Figure 6 .
Images showing how candidate Tuc V appears in the discovery data ( left panel ) and in the Gemini data ( right panel ). Open circles show the position of foreground stars . The dense core region displayed in the discovery image dissolves into a series of low-density knots in the Gemini data , indicating that Tuc V may not be a coherent cluster . confirm an overdensity that matched the discovery detection . In Figure 6 , we can see how Tuc V looks in the discovery data ( left panel ) and with the deeper Gemini data ( right panel ). In the Gemini data , Tuc V dissolves into a series of low density knots rather than a coherent cluster as one would expect . So what is this intriguing object ?
Tuc V has a 3D spatial distance of only 13 kpc from the Small Magellanic Cloud ’ s ( SMC ) core . The SMC is also known to have an extended stellar halo with the SMC Northern Overdensity ( SMCNOD ) residing at 8 kpc from the SMC ’ s center . So at 13 kpc , Tuc V is plausibly within the stellar halo of the SMC . The best fit isochrone for Tuc V suggests an 11.8 Gyr stellar population with a metallicity of [ Fe / H ] = -2.09 dex . However , the agemetallicity degeneracy of isochrone fitting makes an SMCNOD-type stellar population with an age of 6 Gyr and [ Fe / H ] = -1.3 dex consistent with the data . Our GMOS-S results advance the picture that Tuc V is not a bound stellar system , but a disrupted star cluster , merging dwarf galaxy , or a stellar feature in the SMC halo .
As the in-depth analysis of DES 1 , Eri III , and Tuc V has demonstrated , by utilizing the outstanding imaging capabilities of Gemini Observatory , we are able to determine whether a newly detected ultra-faint stellar system belongs to the class of dwarf galaxies or star clusters . We will continue our study of these objects with Gemini , as each of them raises very interesting questions on how they formed and how they entered the Milky Way . Our Galaxy may harbor hundreds of satellite galaxies and clusters , most of which have yet to be discovered and explored . Finding and teasing apart their mysteries will drive this field forward into the future , helping us to better understand the substructure of our Galaxy ’ s halo .
Blair Conn , a former Gemini Assistant Scientist in Chile , is an ARC Postdoctoral Researcher at the Australian National University . He can be reached at :
blair . conn @ anu . edu . au
Helmut Jerjen is Deputy Associate Director of Education and Graduate Program Convenor at the Research School of Astronomy & Astrophysics , Australian National University . He can be reached at :
helmut . jerjen @ anu . edu . au
April 2018 GeminiFocus
7
Figure 6.
Images showing how
candidate Tuc V appears
in the discovery data (left
panel) and in the Gemini
data (right panel). Open
circles show the position
of foreground stars.
The dense core region
displayed in the discovery
image dissolves into a
series of low-density
knots in the Gemini data,
indicating that Tuc V may
not be a coherent cluster.
confirm an overdensity that matched the
discovery detection. In Figure 6, we can see
how Tuc V looks in the discovery data (left
panel) and with the deeper Gemini data
(right panel). In the Gemini data, Tuc V dis-
solves into a series of low density knots
rather than a coherent cluster as one would
expect. So what is this intriguing object?
Tuc V has a 3D spatial distance of only 13
kpc from the Small Magellanic Cloud’s (SMC)
core. The SMC is also known to have an ex-
tended stellar halo with the SMC Northern
Overdensity (SMCNOD) residing at 8 kpc
from the 4>( 26VFW"6B22GV2b0W6&ǒvFFR7FV"bFR42FR&W7BfB66&Rf"GV2b7VvvW7G2w"7FV"VFvFWFƖ2ЦGbfR"FWvWfW"FRvRЦWFƖ6GFVvVW&7b66&RfGFpW244BGR7FV"VFvFvRbbw"BfR2FW667FVBvFFRFFW"t22&RЧ7VG2Gf6RFR7GW&RFBGV2b2@&VB7FV"77FV'WBF7'WFVB7F 6W7FW"W&vrGv&bv"7FV fVGW&RFR426W'fF'vR&R&RFFWFW&֖RvWFW WvǒFWFV7FVBVG&fB7FV"77FVЦ&Vw2FFR672bGv&bvW2"7F 6W7FW'2vRv6FVRW"7GVGbFW6P&V7G2vFvV֖2V6bFV&6W0fW'FW&W7FrVW7F2rFWf&VBBrFWVFW&VBFR֖ƷvW"v&&"VG&VG2b6FVƗFPvW2B6W7FW'27Bbv6fPWBF&RF66fW&VBBW&VBfFpBFV6r'BFV"ח7FW&W2vG&fPF2fVBf'v&BFFRgWGW&RVrW0F&WGFW"VFW'7FBFR7V'7G'V7GW&RbW v( 2&"6f&W"vV֖767FB66VF[email protected]6R2$27FF7F&&W6V&6W"@FRW7G&ƖFVfW'6GR6&P&V6VBC&"6RVGRPVWBW&V2FWWG766FRF&V7F"`VGV6FBw&GVFR&w&6fV"@FR&W6V&666b7G&גb7G&2Ц72W7G&ƖFVfW'6GR6&P&V6VBCVWBW&VRVGRP2FRFWFǗ62bDU2W&@GV2b2FV7G&FVB'WFƗrFRWBЧ7FFrvr6&ƗFW2bvV֖"Ф&#vV֖f7W0p