PoS(DSU 2012)013 http://pos.sissa.it/ (within the virial radius). ⊙ M 10 10 × 4 . and 5 ⊙ M 10 10 × 6 . ∗ [email protected] [email protected] [email protected] Speaker. The dwarf spheroidal (dSph) galaxiesknown. are though to IV be and the Leothe most Milky V Way. dark are Their matter distances two to dominated ultra-faint the objects short Milky dwarf Way difference spheroidal are in 154kpc galaxies and radial recently 175kpc distance found respectively.the The and around rather sky the led fact to that the theyMagellanic idea also Clouds. that have a we Our small might results projected see showpair distance a that to on new the be pair minimum bound of total gravitationally has darkComputing bound to matter the galaxies be mass mass - between required of like 1 for the dark the models matter are within within the the predicted standard range opticalconclude of that radius dark it of matter could 300pc content be possible for shows that satellites that the so our two faint. galaxies We constitute therefore a bound pair. ∗ Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. c ⃝ VIII International Workshop on the DarkJune Side 10-15, of 2012 the , Rio de Janeiro, Brazil Rory Smith Departamento de Astronomia, Universidad de Concepción,E-mail: Chile Michael Fellhauer Departamento de Astronomia, Universidad de Concepción,E-mail: Chile Matias Blaña Diaz Departamento de Astronomia, Universidad de Concepción,E-mail: Chile Dwarf Spheroidal Galaxies and Leo IV and : A bound pair? PoS(DSU 2012)013 20. , 8. In . 10 , 5 = c Matias Blaña Diaz 2 : This scenario is the same as the previous one except : We use only the measured radial velocities, which is the only . Already in the discovery paper of Leo V the authors speculate that the two dwarfs 1 − Only radial velocities Radial and tangential velocities To restrict the parameter spacethe we measured adopt absolute two magnitudes, mass-ratios the luminosity between ratio the between two Leo satellites. IV and Using Leo V is 1 We proposed two main scenarios for3.1) our models as follows: known component. In the DMH(Leo scenario, IV) we should also not require leave the that3.2) smaller the halo centre (Leo of V). the This bigger ensures halo a tight bound pair. We adopt scenarios where we modelbiting the each two other. galaxies We ignore as the twoare luminous dark too components matter low of haloes to the gravitationaly (DMH) galaxies, bound or- because the their pair, masses or to significantly affect their orbits. our simulations we adopt this ratioscenarios for the where masses the of ratio the is two 1, DM that haloes means as that well. both We haloes also use have the same mass. that here we addvelocities. to The magnitude the of galaxies them is aAll as tangential DM high as velocity halos the are component respectiveconcentrations radial assumed to of component. the to the haloes have in respective a a radial range usually NFW assumed profile for the and dSph galaxies for of each of the cases we vary the Many new faint dwarf spheroidal (dSph) galaxies have been discover around the 3 2 1 2. Method (MW) (e.g. Willman etare al., less luminous 2005; than Zucker star et clustersGeha, al., and 2007). their 2006; stars If and exhibit these high manytheir objects velocity more). are high dispersions in velocity (e.g. Many virial dispersion, Simon of equilibrium & (DM) and those then dominated this their dwarfs would luminous objects masses imply known doratios, that in not in these the the explain objects order universe. are ofthis hundreds the They paper (e.g. most we would focus Simon dark exhibit on & two matter highand Geha, of these mass-to-light 2007) Leo new or (M/L) V ultra-faint even dwarfs, (Belokurov thousends namely et Leo(Moretti for IV et al., some (Belokurov al., cases. 2008). et 2009; al., Simon In 2007) et TheirBoth al., properties galaxies 2010; are are Sand very et studied close al., to by 2010)et each and many al., other for 2010) authors: in Leo radial and V: distance for also (Walker et (22 in Leoabout al., kpc) projected 50 IV: (Moretti 2009a,b). distance km et s on al., the 2009; sky. De Their Jong relative radial velocity differs only by DSph Galaxies and Dark Matter: Leo IV and Leo V 1. Introduction could form a bound pairform similar a bound to object the the Magellanic twinfaint system Clouds. satellites. would Nevertheless, need De the a authors Jong lot claimed eta of that it al. simple DM, is much by-chance highly more (2010) alignment. unlikely than argued that They itgalaxies the that also is two at to seen rule satellites all in are out but similar the simple possibilityconclude density that that enhancements the they of two might a faint be stellar dwarfsinvestigate a stream the are ’tumbling by not hypothesis pair’. orbital of With arguments. a ourthe bound paper So minimal (see pair total they Blaña mass further. et the Using system al. needs, a 2012) in restricted we order N-body want to code form to a we tight search bound for pair. PoS(DSU 2012)013 ⊙ ] V that L 1 / M [ 250 ). These values 2 Matias Blaña Diaz − − 20). = ). 