J/A+A/654/A20 Parallax zero-point offset from Gaia EDR3 data (Groenewegen, 2021)
The parallax zero-point offset from Gaia EDR3 data.
Groenewegen M.A.T
<Astron. Astrophys. 654, A20 (2021)>
=2021A&A...654A..20G 2021A&A...654A..20G (SIMBAD/NED BibCode)
ADC_Keywords: Stars, distances ; Parallaxes, trigonometric
Keywords: stars: distances - parallaxes
Abstract:
The second data release of Gaia revealed a parallax zero-point offset
of -0.029mas based on quasars. The value depended on the position on
the sky, and also likely on magnitude and colour. The offset and its
dependence on other parameters inhibited improvement in the local
distance scale using for example the Cepheid and RR Lyrae
period-luminosity relations. Analysis of the recent Gaia Early Data
Release 3 (EDR3) reveals a mean parallax zero-point offset of -0.021
mas based on quasars.
The Gaia team addresses the parallax zero-point offset in detail and
proposes a recipe to correct for it based on ecliptic latitude, G-band
magnitude, and colour information.
This paper presents a completely independent investigation into this
issue focusing on the spatial dependence of the correction based on
quasars and the magnitude dependence based on wide binaries. The
spatial and magnitude corrections are connected to each other in the
overlap region in the range 17<G<19. The spatial correction is
presented at several spatial resolutions based on the HEALPix
formalism. The colour dependence of the parallax offset is unclear and
in any case secondary to the spatial and magnitude dependence.
The spatial and magnitude corrections are applied to two samples of
brighter sources, namely a sample of approximately 100 stars with
independent trigonometric parallax measurements from Hubble Space
Telescope data, and a sample of 75 classical cepheids using
photometric parallaxes. The mean offset between the observed GEDR3
parallax and the independent trigonometric parallax (excluding
outliers) is about -39µas, and after applying the correction it is
consistent with being zero. For the classical cepheid sample the
analysis presented here suggests that the photometric parallaxes may
be underestimated by about 5%.
Description:
The tabular material describes the basic parameters for the sample of
stars with an independent trigonometric parallax (Table 1) and the
parallax zero-point offset at G=20mag for different models (mnn.dat,
where nn= 30,31,..,39 and refers to the model number in Table 2 of the
paper, full Table 3).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 142 111 Stars with independent trigonometric parallaxes
m30.dat 30 12 Parallax zero-point offset for Model 30
m31.dat 30 48 Parallax zero-point offset for Model 31
m32.dat 30 192 Parallax zero-point offset for Model 32
m33.dat 30 768 Parallax zero-point offset for Model 33
m34.dat 30 3072 Parallax zero-point offset for Model 34
m35.dat 30 12 Parallax zero-point offset for Model 35
m36.dat 30 48 Parallax zero-point offset for Model 36
m37.dat 30 192 Parallax zero-point offset for Model 37
m38.dat 30 768 Parallax zero-point offset for Model 38
m39.dat 30 3072 Parallax zero-point offset for Model 39
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 24 A24 --- Name Identifier
26- 32 F7.3 mas plx Parallax
34- 39 F6.4 mas e_plx Parallax error
41 I1 --- r_plx Parallax reference (1)
45- 54 F10.6 deg RAdeg Right Ascension (ICRS) at Ep=2016.0
55 A1 --- f_RAdeg [)] ) for position not in (ICRS) at Ep=2016.0
57- 66 F10.6 deg DEdeg Declination (ICRS) at Ep=2016.0
67 A1 --- f_DEdeg [)] ) for position not in (ICRS) at Ep=2016.0
69- 87 I19 --- GaiaEDR3 ? GAIA EDR3 Source Id
90- 96 F7.3 mas plxG ?=- GAIA parallax
98-102 F5.3 mas e_plxG ? GAIA parallax error
104-110 F7.2 --- GoF ? GAIA Goodness-of-fit
112-116 F5.2 --- RUWE ?=- GAIA RUWE
118-123 F6.3 mag Gmag ? GAIA G-band magnitude
125-129 F5.3 mag e_Gmag ? GAIA G-band magnitude error
131-136 F6.3 mag BP-RP ? GAIA (GBP-GRP) colour
138-142 F5.3 mag e_BP-RP ? GAIA (GBP-GRP) colour
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Note (1): References as follows:
1 = Benedict et al., 2017PASP..129a2001B 2017PASP..129a2001B
2 = Bond et al., 2018ApJ...853...55B 2018ApJ...853...55B
3 = Gaia DR2, 2018A&A...616A...1G 2018A&A...616A...1G, Cat. I/345
4 = Riess et al., 2014ApJ...785..161R 2014ApJ...785..161R
5 = Riess et al., 2018ApJ...855..136R 2018ApJ...855..136R
6 = van Belle et al., 2020PASP..132e4201V 2020PASP..132e4201V
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Byte-by-byte Description of file: m??.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- pixel HEALPix pixel number
6- 14 E9.3 mas PZPO Parallax zeropoint offset (1)
16- 23 E8.3 mas e_PZPO Error in the PZPO
25- 30 I6 --- N Number of objects in that pixel
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Note (1): If the number of objects in a HEALPix pixel is 0 the PZPO and error
are undefined. In the table they are given the value 0.0.
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Acknowledgements:
Martin Groenewegen, martin.groenewegen(at)oma.be
(End) Patricia Vannier [CDS] 25-Jul-2021