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Journal Club Seminars From 2013 - 2014


FALL 2013

September 20, 2013

Alex's Title: "Star Formation Quenching and AGN
Identification in Galaxies"

Alex Mendez (12:00-1:00)
Physics Graduate Student

Alex's Abstract: I will discuss two observational projects related to galaxy and active galactic nuclei (AGN) evolution at z < 1. First I will present a statistical study of the morphologies of galaxies in which star formation is being shut down or quenched; this has implications for how red, elliptical galaxies are formed. I will discuss the physical processes behind star formation quenching from the morphological transformations that galaxies undergo during this process. Then I will focus on multi-wavelength AGN selection methods and tie together disparate results in the literature. Several IR-AGN selection methods have been developed using Spitzer/IRAC data in order to supplement traditional X-ray AGN selection; I will characterize the uniqueness and complementarity of these methods as a function of both IR and X-ray depth. I will use data from the PRIsm MUlti-object Survey (PRIMUS) to compare the efficiency of IR and X-ray AGN selection and discuss the properties of the AGN and host galaxy populations of each. Finally, I will briefly mention ongoing work to compare the clustering of observed IR and X-ray AGN samples relative to stellar mass-matched galaxy samples.

October 4, 2013

Nathan's Title: "Living Degenerately: Could Biology Exist Near a White Dwarf,
and Could Kepler Still Find It?"

Nathan Johnson (12:00-1:00)
Physics Graduate Student

October 11, 2013

Edmond's Title: "Galaxy Zoo: Observing Secular Evolution Through Bars"
Darcy's Title: "Dark Matter Constraints from Observations of 25 Milky Way
Satellite Galaxies with the Fermi Large Area Telescope"

Edmond Cheung (12:00-12:30)
Graduate Student, Astronomy & Astrophysics Department
UC Santa Cruz
Darcy Barron (12:30-1:00)
Physics Graduate Student

Edmond's Abstract: Observations have shown that there is a connection between the presence of a bar and the properties of a galaxy. In a parallel effort, simulations have shown that this connection is consistent with the theory of bar-driven secular evolution. But observational evidence of bar-driven secular evolution has been sparse. In this talk, I use the Galaxy Zoo 2 dataset to look for evidence of this secular evolution. My sample consists of 13,295 disk galaxies, with an overall bar fraction of 23.6 ± 0.4%, of which 1,154 barred galaxies also have bar length measurements. These samples are the largest ever used to study the role of bars in disk galaxy evolution. I characterize bars by the bar likelihood, the likelihood a bar is present in a given galaxy, and the bar length. These two bar properties show interesting correlations with the specific star formation rate and the inner central structure of galaxies. Comparing these observations to state-of-the-art simulations of bar evolution, which include live halos and the effects of gas and star formation, reveals that trends are consistent with the predicted effects of gas content and bulges on bar formation and evolution. These results represent empirical evidence for secular evolution driven by bars in disk galaxies. This work suggests that bars are not stagnant structures within disk galaxies, but are a critical evolutionary driver of their host galaxies in the local universe (z < 1).

October 18, 2013

Alberto's Title: "The measurement of the expansion rate of the Universe
from gamma-ray attenuation"

Alberto Dominguez (12:00-1:00)
Postdoctoral Scholar, Department of Physics and Astronomy
UC Riverside

Alberto's Abstract: We discuss the detection of the cosmic gamma-ray horizon (CGRH) that is independent of any extragalactic background light (EBL) model, which allows us to measure the Hubble constant by using gamma-rays. The CGRH is a fundamental quantity in cosmology. It gives an estimate of the opacity of the Universe to very-high energy (VHE) gamma-ray photons due to photon-photon pair production with the EBL. Our CGRH detection is possible thanks to a multiwavelength catalog of blazars that includes the latest data analysis from the Fermi satellite and Cherenkov telescopes. Interestingly, the observed CGRH is compatible with the current knowledge of the EBL. We show how the detection of the CGRH allows us to measure the expansion rate of the Universe from gamma-ray attenuation. The value of the Hubble constant that we derive is compatible with present-day measurements using well established methods such as local distance ladders and cosmological probes. We also discuss an observational strategy aimed to reduce the uncertainties in the Hubble constant estimate from our novel and independent technique.

