Astronomy Seminars at CFHT
Due to the
Corona Virus Outbreat we will be having Virtual Seminars
May 12th, 2020, at 3 pm
Nicolas Flagey (CFHT)
"Carbon emissions at CFHT first step to a more sustainable observatory"
As the crisis of climate change affects more people every year and lead
to more severe weather patterns with unprecedented socio-economical
consequence, all actors on the planet need to understand their
responsibility and contribute to solving this generational problem. The
Canada-France-Hawaii Telescope (CFHT) Corporation is willing to tackle
the issue, but we first need to assess the carbon footprint of the
company and lay the groundwork for the future implementation of
significant changes required to reduce that footprint. We follow the
method suggested by the CarbonBuddy tool to breakdown the greenhouse gas
(GHG) emissions of various activities at CFHT for the entire year of
2019: travel in and out of state, electricity and other sources of
The total GHG emissions amount and its breakdown will be shown. We show
that significant improvements have occurred in the recent past at CFHT,
with the installation of solar panels and a remarkable reduction in
electricity consumption at headquarters. We list suggestions to further
decrease the GHG emissions in the short to long term: offset current
emissions by supporting local projects, investing in more efficient equipment,
and establishing environmentally friendly habits.
The fundamental work presented in this paper will facilitate the
official planning at CFHT for a drastic reduction in GHG emissions with
the goal to meet the objectives laid out in the 2015 Paris Accord. It
will also support the design of the Maunakea Spectroscopic Explorer
(MSE), the future transformation of CFHT, and allow the project to seize
this opportunity and incorporate the fight against climate change as one
of its core missions. By choosing to implement those changes, CFHT and
MSE can become part of the solution to climate change and lead the way,
locally and in the world of astronomy.
May 6th, 2020, at 11 am
Carter Rhea (University of Montreal)
"A Machine Learning Approach to SITELLE Spectral Analysis"
Machine learning is rapidly becoming another tool in an astronomers statistical toolbox. However, due to the increasing complexity of machine learning algorithms, their exact nature has been shrouded in jargon which has lead to the popular belief that these techniques are simply black boxes. This notion has also spawned a certain, and dangerous, level of carelessness with the input and expected output of the algorithms. In this talk, I will discuss a common paradigms in machine learning -- supervised learning -- through the lense of a popular algorithm: a Convolution Neural Network. We will then explore the applicability of this algorithm to the SIGNALS program spearheaded by Laurie Rousseau-Nepton at the CFHT using the new iFTS instrument SITELLE. Applying the technique to a dynamic region of M33 reveals the strengths (and weaknesses!) of such an approach.
April 9th, 2020, at 11 am
Rebecca Minsley, (Bates College)
"Molecular Gas Heating and Modified Dust Properties in Active Galaxies: Growing Black Holes or Tidal Shocks?"
Please join us for this Virtual Seminar at this zoom link: https://cfht.zoom.us/j/3900698962
We investigate if and how growing super-massive blask holes (SMBH) known as Active Galactic Nuclei (AGN) and
gravitations interactions affect the warm molecular gas and dust of galaxies. Our analysis focuses on the
morphologies and warm ISM properties of 630 galaxies at z < 0.1. We use grizy images from the Pan-STARRS survey to
classify the galaxies into mergers, early mergers, and non-mergers. We use MIR spectroscopic measurements of emission
from rotational H_sub2 transitions, dust and PAH features, and silicate emission or absorption lines at 9.7 um to study
how gravitational interactions impact the warm ISM in AGN and non-AGN hosts.
We find that in AGN-hosts, the ISM is warmer, the rations of H_sub2 to PAHs are larger, the PAH emission line ratios
and silicate strengths have a wider range of values than in non-AGN hosts. We find some statistical differences
between the H_sub2 emission of mergers and non-mergers, but those differences are less statistically significant
than those between AGN and non-AGN hosts.
Our results do not establish a relation between the rate of BH growth and the warm ISM but point to highly
statistically significant differences between AGN hosts and non-AGN hosts, differences that are not present with
the same statistical signficance between mergers and non-mergers. We speculate that the combination of triggereing
mechanisms, AGN orientations, and evolutionary stages that allow AGN to be classified as such in the MIR indicate
that those AGN are energetically coupled on kpc scales to their host galaxies' warm ISM. Future optical and IR,
spatially resolved spectroscopic studies are best suited to characterize this connection.
Link to PDF
March 6th, 2020, at 11 am
Sankalp Gilda, (University of Florida)
"deep-REMAP: Probabilistic Parameterization of Stellar Spectra Using Regularized Multi-Task Learning"
In the era of exploding survey volumes, traditional methods of spectral analysis are being pushed to
their limits. For efficient stellar characterization, there is a dire need for accurate synthetic spectral
libraries and automated, interpretable analytical techniques. In this paper, we develop a novel deep
learning framework--deep-Regularized Ensemble-based Multi-task Learning with
Asymmetric Loss for Probabilistic Inference(deep-REMAP)--and demonstrate its effectiveness
in predicting stellar atmospheric parameters of observed spectra. Specifically, we train our deep
convolution neural net-work on PHOENIX synthetic grid, fine-tune it on a subset of MARVELS observed
spectra of FGK dwarfs, and use it to predict the three main stellar atmospheric properties, effective
temperature (Teff), surface gravity (log g), and metallicity([Fe/H]) for FGK giant candidates. To
incorporate MARVELS instrumental and observational peculiarities as part of the training, we augment
PHOENIX spectra with realistic signatures. When validated on a small subset of MARVELS calibration
stars, the fine-tuned model is again able to faithfully recover observed parameters and their respective
uncertainties, thus demonstrating effective application of transfer learning. While deep-REMAP was
trained on the PHOENIX synthetic grid for use with MARVELS observed spectra, it can be easily extended
to work with other synthetic spectral libraries, expanded wavelength ranges, and higher resolution
spectral surveys covering a wider range of stellar properties, including detailed elemental abundances.
