J/MNRAS/485/4726 An all-sky view of the Orphan Stream (Koposov+, 2019)
Piercing the Milky Way: an all-sky view of the Orphan Stream.
Koposov S.E., Belokurov V., Li T.S., Mateu C., Erkal D., Grillmair C.J.,
Hendel D., Price-Whelan A.M., Laporte C.F.P., Hawkins K., Sohn S.T.,
del Pino A., Evans N.W., Slater C.T., Kallivayalil N., Navarro J.F.,
(the Oats: Orphan Aspen Treasury Collaboration)
<Mon. Not. R. Astron. Soc., 485, 4726-4742 (2019)>
=2019MNRAS.485.4726K 2019MNRAS.485.4726K (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Stars, variable ; Stars, halo ; Positional data ;
Stars, distances ; Proper motions ; Optical
Keywords: Galaxy: halo - Galaxy: kinematics and dynamics - Galaxy: structure -
galaxies: dwarf - galaxies: structure
Abstract:
We use astrometry, broad-band photometry, and variability information
from the Data Release 2 of ESA's Gaia mission (GDR2) to identify
members of the Orphan Stream (OS) across the whole sky. The stream is
traced above and below the celestial equator and in both Galactic
hemispheres, thus increasing its visible length to ∼210°
equivalent to ∼150kpc in physical extent. Taking advantage of the
large number of RR Lyrae stars in the OS, we extract accurate
distances and proper motions across the entire stretch of the tidal
debris studied. As delineated by the GDR2 RR Lyrae, the stream
exhibits two prominent twists in its shape on the sky which are
accompanied by changes in the tangential motion. We complement the RR
Lyrae maps with those created using GDR2 Red Giants and the DECam
Legacy Survey Main Sequence Turn-Off stars. The behaviour of the OS
track on the sky is consistent across all three tracers employed. We
detect a strong non-zero motion in the across-stream direction for a
substantial portion of the stream. Such a misalignment between the
debris track and the streaming velocity cannot be reproduced in a
static gravitational potential and signals an interaction with a
massive perturber.
Description:
We select a high-purity all-sky sample of RRL candidate stars from two
separate source catalogues released as part of the Gaia DR2 (Gaia
Collaboration et al. 2018A&A...616A...1G 2018A&A...616A...1G, Cat. I/345). More precisely,
tables vari classifier result and vari rrlyrae (see Clementini et al.
2019A&A...622A..60C 2019A&A...622A..60C, Cat. J/A+A/622/A60; Holl et al.
2018A&A...618A..30H 2018A&A...618A..30H) are joined, removing the duplicates, and the
stellar astrometry and photometry are obtained from the main gaia
source catalogue.
To select the likely Orphan Stream (OS) members, we translate the
stellar celestial coordinates in equatorial system (α,δ)
into a new coordinate system (Φ1,Φ2) aligned with the
stream (see e.g. Koposov et al. 2010ApJ...712..260K 2010ApJ...712..260K). More
specifically, based on the OS detections reported in Belokurov et al.
(2007ApJ...658..337B 2007ApJ...658..337B), Grillmair (2006ApJ...645L..37G 2006ApJ...645L..37G), and Newberg et
al. (2010ApJ...711...32N 2010ApJ...711...32N), we use a great circle with a pole at
(αOS,δOS)=(72°,-14°). The origin of this
stream's coordinate system is chosen to be at
(α0,δ0)=(191.10487°,-62.86084°), near the
position where the equator of this coordinate system (and the OS)
crosses the Galactic plane. We provide the rotation matrix to this
coordinate system in Appendix B. Finally, Φ1 increases in the
direction of the stream's motion, i.e. from the Galactic South to the
Galactic North.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 104 109 The subset of the likely Orphan RRL selected
based on their distance, proper motion, and
position on the sky
table5.dat 50 109 Adopted light-curve periods and Bailey types
for the likely Orphan RRL members
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/A+A/622/A60 : Gaia DR2 misclassified RR Lyrae list (Clementini+, 2019)
J/AJ/153/204 : RR Lyrae stars from the PS1 3π survey (Sesar+, 2017)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right ascension (ICRS) at Ep=2015.5 (1)
11- 19 F9.5 deg DEdeg Declination (ICRS) at Ep=2015.5 (1)
21- 27 F7.5 --- EBV Colour excess E(B-V)
29- 36 F8.5 mas/yr pmRA Proper motion in right ascension (1)
38- 44 F7.5 mas/yr e_pmRA Error on pmRA (1)
46- 53 F8.5 mas/yr pmDE Proper motion in declination (1)
55- 61 F7.5 mas/yr e_pmDE Error on pmDE (1)
63- 70 F8.5 --- pmRApmDEcor Correlation between proper motion in right
ascension and in declination (1)
72- 79 F8.5 mag Gmag Gaia DR2 G-band magnitude (1)
81- 87 F7.5 mag BP-RP Gaia DR2 BP-RP colour index (1)
89- 95 F7.5 --- E(BP/RP) Gaia DR2 BP/RP excess factor (1)
97-104 F8.5 kpc Dist Heliocentric distance
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Note (1): Values from Gaia DR2 (Gaia Collaboration 2018A&A...616A...1G 2018A&A...616A...1G,
Cat. I/345)
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- GaiaDR2 Gaia DR2 source identifier
21- 34 F14.12 d Period ? Light-curve period
36- 39 A4 --- Type Bailey type
41 I1 --- r_Type References for Type (1)
43- 50 A8 --- Note Reference legend (Gaia, PS1 or ThisWork)
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Note (1): References as follows:
1 = Clementini et al. (2019A&A...622A..60C 2019A&A...622A..60C, Cat. J/A+A/622/A60) (Gaia DR2)
2 = Sesar et al. (2017AJ....153..204S 2017AJ....153..204S, Cat. J/AJ/153/204) (Pan-STARRS DR1)
3 = This work
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 07-Oct-2022