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Full-Text Articles in Physical Sciences and Mathematics

Using Coherent Phonons For Ultrafast Control Of The Dirac Node Of Srmnsb2, Christopher P. Weber, Madison G. Masten, Thomas C. Ogloza, Bryan S. Berggren, Michael K. L. Man, Keshav M. Dani, Jinyu Liu, Zhiqiang Mao, Dennis D. Klug, Adebayo A. Adeleke, Yansun Yao Oct 2018

Using Coherent Phonons For Ultrafast Control Of The Dirac Node Of Srmnsb2, Christopher P. Weber, Madison G. Masten, Thomas C. Ogloza, Bryan S. Berggren, Michael K. L. Man, Keshav M. Dani, Jinyu Liu, Zhiqiang Mao, Dennis D. Klug, Adebayo A. Adeleke, Yansun Yao

Physics

SrMnSb2 is a candidate Dirac semimetal whose electrons near the Y point have the linear dispersion and low mass of a Dirac cone. Here we demonstrate that ultrafast, 800-nm optical pulses can launch coherent phonon oscillations in Sr0.94Mn0.92Sb2, particularly an Ag mode at 4.4 THz. Through first-principles calculations of the electronic and phononic structure of SrMnSb2, we show that high-amplitude oscillations of this mode would displace the atoms in a way that transiently opens and closes a gap at the node of the Dirac cone. The ability to control ...


Excess Electron Screening Of Remote Donors And Mobility In Modern Gaas/Algaas Heterostructures, M. Sammon, Tianran Chen, B. I. Shklovskii Oct 2018

Excess Electron Screening Of Remote Donors And Mobility In Modern Gaas/Algaas Heterostructures, M. Sammon, Tianran Chen, B. I. Shklovskii

Physics

In modern GaAs/AlxGa1−xAs heterostructures with record high mobilities, a two-dimensional electron gas (2DEG) in a quantum well is provided by two remote donor δ-layers placed on both sides of the well. Each δ-layer is located within a narrow GaAs layer, flanked by narrow AlAs layers which capture excess electrons from donors but leave each of them localized in a compact dipole atom with a donor. Still excess electrons can hop between host donors to minimize their Coulomb energy. As a result they screen the random potential of donors dramatically. We numerically model the pseudoground state of excess electrons ...


Measuring The Practical Particle-In-A-Box: Orthorhombic Perovskite Nanocrystals, Brandon Mitchell, Eric Herrmann, Junhao Lin, Leyre Gomez, Chris De Weerd, Yasufumi Fujiwara, Kazutomo Suenaga, Tom Gregorkiewicz Sep 2018

Measuring The Practical Particle-In-A-Box: Orthorhombic Perovskite Nanocrystals, Brandon Mitchell, Eric Herrmann, Junhao Lin, Leyre Gomez, Chris De Weerd, Yasufumi Fujiwara, Kazutomo Suenaga, Tom Gregorkiewicz

Physics

A connection between condensed matter physics and basic quantum mechanics is demonstrated as we use the fundamental 3D particle-in-a-box model to explain the optical properties of semiconductor nanocrystals, which are substantially modified due to quantum confinement. We also discuss recent advances in the imaging and measurement capabilities of transmission electron microscopy, which have made it possible to directly image single nanocrystals while simultaneously measuring their characteristic absorption energies. We introduce the basic theory of nanocrystals and derive a simplified expression to approximate the optical bandgap energy of an orthorhombic nanocrystal. CsPbBr3 perovskite nanocrystals are used to demonstrate this model due ...


E. Coli Elongation Factor Tu Bound To A Gtp Analogue Displays An Open Conformation Equivalent To The Gdp-Bound Form, Jesper S. Johansen, Darius Kavaliauskas, Shawn H. Pfeill, Mickael Blaise, Barry C. Cooperman, Yale E. Goldman, Søren S. Thirup, Charlotte R. Knudsen Aug 2018

E. Coli Elongation Factor Tu Bound To A Gtp Analogue Displays An Open Conformation Equivalent To The Gdp-Bound Form, Jesper S. Johansen, Darius Kavaliauskas, Shawn H. Pfeill, Mickael Blaise, Barry C. Cooperman, Yale E. Goldman, Søren S. Thirup, Charlotte R. Knudsen

Physics

According to the traditional view, GTPases act as molecular switches, which cycle between distinct ‘on’ and ‘off’ conformations bound to GTP and GDP, respectively. Translation elongation factor EF-Tu is a GTPase essential for prokaryotic protein synthesis. In its GTP-bound form, EF-Tu delivers aminoacylated tRNAs to the ribosome as a ternary complex. GTP hydrolysis is thought to cause the release of EF-Tu from aminoacyl-tRNA and the ribosome due to a dramatic conformational change following Pi release. Here, the crystal structure of Escherichia coli EF-Tu in complex with a non-hydrolysable GTP analogue (GDPNP) has been determined. Remarkably, the overall conformation of EF-Tu ...


