Search Publications
X-ray Emission from the Sombrero Galaxy: A Galactic-scale Outflow
Spitler, Lee R.; Jones, Christine; Gilfanov, Marat +8 more
Based on new and archival Chandra observations of the Sombrero galaxy (M 104 = NGC 4594), we study the X-ray emission from its nucleus and the extended X-ray emission in and around its massive stellar bulge. We find that the 0.3-8 keV luminosity of the nucleus appears constant at ~2.4 × 1040 erg s-1, or ~10-7 of it…
X-Ray Characteristics of NGC 3516: A View through the Complex Absorber
Turner, T. J.; Kraemer, S. B.; Reeves, J. N. +1 more
We consider new Suzaku data for NGC 3516 taken during 2009 along with other recent X-ray observations of the source. The cumulative characteristics of NGC 3516 cannot be explained without invoking changes in the line-of-sight absorption. Contrary to many other well-studied Seyfert galaxies, NGC 3516 does not show a positive lag of hard X-ray photo…
Temporal Variability of Active Region Outflows
Warren, Harry P.; Ugarte-Urra, Ignacio
Recent observations from the Extreme-ultraviolet Imaging Spectrometer (EIS) on board Hinode have shown that low-density areas on the periphery of active regions are characterized by strong blueshifts in the emission of spectral lines formed at 1 MK. These Doppler shifts have been associated with outward propagating disturbances observed with extre…
The Formation of Kiloparsec-scale H I Holes in Dwarf Galaxies
Van Dyk, Schuyler D.; Cannon, John M.; Dolphin, Andrew E. +10 more
The origin of kpc-scale holes in the atomic hydrogen (H I) distributions of some nearby dwarf irregular galaxies presents an intriguing problem. Star formation histories (SFHs) derived from resolved stars give us the unique opportunity to study past star-forming events that may have helped shape the currently visible H I distribution. Our sample o…
A Microlensing Measurement of Dark Matter Fractions in Three Lensing Galaxies
Wyithe, J. S. B.; Bate, N. F.; Floyd, D. J. E. +1 more
Direct measurements of dark matter distributions in galaxies are currently only possible through the use of gravitational lensing observations. Combinations of lens modeling and stellar velocity dispersion measurements provide the best constraints on dark matter distributions in individual galaxies, however they can be quite complex. In this paper…
Detection of Supergranulation Alignment in Polar Regions of the Sun by Helioseismology
Zhao, Junwei; Kosovichev, Alexander G.; Sekii, Takashi +1 more
We report on a new phenomenon of "alignment" of supergranulation cells in the polar regions of the Sun. Recent high-resolution data sets obtained by the Solar Optical Telescope on board the Hinode satellite enabled us to investigate supergranular structures in high-latitude regions of the Sun. We have carried out a local helioseismology time-dista…
Water Production by Comet 103P/Hartley 2 Observed with the SWAN Instrument on the SOHO Spacecraft
Bertaux, J. -L.; Combi, M. R.; Quémerais, E. +2 more
Global water production rates were determined from the Lyα emission of hydrogen around comet 103P/Hartley 2, observed with the SWAN (Solar Wind Anisotropies) all-sky camera on the SOHO spacecraft from 2010 September 14 through December 12. This time period included the November 4 flyby by the EPOXI spacecraft. Water production was three times lowe…
HST/COS Observations of Galactic High-velocity Clouds: Four Active Galactic Nucleus Sight Lines through Complex C
Shull, J. Michael; Lockman, Felix J.; Penton, Steven V. +3 more
We report ultraviolet spectra of Galactic high-velocity clouds (HVCs) in Complex C, taken by the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST), together with new 21 cm spectra from the Green Bank Telescope. The wide spectral coverage and higher signal-to-noise ratio, compared to previous HST spectra, provide better velocity…
Spectroscopic Observations of Continuous Outflows and Propagating Waves from NOAA 10942 with Extreme Ultraviolet Imaging Spectrometer/Hinode
Hara, H.; Nishizuka, N.
We focused on "sit-and-stare" observations of an outflow region at the edge of active region NOAA 10942 on 2007 February 20 obtained by the Extreme ultraviolet Imaging Spectrometer on board Hinode. We analyzed the data above the base of the outflow and found both continuous outflows and waves, which propagate from the base of the outflow. The spec…
Infrared Spectra and Spectral Energy Distributions for Dusty Starbursts and Active Galactic Nuclei
Lebouteiller, Vianney; Weedman, Daniel; Sargsyan, Lusine +4 more
We present spectroscopic results for all galaxies observed with the Spitzer Infrared Spectrograph (IRS) that also have total infrared fluxes f IR measured with the Infrared Astronomical Satellite (IRAS), also using AKARI photometry when available. Infrared luminosities and spectral energy distributions (SEDs) from 8 µm to 160 &mic…