working at infrared wavelengths and a slow 10×10 SHS at visible bands. The NG WFS sub-system also provides a common support plate for the 3 WFS and their control electronics and cabling. The paper summarizes the status of the preliminary design of the LOR Module on the road to the MAORY Preliminary Design Review (PDR), focusing mainly on the description and analysis of the opto-mechanical arrangement foreseen for the NGS WFS sub-system. Performances and the design trade-offs of the NGS WFS sub-system are analyzed in a complementary paper. First, the requirement imposed by MAORY AO system are discussed. Then the paper gives an overview of the opto-mechanical arrangement for the main components of the sub-system: the support plate, the 3 WFS units and their interfaces to the instrument rotator. In the end the paper discusses the sub-system pointing and WFE budgets derived from different analyses. The design concept for the electronic devices of the sub-system, the cabinet arrangement and the cabling sheme are given in second complementary paper
ERIS: revitalising an adaptive optics instrument for the VLT
ERIS is an instrument that will both extend and enhance the fundamental
diffraction limited imaging and spectroscopy capability for the VLT. It will
replace two instruments that are now being maintained beyond their operational
lifetimes, combine their functionality on a single focus, provide a new
wavefront sensing module that makes use of the facility Adaptive Optics System,
and considerably improve their performance. The instrument will be competitive
with respect to JWST in several regimes, and has outstanding potential for
studies of the Galactic Center, exoplanets, and high redshift galaxies. ERIS
had its final design review in 2017, and is expected to be on sky in 2020. This
contribution describes the instrument concept, outlines its expected
performance, and highlights where it will most excel.Comment: 12 pages, Proc SPIE 10702 "Ground-Based and Airborne Instrumentation
for Astronomy VII
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