Astronomy Seminars at CFHT
October,26 2017, at
Harvey Richer (University of British Columbia)
Abstract:The James Webb Space Telescope is a 6.5 meter diameter telescope that is optimized
for infrared wavelengths (~1 to ~30 microns). In the 1-2 micron regime it will reach a
limiting flux density in a time that is about 100 times shorter than Gemini.
The impact of the telescope on all aspects of astronomical research will be
enormous including that related to globular star clusters. In this presentation I will
discuss a few areas where it will be particularly powerful in exploring globular
cluster science including a search for possible ancient planets.
"How the James Webb Space Telescope Will Impact Globular Star Cluster Science"
October,26 2017, at
Chris Mann (University of British Columbia)
Abstract:Stellar mass black holes (a few tens of Msun) resulting from end-stage stellar evolution and supermassive black holes (10^6 - 10^9) found in the cores of most galaxies are well established in the observational literature. What are conspicuously absent are detections of black holes with mass between these two extremes. Intermediate mass black holes (IMBHs) in the range of 10^3 - 10^5 Msun have yet to be conclusively discovered, but their proposed formation mechanisms imply that the dense stellar environments in the cores of globular clusters are a good place to look for them.
Our study searches for the kinematic signature of an IMBH in the core of the globular cluster 47 Tucanae. We utilize ultraviolet HST photometry to produce proper motion data for ~50,000 stars in the cluster core. By comparing the velocity dispersions profile of the cluster to theoretical Jeans-derived models and N-body simulations, we detect the influence of a modestly-sized IMBH. Our current estimate for the IMBH mass is something like 2500 +/- 1000 Msun, though our model is undergoing continuous adjustment.
"A Kinematic Search for an Intermediate Mass Black Hole in 47 Tucanae"
October,12 2017, at
Harvey Richer (University of British Columbia)
Abstract: When I was in graduate school, the most boring aspect
of my education was doing stellar astrometry - the positions and motions
of the stars. This to me sounded like very old fashioned astronomy. All that
has changed in recent years and astrometry has become one of the most
exciting fields in astronomy today. In this presentation I’ll talk about some
of our recent results in globular star cluster research that depend sensitively
on accurate astrometry.
"How I learned to love proper motions"
October,11 2017, at
Abstract:Massive stars strongly influence their immediate surroundings during their lifetimes (via e.g. protostellar jets, strong stellar winds, ionising radiation, supernovae). On larger scales, feedback from massive stars regulates the formation and evolution of entire stellar clusters and dominates the mass and energy cycle in star-forming galaxies like the Milky Way. Qualitatively, the effect of massive stars on their environment is well understood, but a solid quantitative, observational analysis is still missing. The results of recent feedback observations of a variety of structures and environments within massive star-forming regions will be shown, carried out with the integral field spectrographs MUSE and KMOS at the Very Large Telescope. I will discuss the advantages (and caveats) of integral field spectroscopy in tracing and quantifying feedback from massive stars, and describe the bigger picture that connects feedback on small (cloud) scales to that on large (galactic) scales.
"Tracing feedback in massive star-forming regions with integral field spectroscopy"
October 5, 2017, at
Andreea Petric (IfA/CFHT)
Abstract:Observations of the dynamics of stars and gas in the nuclear regions of nearby galaxies suggest that the overwhelming majority of spheroidal galaxies in the local Universe contain massive black-holes (BH) and that, with some important caveats, the masses of those central BH correlate with the velocity dispersion of the stars in the spheroid and the bulge luminosities. Much research has been dedicated to understanding the mechanisms responsible for such a fundamental - perhaps causal - relation. An accurate census of the basic properties of the cold interstellar medium (ISM) in galaxies with accreting super-massive black holes at their centers, i.e. galaxies that host active galactic nuclei (AGN), is pertinent to those investigations because cold molecular gas fuels both black hole growth and star-formation.
