Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://www.naic.edu/~astro/School/Talks/condon_cont.pdf Äàòà èçìåíåíèÿ: Tue Jul 12 03:19:16 2005 Äàòà èíäåêñèðîâàíèÿ: Sat Dec 22 06:39:09 2007 Êîäèðîâêà: Ïîèñêîâûå ñëîâà: orion nebula

National Radio Astronomy Obse rvatory
July 11, 2005 NAIC/NRAO Sin gle-dish Summer School

Continuum Emission and Single Dishes
· Continuum sources produce steady, broadband noise · So do recei ver noise and drift, atmospheric emission, ground pickup, confusion, etc. · Single dishes can image large areas and low-brightness sources · Single dishes can use array feeds, wide bandwidths, and incoherent detectors
Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l

Continuu m Observing
Jim C ond on

Astronomical Continuum Sources
Synchrotron (dash-dot curve), free-free (dashes), and dust (dots) emission typical of spiral galaxies

408 MHz continuum emission, galactic coordinates

Ha sla m et al. 1982, A&AS, 47, 1 (see Chri s Salter)
Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l

Orion Nebula HII region at 8.4 GHz

Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l

Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l

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The Galactic dark cloud G11.11-0.12 in absorption at 8 microns (left) and in emission at 850 microns (right)

SCUBA on the JCMT

Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l

Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l

Dust emission at high redshifts 850 micron SCUBA/JCMT image of the HDFN

Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l

Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l

Strong continuum point sources as observing tools
· · · · Sanity checks Pointing, focus, and surface setting Intensity and polarization calibration Offset pointing corrections

A cross scan yields the pointing offset, beam width, and antenna temperature

Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l

Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l

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Distributions of normalized gain G resulting from Gaussian pointing errors with rms = HPBW


Pointing errors: ·Setting ·Gravitational ·Thermal ·Refraction

Diffe rential expansi on from solar heating bent the 300-foot telescope a way from the Sun (nea r = 13h 20 m).
Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l


This dense grid of pointing calibrators ca n be used to reduce tracking errors north of = -40°.


Axial Focus
GBT focal ellipsoid axial FWHM 4


Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l

Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l

Telescope setting by OOF holography

Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l

Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l





before:

Telescope surface-error maps: = 370 µ m after: = 210µ m

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Flux-density and polarization calibrators:
Baars, J. W. M., Ge nzel, R., Pauliny-T oth, I. I. K., & Witzel, A. 1977, A&A, 61, 99 Ott, M. et al. 1994, A&A, 284, 331 http://134.104.64.34/JN/effbg_rx/kalirie.ht m http://www.a oc.nrao.edu/~ gtaylor/calib.ht ml http://www.a oc.nrao.edu/~ gtaylor/cal ma n/polcal.html ftp://ftp.atnf.c siro.au/pub/atnfdoc s/guide s/at.cat

Single-dish continuum observations of faint and/or extended sources
· · · · · Thermal noise 1/f noise (recei ver and atmosphere) Confusion Baselines RFI

Single-dish position calibrators:
Cond on, J. J., & Yi n, Q. F. 2001, PASP, 113, 362 ftp://ftp.c v.nrao.edu/NRAO-sta ff/jcondon/PCAL S3.3 http://wiki.gb. nra o.edu/bi n/vie w/PTCS/Poi ntingFoc usCatalog
Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l

Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l

Postdetectio n power spectrum showing 1/f noise at low freque ncies and refrigerator microphonics near 1.2 Hz.

Radiometer equation for a real receiver

Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l

Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l

Confusion
Profile plot of 45 deg² near the NGP imaged with 12 arcmin resolution at 1.4 GHz. The strongest source shown has S 1.5 J y.


NVSS (45 arcsec FWHM) grayscale under GB (12 arcmin FWHM) contours illustrates source blending

Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l

Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l





Use < 1/(2


k)

: o n-the-fly mapping, Dicke switching, ...



k

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The confusion amplitude P(D) distribution [for n(s) = kS-2.1] "RMS" confusi on

D = i mage bri ght ne ss (e. g., Jy/bea m) D = 0 mean i s not a good ba seline; use runni ng median instead
Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l

The 5 extragalactic confusion limits for Arecibo (d = 220 m) and the GBT (d = 100 m).


Baselines
The total-power output from one receiver channel during a 4.85 GHz scan. The system temperature T 60 K includes receiver noise, atmospheric emission, spillover, leakage through the reflector mesh, etc.

Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l

Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l

Running-median ba seline s ha ve re moved atmospheric emi ssi on, spillover, 1/f noi se, and extended source s.

Beam-switching
The SNR 3C 10 imaged at 10.7 GHz by horizontal scans onl y (top) a nd by dual-bea m ba sket weaving (bottom). Basket weavi ng refere nce s: Sieber et al. 1979, A&A, 74, 361 Eme rson & Gra ve 1988, A&A, 190, 353 (see Chri s Salter)

Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l

Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l



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Future single-dish continuum projects
· Penn Array on GBT
can ma p 15 arcmin X 15 arcmi n with = 0.2 mJ y in 1 hour circumstellar disk s, S-Z clusters, protogalaxies, ...


64-element

= 3 mm bolometer ca mera, 8 arcsec re solution

· ALFA on Arecibo
7-element = 21 cm c ohe rent arra y, 3 arc min re solution full-Stoke s large-area continuum surve y Galactic loops, Faraday tomogra phy, transie nt source s
Natio na l Rad io Astro no my Observa tory July 11, 2005 ­ Single- dis h Summer Sc hoo l


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