J/A+A/666/A64 Sagittarius stream with eDR3 (Ramos+, 2022)
The Sagittarius stream in Gaia Early Data Release 3 and the origin of the
bifurcations.
Ramos P., Antoja T., Yuan Z., Arentsen A., Oria P.-A., Famaey B., Ibata R.,
Mateu C., Carballo-Bello J.A.
<Astron. Astrophys. 666, A64 (2022)>
=2022A&A...666A..64R 2022A&A...666A..64R (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Populations, stellar ; Optical
Keywords: Galaxy: halo - galaxies: dwarf - astrometry
Abstract:
The Sagittarius dwarf spheroidal (Sgr) is a dissolving galaxy being
tidally disrupted by the Milky Way (MW). Its stellar stream still
poses serious modelling challenges, which hinders our ability to use
it effectively as a prospective probe of the MW gravitational
potential at large radii.
Our goal is to construct the largest and most stringent sample of
stars in the stream with which we can advance our understanding of the
Sgr-MW interaction, focusing on the characterisation of the
bifurcations.
We improved on previous methods based on the use of the wavelet
transform to systematically search for the kinematic signature of the
Sgr stream throughout the whole sky in the Gaia data. We then refined
our selection via the use of a clustering algorithm on the statistical
properties of the colour-magnitude diagrams.
Our final sample contains more than 700000 candidate stars and is
three times larger than previous Gaia samples. With it, we have been
able to detect the bifurcation of the stream in both the northern and
southern hemispheres, which requires four branches (two bright and two
faint) to fully describe the system. We present the detailed proper
motion distribution of the trailing arm as a function of the angular
coordinate along the stream, showing, for the first time, the presence
of a sharp edge (on the side of the small proper motions) beyond which
there are no Sgr stars. We also characterise the correlation between
kinematics and distance. Finally, the chemical analysis of our sample
shows that the faint branch of the bifurcation is more metal poor than
the bright. We provide analytical descriptions for the proper motion
trends as well as for the sky distribution of the four branches of the
stream.
Based on our analysis, we interpret the bifurcations as a misaligned
overlap of the material stripped at the antepenultimate pericentre
(faint branches) with the stars ejected at the penultimate pericentre
(bright branch), given that Sgr just went through its perigalacticon.
The source of this misalignment is still unknown, but we argue that
models with some internal rotation in the progenitor - at least
during the time of stripping of the stars that are now in the faint
branches - are worth exploring
Description:
773612 candidate stars in the Sagittarius stream from the Gaia eDR3
sample, classified as such based on their kinematics and photometry.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablec1.dat 255 773612 Candidate stars in the Sagittarius stream from
the Gaia eDR3 sample
--------------------------------------------------------------------------------
See also:
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
Byte-by-byte Description of file: tablec1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- GaiaEDR3 Gaia eDR3 Unique source identifier
(source_id)
21- 30 F10.7 mag Gmag G-band mean magnitude
(photgmean_mag)
32- 41 F10.7 mag BP-RP GBP minus GRP colour (bp_rp)
43- 57 F15.11 deg RAdeg Right ascension (ICRS) at Ep=2015.5
(ra)
59- 73 F15.11 deg DEdeg Declination (ICRS) at Ep=2015.5 (dec)
75- 83 F9.3 mas/yr pmRA Proper motion in right ascension
direction (J2015.5) (pmra)
85- 93 F9.3 mas/yr pmDE Proper motion in declination direction
(J2015.5) (pmdec)
95- 99 F5.3 mas/yr e_pmRA Error in pmRA (pmra_error)
101-105 F5.3 mas/yr e_pmDE Error in pmDE (pmdec_error)
107-118 F12.8 kpc DistWGBPRP ?=- Photometric distance
(only RR Lyrae.) (Dist_WGBPRP)
120-129 F10.8 kpc e_DistWGBPRP ?=- Error in distance
(only RR Lyrae) (DistWGBPRPerr)
131-143 F13.6 km/s Vlos ?=- Line of sight velocity (vlos)
145-148 A4 --- r_Vlos Source of the radal velocity
(vlos_source)
150-157 F8.5 [-] [Fe/H]APOGEE ?=- Metallicity from APOGEE
(FEH_APOGEE)
159-166 F8.5 [-] [alpha/M]APOGEE ?=- Alpha over iron from APOGEE
(ALPHAMAPOGEE)
168-173 F6.3 [-] [Fe/H]LAMOST ?=- Metallicity from LAMOST
(FEH_LAMOST)
175-180 F6.3 [-] [Fe/H]SEGUE ?=- Metallicity from SEGUE (FEH_SEGUE)
182-188 F7.3 --- SNRAPOGEE ?=- Signal to noise (APOGEE, SNREV)
(SNR_APOGEE)
190-195 F6.2 --- SNRgLAMOST ?=- Signal to noise in g-band
(LAMOST) (snrg_LAMOST)
197-203 F7.3 --- SNRSEGUE ?=- Signal to noise (SEGUE)
(SNR_SEGUE)
205-216 E12.6 --- ProbBright Probability to belong to bright arm
(Prob_bright)
218-229 E12.6 --- ProbFaint Probability to belong to faint arm
(Prob_faint)
231-242 E12.6 --- ProbSGR Probability to belong to the stream
(Prob_sgr)
244-255 E12.6 --- ProbPlx Parallax score (Prob_plx)
--------------------------------------------------------------------------------
Acknowledgements:
Pau Ramos, pramos(at)fqa.ub.edu
(End) Patricia Vannier [CDS] 03-Aug-2022