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  • tnithyanandan 7:08 pm on March 21, 2014 Permalink | Reply
    Tags: , Cosmology, , , low frequency, , power spectra, , radio astronomy, ,   

    Joining ASU and a peek into my research 

    My name is Nithyanandan Thyagarajan. I joined the LoCo (Low frequency Cosmology) lab group at ASU SESE headed by Prof. Judd Bowman, in September 2013 as a postdoctoral research scholar. I did my bachelor’s in Electrical Engineering from IIT Madras, India. For my PhD thesis at Columbia University, I worked on identifying and characterizing variable and transient radio objects by conducting one of the biggest searches of its kind in the radio sky. I then moved to Raman Research Institute in Bangalore, India as a postdoc and worked on statistical characterization of foreground contamination in the power spectrum of redshifted 21 cm line emission of neutral hydrogen during the epoch of reionization (EoR). During this period I got associated with the Murchison Widefield Array (MWA) project.

    The LoCo group has members involved in a variety of interesting projects. Besides having a strong presence in the MWA project, the members are also involved in other EoR experiments using the Experiment to Detect the Global EoR Step (EDGES), Precision Array for Probing the Epoch of Reionization (PAPER), Dark Ages Radio Explorer (DARE), Long Wavelength Array (LWA) and other theoretical and modeling projects. I am excited to be a part of this diverse group which provides enormous opportunities to learn science through the many perspectives from these different experiments.

    Currently, I am focusing on setting up simulations to predict the response of the MWA telescopes to all-sky radio emission. My aim is to isolate and characterize the signatures of different spatial structures of foreground objects such as the Milky Way, and other extragalactic objects besides the instrument’s own systematic effects on the observed power spectrum that contains information about the spatial distribution of redshifted 21 cm line emission from neutral hydrogen from the EoR. An understanding of the radio foreground objects and that of the telescope is extremely significant because the expected signatures from the neutral hydrogen emission during the EoR are extremely faint compared to the contamination from radio foregrounds and instrumental artifacts. Detecting EoR signal may be impossible without a precise removal of such contamination and artifacts.

    Here’s an approximate simulation of the radio foreground and instrumental signatures we expect to see in the power spectrum when the entire hemisphere of the sky is observed by the MWA telescope. The simulations are found to match well with results from analysis of data from the MWA telescopes.

    Predicted spatial power spectra of a an all-sky model as seen by MWA telescopes.

    Predicted spatial power spectra of an all-sky radio model of foreground objects as seen by MWA telescopes. The all-sky radio emission model is shown in the central panel. The peripheral panels show the power spectra recorded by different antenna pairs (x-axis) grouped by orientation of the lines joining them (EW at bottom right, NE at top right, NS at top center, and NW at top left). The x-axes in all the peripheral panels represent the different antenna pairs which sample the transverse spatial information from emission from the plane of the sky while the y-axes sample spatial structures into the plane of the sky. Since the sky model contains heterogeneous spatial structures, these different antenna pairs record different spatial information. The wedge/fork shaped feature prominent in the top center panel and the bright horizontal feature in all the peripheral panels arise out of the emission from our galaxy and other extragalactic radio emission (all the bright features enclosed by the forked black lines). The periodically repeated horizontal structures are caused by the frequency characteristics of the MWA telescopes.

  • margaretelizabethblumm 10:18 am on August 9, 2013 Permalink | Reply
    Tags: , conference, education, , , radio astronomy   

    Astronomical Society of the Pacific Meeting 

    Recently, I attended the Astronomical Society of the Pacific’s annual Education and Public Outreach conference in San Jose, CA to represent the Low-Frequency Cosmology Group (LoCo Lab).  It was an amazing experience!  I met with many people involved in the educational outreach community from across the nation.

    I presented a postertitled “RFI Detectives: Raising Awareness of the Radio Sky” describing an activity we modified to use for large public events.  This activity helps us to teach aboutradio wavelengths, frequency, and radio astronomy using hand-held radios to let children search for sources of radio frequency interference; or RFI, for themselves.  We adapted the activity from the NRAO activity “Be an RFI Detective”.  Many people came by to view and discuss my poster, and seemed quite interested in the research we are doing.

    I attended numerous talks about a variety of things, from the politics of astronomy education to how to teach astronomy to preschoolers.  Everyone was so knowledgeable and incredibly kind.  I networked and make contacts that will assist in future efforts toward a career in education outreach.

    One of the sessions I went to was about how to teach the scale of the Universe.  I was amazed to see how far apart the planets are.  We had string that was scaled to the distance of the planets (I don’t remember what the scale factor was), and we stretched out the Solar System.  I objectively knew that the distances were huge, but seeing how the outer planets wouldn’t even fit in the room was surprising.

    The conference provided an invaluable learning experience and was fascinating. I am very grateful that I was able to go and meet so many like-minded people who share my passion for teaching the world about the wonders of space. This was a wonderful opportunity and I will make sure to use all I have learned to improve the outreach here and get people more interested in space.


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