The MEDIDO project: surprising result for Leo I Eva Noyola McDonald Observatory Majo Bustamante-Rosell, Karl Gebhardt (UT, Austin) Constraints on α Shape of dark matter haloes in dwarf galaxies The Astrophysical Journal Letters,775:L30(5pp),2013September20 Jardel & Gebhardt Given the freedom to choose a dark matter profile of any NGC 959 shape, it is immediately apparent that our models have chosen a variety of shapes for the dSphs. Draco appears the most similar to the NFW profile while Sculptor most closely resembles a broken power law that becomes shallower toward its center. The other galaxies host profiles that resemble neither cores nor cusps: Carina’s profile appears flat where we have kinematics but then displays a possible up-bending inside of this region. Sextans has asteeperslopethantheNFWprofileuntilitsoutermostpoint where it suddenly becomes flat. These sharp differences among dSph dark matter profiles demonstrate the variety of profile shapes in the Local Group. Unfortunately, due to a lack of central stellar velocities in the Walker et al. (2009a)data,thecentralprofilesofthedSphswe model become increasingly uncertain there. This is evidenced by the larger error bars on our gray points in Figure 1 where we have no kinematics coverage. However, we do have some constraint from projection effects and radial orbits in our models Figure 2. Combined dark matter density profiles of all the dSphs plotted on that have apocenters at radii where we do have data. the same axes. Each galaxy’s profile is plotted with the same colored points. Adams et al, 2013 Uncertainties on theseJardel points are& the Gebhardt,∆χ 2 1 uncertainties 2013 from Figure 1.We 4.1. Fornax plot the derived best-fit line with slope α = 1.2 0.5asadashedlineaswell as the NFW profile with α 1.0 as a red dashed= ± line. A fit excluding the points One galaxy must be strongly cuspy. One= other is Fornax• is an especially difficult case for non-parametric where we have no kinematics available is shown as a dotted line. The individual modelingmarginally because,Core/cusp compared consistent to theproblem: other dSphs, it iswithmeasure relatively being profilesthe have fullycentral been scaled cuspy. to ashape common height. Theof DM halos baryon-dominated. Our imprecise determination of M /L in (A color version of this figure is available in the online journal.) V Fornax causes ρ (r)tobegreaterthanthetotalmodeleddensity∗ remainder∗ seem to require modification away from NFW. at some radii, making ρ (r)negative.InouranalysisofFornax, 1 • MissingDM Satellite problem: measurethat are different accurate from the mean velocitiesr− profile. Our interpretation for we do not plot the radial range over which this occurs as it is of this observation is that variations in their individual formation unphysical.dwarf Instead, in Figuregalaxies1 we overplot and the stellar test density DM contenthistories cause for galaxies globular to scatter from theclusters average profile. Only in red to illustrate why the subtraction is difficult in Fornax. In when multiple galaxies are averaged together does it become all other panels, ρ (r) ρDM(r)andisnotplotted. clear they follow a combined r 1 profile. This single power- ∗ ≪ − There is strong evidence from multiple studies using indepen- law profile compares well with the predicted NFW profile in dent methods that suggests that Fornax has a dark matter profile the inner portion of the plot. However, at larger radii (>1kpc that is not cuspy like the NFW profile. (Goerdt et al. 2006; in dwarf galaxies) the NFW profile becomes steeper than∼ r 1 Walker & Penarrubia˜ 2011;Jardel&Gebhardt2012). Each of − (Springel et al. 2008). More data are needed at both large and these studies only contrasts between cored and cuspy profiles small radii to further explore this. or uses a single slope to characterize the profile. It is therefore interesting to explore the non-parametric result we obtain. Even K.G. acknowledges support from NSF-0908639. This work though we cannot determine ρDM where the stellar density is greater than the total density, we can still place an upper limit would not be possible without the state-of-the-art supercomput- ing facilities at the Texas Advanced Computing Center (TACC). on ρDM such that it must not be greater than ρ or the red band in Figure 1.Giventhisconstraint,wecanseethattheouterprofile∗ We also thank Matt Walker and the MMFS Survey team for of Fornax is flat, while the inner portion rises more steeply than making their radial velocities publicly available. 1 r− .PastdynamicalstudiesofFornaxonlycomparedgeneric cored and NFW profiles and did not test this up-bending profile, REFERENCES therefore it is difficult to compare to their results. Arraki, K. S., Klypin, A., More, S., & Trujillo-Gomez, S. 2012, arXiv:1212.6651 4.2. A Common Halo? Blumenthal, G. R., Faber, S. M., Flores, R., & Primack, J. 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R., & Gebhardt, K. 2012, ApJ, 746, 89 4 MEDIDO (MEasuring Dynamics In Dwarf Objects) Sample a) UGC2245 c) UGC2245 SDSS i Unresolved dwarf galaxies M79 M79 b) DSS d) Science Figures a) UGC2245 c) UGC2245 SDSS i Resolved dwarf galaxies M79 M79 b) DSS d) Galactic globular clusters Figure 1: Finder charts and preliminary kinematic maps for the globular cluster M79 and the low surface brightness galaxy UGC2245 that we observed during the late December/early January run. In the left two panels the VIRUS-W footprint is represented by blue regions. The upper two panels on the right show the mean line of sight velocity and velocity dispersions that we derived for UGC2245. The lower panel shows the line of sight velocity. We propose similar observations for the other targets of this proposal. For the nearby dwarfs and dwarf spheroidals, the foucus is on the central region for the core/cusp problem and a more robust analysis for the total mass in regards to the missing satellite problem. For the globular clusters, the focus on the outer region for theConstraints presence of dark matter, on and hence α have multiple pointings. Central pointings will be added from the project Central Rotation and Velocity Dispersion of Milky Way Globular Clusters (PI: Rukdee). The Astrophysical Journal Letters,775:L30(5pp),2013September20 Jardel & Gebhardt Given the freedom to choose a dark matter profile of any NGC 959 shape, it is immediately apparent that our models have chosen a variety of shapes for the dSphs. Draco appears the most similar to the NFW profile while Sculptor most closely resembles a broken power law that becomes shallower toward its center. The other galaxies host profiles that resemble neither cores nor cusps: Carina’s profile appears flat where we have kinematics but then displays a possible up-bending inside of this region. Sextans has asteeperslopethantheNFWprofileuntilitsoutermostpoint where it suddenly becomes flat. These sharp differences among dSph dark matter profiles demonstrate the variety of profile shapes in the Local Group. Unfortunately, due to a lack of central stellar velocities in the Walker et al. (2009a)data,thecentralprofilesofthedSphswe model become increasingly uncertain there. This is evidenced by the larger error bars on our gray points in Figure 1 where we have no kinematics coverage. However, we do have some constraint from projection effects and radial orbits in our models Figure 2. Combined dark matter density profiles of all the dSphs plotted on that have apocenters at radii where we do have data. the same axes. Each galaxy’s profile is plotted with the same colored points. Figure 2: Results from previous studies showing thatUncertainties the data on these is points better are the ∆χ fit2 1 byuncertainties dark frommatter Figure 1.We cusps. LEFT) 4.1. Fornax plot the derived best-fit line with slope α = 1.2 0.5asadashedlineaswell Delta chi-square vs.One central galaxy density must slope be from strongly the sample cuspy.as the of NFW Adams profile withOneα et1.0 al.otheras a red (2013).