1 c and a range of 27 ), where they calculate the M/L-ratios ⊙ 2 ). Within the same radius, our models M ⊙ (Walker et al., 2009a) and we calculated 6 ] V . Similarly, for the M/L-ratios we have a ⊙ 10 ] L ⊙ V / × ). M L 5 6 M 1 / . [ M and in Tab. 10 3 [ 78 1 to 2 × = 230 58 ⊙ DM mass for the two faint satellites is shown. Just by + − 19 V . M L 5 75 / 7 (See more details for each galaxy in Tab. 10 = total . M and 6 × V L 7 ⊙ 5–3 . and / . ) the 2 M M ⊙ 5 = respectively. We did the same for Leo V within a radius of 67.4pc M . This distance difference would imply an error in the masses of just 10 6 V 1 ⊙ and ] L × 10 / V ⊙ L 92 × left panel M M . / ( 5 5 1 . 10 M 1 [ 10  × 4 344 1 5 . . . 9 2 1 and Fig. + − 3 − − = 1 . 3 M mass does not strongly depend on the concentration of the haloes nor in the mass-ratio be- = We determine the minimum mass ofcode the to cover system the to huge remain parameter bound space using (Tab. aFinally simple we integration verify the results with full N-body simulations (Tab. M I would like to thank Dr. Christiane Frigerio and the organizers of the Dark Side of the Uni- In Tab. 4 5 total 4. Acknowledgments verse 2012 for the logistics andI the economical also support thank that allowed Dr. methank to Michael to participate in the Fellhauer this Departamento and event. de to Astronomia de the la FONDECYT Universidad de founding Concepción, for Chile. the support. Finally I 10 per cent andchange it our would conclusion. not A it boundtions. alter pair the in inferred the restricted M/L-ratios caseSumming significantly. up, is we still Therefore conclude a it that bound the doesfact pair total within not in mass a the we reasonable infer full range for simula- ofa the values. bound system Therefore, pair, of it making the could them Leos be an to possible ultra-faint be that counterpart bound the of is two the in galaxies Magellanic form Clouds. the tween them. And it strongly varieswith depending only on radial the velocity velocity or or kineticand scenario energy M/L-ratios with they of radial have Leo (scenario IV and with tangential theof velocity). values measured 97pc We by ( compare Simon & the Geha masses 2007 within an optical radius are extremely high but encompassof the the predictions known for values dSph to the galaxiesallow faint that us magnitudes faint, to of exclude if the the an Leos models extrapolation isThe with used. comparison highly The between concentrated range the DM of haloes results observational ( tions of values of the the restricted distance and criterion, the butin full they the do N-body not eighth simulations change column gives the in devia- outcome Tab. of the simulations as it is shown 3. Results & Conclusion looking at our different casesThe we values are get very results high and which would differthese put by results them amongst do an the not order most infer DM of that dominated this magnitude objects scenario known. in is Still total impossible. mass. We may see in the left panel of Fig. DSph Galaxies and Dark Matter: Leo IV and Leo V In total our investigation produces twelve different solutions to the problem. give masses between 5 within a standard optical radius offor the 300 M/L-ratios pc. log Using the same radius, our simulations predict a range range of 33 with with our models a mass range of 2 for the M/L-ratios. Furthermore, welished by checked Wilkinson our et al. results (2006) against (shown the in Fig trend for dSph galaxies pub- PoS(DSU 2012)013 to c Mass-to- 2 for Leo V. . 5 − Right: in favour of 5 10 20 c 4a 5a 6a / Matias Blaña Diaz Scenario 6 Point masses (a) Point masses (b) rad. vel. equal mass rad. vel. equal mass rad. vel. equal mass rad. vel. mass ratio 1.8 rad. vel. mass ratio 1.8 rad. vel. mass ratio 1.8 8 for Leo IV and . 