Twenty first century is the era of big data. Astronomy is no exception to this trend. This
decade alone will add more data to our corpus of stellar and sub-stellar objects than can
be realistically analyzed by manual labor (aka underpaid graduate students). In this talk,
I will demonstrate how astronomers can leverage advances in deep learning to study stars
faster, better, and more precisely. Specifically, we will consider stellar spectra: just
like a beam of light passing through a prism gets split into seven visible colors, light
from stars gets absorbed by atoms, molecules, and ions in their atmospheres, in a unique
way that lets us characterize the intrinsic properties of their atmospheres. This is very
similar to how a person's fingerprints can help us identify them (almost) uniquely. I will
show the advantages of using an automated, data-driven model over the traditional, human-driven
way of deriving stellar atmospheric properties, and how incorporating the latest practices
from machine learning can accelerate this process. Rapid characterization of stars in this
manner will also assist in characterization of exo-planets orbiting them, bringing us that
much closer to finding Earth 2.0.
November 22nd, 2019, at 11 am
Jean-Charles Cuillandre (CEA Saclay / Observatoire de Paris), Stephen Gwyn (NRC HIA), Mike Hudson (University of Waterloo)
"CFIS: Survey, Dataset, and Science"
The Canada-France Imaging Survey enables a slew of scientific investigations in the fields
of galactic archeology and weak gravitational lensing. The key is synergies with existing
rich all-sky photometric datasets such as Gaia and PS1, or spectroscopic, such as Segue and
BOSS/eBOSS. We describe the nature and status of the CFIS now associated with Pan-STARRS to
build the Ultraviolet Near-Infrared Optical Northern Survey, UNIONS, an unprecedented effort
rooted in photometric needs for the Euclid space mission. UNIONS will become a lasting legacy
for the international community for decades to come by providing the deepest multi-wavelength
extended coverage ever produced of the northern sky. The three speakers will cover
respectively: survey and context (Jean-Charles), description of data processing pipeline
(Stephen), and on-going science within the UNIONS collaboration (Mike).
November 19th, 2019, at 10:00 am
Tracy Webb (McGill University)
"The Growth of the Most Massive Galaxies in the Densest Regions of the Universe"
October 28th, 2019, at 11:30 am
Harvey Richer (University of British Columbia)
"Searching for Very Massive White Dwarfs with Gaia"
We have used the Gaia DR2 release to search for massive white dwarfs in the
direction of young open star clusters. All
204 clusters within 1 kpc and with an age
less than 160 Myrs were searched for
white dwarfs. Ten new candidate cluster
white dwarfs were found and about seven
look like cluster members. I'll discuss these
and their implication for the supernova
rate, the late stages of stellar evolution and the upper limit to white dwarf production.
Stars form together and tend to follow a strict recipe known as the initial mass function, you make a few big and lots of tiny (smaller than the sun ones). White dwarfs are burned out stars that have exhausted their fuel and can be used as a way to estimate the age of the population of stars they live in. Knowing the ages of a population you can also infer how many supernova you might detect.
October 25th, 2019, at 11 am
Hugo Ninou (Ecole Normale Superieure de Paris)
"Defects Detection in SITELLE Images Using Convolutional Neural Networks"
Defects such as satellite trails or cosmic rays in SITELLE images are
quite damaging to the overall data analysis. Indeed, one satellite trail
in one of the images of a cube will affect the spectrum of the stars on
its path. As SITELLE generates a lot of images, being able to
automatically detect their defects is crucial. Convolutional neural
networks are well suited for image recognition and can be put at use for
such a job. During my internship, I focused on building a large enough
dataset for a machine learning algorithm to train on and on tuning the
network's parameters to get the best results as possible.
One way to fix data is to have a human look at every frame, search for issues like satellite trails, mask those features out, replacing them with something suitable were suitable depends on the particular frame. This methode benefits from a human's keen eye and suffers from the same human's possible errors. The human learns from such possible errors. Computer codes can also learn, fail, and thus learn some more. One way to do this is through a kind of process that happens in the human brain, particularly the visual cortex. Our little neurons are responsible for only a tiny bit of our visual field, so they don't get overwhelmed by the universe's beauty. This restricted region is known as the "Receptive field". David Hubel & Thorsten Wiesel figured out that we have receptive fields that respond best when the stimulus is of a certain shape, has a given orientation and/or moves in a given direction.
In the figure, we see a very exciting TV show of a green square that moves to the right. When the green square moves to the right a part of the brain watching the TV show gets super activated. In this analogy the exciting TV show of a moving green square is a satellite trail in SITELLE data and your neurons a code that has nothing else to do but find those trails.
All your code has to do is to assign importance (score) to certain features in the image that may be satellite trails and learn to pick them out. To make this process easier here comes convolution. An image is a matrix (X by Y pixels). One way to think of convolution is as smoothing: if you smooth an image you lose the tiny details and keep the important shape structures. So images are convolved to pick out the relevant features in it.
We look forward to Friday's talk to learn more about this exciting technique and how we rid beautiful Sitelle images of satellite trails.
July 23rd, 2019, at 11 am
Emma Bordier (Observatoire de Paris)
"Characterization and Identification of Circumstella Nebulae with Far-infrared and Sub-millimeter Spectro-Imaging Observations"
Evolved and massive stars are significant contributors to the ionizing photons reservoir and kinetic energy
injected in the interstellar medium (ISM) through their intense stellar winds and radiation. They are generally
dust-rich, and form an important step in the evolutionary cycle of baryonic matter that drives our galaxy
evolution, for which dust is an important tracer. The intense mass outflows form a circumstellar nebulae of
ejected material around the progenitor. Estimating the rates of dust and gas injected into the ISM requires
knowledge of the nature of concerned objects.
Abstract: Over the last decades, identification and characterization of new circumstellar shells has been
facilitated thanks to the advent of high spatial resolution and highly sensitive mid-infrared surveys combined
with optical and near-IR spectroscopy to constrain the nature of the central progenitors. Along lines of sight
with high extinction, IR spectro-imaging is a very reliable way to identify and characterize compact envelopes.