We present high sensitivity observations taken with the Herschel Space Observatory to estimate the cold ISM content in a sample of ~200 nearby,optically luminous QSOs. The cold ISM properties of these luminous AGN are discussed in the context of models that envision that quasar activity is triggered by gas-rich galaxy mergers. We also present infrared spectroscopic and photometric observations of a sample of ~200 nearby, Luminous Infrared Galaxies (LIRGs). Luminous Infrared Galaxies (LIRGs) make stars and grow super-massive black holes (SMBH) at a faster rate than most of their local counterparts. Their number density increase with redshift until z~1 when they dominate galaxy evolution. Some are mergers, some are not, some are feeding the central SMBH, others may not be. Because of this, LIRGS constitute a perfect laboratory to observe and study how galaxies grow and to test the conditions in which gas rich mergers trigger episodes of growth for the central SMBH and the host galaxy.
"The Care and Growth of Super Massive Black Holes"
October,4 2017, at
Laurent Drissen (L'Universite Laval)
Abstract:SITELLE, CFHT's Imaging Fourier transform spectrometer, has been in place for two years now.
In this talk, I will present SITELLE's history, very briefly describe how it works, and highlight some
of its scientific capabilities.
"A brief history of SITELLE"
September 27, 2017, at
Clare Higgs (University of Victoria)
Abstract:The Solo (Solitary Local) Dwarf Galaxy Survey is a volume limited sample of all nearby (< 3 Mpc) and isolated ( > 300 kpc from the Milky Way or M31) dwarfs, with wide-field g and i imaging. This survey uses resolved stellar populations to parameterize these low mass systems. Comparison to the well studied satellite dwarfs characterizes the evolutionary impact of a large galaxy in close proximtity. The deep, wide field nature of this survey also lends itself to searching for substructure around these dwarfs, both globular clusters and possible faint satellites. I present a subset of Solo dwarfs, which lie within the virial radius of the Local Group. This sample has been characterized using consistent methods, despite their diversity in mass and size. The analysis focuses on extended faint stellar structure, stellar populations and morphology. We intend to use this subset to examine trends with star formation history, and separation from a large host. This first subset emphasizes both the unique challenges and advantages of this survey. The Solo Survey provides detailed look at the extended structure of dwarfs and helps to characterize the evolution of galaxies in the faint limit.
"Solo Dwarf Galaxies in the Local Group"
August 30, 2017, at
Simon Petrus (University of Grenoble)
Abstract:Luminous Infrared Galaxies (LIRGs) make stars and grow super-massive black holes (SMBH) at faster rates than most of their local counterparts. Their numbers increase with redshift, until about a redshift of 1.Their numbers increase with redshift, until about a
redshift of 1 when they dominate galaxy evolution. Some are mergers,
some are not, some are feeding central SMBH, others may not. Because
of this, LIRGS constitute a perfect laboratory to observe and study
how galaxies grow. The main fuel for this growth is molecular gas,
and the aim of my internship was to study this gas. Out of a sample
of ~200 LIRGs, 10% appear to have more molecular gas at the center
relative to IR and other coolant emission. We followed seven of
those LIRGs with Gemini's Near-Infrared Spectrograph (GNIRS). I
measured the mass and kinematics of their warm molecular gas and
found that all might have bulk flows, associated with massive
star-formation in the central region. I estimated extinction free
star-formation rates using Hydrogen recombination lines and looked
for evidence of shocked gas as from [Fe II] emission. I will also
talk about my opportunity to do classical observing from the
glorious top of Maunakea, at Subaru's telescope. During this night
Andreea Petric, Jameeka Marshall and I, observed a recent Active
Galactic Nuclei activation to study the impact of this awakening on
the Interstellar Medium of its host galaxy.
