Working with the C-CWEL data - Revision history

Rebull: /* Investigating the images of the objects */

2013-08-07T17:21:01Z

Investigating the images of the objects

Rebull: /* Doing Spitzer photometry */

2013-08-07T02:37:16Z

Doing Spitzer photometry

Rebull: /* Doing Spitzer photometry */

2013-08-06T23:43:35Z

Doing Spitzer photometry

Rebull: /* Data Tables, part 2 */

2013-08-06T23:42:25Z

Data Tables, part 2

Rebull: /* Data Tables, part 2 */

2013-08-06T23:42:06Z

Data Tables, part 2

Rebull at 23:41, 6 August 2013

2013-08-06T23:41:17Z

Rebull: /* Investigating the mosaics */

2013-08-02T21:55:43Z

Investigating the mosaics

Rebull: /* Doing Spitzer photometry */

2013-08-02T18:59:27Z

Doing Spitzer photometry

Rebull: /* Doing Spitzer photometry */

2013-08-02T18:58:56Z

Doing Spitzer photometry

Rebull at 18:55, 2 August 2013

2013-08-02T18:55:36Z

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 *[[How can I get data from other wavelengths to compare with infrared data from Spitzer?]]
 *[[Resolution]] (specifically some of the concrete examples there)
-*[http://irsa.ipac.caltech.edu/applications/finderchart/ IRSA finder chart]
+*[http://irsa.ipac.caltech.edu/applications/finderchart/ IRSA finder chart] itself (direct link)
 *[http://www.youtube.com/watch?v=4RHS497XeHQ YouTube video on using Finder Chart]. To use the small images from FinderChart to also examine larger images, download the FinderChart thumbnail images as FITS files, load them and the larger image(s) into ds9, pick one of the small finder chart images, and then pick 'Frame/Match/Frame/WCS'. All will snap to alignment with North up, on the same scale, with the target object in the center.

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 *[[Photometry]]
 *[[I'm ready to go on to a more advanced discussion of photometry]]
-*[[Aperture photometry using APT]], specifically [[Aperture_photometry_using_APT#Looking_for_a_cookbook.3F|this]], which is the closest thing to a cookbook I will give you.
+*[[Aperture photometry using APT]], specifically [[Aperture_photometry_using_APT#Looking_for_a_cookbook.3F|this]], which is the closest thing to a cookbook I will give you. <font color="orange">THIS IS THE PAGE THAT HAS THE STEPS AND THE APERTURE/ANNULUS COMBINATIONS AND APERTURE CORRECTIONS IN IT</font>
 *[http://www.youtube.com/watch?v=_w_5DgB0vKw YouTube video on using APT], including calculating the number APT needs.  (15 min because it starts from software installation and goes through doing photometry.)
 *[http://www.youtube.com/watch?v=vmn4zX0bRrU YouTube video on photometry in general] (from NITARP tutorials)

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 =Doing Spitzer photometry=
-<font color="red">DONE for the test set.</font>
+<font color="red">DONE for the test set.</font> (Ultimately need to do for all sources of interest with Spitzer data - look at batch processing ("source list") photometry in APT.)
 OK, this step is going to take the longest, be the most complex, and involve the most steps out of everything (so far, anyway!).

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 =Data Tables, part 2=
-<font color="red">PARTIALLY DONE</font> - need to use regions file on WISE mosaics, answer last question
+<font color="red">PARTIALLY DONE</font> - need to use regions file on WISE mosaics, answer Q3 below
 OK, now we need to do some more advanced things with data tables, not necessarily limited just to those in Excel.

← Older revision		Revision as of 23:42, 6 August 2013
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	=Data Tables, part 2=		=Data Tables, part 2=
		+
		+	<font color="red">PARTIALLY DONE</font> - need to use regions file on WISE mosaics, answer last question

	OK, now we need to do some more advanced things with data tables, not necessarily limited just to those in Excel.		OK, now we need to do some more advanced things with data tables, not necessarily limited just to those in Excel.

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 =Obtaining the data=
 We have just one region we care about, so just one place to search on the sky. We need to get the relevant data from both WISE and Spitzer.
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 =Investigating the mosaics =
 '''It is "real astronomy" to spend a lot of time staring at the mosaics and understanding what you are looking at. Don't dismiss this step as not "real astronomy" just because you are not making quantitative measurements.  This is time well-spent, and you should plan on investing some time doing this section.'''  Some aspects of this were already discussed in the context of the Resolution worksheet.
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 =Data Tables, part 1=
 Hopefully, you already have developed some of these skills via [[C-CWEL Excel Practice]]. If not, this is the time to learn!
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 =Making color-color and color-magnitude plots=
 OK, fair warning, some math involved, and the start of ''programming'' spreadsheets!
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 =Doing Spitzer photometry=
 OK, this step is going to take the longest, be the most complex, and involve the most steps out of everything (so far, anyway!).

