Updated: 14 May 2013

MIT Kavli Institute for Astrophysics and Space Research

2013 Postdoc Symposium

April 25, 26, and 29 11:45am−1:45pm in 37-252 (Marlar Lounge)

This annual event features the MKI-affiliated postdocs presenting 15 minute talks (with 5 minutes of questions) on their past, present, and/or future research to the MKI community. Lunch will be provided, and the talks will promptly begin at noon. There will be four speakers each day; the full schedule with abstracts is below. The symposium poster is here.

Speaker Schedule

April 25, 2013

Moderator: Kevin Schlaufman

Speaker: Amaury Triaud

Title: An Observational Path Towards Another Genesis

Abstract: I will describe some of my observing projects, mostly linked with the discovery and the characterisation of transiting planets. Despite ranging over different research topics, all those projects participate in the general goal of helping to prepare ourselves to discover earth like environments and study them to answer one of the oldest philosophical questions that remains unanswered by Science: is there life elsewhere?

Speaker: Heather Jacobson

Title: Searching for the Signatures of the First Stars

Abstract: Long-lived, low mass stars preserve the chemical composition of the material from which they formed. While it seems unlikely that any Pop III stars lasted very long, many of the stars that formed from gas enriched by their supernova explosions are expected to still be around today. The element abundances of these stars provide important information about the nature of the first stars and their supernova explosions. To date, only a handful of stars have been found so far to have [Fe/H] < -4.0. Here I will describe the hunt for more of these early generations currently being carried out by the SkyMapper survey and present preliminary results from the ~first year's high resolution spectroscopic followup of the most promising metal-poor candidates.

Speaker: Ruslan Vaulin
Title: Trace Anomaly Modified Theory of Gravity

Abstract: Within the effective field theory framework the conformal trace anomaly gives rise to a marginally significant term in the action in addition to the standard Einstein-Hilbert action of general relativity. The trace anomaly action incorporates coherent fluctuations of quantized matter fields on the curved background and is expressed in terms of a scalar field and the metric. The full theory is a scalar-tensor theory of gravity representing natural extension of general relativity to include vacuum state of matter. In the talk I will discuss some basic properties of the theory: equations of motion, coupling to metric and matter, generation and propagation of gravitational waves. I will also discuss prospects for observing effects of this extension of general relativity with future instruments e.g. LIGO or VLBI.

Speaker: Dan Castro

Title: Supernova Remnants & Cosmic Rays: An Update On Recent Progress

Abstract: No exoplanets here, I will be talking about some of the most spectacular explosions in the Universe and how their shocks produce the most energetic particles detected on Earth. I will comment on why the connection between supernova remnants (SNRs) and cosmic rays (CRs) is so important, and how we have established they are connected. Our studies of X-ray and gamma-ray emission from SNRs have allowed us to gain insight into the nature of particle acceleration as well as magnetic field amplification and the interaction of strong shocks with dense media such as molecular clouds. I will present our most recent results on these topics and outline what we want to look into in the future.

April 26, 2013

Moderator: Ruslan Vaulin

Speaker: Slawek Gras

Title: Acoustic Mode Damper for Parametric Instabilities Control

Abstract: In the next few years as the advanced detectors are commissioned and start to enter the "danger region" of parameter space where parametric instability becomes very likely. At the high optical power levels required to obtain predicted sensitivity a three mode scattering process is likely to transfer optical energy into acoustic vibrations. The research focuses on the design and construction of fully operational piezoelectric resonant dampers technique for suppressing unstable ultrasonic acoustic modes while avoiding a noise penalty. Such acoustic mode damper could be easily implemented in the detectors.

Speaker: Salvatore Vitale

Title: LIGO in the Stars with Diamonds

Abstract: By 2015 the advanced version of the LIGO detectors will be online. Their improved sensitivity will lead to frequent detections, but also allow for precise parameter estimation and model selection. Today I will talk about some of the new possibilities offered by gravitational wave astronomy. I will describe an analytical method to assess the error in the estimation of both extrinsic and intrinsic parameters. I will focus on the errors associated with the measurement of the source position, which are especially important as they will impact our ability to detect electromagnetic counterparts of the gravitational waves. I will show how gravitational waves can be used to test the strong field regime of gravity with an accuracy such that a deviation from General Relativity might be evident after O(10) detections.

