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Hot Populations in M87 Globular Clusters
Sohn, Sangmo T.,O'Connell, Robert W.,Kundu, Arunav,Landsman, Wayne B.,Burstein, David,Bohlin, Ralph C.,Frogel, Jay A.,Rose, James A. American Institute of Physics 2006 The Astronomical journal Vol.131 No.2
<P>To explore the production of UV-bright stars in old, metal-rich populations like those in elliptical galaxies, we have obtained Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph far- and near-UV photometry of globular clusters (GCs) in four fields in the giant elliptical (gE) galaxy M87. To a limit of m<SUB>FUV</SUB> ~ 25 we detect a total of 66 GCs in common with the deep HST optical-band study of Kundu et al. Despite strong overlap in V- and I-band properties, the M87 GCs have UV-optical properties that are distinct from clusters in the Milky Way and in M31. M87 clusters, especially metal-poor ones, produce larger hot horizontal-branch populations than do Milky Way analogs. In color plots including the near-UV band, the M87 clusters appear to represent an extension of the Milky Way sequence. Cluster mass is probably not a factor in these distinctions. The most metal-rich M87 GCs in our sample are near solar metallicity and overlap the local E galaxy sample in estimated Mg<SUB>2</SUB> line indices. Nonetheless, the clusters produce much more UV light at a given Mg<SUB>2</SUB>, being up to 1 mag bluer than any gE galaxy in (FUV - V) color. The M87 GCs do not appear to represent a transition between Milky Way-type clusters and E galaxies. The differences are in the correct sense if the clusters are significantly older than the E galaxies.</P><P>Comparisons with Galactic open clusters indicate that the hot stars lie on the extreme horizontal branch, rather than being blue stragglers, and that the extreme horizontal branch becomes well populated for ages ≳5 Gyr. Existing model grids for clusters do not match the observations well, due to poorly understood giant branch mass loss or perhaps high helium abundances. We find that 41 of our UV detections have no optical-band counterparts. Most appear to be UV-bright background galaxies seen through M87. Eleven near-UV variable sources detected at only one epoch in the central field are probably classical novae. Two recurrent variable sources have no obvious explanation but could be related to activity in the relativistic jet.</P>
Orientation-dependent stereo Wigner time delay and electron localization in a small molecule
Vos, J.,Cattaneo, L.,Patchkovskii, S.,Zimmermann, T.,Cirelli, C.,Lucchini, M.,Kheifets, A.,Landsman, A. S.,Keller, U. American Association for the Advancement of Scienc 2018 Science Vol.360 No.6395
<P>Attosecond metrology of atoms has accessed the time scale of the most fundamental processes in quantum mechanics. Transferring the time-resolved photoelectric effect from atoms to molecules considerably increases experimental and theoretical challenges. Here we show that orientation-and energy-resolved measurements characterize the molecular stereo Wigner time delay. This observable provides direct information on the localization of the excited electron wave packet within the molecular potential. Furthermore, we demonstrate that photoelectrons resulting from the dissociative ionization process of the CO molecule are preferentially emitted from the carbon end for dissociative (2)Sigma states and from the center and oxygen end for the (2)Pi states of the molecular ion. Supported by comprehensive theoretical calculations, this work constitutes a complete spatially and temporally resolved reconstruction of the molecular photoelectric effect.</P>
Active tailoring of nanoantenna plasmonic fields using few-cycle laser pulses
Choi, S.,Ciappina, M. F.,Pé,rez-Herná,ndez, J. A.,Landsman, A. S.,Kim, Y.-J.,Kim, S. C.,Kim, D. American Physical Society 2016 Physical Review A Vol.93 No.2
<P>Plasmonic nanoatennas are a versatile tool for coherently manipulating light on a nanoscale by confining electric fields of the driving laser into subwavelength volumes, thereby significantly enhancing electric near fields. It is normally assumed that the time-dependent spectral properties of these near fields are independent of the duration of the driving laser pulse. Here we show that when a few-cycle laser pulse shines on a bow-tie nanoantenna, its spectral properties are dramatically modified, as evidenced by a large shift of the center wavelength of the near field, relative to the driving laser. In addition, for certain geometries, a second color appears in the near field, creating conditions for generation of an isolated attosecond pulse at megahertz repetition rate. Our results open the door to frequency-tunable ultrafast sources at nanometer scale without tuning the frequency of the driving laser.</P>
Towards a Comprehensive Catalog of Zebrafish Behavior 1.0 and Beyond
Kalueff, Allan V.,Gebhardt, Michael,Stewart, Adam Michael,Cachat, Jonathan M.,Brimmer, Mallorie,Chawla, Jonathan S.,Craddock, Cassandra,Kyzar, Evan J.,Roth, Andrew,Landsman, Samuel,Gaikwad, Siddharth Mary Ann Liebert 2013 Zebrafish Vol.10 No.1