In this presentation, I will focus on more than 400 compact circumstellar shells that have been discovered at
24um thanks to the MIPSGAL Survey of the Galactic plane performed with the Spitzer Space Telescope. Only a
small fraction of these nebula had been identified and spectroscopic follow-up observations from the visible
to the far-infrared have been executed in order to identify as many of these objects as possible. A set of 35
MIPSGAL have been observed with the Herschel/PACS and SPIRE far-IR to sub-mm spectro-imaging instruments. These
observations have allowed me to constrain the physical properties of the envelopes and propose identifications
for their inner stars by analyzing the neutral, ionized, and molecular gas emission in addition to the dust
I'll present three main results which lead to a first identification and characterization of the 35 circumstellar
shells. The spectral gas features are used to derive line flux maps and build CO excitation diagrams. I'll show
simple diagnostics that use the line integrated fluxes or dust continuum, giving reliable clues on the nature of
the inner stars. I'll use these results to report on the ongoing efforts to characterize and identify the
circumstellar envelopes as well as their luminous central stars, especially the third of the shells in our sample
that had never been studied previously.
May 15th, 2019, at 11 am
Todd Boroson, (Director, Las Cumbres Observatory)
"Building the Infrastructure for Time Domain Astronomy in the LSST Era"
Las Cumbres Observatory (LCO) has built, and now operates a global network of robotic telescopes designed for time domain astronomy observations. 'Time domain astronomy' refers to the study of objects in the universe that change detectably on human timescales. Such objects include transients, like supernovae and TDEs (stars sucked into black holes); objects that change in brightness or radial velocity, such as variable and binary stars, stars with transiting planets, and quasars; and objects with detectable motion, like comets and asteroids. These changes demand multiple observations, made at different times, to understand the physics of the processes that cause them.
With the advent of many new surveys that detect time variable phenomena, culminating soon in the LSST project, the requirements of doing time domain astronomy affect how we observe. Some studies require observations continuously or on a cadence, others require a rapid response, still others require real-time decision making. LCO is engaged in two projects to provide new capabilities for time domain astronomy, particularly in the coming era of LSST operations. AEON, the Astronomical Event Observatory Network, is the integration of a number of research telescopes into a single network, able to carry out the complicated sequences of observations for multiple time domain projects in a coordinated way. Current members are LCO, SOAR, NOAO (specifically the Blanco telescope in Chile), and Gemini. The second project is called the TOM Toolkit. This is a software framework that allows a scientist to create a system that will manage a large time domain project, including collecting sample objects from a survey alert stream, triggering requests for follow-up observations, and collecting and organizing all the data.
This presentation will describe these two projects, their current status, and how the particular mission and capabilities of LCO inspired them. I will also talk about future evolution that is envisioned for time domain research and the facilities that support it.
May 14th, 2019, at 11 am
Dhurv Bisaria (Queen's University)
"The Study of the Spatially - Resolved HII Regions of M33 with SITELLE at CFHT"
Understanding the relationships between HII region parameters is important for determining the
extent to which local versus global mechanisms impact the star formation process. We present a
photoionization analysis of the emission from the ionized gas surrounding star forming regions
in M33. With a mosaic of four fields (4 x 11'x11') of the SITELLE Imaging Fourier transform
Spectrometer at CFHT, we observed most of the galaxy disk and its HII regions. We obtained
the flux maps in O II, H-beta, O III, H-alpha, N II, and the SII doublets, and used the
Astrodendro package on the emission maps to identify individual H II regions. Then, we
compared those flux maps with photoionization models using the NebulaBayes package, which
uses a Bayesian approach over a grid of photoionization models to extract the metallicity (Z),
ionization parameter (U), and pressure (P/k) of individual pixels. Abundances (Z, U, P/k) are
plotted against flux, velocity dispersion, and galactocentric distance. In this contribution,
we will present the SITELLE maps and HII region parameters and discuss their implications for star
April 30th, 2019, at 11 am
Axel Guinot (CEA)
"Presentation of ShapePipe, first results on CFIS/UNIONS"
The Canada-France Imaging Survey (CFIS) is a new wide-field survey. It will cover around 5000 deg^2 in the u and r-band in the northern hemisphere with a really good image quality, seeing ~0.6 arcsec for the r-band. Although, the recently collaboration with Pan-STARRS will provide information in g, i and z-band in order to derive photometric redshifts. Those characteristics makes it extremely interesting for weak-lensing analysis. In this framework we start developing a new shape measurement pipeline, ShapePipe, incorporating state-of-the-art technics.
In this talk I will present the first version of ShapePipe and detail some methods used like the metacalibration allowing us to get the shear bias without simulation. I will present as well validation tests and preliminary science results obtain on the CFHTLenS' W3 area of this new dataset.
As weak-lensing studies although require redshift information I will present a cluster-z method planed to be used on CFIS. I will show preliminary results on simulation with this algorithm.
Our current understanding of gravity is that it bends space and time. This means that light from a source galaxy/star/hot potato is not straight but instead can be deflected by a mass because that mass changes the space-time continuum. This is called gravitational lensing. Studying gravitational lenses, therefore, tells us about the mass distribution in the universe which in turn tells us about the Universe' composition and evolution. A big part of this process involves comparing high-quality images (like CFIS will get) with theoretical expectations. To best extract information from those images, you can break them up into component shapes like say your face has a nose, eyes, and other components. There are many ways to figure out the components of an image and this talk will focus on the method employed by CFIS. (Image credit: Original image by NASA, ESA/Hubble & L. Calcada - Image title: Gravitational lensing in action / HST )
April 11th, 2019, at 11 am
Luc Arnold (Observatoire de Haute Provence)
"I: The Earth as an Exoplanet, II: A Virtual Tour of the SOPHIE Spectrograph at T193"
Abstract: I: Detecting an Earth-twin in the HZ of its Sun-like stars by radial velocity (0.1 m/s), direct observing of an Earth-twin as a single dot orbiting its Sun-like star (contrast 1 e-11 in the visible),or probing its atmosphere during a transit (1 e-4 depth) are not et within reach. But direct imaging or RV techniques are continuously improving, and detections of Earth-sized planets around close dwarf stars are promising regarding the possibility of direct imaging or atmospheric characterization. Over the last few years, we conducted two observing programs aimed at characterizing our Earth seen as an exoplanet. First we observed Earthshine on the Moon to obtain a spectrum of the light reflected by the Earth, equivalent to observe the disk-average of the Earth, showing it as a single pale blue dot with the absorption features of oxygen (a biogenic species in the Earth atmosphere). ozone, water vapor, and also the signature of land vegetation. Secondly, we observed lunar eclipses. A lunar eclipse seen from the Earth is a solar eclipse if seen from the Moon: the Earth eclipses the Sun and the Earth atmosphere interacts with sunlight before it reaches the lunar surface. Hence the colorful Moon we enjoy from Earth during a lunar eclipse. The spectroscopy of lunar eclipses therefore gives access to the Earth atmosphere transmission spectrum. We were able to measure the Earth radius versus wavelength (visible range) with SOPHIE, HARPS, and UVES at high spectra resolution to fully characterize the signature of Earth seen as a transiting exoplanet. Again, we could detect oxygen, ozone and water vapor in the Earth's atmosphere. These observations help to validate models and prepare future instruments.
