J/A+A/690/L17 Analysis of Oosterhoff dichotomy (Luongo+, 2024)
An 'alien' called the Oosterhoff dichotomy?
Luongo E., Ripepi V., Marconi M., Prudil Z., Rejkuba M., Clementini G.,
Longo G.
<Astron. Astrophys. 690, L17 (2024)>
=2024A&A...690L..17L 2024A&A...690L..17L (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Stars, variable ; Stars, distances ;
Proper motions ; Photometry ; Optical
Keywords: stars: variables: RR Lyrae - globular clusters: general -
Galaxy: halo - Galaxy: kinematics and dynamics - Galaxy: structure
Abstract:
In this Letter we investigate the origin of the Oosterhoff dichotomy
in light of recent discoveries related to several ancient merging
events of external galaxies with the Milky Way (MW). In particular, we
aim to clarify if the subdivision in terms of the Oosterhoff type
between Galactic globular clusters (GGCs) and field RR Lyrae (RRLs)
can be traced back to one or more ancient galaxies that merged with
the MW in its past.
We first explored the association of GGCs with the past merging events
according to different literature studies. Subsequently, we compiled
the positions, proper motions, and radial velocities of 10138 field
RRL variables from Gaia Data Release 3. To infer the distances, we
adopted the MG-[Fe/H] relation, with [Fe/H] values estimated via
empirical relationships involving individual periods and Fourier
parameters. We then calculated the orbits and the integrals of motion
using the Python library Galpy for the whole sample. By comparing the
location of the field RRLs in the energy-angular momentum diagram
with that of the GGCs, we determined their likely origin. Finally,
using Gaia G-band light curves, we determined the Oosterhoff types of
our RRL stars based on their location in the Bailey diagram.
The analysis of the Bailey diagrams for Galactic RRL stars and GGCs
associated with an "in situ" versus "accreted" halo origin
shows remarkable differences. The in situ sample shows a wide range of
metallicities with a continuous distribution and no sign of the
Oosterhoff dichotomy. Conversely, the accreted RRLs clearly show the
Oosterhoff dichotomy and a significantly smaller dispersion in
metallicity. Our results suggest that the Oosterhoff dichotomy was
imported into the MW by the merging events that shaped the Galaxy.
Description:
We adopted the GGCs inventory and relative fundamental parameters
listed by Baumgardt and collaborators3 (B&Co here after; see also
Baumgardt & Vasiliev 2021MNRAS.505.5957B 2021MNRAS.505.5957B; Vasiliev & Baumgardt,
2021MNRAS.505.5978V 2021MNRAS.505.5978V, Cat. J/MNRAS/505/5978).
In addition to the GGC sample, we also examined field RRLs.
Collecting the six parameters needed to study the dynamics of these
objects is not as straightforward as for the GGCs because there is no
single database that lists all the necessary information.
Our final sample of field RRLs includes 10138 variable stars. Their
identifications, positions, metallicities, Fourier amplitudes, and
other parameters are listed in Table B.7.
The adopted data for the RRLs in GGCs are shown in Table B.8. The
classification of the GGCs into in situ and accreted populations is
the same as in the previous sections (see Table B.6).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tableb6.dat 93 158 Considered GGCs
tableb7.dat 212 10138 Data of the field RRLs used in the paper
tableb8.dat 84 1156 Data for the RRLs in GGCs
--------------------------------------------------------------------------------
See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
V/150 : Updated catalog of variable stars in globular clusters
(Clement+ 2017)
J/MNRAS/505/5978 : Gaia EDR3 view on Galactic globular clusters
(Vasiliev+, 2021)
Byte-by-byte Description of file: tableb6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Name Name of the GGCs from B&Co as referred
in the paper (Name)
14 I1 --- In-situ/Acc [0/1]? Classification of GGCs according to
Belokurov & Kravtsov (2024MNRAS.528.3198B 2024MNRAS.528.3198B)
in situ=1 accreted=0 (In-situ/Acc.)
16 I1 --- OoType [0/2] Oo type lists the classification of
GGCs in Oosterhoff types (Oo_type) (1)
18- 20 A3 --- Prog Classification of GGCs according to
Callingham et al. (2022MNRAS.513.4107C 2022MNRAS.513.4107C)
(Prog.) (G2)
22- 23 I2 --- NRRL Number of RRLs for each GGCs collected
from Clement et al.
