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Alamo-Martinez K.A.,National Autonomous University of Mexico | Alamo-Martinez K.A.,National Research Council Canada | Blakeslee J.P.,National Research Council Canada | Jee M.J.,University of California at Davis | And 8 more authors.
Astrophysical Journal | Year: 2013

We study the rich globular cluster (GC) system in the center of the massive cluster of galaxies Abell 1689 (z = 0.18), one of the most powerful gravitational lenses known. With 28 Hubble Space Telescope/Advanced Camera for Surveys orbits in the F814W bandpass, we reach a magnitude I 814 = 29 with ≳90% completeness and sample the brightest ∼5% of the GC system. Assuming the well-known Gaussian form of the GC luminosity function (GCLF), we estimate a total population of GCs within a projected radius of 400 kpc. As many as half of the GCs may comprise an intracluster component. Even with the sizable uncertainties, which mainly result from the uncertain GCLF parameters, this system is by far the largest GC population studied to date. The specific frequency SN is high, but not uncommon for central galaxies in massive clusters, rising from SN ≈ 5 near the center to ∼12 at large radii. Passive galaxy fading would increase SN by ∼20% at z = 0. We construct the radial mass profiles of the GCs, stars, intracluster gas, and lensing-derived total mass, and we compare the mass fractions as a function of radius. The estimated mass in GCs, = 3.9 × 1010 Mȯ, is comparable to ∼80% of the total stellar mass of the Milky Way. The shape of the GC mass profile appears intermediate between those of the stellar light and total cluster mass. Despite the extreme nature of this system, the ratios of the GC mass to the baryonic and total masses, and thus the GC formation efficiency, are typical of those in other rich clusters when comparing at the same physical radii. The GC formation efficiency is not constant, but varies with radius, in a manner that appears similar for different clusters; we speculate on the reasons for this similarity in profile. © 2013. The American Astronomical Society. All rights reserved..

Wang Q.,Peking University | Wang Q.,New York University | Peng E.W.,Peking University | Blakeslee J.P.,National Research Council Canada | And 7 more authors.
Astrophysical Journal | Year: 2013

We study the azimuthal distribution of globular clusters (GCs) in early-type galaxies and compare them to their host galaxies using data from the ACS Virgo Cluster Survey. We find that in host galaxies with visible elongation (ε > 0.2) and intermediate to high luminosities (Mz < -19), the GCs are preferentially aligned along the major axis of the stellar light. The red (metal-rich) GC subpopulations show strong alignment with the major axis of the host galaxy, which supports the notion that these GCs are associated with metal-rich field stars. The metal-rich GCs in lenticular galaxies show signs of being more strongly associated with disks rather than bulges. Surprisingly, we also find that the blue (metal-poor) GCs can also show the same correlation. If the metal-poor GCs are part of the early formation of the halo and built up through mergers, then our results support a picture where halo formation and merging occur anisotropically, and that the present-day major axis is an indicator of the preferred merging axis. © 2013. The American Astronomical Society. All rights reserved..

Miranda Jr. H.C.,Texas Southern University | Brooks D.M.,Houston Museum of Natural Science | Kennedy R.S.,Ma-Maria
Wilson Journal of Ornithology | Year: 2011

We constructed a phylogenetic hypothesis of the pattern of colonization of Philippine scops owls (Otus and Mimizuku). Two mitochondrial genes, ND2 and cytochrome b, were sequenced for 12 samples representing six Philippine endemic taxa: three endemic species, one of which has three endemic subspecies; and one endemic genus. Topology, branch length information, and sequence divergence were used to present the hypothesis for the pattern, direction, and sequence of island colonization events. Philippine scops owls are in two well-supported clades, consistent with at least two independent colonization routes. One route is represented by the montane clade of Otus sunia, O. longicornis, and O. mirus. The other clade is represented by three subspecies of the lowland O. megalotis. The basal position of Mimizuku gurneyi relative to the megalotis clade suggests early colonization of Mindanao. Branch lengths and sequence divergence data are congruent with the morphological differences among the megalotis races. The three races of megalotis differed in 15 of 16 morphological characters. Based on molecular and morphological evidence, we recognize the following Otus megalotis subspecies as full species: Luzon Lowland Scops Owl (O. megalotis), Mindanao Lowland Scops Owl (O. everetti), and Visayan Lowland Scops Owl (O. nigrorum). We also propose reassigning the Giant Scops Owl (Mimizuku gurneyi) to the genus Otus for phyletic consistency. © 2011 by the Wilson Ornithological Society.

Strelnitski V.,Ma-Maria | Bieging J.H.,University of Arizona | Hora J.,Harvard - Smithsonian Center for Astrophysics | Smith H.A.,Harvard - Smithsonian Center for Astrophysics | And 4 more authors.
Astrophysical Journal | Year: 2013

We report on a study of the ∼10′ (∼5 pc in projection) environs of the peculiar, high-luminosity emission-line star MWC 349A in the IR, radio, and visible domains. Besides the recently discovered X-shaped, arcmin-scale IR nebula centered on MWC 349A ("X nebula"), with the kinematic age of ∼104 yr, we identify several young objects pointing toward an ongoing process of active star formation in this region and estimate some physical parameters of the newly discovered objects. The radiation of the X nebula is due to a geometrically and optically thin dust front heated to Td ≈ 60-70 K by the radiation of the central star. The bipolar dust front probably results from the interaction of a powerful stellar wind with the circumstellar disk. One of the related objects is an elongated, cold molecular cloud, ∼1 pc in size, adjacent to MWC 349A in projection and having the same radial velocity (V LSR ≈ +9 km s-1). The proximity of the molecular cloud may indicate that MWC 349A was born locally rather than being a runaway object ejected from the core of Cyg OB2 several Myr ago. If it is still associated with its natal cloud, MWC 349A may be a rare example of the observable pre-main-sequence stage of a ∼30 M ⊙star. If the association with the molecular cloud is an effect of projection, however, MWC 349A may already be an evolved star, even if it was born locally. We discuss future observations that may shed more light on the evolutionary status of this unique object. © 2013. The American Astronomical Society. All rights reserved..

