Task answer notes from luisa

Task 0

I really hoped that I had successfully reached everyone with some content in June, or at least that people would have time to go back and go through it all again. In June, my last words to you all were to go home, find a quiet few hours, and go through the wiki again with your notes. I knew we'd gone through a lot, very fast, but I also knew that you all had been doing things right (=correctly, confidently, independently) while you were here, and that it was going to take some review with the materials on the wiki to get it all straight. But it seems that I didn't successfully reach everyone, and apparently no one had time to go through it again. I will try to make sure next year's teams come later than June so that the visit is closer to getting tasks done and farther from vacations...

If you are really feeling terribly underwater here, really, please, sit down with the Working with CG4+SA101 page. I promise, there are TONS more words and instructions and step-through-it exercises there. When I say I am proceeding as if you are familiar with the stuff from before, I really do mean it... If absolutely the only thing you get out of this is successfully actually learning just one or two of the tasks from the summer and never getting into this, then that's fine, it's still more than you knew a year ago.

Task 1

TASK: spot-check some of my photometry

Still needs some spot checks. Have only heard from Russ that maybe one is wrong. Have not put in the time to resolve this one.

NB: SPOT CHECKS does not mean DO EVERY SINGLE ONE. It means do enough to assure yourself that (a) you know how to do it, and (b) that I did it right in at least a few cases. HOWEVER, having said that, in another few steps, you'll need to investigate each one separately in as many images as possible, so it is probably worth LOCATING the objects in a few different Spitzer frames, even if you don't do the PHOTOMETRY. Are they all point sources?

Updates from Luisa, Fri Dec 17 15:28:53 PST 2010. The way that I would go about this task is inexorably intertwined with investigating the images at each band, which was technically task 4. I am pretty sure that my photometry is ok for most of the sources. For the source that got corrected midstream (the one previously-known YSO with the corrected coords) for some reason does not have a measured MIPS flux in my photometry. This is weird, and something that I ultimately want to track down.

Task 2

TASK: look at the short lists of YSO candidates.

FAQ: wondering which files to use? *ysocand.tbl.

which are duplicates? there are several that are rediscovered between the tiles. i'll leave it to you to identify the specific ones. from the entire catalogs, there are more than 1000 objects in common between the frames.

are there any that should have been rediscovered but were not? no, that is -- if it was in both tiles, then it was identified as a YSO in both independent detections.

Task 3

TASK: did we rediscover any of the [previously-identified YSOs]?

yes, yes we did. i get 5, or possibly 6; see next item.

are there any in the maps that we did not rediscover? yes, possibly 1.

why did we not rediscover them? (e.g., do they not have any IR excess? if not, why were they identified as young before? can you think of a reason for this discrepancy, if it exists?) I HAVE NOT COMPLETED THIS TASK but i can tell you that some strongly contributing reasons we did not recover one of them is because (a) it requires a larger than "usual" coordinate shift to match it to one of the catalog items (is that a true match? are there other sources in that region it could match to?); (b) for the closest match, we only have 2 irac bands in the catalog, which means that the gutermuth method could never have recovered it. (why do we have only 2 bands? is it on the edge? it it saturated? i don't know; i am leaving this to you.)

UPDATE 23 NOV copy from email.

Mark is working on making SEDs, and had a question re: the source matching with the previously identified objects:

mark says: I was able to match up 5 previous identified Reipurth & Pettersson sources, but there's a final sixth that I'm having trouble matching (see below). Any ideas?

• CG-Halpha 4? 073121.8-465943 112.84104 -46.995456
• CG-Halpha 4? 073121.8-465744 112.84107 -46.96228
• CG-Halpha 4? 073121.9-465746 112.841607 -46.962904

hm. certainly when I did this before, there was one source where I wasn't sure if I found the right match or not; it required a relatively large shift to find the match. ok, here is what i get for the matching.