(2001AJ....122.2587C 2001AJ....122.2587C, Cat. V/150) (N_RRL)
25- 31 F7.3 deg RAdeg Right Ascension are given at J2000 from
B&Co as referred in the paper (RA)
33- 39 F7.3 deg DEdeg Declination are given at J2000 from
B&Co as referred in the paper (Dec)
41- 46 F6.2 kpc Dist Distance from B&Co as referred in
the paper (d)
48- 51 F4.2 kpc e_Dist Error on the distance from B&Co as
referred in the paper (error_d)
53- 59 F7.3 mas/yr pmRA Proper motion in right ascension from
B&Co as referred in the paper (pm_RA)
61- 65 F5.3 mas/yr e_pmRA Standard error of proper motion in
right ascension from B&Co as referred
in the paper (errorpmRA)
67- 73 F7.3 mas/yr pmDE Proper motion in declination from B&Co
as referred in the paper (pm_Dec)
75- 79 F5.3 mas/yr e_pmDE Standard error of proper motion in
declination from B&Co as referred
in the paper (errorpmDec)
81- 87 F7.2 km/s RV Radial velocity from B&Co as referred
in the paper (RV)
89- 93 F5.2 km/s e_RV Error on the radial velocity from B&Co
as referred in the paper (error_RV)
--------------------------------------------------------------------------------
Note (1): according to van den Bergh (2011PASP..123.1044V 2011PASP..123.1044V) and
Stobie (1971ApJ...168..381S 1971ApJ...168..381S) as follows:
0 = no-classification
1 = OoI
2 = OoII
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tableb7.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- GaiaDR3 Unique source identifier from Gaia DR3
(source_id)
21- 28 F8.4 deg RAdeg Right ascension (ICRS) at Ep=2016.0 from
Gaia DR3 (RA)
30- 37 F8.4 deg DEdeg Declination (ICRS) at Ep=2016.0 from
Gaia DR3 (Dec)
39- 44 F6.3 kpc Dist Distance calculated as described in
Sect. 3.1 of the paper (d)
46- 51 F6.3 kpc e_Dist Uncertainty on the distance calculated as
described in Sect. 3.1 of the paper
(error_d)
53- 60 F8.3 mas/yr pmRA Proper motion in right ascension from
Gaia DR3 (pm_RA)
62- 66 F5.3 mas/yr e_pmRA Standard error of proper motion in right
ascension from Gaia DR3 (errorpmRA)
68- 75 F8.3 mas/yr pmDE Proper motion in declination from Gaia DR3
(pm_DEC)
77- 81 F5.3 mas/yr e_pmDE Standard error of proper motion in
declination from Gaia DR3 (errorpmDEC)
83- 88 F6.1 km/s RV Radial velocity collected as reported in
Appendix A (RV)
90- 93 F4.1 km/s e_RV Uncertainty on the radial velocity
calculated as described in Appendix A of
the paper (error_RV)
95-100 F6.3 mag Gmag G-band magnitude from Gaia DR3 (G)
102-106 F5.3 mag e_Gmag Error of G-band magnitude from Gaia DR3
(error_G)
108-112 F5.2 --- [Fe/H] Metallicity calculated as described in
Sect. 3.1 of the paper ([Fe/H])
114-119 F6.3 mag GMAG G-band absolute magnitude calculated as
described in Sect. 3.1 of the paper (M_G)
121-125 F5.3 d Per Periods from Gaia DR3 (Period)
127-131 F5.3 --- R21 Fourier decomposition parameter r21G:
A2/A1 (for G band) from Gaia DR3 (R_21)
133-137 F5.3 --- e_R21 Uncertainty on the r21G parameter:
A2/A1 (for G band) from Gaia DR3
(errorR21)
139-143 F5.3 --- R31 Fourier decomposition parameter r31G:
A3/A1 (for G band) from Gaia DR3 (R_31)
145-149 F5.3 --- e_R31 Uncertainty on the r31G parameter: A3/A1
(for G band) from Gaia DR3 (errorR31)