Speaker: Meng Su

Title: Diffuse Gamma-ray Emission from the Inner Galaxy: Bubbles, Jets, and Dark Matter Annihilation

Abstract: Using data from the Fermi Gamma-ray Space Telescope, we have discovered two gigantic gamma-ray emitting bubble structures in our Milky Way (known as the Fermi bubbles), extending ~50 degrees above and below the Galactic center. The gamma-ray emission associated with these bubbles has a significantly harder spectrum than the inverse Compton emission from known cosmic ray electrons in the Galactic disk, or the gamma-rays produced by decay of pions from proton-ISM collisions. The bubbles are spatially correlated with the hard-spectrum microwave excess known as the WMAP haze; we also found features in the ROSAT soft X-ray maps which line up with the edges of the bubbles (confirmed by XMM-Newton observations). The Fermi bubbles are most likely created by some large episode of energy injection in the Galactic center. Furthermore, we have recently identified evidence for a gamma-ray cocoon feature within the southern bubble, with a jet-like feature along the cocoons axis of symmetry, and another directly opposite the Galactic center in the north. In addition to these components, there is evidence for line emission at E>100 GeV in the inner Galaxy. If confirmed, this line emission may be a sign of dark matter annihilation.

Speaker: Brendan Griffen

Title: To What Extent Did Metal-poor Globular Clusters Reionize the Local Inter-galactic Medium?

Abstract: The extreme age of metal-poor globular clusters make them possible contributors to the reionization of the inter-galactic medium (IGM) at z > 10. Few accurate estimates of their contribution have been made as previous simulations have not been able to directly resolve their formation sites. One current theory of how they formed is that they were seeded within the first dark matter mini-halos at high redshift. By combining simulations of highly resolved Milky Way-like halos (i.e., the Aquarius suite) with a well tested 3D radiative transfer code, I test this hypothesis and present one of the first estimates of how much metal-poor globular clusters contributed to the reionzation of the local IGM.

April 29, 2013

Moderator: Ruslan Vaulin

Speaker: Michael McDonald

Title: Witnessing the Growth of Cool Cores in Massive Galaxy Clusters

Abstract: The lack of runaway cooling in the cores of galaxy clusters has served as prime evidence that some form of feedback must balance cooling over long periods of time. Using new X-ray observations for a sample of 80+ galaxy clusters at 0.31, with the growth rate consistent with the classical cooling flow predictions, suggesting that cooling flows are indeed bringing cool material into the cluster core, but are unable to cool below some threshold energy.

Speaker: Adam Libson

Title: Progress Towards a Fiber Coupled Optomechanics Experiment

Abstract: The study of the quantum behavior of macroscopic objects has flourished in recent years, and enables tests of quantum effects in new regimes. Monitoring a mechanical oscillator using an optical cavity provides a sensitive readout of its position. This system is particularly well suited to the study of noise associated with the quantum nature of light, which is expected to be the dominant noise source in the advanced LIGO detectors. Studying the quantum behavior of an oscillator may also provide a path for precision measurement beyond the standard quantum limit. We report on progress in a fiber coupled optomechanics experiment to measure quantum back-action and quantum radiation pressure effects. The goals of the presented experiment are to measure quantum radiation pressure noise in the few kHz frequency band, ponderomotive squeezing, and other quantum back action effects. A high finesse cavity will be formed between a microgram scale cantilever and a micromachined fiber tip. This will allow the quantum interactions between the cantilever and the light in the cavity to be studied. The thermal and mechanical properties of the cantilever are described, along with the advantages gained by using a micromachined fiber tip to couple the light into the cavity.

Speaker: Kevin Schlaufman

Title: The Fate of Hot Jupiters (and the Earth too)

Abstract: The properties of exoplanet systems are both observed and theoretically suggested to strongly depend on the mass, metallicity, and evolutionary state of their host stars. One example is that evolved stars do not host hot Jupiters. Tidal evolution is one possible explanation, though the possibility that the evolved stars are more massive than the FG-type stars that dominate the main-sequence sample complicates the interpretation. However, I'll show that the Galactic space motions of the evolved host stars demand that on average they be similar in mass to main-sequence FG type planet-hosts. The two samples therefore differ only in age, and provide a glimpse of the same exoplanet population both before and after tidal evolution.

