J/A+A/654/A107 Catalogues of Blue Horizontal Branch Stars (Culpan+, 2021)
Clean catalogues of blue horizontal branch stars using Gaia EDR3.
Culpan R., Pelisoli I., Geier S.
<Astron. Astrophys. 654, A107 (2021)>
=2021A&A...654A.107C 2021A&A...654A.107C (SIMBAD/NED BibCode)
ADC_Keywords: Stars, horizontal branch ; Stars, halo ; Blue objects ;
Proper motions ; Parallaxes, trigonometric
Keywords: Hertzsprung-Russell and C-M diagrams - stars: horizontal-branch -
catalogs - Galaxy: stellar content
Abstract:
Blue horizontal-branch stars evolve from low-mass stars that have
completed their main-sequence lifetimes and undergone a helium flash
at the end of their red-giant phase. As such, blue horizontal-branch
stars are very old objects that can be used as markers in studies of
the Galactic structure and formation history. To create a clean sky
catalogue of blue horizontal-branch stars, we cross-matched the Gaia
data release 2 (DR2) dataset with existing reference catalogues to
define selection criteria based on Gaia DR2parameters. Following the
publication of Gaia early data release 3 (EDR3), these methods were
verified and subsequently applied to this latest release.
Previous catalogues of blue horizontal-branch stars were developed
using spectral analyses or were restricted to individual globular
clusters. The purpose of this catalogue is to identify a set of blue
horizontal-branch star candidates that have been selected using
photometric and astrometric observations and exhibits a low
contamination rate. This has been deemed important as the success of
the Gaia mission has changed the way that targets are selected for
large-scale spectroscopic surveys, meaning that far fewer spectra will
be acquired for blue horizontal-branch stars in the future unless they
are specifically targeted.
We cross-matched reference blue horizontal-branch datasets with the
Gaia DR2 database and defined two sets of selection criteria. Firstly,
in Gaia DR2 - colour and absolute G magnitude space, and secondly, in
Gaia DR2 - colour and reduced proper motion space. The main-sequence
contamination in both subsets of the catalogue was reduced, at the
expense of completeness, by concentrating on the Milky Way's
Galactic halo, where relatively young main-sequence stars were not
expected. The entire catalogue is limited to those stars with no
apparent neighbours within 5 arcsec. These methods were verified and
subsequently applied to theGaia Early Data Release 3 (EDR3).
We present a catalogue, based on Gaia EDR3, of 57377 blue
horizontal-branch stars. The Gaia EDR3 parallax was used in selecting
16794 candidates and the proper motions were used to identify a
further 40583 candidates.
Description:
We present a catalogue, based on Gaia EDR3, of 57377 blue
horizontal-branch stars. The Gaia EDR3 parallax was used in selecting
16794 candidates and the proper motions were used to identify a
further 40583 candidates.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
plx.dat 322 16794 Catalogue or BHB from parallax
rpm.dat 322 40583 Catalogue of BHB from reduced PM
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See also:
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
Byte-by-byte Description of file: plx.dat rpm.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- GaiaEDR3 Unique source identifier (unique within a
particular Data Release) (source_id)
21- 42 F22.18 deg RAdeg FK5 J2000.0 Right Ascension (RA2000)
44- 66 F23.19 deg DEdeg FK5 J2000.0 Declination (DEC2000)
68- 90 E23.19 mas plx Parallax (parallax)
92-103 F12.10 mas e_plx Standard error of parallax (parallax_error)
105-114 F10.7 mag Gmag G-band mean magnitude (photgmean_mag)
116-137 E22.19 mag BP-RP BP-RP colour (bp_rp)
139-160 F22.19 mag GMAG ?=- Absolute G Magnitude (absgmag)
162-179 F18.14 km/s Vtan ?=- Tangential Velocity (tangential_velocity)
181-204 F24.19 mas/yr pmRA Proper motion in right ascension direction
(pmra)
206-217 F12.10 mas/yr e_pmRA Standard error of proper motion in
right ascension direction (pmra_error)
219-242 F24.19 mas/yr pmDE Proper motion in declination direction
(pmdec)
244-255 F12.10 mas/yr e_pmDE Standard error of proper motion in
declination direction (pmdec_error)
257-276 F20.16 mas/yr PM Total Proper Motion (totalpropermotion)
278-298 F21.16 mas/yr PM/e_PM Total Proper Motion over error
(totalpropermotionovererror)
300-318 F19.16 --- rpm Reduced Proper Motion (reducedpropermotion)
320 I1 --- Flagpm [0/1] Parallax candidate flag (absmagflag)
322 I1 --- Flagrpm [0/1] Proper motion candidate flag
(reducedpmflag)
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Acknowledgements:
Richard Culpan, rick(at)culpan.de
(End) Patricia Vannier [CDS] 12-Aug-2021