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Elena Pierpaoli

Professor of Physics and Astronomy

Contact Information
E-mail: pierpaol@usc.edu
Phone: (213) 740-1117
Office: SHS 371

LINKS
Curriculum Vitae
Personal Website
 

Education

  • M.S. Physics, University of Milano, 3/1994
  • Ph.D. Aastrophysics, SISSA-ISAS, 10/1998

  • Academic Appointment, Affiliation, and Employment History

    • Professor, University of Southern California, 01/2011-  
    • Associate Professor, University of Southern California, 04/2007-12/2010  
    • Assistant Professor, University of Southern California, 06/2006-03/2007  
    • Research faculty, Caltech, 09/01/2004-05/31/2006  
    • Research Staff, Princeton University, 01/01/2002-09/01/2004  
    • CITA National Fellow, University of British Columbia, 11/15/1998-11/14/2001  

    Description of Research

    Summary Statement of Research Interests
    I am a theoretical cosmologist, specialized in model comparison with data. I mainly work on the cosmic microwave background and the large scale structure of the Universe.
    Research Keywords
    Cosmology, large scale strucutre, cosmic microwave background, early Universe, dark matter, data analysis
    Research Specialties
    As a theoretical cosmologist, my main aim is to determine the content of the Universe, its evolution and characteristics now and at very early times. While these questions have been outstanding issues for Humankind for centuries, we are now in the position to address them is a quantitative way through the study of astrophysical objects outside our own Galaxy. Two major astrophysical observables can be invoked for this purpose: the Cosmic Microwave Background (CMB) radiation, otherwise known as the radiation that comes to us almost from the times of the Big Bang, and the distribution of galaxies beyond our own. The study of such anisotropies has tremendously advanced the knowledge of the field. Indeed, they convey very straightforward information on the global geometry of the Universe, the kind of matter and energy it contains and also the kind of processes that very early on have seeded the inhomogeneities which have then evolved into the observed bound structures around us (e.g. galaxies and clusters of galaxies). The last generation CMB satellite (Planck) is now flying and collecting data. Part of my group has been involved in the preparation of this mission and is now analyzing the data. One of my research topics consists in testing possible theoretical scenarios of our Universe by comparing the predictions it would imply for these anisotropies with the actual observations. Apart from the CMB, I also extensively work on galaxy clusters. Clusters are the biggest gravitationally–bound objects in our Universe and are composed of dark matter, galaxies and free “gas” (free charged particles). Clusters are important for two reasons: first they are tracers of the underlying matter distribution, second they form for gravitational collapse (contrasting cosmic expansion) and merging events of smaller objects (like galaxies). Studying clusters we can therefore probe the nature of the dark energy (leading the current expansion), dark matter and the assembly of luminous matter.
    Detailed Statement of Research Interests
    As a theoretical cosmologist, my main aim is to determine the content of the Universe, its evolution and characteristics now and at very early times. While these questions have been outstanding issues for Humankind for centuries, we are now in the position to address them is a quantitative way through the study of astrophysical objects outside our own Galaxy. Two major astrophysical observables can be invoked for this purpose: the Cosmic Microwave Background (CMB) radiation, otherwise known as the radiation that comes to us almost from the times of the Big Bang, and the distribution of galaxies beyond our own. The study of such anisotropies has tremendously advanced the knowledge of the field. Indeed, they convey very straightforward information on the global geometry of the Universe, the kind of matter and energy it contains and also the kind of processes that very early on have seeded the inhomogeneities which have then evolved into the observed bound structures around us (e.g. galaxies and clusters of galaxies). The last generation CMB satellite (Planck) is now flying and collecting data. Part of my group has been involved in the preparation of this mission and is now analyzing the data. One of my research topics consists in testing possible theoretical scenarios of our Universe by comparing the predictions it would imply for these anisotropies with the actual observations. The kind of questions Planck can help to answer involve the amount on type of dark matter and dark energy, as well as characteristics of the initial fluctuations imprinted by the big bang. With postdoc Loris Colombo we worked on the determination of these cosmological parameters, specifically focusing on how well each of these properties can be determined given the characteristics of the Planck instrument. Another line of research I pursued in the past years is the preparation of future CMB missions. So far, only the total intensity of the CMB radiation has been extensively studied. However, this radiation also has another property, the polarization, which could yield an equivalent amount of information, and could actually be the smoking gun for particular phenomena. Polarization information could be crucial to characterize very early Universe phenomena like inflation through the study of the gravitational waves they generate. Planck will observe the polarization quite well, but it is likely that another mission will be needed to extract all possible science. As the polarization signal is much weaker than the total intensity one, it is more difficult to detect and also its observation may be more easily contaminated by other astrophysical objects emitting in the same band. For this reason, I dedicated part of my attention to the issue of polarization data analysis with focus on component separation and its impact on parameter determination. We worked on the potentials of future surveys to recover the signal of these gravitational waves and disentangle inflationary models. Apart from the CMB, I also extensively work on galaxy clusters. Clusters are the biggest gravitationally–bound objects in our Universe and are composed of dark matter, galaxies and free “gas” (free charged particles). Clusters are important for two reasons: first they are tracers of the underlying matter distribution, second they form for gravitational collapse (contrasting cosmic expansion) and merging events of smaller objects (like galaxies). Studying clusters we can therefore probe the nature of the dark energy (leading the current expansion), dark matter and the assembly of luminous matter. Moreover, as the gas in clusters underwent very little processing, it is considered a pristine sample of what was created in the early Universe during nucleosynthesis. Clusters are classically observed in the optical and X–ray band because of their galaxy and gas emission respectively. I dealt with clusters observed in both wavebands. Recently, my group lead and the construction of the biggest optical cluster catalog at the present time. We also characterized the population of the brightest galaxies in the clusters. By looking at the light emitted in different colors, it is possible to determine the age and characterize their formation. This information is important in understanding how matter in the Universe first assembled. A very novel way of studying clusters is through their interaction with the CMB. As the gas scatters the CMB radiation, clusters are also detectable in CMB experiments in the radio and infrared bands through the so–called Sunyaev-Zel’dovich (SZ) effect. The unique feature of this effect is that it does not depend on distance, allowing to detect clusters that are very far away. Only a few SZ observations of targeted clusters have been published so far, the major surveys being underway. Planck, for instance, is producing a full–sky map of the most massive clusters in the Universe. Other experiments, focusing on smaller area of the sky, are producing more resolved images of clusters. We are currently working on high–resolution images of the clusters from recently acquired ground–based observations. We are combining radio and X–ray images to extract information on the precise profile of the cluster, with the ultimate goal of understanding how processes like mass accretion or central cooling on the cluster occur and affect the structure evolution. Finally, we are using the information on cluster’s velocities that can be inferred from the SZ signal in order to constrain bulk flows on the largest scales in our Universe. As Planck will produce the first all-sky map of the most massive nearby clusters, the measurements of bulk flows will finally be possible with greatly improved precision. Such information shed lights on early–Universe phenomena such as inflation. As these new data is becoming available, a multi–band study of clusters will be possible, allowing to connect the physics of galaxy formation with the one of the gas component. As the first SZ cluster observations were produced only last year, the exploitation of SZ clusters for cosmology is at its very initial stages. We plan to use these observations for understanding fundamental physical principles, like how gravity works on large scales and what is the nature of dark energy and dark matter. Recently, I also started collaborations with Matilde Marcolli, a Professor mathematical physics, on the cosmological implications of non–commutative geometry. Non–commutative geometry offers a framework for models of the early Universe, which however need to satisfy some requirements for particle production and generation of perturbations which are in agreement with the data. We are in the process of testing such predictions.