Speaker:	Amaury Triaud
Title:	An Observational Path Towards Another Genesis
Abstract:	I will describe some of my observing projects, mostly linked with the discovery and the characterisation of transiting planets. Despite ranging over different research topics, all those projects participate in the general goal of helping to prepare ourselves to discover earth like environments and study them to answer one of the oldest philosophical questions that remains unanswered by Science: is there life elsewhere?

Speaker:	Heather Jacobson
Title:	Searching for the Signatures of the First Stars
Abstract:	Long-lived, low mass stars preserve the chemical composition of the material from which they formed. While it seems unlikely that any Pop III stars lasted very long, many of the stars that formed from gas enriched by their supernova explosions are expected to still be around today. The element abundances of these stars provide important information about the nature of the first stars and their supernova explosions. To date, only a handful of stars have been found so far to have [Fe/H] < -4.0. Here I will describe the hunt for more of these early generations currently being carried out by the SkyMapper survey and present preliminary results from the ~first year's high resolution spectroscopic followup of the most promising metal-poor candidates.

Speaker:	Ruslan Vaulin
Title:	Trace Anomaly Modified Theory of Gravity
Abstract:	Within the effective field theory framework the conformal trace anomaly gives rise to a marginally significant term in the action in addition to the standard Einstein-Hilbert action of general relativity. The trace anomaly action incorporates coherent fluctuations of quantized matter fields on the curved background and is expressed in terms of a scalar field and the metric. The full theory is a scalar-tensor theory of gravity representing natural extension of general relativity to include vacuum state of matter. In the talk I will discuss some basic properties of the theory: equations of motion, coupling to metric and matter, generation and propagation of gravitational waves. I will also discuss prospects for observing effects of this extension of general relativity with future instruments e.g. LIGO or VLBI.

Speaker:	Dan Castro
Title:	Supernova Remnants & Cosmic Rays: An Update On Recent Progress
Abstract:	No exoplanets here, I will be talking about some of the most spectacular explosions in the Universe and how their shocks produce the most energetic particles detected on Earth. I will comment on why the connection between supernova remnants (SNRs) and cosmic rays (CRs) is so important, and how we have established they are connected. Our studies of X-ray and gamma-ray emission from SNRs have allowed us to gain insight into the nature of particle acceleration as well as magnetic field amplification and the interaction of strong shocks with dense media such as molecular clouds. I will present our most recent results on these topics and outline what we want to look into in the future.

Speaker:	Slawek Gras
Title:	Acoustic Mode Damper for Parametric Instabilities Control
Abstract:	In the next few years as the advanced detectors are commissioned and start to enter the "danger region" of parameter space where parametric instability becomes very likely. At the high optical power levels required to obtain predicted sensitivity a three mode scattering process is likely to transfer optical energy into acoustic vibrations. The research focuses on the design and construction of fully operational piezoelectric resonant dampers technique for suppressing unstable ultrasonic acoustic modes while avoiding a noise penalty. Such acoustic mode damper could be easily implemented in the detectors.

Speaker:	Salvatore Vitale
Title:	LIGO in the Stars with Diamonds
Abstract:	By 2015 the advanced version of the LIGO detectors will be online. Their improved sensitivity will lead to frequent detections, but also allow for precise parameter estimation and model selection. Today I will talk about some of the new possibilities offered by gravitational wave astronomy. I will describe an analytical method to assess the error in the estimation of both extrinsic and intrinsic parameters. I will focus on the errors associated with the measurement of the source position, which are especially important as they will impact our ability to detect electromagnetic counterparts of the gravitational waves. I will show how gravitational waves can be used to test the strong field regime of gravity with an accuracy such that a deviation from General Relativity might be evident after O(10) detections.