Assembling And Characterizing The Efficiency Of An Injection Locked Laser System For Cold Neutral Atom Optical Traps, Alexandra Papa Crawford Jun 2018

Assembling And Characterizing The Efficiency Of An Injection Locked Laser System For Cold Neutral Atom Optical Traps, Alexandra Papa Crawford

Physics

Creating a quantum computer requires a system of particles that can be well-controlled to achieve quantum operations. We need a large array of these particles – called qubits – with long coherence times, which can be initialized, operated on by single and two qubit gates, and read out. For neutral atoms, the qubit states are stable ground states that interact minimally with the environment, leading to long coherence times. Experimentally, the qubits are manipulated using carefully timed laser beam pulses with controlled frequency and intensity, but the outstanding issue for optically trapping cold atoms is finding a light pattern that can hold ...


Cuoricino Thermal Pulse Classification By Machine Learning Algorithms, Joshua Mann Jun 2018

Cuoricino Thermal Pulse Classification By Machine Learning Algorithms, Joshua Mann

Physics

Many of the various properties of neutrinos are still a mystery. One unknown is whether neutrinos are Majorana fermions or Dirac fermions. Cuoricino and CUORE are experiments that aim to solve this mystery. Noise reduction in these experiments hinges on the ability to discern among alpha, beta and gamma particle detections using the thermal pulses they create. In this paper, we look at Cuoricino data and attempt to classify pulses, not as alpha, beta or gamma particles, but rather as signal, noise or calibration data. We will use this preliminary testing ground to examine various machine learning algorithms' abilities in ...


Heavy Flavour In Jets And Azimuthal Correlations, Patrick J. Steffanic Jun 2018

Heavy Flavour In Jets And Azimuthal Correlations, Patrick J. Steffanic

Physics

We studied heavy-flavor azimuthal correlations using the semi-leptonic decay channel of hard-scattered bottom quarks in proton-proton collisions at center-of-mass energies of 7 TeV. We used a mixed-event method to produce a corrected correlation that hinted at back-to-back pair production. We further studied the jets resulting from these heavy-flavor hard scatterings, and jets resulting from light-flavor and gluon scattering. We compared several kinematic variables from each of the jet populations, concluding that novel kinematic variables must be developed in order to effectively separate the jet populations.


Rental Property Energy Efficiency In San Luis Obispo, Zachary Earl Shockley Mar 2018

Rental Property Energy Efficiency In San Luis Obispo, Zachary Earl Shockley

Physics

In the modern era, many people choose to rent homes instead of purchasing a home. College towns have an even more disproportionate number of renters when compared to other cities. The majority of rental properties are much less energy efficient than their owner-occupied counterparts. This project analyzes the energy efficiency issues of rental properties in San Luis Obispo and examines potential ways to remedy these issues. In order to analyze these issues, the guiding principles of building science are first discussed, followed by case studies of rental properties in San Luis Obispo. These case studies examine multiple rental properties and ...


Probing The Black-Hole-Mass-Galaxy Connection Of Active Galaxies Using 2d Galaxy Fitting Techniques On Near-Infrared Images, Isak Dan Stomberg Dec 2017

Probing The Black-Hole-Mass-Galaxy Connection Of Active Galaxies Using 2d Galaxy Fitting Techniques On Near-Infrared Images, Isak Dan Stomberg

Physics

Active Galactic Nuclei (AGNs) provide a unique opportunity to measure the mass of supermassive black holes located in the centers of their host galaxies. This enables studying the scaling relations between the mass of the black hole and the properties of the host galaxy.

In this thesis, we present an investigation of the relationship between black hole masses and the host galaxy bulge and total luminosity for a pilot sample of 15 objects imaged in the near-infrared with the 8m telescope of Gemini North observatory. We perform a 2D decomposition of the host galaxies using the software Galfit and obtain ...