Rule E.,Johns Hopkins University | Loeb A.,Harvard - Smithsonian Center for Astrophysics | Strelnitski V.S.,Ma-Maria
Astrophysical Journal Letters | Year: 2013

We investigate the prospects of blind and targeted searches in the radio domain (10 MHz to 1 THz) for high-n hydrogen recombination lines from the first generation of galaxies, at z ≲ 10. The expected optically thin spontaneous α-line luminosities are calculated as a function of the absolute AB magnitude of a galaxy at 1500 Å. For a blind search, semi-empirical luminosity functions are used to calculate the number of galaxies whose expected flux densities exceed an assumed detectability threshold. Plots of the minimum sky area, within which at least one detectable galaxy is expected at a given observing frequency, in the fiducial instantaneous passband of 104 km s-1, allow us to assess the blind search time necessary for detection by a given facility. We show that the chances for detection are the highest in the millimeter and submillimeter domains, but finding spontaneous emission in a blind search, especially from redshifts z ≫ 1, is a challenge even with powerful facilities, such as the Actama Large Millimeter/Submillimeter Array and Square Kilometre Array. The probability of success is higher for a targeted search of lines with principal quantum number n ∼ 10 in Lyman-break galaxies amplified by gravitational lensing. Detection of more than one hydrogen line in such a galaxy will allow for line identification and a precise determination of the galaxy's redshift. © 2013. The American Astronomical Society. All rights reserved..

Messenger S.J.,University of Missouri | Strelnitski V.,Ma-Maria
Monthly Notices of the Royal Astronomical Society | Year: 2010

We confirm, by numerical modelling, the suggestion by Johansson and Letokhov (JL) that some infrared (IR) transitions of circumstellar Fe ii may be inverted by radiative pumping and can, in principle, act as lasers. In contrast with JL, we show that the inversion of populations can be created directly, by the diluted blackbody continuum of the nearby star, without the intermediacy of trapped Lyα photons. Besides η Car (the target object of the JL model), IR Fe ii lasers should be searched for in other objects with large detected amounts of Fe ii - quasars, supernova remnants, B[e] stars, T Tau stars, etc. However, assuming that the pumping cycle contains radiative steps (the most probable situation for an interstellar or circumstellar medium), we demonstrate that the probability of creating a high-gain natural laser is low (as opposed to the probability of creating a high-gain maser), which can explain the relative scarcity of the detected astrophysical lasers. In particular, the available indirect observational evidence indicates that the gain of the 1.7 μm Fe ii lasers in η Car must be low. IR observations with high spatial and spectral resolution are needed to verify this conclusion. © 2010 The Authors. Journal compilation © 2010 RAS.

Fish V.L.,Massachusetts Institute of Technology | Muehlbrad T.C.,Massachusetts Institute of Technology | Muehlbrad T.C.,Texas Lutheran University | Pratap P.,Massachusetts Institute of Technology | And 4 more authors.
Astrophysical Journal | Year: 2011

ClassI methanol masers are believed to be produced in the shock-excited environment around star-forming regions. Many authors have argued that the appearance of various subsets of classI masers may be indicative of specific evolutionary stages of star formation or excitation conditions. Until recently, however, no major interferometer was capable of imaging the important 36 GHz transition. We report on Expanded Very Large Array observations of the 36 GHz methanol masers and Submillimeter Array observations of the 229 GHz methanol masers in DR21(OH), DR21N, and DR21W. The distribution of 36 GHz masers in the outflow of DR21(OH) is similar to that of the other classI methanol transitions, with numerous multitransition spatial overlaps. At the site of the main continuum source in DR21(OH), classI masers at 36 and 229 GHz are found in virtual overlap with classII 6.7 GHz masers. To the south of the outflow, the 36 GHz masers are scattered over a large region but usually do not appear coincident with 44 GHz masers. In DR21W, we detect an "S-curve" signature in Stokes V that implies a large value of the magnetic field strength if interpreted as due to Zeeman splitting, suggesting either that classI masers may exist at higher densities than previously believed or that the direct Zeeman interpretation of S-curve Stokes V profiles in classI masers may be incorrect. We find a diverse variety of different maser phenomena in these sources, suggestive of differing physical conditions among them. © 2011. The American Astronomical Society. All rights reserved.

Strelnitski V.,Ma-Maria
Proceedings of the International Astronomical Union | Year: 2012

The groundwork of the cosmic maser theory was laid four decades ago. The elapsed time, including the few years after the last IAU symposium dedicated to masers, did not add much to the fundamentals. In this review, I will summarize some cornerstones of the theory, with an emphasis on issues that don't seem to have received due attention in the past. I will also comment on some new developments. Copyright © International Astronomical Union 2012.


Ma-Maria | Date: 2013-12-17

Glasses, sun glasses, frames, lenses, cases for glasses; helmets and protective goggles. Articles for gymnastic and sport.

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