II: SOPHIE is a fiber-fed spectrograph in operation at the Cassegrain focus of the 193cm OHP telescope. I will present the main SOPHIE upgrades done since the start of operations in 2006: new guiding software, continuous LN2 cryostat filling, octagonal fibers, improved thermal control, new calibration unit, and implementation of a Fabry-Perot etalon. The current SOPHIE spectrograph is very stable and shows 1.5m/s RMS residuals on reference stars over the long term. All these upgrades ultimately contributed to the recent announcement of Gl411b last February, the planet with the smallest RV semi-amplitude SOPHIE ever detected (1.6 m/s). Gl411b is the third closest low-mass exoplanet discovered to date.
Ever since Earthlings looked up and dreamed of the twinkling lights in the night sky, some thought there might be some Earth-like siblings floating, spinning, watching the night sky. Some of those Earthlings thought hard about how to find other planets. One method to detect planets is to look at how the stars next to those planets get pushed and pulled by the planets around them. In general, stars are big (big enough for gravity to win against pressure and squeeze matter toward fusion and photon production) and planets are comparably tiny (small enough not to allow gravity to win against pressure and not be able to start fusion). This means that to find planets using the radial velosity methods one needs to be able to measure velocities very accurately. Specifically, for an Earth-like planet around a Sun-like star, we need an instrument that can measure 0.1 m/sec velocities. This seems like a challenging problem. The speaker will discuss some of the ways they address this challenge.
April 5th, 2019, at 11 am
Reiner Janssen (NASA Postdoctoral Fellow at JPL)
"The Nature of Jet-mode Active Galaxtic Nucleii in Actively Star Forming Galaxies"
Abstract: According to the most successful galaxy-AGN co-evolution models, there should be two classes of AGN hosts: (1) Galaxies with active star formation and a 'classic', quasar-like AGN, both of which are fuelled by cold gas. (2) Gas-poor, 'red, and dead' galaxies, where the black hole accretes hot halo gas and as a result only produces radio jets (jet-mode AGN). Using all-sky optical and radio surveys, we investigate the properties of both quasar-like and jet-mode AGN in a wide range of host galaxy properties. In particular we find that (1) radio-loud quasar-like AGN behave differently from their radio-quiet counterparts and (2) there exists a significant population of jet-mode AGN in actively star forming galaxies. I will discuss the potential nature of latter these sources based on detailed investigations using multi-wavelength imaging and spectroscopy and show these sources might be ideal places to study both AGN triggering and AGN feedback.
If you look at some galaxies with a radio telescope you will can see amazing structures that can be as large as a few galaxies put together. Those big puffy structures trace particles that move extremely fast (close to the speed of light) and they spiral around magnetic fields. This causes them to lose energy an emission known as synchrotron radiation. What is so mighty to accelerate particles at speeds close to the speed of light? A growing super-massive (more than a million suns) black hole is so mighty! Reinier studies how these structures affect a galaxy's ability to make new stars. To do this he puts together optical, radio, and millimeter data to simultaneously look at active (i.e. eating/growing) super-massive black holes and the galaxies that host them. (Picture from EarthSky website: Active galaxy, Hercules A, showing extensive radio jets. Image via NRAO.)
March 7th, 2019, at 11 am
Hope Boyce (McGill University)
"Getting to know SITELLE"
Abstract: Found in a variety of shapes, sizes, and surroundings, HII regions in nearby galaxies offer the most detailed understanding of star formation across different environments. SITELLE, the 11x11 arc minute imaging Fourier transform spectrometer on CFHT, provides a unique opportunity to study extragalactic HII regions through the large program SIGNALS. On a completely different scale, Ultra Compact Dwarf Galaxies (UCDs) are a new class of stellar systems recently found in the centres of galaxy clusters and often thought to be hosts of intermediate mass black holes. During my 3 month internship here at CFHT I have been lucky enough to use SITELLE data to both identify HII regions in SIGNALS, and assess the feasibility of measuring UCD spectra with SITELLE. In this talk I will introduce myself, summarize my science interests and experiences, and report on progress in both of these projects.
March 6th, 2019, at 3 pm
Shiny Brar (McGill University)
"Probing the Radio-Transient Universe with CHIME"
Abstract: Fast radio bursts (FRBs) are sudden flashes of radio emission with millisecond durations and pulse-dispersion properties that place their sources at extragalactic distances. The mechanisms that produce FRB signals are unknown and the subject of active debate. The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a uniquely powerful monitor of FRB phenomena due to its high sensitivity and a large field-of-view that is efficiently searched using a sophisticated digital backend. In this talk, I will describe the CHIME telescope, its software backend built for real-time detection and early science results.
February 19th, 2019, at 11 am
Teruyuki Hirano (Tokyo Institute of Technology's Department of Earth and Planetary Sciences)
"Subaru/IRD: Technical Challenges and Early Results"
Abstract: InfraRed Doppler (IRD) instrument is a new high-resolution spectrograph on the Subaru
8.2 m telescope, developed for precise radial velocity (RV) measurements in the near IR.
Since the first light in 2017 August, we have tested the performance of IRD, and shown
that the RV precision of less than 3 m/s is achieved for bright M dwarfs on a timescale
of > 6 months. In this talk, I will summarize the current status of IRD, focusing on the
science goals and technical challenges in near-IR RV measurements. I will also present
the early engineering and scientific results by IRD.
