Observatory Visit

Naomi McClure-GriffithsAustralia Telescope National Facility

CSIRO

Vacation Scholar Program2 Dec 2002

What is the Observatory Trip?

• Trip to Parkes of Narrabri from Friday the 17th of January to Tuesday the 21st, inclusive.

• Half students will go to Narrabri and half to Parkes observatories.

• 36 hours telescope time allocated at each observatory.

• Suggest that you form about 6 groups (3 people per group; 3 groups per observatory), with each group getting 12 hours of observing time each.

Basic Aims

• Give you “hands-on” experience in using a world-class telescope

• Give you some insight into various engineering issues as well as physical and astrophysical principles

• Give you an idea of what it’s like to propose and carryout a scientific experiment

• Have fun!

What will happen that weekend?

• Friday: Drive to Narrabri or Parkes.• Friday afternoon and Saturday morning:

Observatory tour, observer and safety training.• Saturday midday to Sunday midnight:

Observing (Three 12hr shifts) and data reduction.

• Monday: More data reduction and finishing up.• Tuesday morning: Drive back to Sydney.

What happens before then?

• December 12 - Introduction to Radio Astronomy lecture

• December 12 – 19 - Start setting up groups and thinking of reasonable projects– To keep in mind:

• Which telescope is good the type of project you want to do?

• Can you complete the project in 12 hours?• Can you reduce the data when you get it?

• December 19 - Project brainstorming session

What happens before then?• January 9 - Written project proposals due.

The proposal (~1 or 2 pages) should include:– Names of group members.– Aim of project and a justification for why this is

appropriate.– The observatory and equipment required. Note

any special hardware or software than might be required.

– Observing frequencies/velocities and source coordinates where relevant.

• January 9 – 17 - Prepare observing schedules• January 15 - Final briefing for the trip

Some Things You Might Need to Know

• Astronomical and telescope coordinates: Where is that source?

• What is sidereal time? And how to figure out when a source is in the sky

• How (very generally!) a single dish or interferometer works.

• How long it will take to get a result.• How (in a practical sense) to observe and

reduce data.

The Telescopes

• Parkes:– 64 meter diameter single antenna– Frequency from 440 MHz to 22 GHz– Low resolution, but large collecting area

• Australia Telescope Compact Array (ATCA):– Six 22 meter diameter antennas operate as an interferometer

– Antennas spread along a 6 km rail– Frequencies from 1.4 Gz to 110 GHz– High resolution, but less collecting area

Parkes Observatory

ATCA (Narrabri)

Interferometry• Interferometer is like a single

dish broken into two parts• Delays are inserted to

compensate for the different path lengths to each antenna.

• Interferometers give much higher resolution and are less susceptible to a number of systematic errors

• Interferometers fail to measure broad scale structure and are more complex devices.

Correlator

Earth rotation synthesis

15 min

4 hrs

12 hrs

What can we observe in the radio?

• Emission types– Continuum emission – Spectral lines

(frequency varying)– Time varying

• Emission mechanisms– Thermal – HII regions– Non-thermal – SNRs– Coherent – Pulsars

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

Frequency (several octaves)

-0.05

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

Frequency (Velocity)

Electromagnetic windows

Devising reasonable projects• Choose a question and then devise an experiment

that can answer that question • Choose something interesting

– Has it been done before?– Are you interested in a source or the instrument?

• Is your project do-able? – Can you detect the source(s)?– Have you chosen the right instrument?

• Do you want to detect it? Image it? Monitor it?– Will your source be up?

• Talk with each other, your supervisor, Naomi, anyone!

What sorts of astronomy?• Solar system

– Sun– Jupiter and other planets

• Nearby stars– Masers– Pulsars– Active stars (episodic)

• The Milky Way (our Galaxy)– HI– Galactic Centre– HII Regions– Supernova remnants– Molecular clouds

• Magellanic Clouds• Nearby galaxies• Distant galaxies

– Radio galaxies– AGN– Gravitational lensing

• Early universe– Cosmic microwave

background

Engineering experiments

• Atmosphere/radiometry– phase stability– 22 GHz water line

• Antennas– Focus effects– Spillover measurements– Distant sidelobes– Polarimetric response– Pointing – Holography/aperture

illumination

• Receivers– Receiver calibration– Hot/cold load tests

• Radio frequency interference– Mobile phones– Microwave ovens– Computers– Satellites

More on Science

• Match your project to the telescope:– Parkes sees a large area with a broad beam

• It is ideal for imaging large objects, measuring flux values, or looking at pulsars

– Narrabri sees a relatively small area with a narrow beam

• It is ideal for imaging regions with small detail, looking at small (extragalactic) objects

– If you want to look at a a large area, Parkes is it– If you want to look with high detail, Narrabri is it

Last Year’s Projects as Examples

• Narrabri:– Characterise site generated interference– Image the massive star Eta Carina at 12mm– High resolution imaging of HIPASS detected galaxies

• Parkes:– Detecting Ammonia in cold interstellar clouds– Detect and measure the velocity, acceleration of the

Galileo probe– Confirm pulsar detections from the Parkes pulsar

survey

Useful Observing Tools• ATNF observing documentation:

– http://www.narrabri.atnf.csiro.au/observering/users_guide/html/atug.html

• Parkes observing documentation:– http://www.parkes.atnf.csiro.au/documentation/documents.html

• Virtual Radio Interferometer (VRI)– http://www.narrabri.atnf.csiro.au/astronomy/vri.html

• ATCA Sensitivity Calculator– http://www.atnf.csiro.au/observers/docs/at_sens

• Parkes Sensitivity Calculator– http://www.parkes.atnf.csiro.au/cgi-bin/utilities/pks_sens.cgi

• Source Rise and Set Time Calculators– http://www.parkes.atnf.csiro.au/cgi-bin/utilities/coord.cgi (Parkes)

Reminders

• December 12 - Introduction to Radio Astronomy

• December 19 - Brainstorming Session• January 9 - Proposals Due• January 17-21 - The Trip!!• Contact:

– Naomi McClure-Griffiths:• Email: Naomi.McClure-Griffiths@csiro.au• Phone: x4321• Room: 91b Marsfield