The Canadian Galactic Plane Survey

Mapping the Ecology Of the Milky Way Galaxy

A Universe of Stars? A Universe of Hydrogen gas

Understanding our Origins

The Evolution of Matter

The “ecosystem” of galaxies

The Milky Way Galaxy is the only galaxy close enough to see the details of the Galactic “Ecosystem”.

Challenges• The Galaxy is very big. Because we are inside it, it completely

encircles the earth. – A large area of sky must be observed.

• The Galaxy is a 3-dimensional object.– Must untangle the third dimension

• High Angular resolution is need to see the details in the context of the larger picture– A very large data base

• A large range of wavelengths must be covered to see all major components of the ISM– Several telescopes will be required.

Milky Way in Optical Light (0.0005 mm)

Stars obscured by dust

Milky Way in Far-infrared Light (0.0035 mm)

Old red stars with little obscuration

Milky Way at Sub-millimetre (=0.240 mm )

Dust now seen as an emitter

Milky Way at Radio (21 cm)

Atomic hydrogen gas (the basic stuff of the Universe)

The Milky Way at Radio (74 cm)

Ionized gas and magnetic fields

The Canadian Galactic Plane ConsortiumCanadian Universities

• University of Calgary• University of Alberta • University of British Columbia• University of Toronto• University of Montreal• University of Waterloo• Queen’s University• Université Laval

National Research Council of Canada

• Dominion Radio Astrophysical Observatory• Canadian Astronomical Data Centre

International Organizations

• California Institute of Technology • University of California, Berkeley • University of Massachusetts • University of New Mexico • Space Telescope Science Institute • Cambridge University • Hamburger Sternwarte

Objectives of the CGPS

Science Goals:

• How does the interstellar medium evolve?Explore the evolutionary relationship between the phases and states

of the interstellar medium. How due galaxies convert diffuse primordial hydrogen to stars and the building blocks of life?

• What energizes and shapes the medium?Characterize the energy sources and modes of energy transport

• Is the Milky Way a closed system?Explore the vertical structure out of the disk. Is there mass and

energy exchange between the disk and extragalactic space?

Observing Goals:

• Create a high-resolution, 3-dimensional map of the interstellar medium of the Milky Way

• Construct a Galactic Plane Survey Data base of the distribution of major constituents of the interstellar medium.

The CGPS Data Base

All images at 1 arcminute resolution

Where is the CGPS?

Image compliments of Alan Dyer

The Dominion Radio Astrophysical Observatory

Milky Way at Radio (21 cm)

Atomic hydrogen gas (the basic stuff of the Universe)

Atomic Hydrogen Image from a Single Antenna Radio Telescope

25-m Radio Telescope, DwingelooNetherlands Foundation for Radio Astronomy

Atomic Hydrogen Image from a Radio Interferometer

7-element Interferometer, PentictonDominion Radio Astrophysical Observatory

equivalent diameter equals 600m

Slicing up the Milky Way Galaxy

Sun

Galactic Centre

Velocity changes systematically with distance along the line of sight.

The Doppler Shift

Calgary CityPolice Officer

Speeding Vehicle

Atomic hydrogen data “cube”

A top-down view of the hydrogen cube

The Perseus spiral arm

The Local spiral arm

Outer spiral arm

A Walk Through the Galaxy

Optical Image Stars and Ionized gas (Thanks to Alan Dyer)

Radio 21cm image Neutral Hydrogen gas (Perseus Spiral Arm)

Optical Image Stars and Ionized gas

Far-Infrared Image Dust Particles

Optical Image Stars and Ionized gas

Radio 74 cm image Ionized Gas

Optical Image Stars and Ionized gas

Composite Image Hydrogen Gas Dust Ionized Gas

A 2000 Light-year section of the Perseus Arm.

Cold Hydrogen Clouds

Clouds of very cold, dense hydrogen are seen silhouetted against a bright hydrogen gas.

Where did these clouds come from?

Temperature < 50 K (-220 C)

Are they related to molecular clouds?

In some cases CO molecules are found. But in most cases there is no association.

A wider view of Cold HI and Molecular Clouds

Cold hydrogen in velocity space

Cold Hydrogen from a Spiral Shock Wave

Evidence of Large Scale Shocks

A “spur” of dust and gas emerging from the galactic plane.

All components of the interstellar medium merge in this spur.

What caused it?

A Chimney to the Galactic halo

The chimney is blown out by a cluster of massive hot stars at the bottom

Intense ultra-violet radiation “leaks” out of the galaxy

Atomic Hydrogen Mushroom Cloud

Only a very small fraction of the Galaxy has been surveyed so far.

• The missing link between diffuse hydrogen gas and molecular clouds

• Evidence of transfer (leakage) of radiation and matter to extragalactic space (chimney and mushroom cloud)

• Examples of large scale shocks that energize the matter between the stars.

• …

In this small fraction we have found:

What about the rest of the Galaxy?

A Global Survey: CGPS, VGPS and SGPS

A Global Galactic Plane Survey Dominion Radio Astrophysical ObservatoryNational Research Council of Canada

Australia Telescope Compact Array Commonwealth Science and Industrial Research Organisation

Very Large ArrayU.S. National Radio Astronomy Observatory