Search Publications
The Formation of IRIS Diagnostics. IV. The Mg II Triplet Lines as a New Diagnostic for Lower Chromospheric Heating
De Pontieu, Bart; Hansteen, Viggo; Carlsson, Mats +1 more
A triplet of subordinate lines of Mg ii exists in the region around the h&k lines. In solar spectra these lines are seen mostly in absorption, but in some cases can become emission lines. The aim of this work is to study the formation of this triplet, and investigate any diagnostic value they can bring. Using 3D radiative magnetohydrodynamic s…
CHAOS II. Gas-phase Abundances in NGC 5194
Skillman, Evan D.; Moustakas, John; Croxall, Kevin V. +2 more
We have observed NGC 5194 (M51a) as part of the CHemical Abundances of Spirals project. Using the Multi Object Double Spectrographs on the Large Binocular Telescope we are able to measure one or more of the temperature-sensitive auroral lines ([O iii] λ4363, [N ii] λ5755, [S iii] λ6312) and thus measure “direct” gas-phase abundances in 29 individu…
A Higher Efficiency of Converting Gas to Stars Pushes Galaxies at z ∼ 1.6 Well Above the Star-forming Main Sequence
Berta, S.; Lutz, D.; Daddi, E. +18 more
Local starbursts have a higher efficiency of converting gas into stars, as compared to typical star-forming galaxies at a given stellar mass, possibly indicative of different modes of star formation. With the peak epoch of galaxy formation occurring at z > 1, it remains to be established whether such an efficient mode of star formation is occur…
UV Surface Environment of Earth-like Planets Orbiting FGKM Stars through Geological Evolution
Kaltenegger, L.; Sasselov, D.; Rugheimer, S. +1 more
The UV environment of a host star affects the photochemistry in the atmosphere, and ultimately the surface UV environment for terrestrial planets and therefore the conditions for the origin and evolution of life. We model the surface UV radiation environment for Earth-sized planets orbiting FGKM stars in the circumstellar Habitable Zone for Earth …
Warmer Local Interstellar Medium: A Possible Resolution of the Ulysses-IBEX Enigma
McComas, D. J.; Fuselier, S. A.; Kucharek, H. +9 more
Interstellar Boundary Explorer (IBEX) measurements from 2009-2010 identified a set of possible solutions with very tight coupling between the interstellar He inflow longitude, latitude, speed, and temperature. The center of this allowable parameter space suggested that the heliosphere could be moving more slowly and in a slightly different directi…
The Event Horizon of M87
Perlman, Eric S.; Kormendy, John; Rieke, Marcia J. +3 more
The 6× {{10}9} {{M}⊙ } supermassive black hole at the center of the giant elliptical galaxy M87 powers a relativistic jet. Observations at millimeter wavelengths with the Event Horizon Telescope have localized the emission from the base of this jet to angular scales comparable to the putative black hole horizon. The jet might…
Indirect Evidence for Escaping Ionizing Photons in Local Lyman Break Galaxy Analogs
Heckman, Timothy M.; Leitherer, Claus; Alexandroff, Rachael M. +2 more
A population of early star-forming galaxies is the leading candidate for the re-ionization of the universe. It is still unclear, however, what conditions and physical processes would enable a significant fraction of the ionizing (Lyman continuum) photons to escape from these gas-rich galaxies. In this paper we present the results of the analysis o…
The Panchromatic Hubble Andromeda Treasury. VIII. A Wide-area, High-resolution Map of Dust Extinction in M31
Bell, Eric F.; Gouliermis, Dimitrios A.; Skillman, Evan D. +15 more
We map the distribution of dust in M31 at 25 pc resolution using stellar photometry from the Panchromatic Hubble Andromeda Treasury survey. The map is derived with a new technique that models the near-infrared color-magnitude diagram (CMD) of red giant branch (RGB) stars. The model CMDs combine an unreddened foreground of RGB stars with a reddened…
The Cause of the Weak Solar Cycle 24
Schüssler, M.; Jiang, J.; Cameron, R. H.
The ongoing 11 year cycle of solar activity is considerably less vigorous than the three cycles before. It was preceded by a very deep activity minimum with a low polar magnetic flux, the source of the toroidal field responsible for solar magnetic activity in the subsequent cycle. Simulation of the evolution of the solar surface field shows that t…
The Atacama Cosmology Telescope: Lensing of CMB Temperature and Polarization Derived from Cosmic Infrared Background Cross-correlation
Hilton, Matt; Hasselfield, Matthew; Bond, J. Richard +49 more
We present a measurement of the gravitational lensing of the Cosmic Microwave Background (CMB) temperature and polarization fields obtained by cross-correlating the reconstructed convergence signal from the first season of Atacama Cosmology Telescope Polarimeter data at 146 GHz with Cosmic Infrared Background (CIB) fluctuations measured using the …