January 17th, 2019, at 11 am
Alexandre Lazarian (University of Wisconsin)
"The Formation of Density Filaments in the Turbulent Interstellar Medium"
Abstract: Modern understanding of MHD turbulence suggests that this type of turbulence is strongly anisotropic at small scales. Due to turbulent fast reconnection turbulent eddies are aligned with the magnetic field surrounding the eddies. This entails a conclusion that gradients of velocity and magnetic field are perpendicular to the local direction of the magnetic field. Guided by this fact we proposed, developed and successfully tested with observational data a set of new techniques for studying interstellar magnetic fields. I shall demonstrate how the velocity gradients can be measured using either velocity centroids of thin channel spectroscopic maps, while magnetic field gradients can be measured using synchrotron intensity or synchrotron polarization. I shall present 3D maps of galactic magnetic fields obtained with the new technique, demonstrate that gradients can provide both magnetic field tracing and identify the regions of graviational collapse. I shall discuss new ways of obtaining magnetic field strength using the gradients. I shall show how to use different types of gradients to map the structure of the magnetic web within the multiphase interstellar media.
January 16th, 2019, at 11 am
Siyao Xu (University of Wisconsin)
"The Formation of Denisity Filaments in the Turbulent Interstellar Medium"
Abstract: Observations reveal that filamentary density structures widely spread in the interstellar medium, including both diffuse media and highly fragmented molecular clouds. The interstellar turbulence shapes the observed density structures. As the fundamental dynamics of compressible MHD turbulence, perpendicular turbulent mixing of density fluctuations entails elongated density structures aligned with the local magnetic field, accounting for low-density parallel filaments seen in diffuse atomic and molecular gas. I will show both theoretical understanding and numerical experiments to demonstrate that the elongation of low-density parallel filaments depends on the turbulence anisotropy. When taking into account the partial ionization, I will show that the minimum width of parallel filaments in the cold neutral medium and molecular clouds is determined by the neutral-ion decoupling scale perpendicular to magnetic field. In highly supersonic MHD turbulence in molecular clouds, both low-density parallel filaments due to anisotropic turbulent mixing and high-density filaments due to shock compression exist.
November 19, 2018, at
Tristan Guillot (Observatoire de la Cote d'Azur)
Abstract:I will provide a brief history of the new field of exoplanetology, from its birth in 1995 to the present. The initial discovery of 51 Peg b posed a mystery: how can giant planets be present extremely close to their parent star? The field has evolved since with a number of issues and new surprises. From the study of giant planets, their sizes, compositions, the field moved towards smaller planets. A number of close-in planets between the mass of Neptune and that of the Earth were discovered, often in highly compact configurations. Understanding how they were formed is among the most active area in this field. We are now entering the epoch of exoplanet characterisation, i.e., the spectra of some exoplanets can now be acquired, their atmospheric dynamics can be studied. In parallel, this led to a race to discover the most favorable targets. The study of exoplanets and their parent star(s) opens a new window to understand our Universe.
"A myriad of new worlds -
November 14, 2018, at
Shrinivas Kulkarni (California Institute of Technology)
Abstract:The Zwicky Transient Facility (ZTF) has been designed with a singular
focus: a systematic exploration of the night sky at a magnitude
level well suited for spectral classification and follow up with
the existing class of 4-m to 10-m class telescopes. ZTF is a
public-private partnership with a major MSIP grant from NSF and
contributions from a consortium of world-wide partners. The discovery
engine for ZTF is a 47 square degree camera (realized through 16
e2V monolithic CCDs) that fills the entire focal plane of the 48-inch
Oschin telescope of the Palomar Observatory. The large etendue
allows for a variety of surveys (slow, medium, fast) to be undertaken.
As a part of the intermediate Palomar Transient Factory (iPTF)
project a low resolution IFU spectrograph tuned for variability/transient
classification was commissioned on the Palomar 60-inch telescope
ZTF achieved first light a year ago and began a 30-month survey
earlier in summer. We are now finding a young SNe (<1 day) a few times
a week. ZTF appears to have the capacity to detect several thousand
SNe candidates. Our record so far 12 classifications in a single
night. ZTF is very well suited to finding really small bodies (down
to 5-m size) and short period binaries (the shortest period to date
is 6.9 minutes). ZTF is a prodigious factory for Tidal Disruption
Events and Super-Luminous Supernovae. Visiting the Galactic Plane
300 times a year ZTF will be prove to be a bonanza for stellar
astronomers. Since ZTF is PI-led effort there is considerable room
for innovation and rapid implementation. In short, ZTF is a TDA
pathfinder for LSST.
" Status of the Zwicky Transient Facility
October 19, 2018, at 11am
Gregory Tarle (University of Michigan)
Abstract: In 2019, The Dark Energy Spectroscopic Instrument (DESI) at the KPNO Mayall telescope will begin a 5-year survey of galaxies, quasars and stars to produce the most detailed 3-dimensional map of the Universe yet. DESI will study the nature of dark energy through the two techniques of Baryon Acoustic Oscillations (BAO) and Redshift Space Distortions (RSD). Central to the design of DESI is a new robotic fiber positioner system that will place 5000 optical fibers on targets of interest to an accuracy of several microns. The fibers sit behind a new prime-focus corrector with an 8 deg2 FOV. The fibers are brought down the Mayall structure to 10 spectrographs providing full coverage from 3600 to 9800A and resolutions up to 4500. I will focus this talk on the design, construction and testing of the individual DESI fiber positioners at the University of Michigan, which is now complete. I will also describe the work now underway at LBNL to integrate the positioners, external electronics, fibers and guide-focus assemblies into the DESI focal plane and the plans for installing the focal plane and fiber-optic cables on the Mayall in early 2019. The lessons learned from the DESI fiber positioner project are useful to inform other highly multiplexed fiber-fed spectrographs now being constructed and planned for the coming decade.
"Control Account Manager for the DESI Fiber Positioner System"
October 17, 2018, at
Jean-Francois Donati (Universite de Toulouse)
Abstract:Jean-Francois Donati will talk about SPiRou science and SPiRou performance.
