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Keck Spectroscopy of Red Giant Stars in the Vicinity of M31'S Massive Globular Cluster G1
Rich, R. Michael; Guhathakurta, Puragra; Reitzel, David B.
We present results from an ongoing Keck spectroscopic survey of red giant stars in a field located along the major axis of M31, ~34 kpc in projection from the nucleus and near the luminous globular cluster G1. We use multislit LRIS spectroscopy to measure the Ca II near-infrared triplet in 41 stars ranging in apparent magnitude from 20<I<22.…
Star Clusters in Virgo and Fornax Dwarf Irregular Galaxies
Olsen, Knut; Seth, Anil; Lotz, Jennifer +2 more
We present the results of a search for clusters in dwarf irregular galaxies in the Virgo and Fornax Clusters using Hubble Space Telescope (HST) WFPC2 snapshot data. The galaxy sample includes 28 galaxies, 11 of which are confirmed members of the Virgo and Fornax Clusters. In the 11 confirmed members, we detect 237 cluster candidates and determine …
Detection of Intergalactic He II Absorption at Redshift 3.5
Anderson, Scott F.; Schneider, Donald P.; York, Donald G. +5 more
The large number of quasars found in the Sloan Digital Sky Survey has allowed searches for elusive, clear lines of sight toward He II Lyα absorption, a sensitive probe of the intergalactic medium. The few known systems indicate that He II reionization occurs at z>3. We report the detection of a He II Lyα absorption edge in a quasar spectrum at …
Lick Northern Proper Motion Program. III. Lick NPM2 Catalog
Monet, David G.; Hanson, Robert B.; Jones, Burton F. +1 more
The Lick Northern Proper Motion (NPM) program, a two-epoch (1947-1988) photographic survey of the northern two-thirds of the sky (δ>~-23deg), has measured absolute proper motions, on an inertial system defined by distant galaxies, for 378,360 stars in the magnitude range 8<~B<~18. The 1993 NPM1 Catalog contains 148,940 stars in…
The Inner Ring of NGC 4736: Star Formation on a Resonant Pattern
Muñoz-Tuñón, Casiana; Aguerri, J. Alfonso L.; Caon, Nicola
We revise the explanation for the ``expanding H II regions ring'' of NGC 4736. From the analysis of long-slit spectra, we identify structures within the emission region previously reported in the literature as a single ring (former parameters: R~47", FWHM=21"). The H II ring is located at 35" (1.12 kpc) galactocentric distance, and its thickness i…
NGC 6543. I. Understanding the Anatomy of the Cat's Eye
Balick, Bruce
Hubble Space Telescope images of NGC 6543 taken in 1994.7 through a variety of narrowband filters yield a very detailed structure in emission lines of low and moderate ionization. On the whole, the core of NGC 6543 is optically thin to ionizing radiation. As expected, the general ionization state of the nebula decreases with radius; however, some …
Resolving the Stellar Population of the Standard Elliptical Galaxy NGC 3379
Ferguson, Henry C.; Gregg, Michael D.; Minniti, Dante +2 more
Using the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) on board the Hubble Space Telescope, we have obtained F110W (~J) and F160W (~H) images of three fields in NGC 3379, a nearby normal giant elliptical galaxy. These images resolve individual red giant stars, yielding the first accurate color-magnitude diagrams for a normal luminou…
The Orbit and Albedo of Trans-Neptunian Binary (58534) 1997 CQ29
Noll, Keith S.; Stephens, Denise C.; Grundy, Will M. +2 more
We have measured the separations and position angles of the two components of the binary trans-Neptunian object (58534) 1997 CQ29 at eight epochs. From these data we are able to constrain the orbit and mass of this binary system. The best-fitting orbit has an orbital period of P=312+/-3 days. The orbital eccentricity is e=0.45+/-0.03 an…
Nuclear Properties of a Sample of Nearby Spiral Galaxies from Hubble Space Telescope STIS Imaging
Marconi, A.; Capetti, A.; Carollo, C. M. +17 more
We present surface photometry for the central regions of a sample of 48 spiral galaxies (mostly unbarred and barred of type Sbc or Sc) observed with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. Surface brightness profiles (SBPs) were derived and modeled with a Nuker law. We also analyzed archival Wide Field Planeta…
XMM-Newton Observations of Two High-Redshift Quasars: RX J1028-0844 and BR 0351-1034
Elvis, M.; Grupe, D.; Mathur, S. +1 more
We report the results of XMM-Newton observations of two high-redshift quasars, one radio-loud, RX J1028.6-0844 (z=4.276) and one radio-quiet, BR 0351-1034 (z=4.351). We find that the evidence for strong excess absorption toward RX J1028-0844 is marginal at best, contrary to previous claims. The superior sensitivity and broader, softer energy range…