Time filter

Source Type

Nierenberg A.M.,University of California at Santa Barbara | Treu T.,University of California at Santa Barbara | Wright S.A.,Dunlap Institute for Astronomy and Astrophysics | Fassnacht C.D.,University of California at Davis | Auger M.W.,University of Cambridge
Monthly Notices of the Royal Astronomical Society | Year: 2014

Strong gravitational lenses can be used to detect low-mass subhaloes, based on deviations in image fluxes and positions from what can be achieved with a smooth mass distribution. So far, this method has been limited by the small number of (radio-loud, microlensing-free) systems which can be analysed for the presence of substructure. Using the gravitational lens B1422+231, we demonstrate that adaptive optics integral field spectroscopy can also be used to detect dark substructures. We analyse data obtained with OH Suppressing Infra-Red Imaging Spectrograph on the Keck I Telescope, using a Bayesian method that accounts for uncertainties relating to the point spread function and image positions in the separate exposures. The narrow-line [OIII] fluxes measured for the lensed images are consistent with those measured in the radio, and show a significant deviation from what would be expected in a smooth mass distribution, consistent with the presence of a perturbing low-mass halo. Detailed lens modelling shows that image fluxes and positions are fitted significantly better when the lens is modelled as a system containing a single perturbing subhalo in addition to the main halo, rather than by the main halo on its own, indicating the significant detection of substructure. The inferred mass of the subhalo depends on the subhalo mass density profile: the 68 per cent confidence intervals for the perturber mass within 600 pc are 8.2+0.6 -0.8, 8.2+0.6 -1 and 7.6 ± 0.3log10[Msub/M(], respectively, for a singular isothermal sphere, a pseudo-Jaffe and a Navarro-Frenk-White mass profile. This method can extend the study of flux ratio anomalies to virtually all quadruply imaged quasars, and therefore offers great potential to improve the determination of the subhalo mass function in the near future.© 2014 The Authors.

Reddy N.A.,National Optical Astronomy Observatory | Reddy N.A.,University of California at Riverside | Pettini M.,Institute of Astronomy | Pettini M.,University of Western Australia | And 4 more authors.
Astrophysical Journal | Year: 2012

A large sample of spectroscopically confirmed star-forming galaxies at redshifts 1.4 ≤ z spec ≤ 3.7, with complementary imaging in the near- and mid-IR from the ground and from the Hubble Space Telescope and Spitzer Space Telescope, is used to infer the average star formation histories (SFHs) of typical galaxies from z ∼ 2 to 7. For a subset of 302 galaxies at 1.5 ≤ z spec < 2.6, we perform a detailed comparison of star formation rates (SFRs) determined from spectral energy distribution (SED) modeling (SFRs[SED]) and those calculated from deep Keck UV and Spitzer/MIPS 24 μm imaging (SFRs[IR+UV]). Exponentially declining SFHs yield SFRs[SED] that are 5-10 times lower on average than SFRs[IR+UV], indicating that declining SFHs may not be accurate for typical galaxies at z ≳ 2. The SFRs of z ∼ 2-3 galaxies are directly proportional to their stellar masses (M *), with unity slope - a result that is confirmed with Spitzer/IRAC stacks of 1179 UV-faint (R ≥ 25.5) galaxies - for M * ≳ 5 × 108 M⊙ and SFRs ≳ 2 M⊙yr-1. We interpret this result in the context of several systematic biases that can affect determinations of the SFR-M * relation. The average specific SFRs at z ∼ 2-3 are remarkably similar within a factor of two to those measured at z ≳ 4, implying that the average SFH is one where SFRs increase with time. A consequence of these rising SFHs is that (1) a substantial fraction of UV-bright z ∼ 2-3 galaxies had faint sub-L* progenitors at z ≳ 4; and (2) gas masses must increase with time from z = 2 to 7, over which time the net cold gas accretion rate - as inferred from the specific SFR and the Kennicutt-Schmidt relation - is ∼2-3 times larger than the SFR. However, if we evolve to higher redshift the SFHs and masses of the halos that are expected to host L* galaxies at z ∼ 2, then we find that ≲ 10% of the baryons accreted onto typical halos at z ≳ 4 actually contribute to star formation at those epochs. These results highlight the relative inefficiency of star formation even at early cosmic times when galaxies were first assembling. © 2012. The American Astronomical Society. All rights reserved.

