Dissertation: Behavior of Low-mass X-ray Binaries and their Formation in Globular Clusters

(Cassiopeia – Autumn/l’automne 2016)

by Arash Bahramian
Thesis defended on June 22, 2016
Department of Physics, University of Alberta
Thesis advisor: Dr. Craig O. Heinke

Low mass X-ray binaries (LMXBs) are systems of compact stellar remnants accreting from a low mass companion star. These systems show various levels of mass transfer on various timescales. Many aspects of accretion in these systems are still not fully understood, specifically the emission processes involved in various states of mass transfer. The population of LMXBs has been found to be orders of magnitude higher (per unit mass) in globular clusters (GCs) compared to the Galactic field. This overabundance has been explained as due to the formation of LMXBs by stellar encounters in GCs. In this thesis, we study GC LMXB populations, and the details of accretion in these systems. First, we focus on the population of LMXBs and the role of stellar encounters in their formation in GCs. We calculate model-independent stellar encounter rates for 124 Galactic GCs, and show that core-collapsed clusters tend to have lower numbers of LMXBs compared to other clusters with similar values of the stellar encounter rate. Then, we focus on studying accretion in LMXBs in various classes of systems (quiescent, transient, ultra-compact and symbiotic). We provide evidence for the presence of low-level accretion in the rise and decay of outbursts in transient LMXBs, and the absence of low-level accretion in many quiescent neutron star LMXBs. Finally we study two peculiar LMXBs, and show that one is an ultra-compact X-ray binary, and another one is a symbiotic X-ray binary.

Dissertation: What Governs Star Formation in Galaxies? A Modern Statistical Approach

(Cassiopeia – Autumn/l’automne 2016)

By Sahar Rahmani
Thesis defended on August 23, 2016
Department of Physics and Astronomy, Western University
Thesis advisor: Dr. Pauline Barmby

Understanding the process of star formation is one of the key steps in understanding the formation and evolution of galaxies. In this thesis, I address the empirical star formation laws, and study the properties of galaxies that can affect the star formation rate.

The Andromeda galaxy (M31) is the nearest large spiral galaxy, and therefore, high resolution images of this galaxy are available. These images provide data from various regions with different physical properties. Star formation rate and gas mass surface densities of M31 have been measured using three different methods, and have been used to compare different star formation laws over the whole galaxy and in spatially-resolved regions. Using hierarchical Bayesian regression analysis, I conclude that there is a correlation between surface density of star formation and the stellar mass surface density. A weak correlation between star formation rate, stellar mass and metallicity is also found.

To study the effect of other properties of a galaxy on the star formation rate, I utilize an unsupervised data mining method (specifically the self-organizing map) on measurements of both nearby and high-redshift galaxies.
Both observed data and derived quantities (e.g. star formation rate, stellar mass) of star-forming regions in M31 and the nearby spiral galaxy M101 are used as inputs to the self-organizing map. Clustering the M31 regions in the feature space reveals some (anti)-correlations between the properties of the galaxy, which are not apparent when considering data from all regions in the galaxy. The self-organizing map can be used to predict star formation rates for spatially-resolved regions in galaxies using other properties of those regions.

I also apply the self-organizing map method to spectral energy distributions of high-redshift galaxies. Template spectra made from galaxies with known morphological type are used to train self-organizing maps. The trained maps are used to classify a sample of galaxy spectral energy distributions derived from fitting models to photometry data of 142 high-redshift galaxies. The grouped properties of the classified galaxies are found to be more tightly correlated in mean values of age, specific star formation rate, stellar mass, and far-UV extinction than in previous studies.

Dissertation: X-ray Populations in The Local Group: Insights with Hubble and Chandra

(Cassiopeia – Autumn/l’automne 2016)

neven vulic

by Neven Vulic
Thesis defended on June 21, 2016
University of Maryland, College Park
Thesis advisors: Dr. Pauline Barmby and Dr. Sarah C. Gallagher

X-ray observations provide a unique perspective on the most energetic processes in the Universe. In particular, Low-mass X-ray binaries (LMXBs) found in globular clusters have been shown to depend on the mass, radius, and metallicity of the cluster. This thesis focuses on the impact environmental parameters have on X-ray sources and the underlying physical explanations for them. I studied the X-ray binary population in M31 using 1 Ms of Chandra ACIS data and 6-filter photometry from the Panchromatic Hubble Andromeda Treasury Survey. From a sample of 83 star clusters we found the brightest and most compact star clusters preferentially hosted an X-ray source. An investigation of 1566 H II regions found that neither radius nor H-alpha luminosity was a predictor of an H II region hosting an X-ray source. To study the faintest X-ray sources a stacking analysis of star clusters and H II regions was completed. Non-detections throughout resulted in upper limits of ~10×1032 erg/s. I produced the most sensitive Chandra X-ray point source catalogue of M31, detecting 795 X-ray sources in an area of ~0.6 deg2, to a limiting unabsorbed 0.5-8.0 keV luminosity of ~10×1034 erg/s. The flatter completeness-corrected X-ray luminosity function of the bulge compared to the disk, consistent with previous work, indicated a lack of bright high-mass X-ray binaries in the disk and an aging population of LMXBs in the bulge. I also investigated the origin of the relationship between the metallicity of 109 Galactic globular clusters and LMXB formation by studying the number density of red giant branch (RGB) stars. A Spearman Rank test between the RGB star density and metallicity [Fe/H] confirmed the data could not have been drawn from a random distribution.

