J/MNRAS/495/98 Tidal scars of the Small Magellanic Cloud (De Leo+, 2020)
Revealing the tidal scars of the Small Magellanic Cloud.
De Leo M., Carrera R., Noel N.E.D., Read J.I., Erkal D., Gallart C.
<Mon. Not. R. Astron. Soc., 495, 98-113 (2020)>
=2020MNRAS.495...98D 2020MNRAS.495...98D (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Stars, giant ; Positional data ;
Radial velocities ; Spectra, optical ; Infrared
Keywords: stars: kinematics and dynamics - galaxies: dwarf -
galaxies: individual: SMC - galaxies: interactions -
galaxies: kinematics and dynamics - Magellanic Clouds
Abstract:
Due to their close proximity, the Large and Small Magellanic Clouds
(LMC/SMC) provide natural laboratories for understanding how galaxies
form and evolve. With the goal of determining the structure and
dynamical state of the SMC, we present new spectroscopic data for
∼3000 SMC red giant branch stars observed using the AAOmega
spectrograph at the Anglo-Australian Telescope. We complement our data
with further spectroscopic measurements from previous studies that
used the same instrumental configuration as well as proper motions
from the Gaia Data Release 2 catalogue. Analysing the photometric and
stellar kinematic data, we find that the SMC centre of mass presents a
conspicuous offset from the velocity centre of its associated HI gas,
suggesting that the SMC gas is likely to be far from dynamical
equilibrium. Furthermore, we find evidence that the SMC is currently
undergoing tidal disruption by the LMC within 2kpc of the centre of
the SMC, and possibly all the way into the very core. This is revealed
by a net outward motion of stars from the SMC centre along the
direction towards the LMC and an apparent tangential anisotropy at all
radii. The latter is expected if the SMC is undergoing significant
tidal stripping, as we demonstrate using a suite of N-body simulations
of the SMC/LMC system disrupting around the Milky Way. Our results
suggest that dynamical models for the SMC that assume a steady state
will need to be revisited.
Description:
Our data is complementary to those from Dobbie et al.
(2014MNRAS.442.1663D 2014MNRAS.442.1663D, Cat. J/MNRAS/442/1663), who performed a similar
study but covered mainly the SMC body. We sampled regions between the
fields from Dobbie et al. (2014MNRAS.442.1663D 2014MNRAS.442.1663D, Cat. J/MNRAS/442/1663)
and went slightly further in some directions. The spectroscopic
targets were selected from the expected position of the upper RGB in
the colour-magnitude diagram (CMD) from the Two Micron All Sky Survey
(2MASS; Skrutskie et al. 2006AJ....131.1163S 2006AJ....131.1163S, Cat. VII/233).
The spectroscopic observations were secured on the nights of the 2011i
October 2 and 3, and 2014 November 10, 11, and 12 with the AAOmega
spectrograph (Saunders et al. 2004SPIE.5492..389S 2004SPIE.5492..389S) fed by the Two
Degree Field (2dF) multiobject system installed at the prime focus of
the Anglo-Australian Telescope located at Siding Spring Observatory
(Australia). The 2dF + AAOmega is a dual-beam spectrograph that allows
to allocate up to 400 2arcsec-size optical fibres within a 2°
field of view. In the red arm, we used the grating 1700D centred on
∼8500Å, providing a spectral resolution of R∼8500. For each field
we acquired three exposures of 3600s. In total, we obtained spectra
with a signal-to-noise ratio (SNR) per pixel larger than 5 for 2573
stars.
Table A1 reports the 1861 stars of our data set with radial velocity
determinations.
Objects:
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RA (ICRS) DE Designation(s)
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00 52 37.99 -72 48 01.0 NAME SMC = 1FGL J0101.3-7257 = NGC 292
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 57 1861 Observational data
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See also:
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
J/MNRAS/442/1663 : Velocities of red giants in the SMC (Dobbie+, 2014)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 21 A21 --- Name Star name (2MASSHHMMSSss+DDMMSSs)
23- 30 F8.5 deg RAdeg Right ascension (J2000)
32- 40 F9.5 deg DEdeg Declination (J2000)
42- 47 F6.2 km/s RV Radial velocity
49- 52 F4.2 km/s e_RV Error on RV
54- 57 F4.1 --- SNR Signal to noise ratio
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 06-Jun-2023