Sand D.J.,Las Cumbres Observatory Global Telescope Network | Sand D.J.,University of California at Santa Barbara | Graham M.L.,Las Cumbres Observatory Global Telescope Network | Graham M.L.,University of California at Santa Barbara | And 9 more authors.
Astrophysical Journal | Year: 2012

We describe the Multi-Epoch Nearby Cluster Survey, designed to measure the cluster Type Ia supernova (SN Ia) rate in a sample of 57 X-ray selected galaxy clusters, with redshifts of 0.05 < z < 0.15. Utilizing our real-time analysis pipeline, we spectroscopically confirmed twenty-three cluster SNe Ia, four of which were intracluster events. Using our deep Canada-France-Hawaii Telescope/MegaCam imaging, we measured total stellar luminosities in each of our galaxy clusters, and we performed detailed supernova (SN) detection efficiency simulations. Bringing these ingredients together, we measure an overall cluster SN Ia rate within R200 (1Mpc) of 0.042+0.012 -0.010 +0.010-0.008 SNuM (0.049 +0.016-0.014 +0.005-0.004 SNuM) and an SN Ia rate within red-sequence galaxies of 0.041+0.015 -0.015 +0.005-0.010 SNuM (0.041 +0.019-0.015 +0.005-0.004 SNuM). The red-sequence SN Ia rate is consistent with published rates in early-type/elliptical galaxies in the "field." Using our red-sequence SN Ia rate, and other cluster SN measurements in early-type galaxies up to z 1, we derive the late-time (>2Gyr) delay time distribution (DTD) of SN Ia assuming a cluster early-type galaxy star formation epoch of zf = 3. Assuming a power-law form for the DTD, Ψ(t)ts , we find s = -1.62 0.54. This result is consistent with predictions for the double degenerate SN Ia progenitor scenario (s ∼ -1) and is also in line with recent calculations for the double detonation explosion mechanism (s ∼ -2). The most recent calculations of the single degenerate scenario DTD predicts an order-of-magnitude drop-off in SN Ia rate ∼6-7Gyr after stellar formation, and the observed cluster rates cannot rule this out. © 2012 The American Astronomical Society. All rights reserved.

Graham M.L.,Las Cumbres Observatory Global Telescope Network | Graham M.L.,University of California at Santa Barbara | Sand D.J.,Las Cumbres Observatory Global Telescope Network | Sand D.J.,University of California at Santa Barbara | And 8 more authors.
Astrophysical Journal | Year: 2012

We present seven spectroscopically confirmed Type II cluster supernovae (SNeII) discovered in the Multi-Epoch Nearby Cluster Survey, a supernova survey targeting 57 low-redshift 0.05 < z < 0.15 galaxy clusters with the Canada-France-Hawaii Telescope. We find the rate of Type II supernovae within R 200 of z 0.1 galaxy clusters to be 0.026+0.085 - 0.018(stat)+0.003 - 0.001(sys) SNuM. Surprisingly, one SNII is in a red-sequence host galaxy that shows no clear evidence of recent star formation (SF). This is unambiguous evidence in support of ongoing, low-level SF in at least some cluster elliptical galaxies, and illustrates that galaxies that appear to be quiescent cannot be assumed to host only Type Ia SNe. Based on this single SNII we make the first measurement of the SNII rate in red-sequence galaxies, and find it to be 0.007+0.014 - 0.007(stat)+0.009 - 0.001(sys) SNuM. We also make the first derivation of cluster specific star formation rates (sSFR) from cluster SNII rates. We find that for all galaxy types the sSFR is 5.1 +15.8 - 3.1(stat) ± 0.9(sys) M o yr -1 (1012 M o)-1, and for red-sequence galaxies only it is 2.0+4.2 - 0.9(stat) ± 0.4(sys) M o yr-1 (1012 M o)-1. These values agree with SFRs measured from infrared and ultraviolet photometry, and Hα emission from optical spectroscopy. Additionally, we use the SFR derived from our SNII rate to show that although a small fraction of cluster Type Ia SNe may originate in the young stellar population and experience a short delay time, these results do not preclude the use of cluster SNIa rates to derive the late-time delay time distribution for SNeIa. © © 2012. The American Astronomical Society. All rights reserved.