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 #How does the number of '''stars''' differ across the bands? Which band has the most stars? The fewest? (Bonus question: why?) The most '''nebulosity'''? The least? (Bonus question: why?) Are there more stars in the regions of nebulosity, or less? Why?
 #What is saturated? Are the same objects saturated in all bands? What are some other instrumental effects you can see? [[Example Spitzer/MIPS image with substantial artifacts here]] if you want to train your eye, or see an extreme case. (Bonus: which way was the scan map 'painting' the sky?)
-#Notice the pixel scale. What is the real pixel scale of the original instrument (WISE, IRAC, MIPS)? What are the pixel scales of the images? Does that actually change the resolution? (for advanced folks - why did we do this?)
+#Notice the pixel scale. What is the real pixel scale of the original instrument (WISE, IRAC, MIPS)? What are the pixel scales of the images? Does that actually change the resolution? (for advanced folks - why did we do this?)  (You may have already addressed these issues during the [[Resolution]] work earlier this year.)
 #Make a three-color image.  What happens when you include a MIPS-24 or WISE-22 mosaic in as one of the three colors with shorter bands as the other two colors? (NB: this might be easiest within the same telescope, e.g., use just WISE bands or just Spitzer bands to make a 3-color image.) Do the stars match up? Does the resolution matter? Can you tell from just a glance at the three-color mosaic which stars are bright at 22 or 24 microns?
 #How much more detail do you see with Spitzer that was missed by WISE? How do the resolution and sensitivity vary?

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 '''Never just trust that the computer has done it right. It probably did what you asked it to do correctly, but maybe you asked it to do the wrong thing. '''Always''' make some plots to test and see if the photometry seems correct.'''
-'''Big picture goal''': Understand what photometry is, and what the steps are to accomplish it.  Do Spitzer photometry on a source-by-source basis for the 'interesting' sources. Understand the units of Spitzer images.  Understand how to assess if your photometry makes sense.
+'''Big picture goal''': Understand what photometry is, and what the steps are to accomplish it.  Ultimately, do Spitzer photometry on a source-by-source basis for the 'interesting' sources. Understand the units of Spitzer images.  Understand how to assess if your photometry makes sense.
-'''More specific shorter term goals''': Ultimately, do photometry on all channels of the Spitzer mosaics for the sources that have survived so far as YSO candidates (or YSOs from the literature); for now, just do a short list of test guys.  Assess whether your photometry seems right.
+'''More specific shorter term goals''': For now, just do Spitzer photometry in all bands for a short list of test guys.  Assess whether your photometry seems right.
 '''Relevant links''':

