SCALA: In situ calibration for integral field spectrographs

¹ Institut für Physik, Humboldt-Universität zu Berlin, Newtonstraße 15, 12489 Berlin, Germany
e-mail: lombardo@physik.hu-berlin.de
² Physics Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA
³ Laboratoire de Physique Nucléaire et des Hautes Énergies, Université Pierre et Marie Curie Paris 6, Université Paris Diderot Paris 7, CNRS-IN2P3, 4 place Jussieu, 75252 Paris Cedex 05, France
⁴ Department of Physics, Yale University, New Haven, CT 06250-8121, USA
⁵ Université de Lyon; Université de Lyon 1, Villeurbanne; CNRS/IN2P3, Institut de Physique Nucléaire de Lyon, 69622 Lyon, France
⁶ Department of Physics, University of California Berkeley, 366 LeConte Hall MC 7300, Berkeley, CA 94720-7300, USA
⁷ Deutsches Elektronen-Synchrotron, 15735 Zeuthen, Germany
⁸ Clermont Université, Université Blaise Pascal, CNRS/IN2P3, Laboratoire de Physique Corpusculaire, BP 10448, 63000 Clermont-Ferrand, France
⁹ Computational Cosmology Center, Computational Research Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 50B-4206, Berkeley, CA 94720, USA
¹⁰ Centre de Recherche Astronomique de Lyon, Université Lyon 1, 9 avenue Charles André, 69561 Saint-Genis-Laval Cedex, France
¹¹ Aix-Marseille Université, CNRS/IN2P3, CPPM UMR 7346, 13288 Marseille, France
¹² Tsinghua Center for Astrophysics, Tsinghua University, 100084 Beijing, PR China
¹³ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching bei München, Germany
¹⁴ Physikalisches Institut, Nussallee 12, Universität Bonn, 53113 Bonn, Germany
¹⁵ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
¹⁶ The Oskar Klein Centre, Department of Physics, AlbaNova, Stockholm University, 106 91 Stockholm, Sweden
¹⁷ Institute for Astronomy, 640 North A’oho̅ku̅ Place, #209 Hilo, HI 96720-2700, USA
¹⁸ Bonn-Shutter UG, Auf dem Hügel 71, Universität Bonn, 53113 Bonn, Germany
¹⁹ Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, 277-8583 Chiba, Japan
²⁰ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany

Received: 1 May 2017
Accepted: 8 August 2017

Abstract

Aims. The scientific yield of current and future optical surveys is increasingly limited by systematic uncertainties in the flux calibration. This is the case for type Ia supernova (SN Ia) cosmology programs, where an improved calibration directly translates into improved cosmological constraints. Current methodology rests on models of stars. Here we aim to obtain flux calibration that is traceable to state-of-the-art detector-based calibration.

Methods. We present the SNIFS Calibration Apparatus (SCALA), a color (relative) flux calibration system developed for the SuperNova integral field spectrograph (SNIFS), operating at the University of Hawaii 2.2 m (UH 88) telescope.

Results. By comparing the color trend of the illumination generated by SCALA during two commissioning runs, and to previous laboratory measurements, we show that we can determine the light emitted by SCALA with a long-term repeatability better than 1%. We describe the calibration procedure necessary to control for system aging. We present measurements of the SNIFS throughput as estimated by SCALA observations.

Conclusions. The SCALA calibration unit is now fully deployed at the UH 88 telescope, and with it color-calibration between 4000 Å and 9000 Å is stable at the percent level over a one-year baseline.