Radial Velocities of Stars in the Galactic Center

We present results from K band slit scan observations of a ~20''x20'' region of the Galactic center (GC) in two separate epochs more than five years apart. The high resolution (R>=14,000) observations allow the most accurate radial velocity and acceleration measurements of the stars in the central parsec of the Galaxy. Detected stars can be divided into three groups based on the CO absorption band heads at ~2.2935 microns and the He I lines at ~2.0581 microns and ~2.112, 2.113 microns: cool, narrow-line hot and broad-line hot. The radial velocities of the cool, late-type stars have approximately a symmetrical distribution with its center at ~-7.8(+/-10.3) km/s and a standard deviation ~113.7(+/-10.3) km/s. Although our statistics are dominated by the brightest stars, we estimate a central black hole mass of 3.9(+/-1.1) million solar masses, consistent with current estimates from complete orbits of individual stars. Our surface density profile and the velocity dispersion of the late type stars support the existence of a low density region at the Galactic center suggested by earlier observations. Many hot, early-type stars show radial velocity changes higher than maximum values allowed by pure circular orbital motions around a central massive object, suggesting that the motions of these stars greatly deviate from circular orbital motions around the Galactic center. The correlation between the radial velocities of the early type He I stars and their declination offsets from Sagittarius A* suggests that a systematic rotation is present for the early-type population. No figure rotation around the Galactic center for the late type stars is supported by the new observations.Comment: 61 pages, 18 figures, 7 tables; accepted for publication in Astrophysical Journa

Peering through the veil: near-infrared photometry and extinction for the Galactic nuclear star cluster

The aims of this work are to provide accurate photometry in multiple near-infrared broadband filters, to determine the power-law index of the extinction-law toward the central parsec of the Galaxy, to provide measurements of the absolute extinction toward the Galactic center, and finally to measure the spatial variability of extinction on arcsecond scales.We use adaptive optics observations of the central parsec of the Milky Way. Absolute values for the extinction in the H, Ks, and L'-bands as well as of the power-law indices of the H to Ks and Ks to L' extinction-laws are measured based on the well-known properties of red clump stars. Extinction maps are derived based on H-Ks and Ks-L' colors. We present Ks-band photometry for ~7700 stars (H and L' photometry for a subset). From a number of recently published values we compute a mean distance of the Galactic center of R_0=8.03+-0.15 kpc, which has an uncertainty of just 2%. Based on this R_0 and on the RC method, we derive absolute mean extinction values toward the central parsec of the Galaxy of A_H=4.48+-0.13 mag, A_Ks=2.54+-0.12$ mag, and A_L'=1.27+-0.18 mag. We estimate values of the power-law indices of the extinction-law of alpha_{H-Ks}=2.21+-0.24 and alpha_{Ks-L'}=1.34+-0.29. A Ks-band extinction map for the Galactic center is computed based on this extinction law and on stellar H-Ks colors. Mean extinction values in a circular region with 0.5" radius centered on Sagittarius A* are A_{H, SgrA*}=4.35+-0.12, A_{Ks, SgrA*}=2.46+-0.03, and A_{L', SgrA*}=1.23+-0.08.Comment: accepted for publication by Astronomy & Astrophysics; please contact RS for higher quality figure

My Mother\u27s High Heel Shoes

pages 112-11

A Second Luminous Blue Variable in the Quintuplet Cluster

H and K band moderate resolution and 4 $\mu$m high resolution spectra have been obtained for FMM#362, a bright star in the Quintuplet Cluster near the Galactic Center. The spectral features in these bands closely match those of the Pistol Star, a luminous blue variable and one of the most luminous stars known. The new spectra and previously-obtained photometry imply a very high luminosity for FMM#362, L $\geq 10^6$ \Lsun, and a temperature of 10,000 - 13,000 K. Based on its luminosity, temperature, photometric variability, and similarities to the Pistol Star, we conclude that FMM#362 is a luminous blue variable.Comment: Accepted for publication in The Astrophysical Journal Letters, 4 PostScript figures, 2 table

San Francisco

pages 110-11

Arquitectura y danza

La danza es una disciplina que no construye formas que duren en el tiempo, ya que únicamente existen durante el momento de su representación. Por lo tanto está ligada al tiempo, ya que sólo existe mientras se representa y está claramente ligada al ritmo y al movimiento de los bailarines en el espacio escenográfico. El estudio de esos movimiento y la modificación temporal del espacio que los acoge es el objetivo principal de esta reflexión, donde la arquitectura es en este caso, el espacio escenográfico que se ve claramente alterado por el devenir de los bailarines al compas de la melodía.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

The role of the cadherin fmi-1/flamingo in the development of the D-type GABAergic neurons

Cadherin proteins are cell adhesion molecules involved in multiple aspects of the development of the nervous system. A subgroup of these proteins, called protocadherin, has been recently shown to play key roles during the formation of neuronal networks in various animal models. In the model nematode Caenorhabditis elegans, there is only one protocadherin protein, called fmi-1, which has not being fully characterized. Here, I describe the cellular and molecular characterization of the cadherin fmi-1/flamingo in the development of the D-type GABAergic neurons. Mutant alleles for fmi-1 were originally isolated during a genetic screen looking for genes that regulate synaptic morphology in the D-type GABAergic neurons, which are comprised of DD and VD neurons. In fact, fmi-1 animals display synaptic defects, which include reduced synapse number and aberrant synapse size and morphology, as well as an abnormal accumulation of synaptic vesicles at non-synaptic regions. Electron microscopy data reinforce these observations. Although synaptic defects were present in both the ventral nerve cord (VNC) and the dorsal nerve cord (DNC), it appears that synapses corresponding to the VD neurons are primary affected by fmi-1 mutations. Furthermore, transcriptional analysis suggests that fmi-1 is not present in the VD neurons. In fact, expression of fmi-1 under a promoter that is not active in the VD neurons was able to partially rescue these defects. Therefore, in this cellular context, fmi-1 might be acting cell non-autonomously. Mutations in fmi-1 also cause neurite growth defects in the VD neurons along the anteroposterior (A/P) axis. I have developed a VD-specific marker to visualize and score these defects. VD neurons in fmi-1 animals display two different types of neurite defects. First, an anterior ventral neurite (AVN), which will become the axon, fails to extend fully in the VNC. Second, VD neurons display a posterior ventral neurite (PVN) instead of a normal anterior neurite, which causes commissure patterning defects along the anteroposterior axis (A/P axis). These defects arose during the early development of the VD neurons and they appear not to be caused by defects in cell division or cell fate specification. Fly and vertebrate homologues of fmi-1 can work as part of the planar cell polarity (PCP) pathway. We found that mutations in two core components of the PCP pathway, vang -1 and prkl-1, do not display fmi-1-like defects in the VD neurons. Therefore, fmi-1 might be working independently from the PCP pathway to regulate directional neurite growth in these neurons. Finally, I also describe genetic interactions between fmi-1 and two components of the Wnt pathway, lin-17/frizzled and dsh-1/disheveled. Epistasis analyses suggest that lin-17 and dsh-1 work in a pathway distinct from that of fmi-1 to regulate directional neurite growth in the VD neurons along the A/P axis. In summary, fmi-1 plays multiple roles during the development of the D-type GABAergic neurons. Interestingly, fmi-1 and the Wnt pathway work redundantly to regulate VD neurite growth along the A/P axis in the VNC in C. elegans