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Pilot Fast Mapping Survey

Next: Jodrell Virgo Survey Up: Minutes of the 1st Previous: Survey Simulations

Minutes of the talk on:
First Results from a Pilot Fast Mapping Survey

Kristine Spekkens (Cornell U.)

A more detailed version of this talk by the speaker is available in HTML, PDF or PPT format.

To test strategies for ALFA, we have considered different schemes to map fields in 4 ways:

1. Drift mode: 12s/beam
2. "Slow" OTF 6s/beam
3. "Fast" OTF, RA-Dec, 3s/beam (drive in RA, step in Dec)
4. "Fast" OTF, Dec-RA, 3s/beam (scan in DEC, step in RA)

Setup and preliminary analysis:

L-narrow, 1385-1425 MHz (x12.5 MH OPs, 12kHz ch)
1 sec integrations, across 5min strips
first order bandpass removal

The sensitivity across a strip mapped via different telescope motion schemes was tested:

drive vs. "slow" OTF
drive vs. "fast" OTF
Dec-RA vs RA-DEC seems same
close to what you expect
Baselines pretty flat

In first map, you see some variation, but when you average and hanning smooth, baselines appear flat.

Also look at power spectrum to look for harmonics in baselines: nothing apparent
Also look at power spectrum and average to look at average power.

Conclusions:

For all methods: theoretical sensitivity limit achieved
- no trend in rms across strip
- baselines flat
- no harmonics in baseline power spectrum.
Map sensitivity and baseline quality independent of mapping technique when you scan faster than the drift rate.
Let the science dictate.

Discussion/Questions: (Also for Riccardo's talk)

Paulo F.	PALFA would be happy to piggyback ZoA survey.
Wim vD.	This is obviously a lot of work. The big surveys will be good. Let's not have long discussions now, but only a few comments.
Jon D.	In Virgo, covering sky area doesn't gain you because the volume is constrained. Rather, you need to go lower than 10⁷ solar masses. To do that, you'll need to integrate longer to go to lower masses.
Riccardo	True. This exercise is of the strawman's kind.
Steve S.	There is some evidence that the HIMF is much flatter in the Virgo region than in the field, and may look more like the Zwaan et al. HIMF. Hence, there may be fewer galaxies at low mass.
Lister	Nyquist sampling is always a good idea, but the pulsar folks are not interested in Nyquist sampling.
Riccardo	But, at some point, we are going to have to figure out what we are all willing to compromise, given the pressure for telescope time. For weak detections, we may have to do repeat observations to follow up.
Desh	Actually, the pulsar folks would propose also Nyquist sampling since they want a second pass for reconfirmation.
Riccardo	Others might also be interested in the fast survey to look for transients, if it also repeats.
Lister	You need 3 passes, 1.5 arcmin in each direction for this array.
Desh	If you fill in the overlap region, you can get to Nyquist sampling with 2 passes.
Chris S.	Rather than staring for pulsar observations, you can also do very slow OTF mapping.

Next: Jodrell Virgo Survey Up: Minutes of the 1st Previous: Survey Simulations

This page created and maintained by Karen Masters, Kristine Spekkens and Martha Haynes.

Last modified: Wed Apr 30 13:34:33 EDT 2003

Minutes of the talk on: First Results from a Pilot Fast Mapping Survey

Kristine Spekkens (Cornell U.)

Conclusions:

Discussion/Questions: (Also for Riccardo's talk)

Minutes of the talk on:
First Results from a Pilot Fast Mapping Survey