Faraday-Talbot Effect From A Circular Array Of Pillars, Jessica J. Pilgram Nov 2017

Faraday-Talbot Effect From A Circular Array Of Pillars, Jessica J. Pilgram

Physics

When an oil bath is vertically oscillating with an acceleration above some critical value, known as the Faraday threshold, the bath surface becomes unstable and nonlinear standing wave patterns emerge. One phenomenon that has been observed above the Faraday threshold is the formation of Faraday-Talbot carpets, resulting from near-field diffraction. The optical Talbot effect occurs when a monochromatic wave passes through a diffraction grating. In the near-field, the formation of self- images is observed at integer multiples of what is known as the Talbot length. These two-dimensional patterns have various applications including X-ray imaging and atom and particle trapping. Two- ...


Investigation Of Ternary Fission, Alex C. Kemnitz Nov 2017

Investigation Of Ternary Fission, Alex C. Kemnitz

Physics

Ternary fission is a rare occurrence in which three particles are produced from a single fission event. This analysis uses tracked fission event data recorded by NIFFTE’s time projection chamber with a series of refined cuts to isolate all possible ternary events. The experiment used two targets, each consisting of two isotopes; one target was Pu-239 and U-235, and the other was U-238 and U-235. The data was used to measure the ternary/binary fission ratios for each isotope. The ratios for the Pu-239 and U-235 target that were found are shown to be too high due to alpha ...


Ambipolar Spin Diffusion In P-Type Gaas: A Case Where Spin Diffuses More Than Charge, F. Cadiz, V. Notot, J. Filipovic, Christopher P. Weber, L. Martinelli, A.C. H. Rowe, S. Arscott Sep 2017

Ambipolar Spin Diffusion In P-Type Gaas: A Case Where Spin Diffuses More Than Charge, F. Cadiz, V. Notot, J. Filipovic, Christopher P. Weber, L. Martinelli, A.C. H. Rowe, S. Arscott

Physics

We investigate the diffusion of charge and spin at 15 K in p-type GaAs, combining transient-grating and energy-resolved microluminescence measurements to cover a broad range of photoelectron density. At very low optical power, in a unipolar nondegenerate regime, charge and spin diffuse at the same rate, implying that the spin-drag effects are negligible. Upon increasing the photoelectron concentration up to about 1016 cm–3, the charge diffusion constant decreases because of ambipolar electrostatic interactions with the slower-diffusing holes while the spin diffusion constant is reduced only weakly by the ambipolar interaction. A further increase in the excitation power causes increases ...


Solar Powered Single-Axis Heliostat Active Solar Tracking Device, Mason Kyle Roberts Sep 2017

Solar Powered Single-Axis Heliostat Active Solar Tracking Device, Mason Kyle Roberts

Physics

As a means of cooking food, the burning of biomass accounts for over 4 million premature deaths in third world countries (“Household Air Pollution and Health”). The focus of this project was to explore an alternative that could utilize focused sunlight to cook food. A solar tracker was designed to be affixed to a parabolic, reflective, tilted single axis heliostat to follow the sun throughout the day and focus the reflected light to the bottom of a cooking surface. This surface became hot enough to for the preparation of food or boiling/sterilization of water.

A goal for each project ...


Charge State Of Vacancy Defects In Eu-Doped Gan, Brandon Mitchell, N. Hernandez, D. Lee, A. Koizumi, Y. Fujiwara, V. Dierolf Aug 2017

Charge State Of Vacancy Defects In Eu-Doped Gan, Brandon Mitchell, N. Hernandez, D. Lee, A. Koizumi, Y. Fujiwara, V. Dierolf

Physics

Eu ions have been doped into GaN in order to achieve red luminescence under current injection, where coupling between the Eu ions and intrinsic defects such as vacancies are known to play an important role. However, the charge state of the vacancies and the impact it would have on the optical and magnetic properties of the Eu ions have not been explored. Through a combination of first-principle calculations and experimental results, the influence of the charge state of the defect environment surrounding the Eu ions has been investigated. We have identified two Eu centers that are related through the charge ...