"Molecular Gas in Luminous Infrared Galaxies"
August 14, 2017, at
Olivia Lim (University of Montreal)
Abstract:SPIRou is a near-infrared spectropolarimeter and high-precision
velocimeter expected to be installed at CFHT at the end of 2017. It is mostly
dedicated to the search and characterization of exoplanets orbiting low-mass
stars such as M dwarfs. In this context, it is important to not only select
the right candidates to observe but also to better understand how their
activity can affect the observations. In this talk, I will present the two
projects I have been working on this summer. The first part of the
presentation will focus on the project at CFHT, supervised by Pascal FouquÃ¯Â¿Â½.
This project aims at confirming and ruling out binary and multiple systems
made of at least one M dwarf to avoid observing such systems with SPIRou and
also to determine the occurrence of multiplicity among M dwarfs. I will
present an automated procedure that first, detects possibly false binaries or
multiples, and second, could verify if other systems are bound. The second
part of the presentation will be on the project in Montreal, supervised by
Lison Malo. The goal of this project is to measure the magnetic field in
M dwarfs to better filter out activity signals from spectra that will be used
to search for exoplanets. I will briefly present our latest results along
with comparisons to measurements obtained by different methods.
"Preparing for SPIRou: Binaries and magnetic fields in M dwarfs"
July 24 2017, at
Meg Schwamb (Gemini Observatories)
Abstract: Planet Four and Planet Four: Terrains
are citizen science projects mining Mars
Reconnaissance Orbiter mages to explore how the south pole of Mars is
sculpted by the never-ending cycle of freezing and thawing of exposed
carbon dioxide ice. In the summer, carbon dioxide geysers loft dust and
dirt through cracks in the thawing carbon dioxide ice sheet to the
surface where winds blow the material into the hundreds of thousands of
dark fans observed from orbit. Planet Four enlists over 136,000
volunteers to map the sizes, shapes, and orientations of these fans in
HiRISE images. Planet Four is creating an unprecedented wind map of the
south pole of Mars in order to probe how the Martian climate changes over
time and is impacted year to year by dust storms and and other
global-scale events. Planet Four: Terrains, aims to study the
distribution of the geyser process across the south pole and identify new
targets of interest for HiRISE. Over 12,000 people have helped identify
the channels and pits (dubbed araneiforms) carved during the geyser
formation process. In this talk, I'll give an overview of Planet Four and
Planet Four: Terrains and present the latest results from these projects.
"Exploring Mars with 150,000 Earthlings"
May 2017, at
Calen Henderson (JPL)
The past three years have witnessed a revolution in microlensing searches for exoplanets. Spitzer campaigns in 2014, 2015, and 2016 have transformed space-based microlensing observations from a novelty to an industry. Campaign 9 of Kepler's extended K2 mission conducted the first automated microlensing survey from the ground and from space. These endeavors facilitate measuring a key observable known as the satellite parallax, which leads to model-independent mass measurements for the lensing systems and opens a new window for astrophysical exploration. I will discuss the scientific methodology and utility of these missions, highlight several key results, and emphasize the preparatory work for and expected yields of the WFIRST microlensing survey.
"Space, the Next Frontier: Exoplanetary Microlensing in the era of Spitzer and K2 with an eye toward WFIRST"
January 19 2017, at
Elodie Hebrard (York University)
Abstract: The detection extra-solar planets through radial-velocity searches
is likely limited by the intrinsic magnetic activity of the host stars. The
correlated magnetic noise that arises from their natural radial-velocity
variability (jitter) can easily mimic and hide the orbital signals of
super-Earth and Earth-mass exoplanets.
The modeling of the RV jitter is thus essential to extrasolar planets searches.
I will present here a technique we can use to filter out the RV activity
jitter of low-mass star as well as what we currently know about the magnetic
field of cool stars
"The magnetic personality of stars"
Seminars at other Institutions operating on Mauna Kea and the Big Island:
List of recent past seminars at CFHT.
E-mail correspondence to Andreea Petric: (Petric (at) cfht (dot) hawaii (dot) edu) who coordinates the seminars.