[seminar] Astro Journal Club on April 5th

[Lana Ceraj]

Dear all, 

Astro Journal club starts on Wednesday at 3 p.m. (sharp) in the seminar room F-201 of the Physics Department. 

Presenter: Jacinta Delhaize, dr. sc.

Title of presentation: Peter Pan Galaxies - Never grow up

Title of paper: Extragalactic peaked-spectrum radio sources at low frequencies

Author: Callingham et al (2017)

Abstract: 
We present a sample of 1,483 sources that display spectral peaks between 72 MHz and 1.4 GHz, selected from the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey. The GLEAM survey is the widest fractional bandwidth all-sky survey to date, ideal for identifying peaked-spectrum sources at low radio frequencies. Our peaked-spectrum sources are the low frequency analogues of gigahertz-peaked spectrum (GPS) and compact-steep spectrum (CSS) sources, which have been hypothesized to be the precursors to massive radio galaxies. Our sample more than doubles the number of known peaked-spectrum candidates, and 95% of our sample have a newly characterized spectral peak. We highlight that some GPS sources peaking above 5 GHz have had multiple epochs of nuclear activity, and demonstrate the possibility of identifying high redshift (z>2) galaxies via steep optically thin spectral indices and low observed peak frequencies. The distribution of the optically thick spectral indices of our sample is consistent with past GPS/CSS samples but with a large dispersion, suggesting that the spectral peak is a product of an inhomogeneous environment that is individualistic. We find no dependence of observed peak frequency with redshift, consistent with the peaked-spectrum sample comprising both local CSS sources and high-redshift GPS sources. The 5 GHz luminosity distribution lacks the brightest GPS and CSS sources of previous samples, implying that a convolution of source evolution and redshift influences the type of peaked-spectrum sources identified below 1 GHz. Finally, we discuss sources with optically thick spectral indices that exceed the synchrotron self-absorption limit.

Link to paper: http://adsabs.harvard.edu/abs/2017ApJ...836..174C <http://adsabs.harvard.edu/abs/2017ApJ...836..174C>
Link to press release: http://www.dunlap.utoronto.ca/new-survey-finds-peter-pan-radio-galaxies-that-may-never-grow-up/ <http://www.dunlap.utoronto.ca/new-survey-finds-peter-pan-radio-galaxies-that-may-never-grow-up/>

If you have recently read interesting astrophysics paper you would like to present, please contact me via e-mail: lceraj at phy.hr <mailto:lceraj at phy.hr>

See you on Wednesday.

Cheers,
Lana




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