Search Publications
A Population of Massive Globular Clusters in NGC 5128
Ho, Luis C.; Martini, Paul
We present velocity dispersion measurements of 14 globular clusters in NGC 5128 (Centarus A) obtained with the MIKE echelle spectrograph on the 6.5 m Magellan Clay telescope. These clusters are among the most luminous globular clusters in NGC 5128 and have velocity dispersions comparable to the most massive clusters known in the Local Group, rangi…
Identification of Type Ia Supernovae at Redshift 1.3 and Beyond with the Advanced Camera for Surveys on the Hubble Space Telescope
Dickinson, Mark; Ferguson, Henry C.; Giavalisco, Mauro +15 more
We present discoveries of Type Ia supernovae (SNe Ia) at z>1 and the photometric diagnostic used to discriminate them from other types of SNe detected during the Great Observatories Origins Deep Survey (GOODS) Hubble Space Telescope Treasury Program with the Advanced Camera for Surveys (ACS). Photometric redshift measurements of the hosts combi…
Supersoft X-Ray Sources in M31. I. A Chandra Survey and an Extension to Quasi-soft Sources
Barmby, P.; Greiner, J.; Murray, S. S. +9 more
We report on very soft X-ray sources (VSSs) in M31. In a survey that was most sensitive to soft sources in four 8'×8' regions covered by Chandra's ACIS-S S3 CCD, we find 33 VSSs that appear to belong to M31. Fifteen VSSs have spectral characteristics mirroring the supersoft X-ray sources studied in the Magellanic Clouds and M…
Nitrogen and Oxygen Abundance Variations in the Outer Ejecta of η Carinae: Evidence for Recent Chemical Enrichment
Smith, Nathan; Morse, Jon A.
We present optical spectra of the ionized ``outer ejecta'' of η Car that reveal differences in chemical composition at various positions. In particular, young condensations just outside the dusty Homunculus nebula show strong nitrogen lines and little or no oxygen, but farther away, nitrogen lines weaken and oxygen lines become stronger. The obser…
The Possible Detection of Cosmological Reionization Sources
Panagia, N.; Fall, S. Michael; Stiavelli, M.
We compare the available catalogs of z~6 galaxies in the Hubble Ultra- Deep Field and in the Great Observatories Origins Deep Survey with the expected properties of the sources of cosmological reionization from our previous theoretical study. Our approach is based on the mean surface brightness of the sources required for reionization and depends …
Relativistic O VIII Emission and Ionized Outflow in NGC 4051 Measured with XMM-Newton
Page, M. J.; Mason, K. O.; Cordova, F. A. +4 more
We present XMM-Newton Reflection Grating Spectrometer observations of the soft X-ray spectrum of NGC 4051 and explore their implications for the inner accretion disk and ionized outflow in the active galactic nucleus. We fit the soft X-ray excess with a relativistically broadened O VIII recombination spectrum, including the entire line series and …
Testing Radiatively Inefficient Accretion Flow Theory: An XMM-Newton Observation of NGC 3998
Ptak, A.; Ho, L. C.; Terashima, Y. +1 more
We present the results of a 10 ks XMM-Newton observation of NGC 3998, a ``type I'' LINER galaxy (i.e., with significant broad Hα emission). Our goal is to test the extent to which radiatively inefficient accretion flow (RIAF) models and/or scaled-down active galactic nuclei (AGNs) models are consistent with the observed properties of NGC 3998. A p…
On the Determination of Michelson Doppler Imager High-Degree Mode Frequencies
Schou, J.; Korzennik, S. G.; Rabello-Soares, M. C.
The characteristics of the solar acoustic spectrum are such that mode lifetimes get shorter and spatial leaks get closer in frequency as the degree of a mode increases for a given order. A direct consequence of this property is that individual p-modes are resolved only at low and intermediate degrees and that at high degrees individual modes blend…
Stellar and Gaseous Abundances in M82
Maiolino, R.; Ranalli, P.; Comastri, A. +1 more
The near-infrared (near-IR) absorption spectra of starburst galaxies show several atomic and molecular lines from red supergiants that can be used to infer reliable stellar abundances. The metals locked in stars give a picture of the galaxy metallicity prior to the last burst of star formation. The enrichment of the new generation of stars born in…
Deep Luminosity Functions of Old and Intermediate-Age Globular Clusters in NGC 1316: Evidence for Dynamical Evolution of Second-Generation Globular Clusters
Gilmore, Diane; Whitmore, Bradley C.; Schweizer, François +1 more
The Advanced Camera for Surveys on board the Hubble Space Telescope has been used to obtain deep high-resolution images of the giant early-type galaxy NGC 1316, an obvious merger remnant. These observations supersede previous shallower imagery that revealed the presence of a population of metal-rich globular clusters of intermediate age (~3 Gyr). …