J/ApJ/921/32 Kinematics of Ant2 & Cra2 with S5 (DR2.2) & Gaia data (Ji+, 2021)
Kinematics of Antlia 2 and Crater 2 from the Southern Stellar Stream
Spectroscopic Survey (S5).
Ji A.P., Koposov S.E., Li T.S., Erkal D., Pace A.B., Simon J.D.,
Belokurov V., Cullinane L.R., Da Costa G.S., Kuehn K., Lewis G.F.,
Mackey D., Shipp N., Simpson J.D., Zucker D.B., Hansen T.T.,
Bland-Hawthorn J., The S5 Collaboration.
<Astrophys. J., 921, 32 (2021)>
=2021ApJ...921...32J 2021ApJ...921...32J
ADC_Keywords: Galaxies, spectra; Optical; Radial velocities; Proper motions;
Abundances, [Fe/H]; Photometry; Surveys; Galaxies, dwarf
Keywords: Dwarf galaxies ; Stellar kinematics ; Stellar streams ;
Milky Way Galaxy ; Large Magellanic Cloud ; Dark matter
Abstract:
We present new spectroscopic observations of the diffuse Milky Way
satellite galaxies Antlia 2 and Crater 2, taken as part of the
Southern Stellar Stream Spectroscopic Survey (S5). The new
observations approximately double the number of confirmed member stars
in each galaxy and more than double the spatial extent of
spectroscopic observations in Antlia 2. A full kinematic analysis,
including Gaia EDR3 proper motions, detects a clear velocity gradient
in Antlia 2 and a tentative velocity gradient in Crater 2. The
velocity gradient magnitudes and directions are consistent with
particle stream simulations of tidal disruption. Furthermore, the
orbit and kinematics of Antlia 2 require a model that includes the
reflex motion of the Milky Way induced by the Large Magellanic Cloud.
We also find that Antlia 2's metallicity was previously overestimated,
so it lies on the empirical luminosity-metallicity relation and is
likely only now experiencing substantial stellar mass loss. Current
dynamical models of Antlia 2 require it to have lost over 90% of its
stars to tides, in tension with the low stellar mass loss implied by
the updated metallicity. Overall, the new kinematic measurements
support a tidal disruption scenario for the origin of these large and
extended dwarf spheroidal galaxies.
Description:
Both Ant2 and Cra2 were observed as part of the Southern Stellar
Stream Spectroscopy Survey (S5). S5 uses the AAOmega spectrograph
on the 3.9m Anglo-Australian Telescope (AAT), fed by the 2dF fiber
positioner facility; see Li+ (2019, J/MNRAS/490/3508) for details on
the survey strategy, target selection, observation, and reduction of
S5 data.
Ant2 was observed with five AAT pointings between 2020 February 27 and
March 1. Each field was observed with three 40-minute exposures.
For Cra2, only one AAT field centered at Cra2 was observed. We
obtained two 2250s exposures on February 29 and two 2700s exposures on
March 1 for Cra2, with identical target lists and fiber allocations
for both nights.
Objects:
--------------------------------------------------------------
RA (ICRS) DE Designation(s)
--------------------------------------------------------------
09 35 32.83 -36 46 02.2 Ant2 = NAME Antlia 2 Dwarf Galaxy
11 49 14.40 -18 24 46.8 Cra2 = NAME Crater 2 Dwarf Galaxy
--------------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table4.dat 107 508 Antlia 2 data
table5.dat 107 207 Crater 2 data
--------------------------------------------------------------------------------
See also:
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
III/284 : APOGEE-2 data from DR16 (Johnsson+, 2020)
J/A+A/538/A100 : Abundances red giants in Carina dSph (Lemasle+, 2012)
J/MNRAS/434/1681 : Extremely metal-poor stars CaII triplet (Carrera+, 2013)
