[daip] problems measuring flux
Leonia Kogan
lkogan at aoc.nrao.edu
Mon Apr 23 12:13:45 EDT 2001
Kristy,
You wrote:
>Some times IMSTAT or IMEAN give a line:
>AIPS 1: Flux density = -3.2719E-02 Jy. Beam area = 100.63 pixels
As I understand the "some times" means you have different maps.
Some of them produce the line some not
If my guess is right then the answer is:
The line will be produced if the cathalog of the data include information
about the beam size and about the cell size
The line will not be produced if such an information absent at the
cathalog or it is equal zero.
Leonia
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>From kkdyer at unity.ncsu.edu Mon Apr 23 09:42 MDT 2001
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Date: Mon, 23 Apr 2001 10:51:07 -0400
From: "K. Dyer" <kkdyer at unity.ncsu.edu>
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To: Leonia Kogan <lkogan at zia.aoc.NRAO.EDU>
Subject: Re: [daip] problems measuring flux
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I could give you fits files that do and do not produce the flux line.
-- Kristy
Leonia Kogan wrote:
>
> Hi Kristy,
>
> May I start answering your second question:
>
> >2. If there is no beam size information in the head (that I can see),
> >how is IMEAN/IMSTAT calculating
>
> >1.5103E-02 Rms= 8.1310E-03 in JY/BEAM?
>
> Both IMEAN and IMSTAT should consider that all pixel values at the map
> are measured at JY/BEAM. And this information is given at the header:
>
> Minimum=-7.00000022E-03 Maximum= 1.34000003E-01 JY/BEAM
> ^^^^^^^
> Therefore IMEAN and IMSTAT do not carry out any conversion from
> JY/PIXEL to JY/BEAM or vice versa. They simple use the label.
>
> I think so
>
> Let me think about the first question
>
> Leonia
>
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> From owner-daip at kochab.cv.nrao.edu Sat Apr 21 15:51 MDT 2001
> Date: Sat, 21 Apr 2001 17:48:33 -0400
> From: "K. Dyer" <kkdyer at unity.ncsu.edu>
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> Organization: NCSU Astrophysics
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> Subject: [daip] problems measuring flux
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>
> I have the a map of single dish + interferometer data with header thus:
>
> AIPS 1: Image=SNR1006 (MA) Filename=PARKES .IMAP . 1
> AIPS 1: Telescope= Receiver=Molonglo
> AIPS 1: Observer=Roger-Mi User #= 1010
> AIPS 1: Observ. date=01-JUN-1983 Map date=12-OCT-2000
> AIPS 1: Minimum=-7.00000022E-03 Maximum= 1.34000003E-01 JY/BEAM
> AIPS 1: ----------------------------------------------------------------
> AIPS 1: Type Pixels Coord value at Pixel Coord incr Rotat
> AIPS 1: RA---NCP 256 15 02 46.281 129.00 -11.000 0.00
> AIPS 1: DEC--NCP 256 -41 55 45.265 129.00 11.000 0.27
> AIPS 1: FREQ 1 8.4300000E+08 1.00 1.0000000E+00 0.00
> AIPS 1: STOKES 1 1.0000000E+00 1.00 1.0000000E+00 0.00
> AIPS 1: ----------------------------------------------------------------
> AIPS 1: Coordinate equinox 2000.00
> AIPS 1: Maximum version number of extension files of type HI is 1
> AIPS 1: Maximum version number of extension files of type SL is 2
> AIPS 1: Maximum version number of extension files of type PL is 3
>
> I want to know the flux density [Jy] in a particular area but instead I
> get:
>
> IMSTAT
> AIPS 1: Mean= 1.8883E-02 rms= 6.9834E-03 JY/BEAM over 840. pixels
> AIPS 1: Maximum= 3.4000E-02 at 103 61 1 1 1 1 1
> AIPS 1: Skypos: RA 15 03 12.304 DEC -42 08 10.03
> AIPS 1: Skypos: IPOL 843.000 MHZ
> AIPS 1: Minimum= 3.0000E-03 at 78 56 1 1 1 1 1
> AIPS 1: Skypos: RA 15 03 37.061 DEC -42 09 02.38
> AIPS 1: Skypos: IPOL 843.000 MHZ
>
> IMEAN
> localh> IMEAN1: Task IMEAN (release of 15OCT99) begins
> localh> IMEAN1: ZTXOP2: using translated file name =
> localh> IMEAN1: ZTXOP2: /marcielocal/aips/FITS/parkes.ps
> localh> IMEAN1: Image= PARKES .CLIP . 8 2 xywind= 64 56
> 194 196
> localh> IMEAN1: Mean and rms found by fitting peak in histogram:
> localh> IMEAN1: Mean= 1.2134E-02 Rms= 5.2291E-03 **** from histogram
> localh> IMEAN1: Mean and rms found by including all data:
> localh> IMEAN1: Mean= 1.5103E-02 Rms= 8.1310E-03 JY/BEAM over 9226.
> pixels
> localh> IMEAN1: Minimum= 4.0000E-03 at 150 161 1 1
> localh> IMEAN1: Skypos: RA 15 02 25.467 DEC -41 49 53.74
> localh> IMEAN1: Maximum= 6.6000E-02 at 149 70 1 1
> localh> IMEAN1: Skypos: RA 15 02 26.782 DEC -42 06 33.91
> localh> IMEAN1: Skypos: IPOL 843.000 MHZ
> localh> IMEAN1: Appears to have ended successfully
> localh> IMEAN1: marcie 15OCT99 TST: Cpu= 0.0 Real= 0
>
> Some times IMSTAT or IMEAN will give a line:
>
> AIPS 1: Flux density = -3.2719E-02 Jy. Beam area = 100.63 pixels
>
> Sometimes it doesn't.
>
> Two questions:
>
> 1. Why doesn't it always give that line?
>
> 2. If there is no beam size information in the head (that I can see),
> how is IMEAN/IMSTAT calculating
>
> 1.5103E-02 Rms= 8.1310E-03 in JY/BEAM?
>
> -- Kristy Dyer
>
> --
> Work: Kristy_Dyer at ncsu.edu
> NCSU Astrophysics
> http://wonka.physics.ncsu.edu/~kkdyer/kristy.html
>
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--
Work: Kristy_Dyer at ncsu.edu
NCSU Astrophysics
http://wonka.physics.ncsu.edu/~kkdyer/kristy.html
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