October 25, 2013

Irina's Title: "Modeling the hierarchical evolution of galaxy clusters"

Irina Dvorkin (12:00-1:00)
Graduate Student, Department of Astrophysics
Tel Aviv University

Irina's Abstract: Measurements of the mass function of galaxy clusters provide tight constraints on various cosmological parameters, in particular the equation of state of dark energy and the neutrino mass. However, in order to fully exploit this powerful probe it is necessary to develop accurate models for the relations between cluster mass and its observable properties. In this talk I will present a semi-analytic approach to modeling the hierarchical evolution of galaxy clusters and show how it can facilitate the analysis of current and upcoming cluster surveys.

November 1, 2013

Marcel's Title: "Observing the highest redshift galaxies"

Marcel Neeleman (12:00-12:30)
Physics Graduate Student
[OPEN TIME SLOT] (12:30-1:00)

Marcel's Abstract: In the spirit of a real Journal Club, I will be discussing in very general terms the steps and challenges one faces to discover the highest redshift galaxies (i.e. z >7). In particular, I will be focussing on a recent discovery of a spectroscopically confirmed galaxy at redshift 7.51.

November 8, 2013

Mojegan's Title: "The Relationship Between Star Formation Rate and
X-ray Luminosity"

Mojegan Azadi (12:00-12:30)
Physics Graduate Student
[OPEN TIME SLOT] (12:30-1:00)

November 15, 2013

Anna's Title: "Bright and dark: satellite galaxies as a test of galaxy formation
and the nature of dark matter"

Anna Nierenberg (12:00-1:00)
Graduate Student, Astronomy & Astrophysics
UC Santa Barbara

Anna's Abstract: I present our recent measurements of the spatial distribution and the cumulative luminosity function of satellites up to a thousand times fainter than their hosts, as a function of host stellar mass and morphology between redshifts 0.1 and 0.8, using imaging from the COSMOS fields and a rigorous statistical analysis. I will demonstrate how these measurements provide powerful new constraints for abundance matching and cosmological simulations in the context of both warm and cold dark matter, and how future measurements of faint satellite colors using CANDELS, will provide important distinguishing power between warm and cold dark matter models. In addition, I will present results from a complementary gravitational lens modeling project in which we use spatially resolved spectra obtained with OSIRIS at Keck to place new constraints on the subhalo mass function.

November 22, 2013


 This week's Journal Club will feature a three-member panel discussing community service and outreach in physics. The panel will discuss outreach ideas and events as well as how outreach plays a role within the physics community. The topics of discussion will be directed towards grad students, but everybody in CASS is welcome to attend and offer advice and ask questions. The panel consists of Tom Murphy, Adam Burgasser, and Dianna Leilani.

November 29, 2013


December 6, 2013

Paul's Title: "The first Suzaku observation of 4U 1538-522"
Dr. Nicholls's Title: "A nova re-accretion model for J-type carbon stars"
by Sengupta et al. (

Paul Hemphill (12:00-12:30)
Physics Graduate Student
Christine Nicholls (12:30-1:00)
Postdoctoral Scholar


January 10, 2014

-- see Seminar calendar

January 17, 2014

Dr. Rice's Title: "Young Brown Dwarfs at Exoplanet Analogs"

Emily Rice (12:00-1:00)
Assistant Professor, Engineering Science & Physics
CUNY, Staten Island

Dr. Rice's Abstract: Young brown dwarfs and directly-imaged exoplanets have enticingly similar photometric and spectroscopic characteristics, including red near-infrared colors and spectral features indicative of low surface gravity and enhanced atmospheric dust. However, the inference of physical and atmospheric properties from observations of these cool, very-low-mass objects is fraught with degeneracies and inconsistencies. While direct observations of exoplanets will be limited to very low-resolution near-infrared spectra for the foreseeable future, young brown dwarfs can be studied over broader wavelength regimes and at higher spectral resolution, allowing us to identify and calibrate spectral diagnostics of physical and atmospheric properties, constrain age and calibrate substellar evolutionary models, and evaluate inferred properties to differentiate between possible formation scenarios. I will review the rapid progression of our understanding of young brown dwarfs in the last decade, describe current programs to identify and characterize benchmark objects, and describe the ongoing challenges in developing efficient and consistent diagnostics of temperature, gravity, metallicity, and dust/cloud properties that can also be applied to directly-imaged exoplanets. Finally I will explain how a robust understanding of the near-infrared spectra of young brown dwarfs will translate to the characterization of gas giant exoplanets observed at low spectral resolution by high contrast instruments like Project 1640, the Gemini Planet Imager, and SPHERE.

