Search Publications
X-Ray Echo from the Sagittarius C Complex and 500-year Activity History of Sagittarius A*
Koyama, Katsuji; Nobukawa, Masayoshi; Nakashima, Shinya +3 more
This paper presents Suzaku results obtained for the Sagittarius (Sgr) C region using the concept of X-ray reflection nebulae (XRNe) as the echo of past flares from a super-massive black hole, Sgr A*. The Sgr C complex is composed of several molecular clouds proximately located in projected distance. The X-ray spectra of Sgr C were analyzed based o…
The SWELLS survey - V. A Salpeter stellar initial mass function in the bulges of massive spiral galaxies
Treu, Tommaso; Marshall, Philip J.; Auger, M. W. +6 more
Recent work has suggested that the stellar initial mass function (IMF) is not universal, but rather is correlated with galaxy stellar mass, stellar velocity dispersion or morphological type. In this paper, we investigate variations of the IMF within individual galaxies. For this purpose, we use strong lensing and gas kinematics to measure independ…
Supervolcanoes within an ancient volcanic province in Arabia Terra, Mars
Bleacher, Jacob E.; Michalski, Joseph R.
Several irregularly shaped craters located within Arabia Terra, Mars, represent a new type of highland volcanic construct and together constitute a previously unrecognized Martian igneous province. Similar to terrestrial supervolcanoes, these low-relief paterae possess a range of geomorphic features related to structural collapse, effusive volcani…
The Metallicity Evolution of Star-forming Galaxies from Redshift 0 to 3: Combining Magnitude-limited Survey with Gravitational Lensing
Richard, J.; Yuan, T. -T.; Kewley, L. J.
We present a comprehensive observational study of the gas-phase metallicity of star-forming galaxies from z ~ 0 → 3. We combine our new sample of gravitationally lensed galaxies with existing lensed and non-lensed samples to conduct a large investigation into the mass-metallicity (MZ) relation at z > 1. We apply a self-consistent metallicity ca…
A new way to measure supermassive black hole spin in accretion disc-dominated active galaxies
Done, Chris; Ward, Martin; Jin, C. +1 more
We show that disc continuum fitting can be used to constrain black hole spin in a subclass of narrow-line Seyfert 1 (NLS1) active galactic nuclei as their low mass and high mass accretion rate means that the disc peaks at energies just below the soft X-ray bandpass. We apply the technique to the NLS1 PG1244+026, where the optical/UV/X-ray spectrum…
Limits on the Dependence of the Fine-Structure Constant on Gravitational Potential from White-Dwarf Spectra
Barstow, M. A.; Holberg, J. B.; Webb, J. K. +5 more
We propose a new probe of the dependence of the fine-structure constant α on a strong gravitational field using metal lines in the spectra of white-dwarf stars. Comparison of laboratory spectra with far-UV astronomical spectra from the white-dwarf star G191-B2B recorded by the Hubble Space Telescope Imaging Spectrograph gives limits of Δα/α=(4.2±1…
The thermal structure of Titan’s upper atmosphere, I: Temperature profiles from Cassini INMS observations
Wahlund, J. -E.; Edberg, N. J. T.; Ågren, K. +3 more
We derive vertical temperature profiles from Ion Neutral Mass Spectrometer (INMS) N2 density measurements from 32 Cassini passes. We find that the average temperature of Titan’s thermosphere varies significantly from pass-to-pass between 112 and 175 K. The temperatures from individual temperature profiles also varies considerably, with …
The Intriguing Stellar Populations in the Globular Clusters NGC 6388 and NGC 6441
Anderson, J.; Milone, A. P.; Sarajedini, A. +8 more
NGC 6388 and NGC 6441 are two massive Galactic bulge globular clusters that share many properties, including the presence of an extended horizontal branch (HB), quite unexpected because of their high metal content. In this paper we use Hubble Space Telescope's WFPC2, ACS, and WFC3 images and present a broad multicolor study of their stellar conten…
Herschel Exploitation of Local Galaxy Andromeda (HELGA). III. The Star Formation Law in M31
Gordon, Karl D.; Lebouteiller, Vianney; Wilson, Christine D. +17 more
We present a detailed study of how the star formation rate (SFR) relates to the interstellar medium (ISM) of M31 at ~140 pc scales. The SFR is calculated using the far-ultraviolet and 24 µm emission, corrected for the old stellar population in M31. We find a global value for the SFR of 0.25^{+0.06}_{-0.04}\,M_{\odot }\,yr^{-1} and compare th…
Stealth Coronal Mass Ejections: A Perspective
Howard, Timothy A.; Harrison, Richard A.
"Stealth CME" has become a commonly used term in recent studies of solar activity. It refers to a coronal mass ejection (CME) with no apparent solar surface association, and therefore has no easily identifiable signature to locate the region on the Sun from which the CME erupted. We review the literature and express caution in categorising CMEs in…