Dissertation: Monitoring Broad Absorption-line Quasar Variability

(Cassiopeia – Autumn/l’automne 2016)

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.

Update from the Canadian Space Agency / Compte rendu de l’agence spatiale canadienne

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)

La version française suit

Canadian Space Exploration Workshop – CSEW 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.

More details are presented on the CSEW webpage. There is no fee to participate, but registration is required. For any questions about the workshop please contact: asc.aces-csew.csa@canada.ca.

English above

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: asc.aces-csew.csa@canada.ca.

Celebrating the History of Radio Astronomy in Canada

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.

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.

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:

Plaskett Postdoctoral Fellowship (Research Associate), NATIONAL RESEARCH COUNCIL of CANADA (NRC)

Herzberg Astronomy and Astrophysics, Dominion Astrophysical Observatory
5071 West Saanich Road
Victoria, BC V9E 2E7
Fax : (613) 990-1286
Telephone: (613) 949-7685
E-mail enquiries: HRQuestionsRH_CG1@nrc-cnrc.gc.ca.

Related URLs: Job Post
Further information on NRC Herzberg can be found here.
Information on the staff and their research interests is available here.
More information on the Fellowship is available here.
Desired starting date: September 2017

The Herzberg Astronomy and Astrophysics portfolio of the National Research Council (NRC) is pleased to announce the 2016 competition for a Plaskett Postdoctoral Fellowship (Research Associate) position tenable at Dominion Astrophysical Observatory (DAO) in Victoria, BC, Canada. The successful candidate will be an outstanding recent doctoral graduate in astronomy/astrophysics who is highly motivated to exploit astronomical facilities administered by NRC and contribute to forefront research projects conducted using those facilities.
This hiring is at the postdoctoral level, but at NRC Canada, this is in effectively a term staff scientist position with all the associated benefits, including paid maternity and parental leave, vacation, accruable pension contributions and others.
We are particularly interested in a candidate who will contribute to one or more of the following research areas:
• Exoplanets and debris disks (direct detection, planetary atmospheres, dynamical evolution, collisional evolution, composition), utilizing Gemini, ALMA, HST, JWST and/or exploitation of existing large survey data from Kepler, Spitzer, Herschel, WISE and other missions. Participation in the Gemini Planet Imager (GPI) Exoplanet Survey, which has both exoplanet and disk components, is a possibility. GPI is also available for PI projects through the general time allocation process.
• Outer solar system bodies (accretion processes, size-frequency distributions, surface properties, orbital dynamics, binaries, space-craft exploration), utilizing CFHT, Gemini, ALMA, HST, Subaru, and the New Horizons spacecraft with possible participation in the Outer Solar System Origins Survey (OSSOS).
• Star or planet formation processes (protostellar evolution, cluster formation, circumstellar disks, super-star clusters in external galaxies), utilizing ALMA, the Jansky VLA, or other facilities, and leveraging results from Herschel, Spitzer, or JCMT legacy programs (e.g., the JCMT Gould Belt Survey).
• Photometric and spectroscopic studies of the structure and stellar content of the Milky Way, Local Group, and other nearby galaxies, including all areas of research associated with the broad field of near-field cosmology.
• Multi-wavelength investigations of galaxies and clusters, including studies of galaxy distances, dynamics, and structural properties; super-massive black holes and galactic nuclei; and star clusters and star formation at UV, optical, IR and sub-mm wavelengths.
• Cosmological evolution of galaxies including physical processes such as accretion, outflow, feedback, metal enrichment, star formation, super-massive black hole growth, mergers, and strong lensing.
Candidates should have an observational background or an interest in constraining theories with observations.
The successful candidate will:
• Conduct original research independently and in collaboration with NRC Herzberg staff members associated with the projects that are most relevant to the fellow’s area of expertise.
• Contribute to the scientific exploitation of NRC Herzberg’s projects, particularly, but not limited to, those that utilize the astronomical facilities and infrastructure administered by NRC Herzberg, such as ALMA, CFHT, and the Gemini Observatory.
• Engage with the astronomical community to advance NRC Herzberg’s mandate to provide astronomical facilities and services to Canadian researchers. In particular, NRC Herzberg is a leading developer of instrumentation for current and future ground- and space-based telescopes (e.g., ALMA, CFHT, Gemini, JWST, MSE, SKA, and TMT) and provides scientific data preservation, distribution, and analysis services. NRC Herzberg also hosts CADC, which is home to the CANFAR cloud computing network, and extensive data archives (including those for DAO, CFHT, CGPS, Gemini, HST, JCMT).
• Share with other postdoctoral research associates the organization of the NRC Herzberg weekly seminar series which runs from September to April.
The initial appointment is of two years duration, which may be extended for one further year (subject to performance and availability of funds). In addition to highly competitive benefits and salary, the Plaskett Fellow will receive support for observing and conference travel, page charges, and access to professionally managed computation infrastructure and resources.
Applicants must have acquired their Ph.D. within the last five years or expect to obtain their degree before taking up the position. Applications should be made by 15 November 2016 via the process described at the URL provided.
NRC is an equal opportunity employer.
Vous pouvez obtenir ces renseignements en français au site web indiqué ci-haut.