Medling A.M.,Australia National University | Vivian U.,University of California at Riverside | Max C.E.,University of California at Santa Cruz | Sanders D.B.,University of Hawaii at Manoa | And 6 more authors.
Astrophysical Journal | Year: 2015

We present black hole mass measurements from kinematic modeling of high-spatial resolution integral field spectroscopy of the inner regions of nine nearby (ultra-)luminous infrared galaxies in a variety of merger stages. These observations were taken with OSIRIS and laser guide star adaptive optics on the Keck I and Keck II telescopes, and reveal gas and stellar kinematics inside the spheres of influence of these supermassive black holes. We find that this sample of black holes are overmassive (∼107-9m⊙) compared to the expected values based on black hole scaling relations, and suggest that the major epoch of black hole growth occurs in early stages of a merger, as opposed to during a final episode of quasar-mode feedback. The black hole masses presented are the dynamical masses enclosed in ∼25 pc, and could include gas which is gravitationally bound to the black hole but has not yet lost sufficient angular momentum to be accreted. If present, this gas could in principle eventually fuel active galactic nucleus feedback or be itself blown out from the system. © 2015. The American Astronomical Society. All rights reserved.

News Article | April 11, 2016
Site: www.nrl.navy.mil

Imagine taking the world's most powerful radio telescope, used by scientists around the globe, and piping a nearly continuous data stream into your research laboratory. That is exactly what scientists at the Naval Research Laboratory (NRL) in Washington, D.C. have done in collaboration with the National Radio Astronomy Observatory's Karl G. Jansky Very Large Array (NRAO VLA). The newly-completed VLA Low Band Ionospheric and Transient Experiment (VLITE for short) has been built to piggyback on the $300 million dollar infrastructure of the VLA. The primary scientific driver for VLITE is real-time monitoring of ionospheric weather conditions over the U.S. southwest. NRL ionospheric lead scientist Dr. Joseph Helmboldt says "This new system allows for continuous specification of ionospheric disturbances with remarkable precision. VLITE can detect and characterize density fluctuations as small as 30 parts per million within the total electron content along the line of sight to a cosmic source. This is akin to being at the bottom of Lake Superior and watching waves as small as 1-cm in height pass overhead. This will have a substantial impact on our understanding of ionospheric dynamics, especially the coupling between fine-scale irregularities within the lower ionosphere and larger disturbances higher up." Ionospheric disturbances represent one of the most significant limitations to the performance of many radio-frequency applications like satellite-based communication and navigation (including the GPS in your phone) as well as ground-based, over-the-horizon systems (think ham radio or AM radio). While the fine-scale irregularities that VLITE is especially sensitive to aren't large enough to make your smart phone think you are at your neighbor's house when you're really at home, they are quite problematic for vital remote sensing surveillance systems like over-the-horizon radar. The additional insights provided by VLITE into the nature of these ionospheric ripples will help us to better understand how to cope with their effects on such systems. "VLITE is also a powerful new tool in our arsenal for astrophysical research" says VLITE principle investigator Dr. Namir Kassim. He points out that "We know the Universe has many secrets including mysterious blips (so-called transients) that appear and vanish like fireflies in the night. Limited observing time at classical observatories hampers our ability to understand these intriguing objects. The power of VLITE is the nearly continual data stream over a large region of the sky. This opens up a new window on the transient Universe." At any given time, the region of the sky that VLITE peers at is so large that nearly 20 full moons would fit inside it. Astrophysics lead scientist Dr. Tracy Clarke of NRL describes VLITE as "a symbiotic instrument that piggybacks on world-class science at the VLA. It operates as a stand-alone tool for ionospheric and astrophysical studies while at the same time VLITE provides the opportunity for enhanced science in the research program running on the VLA." VLITE operations started with first light on July 17, 2014 but the real fun began two days before Thanksgiving, on November 25, 2014, when VLITE moved from a commissioning phase into full scientific operations. The system operates in real-time on 10 VLA antennas and provides 64 MHz of bandwidth centered on 352 MHz with a temporal resolution of 2s and a spectral resolution of 100 kHz. This powerful new instrument operates in parallel with the VLA and is essentially 'driven' around the sky by the primary science observer. Data streams off the telescope through dedicated systems that bypass normal VLA operations. The data then take two roads, one through real-time processing on computers located at the VLA site, and the other through off-line processing at NRL's facility in Washington. Due to the large volume of nearly continuous incoming data, all data must be analyzed by an automated pipeline that was custom designed for VLITE. Pipeline designer Dr. Wendy Lane Peters of NRL describes this process as being like "sitting in the passenger seat of a Google car and not knowing where it is taking you. VLITE is along for the ride wherever the primary science program takes us. We have to anticipate what they might do so that our pipeline is smart enough to understand the incoming data." Professor Bryan Gaensler, Director of the Dunlap Institute for Astronomy and Astrophysics at the University of Toronto, says that this is going to become the new way of doing astronomy. "It's a tragedy and a travesty that most of the information our telescopes gather from the sky is ignored and discarded. VLITE is part of a new generation of experiments that fully utilize the massive data torrents collected by the world's most powerful observatories." Over the first two months of science operations, VLITE has recorded observations of sources ranging from the Sun, nearby stars and galaxies, to some of the most distant sources in the Universe. NRL astronomers and their colleagues have been poring over the pipeline images, improving their analysis pipeline and exploring the scientific potential of the instrument. About the U.S. Naval Research Laboratory The U.S. Naval Research Laboratory provides the advanced scientific capabilities required to bolster our country's position of global naval leadership. The Laboratory, with a total complement of approximately 2,500 personnel, is located in southwest Washington, D.C., with other major sites at the Stennis Space Center, Miss., and Monterey, Calif. NRL has served the Navy and the nation for over 90 years and continues to advance research further than you can imagine. For more information, visit the NRL website or join the conversation on Twitter, Facebook, and YouTube.

