iraf.net

I have four images of quasar host galaxies but I
cannot make out their morphologies. I wanted to
perform psf fitting and then subtract it from the
image so I can see the host galaxies. I checked
online and found there is a psf package in IRAF. I
used the following website as my reference
http://www.physics.hmc.edu/Astronomy/Ipsf.htmlIt said I need to run daofind first to obtain a .coo
file and then use the phot package to get a .mag file
I tried to obtain a .coo file but I kept getting an
error that the pixel file was not found.
Im not even sure if this procedure will work to give a
clearer image of the galaxies. I am relatively new to
IRAF so I would appreciate any help you can provide.
Thank you.__________________________________________________
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On Tue, 5 Apr 2005 08:40:59 -0700 (PDT)
Azmat Latif <nykid5@yahoo.com> wrote:> I have four images of quasar host galaxies but I
> cannot make out their morphologies. I wanted to
> perform psf fitting and then subtract it from the
> image so I can see the host galaxies. I checked
> online and found there is a psf package in IRAF. I
> used the following website as my reference
> http://www.physics.hmc.edu/Astronomy/Ipsf.html
>
> It said I need to run daofind first to obtain a .coo
> file and then use the phot package to get a .mag file
> I tried to obtain a .coo file but I kept getting an
> error that the pixel file was not found.
> Im not even sure if this procedure will work to give a
> clearer image of the galaxies. I am relatively new to
> IRAF so I would appreciate any help you can provide.
> Thank you.Hi Azmat,What type of images are you working with? The error you see is
typically because IRAF cannot find the location of the pixels. You may
want to try converting the images to FITS format before attempting to
use DAOPHOT (provided you haven't already).Some tests you can perform are to determine whether you can display the
image with ds9 or ximtool (e.g., 'display <image>'). You can next
check whether you can see the headers with 'imheader <image> l+'.
Running imheader will also show you whether the pixels were found (near
the top of the imheader output).DAOPHOT is mainly for crowded field photometry. As quasars are stellar-
like objects on an image frame, DAOPHOT may prove useful for you. You
would fit the stars in your image, then try to remove the quasar with
substar, using the derived PSF.I hope that helps. Let us know if you have further questions or
problems.Cheers,Phillip

On Tue, 5 Apr 2005 09:56:54 -0700 (PDT)
Azmat Latif <nykid5@yahoo.com> wrote:>
> Hello,
> Thank you for your quick response. Yes the
> images are already in FITS format. I can display them
> using ds9 and also can read the header information. I
> had used daofind a few days earlier and was able to
> obtaind a .coo file. It just keeps sayind Error:
> Cannot open pixel file (den1962g). I am not sure why
> it is not working now. I hope you can help me. Thank
> you once again.
> Hi Azmat,You may want to check that you have the permissions to write to the
imdir (found in the login.cl file). Often there are tasks that will
write temporary files (.imh/.pix -- IRAF image format, where .pix is
written to imdir), and if that directory is not writable by users, then
you will receive this error.Another issue could be the configuration of your login.cl file, or
that some parameter is set incorrectly. If the above check shows that
you have permissions to write to imdir, then you can move the login.cl
file and uparm directories somewhere else, then run mkiraf again. An
alternative is to run mkiraf in a subdirectory in $HOME, then run the
cl from that directory.If all that fails, could you send me the FITS image? If it is too
large for email, you can post it to the IRAF ftp site, in the /pub
directory (let me know if you do this, and include the name of the
file).site: iraf.noao.edu
user: anonymous
pass: <your email address>cd /pub
put <file>
I hope that helps.Cheers,Phillip

On Fri, 8 Apr 2005 07:48:55 -0700 (PDT)
Azmat Latif <nykid5@yahoo.com> wrote:> Hello,
> Thank you for help with daofind. I have
> everything now I believe. I wanted to ask about the
> psf task. The images I am working with are too big so
> I created new fits images by just copying the sections
> I needed. I have four images that have four quasars
> in them. I ran daofind and phot on the images to get
> the .coo and .mag files. I made my threshold really
> high so that only the quasars will be detected. I
> then entered the .coo and .mag files into the psf
> task. I have to remove the blurriness surrounding the
> quasars and am unsure of where to go from here. I
> also wanted to ask is it ok if I only have the quasars
> in the coordinate and mag files? I would appreciate
> any help you can provide. Thank you once again.
>
> Hi Azmat,The next step, at least for stellar photometry, is to remove the
quasars using the SUBSTAR task (see 'phelp substar' for more
information). SUBSTAR removes the stars in the photometry file (.mag).If I recall, your goal was to determine the morphology of the host
galaxy. Hence, I think that if you used only the quasars in the
derivation of the PSF, then you may have issues with the wings of the
PSF, i.e., they may include part of the host galaxy. You will probably
want to use other stars in the derivation of the psf, as this would
most likely give you a better estimate of the psf of the quasar.The SUBSTAR task will certainly give you an idea of how good the PSF
fit the actual quasar, and whether you will need to include other stars
in the PSF derivation.I hope that helps. Let us know if you have further questions.Cheers,Phillip

