J/A+A/670/L2 Gaia DR3 of substructure in the stellar halo (Dodd+, 2023)
The Gaia DR3 view of dynamical substructure in the stellar halo near the Sun.
Dodd E., Callingham T.M., Helmi A., Matsuno T., Ruiz-Lara T., Balbinot E.,
Loevdal S.
<Astron. Astrophys. 670, L2 (2023)>
=2023A&A...670L...2D 2023A&A...670L...2D (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Optical ; Space velocities ; Stars, distances
Keywords: Galaxy: kinematics and dynamics - Galaxy: halo - Galaxy: structure
Abstract:
The debris from past merger events is expected and, to some extent,
know n to populate the stellar halo near the Sun. We aim to identify
and characterise such merger debris using Gaia DR3 data supplemented
by metallicity and chemical abundance information from LAMOST LRS and
APOGEE for halo stars within 2.5kpc from the Sun. We utilise a single
linkage-based clustering algorithm to identify over-densities in
Integrals of Motion space that could be due to merger debris. Combined
with metallicity information and chemical abundances, we characterise
these statistically significant over-densities. We find that the local
stellar halo contains 7 main dynamical groups, some of in-situ and
some of accreted origin, most of which are already known. We report
the discovery of a new substructure, which we name ED-1. In addition,
we find evidence for 11 independent smaller clumps, 5 of which are
new: ED-2, 3, 4, 5 and 6 are typically rather tight dynamically,
depict a small range of metallicities, and their abundances when
available, as well as their location in Integrals of Motion space,
suggest an accreted origin.The local halo contains an important amount
of substructure, of both in-situ and accreted origin.
Description:
Catalogue of substructures identified in the local stellar halo using
Gaia DR3. Stars within 5 kpc from the Sun are provided in this
catalogue, including their Gaia source_id, the distance and various
dynamics; position (x, y, z), velocity (vx, vy, vz), angular momenta
(Lz, Lperp) and energy (En). Energy is calculated for the potential
outlined in the paper. The significant overdensities from clustering
on energy and angular momenta for the stars within 2.5kpc are given
by labels_original which ranges from -1 to 90. Stars labelled as -1
are not associated to an overdensity. The paper outlines joining
clusters into groups which are given by labelsgrouporiginal ranging
from -1 to 28. The columns Dclusteroriginal and Dgrouporiginal
correspond to the Mahalanobis distance of stars in an overdensity to
the centre of the cluster or group respectively. We add additional
members to clusters out to 5kpc using a cut on the Mahalanobis
distance to the closest clusters which is given by labels_derived and
combining those cluster stars into groups is given by
labelsgroupderived. We also have an alternative way of adding
additional members to the groups out to 5kpc by using a cut on the
Mahalanobis distance to the closet group, instead of cluster, which is
given by labelsgroupadded.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
catalog.dat 311 193831 Catalogue of stellar overdensities including
Gaia DR3 source_id, dynamics and labels
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See also:
J/A+A/665/A57 : Substructure in stellar halo near the Sun. I. (Lovdal+, 2022)
Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- GaiaDR3 Gaia DR3 source_id (source_id)
21- 42 E22.19 kpc xpos x position (x)
44- 65 E22.19 kpc ypos y position (y)
67- 88 E22.19 kpc zpos z position (z)
90-113 F24.19 km/s Vx x component of velocity vector (vx)
115-137 F23.18 km/s Vy y component of velocity vector (vy)
139-160 E22.19 km/s Vz z component of velocity vector (vz)
162-181 F20.18 kpc Dist Distance from Sun (distance)
183-207 F25.19 kpc.km/s Lz z component of angular momentum (Lz)
209-229 F21.16 kpc.km/s Lperp Perpendicular component of angular
momentum (Lperp)
231-252 F22.14 km2/s2 En Energy (En)
254-255 I2 --- labelOri [-1/90] Original cluster label
(labels_original) (1)
257-258 I2 --- labelGroupOri [-1/28] Original group label
(labelsgrouporiginal) (1)
260-278 F19.17 --- DclOri Mahalanobis distance to associated
cluster (Dclusteroriginal)
280-298 F19.17 --- DgroupOri Mahalanobis distance to associated
group (Dgrouporiginal)
300-303 F4.1 --- labelsderiv [-1/90] Cluster labels after adding
members to clusters
(labels_derived) (1)
305-308 F4.1 --- labelsGroupderiv [-1/28] Group labels after adding
members to clusters
(labelsgroupderived) (1)
310-311 I2 --- labelsGroupAdded [-1/28] Group labels after adding
members to groups
(labelsgroupadded) (1)
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Note (1): Stars labelled as -1 are not associated to an overdensity.
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Acknowledgements:
Emma Dodd, dodd(at)astro.rug.nl
(End) Patricia Vannier [CDS] 02-Dec-2022