J/MNRAS/513/1958 Study of RR Lyrae stars in MW substructures (Wang+, 2022)
Probing the Galactic halo with RR Lyrae stars - II. The substructures of
the Milky Way.
Wang F., Zhang H.-W., Xue X.-X., Huang Y., Liu G.-C., Zhang L., Yang C.-Q.
<Mon. Not. R. Astron. Soc. 513, 1958-1971 (2022)>
=2022MNRAS.513.1958W 2022MNRAS.513.1958W (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Milky Way ; Stars, metal-deficient ;
Positional data ; Stars, distances ; Radial velocities ;
Proper motions ; Abundances, [Fe/H] ; Regional catalog ;
Photometry ; Spectroscopy ; Optical ; Infrared
Keywords: stars: variables: RR Lyrae - Galaxy: evolution - Galaxy: formation -
Galaxy: halo
Abstract:
We identify substructures of the Galactic halo using 3003 type ab RR
Lyrae stars with six-dimensional position-velocity information from
the Sloan Digital Sky Survey, the Large Sky Area Multi-Object Fiber
Spectroscopic Telescope and the Gaia Early Data Release 3. Based on
this information, we define the separation of any two of the stars in
the integrals of motion space and we identify substructures by
utilizing the friends-of-friends algorithm. We identify members
belonging to several known substructures: the Sagittarius stream, the
Gaia- Enceladus-Sausage (GES), the Sequoia and the Helmi streams. In
addition to these known substructures, there are three other
substructures possibly associated with globular clusters NGC 5272,
6656 and 5024, respectively. Finally, we also find three remaining
unknown substructures, one of which has large angular momentum and a
mean metallicity -2.13 dex, which may be a new substructure. As for
the GES, we find that it accounts for a large part of substructures in
the inner halo and the apocentre distance is in the range 10-34 kpc,
which suggests that the GES is mainly distributed in the inner halo.
The near one-third proportion of the GES and the peak value of 20 kpc
of the apocentre distance suggest that the GES could account for the
break in the density profile of the Galactic halo at the
Galactocentric distance ∼20-25 kpc. The similarity when comparing the
kinematic properties of the GES with the Hercules-Aquila Cloud and
Virgo Overdensity suggests that the three substructures may have
similar origins.
Description:
RRLs are old and metal-poor variable stars with a well-defined
luminosity-metallicity relation in the optical band and
period-metallicity-luminosity (PMZ) relation in the infrared band;
thus, they are good standard candles. These properties indicate that
RRLs are ideal tracers to study the Galactic halo. However, because of
the pulsation of RRLs, the radial velocities will vary with the
pulsation phase.
In this work, the RRL catalogue we have adopted is from Liu et al.
(2020ApJS..247...68L 2020ApJS..247...68L, Cat. J/ApJS/247/68). They publicated a catalogue
of 5290 RRLs with metallicities estimated from spectra of the LAMOST
and SDSS/SEGUE surveys. They also estimated the systemic radial
velocities Vlos for 3642 objects by fitting empirical templates to the
velocity curves of the multiple measurements. We also collect the RRL
catalogue from Gaia (Clementini et al. 2019A&A...622A..60C 2019A&A...622A..60C, Cat.
J/A+A/622/A60), the ASAS-SN (Jayasinghe et al. 2018MNRAS.477.3145J 2018MNRAS.477.3145J,
Cat. II/366), the PS1 (Sesar et al. 2017AJ....153..204S 2017AJ....153..204S, Cat.
J/AJ/153/204), Catalina Survey and the GCVS. In the time, we utilize
the spectra from SDSS DR12 (Alam et al. 2015ApJS..219...12A 2015ApJS..219...12A, Cat.