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 #You should have a WISE catalog, either from your earlier download or the DVD. Load that puppy into Excel. Cope with the long header - scan it, keep it elsewhere, but you may not want to read it in to your Excel copy. What information do we need? How do you figure out which ones have bad photometry?
 #You should have a copy of Xavier's catalog with classifications on the DVD. Load that into another Excel worksheet or file. This one has a lot less documentation within the catalog; its documentation is a separate file, and you will need to consult this to decrypt which sources are YSO candidates and which are not. Figure out how to do this. There may be some utility in keeping the codes (rather than global search and replace).
-#Are these two files in the same order? (Did you change the order during the prior 'decryption' step? I did!) How could you find out, and fix this if necessary? Do they contain the same number of sources? Can you just copy the classification column out of Xavier's catalog into the WISE catalog? You need to tie Xavier's class to the WISE object, because in the next step, you will need a way of identifying the YSO candidates in plots.
+#Are these two files in the same order? (Did you change the order during the prior 'decryption' step? I did!) How could you find out, and fix this if necessary? Do they contain the same number of sources? Can you just copy the classification column out of Xavier's catalog into the WISE catalog? You need to tie Xavier's class to the WISE object, because in the next step, you will need a way of identifying the YSO candidates in plots.  Save this file as its own Excel file.
 =Making color-color and color-magnitude plots=
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 '''Big picture goal''': Understand what plots to make. Understand the basic idea of using them to pick out certain objects.
-'''More specific shorter term goals''': Make some color-color and color-mag plots using the data imported into Excel in the last step. At the very least, make a plot of the entire distribution and highlight the YSO candidates from Xavier.
+'''More specific shorter term goals''': Make some color-color and color-mag plots using the complete WISE catalog imported into Excel in the last step. At the very least, make a plot of the entire distribution and highlight the YSO candidates from Xavier.
 '''Relevant links''':
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 #Start from the complete WISE catalog. Pick at least one color-color or color-magnitude plot to make (Suggestion: W1-W2 vs W3-W4, K vs. W1-W4 plot, or a W1 vs. W1-W4 plot).  Figure out a way to ignore the "no data" flags (exactly what they are depends on which file you are starting from - they could be 'null' or they could be '-9'). Does the photometry seem ok? Identify the regions where you expect to find the plain stars and the IR excess objects.
 #Which objects are selected by Xavier's method as YSO candidates? Overplot them '''on the same plot''' as above with a different color and/or shape symbol. You may wish to try drawing the line segments on the plot too.
-#Bonus - read in one of my catalogs from the DVD that has literature sources indicated. Overplot these on the same plot, with a different color and/or shape symbol. Are the literature sources tagged as YSO candidates by Xavier or not?
+#Bonus - read in one of my catalogs from the DVD that has literature sources indicated (e.g, the 'interesting' file loaded into Excel in the last step). Overplot these on the same plot, with a different color and/or shape symbol. Are the literature sources tagged as YSO candidates by Xavier or not?
 #EXTRA BONUS, especially when circling back to this step - are there any sources you can identify in this diagram that might be worth a second look in SED or images?
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 '''Tasks and Questions for you''':
-#We already have good coordinates from each paper for BRC 38. I matched them all; copies of these files are on the DVD and they should import cleanly into xls, but be careful about the limits (see below).
+#For each of the ''*known*'' objects, you have the RA/Dec - find some of the objects in the images you obtained above. (Hint: you want a ds9 regions file: [[file:brc38knownysos.reg.txt]] is the file for just the known ysos. The file off the DVD that has "withnames" in the filename also prints the row number on top of the region.)  Take notes on any that look like the photometry may be corrupted or that you can easily dismiss as galaxies or other contaminants now that you are looking at better and/or different data than they had before. <font color="green">TEST SAMPLE: the first 4 previously known objects in the 'interesting' list (row numbers 1127, 1144, 1352, 1682)</font> (hint to find them in the image: they are sorted by, and therefore numbered by, RA). Which objects have a WISE match? Which might we worry about?
-##CAUTION 1: Some of the literature reported whole data tables, and some just reported the YSOs. So there are files from me with everything in the literature (long) and files with just the things someone in the literature tagged as YSOs (short). There are also files from me with just the 'interesting' ones (meaning the literature-identified plus the new Xavier-identified). Because the file of all the 'interesting' sources has a column indicating whether the source is there because it is previously known ("PrevKn") or is in the list because it seems to have a WISE IR excess ("WISEIRx"), you can tell from that column in the 'interesting' files which sources are solely literature ("PrevKn") and which are literature but also seem independently to have an IR excess ("PrevKn+WISEIRx"). The sources you want to work with (for now) are the ones that someone in the literature tagged as YSOs. So, you can use EITHER the 'interesting' file OR the 'justlitysos' files. '''TO SAVE YOU WORK DOWNSTREAM, SUGGEST YOU LOAD 'INTERESTING' FILE.'''
+#BONUS ONLY IF YOU ARE INTERESTED IN BANDMERGING ... For each of the known YSOs (identified in the 'interesting' file), you have the RA/Dec - find the same objects in the big WISE catalog. Which objects are the matches? What constitutes a 'match'? Are there any with no matches?  Spot check a few of my matches between strictly literature catalogs. Did I match them correctly? Which ones are the same between papers and which are new to just one paper?
-##CAUTION 2, AND THIS ONE'S A BIGGIE: '''These catalog files generally have a mixture of detections and limits, measurements and errors, flux densities and magnitudes.''' You will need to be careful in importing this into Excel. The UBVRIriHalphaJHK are all Vega mags, some have errors and some have limits. The IRAC and MIPS data are all in FLUX DENSITIES (uJy), and often have limits.
+#Now, start to pull together stuff from this step plus those above.  You can plot RA/Dec of everything. Here, I've done this both in an x/y plot and overplotted on the image (click to get a big one). The first one has several types of objects (defined in plot itself) plotted just in a graph; the second one just has the "sources of interest" (==previously identified YSOs+new candidate YSOs), overplotted on the WISE-1 image (the green circle is the 20 arcmin radius circle that defines our region of interest.
 <gallery widths="100px" heights="100px">
 file:Brc38where1jul2013.png
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 </gallery>
 Why are there some regions where WISE sources are missing? Are they really missing, or just missing from the catalog? Why are the Spitzer sources where they are? Why is there a patch of black in the center of the plot on the left (hint: Beltran et al.)?
 Things to note:
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 To start, we should decide as a group which small set of sources to measure, and have everyone measure the same sources. We will then compare all of our measurements among the whole group. Ultimately, we will need to measure photometry for everything we care about that falls in the Spitzer maps. <font color="green">'''NEARLY ARBITRARILY''', I've picked 5384, 3704, 4009, 3896 as some good test particles.</font>
-The measurements you get from the Spitzer images are in flux density, e.g., they will come in Jy (microJy or milliJy). It is easier to compare measurements if you convert these to magnitudes first. Ultimately, you need magnitudes for use in color-color and color-mag diagrams. You will also need to convert these into the right units for addition to the SEDs. For now, just convert them to magnitudes. See [[Units#Units_of_Spitzer_Photometry]] and [[Central wavelengths and zero points]] for the numbers and formulae you need.
+The measurements you get from the Spitzer images are in flux density, e.g., they will come in Jy (microJy or milliJy). It is easier to compare measurements if you convert these to magnitudes first. Ultimately, you need magnitudes for use in color-color and color-mag diagrams anyway. You will also need to convert these into the right units for addition to the SEDs. For now, just convert them to magnitudes. See [[Units#Units_of_Spitzer_Photometry]] and [[Central wavelengths and zero points]] for the numbers and formulae you need.
 '''Steps''':