Search Publications
Advanced Camera for Surveys Photometry of the Cluster RDCS 1252.9-2927: The Color-Magnitude Relation at z = 1.24
Ford, H. C.; Demarco, R.; Infante, L. +20 more
We investigate the color-magnitude (CM) relation of galaxies in the distant X-ray-selected cluster RDCS 1252.9-2927 at z=1.24 using images obtained with the Advanced Camera for Surveys on the Hubble Space Telescope in the F775W and F850LP bandpasses. We select galaxies based on morphological classifications extending about 3.5 mag down the galaxy …
Identification of Solar Sources of Major Geomagnetic Storms between 1996 and 2000
Zhang, J.; Bothmer, V.; Howard, R. A. +1 more
This paper presents identification of solar coronal mass ejection (CME) sources for 27 major geomagnetic storms (defined by disturbance storm timeindex<=-100 nT) occurring between 1996 and 2000. Observations of CMEs and their solar surface origins are obtained from the Large Angle and Spectrometric Coronagraph (LASCO) and the EUV Imaging Telesc…
The [C II] 158 Micron Line Deficit in Ultraluminous Infrared Galaxies Revisited
Lutz, D.; Genzel, R.; Sturm, E. +5 more
We present a study of the [C II] 157.74 µm fine-structure line in a sample of 15 ultraluminous infrared (IR) galaxies (IR luminosity LIR>=1012Lsolar ULIRGs) using the Long Wavelength Spectrometer (LWS) on the Infrared Space Observatory (ISO). We confirm the observed order of magnitude deficit (compared to …
Microlensing Optical Depth toward the Galactic Bulge from Microlensing Observations in Astrophysics Group Observations during 2000 with Difference Image Analysis
Sumi, T.; Honda, M.; Saito, Y. +27 more
We analyze the data of the gravitational microlensing survey carried out by the Microlensing Observations in Astrophysics (MOA) group during 2000 toward the Galactic bulge (GB). Our observations are designed to detect efficient high-magnification events with faint source stars and short-timescale events, by increasing the sampling rate up to ~6 ti…
The Properties of Small Magnetic Regions on the Solar Surface and the Implications for the Solar Dynamo(s)
Title, Alan M.; Schrijver, Carolus J.; Hagenaar, Hermance J.
We find that bipolar active regions that emerge onto the Sun's surface are part of a smoothly decreasing frequency distribution that spans almost 4 orders of magnitude in flux and 8 orders of magnitude in frequency. Distributions of emergence latitude and dipole orientation narrow from nearly uniform for the smallest observed ephemeral regions (~5…
XMM-Newton Reveals the Quasar Outflow in PG 1115+080
Brandt, W. N.; Chartas, G.; Gallagher, S. C.
We report on an observation of the broad absorption line (BAL) quasar PG 1115+080 performed with the XMM-Newton observatory. Spectral analysis reveals the second case of a relativistic X-ray-absorbing outflow in a BAL quasar. The first case was revealed in a recent observation of APM 08279+5255 with the Chandra X-Ray Observatory. As in the case of…
A Tale of Two Stars: The Extreme O7 Iaf+ Supergiant AV 83 and the OC7.5 III((f)) star AV 69
Hillier, D. John; Lennon, D. J.; Smith, L. J. +5 more
We present a detailed study of AV 83, an O7 Iaf+ supergiant, and AV 69 [OC7.5 III((f))] in the SMC. The stars have similar effective temperatures and luminosities but show very different wind signatures. For our study we have used the non-LTE line-blanketed atmosphere code developed by Hillier and Miller, which explicitly allows for line blanketin…
Latitude-dependent Effects in the Stellar Wind of η Carinae
Smith, Nathan; Hillier, D. John; Gull, Theodore R. +2 more
The Homunculus reflection nebula around η Carinae provides a rare opportunity to observe the spectrum of a star from more than one direction. In the case of η Car, the nebula's geometry is known well enough to infer how line profiles vary with latitude. We present Space Telescope Imaging Spectrograph (STIS) spectra of several positions in the Homu…
Toward a Self-Consistent Model of the Ionized Absorber in NGC 3783
Elvis, M.; Nicastro, F.; Krongold, Y. +3 more
We present a detailed model for the ionized absorbing gas evident in the 900 ks Chandra HETGS spectrum of NGC 3783. The analysis was carried out with PHASE, a new tool designed to model X-ray and UV absorption features in ionized plasmas. The 0.5-10 keV intrinsic continuum of the source is well represented by a single power law (Γ=1.53) and a soft…
Hα Spectroscopy of Galaxies at z > 2: Kinematics and Star Formation
Pettini, Max; Erb, Dawn K.; Shapley, Alice E. +5 more
We present near-infrared spectroscopy of Hα emission lines in a sample of 16 star-forming galaxies at redshifts 2.0<z<2.6. Our targets are drawn from a large sample of galaxies photometrically selected and spectroscopically confirmed to lie in this redshift range. We have obtained this large sample with an extension of the broadband Un<…