    Affiliations with Research Centers, Labs, and Other Institutions

    • Caltech, Visiting faculty
    • Jet Propulsion Laboratory, Non-resident affiliate

    Guest Lectures in Courses

    • PHYS 190-Freshman Colloquium: "What's new in Cosmology today", 2010-2011   
    • TASI lectures: The Cosmic Microwave Background, 2009-2010   

    Honors and Awards

    • NASA Group Achievement Award (2011), Fall 2011   
    • NASA Group Achievement Award - Planck Data Analysis Team (2010), 2010-2011   
    • NSF ADVANCE Fellow, 7/2004-6/2010  

    Service to the University

    Committees
    • Chair, Physics Graduate Admission, 03/2010-10/2012  
    • Member, WiSE College committee and advisory Board, 2010-2011   
    • Member, Graduate Admissions, 09/2006-08/2010  
    • Member, Graduate and undergraduate curriculum, 2009-2010   
    • Member, Strategic University Planning, Spring 2010   
    • Member, Cosmology program, 03/2007-12/2009  
    Media, Alumni, and Community Relations
    • USC Vision and Voices event "Einstein Cosmic Messangers"- organizer, 2010-2011   
    • 217th AAS Meeting: Press release on Planck early results, Spring 2011   
    • Invited guest at the USC College Program: "Junior Faculty Showcase", 2007-2008   
    • Invited guest at the WISE Undergraduate Students Residence at USC, 2006-2007   
    • Invited guest at the USC College Doctoral Fellowship Program:"Inside the Academics Studio", 2006-2007   

    Service to the Profession


    Professional Memberships
    • American Astronomical Society, 12/2010-  




  • Department of Physics and Astronomy
  • University of Southern California
  • 825 Bloom Walk
  • ACB 439
  • Los Angeles, CA 90089-0484