News Article | January 4, 2016
Site: www.scientificcomputing.com

Tales of strange alien worlds, fantastic future technologies and bowls of sentient petunias have long captivated audiences worldwide. But science fiction is more than just fantasy in space; it can educate, inspire and expand our imaginations to conceive of the universe as it might be. We invited scientists to highlight their favorite science fiction novel or film and tell us what it was that captivated their imagination — and, for some, how it started their career. Long before the era of hard science fiction, Robert Heinlein took Einstein’s special theory of relativity and turned it into a masterpiece of young adult fiction. In Time for the Stars, Earth explores the Galaxy via a fleet of “torch ships,” spacecraft that travel at a significant fraction of the speed of light. Communication with the fleet is handled by pairs of telepathic twins, one of whom stays on Earth while the other journeys forth. The supposed simultaneity of telepathy overcomes the massive time delays that would otherwise occur over the immense distances of space. The catch is that at the tremendous speeds of these torch ships, time travels much slower than back on Earth. The story focuses on Tom, the space traveler, and his twin brother Pat, who remains behind. The years and decades sweep by for Pat, in a journey that takes mere months for Tom. Pat’s telepathic voice accelerates to a shrill accelerated squeal for Tom, as Einstein’s time dilation drives them apart, both metaphorically and physically. This is ultimately a breezy kids’ adventure novel, but it had a massive influence on me. Modern physics wasn’t abstruse. It was measurable, and it had consequences. I was hooked. And I’ve never let go. Stanley Kubrick’s 2001: A Space Odyssey encompasses human evolution, space, alien life and artificial intelligence. Despite being released the year before Apollo 11, the Academy Award winning special effects still make its vision of space inspiring. It can be spine tingling when seen at an old fashioned cinema with a wide screen and a 70mm print (such as Melbourne’s Astor). 2001 is also a product of its time. During the 1960s NASA consumed roughly four percent of the US federal budget, and if that had continued, then perhaps the International Space Station would be a giant rotating behemoth seen in 2001. Indeed 2001’s Pan Am spaceplane seems like a natural progression from early (ambitious) proposals for the Space Shuttle. Technologies in the film are ahead and behind what we have today. The most memorable (and arguably emotional) character of 2001 is HAL, an eerily intelligent computer that is far in advance of any computer in existence. And yet astronauts on the moon are using photographic film, rather than digital cameras. Kubrick deliberately made some space travel seem routine, so his space travelers are frozen in 1960s norms. The astronauts are mostly white men, with women mostly relegated to roles such as flight attendants (an exception is a Soviet scientist). Fortunately, in this regard, the 21st century is more advanced than 2001’s imagined future. The first book of the classic “Space Trilogy” was written 20 years before the launch of Sputnik 1 in 1957, the first “world-circling spaceship”. C. S. Lewis was no scientist — he was a professor of Medieval and Renaissance literature — but his deep knowledge of pre-modern cosmology gives his take on space travel a unique flavor. I find myself returning to Out of the Silent Planet and its sequel, Voyage to Venus, over and over again. In the story, Lewis' hero, Ransom, becomes a reluctant astronaut when kidnapped by the uber-colonial “hard” scientist Weston for a journey to Mars. Confined in the spherical spaceship, he becomes aware of a constant faint tinkling noise. In the world before space junk, it is a fine rain of micrometeoroids striking the aluminium shell. Ransom’s “dismal fancy of the black, cold vacuity, the utter deadness, which was supposed to separate the worlds” fostered by modern science, is transformed by the experience of actually being in space. His revelation is an intimately joyous recognition that space, far from being dead, is an “empyrean ocean of radiance,” whose “blazing and innumerable offspring” look down upon