The Mass-to-Light Ratios of the Draco and Ursa Minor Dwarf Spheroidal Galaxies. II. The Binary Population and its Effects on the Measured Velocity Dispersions of Dwarf Spheroidals

We have used the Hydra fiber positioner and the bench spectrograph on the KPNO 4 m telescope to measure radial velocities for giants in the Draco (Dra) and Ursa Minor (UMi) dwarf spheroidal galaxies. The measurement uncertainties are 1–10 km s−1 per observation, with the median uncertainty being 3.6 km s−1. To date, we have reduced the data from two of our three runs. In UMi these have yielded 150 velocities for 85 member giants; 52 stars have two or more measurements. In Dra we have 108 velocities for 84 member giants and 20 stars have two or more measurements. There is good agreement between the repeat observations and with the Olszewski, Aaronson, & Hill (1995) MMT echelle velocities.

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HI Distribution in Extreme Dwarf Irregulars and Dwarf Spheroidals

Highlights of Astronomy ◽

10.1017/s1539299600020177 ◽

1998 ◽

Vol 11 (1) ◽

pp. 121-122

Author(s):

Claude Carignan

Keyword(s):

Star Formation ◽

Stellar Population ◽

Large Fraction ◽

Dwarf Spheroidal Galaxies ◽

Irregular Galaxies ◽

Single Burst ◽

Dwarf Spheroidals ◽

Dwarf Irregular Galaxies ◽

Spheroidal Galaxies

Recent studies (Puche & Westpfahl 1994, Young & Lo 1996) have shown that the distribution of HI in some extreme low luminosity dwarf irregular galaxies (e.g. M81dwA, Holmberg I, Leo A) tends to have a ring-like (or shell-like) distribution which suggests that a single burst of star formation could expell most of the remaining ISM (or at least a large fraction of it) from the system. In view of this, Puche & Westpfahl (1994) suggested that in dwarf spheroidal galaxies, the HI should be found at large radii since no young stellar population is observed in most of them.

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Evidence for Light-weight Local Group Dwarf Spheroidal Galaxies

Symposium - International Astronomical Union ◽

10.1017/s0074180900183652 ◽

2004 ◽

Vol 220 ◽

pp. 365-366

Author(s):

J. R. Kuhn ◽

D. Kocevski

Keyword(s):

Dark Matter ◽

Milky Way ◽

Local Group ◽

Light Weight ◽

Natural Explanation ◽

Dwarf Spheroidal Galaxies ◽

Ursa Minor ◽

Matter Component ◽

Morphological State ◽

Spheroidal Galaxies

A simple and natural explanation for the dynamics and morphology of the Local Group Dwarf Spheroidal galaxies, Draco (Dra) and Ursa Minor (UMi), is that they are weakly unbound stellar systems with no significant dark matter component. A gentle, but persistent, Milky Way (MW) tide has left them in their current kinematic and morphological state (the “parametric tidal excitation”). A new test of a dark matter dominated dS potential follows from a careful observation of the “clumpiness” of the dS stellar surface density.

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Too big to fail in light of Gaia

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2511 ◽

2019 ◽

Vol 490 (1) ◽

pp. 231-242 ◽

Cited By ~ 12

Author(s):

Manoj Kaplinghat ◽

Mauro Valli ◽

Hai-Bo Yu

Keyword(s):

Dark Matter ◽

Milky Way ◽

Large Scatter ◽

Too Big To Fail ◽

Dwarf Spheroidal Galaxies ◽

Ursa Minor ◽

Spheroidal Galaxies

ABSTRACT We point out an anticorrelation between the central dark matter (DM) densities of the bright Milky Way dwarf spheroidal galaxies (dSphs) and their orbital pericenter distances inferred from Gaia data. The dSphs that have not come close to the Milky Way centre (like Fornax, Carina and Sextans) are less dense in DM than those that have come closer (like Draco and Ursa Minor). The same anticorrelation cannot be inferred for the ultrafaint dSphs due to large scatter, while a trend that dSphs with more extended stellar distributions tend to have lower DM densities emerges with ultrafaints. We discuss how these inferences constrain proposed solutions to the Milky Way’s too-big-to-fail problem and provide new clues to decipher the nature of DM.

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