We present three new clusters discovered in the halo of M31 which, although having globular-like colours and luminosities,have an unusually large half-light radii, ~30 pc. They lie at projected galactocentric distances of approx. 15 to 35 kpc. These objects begin to fill the gap in parameter space between globular clusters and dwarf spheroidals, and are unlike any clusters found in the Milky Way, or elsewhere to date. Basic photometric and derived King profile fit parameters are given, and we discuss possible origins and their relationships to other populations.Comment: Revised according to referee comments. Accpeted by MNRA

An origin is sought for the ubiquity of cusps, both in computer simulations of halo formation in hierarchical clustering cosmogonies and in observations of galactic nuclei by the Hubble Space Telescope (HST). The encounters of merging clumps that built the galaxies can be described by the collisional Boltzmann equation. Using insights gained by studying the simpler Fokker-Planck equation, we show that there is a steady-state, self-consistent, cusped solution of the collisional Boltzmann equation corresponding to $\rho \sim r^{-4/3}$. This equilibrium is both stable and an attractor. It is the natural end-point of the diffusive encounters of an ensemble of equal mass clumps. The introduction of a mass spectrum weakens the mass density cusp. The spike in the luminosity density can be accentuated or softened, depending on the form of the mass-luminosity relation. Possible applications to the cusped nuclei of early-type galaxies are discussed.Comment: Latex, 14 pages, Needs aasms4.sty. The Astrophysical Journal (Letters), in pres

We have undertaken an HST Space Telescope Imaging Spectrograph survey of 54 late type spiral galaxies to study the scaling relations between black holes and their host spheroids at the low mass end. Our aim is to measure black hole masses or to set upper limits for a sizeable sample of spiral galaxies. In this paper we present new Space Telescope Imaging Spectrograph (STIS) observations of three spiral galaxies, NGC 4303, NGC 3310 and NGC 4258. The bright optical emission lines Hα λ 6564 Å, [NII] λλ 6549, 6585 Å and [SII] λλ 6718, 6732 Å were used to study the kinematics of the ionized gas in the nuclear region of each galaxy with a ∼0.07 spatial resolution. Our STIS data for NGC 4258 were analyzed in conjunction with archival ones to compare the gas kinematical estimate of the black hole mass with the accurate value from H 2 O-maser observations. In NGC 3310, the observed gas kinematics is well matched by a circularly rotating disk model but we are only able to set an upper limit to the BH mass which, taking into account the allowed disk inclinations, varies in the range 5.0 × 10 6 -4.2 × 10 7 M at the 95% confidence level. In NGC 4303 the kinematical data require the presence of a BH with mass M BH = (5.0)6 M (for a disk inclination i = 70 deg) but the weak agreement between data and disk model does not allow us to consider this measurement completely reliable. If the allowed inclination values are taken into account, M BH varies in the range 6.0 × 10 5 -1.6 × 10 7 M at the 95% confidence level. In NGC 4258, the observed kinematics require the presence of a black hole with M BH = (7.9) +6.2 −3.5 × 10 7 M (i = 60 deg) and, taking into account reasonable limits for the inclination, M BH is in the range 2.5× 10 7 -2.6× 10 8 M at the 95% confidence level. This result is in good agreement with the published value (3.9 ± 0.1) × 10 7 M , derived from H 2 O-maser observations. As in the case of NGC 4303, the agreement between observed and model kinematics is not strong but this does not affect the recovery of the correct M BH value. Our attempt at measuring BH masses in these 3 late type Sbc spiral galaxies has shown that these measurements are very challenging and at the limit of the highest spatial resolution currently available. Nonetheless our estimates are in good agreement with the scaling relations between black holes and their host spheroids suggesting that (i) they are reliable and (ii) black holes in spiral galaxies follow the same scaling relations as those in more massive early-type galaxies. A crucial test for the gas kinematical method, the correct recovery of the known BH mass in NGC 4258, has been successful.

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Context. Methanol masers at 6.7 GHz are recognised markers of high-mass star formation regions. The study of their distribution in the Galaxy gives important insights into the star formation activity of the Milky Way. We present a statistical analysis on the General Catalogue of 6.7 GHz methanol masers in the Galaxy with the aim of extracting global properties of the masers. Aims. We provide constraints on the luminosity function of 6.7 GHz methanol masers and on their total number in the Galaxy. Methods. We model the spatial distribution of the masers in the Milky Way by using their distribution in galactocentric distance which is unambiguous once a rotation curve for the Galaxy is assumed. This is the starting point for determining the luminosity function of the masers.Results. The luminosity function of 6.7 GHz methanol masers is modelled as a power-law with sharp cutoffs and having an index lying between −1.5 and −2. We also predict the number of detections of methanol masers assuming different sensitivity limits in the observations.