809 research outputs found

    Multiple Images of a Highly Magnified Supernova Formed by an Early-Type Cluster Galaxy Lens

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    In 1964, Refsdal hypothesized that a supernova whose light traversed multiple paths around a strong gravitational lens could be used to measure the rate of cosmic expansion. We report the discovery of such a system. In Hubble Space Telescope imaging, we have found four images of a single supernova forming an Einstein cross configuration around a redshift z=0.54 elliptical galaxy in the MACS J1149.6+2223 cluster. The cluster's gravitational potential also creates multiple images of the z=1.49 spiral supernova host galaxy, and a future appearance of the supernova elsewhere in the cluster field is expected. The magnifications and staggered arrivals of the supernova images probe the cosmic expansion rate, as well as the distribution of matter in the galaxy and cluster lenses.Comment: Published in the 6 March 2015 issue of Science; 17 pages, 7 figures, and 3 tables including Supplementary Material

    GOALS-JWST: Small neutral grains and enhanced 3.3 micron PAH emission in the Seyfert galaxy NGC 7469

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    We present James Webb Space Telescope (JWST) Near Infrared Spectrograph (NIRSpec) integral-field spectroscopy of the nearby luminous infrared galaxy, NGC 7469. We take advantage of the high spatial/spectral resolution and wavelength coverage of JWST /NIRSpec to study the 3.3 um neutral polycyclic aromatic hydrocarbon (PAH) grain emission on ~60 pc scales. We find a clear change in the average grain properties between the star-forming ring and the central AGN. Regions in the vicinity of the AGN, with [NeIII]/[NeII]>0.25, tend to have larger grain sizes and lower aliphatic-to-aromatic (3.4/3.3) ratios indicating that smaller grains are preferentially removed by photo-destruction in the vicinity of the AGN. We find an overall suppression of the total PAH emission relative to the ionized gas in the central 1 kpc region of the AGN in NGC 7469 compared to what has been observed with Spitzer on 3 kpc scales. However, the fractional 3.3 um to total PAH power is enhanced in the starburst ring, possibly due to a variety of physical effects on sub-kpc scales, including recurrent fluorescence of small grains or multiple photon absorption by large grains. Finally, the IFU data show that while the 3.3 um PAH-derived star formation rate (SFR) in the ring is 8% higher than that inferred from the [NeII] and [NeIII] emission lines, the integrated SFR derived from the 3.3 um feature would be underestimated by a factor of two due to the deficit of PAHs around the AGN, as might occur if a composite system like NGC 7469 were to be observed at high-redshift.Comment: 14 pages, 5 figures, 2 tables, Submitted to ApJ

    A Novel Molecular Solution for Ultraviolet Light Detection in Caenorhabditis elegans

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    For many organisms the ability to transduce light into cellular signals is crucial for survival. Light stimulates DNA repair and metabolism changes in bacteria, avoidance responses in single-cell organisms, attraction responses in plants, and both visual and nonvisual perception in animals. Despite these widely differing responses, in all of nature there are only six known families of proteins that can transduce light. Although the roundworm Caenorhabditis elegans has none of the known light transduction systems, we show here that C. elegans strongly accelerates its locomotion in response to blue or shorter wavelengths of light, with maximal responsiveness to ultraviolet light. Our data suggest that C. elegans uses this light response to escape the lethal doses of sunlight that permeate its habitat. Short-wavelength light drives locomotion by bypassing two critical signals, cyclic adenosine monophosphate (cAMP) and diacylglycerol (DAG), that neurons use to shape and control behaviors. C. elegans mutants lacking these signals are paralyzed and unresponsive to harsh physical stimuli in ambient light, but short-wavelength light rapidly rescues their paralysis and restores normal levels of coordinated locomotion. This light response is mediated by LITE-1, a novel ultraviolet light receptor that acts in neurons and is a member of the invertebrate Gustatory receptor (Gr) family. Heterologous expression of the receptor in muscle cells is sufficient to confer light responsiveness on cells that are normally unresponsive to light. Our results reveal a novel molecular solution for ultraviolet light detection and an unusual sensory modality in C. elegans that is unlike any previously described light response in any organism

    The Lantern, 2015-2016

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    • Ghosts • Going to China • 98% Guaranteed • Constellation/Boulevard • Prayer • The Little One • Burning • The Amber Macaroon • Becoming • Requiem • Construction Site • Thirteen Ways of Looking at a Dragon • Charlie • No Sleep • A Lesson in Physical Education • Statues • Who Can Love a Black Woman? • Apples • Fun Craft • The Door at Midnight • Eve as a Book in the Bible • Boys • Diamond Heart • To Apollo • Joanne and Her July Garden • Option A, 1936 • Young White Girls, Hollow Bodies, and Home • Mama\u27s Stance on Sugar • The Mariana Trench • Hurricane • Part of the Job • Avenue H Blues • Hour of Nones • Send Toilet Paper • Grave Robbing • Wild Turkey • The Creek • Let\u27s Go for a Walk • Deaconess • Border of Love • Your Father, Rumpelstiltskin • Purchasing Poplars • Red Tatters • Sunken • Whispers • Existence • God Took a Cigarette Break with Police Officers • Martian Standoff • In the Headlights • It\u27s a Subtle Thing • Dear Kent • Hanako-san • A Brief Interlude • On Fencing, Gummy Worms, and my Inescapable Fear of Living in the Moment • Stolen Soul • Block • Mortem Mei Fratris • Kalki • Lake Placid • Atom and Eve • The Baerie Queene • Gladston • Soldiers at Gettysburg • Pattern • Foliage • Mass Media • Arrow • Move Out • Wanderers • Riverside Gardenhttps://digitalcommons.ursinus.edu/lantern/1182/thumbnail.jp

    The Armed Forces

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