My Contributions To The Cryogenic Underground Observatory For Rare Events Experiment And The Utilization Of Geant4 In Their Analysis, Kevin Armenta Jun 2017

My Contributions To The Cryogenic Underground Observatory For Rare Events Experiment And The Utilization Of Geant4 In Their Analysis, Kevin Armenta

Physics

First, a brief introduction and background of the basics of particle physics and the Standard Model is discussed in order to give context to nature of the neutrinoless double beta decay ($2\nu\beta\beta$) and why it is so interesting to particle physicists. Next, the Cryogenic Underground Observatory for Rare Events (CUORE) experiment is discussed in detail, explaining the rational behind the experimental setup and detection process. Finally, I conclude by discussing Geant4, an important software toolkit used in particle physics, and how it is utilized in the CUORE experiment.


Improvements For The T0c+ Geometry Of The Fast Interaction Trigger (Fit) Upgrade To Alice At The Cern Lhc, Noah Miller Jun 2017

Improvements For The T0c+ Geometry Of The Fast Interaction Trigger (Fit) Upgrade To Alice At The Cern Lhc, Noah Miller

Physics

The purpose of the ALICE experiment at CERN is to investigate the properties of the strongly interacting quark-gluon plasma formed in the high-energy collisions of lead nuclei in the CERN Large Hadron Collider. ALICE has been collecting data since 2009. The upcoming upgrade of the CERN LHC injectors during 2019-20 will boost the luminosity and the collision rate beyond the design parameters for several of the key ALICE detectors including the forward trigger detectors. The new Fast Interaction Trigger (FIT) will enable ALICE to discriminate beam-beam interactions with a 99% efficiency for the collisions generated by the LHC at a ...


Optical Physics Of Rifle Scopes, Ryan Perry Jun 2017

Optical Physics Of Rifle Scopes, Ryan Perry

Physics

Optical systems are typically consist of multiple lenses and mirrors and are used in a wide variety of fields. While there exist a variety of setups, there are a few key concepts that are at the core of all of them. These could be used from the most advanced scientific research to a simple magnifying glass. They are also used in industry and consumer products such as glasses and cameras. We are going to go over these key concepts and show how they apply to telescopes, or more specifically rifle scopes. First, we will go over Snell's Law of ...


Working With Cuore In Search For The Neutrinoless-Double Beta Decay, Kevin H. Phung Jun 2017

Working With Cuore In Search For The Neutrinoless-Double Beta Decay, Kevin H. Phung

Physics

The neutrino, if found to be its own anti-particle, will reshape the Standard Model of physics. This paper will give some background information regarding CUORE’s experiment to discover the radioactive process known as neutrinoless double-beta decay, how their experiment works, and my own involvement in their research during the installation phase of the project in the summer of 2017.


On-Sight Shifting At The Cryogenic Underground Observatory For Rare Events, Aaron C. Wong Jun 2017

On-Sight Shifting At The Cryogenic Underground Observatory For Rare Events, Aaron C. Wong

Physics

During the summer of 2016, four Cal Poly students traveled to Assergi, Italy to contribute to the CUORE collaboration which is in search of a rare process called neutrinoless double beta decay. If detected, neutrinoless double beta decay will make break throughs in particle and nuclear physics, and will be the first observation of lepton number violation. The Cal Poly students provided on-sight shifting support during the installation phase of the project. This is a breakdown of the physics behind CUORE and Cal Poly's contribution.


Investigation Of Peltier Devices For Refrigeration, Evan C. Drake Jun 2017

Investigation Of Peltier Devices For Refrigeration, Evan C. Drake

Physics

The purpose of our project was to characterize Peltier devices and determine if they were good candidates toward inexpensive off-grid solar powered refrigeration in poor countries. We measured the rate of cooling with a constant temperature thermal sink for different current inputs. Through numerous experiments we calculated the coefficient of performance for two different thermoelectric coolers (TECs) through a range of temperature differentials. In addition, we found the lowest temperature these Peltier chips could reach so that we could test the accuracy of the information provided by the manufacturers spec sheets. Overall the data gathered through our research is compelling ...


The Classical Limit Of Entropic Quantum Dynamics, Anthony V. Demme May 2017

The Classical Limit Of Entropic Quantum Dynamics, Anthony V. Demme

Physics

The framework of entropic dynamics (ED) allows one to derive quantum mechanics as an application of entropic inference. In this work we derive the classical limit of quantum mechanics in the context of ED. Our goal is to find conditions so that the center of mass (CM) of a system of N particles behaves as a classical particle. What is of interest is that ~ remains finite at all steps in the calculation and that the classical motion is obtained as the result of a central limit theorem. More explicitly we show that if the system is sufficiently large, and if ...


