J/A+A/649/A3 Gaia Early Data Release 3 photometric passbands (Riello+, 2021)
Gaia Early Data Release 3: Photometric content and validation.
Riello M., De Angeli F., Evans D.W., Montegriffo P., Carrasco J.M,
Busso G., Palaversa L., Burgess P., Diener C., Davidson M., Rowell N.,
Fabricius C., Jordi C., Bellazzini M., Pancino E., Harrison D.L.,
Cacciari C., van Leeuwen F., Hambly N.C., Hodgkin S.T., Osborne P.J.,
Altavilla G., Barstow M.A., Brown A.G.A., Castellani M., Cowell S.,
De Luise F., Gilmore G., Giuffrida G., Hidalgo S., Holland G., Marinoni S.,
Pagani C., Piersimoni A.M., Pulone L., Ragaini S., Rainer M., Richards P.J.,
Sanna N., Walton N.A., Weiler M., Yoldas A.
<Astron. Astrophys. 649, A3 (2021)>
=2021A&A...649A...3R 2021A&A...649A...3R (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Photometry, G band
Keywords: catalogues - surveys - instrumentation: photometers -
techniques: photometric - Galaxy: general
Abstract:
Gaia Early Data Release 3 (Gaia EDR3) contains astrometry and
photometry results for about 1.8 billion sources based on
observations collected by the European Space Agency Gaia satellite
during the first 34 months of its operational phase.
In this paper, we focus on the photometric content, describing the
input data, the algorithms, the processing, and the validation of the
results. Particular attention is given to the quality of the data and
to a number of features that users may need to take into account to
make the best use of the Gaia EDR3 catalogue.
The processing broadly followed the same procedure as for Gaia DR2,
but with significant improvements in several aspects of the blue and
red photometer (BP and RP) preprocessing and in the photometric
calibration process. In particular, the treatment of the BP and RP
background has been updated to include a better estimation of the
local background, and the detection of crowding effects has been used
to exclude affected data from the calibrations. The photometric
calibration models have also been updated to account for flux loss
over the whole magnitude range. Significant improvements in the
modelling and calibration of the Gaia point and line spread functions
have also helped to reduce a number of instrumental effects that were
still present in DR2.
Gaia EDR3 contains 1.806 billion sources with G-band photometry and
1.540 billion sources with GBP and GRP photometry. The median
uncertainty in the G-band photometry, as measured from the standard
deviation of the internally calibrated mean photometry for a given
source, is 0.2mmag at magnitude G=10 to 14, 0.8mmag at G∼17, and
2.6mmag at G∼19. The significant magnitude term found in the Gaia DR2
photometry is no longer visible, and overall there are no trends
larger than 1mmag/mag. Using one passband over the whole colour and
magnitude range leaves no systematics above the 1% level in magnitude
in any of the bands, and a larger systematic is present for a very
small sample of bright and blue sources. A detailed description of the
residual systematic effects is provided. Overall the quality of the
calibrated mean photometry in Gaia EDR3 is superior with respect to
DR2 for all bands.
Description:
These tabular data describes the photometric system defined by the G,
GBP and GRP Gaia bands for Gaia Early Data Release 3.
The tables provide the full passband and the corresponding zero point
for each of the photometric bands. The zero points are available both
in the VEGAMAG and AB systems.
The passband calibration is based on the modelling of a set of
corrections applied to pre-launch knowledge of the instrument, to find
the best match between observed and synthetic photometry for a set of
calibrators. For EDR3 a large set of calibrators covering a wide range
of spectra types was used for the passband calibration.
For these sources reconstructed SEDs were obtained from externally
calibrated Gaia BP/RP spectra.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
passband.dat 103 781 G, GBP anf GRP passbands used to generate
the magnitudes and astrophysical parameters
included in Gaia EDR3
zeropt.dat 97 2 G, GBP and GRP zero points used to generate
the magnitudes and astrophysical parameters
included in Gaia EDR3
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See also:
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
J/A+A/649/A6 : Gaia Catalogue of Nearby Stars - GCNS (Gaia collaboration, 2021)
J/A+A/649/A7 : MC structure and properties (Gaia Collaboration+, 2021)
Byte-by-byte Description of file: passband.dat
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Bytes Format Units Label Explanations
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1- 7 F7.2 nm lambda Wavelength
10- 23 E14.9 mag GPb ?=99.99 G transmissivity curve at the
corresponding wavelength (1)
26- 39 E14.9 mag e_GPb ?=99.99 Uncertainty on the G transmissivity
curve (1)
42- 55 E14.9 mag BPPb ?=99.99 BP transmissivity curve at the
corresponding wavelength (1)
58- 71 E14.9 mag e_BPPb ?=99.99 Uncertainty on the BP transmissivity
curve (1)
74- 87 E14.9 mag RPPb ?=99.99 RP transmissivity curve at the
corresponding wavelength (1)
90-103 E14.9 mag e_RPPb ?=99.99 Uncertainty on the RP transmissivity
curve (1)
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Note (1): In correspondence to wavelength values where the passband is not
defined, both transmissivity and uncertainty are set to 99.99.
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Byte-by-byte Description of file: zeropt.dat
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Bytes Format Units Label Explanations
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2- 14 F13.10 --- GZp G band zero point
18- 29 F12.10 --- e_GZp G band zero point uncertainty
32- 44 F13.10 --- BPZp GBP band zero point
48- 59 F12.10 --- e_BPZp GBP band zero point uncertainty
62- 74 F13.10 --- RPZp GRP band zero point
78- 89 F12.10 --- e_RPZp GRP band zero point uncertainty
91- 97 A7 --- System [VEGAMAG, AB] Photometric system
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Acknowledgements:
Marco Riello, mriello(at)ast.cam.ac.uk
Francesca De Angeli, fda(at)ast.cam.ac.uk
(End) Francesca De Angeli [IoA, UK], Patricia Vannier [CDS] 05-Jan-2021