We consider the hypothesis that galactic dark matter is composed of ultralight scalar particles and use internal properties of dwarf spheroidal galaxies to establish a preferred range for the mass m φ of these bosonic particles. We re-investigate the problem of the longevity of the cold clump in Ursa Minor and the problem of the rapid orbital decay of the globular clusters in Fornax and dwarf ellipticals. Treating the scalar field halo as a rigid background gravitational potential and using N -body simulations, we have explored how the dissolution timescale of the cold clump in Ursa Minor depends on m φ . It is demonstrated that for masses in the range 0.3 × 10 −22 eV < m φ < 1 × 10 −22 eV, scalar field dark halos without self-interaction would have cores large enough to explain the longevity of the cold clump in Ursa Minor and the wide distribution of globular clusters in Fornax, but small enough to make the mass of the dark halos compatible with dynamical limits. It is encouraging to see that this interval of m φ is consistent with that needed to suppress the overproduction of substructure in galactic halos and is compatible with the acoustic peaks of cosmic microwave radiation. On the other hand, for self-interacting scalar fields with coupling constant λ, values of m 4 φ /λ 0.55 × 10 3 eV 4 are required to account for the properties of the dark halos of these dwarf spheroidal galaxies.

The well-established correlations between the mass of massive black holes (BHs) in the nuclei of most studied galaxies and various global properties of their hosting galaxy lend support to the idea that dwarf galaxies and globular clusters could also host a BH in their centers. Direct kinematic detection of BHs in dwarf spheroidal (dSph) galaxies are seriously hindered by the small number of stars inside the gravitational influence region of the BH. The aim of this Letter is to establish an upper dynamical limit on the mass of the putative BH in the Ursa Minor (UMi) dSph galaxy. We present direct N-body simulations of the tidal disruption of the dynamical fossil observed in UMi, with and without a massive BH. We find that the observed substructure is incompatible with the presence of a massive BH of (2 − 3) × 10 4 M ⊙ within the core of UMi. These limits are consistent with the extrapolation of the M BH − σ relation to the M BH < 10 6 M ⊙ regime. We also show that the BH may be off-center with respect to the center of symmetry of the whole galaxy.

We study archival HST [S ii] 6716+30 and Hα images of the HH 34 outflow, taken in 1998.71 and in 2007.83. The ∼9 yr time baseline and the high angular resolution of these observations allow us to carry out a detailed proper-motion study. We determine the proper motions of the substructure of the HH 34S bow shock (from the [S ii] and Hα frames) and of the aligned knots within ∼30 from the outflow source (only from the [S ii] frames). We find that the present-day motions of the knots along the HH 34 jet are approximately ballistic, and that these motions directly imply the formation of a major mass concentration in ∼900 yr, at a position similar to the one of the present-day HH 34S bow shock. In other words, we find that the knots along the HH 34 jet will merge to form a more massive structure, possibly resembling HH 34S.

The Bose-Einstein condensate/scalar field dark matter model, considers that the dark matter is composed by spinless-ultra-light particles which can be described by a scalar field. This model is an alternative model to the Λ-cold dark matter paradigm, and therefore should be studied at galactic and cosmological scales. Dwarf spheroidal galaxies have been very useful when studying any dark matter theory, because the dark matter dominates their dynamics. In this paper we study the Sextans dwarf spheroidal galaxy, embedded in a scalar field dark matter halo. We explore how the dissolution time-scale of the stellar substructures in Sextans, constrain the mass, and the self-interacting parameter of the scalar field dark matter boson. We find that for masses in the range (0.12 < m φ < 8) × 10 −22 eV, scalar field dark halos without self-interaction would have cores large enough to explain the longevity of the stellar substructures in Sextans, and small enough mass to be compatible with dynamical limits. If the self-interacting parameter is distinct to zero, then the mass of the boson could be as high as m φ ≈ 2 × 10 −21 eV, but it would correspond to an unrealistic low mass fot the Sextans dark matter halo . Therefore, the Sextans dwarf galaxy could be embedded in a scalar field/BEC dark matter halo with a preferred self-interacting parameter equal to zero.

We present a new IRAC, Spitzer IRAC images of the HH 34 outflow. These are the first images that detect both the knots along the southern jet and the northern counterjet (the counterjet knots were only detected previously in a long slit spectrum). This result removes the problem of the apparent coexistence of a large scale symmetry (at distances of up to ∼ 1 pc) and a complete lack of symmetry close to the source (at distances of ∼ 10 17 cm) for this outflow. We present a quantitative evaluation of the newly found symmetry between the HH 34 jet and counterjet, and show that the observed degree of symmetry implies that the jet production region has a characteristic size < 2.8 AU. This is the strongest constraint yet derived for the size of the region in which HH jets are produced. Subject headings: circumstellar matter -stars: formation -ISM: jets and outflows -infrared: ISM -Herbig-Haro objects -ISM: individual objects (HH34)