V/147) and a larger quantity of spectra from LAMOST DR6. Thus, we
measure the radial velocity of each single-exposure spectrum from
three Balmer lines. Next, by cross-matching with the Gaia EDR3
catalogue (Brown et al. 2021A&A...649A...1G 2021A&A...649A...1G, Cat. I/350), we obtain
proper motions for these sample stars. We select the Gaia EDR3 data
with ruwe < 1.4 to remove stars with dubious astrometry. Using the
Python package GALPY, we calculate the Galactic longitude l, latitude
b and tangential velocities (Vl, Vb) based on the right ascension RA,
declination Dec, proper motions and distances. With the solar peculiar
velocity and the LSR velocity, all velocities of stars are converted
to the Galactic standard of rest (GSR) frame.
Finally, we obtain a sample of 3065 RRab stars with full 6D
information (3D positions and 3D velocities) as exposed in table1.dat
for the parameters and corresponding uncertainties of our sample, (i.e
refer to section 2.2 RRL sample). Secondly, we aim to identify
substructures in the IoM space using orbital parameters regrouping
stars with similar characteristics with the help of FoF group-finding
algorithm (i.e see section 3.1 Integrals of metion and section FoF
algorithm). We exposed every results in the section 4 Results and in
the table4.dat where 11 main substructures and their membership stars
are revealed via orbital parameters, total mechanical energy and
angular momentum values.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 114 3065 Parameters and properties of our all 3065
RRab stars
table4.dat 85 1411 The integrals of motion (IoM) orbital parameters
of all RRab stars in the substructures
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See also:
J/ApJS/247/68 : Probing the Gal. halo with RR Lyrae stars. I. (Liu+, 2020)
J/A+A/622/A60 : Gaia DR2 misclassified RR Lyrae list (Clementini+, 2019)
II/366 : ASAS-SN catalog of variable stars (Jayasinghe+, 2018-2020)
J/AJ/153/204 : RR Lyrae stars from the PS1 3π survey (Sesar+, 2017)
V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
J/ApJ/763/32 : Galactic halo RRab stars from CSS (Drake+, 2013)
J/ApJ/765/154 : RR Lyrae stars in the Catalina Sky Survey (Drake+, 2013)
J/ApJS/213/9 : Catalina Surveys periodic variable stars (Drake+, 2014)
J/MNRAS/469/3688 : CSS Periodic Variable Star Catalogue (Drake+, 2017)
J/MNRAS/446/2251 : Southern Catalina Survey type-ab RR Lyrae (Torrealba+, 2015)
J/AJ/146/21 : LINEAR. II. Catalog of RR Lyrae stars (Sesar+, 2013)
B/gcvs : General Catalogue of Variable Stars (Samus+, 2007-2017)
J/MNRAS/424/2528 : RR Lyrae in SDSS Stripe 82 (Suveges+, 2012)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- ID Index ID number (index)
6- 15 F10.6 deg RAdeg Right ascension (J2000) (ra)
17- 26 F10.6 deg DEdeg Declination (J2000) (dec)
28- 33 F6.3 kpc Dist Distance (d)
35- 39 F5.3 kpc e_Dist Mean uncertainty of d (d_err)
41- 48 F8.3 km/s Vlos Line of sight radial velocity (Vlos)
50- 55 F6.3 km/s e_Vlos Mean uncertainty of Vlos (Vlos_err)
57- 63 F7.3 mas/yr pmRA Proper motion in right ascension direction
(pmra)
65- 69 F5.3 mas/yr e_pmRA Mean uncertainty of pmRA (pmra_err)
71- 77 F7.3 mas/yr pmDE Proper motion in declination direction (pmdec)
79- 83 F5.3 mas/yr e_pmDE Mean uncertainty of pmDE (pmdec_err)
85- 90 F6.3 [Sun] [Fe/H] Iron to hydrogen ratio abundance (feh)
92- 96 F5.3 [Sun] e_[Fe/H] Mean uncertainty of [Fe/H] (feh_err)
98- 105 F8.6 d Per Variation period (period)
107- 114 A8 --- Ref Source reference (source) (1)
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Note (1): Source references are as follows:
Catalina = For Catalina Survey (Drake et al. 2013ApJ...763...32D 2013ApJ...763...32D,
Cat. J/ApJ/763/32 ; 2013ApJ...765..154D 2013ApJ...765..154D,
Cat. J/ApJ/765/154 ; 2014ApJS..213....9D 2014ApJS..213....9D,
Cat. J/ApJS/213/9 ; 2017MNRAS.469.3688D 2017MNRAS.469.3688D,
Cat. J/MNRAS/469/3688; Torrealba et al.