Dunlap Postdoctoral Fellowships in Astronomy and Astrophysics

Email Submission Address: fellowships@dunlap.utoronto.ca
Attention To: Prof Bryan Gaensler, Director
Dunlap Institute for Astronomy and Astrophysics, University of Toronto
50 St. George Street, Toronto, ON M5S 3H4 Canada

Email Address for Inquiries: director@dunlap.utoronto.ca

Closing Date for Receipt of Applications: November 1, 2016

Related URLs:
Dunlap Institute for Astronomy and Astrophysics: dunlap.utoronto.ca
Department of Astronomy and Astrophysics: astro.utoronto.ca
Canadian Institute for Theoretical Astrophysics: cita.utoronto.ca
Center for Planetary Sciences: cps.utoronto.ca

The University of Toronto invites applications for Dunlap Postdoctoral Fellowships within the Dunlap Institute for Astronomy and Astrophysics. This growing unit pursues groundbreaking research in experimental astrophysics, in close collaboration with Toronto colleagues in the Department of Astronomy and Astrophysics (DAA), the Canadian Institute for Theoretical Astrophysics (CITA) and the Center for Planetary Sciences (CPS).

Dunlap Fellows are expected to conduct a program of original research either independently or in collaboration with others at the University, and will be offered professional development and mentoring across a range of areas relevant to a scientific career. Exceptional candidates in instrumentation, software, or observation are encouraged to apply. Fellows have access to laboratories, computing clusters and fabrication facilities, and can propose for additional support for their experimental or computational plans. Dunlap Fellows are also strongly encouraged to participate in the Institute’s outreach and training initiatives. The range of activities and opportunities in research, outreach and training can be seen in the annual reports on the Dunlap Institute’s web site.

The Dunlap Institute, DAA, CITA and CPS together host over 130 staff and students in astronomy, who conduct a diverse research program across instrumentation, observation, computation and theory. The Dunlap Institute is located on a beautiful 19th century campus in the heart of one of the world’s great cities. Rated as having one of the highest standards of living in the world, Toronto offers a huge range of indoor and outdoor pursuits, outstanding food and music, and a vibrant and diverse cultural community.

The Dunlap Institute is committed to a flexible and inclusive workplace. We encourage applications from qualified women and men, members of visible minorities, aboriginal peoples, persons with disabilities, and potential two-body hires. Subject to immigration regulations, successful candidates will be given the option to take up their Fellowships as part-time appointments (such a request need not be made as part of a candidate’s initial application).

Appointments are initially for three years, with a subsequent possibility of extension for one further year subject to outstanding performance in public outreach and education activities.. Dunlap Fellowships include an annual salary of CAD $68000 plus generous benefits, a research allowance of CAD $18000 per year, relocation assistance, and the opportunity to request additional research funds from the Dunlap Institute.

The approximate expected starting date is September 1, 2017. Applicants should send a cover letter including a summary of their research program not to exceed 300 words, a curriculum vitae, a publication list, and a statement of research interests not to exceed 3 pages, and arrange to have three letters of recommendation sent to fellowships@dunlap.utoronto.ca by November 1, 2016.

Employment as a Postdoctoral Fellow at the University of Toronto is covered by the terms of the CUPE 3902 Unit 5 Collective Agreement.

This job is posted in accordance with the CUPE 3902 Unit 5 Collective Agreement.

The University of Toronto is strongly committed to diversity within its community and especially welcomes applications from racialized persons / persons of colour, women, Indigenous / Aboriginal People of North America, persons with disabilities, LGBTQ persons, and others who may contribute to the further diversification of ideas.