From light to mass: accessing the initial and present-day Galactic globular cluster mass functions

The initial and present-day mass functions (ICMF and PDMF, respectively) of the Galactic globular clusters (GCs) are constructed based on their observed luminosities, the stellar evolution and dynamical mass-loss processes, and the mass-to-light ratio (MLR). Under these conditions, a Schechter-like ICMF is evolved for approximately a Hubble time and converted into the luminosity function (LF), which requires finding the values of 5 free parameters: the mean GC age (\tA), the dissolution timescale of a 10^5 \ms cluster ($\tau_5$), the exponential truncation mass (\mc) and 2 MLR parametrising constants. This is achieved by minimising the residuals between the evolved and observed LFs, with the minimum residuals and realistic parameters obtained with MLRs that increase with luminosity (or mass). The optimum PMDFs indicate a total stellar mass of $\sim4\times10^7$ \ms\ still bound to GCs, representing $\sim15$ of the mass in clusters at the beginning of the gas-free evolution. The corresponding ICMFs resemble the scale-free MFs of young clusters and molecular clouds observed in the local Universe, while the PDMFs follow closely a lognormal distribution with a turnover at \mto\sim7\times10^4\,\ms. For most of the GC mass range, we find an MLR lower than usually adopted, which explains the somewhat low \mto. Our results confirm that the MLR increases with cluster mass (or luminosity), and suggest that GCs and young clusters share a common origin in terms of physical processes related to formation.Comment: Accepted by MNRA

FSR1767 - a new globular cluster in the Galaxy

The globular cluster (GC) nature of the recently catalogued candidate FSR 1767 is established in the present work. It results as the closest GC so far detected in the Galaxy. The nature of this object is investigated by means of 2MASS colour-magnitude diagrams (CMDs), the stellar radial density profile (RDP) and proper-motions (PM). The properties are consistent with an intermediate metallicity (\feh\approx-1.2) GC with a well-defined turnoff (TO), red-giant branch (RGB) and blue horizontal-branch (HB). The distance of FSR 1767 from the Sun is \ds\approx1.5 kpc, and it is located at the Galactocentric distance \rgc\approx5.7 kpc. With the space velocity components $(V,W)=(184\pm14,-43\pm14)\rm km s^{-1}$, FSR 1767 appears to be a Palomar-like GC with \mv\approx-4.7, that currently lies $\approx57$ pc below the Galactic plane. The RDP is well represented by a King profile with the core and tidal radii \rc=0.24\pm0.08 pc and \rt=3.1\pm1.0 pc, respectively, with a small half-light radius \rh=0.60\pm0.15 pc. The optical absorption is moderate for an infrared GC, $A_V=6.2\pm0.3$, which together with its central direction and enhanced contamination explains why it has so far been overlooked.Comment: 6 pages, 7 figures. MNRAS Letters, accepte

The Impact of Baryonic Cooling on Giant Arc Abundances

Using ray tracing for simple analytic profiles, we demonstrate that the lensing cross section for producing giant arcs has distinct contributions due to arcs formed through image distortion only, and arcs form from the merging of two or three images. We investigate the dependence of each of these contributions on halo ellipticity and on the slope of the density profile, and demonstrate that at fixed Einstein radius, the lensing cross section increases as the halo profile becomes steeper. We then compare simulations with and without baryonic cooling of the same cluster for a sample of six clusters, and demonstrate that cooling can increase the overall abundance of giant arcs by factors of a few. The net boost to the lensing probability for individual clusters is mass dependent, and can lower the effective low mass limit of lensing clusters. This last effect can potentially increase the number of lensing clusters by an extra 50%. While the magnitude of these effects may be overestimated due to the well known overcooling problem in simulations, it is evident that baryonic cooling has a non-negligible impact on the expected abundance of giant arcs, and hence cosmological constraints from giant arc abundances may be subject to large systematic errors.Comment: ApJ Submitte

Discovery of two embedded clusters with WISE in the high Galactic latitude cloud HRK 81.4-77.8

