Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://www.naic.edu/~astro/sdss7/talks/HoPtalks/CygnusloopGBT.pdf Äàòà èçìåíåíèÿ: Fri Aug 2 22:49:45 2013 Äàòà èíäåêñèðîâàíèÿ: Sat Mar 1 08:43:27 2014 Êîäèðîâêà: Ïîèñêîâûå ñëîâà: âíåøíèå ïëàíåòû

Continuum observations of the Cygnus loop using the GBT

Theresa Wiegert & Wu Yajun
with

Jim Condon Brian Mason

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What's cool about the Cygnus loop?
· LARGE supernova remnant at large galactic latitude and D=~0.54 kpc, exploded ~10000 years ago (Blair et al 2005) · Curious morphology - Two SNRs in one? (e.g. Uyaniker et al. 2002) · Non-thermal emission · What is its total flux at S-band? · What is its (overall) spectral index?

4.85 GHz, Condon et al 1989 (300 foot telescope, Greenbank)
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Observation setup
· Backend: Digital Continuum Receiver (DCR) at GBT · S-band - chose a bandwidth not contaminated by RFI => central frequency=2.09625 GHz, band width = 12.5 MHz

· Observations: 1:30 - 6:00 am, July 12
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Observation setup
· Backend: Digital Continuum Receiver (DCR) at GBT · S-band - chose a bandwidth not contaminated by RFI => central frequency=2.09625 GHz, band width = 12.5 MHz

· Observations: 1:30 - 6:00 am, July 12
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Observation setup
· Backend: Digital Continuum Receiver (DCR) at GBT · S-band - chose a bandwidth not contaminated by RFI => central frequency=2.09625 GHz, band width = 12.5 MHz

· Observations: 1:30 - 6:00 am, July 12
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Observations
· Flux calibrator 3C295 · Raster scans of an area 4°x 5° (both in Dec and RA for potential basket weaving) · Declination scans: 120 columns, 2' wide (estimated beam size 6') in three scheduling blocks (SBs) · Noise diode calibration beginning of each SB · Problem with too fast slewing: near zenith, passed speed limit for telescope => scans 60 s/column (iso 30s/column) · => less time for RA scans, only observed every 9 rows (1 SB) · Finished with 3C48 fluxcal scan · Beam efficiency 95% (GBT unblocked)

4


Observations
· Flux calibrator 3C295 · Raster scans of an area 4°x 5° (both in Dec and RA for potential basket weaving) · Declination scans: 120 columns, 2' wide (estimated beam size 6') in three scheduling blocks (SBs) · Noise diode calibration beginning of each SB · Problem with too fast slewing: near zenith, passed speed limit for telescope => scans 60 s/column (iso 30s/column) · => less time for RA scans, only observed every 9 rows (1 SB) · Finished with 3C48 fluxcal scan · Beam efficiency 95% (GBT unblocked)

4


Observations
· Flux calibrator 3C295 · Raster scans of an area 4°x 5° (both in Dec and RA for potential basket weaving) · Declination scans: 120 columns, 2' wide (estimated beam size 6') in three scheduling blocks (SBs) · Noise diode calibration beginning of each SB · Problem with too fast slewing: near zenith, passed speed limit for telescope => scans 60 s/column (iso 30s/column) · => less time for RA scans, only observed every 9 rows (1 SB) · Finished with 3C48 fluxcal scan · Beam efficiency 95% (GBT unblocked)

4


Observations
· Flux calibrator 3C295 · Raster scans of an area 4°x 5° (both in Dec and RA for potential basket weaving) · Declination scans: 120 columns, 2' wide (estimated beam size 6') in three scheduling blocks (SBs) · Noise diode calibration beginning of each SB · Problem with too fast slewing: near zenith, passed speed limit for telescope => scans 60 s/column (iso 30s/column) · => less time for RA scans, only observed every 9 rows (1 SB) · Finished with 3C48 fluxcal scan · Beam efficiency 95% (GBT unblocked)

