J/MNRAS/501/5981 COMBS Survey. Metal-poor bulge stars (Lucey+, 2021)
The COMBS Survey.
II. Distinguishing the metal-poor bulge from the halo interlopers.
Lucey M., Hawkins K., Ness M., Debattista V.P., Luna A., Asplund M.,
Bensby T., Casagrande L., Feltzing S., Freeman K.C., Kobayashi C.,
Marino A.F.
<Mon. Not. R. Astron. Soc., 501, 5981-5996 (2021)>
=2021MNRAS.501.5981L 2021MNRAS.501.5981L (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Stars, population II ; Radial velocities ; Milky Way ;
Optical
Keywords: stars: kinematics and dynamics - stars: Population II -
Galaxy: bulge - Galaxy: evolution
Abstract:
The metal-poor stars in the bulge are important relics of the Milky
Way's formation history, as simulations predict that they are some of
the oldest stars in the Galaxy. In order to determine if they are
truly ancient stars, we must understand their origins. Currently, it
is unclear if the metal-poor stars in the bulge ([Fe/H]←1dex) are
merely halo interlopers, a unique accreted population, part of the
boxy/peanut-shaped bulge, or a classical bulge population. In this
work, we use spectra from the VLT/FLAMES spectrograph to obtain
metallicity estimates using the Ca-II triplet of 473 bulge stars (187
of which have [Fe/H]←1dex), targeted using SkyMapper photometry.
We also use Gaia DR2 data to infer the Galactic positions and
velocities along with orbital properties for 523 stars. We employ a
probabilistic orbit analysis and find that about half of our sample
has a >50 per cent probability of being bound to the bulge, and half
are halo interlopers. We also see that the occurrence rate of halo
interlopers increases steadily with decreasing metallicity across the
full range of our sample (-3<[Fe/H]<0.5). Our examination of the
kinematics of the confined compared to the unbound stars indicates the
metal-poor bulge comprises at least two populations; those confined to
the boxy/peanut bulge and halo stars passing through the inner galaxy.
We conclude that an orbital analysis approach, as we have employed, is
important to understand the composite nature of the metal-poor stars
in the inner region.
Description:
Based on observations collected at the European Southern Observatory
under ESO programme: 089.B-069
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 428 523 Dynamical properties of our target stars
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/MNRAS/488/2283 : COMBS survey. Galactic Bulge metal-poor stars (Lucey+, 2019)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 8 F8.3 km/s Uvel U velocity (U)
10- 17 F8.3 km/s b_Uvel Lower value of U interval (U_lo)
19- 26 F8.3 km/s B_Uvel Upper value of U interval (U_hi)
28- 36 F9.3 km/s Vvel V velocity (V)
38- 46 F9.3 km/s b_Vvel Lower value of V interval (V_lo)
48- 55 F8.3 km/s B_Vvel Upper value of V interval (V_hi)
57- 64 F8.3 km/s Wvel W velocity (W)
66- 74 F9.3 km/s b_Wvel Lower value of W interval (W_lo)
76- 83 F8.3 km/s B_Wvel Upper value of W interval (W_hi)
85- 92 F8.5 pc Xpos X position (X)
94-101 F8.5 pc b_Xpos Lower value of X interval (X_lo)
103-111 F9.5 pc B_Xpos Upper value of X interval (X_hi)
113-118 F6.3 pc Ypos Y position (Y)
120-125 F6.3 pc b_Ypos Lower value of Y interval (Y_lo)
127-132 F6.3 pc B_Ypos Upper value of Y interval (Y_hi)
134-139 F6.3 pc Zpos Z position (Z)
141-147 F7.3 pc b_Zpos Lower value of Z interval (Z_lo)
149-155 F7.3 pc B_Zpos Upper value of Z interval (Z_hi)
157-165 F9.6 kpc d Distance (d)
167-175 F9.6 kpc b_d Lower value of Distance interval (d_lo)
177-186 F10.6 kpc B_d Upper value of Distance interval (d_hi)
188-192 F5.3 --- Prob Pobability that a star stays confined
to the bulge (prob)
194-202 F9.6 kpc peri Pericentre (peri)
204-211 F8.6 kpc b_peri Lower value of peri interval (peri_lo)
213-222 F10.6 kpc B_peri Upper value of peri interval (peri_hi)
224-234 F11.6 kpc api Apocentre (api)
236-244 F9.6 kpc b_api Lower value of api interval (api_lo)
246-256 F11.6 kpc B_api Upper value of api interval (api_hi)
258-266 F9.7 --- e Excentricity (e)
268-276 F9.7 --- b_e Lower value of e interval (e_lo)
278-286 F9.7 --- B_e Upper value of e interval (e_hi)
288-296 F9.6 pc zmax Maximun height above the plane (zmax)
298-306 F9.6 pc b_zmax Lower value of e zmax (zmax_lo)
308-318 F11.6 pc B_zmax Upper value of e zmax (zmax_hi)
320-327 A8 --- object Object designation (object)
329-347 I19 --- Source Gaia source ID (some erroneous identifiers)
(source_id)
349-357 F9.5 deg RAdeg Right ascension (ICRS) (ra)
359-367 F9.5 deg DEdeg Declination (ICRS) (dec)
369-377 F9.5 deg GLON [0/360] Galactic longitude (l)
379-387 F9.5 deg GLAT Galactic latitude (b)
389-393 F5.2 [-] [Fe/H] ?=- Metallicity ([Fe/H])
395-398 F4.2 [-] e_[Fe/H] ?=- Metallicity error (e_[Fe/H])
400-407 F8.3 km/s RV Radial velocity (RV)
409-413 F5.3 km/s e_RV Radial velocity error (e_RV)
415-417 I3 --- SNR Signal-to-noise ratio (SNR)
419-426 F8.6 --- RUWE Renormalised unit weight error (ruwe)
428 A1 --- Spec [GU] Spectra origin (Spec) (1)
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Note (1): Spectra origin as follows:
G = GIRAFFE spectra
U = UVES spectra
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Acknowledgements:
Madeline Lucey, m_lucey(at)utexas.edu
References:
Lucey et al., Paper I 2019MNRAS.488.2283L 2019MNRAS.488.2283L, Cat. J/MNRAS/488/2283
(End) Patricia Vannier [CDS] 16-Oct-2021