"SPiRou Science and Performance"
October 11, 2018, at 11am
Olivier Lai, (Observatoire de la Cote d Azur),
Kanoa Withington, (CFHT),
Mark Chun, (IfA University of Hawaii)
Abstract: Imaka is a ground layer adaptive optics demonstrator on the UH 88 telescope, which saw first light in October 2016 and has been used since to explore GLAO performance in a variety of conditions. Being able to routinely measure the turbulence profile is a very useful tool to understand GLAO performance and optical turbulence in general. For instance, our experiments with imaka revealed the importance of dome seeing and self-generated turbulence. To understand this further, we have developed a new type of optical turbulence sensor called AIR FLOW: Airborne Interferometric Recombiner - Fluctuations of Light at Optical Wavelengths. It is based on a non-redundant mask imaging interferometer that samples the optical turbulence passing through a measurement cell. The instrument allows to measure the local two dimensional optical Phase Structure Function which fully characterises different types of turbulence (Kolmogorov, diffusive turbulence, etc.). By fitting different models, we can infer parameters such as Cn2, r0, L0 or deviation to fully developed turbulence. We have tested the instrument in the CFHT dome and it has proven reliable and sensitive enough to detect changes in the turbulent conditions close to the telescope beam with different dome vent configurations. In this talk, We will report on our findings and propose ways to further improve our understanding of dome seeing, to eventually be able to control it, through objective and quantitative use of the dome vents.
"Direct measure of dome seeing with a localised optical turbulence sensor."
September 28, 2018, at 11am
Jordan Raffard (Observatoire de Paris)
Abstract:SPIRou is the next-generation spectropolarimeter and high-precision velocimeter which offers the possibility to search for exoplanets around cool stars and explore the magnetic topology of protostars. It is equipped with a highly stabilized cryostat having the capability to get internal radial-velocity precision of about 0.3 m/s and a polarimeter to register the linear and circular polarization of stars. This summer several engineering tasks have been done to provide SPIRou to the astronomical community as well as the installation of the H4RG, the calibration of the atmospheric dispersion corrector, etc.
"Astronomical and Ground-based Systems Engineering for SPIRou first light and on-sky characterization"
August 27, 2018, at 11am
Eduardo Vitral (Ecole Polytechnique)
Abstract:Some galaxies host luminous, compact cores built around growing supermassive black holes. Those galactic centers are known as Active Galactic Nuclei and the processes associated with them may impact the evolution of the entire host galaxy.
Their study requires understanding complex physical processes associated with accretion physics, dust formation and destruction, star formation, and galaxy interactions.
One of the fundamental unresolved questions of galaxy evolution is the role AGN play in triggering or quenching star-formation. One method to study this question is to investigate the impact the AGN has on its host's interstellar medium, since interstellar medium is the fuel for star-formation.
In this project, I studied a sample of 12 nearby, optically luminous AGN, knowns as Quasars. I used optical, NIR, and some MIR spectroscopy to estimate if, how, and which types of AGN impact the interstellar medium of their host galaxies. Where possible I estimated BH masses, warm molecular gas masses, star formation rates, and looked for kinematic signatures of outflows.
In this presentation, I will first introduce the relevant AGN and galaxy evolution concepts and present my analysis in the context of current research in this field. Finally, I will present my conclusions and future steps.
"Infrared Spectroscopy of Nearby, Optically Luminous, Quasars"
August 20, 2018, at
Nicolas Martin (Universite de Strasbourg)
Abstract:I will present the latest results of the Pristine survey, a Franco-Canadian photometric survey of the Milky Way halo performed with the new CaHK filter on CFHT's MegaCam. Currently covering more than 3,000 deg^2, this survey leads to an efficient metallicity decomposition of the Milky Way halo. In particular, I will show how efficient Pristine is in selecting the metal-poor end of the metallicity distribution ([Fe/H]<-2.5) to hunt for the very rare extremely metal-poor stars (bearer of the chemical imprint of the first stars). I will present the Pristine discovery of one of the most metal-poor stars known to date. A dedicated part of the survey also focuses on the enigmatic very faint (and therefore metal-poor) Milky Way dwarf galaxies found over the last decade. I will show how efficient Pristine is at isolating likely member stars and how it opens a well-needed window onto the detailed study of these systems that are often used as near-field cosmological probes.
"An update on the Pristine survey - Mining and mapping the first generations of stars
August 16, 2018, at 11am
Barbara Mazzilli-Ciraulo (Universite de Strasbourg)
Abstract:Nearby Luminous Infrared Galaxies provide a window into the fate of galaxies at higher redshifts when gravitational interactions between gas rich galaxies may have created today's big ellipticals. II Zw 96 is Luminous Infrared system of merging galaxies, with global star-formation rates an order of magnitude larger than those of the well-studied merger system - the Antennae. Combined HST and Spitzer data suggested that 80% of the II Zw 096's IR emission comes from a small (~1 kpc) off-center region (region D). SITELLE provides high-resolution 3D spectroscopic data which we use to measure the kinematics and morphology of the ionized hydrogen, measure extinction corrected star-formation rates, and suggest a solution for the mystery of region D.
"Dancing Infrared-Bright Galaxies: Optical Imaging Fourier Transform Spectroscopy with SITELLE of the galaxy merger II Zw 96 "
July 30th, 2018, at 3:30 pm
Corinne Charbonnel (Department of Astronomy, University of Geneva, and CNRS)
Abstract:I will review the observations of multiple stellar populations in Galactic globular clusters, and will discuss the pros and cons of the scenarios that have been proposed to explain their origin.
"Multiple stellar populations in globular clusters "
July 30th, 2018, at 3:00 pm
Daniel Schaerer (Department of Astronomy, University of Geneva, and CNRS)
Abstract:I will present an update and overview on searches for sources of cosmic
reionization and their analogs at lower redshift from numerous recent
observational efforts with the HST and large ground-based telescopes.
Recent breakthroughs have allowed us to find fairly strong Lyman continuum
emitters (with escape fractions ~5-40%), and to significantly increase the
number of such confirmed sources. We discuss the physical properties of these
sources and the physical mechanisms allowing the escape of ionizing radiation.