Room-Temperature Self-Powered Energy Photodetector Based On Optically Induced Seebeck Effect In Cd3As2, Niloufar Yavarishad, Tahereh Hosseini, Elaheh Kheirandish, Christopher P. Weber, Nikolai Kouklin Apr 2017

Room-Temperature Self-Powered Energy Photodetector Based On Optically Induced Seebeck Effect In Cd3As2, Niloufar Yavarishad, Tahereh Hosseini, Elaheh Kheirandish, Christopher P. Weber, Nikolai Kouklin

Physics

We demonstrate an intrinsically fast Seebeck-type metal–semimetal–metal infrared photodetector based on Cd3As2 crystals. The Seebeck voltage is induced under off-center illumination, leading to asymmetric temperature gradients and a net current flow. The room-temperature responsivity of the sensor is 0.27 mA/W. The photocurrent signal is readily registered at a modulation frequency of 6 kHz, and the intrinsic bandwidth of the sensor is predicted to approach the terahertz range. The photocurrent depends on the optical power and modulation frequency. Our study demonstrates that crystallineCd3As2 is a promising material for high-bandwidth and spectrally ...


Developing An Imaging System To Monitor Atom Traps For Neutral Atom Quantum Computing, Jenna Valdez Mar 2017

Developing An Imaging System To Monitor Atom Traps For Neutral Atom Quantum Computing, Jenna Valdez

Physics

Quantum computing exploits the laws of quantum mechanics to exponentially increase computing rate for certain processes. A realized quantum computer could break encryptions and simulate large quantum systems previously unbreakable and unattainable with classical computers. Neutral atom quantum computing is a viable candidate for building these devices that satisfies four of the five criteria for a successful quantum computer. We are exploring a novel method in creating neutral atom qubits that involves a magneto-optical trap and a dipole trap created in the diffraction pattern behind an array of pinholes. The magneto-optical trap works to cool the atoms and centralize them ...


On The Redshift Distribution And Physical Properties Of Act-Selected Dsfgs, T. Su, T. A. Marriage, V. Asboth, A. J. Baker, J. R. Bond, D. Crichton, M. J. Devlin, R. Dünner, D. Farrah, D. T. Frayer, M. B. Gralla, K. Hall, M. Halpern, A. I. Harris, M. Hilton, A. D. Hincks, J. P. Hughes, M. D. Niemack, L. A. Page, B. Partridge, J. Rivera, D. Scott, J. L. Sievers, Robert J. Thornton, M. P. Viero, L. Wang, E. J. Wollack, M. Zemcov Jan 2017

On The Redshift Distribution And Physical Properties Of Act-Selected Dsfgs, T. Su, T. A. Marriage, V. Asboth, A. J. Baker, J. R. Bond, D. Crichton, M. J. Devlin, R. Dünner, D. Farrah, D. T. Frayer, M. B. Gralla, K. Hall, M. Halpern, A. I. Harris, M. Hilton, A. D. Hincks, J. P. Hughes, M. D. Niemack, L. A. Page, B. Partridge, J. Rivera, D. Scott, J. L. Sievers, Robert J. Thornton, M. P. Viero, L. Wang, E. J. Wollack, M. Zemcov

Physics

No abstract provided.


Elasticity Of Cylindrical Black Holes, Conrad Pearson Dec 2016

Elasticity Of Cylindrical Black Holes, Conrad Pearson

Physics

Black holes are regions of strong gravity, and are often regarded as behaving like drops of fluid. When this line of thought is applied to cylindrical black holes (black cylinders), a mapping can be made between known instabilities for black cylinders and ordinary fluid cylinders. However, this known correlation is increasingly less accurate for lower spatial dimensions, and I seek to correct this discrepancy in this thesis. By considering soft solids instead of pure fluids, elastic energy can be included, which brings us closer to a direct comparison. In improving this mapping, it becomes possible to better understand the behavior ...


Large-Scale Outflows In Luminous Qsos Revisited: The Impact Of Beam Smearing On Agn Feedback Efficiencies, Bernd Husemann, Julia Scharwächter, Vardha N. Bennert, V. Manieri, Jong-Hak Woo, Darshan Kakkad Oct 2016

Large-Scale Outflows In Luminous Qsos Revisited: The Impact Of Beam Smearing On Agn Feedback Efficiencies, Bernd Husemann, Julia Scharwächter, Vardha N. Bennert, V. Manieri, Jong-Hak Woo, Darshan Kakkad

Physics

Context. Feedback from active galactic nuclei (AGN) is thought to play an important role in quenching star formation in galaxies. However, the efficiency with which AGN dissipate their radiative energy into the ambient medium remains strongly debated.