Molecular clouds at very high latitude ($b>60^{\circ}$) away from the Galactic plane are rare and in general are expected to be non-star-forming. However, we report the discovery of two embedded clusters (Camargo 438 and Camargo 439) within the high-latitude molecular cloud HRK 81.4-77.8 using WISE. Camargo 439 with Galactic coordinates $\ell=81.11^{\circ}$ and $b=-77.84^{\circ}$ is an $\sim2$ Myr embedded cluster (EC) located at a distance from the Sun of $d_{\odot}=5.09\pm0.47$ kpc. Adopting the distance of the Sun to the Galactic centre $R_{\odot}=7.2$ kpc we derive for Camargo 439 a Galactocentric distance of $R_{GC}=8.70\pm0.26$ kpc and a vertical distance from the plane of $-4.97\pm0.46$ kpc. Camargo 438 at $\ell=79.66^{\circ}$ and $b=-78.86^{\circ}$ presents similar values. The derived parameters for these two ECs put HRK 81.4-77.8 in the halo at a distance from the Galactic centre of $\sim8.7$ kpc and $\sim5.0$ kpc from the disc. Star clusters provide the only direct means to determine the high latitude molecular cloud distances. The present study shows that the molecular cloud HRK 81.4-77.8 is currently forming stars, apparently an unprecedented event detected so far among high latitude clouds. We carried out a preliminary orbit analysis. It shows that this ECs are the most distant known embedded clusters from the plane and both cloud and clusters are probably falling ballistically from the halo onto the Galactic disc, or performing a flyby.Comment: 7 pages, 7 figures, and 2 tables in MNRAS, 201

Cuantificación de los flujos de asistencia: un nuevo enfoque

(Disponible en idioma inglés únicamente) La discusión sobre la eficacia de la asistencia externa se ha intensificado en los últimos años, en la medida en que la asistencia ha venido experimentando cada vez más presiones presupuestarias en los países donantes. Independientemente de los méritos de los argumentos en contra, el problema de fondo surge de si las medidas de asistencia que se emplean convencionalmente, tales como la ODA, que agrupa las donaciones y los préstamos, reflejan con precisión los flujos de asistencia reales. En este trabajo se analizan las deficiencias metodológicas de las medidas convencionales de la asistencia y se propone un nuevo enfoque de valoración que cuantifique los flujos de asistencia oficial como la suma de las donaciones y los equivalentes de donaciones de los préstamos oficiales. Esta medición de la asistencia, conceptualmente superior, puede distanciarse considerablemente de los agregados convencionales y dar una idea muy distinta de las principales tendencias de la asistencia.

Measuring aid flows : a new approach

Debate about the effectiveness of foreign aid has intensified in recent years, as budgetary pressures on aid have increased in donor countries. Whatever the merits of opposing arguments, the question is: do conventional measures of aid (such as OECD's Net ODA), which lump together grants and loans, accurately reflect true aid flows? The authors analyze the methodological shortcomings of conventional measures of aid and propose a new approach, which measures official aid flows as the sum of grants and the grant-equivalents of official loans (in a new aggregate they call"Effective Development Assistance,"or EDA). They show how results using this conceptually superior measure may differ significantly from conventional aggregates, providing a quite different view on major aid trends. They implement their approach empirically using data on some 40,000 official loans from the World Bank's DRS database--virtually all of the official loans to 133 developing countries from 1975 to 1995. The numerical results underscore several points: 1) The conventional approach has led to systematic overestimates of the concessionality of official loans. This overestimate has increased significantly since the mid-1980s. Conventional methods show a rising trend; the new method shows the opposite. 2) Net ODA increasingly overstates the true aid content of official flows, although the divergence between the two approaches is somewhat muted by the rising relative importance of grants over loans in total official flows.Strategic Debt Management,Economic Adjustment and Lending,Banks&Banking Reform,Payment Systems&Infrastructure,Economic Theory&Research,Economic Adjustment and Lending,Banks&Banking Reform,Strategic Debt Management,Economic Theory&Research,Payment Systems&Infrastructure