the Earth. He feels “life pouring into him from it every moment. How indeed should it be otherwise, since out of this ocean all the worlds and all their life had come?” How, indeed, could we not long for space after such a vision as this? Not just life on another planet… It was Larry Niven’s Ringworld that led, in part, to my career in astrophysics. Ringworld describes the exploration of an alien megastructure of unknown origin, discovered around a distant star. The artificial world is literally in the shape of a ring, with a radius corresponding to the distance of the Earth to the sun; mountainous walls on each side hold in the atmosphere, and the surface is decorated with a wide variety of alien plants and animals. The hero gets to the Ringworld via a mildly faster-than-light drive purchased at astronomical cost from an alien trading species, and makes use of teleportation disks and automated medical equipment. The appeal of high-technology stories like this are obvious: many contemporary problems, like personal transportation, overpopulation, disease, and death have all been solved by advanced technology; while of course, new and interesting problems have arisen. Grand in scope, and featuring some truly bold ideas, Ringworld (and Niven’s other books set in “Known Space”) are as keen now as when they were written, 40 years ago. Whether you have heard the radio play, read the book or seen the film, this story of a hapless Englishman negotiating his way through the galaxy is an essential piece of nerd culture. I first heard the play as a teenager, and even now not many weeks go by without me delving into sections of this trilogy of five-parts. As a scientist, my life can seem a little zany to an outsider. When your job does sometimes actually entail reversing the polarity of a neutron flow, you need to look to an even crazier fiction world for your escapism. And for me this book is it. A world where sperm whales and bowls of petunias can appear in space for no reason at all and staggering co-incidences happen every time you power up your spaceship. Life among the stars is rather more ordinary than it might seem. BBC The genius (and I do not use that word lightly) of Douglas Adams’ writing is that the loopy concepts of the book are presented with a thin veneer of “scienceness”, enough to make the fantastical concepts that little more believable. Then he “normalises” it all. A packet of peanuts will help you survive a matter transference beam, for instance. The heart of this book is its characters, a suite of people/aliens that are echoed in every workplace (certainly every laboratory) across the world. Walk into any science institute and there will be a two-headed power-hungry presidential leader railing upon post-docs, with brains the size of planets, who really wish you hadn’t talked to them about life. I get the impression that Douglas Adams would not have wanted you to take anything away from this book. But, for me it gives continued inspiration that there is always another way to sidle up to a problem. Most of all though: don’t panic. What might a post-scarcity society look like? I love a lot of science fiction, but Iain M. Banks’ classic space-opera Consider Phlebas is a special favorite. Banks describes the “Culture”, a diverse, anarchic, utopian and galaxy-spanning post-scarcity society. The Culture is a hybrid of enhanced and altered humanoids and artificial intelligences, which range from rather dull to almost godlike in their capabilities. Most people in the Culture lead a relaxed, hedonistic lifestyle, going to parties, doing art, taking drugs (which they can synthesize from bio-engineered glands) and generally having fun. The tedious business of actually running the whole show is mostly left up to the most powerful AIs, called Minds, who manifest themselves in the great star-ships and orbitals in which most citizens live. Of course, it’s a big galaxy, and not everyone shares the Culture’s easy-going approach to galactic citizenship. Consider Phlebas is set against the backdrop of a growing conflict between the Culture and the Indirans, a speciesist, religious and hierarchical empire with expansion on its mind. Perhaps the best thing about Consider Phlebas (apart from the wonderfully irreverent ship names the