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Stellar clusters in M83: formation, evolution, disruption and the influence of the environment
Bastian, N.; Larsen, S. S.; Smith, L. J. +6 more
We study the stellar cluster population in two adjacent fields in the nearby, face-on spiral galaxy M83 using multiwavelength Wide Field Camera 3/Hubble Space Telescope imaging. After automatic detection procedures, the clusters are selected through visual inspection to be centrally concentrated, symmetric, and resolved on the images, which allows…
Occurrence rate of earthward-propagating dipolarization fronts
André, M.; Vaivads, A.; Huang, S. Y. +2 more
The occurrence rate of earthward-propagating dipolarization fronts (DFs) is investigated in this paper based on the 9 years (2001-2009) of Cluster 1 data. For the first time, we select the DF events by fitting the characteristic increase in Bz using a hyperbolic tangent function. 303 earthward-propagating DFs are found; they have on ave…
Faint high-redshift AGN in the Chandra deep field south: the evolution of the AGN luminosity function and black hole demography
Pannella, M.; Fiore, F.; Castellano, M. +14 more
Context. We present detection and analysis of faint X-ray sources in the Chandra deep field south (CDFS) using the 4 Ms Chandra observation.
Aims: We place constraints on active galactic nuclei (AGN) luminosity functions at z = 3-7, its cosmological evolution, and high-redshift black hole and AGN demography.
Methods: We use a new detecti…
Investigations of dust heating in M81, M83 and NGC 2403 with the Herschel Space Observatory
Clements, D. L.; Roussel, H.; Cooray, A. +21 more
We use Spitzer Space Telescope and Herschel Space Observatory far-infrared data along with ground-based optical and near-infrared data to understand how dust heating in the nearby face-on spiral galaxies M81, M83 and NGC 2403 is affected by the starlight from all stars and by the radiation from star-forming regions. We find that 70/160 ?m surface …
Quantifying Spicules
De Pontieu, Bart; Carlsson, Mats; Pereira, Tiago M. D.
Understanding the dynamic solar chromosphere is fundamental in solar physics. Spicules are an important feature of the chromosphere, connecting the photosphere to the corona, potentially mediating the transfer of energy and mass. The aim of this work is to study the properties of spicules over different regions of the Sun. Our goal is to investiga…
Disentangling Baryons and Dark Matter in the Spiral Gravitational Lens B1933+503
McKean, J. P.; Treu, T.; Auger, M. W. +10 more
Measuring the relative mass contributions of luminous and dark matter in spiral galaxies is important for understanding their formation and evolution. The combination of a galaxy rotation curve and strong lensing is a powerful way to break the disk-halo degeneracy that is inherent in each of the methods individually. We present an analysis of the …
Neutral Interstellar Helium Parameters Based on IBEX-Lo Observations and Test Particle Calculations
Bochsler, P.; McComas, D. J.; Fuselier, S. A. +10 more
Because of its high ionization potential and weak interaction with hydrogen, neutral interstellar helium (NISHe) is almost unaffected at the heliospheric interface with the interstellar medium and freely enters the solar system. This second most abundant species provides some of the best information on the characteristics of the interstellar gas i…
The Large Longitudinal Spread of Solar Energetic Particles During the 17 January 2010 Solar Event
Gómez-Herrero, R.; Dresing, N.; Heber, B. +3 more
We investigate multi-spacecraft observations of the 17 January 2010 solar energetic particle event. Energetic electrons and protons have been observed over a remarkable large longitudinal range at the two STEREO spacecraft and SOHO, suggesting a longitudinal spread of nearly 360 degrees at 1 AU. The flaring active region, which was on the backside…
Dwarfs Gobbling Dwarfs: A Stellar Tidal Stream around NGC 4449 and Hierarchical Galaxy Formation on Small Scales
Carballo-Bello, Julio A.; Romanowsky, Aaron J.; Brodie, Jean P. +13 more
A candidate diffuse stellar substructure was previously reported in the halo of the nearby dwarf starburst galaxy NGC 4449 by Karachentsev et al. We map and analyze this feature using a unique combination of deep integrated-light images from the BlackBird 0.5 m telescope, and high-resolution wide-field images from the 8 m Subaru Telescope, which r…
Hubble Space Telescope Reveals Multiple Sub-giant Branch in Eight Globular Clusters
Anderson, J.; Milone, A. P.; Marino, A. F. +6 more
In the last few years many globular clusters (GCs) have revealed complex color-magnitude diagrams, with the presence of multiple main sequences (MSs), broad or multiple sub-giant branches (SGBs) and MS turnoffs, and broad or split red giant branches (RGBs). After a careful correction for differential reddening, high-accuracy photometry with the Hu…