2015MNRAS.446.2251T 2015MNRAS.446.2251T, Cat. J/MNRAS/446/2251), 2010 objects
in our sample
Gaia = For Gaia DR2 misclassified RR Lyrae list (Clementini et al.
2019A&A...622A..60C 2019A&A...622A..60C, Cat. J/A+A/622/A60) and gaia EDR3
catalogue (Brown et al. 2021A&A...649A...1G 2021A&A...649A...1G, Cat. I/350),
634 objects in our sample
LINEAR = For LINEAR. II. Catalog of RR Lyrae stars (Sesar et al.
2013AJ....146...21S 2013AJ....146...21S Cat. J/AJ/146/21), 189 objects in our
sample
GCVS = For General Catalogue of Variable Stars (Samus et al.
2017ARep...61...80S 2017ARep...61...80S, Cat. B/gcvs), 58 objects in our
sample
ASASSN = For ASAS-SN catalog of variable stars (Jayasinghe et al.
2018MNRAS.477.3145J 2018MNRAS.477.3145J, Cat. II/366), 57 objects in our
sample
PS1 = For RR Lyrae stars from the PS1 3π survey (Sesar et al.
2017AJ....153..204S 2017AJ....153..204S, Cat. J/AJ/153/204), 51 object in our
sample
Stripe82 = For RR Lyrae in SDSS Stripe 82 (Suveges et al.
2012MNRAS.424.2528S 2012MNRAS.424.2528S, Cat. J/MNRAS/424/2528), 37 object
in our sample
QUEST = QUEST RR Lyrae surveys, 29 object
in our sample
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- ID Index ID number (index)
6- 11 F6.2 deg l-orb IoM direction of the orbital pole galactic
longitude (l_orbit)
13- 18 F6.2 deg b-orb IoM direction of the orbital pole galactic
latitude (b_orbit)
20- 24 F5.2 kpc a IoM semimajor axis of the orbit (a)
26- 29 F4.2 --- e IoM eccentricity (e)
31- 36 F6.2 deg l-apo IoM angle between apocenter and the
projection of X-axis on the orbital plane
(lapo_orbit)
38- 47 F10.2 km2/s2 E IoM total mechanical energy (E)
49- 55 F7.2 kpc.km/s L IoM angular momentum (L)
57- 64 F8.2 kpc.km/s Lx IoM x-component of L (Lx)
66- 73 F8.2 kpc.km/s Ly IoM y-component of L (Ly)
75- 82 F8.2 kpc.km/s Lz IoM z-component of L (Lz)
84- 85 I2 --- Memb [0/10] Index denotes the structure membership
(label) (1)
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Note (1): Substructures are as follows:
0 = Sagittarius leading arm, 108 objects in our sample
1 = Sagittarius trailing arm, 37 objects in our sample
2 = Gaia-Enceladus-Sausage, 1067 objects in our sample
3 = Sequoia stream, 99 objects in our sample
4 = Helmi stream, 32 objects in our sample
5 = Likely to be associated with the globular cluster NGC 5272,
31 objects in our sample
6 = Likely to be associated with the globular cluster NGC 6656,
12 objects in our sample
7 = Likely to be associated with the globular cluster NGC 5024,
6 objects in our sample
8 = Group72 with very special kinematic properties not to be
related to the known large substructures or globular
clusters, 5 objects in our sample
9 = Group79 with very special kinematic properties not to be
related to the known large substructures or globular
clusters, 5 objects in our sample
10 = Group80 with very special kinematic properties not to be
related to the known large substructures or globular
clusters, 9 objects in our sample
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History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 13-Dec-2024