Search Publications
A high stellar velocity dispersion for a compact massive galaxy at redshift z = 2.186
van Dokkum, Pieter G.; Franx, Marijn; Kriek, Mariska
Recent studies have found that the oldest and most luminous galaxies in the early Universe are surprisingly compact, having stellar masses similar to present-day elliptical galaxies but much smaller sizes. This finding has attracted considerable attention, as it suggests that massive galaxies have grown in size by a factor of about five over the p…
Observed variations of methane on Mars unexplained by known atmospheric chemistry and physics
Lefèvre, Franck; Forget, François
The detection of methane on Mars has revived the possibility of past or extant life on this planet, despite the fact that an abiogenic origin is thought to be equally plausible. An intriguing aspect of the recent observations of methane on Mars is that methane concentrations appear to be locally enhanced and change with the seasons. However, metha…
Evidence of a long-term trend in total solar irradiance
Fröhlich, C.
Aims: During the solar minimum of 2008, the value of total solar irradiance at 1 AU (TSI) was more than 0.2 Wm-2 lower than during the last minimum in 1996, indicating for the first time a directly observed long-term change. On the other hand, chromospheric indices and hence solar UV irradiance do not exhibit a similar change.
Metho…
The Infrared Nuclear Emission of Seyfert Galaxies on Parsec Scales: Testing the Clumpy Torus Models
Telesco, C. M.; Fisher, R. S.; Packham, C. +6 more
We present subarcsecond resolution mid-infrared (mid-IR) photometry in the wavelength range from 8 to 20 µm of 18 Seyfert galaxies, reporting high spatial resolution nuclear fluxes for the entire sample. We construct spectral energy distributions (SEDs) that the active galactic nucleus (AGN) dominates, relatively uncontaminated by starlight,…
Massive Galaxies in COSMOS: Evolution of Black Hole Versus Bulge Mass but not Versus Total Stellar Mass Over the Last 9 Gyr?
Koekemoer, Anton M.; Trump, Jonathan R.; Comastri, Andrea +23 more
We constrain the ratio of black hole (BH) mass to total stellar mass of type-1 active galactic nuclei (AGNs) in the COSMOS survey at 1 < z < 2. For 10 AGNs at mean redshift z ~ 1.4 with both Hubble Space Telescope (HST)/ACS and HST/NICMOS imaging data, we are able to compute the total stellar mass M *,total, based on rest-frame UV…
The active nuclei of z < 1.0 3CRR radio sources
Hardcastle, M. J.; Croston, J. H.; Evans, D. A.
We combine Chandra and XMM-Newton X-ray data from our previous papers with new X-ray observations and with Spitzer mid-infrared (mid-IR) data in order to study the nature of the nuclei of radio galaxies and radio-loud quasars with z < 1.0 from the 3CRR sample. The significant increase in sample size over our previous work, the reduction of bias…
Red Supergiants as Potential Type IIn Supernova Progenitors: Spatially Resolved 4.6 µm CO Emission Around VY CMa and Betelgeuse
Smith, Nathan; Hinkle, Kenneth H.; Ryde, Nils
We present high-resolution 4.6 µm CO spectra of the circumstellar environments of two red supergiants (RSGs) that are potential supernova (SN) progenitors: Betelgeuse and VY Canis Majoris (VY CMa). Around Betelgeuse, 12CO emission within ±3'' (±12 km s-1) follows a mildly clumpy but otherwise spherical shell, smaller th…
An X-ray view of 82 LINERs with Chandra and XMM-Newton data
Guainazzi, M.; Jiménez-Bailón, E.; González-Martín, O. +2 more
We present the results of a homogeneous X-ray analysis for 82 nearby low-ionisation, narrow emission-line regions (LINERs) selected from the catalogue of Carrillo et al. (1999, Rev. Mex. Astron. Astrofis., 35, 187). All sources have available Chandra (68 sources) and/or XMM-Newton (55 sources) observations. This is the largest sample of LINERs wit…
Evidence for X-Ray Synchrotron Emission from Simultaneous Mid-Infrared to X-Ray Observations of a Strong Sgr A* Flare
Genzel, R.; Rouan, D.; Pantin, E. +22 more
This paper reports measurements of Sgr A* made with NACO in L' band (3.80 µm), Ks band (2.12 µm), and H band (1.66 µm), and with VISIR in N band (11.88 µm) at the ESO VLT, as well as with XMM-Newton at X-ray (2-10 keV) wavelengths. On 2007 April 4, a very bright flare was observed from Sgr A* simultaneously at L' band and X…
Ion heating resulting from pickup in magnetic reconnection exhausts
Lin, R. P.; Phan, T. D.; Lepri, S. T. +6 more
The heating of ions downstream of the x-line during magnetic reconnection is explored using full-particle simulations, test particle simulations, and analytic analysis. Large-scale particle simulations reveal that the ion temperature increases sharply across the boundary layer that separates the upstream plasma from the Alfvénic outflow. This boun…