J/A+A/646/A99 Gaia DR2 Monoceros and ACS candidates (Ramos+, 2021)
The outer disc in shambles:
Blind detection of Monoceros and the ACS with Gaia's astrometric sample.
Ramos P., Antoja T., Mateu C., Anders F., Laporte C. F. P.,
Carballo-Bello J.A., Famaey B., Ibata R.
<Astron. Astrophys. 646, A99 (2021)>
=2021A&A...646A..99R 2021A&A...646A..99R (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Stars, giant ; Proper motions
Keywords: Galaxy: kinematics and dynamics - Galaxy: formation - Galaxy: halo -
astrometry
Abstract:
The Gaia astrometric sample allows us to study the outermost Galactic
disc, the halo, and their interface. It is precisely at the very edge
of the disc where the effects of external perturbations are expected
to be the most noticeable.
Our goal is to detect the kinematic substructure present in the halo
and at the edge of the Milky Way (MW) disc and provide observational
constraints on their phase-space distribution. We download, one HP at
a time, the proper motion histogram of distant stars, to which we
apply a wavelet transformation to reveal the significant
overdensities. We then analyse the large coherent structures that
appear in the sky.
We reveal a sharp yet complex anticentre dominated by Monoceros (MNC)
and the Anticentre Stream (ACS) in the north - which we find have
intensities comparable to the Magellanic Clouds and the Sagittarius
stream - and by MNC South and TriAnd at negative latitudes. Our method
allows us to perform a morpho-logical analysis of MNC and the ACS,
both of which span more than 100° in longitude, and to provide a
high purity sample of giants with which we track MNC down to latitudes
as low as ∼5°. Their colour-magnitude diagram is consistent with
extended structures at a distance of ∼10-11kpc that originated in the
disc, with a very low ratio of RR-Lyrae over M giants, and with
kinematics compatible with the rotation curve at those distances or
slightly slower.
We present a precise characterisation of MNC and the ACS, two
previously known structures that our method reveals naturally,
allowing us to detect them without limiting ourselves to a particular
stellar type and, for the first time, using only kinematics. Our
results will allow future studies to model their chemo-dynamics and
evolution, thus constraining some of the most influential processes
that shaped the MW.
Description:
In this paper we have compiled a list of candidate members for the
Monoceros and the Anticentre stream using our kinematic detection
method based on the wavelet transformation. Each star has its the
source_id, positions and proper motions - with its errors - in
equatorial coordinates, as well as the magnitude and colour from Gaia
DR2, and the computed extinction in the G band from the Schlegel-98
maps.
mnc.dat:
This table contains the list of 10079 Monoceros giant stars
kinematically selected with our method.
acs.dat:
This table contains the list of 2104 Anticentre stream giant stars
kinematically selected with our method.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
acs.dat 204 2104 ACS Gaia DR2 sample
mnc.dat 204 10079 Monoceros Gaia DR2 sample
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
Byte-by-byte Description of file: acs.dat mnc.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- GaiaDR2 Gaia DR2 source ID
21- 38 F18.14 deg RAdeg Right ascension (ICRS) at Ep=2015.5
40- 57 F18.15 deg DEdeg Declination (ICRS) at Ep=2015.5
59- 80 F22.19 mas/yr pmRA* Proper motion in right ascension direction
(pmRA*cosDE)
82-101 F20.18 mas/yr e_pmRA* Standard error of pmRA*
103-124 F22.19 mas/yr pmDE Proper motion in declination direction
126-145 F20.18 mas/yr e_pmDE Standard error of pmDE
147-164 F18.15 mag Gmag G-band mean magnitude
166-183 F18.16 mag BP-RP BP-RP colour index
185-204 F20.18 mag AG Estimated extinction in G-band
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Acknowledgements:
Pau Ramos, p.ramos(at)unistra.fr
(End) Patricia Vannier [CDS] 18-Jan-2021