By Jesse Rogerson
Thesis defended on April 18, 2016
Department of Physics and Astronomy, York University
Thesis advisor: Dr. Patrick Hall
Winds generated by an accreting super massive black hole may provide feedback to the host galaxy and offer an explanation for the co-evolution of galaxies with their super massive black holes that has been reported in the literature. Some outflows are manifested as broad absorption line (BAL) troughs in quasar spectra, and are measured at velocities as high as ~60,000 km s−1 at ultra-violet wavelengths. These BAL troughs have been observed to vary on both long (years) and short (weeks) rest-frame time-scales and can emerge in a quasar that had none, or disappear completely. By monitoring the variability of absorption in BAL quasars, constraints can be placed on outflow models and the structure of quasars in general.
In this study, we isolate a set of quasars that exhibit emergent CIV BALs in their spectra, by comparing archival data in the SDSS Data Release 7 to the BOSS Data Release 9 and 10. After visually defining a set of emergent BALs, follow-up observations were obtained with the Gemini Observatory for 105 quasars. BALs were formally detected in all but two of the quasars in the dataset, and we report 219 absorption complexes in the entire set. After a BAL has emerged, we find it is equally likely to continue increasing as it is to start decreasing in a subsequent observation. Based on the range of time between our observations, this indicates the coherence time-scale of BALs is less than 100 days. There is a strong signal of coordinated variability among two troughs in the same quasar. Further, coordination is stronger if the velocity separation between the two troughs is smaller. We conclude the variability is likely due to changes in the ionizing flux incident on the absorbing cloud, which agrees with the results of Filiz Ak et al. (2013).
In this work we also test two competing models of BAL variability (bulk motion and ionization changes) in the context of a case study of the quasar SDSS J023011.28+005913.6, which had two high-velocity emergent troughs. Both models yield plausible results.
From/de Denis Laurin, Senior Program Scientist/Scientifique principal de programme, Space astronomy, Space Exploration development/Développement d’exploration spatiale, CSA/ASC (Cassiopeia – Autumn/l’automne 2016)
The CSA will host a consultation workshop on November 24-25 in downtown Montreal to update the space sciences priorities, looking at opportunities for the next decade and beyond. This includes space astronomy, planetary exploration and space health disciplines. Ideas will be welcomed from the community (academia & industry) to help shape future of Canadian space activities. The workshop is a forum for the current space exploration Topical Teams (described in Cassiopeia March 2016) to present and discuss their interim results.
Participation by a broad representation of the community in space sciences is thus important to ensure that the set of objectives of the Canadian Exploration communities are being fully and accurately captured.
Atelier canadien sur l’exploration spatiale – ACES 2016
L’ASC offrira un atelier de consultation le 24 et 25 novembre au centre-ville de Montréal afin de mettre à jour les priorités en sciences spatiales, revoir les opportunités pour la prochaine décennie et au-delà. Cela comprend l’astronomie spatiale, l’exploration planétaire et de la santé dans l’espace. Des idées seront échangées par la communauté (les universités, l’industrie) pour aider à façonner l’avenir des activités spatiales canadiennes. L’atelier est un forum pour les Équipes thématiques en exploration spatiale actuelles (tel que décrites dans le numéro Cassiopeia mars 2016) pour présenter et discuter leurs résultats intermédiaires.
La participation d’une large partie de la communauté directement concernée par les sciences spatiales est donc importante pour faire en sorte que leurs objectifs soient pleinement et correctement entendus.
Plus de détails sont présentés sur la page Web CSEW. Il n’y a pas de frais pour participer, mais l’inscription est obligatoire. Pour toutes questions concernant l’atelier, contacter: email@example.com.
By/par Tim Robishaw, DRAO (Cassiopeia – Autumn/l’automne 2016)
A workshop on the history of Canadian radio astronomy was held July 25 and 26 at the Dominion Radio Astrophysical Observatory (DRAO).
Workshop participants under the John A. Galt 26-m telescope.
Workshop participants under the John A. Galt 26-m telescope.
Nametags of workshop participants were customized with telescopes and observatories from their past.
A major motivation for the event was the work of the late Richard Jarrell (York University), the author of “The Cold Light of Dawn: A History of Canadian Astronomy”. Richard collected an extensive archive on the history of Canadian radio astronomy, including many interviews with all the original players. Richard had just begun writing a book on this topic at the time of his passing in late 2013. A group of Canadian radio astronomers hopes to finish writing this book following the outline Richard provided and using his archival material. To this end, in addition to topics of worldwide importance to the history of radio astronomy, contributions were solicited on topics pertaining to the development of radio astronomy in Canada. Richard’s wife, Martha, attended the workshop and hand-delivered Richard’s archives and interviews to DRAO where they will be housed.
The workshop included 27 talks covering a breadth of stories about the development of radio astronomy at Canada’s universities and observatories. The nearly 50 attendees took part in a discussion about practicing history led by Woody Sullivan (University of Washington), Miller Goss (NRAO)—both active historians of radio astronomy—and NRAO Archivist, Ellen Bouton.
A website containing videos of the talks and photos from the workshop can be found here. And thanks to Joseph Fletcher (NRC, retired) and Bob Hayward (NRAO, retired), we now have video of a 1987 NRC workshop entitled “Radio Astronomy and Canada: Fifty Years of Progress”. These videos can also be found at the above website.
If you prefer to view the videos directly, the Youtube links to the workshop playlists are below: