J/A+A/648/A78 Orphan stream RR Lyrae and non-variables (Prudil+, 2021)
Milky Way archaeology using RR Lyrae and type II Cepheids.
I. The Orphan stream in 7D using RR Lyrae stars.
Prudil Z., Hanke M., Lemasle B., Crestani J., Braga V.F., Fabrizio M.,
Koch-Hansen A. J., Bono G., Grebel E.K., Matsunaga N., Marengo M.,
da Silva R., Dall'Ora M., Martinez-Vazquez C.E., Altavilla G., Lala H.,
Chaboyer B., Ferraro I., Fiorentino G., Gilligan C. Nonino M., Thevenin F.
<Astron. Astrophys. 648, A78 (2021)>
=2021A&A...648A..78P 2021A&A...648A..78P (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Stars, variable ; Stars, distances ;
Radial velocities
Keywords: Galaxy: halo - Galaxy: kinematics and dynamics -
Galaxy: structure - stars: variables: RR Lyrae
Abstract:
We present a chemo-dynamical study of the Orphan stellar stream using
a catalog of RR Lyrae pulsating variable stars for which photometric,
astrometric, and spectroscopic data are available. Employing
low-resolution spectra from the Sloan Digital Sky Survey (SDSS), we
determined line-of-sight velocities for individual exposures and
derived the systemic velocities of the RR Lyrae stars. In combination
with the stars' spectroscopic metallicities and Gaia EDR3 astrometry,
we investigated the northern part of the Orphan stream. In our
probabilistic approach, we found 20 single mode RR Lyrae variables
likely associated with the Orphan stream based on their positions,
proper motions, and distances. The acquired sample permitted us to
expand our search to nonvariable stars in the SDSS dataset, utilizing
line-of-sight velocities determined by the SDSS. We found 54
additional nonvariable stars linked to the Orphan stream. The
metallicity distribution for the identified red giant branch stars and
blue horizontal branch stars is, on average, -2.13±0.05dex and
-1.87±0.14dex, with dispersions of 0.23 and 0.43dex, respectively.
The metallicity distribution of the RR Lyrae variables peaks at
-1.80±0.06dex and a dispersion of 0.25dex. Using the collected
stellar sample, we investigated a possible link between the
ultra-faint dwarf galaxy Grus II and the Orphan stream. Based on their
kinematics, we found that both the stream RR Lyrae and Grus II are on
a prograde orbit with similar orbital properties, although the large
uncertainties on the dynamical properties render an unambiguous claim
of connection difficult. At the same time, the chemical analysis
strongly weakens the connection between both. We argue that Grus II in
combination with the Orphan stream would have to exhibit a strong
inverse metallicity gradient, which to date has not been detected in
any Local Group system.
Description:
In our investigation, we identified 20 RR Lyrae variables (13 RRab and
7 RRc-type pulsators) to be associated with the Orphan stream based on
their equatorial coordinates, proper motions, and distances, listed in
table D1.
We recovered 54 nonvariable stars likely associated with the Orphan
stream as traced by our sample of RR Lyrae variables (listed in
Table D.2).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tabled1.dat 240 20 RR Lyrae stars in Orphan stream
tabled2.dat 212 54 Non variable stars in Orphan stream
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See also:
I/350 : Gaia Early Data Release 3 (Gaia EDR3) (Lindegren+ 2020)
V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
J/AJ/136/2050 : SEGUE stellar parameter pipeline. II. (Lee+, 2008)
J/AJ/153/204 : RR Lyrae stars from the PS1 3π survey (Sesar+, 2017)
J/ApJ/765/154 : RR Lyrae stars in the Catalina Sky Survey (Drake+, 2013)
Byte-by-byte Description of file: tabled1.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- ObjID SDSS source ID
20 A1 --- n_ObjID [*] * for star not used as reference sample
in Sect. 4.2
22- 40 I19 --- GaiaEDR3 Gaia EDR3 source ID
42- 59 F18.14 deg RAdeg Right ascension (J2000)
61- 78 F18.15 deg DEdeg Declination (J2000)
80- 97 F18.12 pc d Distance
99-116 F18.13 pc e_d Uncertainty on distance
118-135 F18.14 km/s Vsys Systemic velocity
137-155 F19.16 km/s e_Vsys Uncertainty on systemic velocity
157-165 F9.6 mag VCSS Mean V band magnitude (Catalina photometry)
167-174 F8.6 mag e_VCSS Uncertainty on mean V band magnitude
176-183 F8.6 d P Pulsation period
185-196 F12.6 d M0 Time of brightness maxima
198-205 F8.6 mag AmpVCSS Pulsation amplitude (Catalina photometry)
207-210 A4 --- Type Pulsation RR Lyrae type
212-216 F5.2 [-] [Fe/H] Metallicity
218-236 F19.17 --- P(A/B) The conditional prob. of membership
238-240 A3 --- Note [K19 -] Known from Koposov et al.
(2019MNRAS.485.4726K 2019MNRAS.485.4726K)
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Byte-by-byte Description of file: tabled2.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- ObjID SDSS source ID
21- 39 I19 --- GaiaEDR3 Gaia EDR3 source ID
41- 58 F18.14 deg RAdeg Right ascension (J2000)
60- 77 F18.15 deg DEdeg Declination (J2000)
79- 88 F10.6 km/s RV Adopted radial velocity
90- 99 F10.7 km/s e_RV Uncertainty on adopted radial velocity
101-109 F9.6 mag gmag g-band magnitude
111-125 F15.9 mag e_gmag ?=-9999 Uncertainty on g-band magnitude
127-135 F9.4 K Teff Adopted Effective temperature
137-146 F10.6 K e_Teff Uncertainty on adopted effective temperature
148-157 F10.7 --- [Fe/H] Adopted Metallicity
159-169 F11.9 --- e_[Fe/H] Uncertainty on adopted metallicity
171-180 F10.8 --- logg Adopted Surface gravity
182-192 F11.9 --- e_logg Uncertainty on adopted surface gravity
194-212 F19.17 --- P(A/B) The conditional probability of membership
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Acknowledgements:
Zdenek Prudil, prudilz(at)ari.uni-heidelberg.de
(End) Zdenek Prudil [ARI, Germany], Patricia Vannier [CDS] 21-Apr-2021