The new results also allow us to define several new indirect diagnostics
(using e.g. Lyman-alpha, UV absorption lines, rest-optical emission lines),
which can be used up to the highest redshift and which will be crucial
to identify and study these sources with upcoming facilities and instruments,
such as the JWST and the ELTs.
"Searches for and properties of the sources of cosmic reionization "
July 24th, 2018, at 11:00 am
Pauline Barmby (Western University)
Abstract:X-ray binaries are probes of the physics of compact objects and stellar interactions. Multiwavelength identification of X-ray binaries tells us about star formation and stellar evolution in nearby galaxies and their star clusters. Outstanding questions include: are X-ray binaries made or born? From what kinds of parent systems? This talk will describe studies in three galaxies: M31, Sculptor dSph and the Milky Way, and their expected and unexpected results.
"Nearby galaxies and their X-ray binaries "
June 8, 2018, at
Kristy Webb (Universite of Waterloo)
Abstract: The Gemini Large Program, Gemini Observations of Galaxies in Rich Early Environments (GOGREEN) is an imaging and deep spectroscopic survey of 21 galaxy systems at 1 < z < 1.5. Some of the main science goals are to measure the role of environment in the evolution of low-mass galaxies, and measure the dynamics and stellar contents of their host haloes. The sample of galaxies were selected to span a factor of ~10 in halo mass, and have deep enough spectroscopy to be statistically complete for stellar masses of ~10^10.3 solar masses for all galaxy types over the redshift range. The spectroscopy is ~60 percent complete as of the semester 18A, with an anticipated final sample of ~500 new cluster memebers. In combination with existing spectroscopy on the brighter galaxies, GOGREEN will be a large legacy cluster and field galaxy sample with a wide range in stellar mass, halo mass, and cluster-centric radius. I will discuss the main goals of the survey, as well as the current status of several ongoing projects with the preliminary data. The focus of my project is to measure the star formation histories from the spectra of quiescent galaxies of different masses in different environments, and to distinguish between quenching mechanisms.
"Galaxies in Rich Early Environments"
June 4, 2018, at
Francois Bouchy (Obs Geneva, Switzerland and LAM, Marseille, France)
"From pixels to stellar radial velocites"
Abstract: Data reduction softwares of high-precision spectrographs has to face with several aspects to extract
from detector raw frames the radial velocity measurements of stars at the precision level of 1 m/s.
I will describe the main difficulties, challenges, pitfalls, tricks of such softwares, present some results
from the state-of-art spectrographs, and focus to the on-going development of the SPIRou pipeline.
May 29, 2018, at
Rene Doyon (Universite of Montreal)
"Detecting and Characterizing Nearby Habitable Worlds"
May 25, 2018, at
Etienne Artigau (Universite de Montreal)
"Glimpses into telluric subtraction and persistence effects with SPIRou"
May 24, 2018, at
"Battery Technology and Electric Vehicles"
May 09, 2018, at
Przemek Mroz (Astronomical Observatory of the University of Warsaw)
"Exploring the free-floating planet population with the OGLE data"
Abstract: Theories of planet formation predict the existence of a population of unbound (free-floating) planets. Gravitational microlensing provides a unique tool for studying these objects. The first results of Sumi et al. (2011) claimed that Jupiter-mass free-floating planets are as common as main-sequence stars. However, these results appear to disagree with censuses of substellar objects in young clusters and star-forming regions and with predictions of planet formation theories. I will present new results of the analysis of a ten times larger sample of microlensing events discovered by the OGLE-IV survey during the years 2010-2015. They shed new light on the population of free-floating planets.
May 01, 2018, at
Ismael Moumen (Laval University)
"A serendipitous discovery of a sample of Supernova Remnants in NGC 3344 with SITELLE"
Abstract: I present a 3D spectroscopic study of the nearby spiral galaxy NGC 3344. In particular, I will present the new sample of extragalactic Supernova Remnants (SNRs) recently discovered in the NGC 3344. Using the high spectral and spatial resolution data, obtained with the CFHT imaging spectrograph SITELLE, we identified a sample of SNR candidates by the well-known criteria [SII]/H_alpha > 0.4. Emission lines of [OII]3727, Hb, [OIII]4959,5007, Ha, [NII]6549,6584 and [SII]6717,6731 have been measured to study the ionized gas properties in the SNR candidates. Our analysis with SITELLE confirmed, with optical spectroscopy, the shock-excited nature of these sources. The question of the optimal background subtraction will be presented.
April 03, 2018, at
Kim-Vy Tran (University of New South Wales, Texas A & M University)
"From the FOURGE to the FIRE: Tracking Galaxy Evolution Over 12 Billion Years"
Abstract:ZFOURGE and ZFIRE are deep observational surveys that track how galaxies assemble over cosmic time. ZFOURGE identifies approximately 70,000 objects up to redshifts of z~7 using a custom set of near-infrared imaging filters that provide high precision photometric redshifts. ZFIRE selects galaxies from ZFOURGE for spectroscopic follow-up to measure how baryons cycle between stars, winds, and the Inter-Stellar Medium (ISM) at z~2. Here I highlight results that include building a library of composite Spectral Energy Distributions and properties of galaxies in clusters at z~2.
March 22, 2018, at
Carmelle Robert and Laurent Drissen (Universite de Laval)
"Some of the things we have done: Do ghost have hearts? and other stories"
It's almost time to head back home, so we would like to present an overview of some of the projects on which we have worked
during our 7 months sabbatical leave at UH-Hilo and CFHT, all of which involving SITELLE (with a little help from
our friend, ESPaDOnS): a well-hidden HII region inside a dusty star-forming region, and its accompanying young stars;
an expanding, old supernova remnant in the Milky way; a survey of the nearby galaxy M33; a rotation curve in a lopsided
spiral galaxy from absorption features; and star-forming galaxies 3 billion light-years away.