5 − 5 10 20 – – Ratio 0.935 1.284 rad. & tang. vel. equal mass 0.953 1.204 1.375 rad. & tang. vel. equal mass 0.965 1.194 1.450 rad. & tang. vel. equal mass 1.179 0.9930.956 rad. & tang. vel.0.968 mass rad. ratio & 1.8 tang. vel. mass rad. ratio & 1.8 tang. vel. mass ratio 1.8 4 5 20 respectively) with radial velocities only. The 9 = 10 10 10 10 10 10 10 10 10 10 10 10 10 c ] 10 10 10 10 10 10 10 10 10 10 10 10 10 10 ⊙ tot × × × × × × × × × × × × × × M M [ -band magnitudes of 18 5 and 89 20 98 66 40 09 71 80 47 39 14 42 81 ...... V 4 1 = c 10 20 ] versus concentration of the haloes. We plot 1 4 LeoV , tot kpc [ 39.98 1 56.91 4 39.55 1 41.76 1 57.80 4 40.29 2 42.18 1 59.50 4 55.2853.30 5 51.70 4 4 42.99 1 : We adopt vir r 5 1a 2a 3a Note 9 9 9 9 9 9 10 10 10 10 10 10 ] 10 10 10 10 10 10 10 10 10 10 10 10 LeoV ⊙ , × × × × × × × × × × × × M 3 [ DM 75 05 30 45 55 05 20) with radial and tangential velocities. For Leo V we plot the values of cases 1 and 10 20 40 93 73 58 ...... M = c 2 ] 0 (cases 0a,b; plotted as open and filled circle - blue online). Solid lines are the results using 5 and LeoIV = , kpc [ = c 56.91 2 47.42 6 57.80 2 48.11 7 41.76 8 59.50 2 49.00 7 42.18 8 67.2564.83 1 62.90 1 1 42.99 9 vir / c r 1 5 10 20 9 9 9 10 10 10 10 10 10 10 10 10 ] 10 10 10 10 10 10 10 10 10 10 10 10 LeoIV ⊙ ) 2.544 2.929 3.343 2.484 2.867 3.279 2.686 3.067 3.482 2.631 3.014 3.425 , × × × ) 2.710 3.092 3.499 2.740 3.122 3.534 2.853 3.232 3.641 2.886 3.270 3.688 × × × × × × × × × ⊙ M ⊙ [ DM 30 55 05 10 22 20 27 40 34 47 11 84 Minimum DM mass of the total system M /L . . . /L ...... M ⊙ ⊙ (M (M Left: 10 c c 10 Mass-to-light ratios within a radius of 300 pc. The first column gives the number of the case, the second is the adopted concentration of the haloes. Then we give the mass Case 3 20 1 2 10 1 45 56 10 3 20 3 2 1 5 1 6a 20 2 3a 20 8 5a 10 2 2a 10 8 4a 5 2 1a 5 9 0a — 0b — Case LeoV: Log LeoIV: Log 3a as well as 4 and 6a, respectively. We use these specific cases because they span the whole range of our results. light ratios within a radius ofIV, 300 the pc. filled The upside-down circles triangles are areopen dSph cases triangles Galaxies of 1a are the cases and Local 4a 3 Group and (concentrations as 6 reported ( by Wilkinson et al. (2006). For Leo the mass-ratio 1.8. Triangles are casesresults with of radial equal velocity mass only haloes. and tri-stars Squares with are additional tangential radial-velocity-only velocity. cases Dashed and lines crosses show the have additional tangential velocity. include the point-mass results at 1 Figure 1: Table 2: Table 1: of the DM halo and itscolumn virial shows radius the for “ratio” Leo by IV whichcolumn and the is Leo maximum a V. distance The short differs next explanation between column forratio the gives the 1.8 the full = cases total N-body the masses rad. simulation two in and vel. haloes DM the = have of two-body a only the code. fixed radial whole The mass system, velocity, last rad. ratio the of next & 1.8; tang. equal = mass radial = and the tangential two velocity haloes adopted; have the mass same mass. DSph Galaxies and Dark Matter: Leo IV and Leo V PoS(DSU 2012)013 Leo 2007, , 686, , 542, A61 ApJ A&A 2008, Matias Blaña Diaz A Universal Mass 643, L103 2012, , 710, 1664 A Deeper Look at Leo ApJ , 716, 446 ApJ The Enigmatic Pair of ApJ 2006, 2010, 2010, , 694, L114 High-resolution Spectroscopy of ApJ , 718, 530 ApJ , 704, 1274 2009 (a), 2010, ApJ 5 2009 (b), Leo IV and V – A possible pair? , 670, 313 ApJ The Kinematics of the Ultra-Faint Milky Way Satellites: Solving the Missing Leo V: A Companion of a Companion of the Milky Way Galaxy? Cats and Dogs, Hair and a Hero: A Quintet of New Milky Way Companions The Leo IV : Color-Magnitude Diagram and Pulsating A New Milky Way Dwarf Satellite in Canes Venatici 2007, , 699, L125 ApJ 2009, Probing the Dark Matter Content of Dwarf Spheroidal Galaxies with FLAMES , 654, 897 Profile for Dwarf Spheroidal Galaxies? Walker M.G., Mateo M., Olszewski E.W., Penarrubia J., Evans, N.W., Gilmore G. Zucker D.B., et al. Wilkinson M.I., Kleyna J.T., Gilmore G.F., EvansD.R. N.W., Koch A., Grebel E.K., Wyse2006, R.F.G., Msngr, Harbeck 124, 25 Walker M.G., Belokurov V., Evans N.W., Irwin M.J., Mateo M., Olszewski E.W., and Gilmore G. ApJ L83 Dwarf Galaxies Leo IV and Leo V: Coincidence or Common Origin? Stars Sand D.J., Seth A., Olszewski E.W.,IV: Willman Star B., Formation Zaritzky History D., and Kallivayalil Extended N. Structure Simon J.D., Geha M. Simon J.D.,Frebel A., McWiliam A., KirbyExtremely E.N., Metal-poor Thompson Stars I.B. in the Least Evolved Galaxies: Leo IV V: Spectroscopy of a Distant and Disturbed Satellite De Jong J.T.A., Martin N.F., Rix H.-W., Smith K.W., Jin S., Macciò A.V. Moretti M.I., et al. Satellite Problem Belokurov V. et al, Belokurov V., et al. Blaña M., Fellhauer M., Smith R. [7] [8] [9] [5] [6] [2] [3] [4] [1] [12] [10] [11] DSph Galaxies and Dark Matter: Leo IV and Leo V References