Search Publications
A Hubble Space Telescope Census of Nuclear Star Clusters in Late-Type Spiral Galaxies. I. Observations and Image Analysis
Böker, Torsten; Ho, Luis C.; Shields, Joseph C. +4 more
We present new Hubble Space Telescope I-band images of a sample of 77 nearby late-type spiral galaxies with low inclination. The main purpose of this catalog is to study the frequency and properties of nuclear star clusters. In 59 galaxies of our sample, we have identified a distinct, compact (but resolved), and dominant source at or very close to…
X-ray background measurements with XMM-Newton EPIC
De Luca, A.; Warwick, R. S.; Page, M. +1 more
We discuss the methods used to compile a high signal-to-noise dataset representative of both the instrumental and cosmic background signal measured at high galactic latitude by the XMM-Newton EPIC cameras. The characteristics of the EPIC background are described and the potential applications of the derived dataset in general science analysis are …
Evolving Submerged Meridional Circulation Cells within the Upper Convection Zone Revealed by Ring-Diagram Analysis
Hill, Frank; Toomre, Juri; Bogart, Richard S. +3 more
Using the local helioseismic technique of ring-diagram analysis applied to Michelson Doppler Imager (MDI) Dynamics Program data from the Solar and Heliospheric Observatory, we have discovered that the meridional flow within the upper convection zone can develop additional circulation cells whose boundaries wander in latitude and depth as the solar…
On the Relationship between Radio Emission and Black Hole Mass in Galactic Nuclei
Ho, Luis C.
We use a comprehensive database of black hole masses (MBH) and nuclear luminosities to investigate the relationship between radio emission and MBH. Our sample covers a wide range of nuclear activity, from nearby inactive nuclei to classical Seyfert 1 nuclei and luminous quasars. Contrary to some previous studies, we find that…
A Redshift z=6.56 Galaxy behind the Cluster Abell 370
Kneib, J. -P.; Motohara, K.; Capak, P. +5 more
We report the discovery of a redshift z=6.56 galaxy lying behind the cluster Abell 370. The object HCM 6A was found in a narrowband imaging survey using a 118 Å bandpass filter centered at 9152 Å in the Low-Resolution Imaging Spectrograph (LRIS) camera on the 10 m Keck II telescope. Candidate Lyα emitters were identified by the equivalent width of…
Nested and Single Bars in Seyfert and Non-Seyfert Galaxies
Peletier, Reynier F.; Laine, Seppo; Knapen, Johan H. +1 more
We analyze the observed properties of nested and single stellar bar systems in disk galaxies. The 112 galaxies in our sample comprise the largest matched Seyfert versus non-Seyfert galaxy sample of nearby galaxies with complete near-infrared or optical imaging sensitive to length scales ranging from tens of parsecs to tens of kiloparsecs. The pres…
A long hard look at MCG-6-30-15 with XMM-Newton
Young, A. J.; Nandra, K.; Iwasawa, K. +6 more
We present the first results from a 325-ks observation of the Seyfert 1 galaxy MCG-6-30-15 with XMM-Newton and BeppoSAX. The strong, broad, skewed iron line is clearly detected and is well characterized by a steep emissivity profile within 6rg (i.e. 6GM/c2) and a flatter profile beyond. The inner radius of the emission appear…
XMM-Newton Reflection Grating Spectrometer Observations of Discrete Soft X-Ray Emission Features from NGC 1068
Kahn, Steven M.; Paerels, Frits; Behar, Ehud +6 more
We present the first high-resolution, soft X-ray spectrum of the prototypical Seyfert 2 galaxy, NGC 1068. This spectrum was obtained with the XMM-Newton Reflection Grating Spectrometer (RGS). Emission lines from H-like and He-like low-Z ions (from C to Si) and Fe L-shell ions dominate the spectrum. Strong, narrow radiative recombination continua (…
HST color-magnitude diagrams of 74 galactic globular clusters in the HST F439W and F555W bands
Djorgovski, S. G.; Recio-Blanco, A.; Zoccali, M. +9 more
We present the complete photometric database and the color-magnitude diagrams for 74 Galactic globular clusters observed with the HST/WFPC2 camera in the F439W and F555W bands. A detailed discussion of the various reduction steps is also presented, and of the procedures to transform instrumental magnitudes into both the HST F439W and F555W flight …
Absolute Dimensions of the M-Type Eclipsing Binary YY Geminorum (Castor C): A Challenge to Evolutionary Models in the Lower Main Sequence
Torres, Guillermo; Ribas, Ignasi
We present new spectroscopic observations of the detached late-type double-lined eclipsing binary YY Geminorum (P=0.814 day), a member of the Castor sextuple system and one of the benchmarks for the comparison between observations and stellar evolution theory in the lower main sequence. In addition, we have reanalyzed existing light curves in seve…