Search Publications
Dynamical Evolution of the TW Hydrae Association
Ortega, V. G.; de la Reza, R.; Jilinski, E.
Using Galactic dynamics we have determined the age of the low-mass post-T Tauri stars in the TW Hya Association (TWA). To do so we applied the method of Ortega and coworkers to five stars of the association with Hipparcos-measured distances (TWA 1, TWA 4, TWA 9, TWA 11, and TWA 19). The method is based on the calculation of the past three-dimensio…
Spectral Statistics and Local Luminosity Function of a Complete Hard X-Ray Sample of the Brightest Active Galactic Nuclei
Ishisaki, Y.; Ueda, Y.; Miyaji, T. +2 more
We have measured the X-ray spectral properties of a complete flux-limited sample of bright active galactic nuclei (AGNs) from the HEAO-1 all-sky catalogs to investigate their statistics and provide greater constraints on the bright end of the hard X-ray luminosity function (HXLF) and the AGN population synthesis model of the X-ray background. Spec…
The Subparsec-Scale Radio Properties of Southern Starburst Galaxies. I. Supernova Remnants, the Supernova Rate, and the Ionized Medium in the NGC 253 Starburst
Tingay, S. J.; Lenc, E.
Wide-field, very long baseline interferometry observations of the nearby starburst galaxy NGC 253, obtained with the Australian Long Baseline Array, have produced a 2.3 GHz image with a maximum angular resolution of 15 mas (0.3 pc). Six sources were detected, all corresponding to sources identified in higher frequency (>5 GHz) VLA images. One o…
Dynamical Mass Estimates for Incomplete Orbits: Young Multiple Stars in Taurus and Ophiuchus
Nelan, E.; Prato, L.; Schaefer, G. H. +2 more
We present recent measurements of the orbital motion in the binaries DF Tau and ZZ Tau and in the triples Elias 12, T Tau, and V853 Oph. We observed these systems with the Fine Guidance Sensors on the Hubble Space Telescope and with adaptive optics imaging at the W. M. Keck and Gemini North Observatories. Based on our measurements and those presen…
Nature of Nuclear Rings in Unbarred Galaxies: NGC 7742 and NGC 7217
Moiseev, A. V.; Sil'chenko, O. K.
We have studied an unbarred Sb galaxy with a nuclear star-forming ring, NGC 7742, by means of two-dimensional spectroscopy, long-slit spectroscopy, and imaging and have compared the results with the properties of another galaxy of this type, NGC 7217, which was studied by us earlier. Both galaxies have many peculiar features in common: each has tw…
The Dynamical State and Blue Straggler Population of the Globular Cluster NGC 6266 (M62)
Valenti, E.; Possenti, A.; Beccari, G. +3 more
We have used a proper combination of multiband high-resolution Hubble Space Telescope WFPC2 and wide-field ground-based observations to image the Galactic globular cluster NGC 6266 (M62). The extensive photometric data set allows us to determine the center of gravity and to construct the most extended radial profile ever published for this cluster…
The Morphological Demographics of Galaxies in the Advanced Camera for Surveys Hubble Ultra Deep Parallel Fields
Infante, Leopoldo; Benítez, Narciso; Blakeslee, John P. +4 more
We present a morphological analysis of distant field galaxies using the deep Advanced Camera for Surveys images from the public parallel Near-Infrared Camera and Multi-Object Spectrometer observations of the Hubble Ultra Deep Field obtained in the F435W (B435), F606W (V606), F775W (i775), and F850LP (z850
Precision Kinematics and Related Parameters of the α Persei Open Cluster
Makarov, Valeri V.
A kinematical study of the nearby open cluster α Persei is presented based on the astrometric proper motions and positions in the Tycho-2 catalog and Second USNO CCD Astrographic Catalog (UCAC2). Using the astrometric data and photometry from the Tycho-2 and ground-based catalogs, 139 probable members of the cluster are selected, 18 of them new. B…
The Spiral Host Galaxy of the Double Radio Source 0313-192
White, Raymond E., III; Keel, William C.; Owen, Frazer N. +1 more
We present new Hubble Space Telescope (HST), Gemini South, and Chandra observations of the radio galaxy 0313-192, which hosts a 350 kpc double source and jets, even though previous data have suggested that it is a spiral galaxy. We measure the bulge scale and the luminosity, radial, and vertical profiles of disk starlight and consider the distribu…
XMM-Newton Observations of High-Redshift Quasars
Grupe, D.; Mathur, S.; Wilkes, B. +1 more
We report on our XMM-Newton observations of the high-redshift quasars BR 2237-0607 (z=4.558) and BR 0351-1034 (z=4.351). We also report on XMM-Newton observations of 19 other z>4 objects available in the public archive of which 14 were detected. We find that the optical to X-ray spectral index αox is correlated with the luminosity density at 25…