• cg-halpha 1 -- 667" from anything. no match.
• 2 -- 1.45" from 073057.5-465611
• 3 -- 1.23" from 073110.8-470032
• 4 -- 1.66" from 073121.8-465943
• 5 -- 0.89" from 073136.6-470013
• 6 -- 0.82" from 073137.4-470021
• 7 -- 1.10" from 073326.8-464842
• 8 -- >10,000 arcsec from anything, no match
• PHalpha 92 -- >58,000 arcsec from anything, no match

Now, remember, this is a blind matching, which the computer is doing without my intervention. 1.66" is pretty far, compared to the other coordinates in the list (it's the largest one of all the matches). BUT, the next closest thing is 6.2" away, much further than the rest.

So, let's go look at the images. I asked IRSA's finder chart service (http://irsa.ipac.caltech.edu/applications/FinderChart/ -- linked from the fall work page also) to give me DSS and 2MASS images at this location: 112.84133 -46.995872 and in the DSS images as well as the 2MASS images, there's nothing really very bright at this location, which already makes me suspicious -- the prior optical surveys were very shallow, so they should have only found the bright sources. The fact that there is no bright source here is worriesome.

Here is a screenshot of what I get when I look at the IRAC1234+MIPS1 image of this region, and the last pane is 2MASS J (I think) for comparison. The green circle in the first panel is centered on the position for CG4-Halpha 4; the other panes are aligned to cover the same area, in the same orientation. The objects at the location given for CG4-Halpha 4 are faint even in 3.6 um! And really nothing is there at all in irac-3 or 4. It MIGHT be there in mips1, but wow that's a stretch. And it's definitely not there in 2MASS.

SO, my conclusion is that we don't know exactly what object Reipurth and Petersson were really looking at when they recorded CG4-Halpha 4. It could have been that one of these faint guys really was whoppingly bright at the time that they observed it -- after all, young stars do vary with time. BUT whatever it was is either not really at this location (e.g., they screwed up the coordinates), or perhaps there was an error in transcription.

I went back to the Reipurth and Pettersson paper, and it reports in 1950 coordinates: 7:29:54.1, -46:51:19 when i convert this to J2000, I get 7:31:21.95, -46:57:45.1 note that this is -46:57:45, not -46:59:45. That's an easy error to make, especially if transcribing something handwritten!

With that new position, the closest match is 0.71" away from 073121.8-465745. At this location in the images, there's something whoppingly bright at the Spitzer bands, and it's seen at MIPS-24 too, though for some reason this object is missing a flux at 24 um in our catalog. The object apears to be saturated or somehow other compromised at 8um, so there's no flux there either. I can see it in the 2MASS images, though it is missing a 2MASS flux in our catalog as well -- perhaps it is saturated.

OK, so the implications of this are: (1) we need to update (correct) the list of previously known sources in at least 2 places on the wiki, and in all of your own notes and spreadsheets. (2) someone needs to go manually measure the flux densities for him at least at 24um. (2a -- i need to track down why there is no mips-24 flux (and for that matter, JHK and 8um) for this object in my catalog) (3) the current best ysocandidate list DOES NOT ALREADY HAVE this guy included -- it's in the master catalog, but it didn't have a 24 um flux there either. The previous ysocandidate list does have 073121.8-465943, which I had manually added on the basis of the fact that it appeared (blindly) to match the position for the previously known object. HOWEVER, now we know that this is erroneously included due to this position error, and it should be dropped from our list of YSOs. (4) Now we know the answer to the question I posed in the Fall Work page for task3 -- did we recover all of the previously known objects in our fields? no. Are there any we did not recover? yes, one, because of missing fluxes.

Task 4

TASK: for each of the YSO candidates, [investigate them at other bands]

i guarantee you that at least 3 of the YSOs should be dropped because they are not really stars. not telling you which ones! you go figure this out ...

