Confrontation of MOND with the rotation curves of early-type disc galaxies

We extend the MOND analysis to a sample of 17 high surface brightness, early-type disc galaxies with rotation curves derived from a combination of 21cm HI line observations and optical spectroscopic data. A number of these galaxies have asymptotic rotation velocities between 250 and 350 km/s making them among the most massive systems (in terms of baryonic mass) considered in the context of MOND. We find that the general MOND prediction for such galaxies -- a rotation curve which gradually declines to the asymptotic value -- is confirmed, and in most cases the MOND rotation curve, determined from the mean radial light and gas distribution, agrees in detail with the observed rotation curve. In the few cases where MOND appears not to work well, the discrepancies can generally be understood in terms of various observational errors -- such as incorrect orientation angles and/or distances -- or of unmodelled physical effects -- such as non-circular motions. The implied mass-to-light ratios for the stellar disc and bulge constrain the MOND interpolating function; the form recently suggested by Zhao & Famaey (2005) yields more sensible values than the one traditionally used in MOND determinations of galaxy rotation curves.Comment: 9 pages, 2 figures, submitted MNRA

Absolute absorption and fluorescence measurements over a dynamic range of 106^6 with cavity-enhanced laser-induced fluorescence

We describe a novel experimental setup that combines the advantages of both laser-induced fluorescence and cavity ring-down techniques. The simultaneous and correlated measurement of the ring-down and fluorescence signals yields absolute absorption coefficients for the fluorescence measurement. The combined measurement is conducted with the same sample in a single, pulsed laser beam. The fluorescence measurement extends the dynamic range of a stand-alone cavity ring-down setup from typically three to at least six orders of magnitude. The presence of the cavity improves the quality of the signal, in particular the signal-to-noise ratio. The methodology, dubbed cavity-enhanced laser-induced fluorescence (CELIF), is developed and rigorously tested against the spectroscopy of 1,4-bis(phenylethynyl)benzene in a molecular beam and density measurements in a cell. We outline how the method can be utilised to determine absolute quantities: absorption cross sections, sample densities and fluorescence quantum yields.Comment: 12 pages, 6 figures, submitted to J. Chem. Phy

Bars from the Inside Out: An HST Study of their Dusty Circumnuclear Regions

The results of bar-driven mass inflow are directly observable in high-resolution HST observations of their circumnuclear regions. These observations reveal a wealth of structures dominated by dust lanes, often with a spiral-like morphology, and recent star formation. Recent work has shown that some of these structures are correlated with the presence or absence of a bar. I extend this work with an investigation of circumnuclear morphology as a function of bar strength for a sample of 48 galaxies with both measured bar strengths and ``structure maps'' computed from HST images. The structure maps for these galaxies, which have projected spatial resolutions of 2 - 15 pc, show that the fraction of galaxies with grand-design (GD) circumnuclear dust spirals increases significantly with bar strength, while tightly wound dust spirals are only present in the most axisymmetric galaxies. GD structure is only found at the centers of galaxies classified as SB(s) or SB(rs) and not SB(r). SB(s) galaxies on average have stronger bars than SB(r) galaxies. There is also a modest increase in the fraction of loosely wound dust spirals at later morphological types, which may reflect an increase in the fraction of galaxies with circumnuclear, gaseous disks. (abridged)Comment: 10 pages, 6 figures. To appear in "Penetrating Bars through Masks of Cosmic Dust: The Hubble Tuning Fork strikes a New Note" held June 7-12th, 2004 in Pilanesberg National Park, South Africa. Version with higher resolution figures is available at http://cfa-www.harvard.edu/~pmartini/professional/publications/safrica04.pd

BOOMERanG Data Suggest a Purely Baryonic Universe

The amplitudes of peaks in the angular power spectrum of anisotropies in the microwave background radiation depend on the mass content of the universe. The second peak should be prominent when cold dark matter is dominant, but is depressed when baryons dominate. Recent microwave background data are consistent with a purely baryonic universe with Omega(matter) = Omega(baryon) ~ 0.03 and Omega(Lambda) ~ 1.Comment: 10 pages AASTeX with 1 color postscript figure. Accepted for publication in ApJ Letters. And yes, the prediction was in the literature before the dat

Oxygen Isotopic Constraints on the Number and Origin of Basaltic Achondrite Parent Bodies

Our data show that HED meteorites have a homogeneous oxygen isotopic composition consistent with a magma ocean on Vesta. Ibitira, Asuka 881394, Pasamonte, and NWA 1240 probably come from separate parent asteroids

Is dark matter an extra-dimensional effect?

We investigate the possibility that the observed behavior of test particles outside galaxies, which is usually explained by assuming the presence of dark matter, is the result of the dynamical evolution of particles in higher dimensional space-times. Hence, dark matter may be a direct consequence of the presence of an extra force, generated by the presence of extra-dimensions, which modifies the dynamic law of motion, but does not change the intrinsic properties of the particles, like, for example, the mass (inertia). We discuss in some detail several possible particular forms for the extra force, and the acceleration law of the particles is derived. Therefore, the constancy of the galactic rotation curves may be considered as an empirical evidence for the existence of the extra dimensions.Comment: 11 pages, no figures, accepted for publication in MPLA; references adde

Migrant and minority community organisations: funding, sustainability and ways forward

MODA (Migrant Organisations’ Development Agency) and Middlesex University have been working together on a research project about funding and resources available to migrant and minority organisations in London. This reports presents some of its key findings. The aim of the project was to gather information about the role of minority and migrant organisations, including details about the services they provide, the community needs they address, the financial and organizational challenges they face and the creative ways they are finding to cope. The research also aimed to explore the effects of the current economic and political climate on the sector and the role played by second tier organisations and other networks

Chandra Observations of ULIRGs: Extended Hot Gas Halos in Merging Galaxies

We study the properties of hot gaseous halos in 10 nearby ultraluminous IRAS galaxies observed with the ACIS instrument on board Chandra. For all sample galaxies, diffuse soft X-ray emissions are found within ~10 kpc of the central region; their spectra are well fitted by a MEKAL model plus emission lines from alpha-elements and other ions. The temperature of the hot gas is about 0.7 keV and metallicity is about 1 solar. Outside the central region, extended hot gaseous halos are found for nine out of the ten ULIRGs. Most spectra of these extended halos can be fitted with a MEKAL model with a temperature of about 0.6 keV and a low metallicity (~ 0.1 solar). We discuss the implications of our results on the origin of X-ray halos in elliptical galaxies and the feedback processes associated with starbursts.Comment: 31 pages, 6 figuers, ApJ in press, accepted versio