J/ApJ/779/102 : Metallicities of RGB stars in dwarf gal. (Kirby+, 2013)
J/ApJ/833/167 : PAndAS view of Andromeda satellites. II. (Martin+, 2016)
J/ApJ/819/53 : Magellan/M2FS sp. of Tucana 2 & Grus 1 (Walker+, 2016)
J/A+A/616/A10 : 46 open clusters GaiaDR2 HR diag. (Gaia Col., 2018)
J/ApJ/857/104 : Low surface brightness gal. from HSC-SSP (Greco+, 2018)
J/AJ/156/257 : Sp. of RGB stars in Draco & Ursa Minor (Spencer+, 2018)
J/A+A/625/A76 : NGC1052-DF2 VLT/MUSE datacubes (Emsellem+, 2019)
J/ApJ/883/11 : Magellan/IMACS sp. of Crater II & Hercules (Fu+, 2019)
J/MNRAS/490/3508 : The Southern Stellar Stream Sp. Survey (S5) (Li+, 2019)
J/ApJ/875/77 : PMs of MW satellites with Gaia & DES (Pace+, 2019)
J/ApJ/885/3 : Membership in 12 stellar streams from DES (Shipp+, 2019)
J/MNRAS/488/2743 : Giant Gal. dwarf satellite in Gaia DR2 (Torrealba+, 2019)
J/MNRAS/491/3496 : Andromeda XIX member stars (Collins+, 2020)
J/AJ/160/181 : Abundances in red giants with Magellan (Ji+, 2020)
J/AJ/159/46 : Abundances of 416 stars in 5 dSphs of M31 (Kirby+, 2020)
J/A+A/640/A106 : MUSE MATLAS-2019 spectral datacube (Mueller+, 2020)
J/other/Nat/583.768 : 2050 red giants CaII EWs (Wan+, 2020)
J/ApJ/906/96 : Dwarfs gal. in DC Justice League Simu. (Applebaum+, 2021)
J/MNRAS/506/150 : The GALAH+ Survey DR3 (Buder+, 2021)
J/ApJ/911/149 : Sp. obs. in ATLAS and Aliqa Uma streams (Li+, 2021)
J/A+A/649/A3 : Gaia EDR3 photometric passbands (Riello+, 2021)
J/ApJS/252/18 : LSB galaxies from DES Y3 (Tanoglidis+, 2021)
http://s5collab.github.io/ : S5 home page
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- Gaia Gaia EDR3 Source ID
21- 29 F9.5 deg RAdeg [141.9/146] Right Ascension (ICRS) at
Epoch=2015.5
31- 39 F9.5 deg DEdeg [-38.8/-34.5] Declination (ICRS) at
Epoch=2015.5
41- 45 F5.2 mag Gmag [16.97/20.34] Gaia EDR3 G-band magnitude
47- 52 F6.3 mas/yr pmRA [-3.9/1.1] Gaia EDR3 Proper motion in Right
Ascension
54- 59 F6.3 mas/yr pmDE [-4.9/2.2] Gaia EDR3 Proper motion in
Declination
61- 67 F7.2 km/s HRV [-105/420] Heliocentric Radial Velocity
69- 72 F4.2 km/s e_HRV [0.7/10] Uncertainty in HRV
74- 78 F5.2 [-] [Fe/H]1 [-3.5/1] Metallicity, S5 data release (DR2.2)
80- 84 F5.2 [-] e_[Fe/H]1 [0.01/99] Uncertainty in [Fe/H]1
86- 90 F5.2 [-] [Fe/H]2 [-3.5/1.8] Metallicity, higher-resolution red
calcium triplet (CaT)
92- 95 F4.2 [-] e_[Fe/H]2 [0.1/5] Uncertainty in [Fe/H]2
97 A1 --- Bin [YN] Binary Flag
99- 102 F4.2 --- Mm [0/1] Membership probability
104- 107 F4.1 --- S/N [4/32.2] Spectra Signal to Noise
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
2- 20 I19 --- Gaia Gaia EDR3 Source ID
22- 30 F9.5 deg RAdeg [176.5/178.4] Right Ascension (ICRS) at
Epoch=2015.5
32- 40 F9.5 deg DEdeg [-19.5/-17.4] Declination (ICRS) at
Epoch=2015.5
42- 46 F5.2 mag Gmag [16.34/20.23] Gaia EDR3 G-band magnitude
48- 53 F6.3 mas/yr pmRA [-5.8/1.8] Gaia EDR3 Proper motion in Right
Ascension
55- 60 F6.3 mas/yr pmDE [-2.1/1.5] Gaia EDR3 Proper motion in
Declination
62- 67 F6.2 km/s HRV [-32/367] Heliocentric Radial Velocity
69- 72 F4.2 km/s e_HRV [0.8/10] Uncertainty in HRV
74- 78 F5.2 [-] [Fe/H]1 [-3.3/0.06] Metallicity, S5 data release
(DR2.2)
80- 84 F5.2 [-] e_[Fe/H]1 [0.03/99] Uncertainty in [Fe/H]1
86- 90 F5.2 [-] [Fe/H]2 [-4.5/0.6] Metallicity, higher-resolution red
calcium triplet (CaT)
92- 95 F4.2 [-] e_[Fe/H]2 [0.1/3] Uncertainty in [Fe/H]2
97 A1 --- Bin [YN] Binary Flag
99- 102 F4.2 --- Mm [0/1] Membership probability
104- 107 F4.1 --- S/N [3/26.4] Spectra Signal to Noise
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 03-Feb-2023