Aims. Enormous observational efforts have been made to constrain the energetics of AGN feedback by mapping the kinematics of the ionized gas on kpc scale. We study how the observed kinematics and inferred energetics are affected by beam smearing of a bright unresolved narrow-line region (NLR) due to seeing.

Methods. We re-analyse optical integral-field spectroscopy of a sample of twelve luminous unobscured quasi-stellar ...


Fluctuations In A Cosmology With A Spacelike Singularity And Their Gauge Theory Dual Description, Robert H. Brandenberger, Elisa G.M. Ferreira, Ian A. Morrison, Yi-Fu Cai, Sumit R. Das, Yi Wang Oct 2016

Fluctuations In A Cosmology With A Spacelike Singularity And Their Gauge Theory Dual Description, Robert H. Brandenberger, Elisa G.M. Ferreira, Ian A. Morrison, Yi-Fu Cai, Sumit R. Das, Yi Wang

Physics

We consider a time-dependent deformation of anti–de Sitter (AdS) space-time which contains a spacelike “singularity”—a spacelike region of high curvature. Making use of the AdS/CFT correspondence we can map the bulk dynamics onto the boundary. The boundary theory has a time dependent coupling constant which becomes small at times when the bulk space-time is highly curved. We investigate the propagation of small fluctuations of a test scalar field from early times before the bulk singularity to late times after the singularity. Under the assumption that the AdS/CFT correspondence extends to deformed AdS space-times, we can map ...


Community Outreach With Play-Doh® Electronics, Thomas J. Bensky, William Bensky Oct 2016

Community Outreach With Play-Doh® Electronics, Thomas J. Bensky, William Bensky

Physics

It never fails: you’re in your office and the phone rings. Your department head says, “Hi! Fifty kids are coming to campus in 30 minutes. Can you meet with them and give them a one-hour hands-on activity that will make them excited about physics?” Likely you’ll run to your demonstration room and grab anything that’ll generate a bright light or cause something to explode or levitate, right? In recent years, we’ve taken a more systematic approach to hosting visitors by developing a ready-to-go hands-on activity that provides opportunities for learning about DC electric circuits.


Enhancement Of Hopping Conductivity By Spontaneous Fractal Ordering Of Low-Energy Sites, Tianran Chen, Brian Skinner Aug 2016

Enhancement Of Hopping Conductivity By Spontaneous Fractal Ordering Of Low-Energy Sites, Tianran Chen, Brian Skinner

Physics

Variable-range hopping conductivity has long been understood in terms of a canonical prescription for relating the single-particle density of states to the temperature-dependent conductivity. Here we demonstrate that this prescription breaks down in situations where a large and long-ranged random potential develops. In particular, we examine a canonical model of a completely compensated semiconductor, and we show that at low temperatures hopping proceeds along self-organized, low-dimensional subspaces having fractal dimension d = 2. We derive and study numerically the spatial structure of these subspaces, as well as the conductivity and density of states that result from them. One of our prominent ...


About Agn Ionization Echoes, Thermal Echoes, And Ionization Deficits In Low Redshift Lyman-Alpha Blobs, Mischa Schirmer, Sangeeta Malhotra, Nancy A. Levenson, Hai Fu, Rebecca L. Davies, William Keel, Paul Torrey, Vardha Nicola Bennert, Anna Pancoast, James E. H. Turner Jul 2016

About Agn Ionization Echoes, Thermal Echoes, And Ionization Deficits In Low Redshift Lyman-Alpha Blobs, Mischa Schirmer, Sangeeta Malhotra, Nancy A. Levenson, Hai Fu, Rebecca L. Davies, William Keel, Paul Torrey, Vardha Nicola Bennert, Anna Pancoast, James E. H. Turner

Physics

We report the discovery of 14 Lyα blobs (LABs) at z ∼ 0.3, existing at least 4–7 billion years later in the Universe than all other LABs known. Their optical diameters are 20–70 kpc, and GALEX data imply Lyα luminosities of (0.4–6.3) × 1043 erg s−1. Contrary to high-z LABs, they live in low-density areas. They are ionized by AGN, suggesting that cold accretion streams as a power source must deplete between z = 2 and 0.3. We also show that transient AGN naturally explain the ionization deficits observed in many LABs. Their ...