4


Observations
· Flux calibrator 3C295 · Raster scans of an area 4°x 5° (both in Dec and RA for potential basket weaving) · Declination scans: 120 columns, 2' wide (estimated beam size 6') in three scheduling blocks (SBs) · Noise diode calibration beginning of each SB · Problem with too fast slewing: near zenith, passed speed limit for telescope => scans 60 s/column (iso 30s/column) · => less time for RA scans, only observed every 9 rows (1 SB) · Finished with 3C48 fluxcal scan · Beam efficiency 95% (GBT unblocked)

4


Observations
· Flux calibrator 3C295 · Raster scans of an area 4°x 5° (both in Dec and RA for potential basket weaving) · Declination scans: 120 columns, 2' wide (estimated beam size 6') in three scheduling blocks (SBs) · Noise diode calibration beginning of each SB · Problem with too fast slewing: near zenith, passed speed limit for telescope => scans 60 s/column (iso 30s/column) · => less time for RA scans, only observed every 9 rows (1 SB) · Finished with 3C48 fluxcal scan · Beam efficiency 95% (GBT unblocked)

4


Observations
· Flux calibrator 3C295 · Raster scans of an area 4°x 5° (both in Dec and RA for potential basket weaving) · Declination scans: 120 columns, 2' wide (estimated beam size 6') in three scheduling blocks (SBs) · Noise diode calibration beginning of each SB · Problem with too fast slewing: near zenith, passed speed limit for telescope => scans 60 s/column (iso 30s/column) · => less time for RA scans, only observed every 9 rows (1 SB) · Finished with 3C48 fluxcal scan · Beam efficiency 95% (GBT unblocked)

4


Observations
· Flux calibrator 3C295 · Raster scans of an area 4°x 5° (both in Dec and RA for potential basket weaving) · Declination scans: 120 columns, 2' wide (estimated beam size 6') in three scheduling blocks (SBs) · Noise diode calibration beginning of each SB · Problem with too fast slewing: near zenith, passed speed limit for telescope => scans 60 s/column (iso 30s/column) · => less time for RA scans, only observed every 9 rows (1 SB) · Finished with 3C48 fluxcal scan · Beam efficiency 95% (GBT unblocked)

4


Observations
· Flux calibrator 3C295 · Raster scans of an area 4°x 5° (both in Dec and RA for potential basket weaving) · Declination scans: 120 columns, 2' wide (estimated beam size 6') in three scheduling blocks (SBs) · Noise diode calibration beginning of each SB · Problem with too fast slewing: near zenith, passed speed limit for telescope => scans 60 s/column (iso 30s/column) · => less time for RA scans, only observed every 9 rows (1 SB) · Finished with 3C48 fluxcal scan · Beam efficiency 95% (GBT unblocked)

4


Observations
· Flux calibrator 3C295 · Raster scans of an area 4°x 5° (both in Dec and RA for potential basket weaving) · Declination scans: 120 columns, 2' wide (estimated beam size 6') in three scheduling blocks (SBs) · Noise diode calibration beginning of each SB · Problem with too fast slewing: near zenith, passed speed limit for telescope => scans 60 s/column (iso 30s/column) · => less time for RA scans, only observed every 9 rows (1 SB) · Finished with 3C48 fluxcal scan · Beam efficiency 95% (GBT unblocked)

4


Data reduction
· IDL image and merge the SBs · Baseline fitting to remove background · Flux calibrators: beam=6.4', conversion K-> Jy/beam=1.76 K/Jy (theor: ~2K/Jy) · Integrated flux density (CASA): 210Jy??? · Sanity check: Measure flux of CL2, compare to NVSS 1.4GHz flux (adjust for difference in frequency using published spectral index) => ~twice as much flux too!