March 15, 2018, at
Eilat Glikman (Middlebury College)
"Dust-Reddened Quasars: Signposts for Feedback and co-evolution
Abstract: The study of the evolution of quasars and their influence on their host galaxies provides unique insight into how supermassive black holes became a ubiquitous feature of galaxies today. Dust-reddened quasars appear to represent a transitional phase in merger-driven models of quasar/galaxy co-evolution. I will present results from recent and ongoing surveys to identify these transitional systems using infrared and radio selection. The results of these surveys reveal that red quasars are among the most intrinsically-luminous quasars in the Universe, and make up ~20% of the overall quasar population. They reside in actively merging galaxies, and their rest-frame UV spectra exhibit outflows in absorption and emission. I will discuss how reddened quasars fit into the larger picture of AGN evolution which includes both mergers and secular growth. Finally, I will present new work on surveys to explore red-quasars’ parameter space to fully understand the connection between galaxy mergers and black hole growth.
February 21, 2018, at
Claire Moutou (CFHT)
"Radial velocities and exoplanets"
Abstract: This is a review or radial-velocity observing technics and developments in the last 30 years of explanet searches. I will also review the general characteristics of exoplants found using the radial-velocity method, and discuss recent discoveries.
February 12, 2018, at
Jean-Charles Cuillandre (Institut de Recherche sur les lois Fondamentales de l'Univers
Abstract: The ESA Euclid space mission core science goals rely on complementary deep ground-based surveys covering both the northern and southern galactic caps. This talk will present an overview of the space survey design and the current status of the ground-based survey campaign, with a focus on its forerunner, CFHT's Canada-France Imaging Survey.
"The challenge of the distributed Euclid survey"
January 24, 2018, at
Haeun Chung (Seoul National University/Korea Institute for Advanced Study)
Abstract: Devasthal Optical Telescope Integral Field Spectrograph (DOTIFS) is a new multi-Integral Field Unit (IFU) instrument being designed and fabricated by the Inter-University Center for Astronomy and Astrophysics (IUCAA), Pune, India, for the Cassegrain side port of the 3.6m Devasthal Optical Telescope, operated by the Aryabhatta Research Institute of Observational Sciences (ARIES). The science drivers mainly focus on nearby galaxies, which are the primary targets of the instrument. This includes star formation and kinematics of nearby galaxies, galactic HII regions, merging and interacting galaxies, etc. DOTIFS has sixteen IFUs, which can be deployed over an 8 arcminute diameter telescope focal plane. Each IFU sees 8.7 arcsec x 7.4 arcsec on the sky and is composed of a 12 x 12 array of hexagonal shape microlenses each of which is 0.8 arcsec vertex to vertex. Optical fibers are attached to the back side of each microlens to gather and transfer light to the spectrographs. Eight identical, all refractive, dedicated spectrographs cover 2,304 fibers, with 288 fibers (from two IFUs) per spectrograph. Its wavelength coverage is 370-740nm, and the spectral resolution is 1200 â 2400 over the wavelength range. In this talk, I will present an overview and current development status of the instrument.
"DOTIFS: a new multi-IFU optical spectrograph for the 3.6-m Devasthal optical telescope - overview and development status"
January 23, 2018, at
Lauren Weiss (Trottier Postdoctoral Fellow
Institute of Research on Exoplanets
Universite de Montreal)
Abstract: The universe has provided us with multiplanet systems, laboratories in which we can test the physics of planet formation. I will talk about three ways in which we can use multiplanet systems as laboratories. (1) We can study the orbital dynamics of a single multi-planet system in detail. (2) In each multiplanet system, we can compare a planet to its siblings, developing statistics over many systems. (3) We can compare multiplanet systems to systems with only one known planet. My talk will draw on results from the California Kepler Survey, which provided new stellar and planetary properties for 909 transiting planets in 355 multiplanet systems, as well as recent dynamical work.
"Multi-Planet Systems as Laboratories for Planet Formation"
December 8, 2017, at
Michael Radica (McMaster University)
Abstract: My talk will elaborate on the two main projects I have worked on during my time at the CFHT.
I will first discuss the problems encountered with the ORCS data reduction pipeline for SITELLE. Its
software was updated to version 2 in early September, which introduced issues in optimization of the
spectral line fitting procedure. I will speak about our attempts to isolate and fix the problem. The
second part of the talk will focus on my main project - to better understand the line of sight
variations in dust extinction, in the direction of NGC 6822. We have both high resolution spectroscopy,
as well as visible and infrared photometry, from SITELLE and WIRCam, for NGC 6822. In conjunction, our
photometry and spectroscopy can allow us to derive line of sight dust extinction laws for NGC 6822,
and identify how the individual line of sight laws vary from the mean diffuse dust extinction law,
commonly used to correct for dust in the Milky Way,
"A High Resolution Study of NGC 6822 with SITELLE"
November,17 2017, at
Erini Lambrides (John Hopkins University)
Abstract:Most galaxies appear to harbor a supermassive black hole (SMBH) at their centers. The growing
SMBH and their immediate neighborhoods appear as compact but highly luminous nuclei known Active
Galactic Nuclei (AGN). In this talk we present our efforts to disentangle the impact of AGN on the
interstellar medium of their host galaxies. We analyze 2200 mid-infrared spectra of active galaxies to
determine if and how accreting, super-massive black holes at the center of galaxies impact the
interstellar medium of their hosts. The molecular gas component of the interstellar medium is important
because it is the fuel for both star-formation and SMBH accretion. We provide a large census of
rotational molecular hydrogen emission in the context mid-infrared star-formation and AGN activity
diagnostics. We find a 200K difference between the excitation temperatures of the higher pure rotational
molecular hydrogen transitions in AGN dominated and non-AGN dominated spectra. We find a statistically
significant positive correlation between excess molecular hydrogen emission and the relative
contribution of the AGN to the IR emission. We also perform a census of polycyclic aromatic hydrocarbon
emission, and find that dust grains in AGN dominated galaxies appear have a wider size of ranges and
ionizations than non-AGN dominated galaxies. We interpret our findings as evidence of differences in the
star-forming molecular gas in AGN host galaxies, and interpret our molecular hydrogen temperature
differences as evidence of AGN host galaxies having a warmer or more dense warm molecular hydrogen
"Running up the Gas Bill: The Price of Leaving Your AGN On"
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 IÃ¢ÂÂll 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 11:00am
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 Fouquè.
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.