J/A+A/687/A312 Kinematics of bulge RR Lyrae stars (Olivares Carvajal+, 2024)
Comparing bulge RR Lyrae stars with bulge giants. Insight from 3D kinematics.
Olivares Carvajal J., Zoccali M., De Leo M., Contreras Ramos R., Quezada C.,
Rojas-Arriagada A., Valenti E., Albarracin R., Valenzuela Navarro A.
<Astron. Astrophys. 687, A312 (2024)>
=2024A&A...687A.312O 2024A&A...687A.312O (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Stars, variable ; Radial velocities ; Optical
Stars, distances ; Photometry, infrared ; Abundances, [Fe/H]
Keywords: surveys - stars: variables: RR Lyrae - Galaxy: bulge -
Galaxy: formation - Galaxy: kinematics and dynamics -
Galaxy: structure
Abstract:
The structure and kinematics of the old component of the Galactic
bulge are still a matter of debate. It is clear that the bulk of the
bulge as traced by red clump stars includes two main components, which
are usually identified as the metal-rich and metal-poor components.
They have different shapes, kinematics, mean metallicities, and
alpha-element abundances. It is our current understanding that they
are associated with a bar and a spheroid, respectively. On the other
hand, RR Lyrae variables trace the oldest population of the bulge.
While it would be natural to think that they follow the structure and
kinematics of the metal-poor component, the data analysed in the
literature show conflicting results.
We aim to derive a rotation curve for bulge RR Lyrae stars in order to
determine that the old component traced by these stars is distinct
from the two main components observed in the Galactic bulge.
This paper combines APOGEE-2S spectra with OGLE-IV light curves,
near-IR photometry, and proper motions from the VISTA Variables in the
Via Lactea survey for 4193 RR Lyrae stars. Six-dimensional phase-space
coordinates were used to calculate orbits within an updated Galactic
potential and to isolate the stars.
The stars that stay confined within the bulge represent 57% of our
sample. Our results show that bulge RR Lyrae variables rotate more
slowly than metal-rich red clump stars and have a lower velocity
dispersion. Their kinematics is compatible with them being the
low-metallicity tail of the metal-poor component. We confirm that a
rather large fraction of halo RR Lyrae stars pass by the bulge within
their orbits, increasing the velocity dispersion. A proper orbital
analysis is therefore critical to isolate bona fide bulge variables.
Finally, bulge RR Lyrae seem to trace a spheroidal component, although
the current data do now allow us to reach a firm conclusion about the
spatial distribution.
Description:
We present the results of a study of RR Lyrae stars in the bulge
region of the Galaxy presented in the OGLE-IV catalogue. These stars
have also spectra in the APOGEE Data Release 17. Most of the stars
have also near-infrared photometric data in the VVV survey. We
presented in table1.dat all the observational parameters derived from
the different surveys, which are helpful to obtain the orbital
parameters with their respective error. In table2.dat, we put the
results from the orbital analysis that we used to select the RR Lyraes
that are bonafide members of the bulge/bar region.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 125 4193 Observational parameters of the RRLs in our sample
table2.dat 59 4193 Orbital parameters derived for the RRLs
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See also:
J/AcA/69/321 : OGLE RR Lyrae stars in Galactic bulge & disk (Soszynski+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- OGLE OGLE identifier, OGLE BLG-RRLYR-NNNNN in Simbad
8- 17 F10.6 deg RAdeg Right ascension (J2000)
20- 30 F11.7 deg DEdeg Declination (J2000)
32- 37 F6.1 km/s Vsyst Systemic radial velocity
40- 43 F4.1 km/s e_Vsyst Systemic radial velocity error
46- 51 F6.1 km/s VGC Galactocentric radial velocity
54- 59 F6.3 mag Ksmag Mean magnitude in the Ks band
62- 67 F6.3 mag Jmag Mean magnitude in the J band
70- 75 F6.2 [-] [Fe/H] ?=- Photometric metallicity
77- 80 F4.2 [-] e_[Fe/H] ?=- Photometric metallicity error
83- 89 F7.3 mas/yr pml Proper motion in Galactic longitude
91- 95 F5.2 mas/yr e_pml Proper motion error in Galactic longitude
98-104 F7.3 mas/yr pmb Proper motion in Galactic latitude
107-111 F5.2 mas/yr e_pmb Proper motion error in Galactic latitude
114-117 F4.1 kpc Dist Distance
120-122 F3.1 kpc e_Dist ?=- Distance error
125 A1 --- Flag [012] Quality flag (1)
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Note (1): Flag as follows:
0 = Excellent quality Ks band light curve
1 = Intermediate quality Ks band light curve
2 = Bad quality Ks band light curve
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- OGLE OGLE identifier
8- 17 F10.2 km2/s2 Etot Total energy
20- 26 F7.1 kpc.km/s Lz Angular momentum in Z
29- 33 F5.1 kpc Apo Apocenter radius
35- 38 F4.1 kpc Peri Pericenter radius
41- 46 F6.1 kpc Zmax Maximun height
49- 52 F4.2 --- Ecc Eccentricity
55- 59 F5.1 % Time2.5 Time percentage within a radius of 2.5kpc
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Acknowledgements:
Julio Olivares Carvajal, jrolivares(at)uc.cl
(End) Julio Olivares Carvajal [PUC/MAS], Patricia Vannier [CDS] 29-May-2024