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Extracting the spectrum of the highly redshifted (10 < z < 35) 21-cm background from foregrounds

Event Details

Event Dates: 

Friday, May 26, 2017 - 12:00pm

Seminar Location: 

  • JILA 10th Floor - Foothills Room

Speaker Name(s): 

Keither Tauscher

Speaker Affiliation(s): 

CU Physics, CASA
Seminar Type/Subject

Scientific Seminar Type: 

  • Astrophysics Lunch Seminar

Event Details & Abstract: 

The highly redshifted 21-cm radiation background’s monopole component—a weak (~100 mK) but attractive observational target for low-frequency (40 < f / (1 MHz) < 120) radio experiments due to its expected large impact on our ability to constrain the properties of the earliest generations of stars and the properties of the early Inter Galactic Medium (IGM)—is hidden amongst foregrounds with strengths between 10^3 K and 10^4 K. Extracting it is the main challenge of any 21-cm cosmology experiment which uses an antenna with a large (>60 degrees FWHM) beam. In this talk, I will describe a method by which the foreground can be separated from the 21-cm global signal given a realistic instrument. The method utilizes a weighted form of Singular Value Decomposition (SVD) to pick out the main modes of variation from simulated datasets. There are separate datasets for each component of the model. The signal dataset is simulated by exploring the parameter space of the ares code. The other datasets are derived from prior measurements, including expected uncertainties on antenna and receiver measurements. After detailing the method of calculating the basis vectors of the signal, foreground and instrument, I present results showing that, using a Markov Chain Monte Carlo (MCMC) sampler, the signal can be extracted to within ∼20 mK given justified priors and the instrument proposed for the Dark Ages Radio Explorer (DARE) experiment.