Text

5


Data reduction
· IDL image and merge the SBs · Baseline fitting to remove background · Flux calibrators: beam=6.4', conversion K-> Jy/beam=1.76 K/Jy (theor: ~2K/Jy) · Integrated flux density (CASA): 210Jy??? · Sanity check: Measure flux of CL2, compare to NVSS 1.4GHz flux (adjust for difference in frequency using published spectral index) => ~twice as much flux too!

4.9%

Text

5


Data reduction
· IDL image and merge the SBs · Baseline fitting to remove background · Flux calibrators: beam=6.4', conversion K-> Jy/beam=1.76 K/Jy (theor: ~2K/Jy) · Integrated flux density (CASA): 210Jy??? · Sanity check: Measure flux of CL2, compare to NVSS 1.4GHz flux (adjust for difference in frequency using published spectral index) => ~twice as much flux too!

4.9% 7.7%

Text

5


Data reduction
· IDL image and merge the SBs · Baseline fitting to remove background · Flux calibrators: beam=6.4', conversion K-> Jy/beam=1.76 K/Jy (theor: ~2K/Jy) · Integrated flux density (CASA): 210Jy??? · Sanity check: Measure flux of CL2, compare to NVSS 1.4GHz flux (adjust for difference in frequency using published spectral index) => ~twice as much flux too!

4.9% 7.7%

Text

5


Data reduction
· IDL image and merge the SBs · Baseline fitting to remove background · Flux calibrators: beam=6.4', conversion K-> Jy/beam=1.76 K/Jy (theor: ~2K/Jy) · Integrated flux density (CASA): 210Jy??? · Sanity check: Measure flux of CL2, compare to NVSS 1.4GHz flux (adjust for difference in frequency using published spectral index) => ~twice as much flux too!

4.9% 7.7%

Text

5


Data reduction
· IDL image and merge the SBs · Baseline fitting to remove background · Flux calibrators: beam=6.4', conversion K-> Jy/beam=1.76 K/Jy (theor: ~2K/Jy) · Integrated flux density (CASA): 210Jy??? · Sanity check: Measure flux of CL2, compare to NVSS 1.4GHz flux (adjust for difference in frequency using published spectral index) => ~twice as much flux too!

4.9% 7.7%

CL2

Text

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Data reduction continued
· Searched for errors in procedures · Tool: Brian's brains (helpdesk/local expert)

6


Data reduction continued
· Searched for errors in procedures · Tool: Brian's brains (helpdesk/local expert)

6


Data reduction continued
· Searched for errors in procedures · Tool: Brian's brains (helpdesk/local expert)

6


Data reduction continued
· Searched for errors in procedures · Tool: Brian's brains (helpdesk/local expert)

· Bug in the way we used the noise diode calibrations: Every first scan of each SB is a cal scan (track scan to calibrate counts to K), followed by source scans. Cal scan consists of two parts: cal on and cal off. Source scans are one scan => counts differ by a factor of 2 between cal scan and source scans: cal scan source scans

...
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Results/lessons learnt
· Flux density: 105 Jy +/-6.3 (background
and fluxcal (obsed and listed) uncertainties)

· Spectral index =-0.52 slightly steeper but within limits of literature (-0.50+-0.06)

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Results/lessons learnt
· Flux density: 105 Jy +/-6.3 (background
and fluxcal (obsed and listed) uncertainties)

· Spectral index =-0.52 slightly steeper but within limits of literature (-0.50+-0.06)

... and some bonus experience:
· Always compare to literature · Do sanity checks using other sources in your data · Ask the experts on your instrument · Don't publish until you're SURE...
7


Results/lessons learnt
· Flux density: 105 Jy +/-6.3 (background
and fluxcal (obsed and listed) uncertainties)

· Spectral index =-0.52 slightly steeper but within limits of literature (-0.50+-0.06)

... and some bonus experience:
· Always compare to literature · Do sanity checks using other sources in your data · Ask the experts on your instrument · Don't publish until you're SURE...
7