151-155 F5.3 --- Phi21 Fourier decomposition parameter phi21G:
phi2-2*phi1 (for G band) from Gaia DR3
(Phi_21)
157-161 F5.3 --- e_Phi21 Uncertainty on the phi21G parameter:
phi2-2*phi1 (for G band) from Gaia DR3
(errorPhi21)
163-167 F5.3 --- Phi31 Fourier decomposition parameter phi31G:
phi3-3*phi1 (for G band) from Gaia DR3
(Phi_31)
169-173 F5.3 --- e_Phi31 Uncertainty on the phi31G parameter:
phi3-3*phi1 (for G band) from Gaia DR3
(errorPhi31)
175-179 F5.3 mag AmpG Peak-to-peak amplitude of the G band light
curve from Gaia DR3 (Amp(G))
181-185 F5.3 mag e_AmpG Uncertainty on the Amp(G) parameter from
Gaia DR3 (error_Amp(G))
187-192 F6.3 mag AG Interstellar absorption in the G-band from
Gaia DR3 (A(G))
194-202 F9.3 mag e_AG Error on the interstellar absorption in the
G-band from Gaia DR3 (error_A(G))
204 I1 --- In-situ/Acc [0/1] In situ or accreted provides the
classification (In-Situ/Acc.) (1)
206-208 A3 --- Prog Most probable class assigned in terms of
Callingham et al. (2022MNRAS.513.4107C 2022MNRAS.513.4107C)
progenitors obtained in Sect. 3.2 of
the paper (Prog.) (G2)
210-212 A3 --- AltProg Secondary probable class assigned in terms
of Callingham et al. (2022MNRAS.513.4107C 2022MNRAS.513.4107C)
progenitors obtained in Sect. 3.2 of the
paper (Alt. Prog.) (G2)
--------------------------------------------------------------------------------
Note (1): in terms of in situ versus accreted populations by Belokurov &
Kravtsov (2024MNRAS.528.3198B 2024MNRAS.528.3198B), as determined in Sect. 3.2 of the paper
(in situ=1; accreted=0) (In-Situ/Acc.)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tableb8.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- GaiaDR3 Unique source identifier from Gaia DR3
(source_id)
21- 28 A8 --- Name Name of the GGCs from Clement et al.
(2001AJ....122.2587C 2001AJ....122.2587C, Cat. V/150) (Name)
30- 36 A7 --- Var RRL identification within the cluster from
Clement et al. (2001AJ....122.2587C 2001AJ....122.2587C,
Cat. V/150) (Var)
38 I1 --- In-situ/Acc [0/1] Classification of GGCs according to
Belokurov & Kravtsov (2024MNRAS.528.3198B 2024MNRAS.528.3198B)
in situ=1 accreted=0 (In-situ/Acc.)
40- 42 A3 --- Prog Classification of GGCs according to
Callingham et al. (2022MNRAS.513.4107C 2022MNRAS.513.4107C),
(Prog.) (G2)
44- 51 F8.4 deg RAdeg Right ascension (ICRS) at Ep=2016.0
from Gaia DR3 (RA)
53- 60 F8.4 deg DEdeg Declination (ICRS) at Ep=2016.0
from Gaia DR3 (Dec)
62- 66 F5.3 d Per Periods from Gaia DR3 (Period)
68- 72 F5.3 mag AmpG Peak-to-peak amplitude of the G band light
curve from Gaia DR3 (Amp(G))
74- 78 F5.3 mag e_AmpG Uncertainty on the Amp(G) parameter from
Gaia DR3 (error_Amp(G))
80- 84 F5.2 --- [Fe/H] Metallicity from Harris
(1996AJ....112.1487H 1996AJ....112.1487H, Cat. VII/195)
([Fe/H])
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Global notes:
Note (G2): Meaning of the acronyms as follows:
G-E = Gaia-Enceladus
H-E = Ungrouped/High Energy
H99 = Helmi Streams
L-E = Kraken/Low-Energy
M-B = Main-Bulge
M-D = Main-Disk
Sag = Sagittarius
Seq = Sequoia
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Acknowledgements:
Emanuela Luongo, emanuela.luongo(at)inaf.it
(End) Patricia Vannier [CDS] 03-Oct-2024