Minds give themselves) is the fact that a story from this conflict is told from the perspective of an Indiran agent, who despises the Culture and everything it stands for. My own take on the book is as an ode to progressive technological humanism, and the astute reader will find many parallels to contemporary political and cultural issues. Truman Burbank, played with a delectable balance of animation and pathos by Jim Carrey, lives a confected life as unwitting protagonist in a reality television show. Conceived on camera, adopted by a corporation and manipulated at every stage by the show’s sinister creative genius, Christof (Ed Harris), Truman nonetheless comes to realize that his world is a sham and that almost every interaction he ever had was a lie. Against the backdrop of Seahaven’s dystopic perfection, Weir exposes prescient glimpses of reality television, surveillance culture and the stalkerish targeted advertising we now find in our social media streams. It’s like a peppy 1984 but with corporate hegemony replacing the totalitarian state. But I was most gripped by the fresh take on ancient debates about rationalist nature and empiricist nurture. As a student of behavior, I’ve always rued the amputation of biology from the social sciences, particularly the wasted opportunity that saw sociobiology turned into a perjorative in the late 1970s, at least outside the study of insect sociality. The rejection of evolutionary thinking as “biological determinism”, and its positioning as opposite to progress and liberation, has always rankled me. I recall watching the film alone, between conferences, at an ancient cinema in Santa Cruz. What excited me most, and kept me up much of the night scribbling notes that would eventually shape my research direction and lead me to popular writing, was Weir’s clever inversion of the relationships between nature/nurture and determinism/free will. While Cristof’s nurture tramples Truman’s nature throughout the film, in the end something inherent to Truman sets him free, as he whispers: “You never had a camera in my head!”. The climax of The Truman Show. “Good afternoon, good evening and goodnight!” In the decade before Albert Einstein told us that time and space were malleable, H. G. Wells gave us the adventures of the Time Traveller. We never learn the name of this Victorian scientist, a man who explains “there is no difference between time and any of the three dimensions of space” and builds a machine to explore this new world. It was not from Einstein that I discovered the non-absolute nature of space and time, but from the Time Traveller, and his present-day incarnation, Doctor Who. A view of the distant future from the recent past. The Traveller doesn’t head to past, to be a voyeur at historical events, but into the unknown future. And the future of Wells is not glorious! The Traveller finds evolution has split humans in two, with delicate Eloi being little more than food for the subterranean Morlocks. Escaping mayhem and heading even further into the future, the Traveller finds the life’s last gasp under a swollen, red sun, eventually seeing the Earth succumbs to final freezing, before he returns to the relative safety of Victorian London. This scientific vision of the future struck me, and the nature of time has remained in my mind. At the end of the story the Traveller heads back to continue his exploration of the future; playing with the equations of relativity is likely to be the closest I will ever come to realizing this dream. Michael J. I. Brown, Associate professor, Monash University; Alice Gorman, Senior Lecturer in archaeology and space studies, Flinders University; Bryan Gaensler, Director, Dunlap Institute for Astronomy and Astrophysics, University of Toronto; Duncan Galloway, PhD; Senior Lecturer in Astrophysics, Monash University; Geraint Lewis, Professor of Astrophysics, University of Sydney; Helen Maynard-Casely, Instrument Scientist, Australian Nuclear Science and Technology Organisation; Matthew Browne, Senior Lecturer in Statistics, CQUniversity Australia, and Rob Brooks, Scientia Professor of Evolutionary Ecology; Director, Evolution & Ecology Research Centre, UNSW Australia. This article was originally published on The Conversation. Read the original article.

