Search Publications
The Globular Cluster System in NGC 5866: Optical Observations from Hubble Space Telescope Advanced Camera for Surveys
Blakeslee, John P.; Cantiello, Michele; Raimondo, Gabriella
We perform a detailed study of the globular cluster (GC) system in the galaxy NGC 5866 based on F435W, F555W, and F625W (~B, V, and R) Hubble Space Telescope Advanced Camera for Surveys images. Adopting color, size, and shape selection criteria, the final list of GC candidates comprises 109 objects, with small estimated contamination from backgrou…
Evidence for the Importance of Resonance Scattering in X-Ray Emission Line Profiles of the O Star ζ Puppis
Leutenegger, Maurice A.; Kahn, Steven M.; Owocki, Stanley P. +1 more
We fit the Doppler profiles of the He-like triplet complexes of O VII and N VI in the X-ray spectrum of the O star ζ Pup, using XMM-Newton RGS data collected over ~400 ks of exposure. We find that they cannot be well fit if the resonance and intercombination lines are constrained to have the same profile shape. However, a significantly better fit …
Optical Spectroscopy of the Environment of a ULX in NGC 7331
Tennant, Allyn F.; Swartz, Douglas A.; Ghosh, Kajal K. +3 more
Optical photometric and spectroscopic data are presented that show an association of an ultraluminous X-ray source in NGC 7331 with a young star cluster of mass M=(1.1+/-0.2)×105 Msolar and age tc=4.25+/-0.25 Myr. If the ULX is part of the bright stellar cluster, then the mass of the progenitor of the compact accre…
The Dynamical Distinction between Elliptical and Lenticular Galaxies in Distant Clusters: Further Evidence for the Recent Origin of S0 Galaxies
Treu, Tommaso; Ellis, Richard S.; Moran, Sean M. +3 more
We examine resolved spectroscopic data obtained with the Keck II telescope for 44 spheroidal galaxies in the fields of two rich clusters, Cl 0024+16 (z=0.40) and MS 0451-03 (z=0.54) and contrast this with similar data for 23 galaxies within the redshift interval 0.3<z<0.65 in the GOODS northern field. For each galaxy we examine the case for …
Discovery of the Pre-Main-Sequence Population of the Stellar Association LH 95 in the Large Magellanic Cloud with Hubble Space Telescope Advanced Camera for Surveys Observations
Henning, Thomas; Gouliermis, Dimitrios A.; Dolphin, Andrew E. +3 more
We report the discovery of an extraordinary number of pre-main-sequence (PMS) stars in the vicinity of the stellar association LH 95 in the Large Magellanic Cloud (LMC). Using the Advanced Camera for Surveys on board the Hubble Space Telescope in wide-field mode, we obtained deep high-resolution imaging of the main body of the association and of a…
Doppler Velocities Measured in Coronal Emission Lines from a Bright Point Observed with the EUNIS Sounding Rocket
Brosius, Jeffrey W.; Thomas, Roger J.; Rabin, Douglas M.
Spectroscopic measurements of a coronal bright point obtained with the Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) sounding rocket instrument on 2006 April 12 show both upflows and downflows in all five of the best observed emission lines. Relative velocities on opposite sides of the feature were found to be +/-15 km s-1 i…
Can Chandra Resolve the Remaining Cosmic X-Ray Background?
Hickox, Ryan C.; Markevitch, Maxim
The deepest extragalactic X-ray observation, the 2 Ms Chandra Deep Field North (CDF-N), resolves ~80% of the total extragalactic cosmic X-ray background (CXB) in the 1-2 keV band. Recent work has shown that 70% of the remaining CXB flux is associated with sources detected by the Hubble Space Telescope (HST). This paper uses the existing CDF-N data…
Plasma Outflows in Coronal Streamers
Noci, Giancarlo; Gavryuseva, Elena
In this Letter we show that it is possible to determine slow velocities (~20 km s-1) in the extended solar corona by means of the ratio of the resonance doublet of O VI. We apply this technique to a quiescent streamer at solar minimum, observed by the Ultraviolet Coronagraph Spectrometer (UVCS) for 4 consecutive days, and determine the …
Coronal Diagnostic Spectrometer Observations of Isothermal and Multithermal Coronal Loops
Mason, H. E.; Del Zanna, G.; Schmelz, J. T. +3 more
A data set obtained on 2003 January 17 with the Coronal Diagnostic Spectrometer (CDS) shows two loops sitting side by side on the solar disk. These loops are oriented along the CDS slit, so all pixels in each loop were observed simultaneously. So, although the instrument has a relatively slow time cadence, changes as a function of time that may oc…
Synthetic Mid-UV Spectroscopic Indices of Stars
Chavez, M.; Buzzoni, A.; Morossi, C. +4 more
Using the UVBLUE library of synthetic stellar spectra we have computed a set of mid-UV line and continuum spectroscopic indices. We explore their behavior in terms of the leading stellar parameters (Teff, logg). The overall result is that synthetic indices follow the general trends depicted by those computed from empirical databases. Se…