On Collision Course: The Nature of the Binary Star Cluster NGC 2006 / SL 538

The LMC hosts a rich variety of star clusters seen in close projected proximity. Ages have been derived for few of them showing differences up to few million years, hinting at being binary star clusters. However, final confirmation needs to be done through spectroscopic analysis. Here we focus on the LMC cluster pair NGC2006-SL538 and aim to determine whether the star cluster pair is a bound entity (binary star cluster) or a chance alignment. Using the MIKE echelle spectrograph at LCO we have acquired integrated-light spectra for each cluster. We have measured radial velocities by two methods: a) direct line profile measurement yields v$_r=300.3\pm5\pm6$ km/s for NGC2006 and $v_r=310.2\pm4\pm6$ km/s for SL538. b) By comparing observed spectra with synthetic bootstrapped spectra yielding $v_r=311.0\pm0.6$ km/s for NGC2006 and $v_r=309.4\pm0.5$ km/s for SL538. Finally when spectra are directly compared, we find a ${\Delta}v=1.08\pm0.47$ km/s. Full-spectrum SED fits reveal that the stellar population ages lie in the range 13-21 Myr with a metallicity of Z=0.008. We find indications for differences in the chemical abundance patterns as revealed by the helium absorption lines between the two clusters. The dynamical analysis shows that the two clusters are likely to merge within the next $\sim$150 Myr. The NGC2006-SL538 cluster pair shows radial velocities, stellar population and dynamical parameters consistent with a gravitational bound entity. We conclude that this is a genuine binary cluster pair, and we propose that their differences in ages and stellar population chemistry is most likely due to variances in their chemical enrichment history within their environment. We suggest that their formation may have taken place in a loosely bound star-formation complex which saw initial fragmentation but then had its clusters become a gravitationally bound pair by tidal capture.Comment: Accepted for publication in Astronomy & Astrophysics. 15 pages, 10 figures in low resolutio

Remittances, Inequality and Poverty: Evidence from Rural Mexico

Economic research has produced conflicting findings on the distributional impacts of migrant remittances, and there has been little research on the effects of changes in remittances on poverty. This paper utilizes new data from the Mexico National Rural Household Survey, together with inequality and poverty decomposition techniques, to explore the impacts of remittances on rural inequality and poverty. Our findings suggest that remittances from international migrants become more equalizing (or less unequalizing), as well as more effective at reducing poverty, as the prevalence of migration increases.Labor and Human Capital,

Energy dependence of the quark masses and mixings

The one loop Renormalization Group Equations for the Yukawa couplings of quarks are solved. From the solution we find the explicit energy dependence on $t=\ln E/\mu$ of the evolution of the {\em down} quark masses $q=d,s,b$ from the grand unification scale down to the top quark mass $m_{t}$. These results together with the earlier published evolution of the {\em up} quark masses completes the pattern of the evolution of the quark masses. We also find the energy dependence of the absolute values of the Cabibbo-Kobayashi-Maskawa (CKM) matrix $|V_{ij}|$. The interesting property of the evolution of the CKM matrix and the ratios of the quark masses: $m_{u,c}/m_{t}$ and $m_{d,s}/m_{b}$ is that they all depend on $t$ through only one function of energy $h(t)$.Comment: Talk presented at the IX Mexican School on Particles and Fields, August 9-19, Metepec, Pue., Mexico. To be published in the AIP Conference Proceedings. 5 pages and 1 eps figure included in the tex