January 24, 2014

-- see Seminar calendar

January 31, 2014

Dr. Michelsen's Title: "Decoherence: Real and Fake"

Eric Michelsen (12:00-1:00)
Physics Lecturer

Dr. Michelsen's Abstract: Quantum decoherence largely explains the transition from quantum-scale phenomena to classical-scale. As expected on physical grounds, the transition is gradual, changing from coherent, to partially coherent, to classical. Unfortunately, the word "decoherence" has different meanings in different contexts, and this creates much confusion about the concept. In this talk, we attempt to clarify two sources of loss of coherence. The distinction might be important in cases where a system is dominated by only one of the sources, such as might be the case for weakly coupled particles or systems.

February 7, 2014

Alexey's Title: "New Frontiers in Neutrino Kinetics"

Alexey Vlasenko (12:00-1:00)
Physics Graduate Student

Alexey's Abstract: Neutrinos play a key role in the physics of hot, dense environments such as core collapse supernovae, compact object mergers and the early Universe. These environments can be important sites for the origin of the elements, and, in the case of supernovae, can produce observable neutrino signals. Neutrino flavor physics in these environments is poorly understood, as current treatments of neutrino flavor evolution are incomplete. I will point out some limitations of these treatments and describe some possible novel phenomena, including coherent transformation between neutrinos and anti-neutrinos and the interplay between collisions and coherent flavor evolution.

February 14, 2014

Evan's Title: TBA

Evan Grohs (12:00-1:00)
Physics Graduate Student

February 21, 2014

Dr. Skibba's Title: "New Research on Galaxy Clustering and Galaxy Clusters"

Ramin Skibba (12:00-12:30)
Assistant Project Scientist
OPEN TIME SLOT (12:30-1:00)

Dr. Skibba's Abstract: I will talk about these two papers:

February 28, 2014

Dr. Amin's Title: "After Inflation"

Mustafa Amin
Senior Postdoctoral Fellow, Kavli Institute Fellowship
Kavli Institute for Cosmology, University of Cambridge

Dr. Amin's Abstract: Our understanding of how inflation ends and how the universe gets populated with particles is incomplete. I will discuss some end of inflation scenarios, focusing on a particular case where the inflaton fragments into localized pseudo-solitons (oscillons) which can end up dominating the energy density of the universe. I will provide conditions for existence, emergence and stability of these oscillons. I will also report on the surprising simplicity of ultra-relativisitic soliton interactions.

March 7, 2014

Daniella's Title: "Bridging the gap on tight separation brown dwarf binaries"
Amol's Title: "Dark matter matters, but so do baryons"

Daniella Baradlez Gagliuffi (12:00-12:30)
Physics Graduate Student
Amol Patwardhan (12:30-1:00)
Physics Graduate Student

Daniella's Abstract: Multiplicity is a key statistic for understanding the formation of very low mass (VLM) stars and brown dwarfs. Currently, the separation distribution of VLM binaries remains poorly constrained at small separations ($\leq$ 1 AU), leading to uncertainty in the overall binary fraction. We approach this problem by searching for late M/early L plus T dwarf spectral binaries whose combined light spectra exhibit distinct peculiarities, making their identification independent of separation. We define a set of spectral indices designed to identify these systems, and use a spectral template fitting method to confirm and characterize spectral binary (SB) candidates from a library of 738 spectra from the SpeX Prism Spectral Libraries. We present ten new binary candidates, confirm two previously reported candidate and rule out two previously identified candidates, all with primary and secondary spectral types between M7-L7 and L8-T8 respectively. We find that blue L dwarfs are the primary contaminants in our sample and propose a method for segregating these sources. If confirmed by follow-up observations, these systems may potentially add to the growing list of tight separation binaries, giving further insight into brown dwarf formation scenarios.

Amol's Abstract: In recent years, observations ranging from dwarf galactic to galaxy cluster scales have seemingly thrown the Lambda-CDM paradigm into troubled waters. However, it has been argued that baryonic physics could yet effect a reconciliation between observations and theory. In my talk, I shall attempt to discuss and summarize a recent paper ( that expounds on this subject.