I have four images of quasar host galaxies but I
cannot make out their morphologies. I wanted to
perform psf fitting and then subtract it from the
image so I can see the host galaxies. I checked
online and found there is a psf package in IRAF. I
used the following website as my reference
http://www.physics.hmc.edu/Astronomy/Ipsf.htmlIt said I need to run daofind first to obtain a .coo
file and then use the phot package to get a .mag file
I tried to obtain a .coo file but I kept getting an
error that the pixel file was not found.
Im not even sure if this procedure will work to give a
clearer image of the galaxies. I am relatively new to
IRAF so I would appreciate any help you can provide.
Thank you.__________________________________________________
Do You Yahoo!?
Tired of spam? Yahoo! Mail has the best spam protection around
http://mail.yahoo.com

On Tue, 5 Apr 2005 08:40:59 -0700 (PDT)
Azmat Latif <nykid5@yahoo.com> wrote:> I have four images of quasar host galaxies but I
> cannot make out their morphologies. I wanted to
> perform psf fitting and then subtract it from the
> image so I can see the host galaxies. I checked
> online and found there is a psf package in IRAF. I
> used the following website as my reference
> http://www.physics.hmc.edu/Astronomy/Ipsf.html
>
> It said I need to run daofind first to obtain a .coo
> file and then use the phot package to get a .mag file
> I tried to obtain a .coo file but I kept getting an
> error that the pixel file was not found.
> Im not even sure if this procedure will work to give a
> clearer image of the galaxies. I am relatively new to
> IRAF so I would appreciate any help you can provide.
> Thank you.Hi Azmat,What type of images are you working with? The error you see is
typically because IRAF cannot find the location of the pixels. You may
want to try converting the images to FITS format before attempting to
use DAOPHOT (provided you haven't already).Some tests you can perform are to determine whether you can display the
image with ds9 or ximtool (e.g., 'display <image>'). You can next
check whether you can see the headers with 'imheader <image> l+'.
Running imheader will also show you whether the pixels were found (near
the top of the imheader output).DAOPHOT is mainly for crowded field photometry. As quasars are stellar-
like objects on an image frame, DAOPHOT may prove useful for you. You
would fit the stars in your image, then try to remove the quasar with
substar, using the derived PSF.I hope that helps. Let us know if you have further questions or
problems.Cheers,Phillip

On Tue, 5 Apr 2005 09:56:54 -0700 (PDT)
Azmat Latif <nykid5@yahoo.com> wrote:>
> Hello,
> Thank you for your quick response. Yes the
> images are already in FITS format. I can display them
> using ds9 and also can read the header information. I
> had used daofind a few days earlier and was able to
> obtaind a .coo file. It just keeps sayind Error:
> Cannot open pixel file (den1962g). I am not sure why
> it is not working now. I hope you can help me. Thank
> you once again.
> Hi Azmat,You may want to check that you have the permissions to write to the
imdir (found in the login.cl file). Often there are tasks that will
write temporary files (.imh/.pix -- IRAF image format, where .pix is
written to imdir), and if that directory is not writable by users, then
you will receive this error.Another issue could be the configuration of your login.cl file, or
that some parameter is set incorrectly. If the above check shows that
you have permissions to write to imdir, then you can move the login.cl
file and uparm directories somewhere else, then run mkiraf again. An
alternative is to run mkiraf in a subdirectory in $HOME, then run the
cl from that directory.If all that fails, could you send me the FITS image? If it is too
large for email, you can post it to the IRAF ftp site, in the /pub
directory (let me know if you do this, and include the name of the
file).site: iraf.noao.edu
user: anonymous
pass: <your email address>cd /pub
put <file>
I hope that helps.Cheers,Phillip

On Fri, 8 Apr 2005 07:48:55 -0700 (PDT)
Azmat Latif <nykid5@yahoo.com> wrote:> Hello,
> Thank you for help with daofind. I have
> everything now I believe. I wanted to ask about the
> psf task. The images I am working with are too big so
> I created new fits images by just copying the sections
> I needed. I have four images that have four quasars
> in them. I ran daofind and phot on the images to get
> the .coo and .mag files. I made my threshold really
> high so that only the quasars will be detected. I
> then entered the .coo and .mag files into the psf
> task. I have to remove the blurriness surrounding the
> quasars and am unsure of where to go from here. I
> also wanted to ask is it ok if I only have the quasars
> in the coordinate and mag files? I would appreciate
> any help you can provide. Thank you once again.
>
> Hi Azmat,The next step, at least for stellar photometry, is to remove the
quasars using the SUBSTAR task (see 'phelp substar' for more
information). SUBSTAR removes the stars in the photometry file (.mag).If I recall, your goal was to determine the morphology of the host
galaxy. Hence, I think that if you used only the quasars in the
derivation of the PSF, then you may have issues with the wings of the
PSF, i.e., they may include part of the host galaxy. You will probably
want to use other stars in the derivation of the psf, as this would
most likely give you a better estimate of the psf of the quasar.The SUBSTAR task will certainly give you an idea of how good the PSF
fit the actual quasar, and whether you will need to include other stars
in the PSF derivation.I hope that helps. Let us know if you have further questions.Cheers,Phillip