Iserlohe C.,University of Cologne | Krabbe A.,University of Stuttgart | Larkin J.E.,University of California at Los Angeles | Barczys M.,University of Rochester | And 4 more authors.
Astronomy and Astrophysics | Year: 2013

We present H- and K-band data from the inner arcsecond of the Seyfert 1.5 galaxy NGC 4151 obtained with the adaptive-optics-assisted near-infrared-imaging field spectrograph OSIRIS at the Keck Observatory. The angular resolution is about a few parsecs on-site and thus competes easily with optical images taken previously with the Hubble Space Telescope. We present the morphology and dynamics of most species detected but focus on the morphology and dynamics of the narrow line region (as traced by emission of [FeII]λ1.644 μm), the interplay between plasma ejected from the nucleus (as traced by 21 cm continuum radio data) and hot H2 gas and characterize the detected nuclear HeIλ2.058 μm absorption feature as a narrow absorption line (NAL) phenomenon. The emission from the narrow line region (NLR) as traced by [FeII] reveals a biconical morphology and we compare the measured dynamics in the [FeII] emission line with models that propose acceleration of gas in the NLR and simple ejection of gas into the NLR. In the inner 2.5 arcsec the acceleration model reveals a better fit to our data than the ejection model. We also see evidence that the jet very locally enhances emission in [FeII] at certain positions in our field-of-view such that we were able to distinct the kinematics of these clouds from clouds generally accelerated in the NLR. Further, the radio jet is aligned with the bicone surface rather than the bicone axis such that we assume that the jet is not the dominant mechanism responsible for driving the kinematics of clouds in the NLR. The hot H2 gas is thermal with a temperature of about 1700 K. We observe a remarkable correlation between individual H2 clouds at systemic velocity with the 21 cm continuum radio jet. We propose that the radio jet is at least partially embedded in the galactic disk of NGC 4151 such that deviations from a linear radio structure are invoked by interactions of jet plasma with H2 clouds that are moving into the path of the jet because of rotation of the galactic disk of NGC 4151. Additionally, we observe a correlation of the jet as traced by the radio data, with gas as traced in Brγ and H2, at velocities between systemic and ±200 km s-1 at several locations along the path of the jet. The HeIλ2.058 μm line in NGC 4151 appears in emission with a blueshifted absorption component from an outflow. The emission (absorption) component has a velocity offset of 10 km s -1 (-280 km s-1) with a Gaussian (Lorentzian) full-width (half-width) at half maximum of 160 km s-1 (440 km s-1). The absorption component remains spatially unresolved and its kinematic measures differ from that of UV resonance absorption lines. From the amount of absorption we derive a lower limit of the HeI 21S column density of 1 × 1014 cm-2 with a covering factor along the line-of-sight of Clos â‰0.1. © ESO, 2013.

Chilcote J.K.,University of California at Los Angeles | Larkin J.E.,University of California at Los Angeles | Maire J.,Dunlap Institute for Astronomy and Astrophysics | Perrin M.D.,US Space Telescope Science Institute | And 7 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

We present performance results, from in-lab testing, of the Integral Field Spectrograph (IFS) for the Gemini Planet Imager (GPI). GPI is a facility class instrument for the Gemini Observatory with the primary goal of directly detecting young Jovian planets. The GPI IFS is based on concepts from the OSIRIS instrument at Keck and utilizes an infrared transmissive lenslet array to sample a rectangular 2.8 x 2.8 arcsecond field of view. The IFS provides low-resolution spectra across five bands between 1 and 2.5 μm. Alternatively, the dispersing element can be replaced with a Wollaston prism to provide broadband polarimetry across the same five filter bands. The IFS construction was based at the University of California, Los Angeles in collaboration with the Université de Montréal, Immervision and Lawrence Livermore National Laboratory. During its construction, we encountered an unusual noise source from microphonic pickup by the Hawaii-2RG detector. We describe this noise and how we eliminated it through vibration isolation. The IFS has passed its preship review and was shipped to University of California, Santa Cruz at the end of 2011 for integration with the remaining sub-systems of GPI. The IFS has been integrated with the rest of GPI and is delivering high quality spectral datacubes of GPI's coronagraphic field. © 2012 SPIE.

Mieda E.,University of Toronto | Mieda E.,Dunlap Institute for Astronomy and Astrophysics | Maire J.,Dunlap Institute for Astronomy and Astrophysics | Graham J.R.,University of California at Berkeley | And 3 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

We present the development of a portable SLODAR (SLOpe Detection and Ranging) instrument to measure the vertical atmosphere profile using several different telescopes (14", 16", and 20" aperture) and at varying worldwide sites. In particular, the portability and feasibility of this instrument motivated us to operate it at Ellesmere Island in the Canadian High Arctic. We discuss the SLODAR technique, the design of the instrument, and the results of the performance tests in the lab. The results of the Arctic site testing measurements in October and November 2012 are discussed by Maire et. al. (this conference).1. © 2014 SPIE.

Loading Dunlap Institute for Astronomy and Astrophysics collaborators
Loading Dunlap Institute for Astronomy and Astrophysics collaborators