March 14, 2014

Chang's Title: "Precision measurements of the Hubble constant from the
gravitational lenz B1608+656"

Chang Feng (12:00-12:30)
Physics Graduate Student
OPEN TIME SLOT (12:30-1:00)


April 4, 2014

NOTE: Journal Club ends @ 12:30 today
Pei-Chun's Title: "Jupiter's New Red Spot: Dynamics, Color, and Relationship
to Jovian Climate Change"

Pei-Chun Hsu (12:00-12:30)
Physics Graduate Student

April 11, 2014

CASS All-Hands Research Interests (12:00-1:00)

April 18, 2014

Evan's Title: "Neutrinos in Cosmology I"

Evan Grohs (12:00-1:00)
Physics Graduate Student

Evan's Abstract: In the era of precision cosmology, the CMB has become the principal observation to test beyond-standard-model physics. A 2014 paper (arXiv: 1403.4852) discusses cosmological parameters relevant to neutrino physics, specifically: sum of the neutrino masses, Neff, axion mass, and sterile-neutrino mass. The authors use a Monte Carlo Markov chain algorithm to calculate the values of the parameters using data sets from Planck, BOSS, CFHTLenS, HST, and nuclear abundance observations. The authors also use Neff as a means to resolve tension between Planck and the recent BICEP2 results.

April 25, 2014

Dr. Kishimoto's Title: "Neutrinos in Cosmology II"

Chad Kishimoto (12:00-1:00)
CASS Assistant Project Scientist

May 2, 2014

Scott's Title: "Primordial light element abundances and new measurements of D/H"

Scott Gustafson (12:00-12:30)
Physics Graduate Student

May 9, 2014

Fred's Title: "How much can we learn about the physics of inflation?"

Fred Matsuda (12:00-12:30)
Physics Graduate Student
OPEN TIME SLOT (12:30-1:00)

Fred's Abstract: Fred will be discussing this article by Scott Dodelson, arxiv:1403.6310

May 16, 2014

NOTE: Special Joint Astro-Plasma Physics Seminar
           (in lieu of Journal Club) *Pizza/soda to be served*
Prof. Seo's Title: "Current Results and Prospects of Cosmic Ray Experiments"

Eun-Suk Seo (12:00-1:00)
Professor, Department of Physics
University of Maryland

Prof. Seo's Abstract: Cosmic ray research lies at the intersection of particle physics, cosmology, and astronomy. It focuses on highly relativistic particles produced in the most extreme non-equilibrium environments in nature, e.g., supernova explosions, gamma-ray bursts, or active galactic nuclei. Direct measurements of cosmic rays with satellite or balloon-borne detectors are used for understanding cosmic ray origin, acceleration and propagation. They have also been used to search for exotic sources, such as dark matter and antimatter, and to explore a possible limit to particle acceleration in supernova. Recent results will be presented, and the outlook for existing and future experiments will be discussed.

May 23, 2014

Chris's Title: "An overview of edge localized modes (ELMs) in tokamaks"

Chris Lee (12:00-1:00)
Physics Graduate Student

May 30, 2014

Joey's Title: "The Great Inflationary Debate: Inflation in a Post-Planck World"

Joey Fedrow (12:00-12:30)
Adjunct Faculty @ Palomar College and Visiting Scholar, UCSD-CASS
OPEN TIME SLOT (12:30-1:00)

June 6, 2014

Prof. Wright's Title: "Precise Radial Velocities for the Future of Exoplanet Detection"

Jason T. Wright (12:00-1:00)
Assistant Professor of Astronomy, Department of Astronomy & Astrophysics
Penn State

Prof. Wright's Abstract: As precise radial velocimetry passes the 20 year mark, it remains a fundamental component of the exoplaneteer's toolkit. I will look ahead to the role it will play in its third decade, characterizing the Kepler mission's extraordinary harvest of planetary systems, exploring the Solar neighborhood, and placing the Solar System in cosmic context.

I will describe our strategy with the MINERVA project and at the Hobby-Eberly Telescope, which proceeds both from the "outside in" and the "inside out". Long-term followup of Kepler systems with inner terrestrial planets will reveal their larger architecture, including the Jupiter analogs that dynamically craft and stabilize planetary orbits. High cadence monitoring of the brightest, nearest, most Sun-like stars will burrow beneath the astrophysical and instrumental noise to reveal the close-in terrestrial planets orbiting stars already known to have outer gas giants.

June 20, 2014

NOTE: Special Journal Club Seminar
           *Pizza/soda will be served*
Dr. Terrano's Title: "Searching for New Forces Using Torsion Pendula"

Will Terrano (12:00-1:00)
Research Assistant, Center for Experimental Nuclear Physics and Astrophysics (CENPA)
University of Washington

Dr. Terrano's Abstract: Equivalence principle violation, deviations from the inverse-square law of gravity, and long-range interactions between particle spins offer powerful tests of beyond-the-standard-model physics. Using a torsion pendulum, a technique that dates to the 18th century, is still the most sensitive way to search for these signatures of new physics. I will talk about how the experiments are done and give an update on the current and future status of such torsion balance experiments in the Eot-Wash group.