J/A+A/623/A129 New satellites of the LMC search (Fritz+, 2019)
Gaia DR2 and VLT/FLAMES search for new satellites of the LMC.
Fritz T.K., Carrera R., Battaglia G., Taibi S.
<Astron. Astrophys. 623, A129 (2019)>
=2019A&A...623A.129F 2019A&A...623A.129F (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Abundances, [Fe/H] ; Proper motions ;
Radial velocities; Spectroscopy
Keywords: proper motions - stars: abundances - galaxies: dwarf -
galaxies: kinematics and dynamics
Abstract:
A wealth of tiny galactic systems populates the surroundings of the
Milky Way. However, some of these objects might have originated as
former satellites of the Magellanic Clouds, in particular of the Large
Magellanic Cloud (LMC). Examples of the importance of understanding
how many systems are genuine satellites of the Milky Way or the LMC
are the implications that the number and luminosity-mass function of
satellites around hosts of different mass have for dark matter
theories and the treatment of baryonic physics in simulations of
structure formation. Here we aim at deriving the bulk motions and
estimates of the internal velocity dispersion and metallicity
properties in four recently discovered distant southern dwarf galaxy
candidates, Columba I, Reticulum III, Phoenix II, and Horologium II.
We combined Gaia DR2 astrometric measurements, photometry, and new
FLAMES/GIRAFFE intermediate-resolution spectroscopic data in the
region of the near-IR CaII triplet lines; this combination is
essential for finding potential member stars in these low-luminosity
systems. We find very likely member stars in all four satellites and
are able to determine (or place limits on) the bulk motions and
average internal properties of the systems. The systems are found to
be very metal poor, in agreement with dwarf galaxies and dwarf galaxy
candidates of similar luminosity. Of these four objects, we can only
firmly place Phoenix II in the category of dwarf galaxies because of
its resolved high velocity dispersion (9.5+6.8-4.4km/s) and
intrinsic metallicity spread (0.33dex). For Columba I we also measure
a clear metallicity spread. The orbital pole of Phoenix II is well
constrained and close to that of the LMC, suggesting a prior
association. The uncertainty on the orbital poles of the other systems
is currently very large, so that an association cannot be excluded,
except for Columba I. Using the numbers of potential former satellites
of the LMC identified here and in the literature, we obtain for the
LMC a dark matter mass of M200=1.9+1.3-0.9x1011M☉
Description:
The observations were carried out with FLAMES mounted at Very Large
Telescope (VLT) UT2, together with the GIRAFFE spectrograph and the
LR8 grating, which provides a resolution of ∼6500 in the region of
the near-infrared CaII triplet lines around 8500Å. The data consist
of 3x3000s exposures and one of 1980s for Phx II, 6x2775s for Col I,
3x2775s for Horo II, and 3x2775s for Ret III.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 104 264 Observed properties for potential member stars
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- ID Target Identifier, based on 096.B-0785(A)
and 098.B-0419(A)
13- 21 F9.5 deg RAdeg Right Ascension (J2000)
23- 31 F9.5 deg DEdeg Declination (J2000)
33- 36 F4.2 --- R Radius in elliptical half light radii
38- 42 F5.2 mag gmag Extinction corrected magnitude in g band
44- 48 F5.2 mag imag Extinction corrected magnitude in i band
50- 53 F4.1 --- S/N Signal/Noise ratio per pixel
55- 59 F5.1 km/s Vlos Line-of-Sight velocity,
barycentric rest frame
61- 64 F4.1 km/s e_Vlos Uncertainty in Vlos
66- 70 F5.2 [Sun] [Fe/H] ?=- Metallicity
72- 75 F4.2 [Sun] e_[Fe/H] ?=- Uncertainty in [Fe/H]
77- 82 F6.2 mas/yr pmRA* ?=- Gaia DR2 proper motion in
Right Ascension (pmRA*cosDE)
84- 87 F4.2 mas/yr e_pmRA* ?=- Uncertainty in Gaia DR2 proper motion in
Right Ascension
89- 95 F7.2 mas/yr pmDE ?=- Gaia DR2 proper motion in Declination
97-100 F4.2 mas/yr e_pmDE ?=- Uncertainty in Gaia DR2 proper motion in
Declination
102-104 F3.1 --- Pmember Membership classification (1)
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Note (1): Membership classification as follows:
0.0 = non-member
0.5 = possible member
1.0 = very likely member
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Acknowledgements:
Tobias Fritz, tfritz(at)iac.es
(End) Patricia Vannier [CDS] 26-Feb-2019