Speaker:	Meng Su
Title:	Diffuse Gamma-ray Emission from the Inner Galaxy: Bubbles, Jets, and Dark Matter Annihilation
Abstract:	Using data from the Fermi Gamma-ray Space Telescope, we have discovered two gigantic gamma-ray emitting bubble structures in our Milky Way (known as the Fermi bubbles), extending ~50 degrees above and below the Galactic center. The gamma-ray emission associated with these bubbles has a significantly harder spectrum than the inverse Compton emission from known cosmic ray electrons in the Galactic disk, or the gamma-rays produced by decay of pions from proton-ISM collisions. The bubbles are spatially correlated with the hard-spectrum microwave excess known as the WMAP haze; we also found features in the ROSAT soft X-ray maps which line up with the edges of the bubbles (confirmed by XMM-Newton observations). The Fermi bubbles are most likely created by some large episode of energy injection in the Galactic center. Furthermore, we have recently identified evidence for a gamma-ray cocoon feature within the southern bubble, with a jet-like feature along the cocoons axis of symmetry, and another directly opposite the Galactic center in the north. In addition to these components, there is evidence for line emission at E>100 GeV in the inner Galaxy. If confirmed, this line emission may be a sign of dark matter annihilation.

Speaker:	Brendan Griffen
Title:	To What Extent Did Metal-poor Globular Clusters Reionize the Local Inter-galactic Medium?
Abstract:	The extreme age of metal-poor globular clusters make them possible contributors to the reionization of the inter-galactic medium (IGM) at z > 10. Few accurate estimates of their contribution have been made as previous simulations have not been able to directly resolve their formation sites. One current theory of how they formed is that they were seeded within the first dark matter mini-halos at high redshift. By combining simulations of highly resolved Milky Way-like halos (i.e., the Aquarius suite) with a well tested 3D radiative transfer code, I test this hypothesis and present one of the first estimates of how much metal-poor globular clusters contributed to the reionzation of the local IGM.

Speaker:	Michael McDonald
Title:	Witnessing the Growth of Cool Cores in Massive Galaxy Clusters
Abstract:	The lack of runaway cooling in the cores of galaxy clusters has served as prime evidence that some form of feedback must balance cooling over long periods of time. Using new X-ray observations for a sample of 80+ galaxy clusters at 0.31, with the growth rate consistent with the classical cooling flow predictions, suggesting that cooling flows are indeed bringing cool material into the cluster core, but are unable to cool below some threshold energy.

Speaker:	Adam Libson
Title:	Progress Towards a Fiber Coupled Optomechanics Experiment
Abstract:	The study of the quantum behavior of macroscopic objects has flourished in recent years, and enables tests of quantum effects in new regimes. Monitoring a mechanical oscillator using an optical cavity provides a sensitive readout of its position. This system is particularly well suited to the study of noise associated with the quantum nature of light, which is expected to be the dominant noise source in the advanced LIGO detectors. Studying the quantum behavior of an oscillator may also provide a path for precision measurement beyond the standard quantum limit. We report on progress in a fiber coupled optomechanics experiment to measure quantum back-action and quantum radiation pressure effects. The goals of the presented experiment are to measure quantum radiation pressure noise in the few kHz frequency band, ponderomotive squeezing, and other quantum back action effects. A high finesse cavity will be formed between a microgram scale cantilever and a micromachined fiber tip. This will allow the quantum interactions between the cantilever and the light in the cavity to be studied. The thermal and mechanical properties of the cantilever are described, along with the advantages gained by using a micromachined fiber tip to couple the light into the cavity.

Speaker:	Kevin Schlaufman
Title:	The Fate of Hot Jupiters (and the Earth too)
Abstract:	The properties of exoplanet systems are both observed and theoretically suggested to strongly depend on the mass, metallicity, and evolutionary state of their host stars. One example is that evolved stars do not host hot Jupiters. Tidal evolution is one possible explanation, though the possibility that the evolved stars are more massive than the FG-type stars that dominate the main-sequence sample complicates the interpretation. However, I'll show that the Galactic space motions of the evolved host stars demand that on average they be similar in mass to main-sequence FG type planet-hosts. The two samples therefore differ only in age, and provide a glimpse of the same exoplanet population both before and after tidal evolution.