<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class="">Dear all, <div class=""><br class=""></div><div class="">Astro Journal club starts on Wednesday at 3 p.m. (sharp) in the seminar room F-201 of the Physics Department. </div><div class=""><br class=""></div><div class="">Presenter: Jacinta Delhaize, dr. sc.</div><div class=""><br class=""></div><div class=""><div class="">Title of presentation: Peter Pan Galaxies - Never grow up</div><div class=""><br class=""></div></div><div class="">Title of paper: Extragalactic peaked-spectrum radio sources at low frequencies</div><div class=""><br class=""></div><div class="">Author: Callingham et al (2017)</div><div class=""><br class=""></div><div class="">Abstract: </div><div class=""><div class="">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.</div></div><div class=""><br class=""></div><div class=""><div class="">Link to paper: <a href="http://adsabs.harvard.edu/abs/2017ApJ...836..174C" class="">http://adsabs.harvard.edu/abs/2017ApJ...836..174C</a></div><div class="">Link to press release: <a href="http://www.dunlap.utoronto.ca/new-survey-finds-peter-pan-radio-galaxies-that-may-never-grow-up/" class="">http://www.dunlap.utoronto.ca/new-survey-finds-peter-pan-radio-galaxies-that-may-never-grow-up/</a></div><div class=""><br class=""></div></div><div class="">If you have recently read interesting astrophysics paper you would like to present, please contact me via e-mail: <a href="mailto:lceraj@phy.hr" class="">lceraj@phy.hr</a></div><div class=""><br class=""></div><div class="">See you on Wednesday.</div><div class=""><br class=""></div><div class="">Cheers,</div><div class="">Lana</div></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div></body></html>