An absolute calibration of DENIS (deep near infrared southern sky survey)
Astron. Astrophys. Suppl. Ser.
An absolute calibration of DENIS (deep near infrared southern sky survey)
P. Fouque 11 12
L. Chevallier 11
M. Cohen 9
E. Galliano 11
C. Loup 17
C. Alard 3
B. de Batz 16
E. Bertin 17
J. Borsenberger 17
M.R. Cioni 15
E. Copet 12
M. Dennefeld 17
S. Derriere 14
E. Deul 15
P.-A. Duc 19
D. Egret 14
N. Epchtein 18
T. Forveille 13
F. Garzon 4
H.J. Habing 15
J. Hron 7
S. Kimeswenger 8
F. Lacombe 12
T. Le Bertre 5
G.A. Mamon 6 17
A. Omont 17
G. Paturel 1
S. Pau 12
P. Persi 2
A.C. Robin 0
D. Rouan 12
M. Schultheis 17
G. Simon 3
D. Tiphene 12
I. Vauglin 1
S.J. Wagner 10
0 Observatoire de Besancon , BP. 1615, F-25010 Besancon Cedex , France
1 CRAL , Observatoire de Lyon, F-69561 Saint-Genis Laval Cedex , France
2 Istituto di Astro sica Spaziale, CNR , C.P. 67, I-00044 Frascati , Italy
3 DASGAL, Observatoire de Paris , 61 Av. de l'Observatoire, F-75014 Paris , France
4 Instituto de Astrof sica de Canarias, E-38200 La Laguna , Tenerife , Spain
5 DEMIRM, Observatoire de Paris , 61 Av. de l'Observatoire, F-75014 Paris , France
6 DAEC, Observatoire de Paris , 5 place J. Janssen, F-92195 Meudon Cedex , France
7 Institut fu ̈r Astronomie der Universit ̈at Wien , Tu ̈rkenschanzstrasse 17, A-1180 Wien , Austria
8 Institut fu ̈r Astronomie, Innsbruck University , A-6020 Innsbruck , Austria
9 Radio Astronomy Laboratory , 601 Campbell Hall , University of California , Berkeley, CA 94720 , U.S.A
10 Landessternwarte Heidelberg, K ̈onigstuhl , D-69117 Heidelberg , Germany
11 European Southern Observatory , Casilla 19001, Santiago 19 , Chile
12 DESPA, Observatoire de Paris , 5 place J. Janssen, F-92195 Meudon Cedex , France
13 Observatoire de Grenoble , 414 rue de la Piscine, Domaine Universitaire de Saint Martin d'Heres, F-38041 Grenoble , France
14 CDS , Observatoire Astronomique de Strasbourg, UMR 7550, 11 rue de l'Universite, F-67000 Strasbourg , France
15 Leiden Observatory, University of Leiden , P.O. Box 9513, 2300 RA Leiden , The Netherlands
16 DASGAL, Observatoire de Paris , 5 place J. Janssen, F-92195 Meudon Cedex , France
17 Institut d'Astrophysique de Paris , 98 bis Bd. Arago, F-75014 Paris , France
18 Observatoire de la C
19 CEA, DSM, DAPNIA, Centre d'Etudes de Saclay , F-91191 Gif-sur-Yvette Cedex , France
20 ote d'Azur, Departement Fresnel , F-06304 Nice Cedex , France
An absolute calibration of the DENIS photometric system is presented. It includes the determination of the overall transmission pro les in the 3 bands, namely i, J and Ks, combining contributions from atmosphere, telescope mirrors, instrument lenses and dichroics, lters, and detectors. From these normalized pro les, isophotal and e ective wavelengths are computed, using the same synthetic Vega spectrum as that used to support the absolute calibration of many other ground-based and spaceborne photometric systems. Flux densities at zero magnitude are derived and integrated to give in-band fluxes, which are used to compute theoretical zero-points and compare them to observed ones, yielding estimates of the overall throughput of the whole system.
surveys | instrumentation; miscellaneous
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1. Introduction
The main goal of the DENIS survey (Deep Near-Infrared
Southern Sky Survey, see
Epchtein et al. (1994)
for a
complete introduction to DENIS) is to bridge the gap between
the optical surveys on Schmidt plates and the far-infrared
IRAS survey. Many aspects of astrophysics will bene t
from such a survey, particularly studies of cool stars and
heavily obscured regions.
Each night, roughly 1 million stars are detected by
at least one of the 3 cameras of the DENIS instrument.
Photometric calibration is derived by observation of stan
dard star elds. In order to compare our magnitude system
to published ones, we need a precise de nition of our
photometric bands and an absolute calibration of the DENIS
photometric system.
In Sect. 2, we describe the DENIS instrument and
show the response curve for the complete system in the
three bands. In Sect. 3, we estimate the conversion factors
(ADUs to electrons) from the typical characteristics of
DENIS images. Absolute calibration, based upon a
synthetic Vega spectrum, is performed in Sect. 4, and
observed and theoretical zero-points are compared.
2. Instrument characteristics
The DENIS instrument has been described in detail by
Copet et al. (1999)
. A sketch of its main optical
components is displayed in Fig. 1. It is located at the Cassegrain
focus of the ESO 1 m telescope at La Silla Observatory
(Chile). After reflection from the two telescope mirrors,
the light beam goes through a eld lens at the telescope
focus, covered by a protective blade, both of CaF2 and
uncoated. Then a dichroic splits the i beam in reflection
from the J /Ks beam in transmission.
The i beam has two more reflections from coated
mirrors before entering the objective (3 CaF2 and 2 silica
coated lenses), then goes through the Gunn i lter, a
shutter, the cryost (...truncated)