Update from Luisa Fri Dec 17 15:33:39 PST 2010: The YSO candidate list is starting with 30 objects. I went through each of the Spitzer bands that we have, looking at each of the YSO candidates. Here are my notes on what I see in the Spitzer images. I did not look in the 2MASS images. Did you find anything different? The spatial resolution at 2MASS is comparable to IRAC-1, so 2MASS should not reveal galaxies that we did not suspect from the IRAC image.

SSTiau name	    	    
 073049.1-470209   
 073049.8-465806   
 073053.6-465742   very faint m1, but probably there.
 073057.5-465611   
 073106.5-465454   
 073108.4-470130   
 073109.9-465750   
 073110.8-470032   
 073114.6-465842   
 073114.9-470055   very faint m1, but probably there.
 073121.8-465744   multiple srcs on top of one, probably not unique detections DROP
 073121.8-465745   multiple srcs on top of one, probably not unique detections. this is best centered, probably best fluxes obtained here.
 073121.9-465746   multiple srcs on top of one, probably not unique detections DROP
 073136.6-470013   
 073137.4-470021   
 073143.8-465818   
 073144.1-470008   src is offset from core of bright star in i1,i2. real? in i3 can clearly see that it's really another source. computer wins!
 073145.6-465917   
 073243.5-464941   stuck in muck from bright star in i1,i2,i3. fluxes prob hi error. even in i4, hard to tell if real source. what does SED look like? i can't see it in m1.
 073326.8-464842   
 073337.0-465455   very faint m1, but probably there.
 073337.6-464246   very faint m1, but probably there.
 073406.9-465805   
 073425.3-465409   BOOMING bright m1.
 073439.9-465548   off edge m1 (no fluxes possible.)
 073501.1-465442   middle of gal, not true pt src much less YSO. offedge m1. DROP
 073504.7-465514   middle of gal, not true pt src much less YSO. offedge m1. DROP
 073508.1-465544   middle of gal, not true pt src much less YSO. offedge m1. DROP
 073542.2-470126   offedge m1.
 073548.5-470727   near diffraction spike i1, prob ok. offedge m1.

PROBLEM CHILDREN:

Look at how the red circles are nicely centered on the sources, even the fainter ones, in most cases in this zoom-in, except for that cluster of 3 sources on top of the bright object. (I've added some large red lines to draw your eye towards some of the little red circles centered on the YSO candidates.) Something hiccupped here in that one case -- the computer often has problems with the brightest sources because the PSF is a complicated source. The most likely best measurement of the real source is the one best centered on the source. Drop the other two sources as false sources.

Here again, look at how the red circles are nicely centered on the sources -- I've added some large red lines to draw your eye towards the little red circles centered on the YSO candidates. But there seems to be three "sources" within the galaxy. Here, the computer has been fooled by local brightness maxima in the galaxy. These objects are not single young stars. They may indeed be large star-forming complexes in the other galaxy (they seem to have the right colors), but they are not single point sources, so they're not young stars in *our* galaxy. Drop them from the list.

I thought that 073144.1-470008 was going to turn out to be another problem child, but inspection at the longer bands (i3 and 4) reveals that the computer is correct, there really is a distinct source there.

SO now that we've dropped 5 things off the list, the running YSO candidate list is now down to 25 objects.

Task 5

TASK: for the new YSO candidates[...]go get the optical

OK, so this was WAY WAY WAY harder than I thought it would have been. there were TONS of duplicates within the optical catalog, as well as objects with no photometry at all. I did this merging and have emailed around a merged catalog.

Task 6

TASK: [...] make some color-mag and color-color diagrams

I still think you can do this one. look at the IC2118 paper for specific examples and ideas. I haven't seen any examples from anyone yet, so I don't know if you need help.

Task 7

TASK: [...] make SEDs

I still think you can do this one. I sent around examples before, and will send around new examples with the optical included. you need the wavelengths and zeropoints of the optical bands, which I will provide.

Task 8

TASK: [...] SED slopes

Let's wait and see if you get to task 7 before I just go ahead and do this one.

Task 9

TASK: [...] 3-color images with sources indicated

hint: use region files and ds9.