I have a position, how do I find which ARG fields contain it (if any)? SOLUTION

by KWillett scientist, admin, translator

This is a response to discussions in http://radiotalk.galaxyzoo.org/#/boards/BRG0000003/discussions/DRG0000cud, as well as several other times it's popped up on the site. While we don't have a full position seach function implemented in RGZ, what we can provide is this: a list of every subject in RGZ, which should enable the volunteers to do their own searches.

This is in two parts: first, the data. Here's a simple text file (rgz_targets.csv) that has three columns: zooniverse_id, ra, and dec. It looks like this:
```
zooniverse_id,ra,dec
ARG000255t,206.419375,23.38236111111111
ARG000255u,164.2139583333333,23.38225
ARG000255v,251.67925,23.38216666666667
ARG000255w,196.0109166666667,23.38216666666667
....
```
So for any subject, if you want to see it in Talk (including collections, comments, discussion, etc), you can just type it into the web browser, replacing the last part in the URL with the zooniverse_id. For example, http://radiotalk.galaxyzoo.org/#/subjects/ARG0001og2

https://www.dropbox.com/s/bum9qn3l7kdzhpk/rgz_targets.csv?dl=0

The second bit is going from a set of coordinates to any potential fields that might include that point. I've written a short piece of Python code (rgz_cone.py) that takes in as input any point on the sky and returns all RGZ images within a certain radius. To run it, you'll need to have Python on your machine (which will work on any computer operating system), as well as installing the astropy package. Google is your best resource for either of these if you need help.

https://www.dropbox.com/s/l0qf62rx56w5dbu/rgz_cone.py?dl=0

Once you have both the code and data file, open up a Terminal window, and go to the directory where you have both files. Here's an example: to search for RGZ images near the point (RA,dec) = (206.41,23.38), type in the following:
```
python rgz_cone.py 206.41 23.38 3
```
The last number gives the radius in which to search, measured in arcminutes. In the example above, I've chosen 3 arcmin, which is the width of the FIRST images in RGZ.

The code in this example will return this:
```
2 matches within 3.0 arcmin

id,ra,dec,separation [arcmin]
==========================
ARG000255t,206.41938,23.38236,0.535
ARG0002564,206.42362,23.38133,0.755
```
Alternatively - if you don't want to tackle Python, there are lots of other ways to explore the data. The simplest would be opening up the rgz_targets.csv file in a spreadsheet program (like Excel or Google Docs) and sort the RA and dec columns until you find fields near the point that you're looking for.

I'll look into putting this catalog online in a format that's more permanent and can link to other catalogs in the future. However, I know that Zooites are resourceful and I hope many of you can use this data as is. Please share any suggestions, tips, or questions you have on Talk!

Posted November 9, 2015 9:51 PM
by JeanTate in response to KWillett's comment.

This is really cool, KWillett! 😄 Thank you very, very much!! 😃

Alternatively - if you don't want to tackle Python, there are lots of other ways to explore the data. The simplest would be opening up the rgz_targets.csv file in a spreadsheet program (like Excel or Google Docs) and sort the RA and dec columns until you find fields near the point that you're looking for.

If anyone is interested, we can discuss some simple things you can do, with the data in a spreadsheet, that will help you zero in on the rows which are closest to your target position. These may be more efficient, in the end, than doing sorts by RA or Dec ... 😉

Posted November 10, 2015 8:31 PM
by sisifolibre

Thanks KWillett.

Using a spreadsheet (I use OpenOfice) some searches can be done by the ID, usually closer ID ecual closer coordinates I guess. But I think that for other subjects like giants or similar, searches must be done by RA and Dec because they will have a very diferent ID.

On the other hand: which can be the utilities of this list? the searches of ID in RGZ Talk only have success if the object has been already commented.

EDIT now I underestand :

if you want to see it in Talk (including collections, comments, discussion, etc), you can just type it into the web browser, replacing the last part in the URL with the zooniverse_id.

In this way no matter if an object has been comented, you can see it in Talk.

Posted November 11, 2015 7:51 AM
by JeanTate in response to sisifolibre's comment.

I too use OpenOffice! 😃

You can do a cone search in a spreadsheet, by calculating the (angular) distance between your target position and each of the objects/fields in the rgz_targets file. That distance comes from a spherical geometry formula (sorry, too lazy to find a link). If you're using an older PC/laptop/whatever, it may not have enough oomph to do this for all targets, in an acceptable time; if so, it's easy enough to do the cone search over a much smaller number of targets, by first narrowing the RA and Dec ranges to +/-2 degrees (say).

for other subjects like giants or similar

This is what makes RGZ much more exciting than GZ, say! The host of a candidate giant may be quite some distance from either lobe, especially if it's low-z (redshift).

Posted November 11, 2015 3:02 PM
by KWillett scientist, admin, translator

I've added the list as an Excel spreadsheet, if that's easier for anyone. I don't have OpenOffice, but I think it should be able to open that as well.

https://www.dropbox.com/s/p5zgrxr04fq9896/rgz_targets.xlsx?dl=0

Posted November 18, 2015 10:58 PM
by Peter_Dzwig

Thasnks for this Kyle. Had I known avbout it earlier...but great this is data that I needed. Do you have a maximum redshift value for this lot?

Posted December 28, 2016 11:06 PM
by JeanTate in response to Peter_Dzwig's comment.

Happy New Year, 2017 Peter! 😃

I'm not sure if Kyle drops by any more, here in RGZ Talk; after all, he left the team in June 2016.

Do you have a maximum redshift value for this lot?

The FIRST sources in the spreadsheet do not have redshifts as they are detections at a single wavelength (1.4 GHz).

One key goal of RGZ is to get a handle on what the hosts of each of these FIRST sources is, as a WISE source. I imagine that there'll be some very interesting analyses which will be done downstream, associating the identified WISE sources with galaxies or QSOs (or stars!) with redshifts reported in the literature. And we citizen scientists will be able to be a part of many such analyses, even initiating them.

Posted January 8, 2017 4:12 PM
by Peter_Dzwig in response to JeanTate's comment.

Jean, HNY to you too 😃

I guess that my question was poorly phrased. It might have been expressed as "Of the group of sources in RGZ what is (currently) the highest z for which a RGZ source has been identified with an optical counterpart" I assume that some have been identified already.

Peter

Posted January 9, 2017 11:53 AM
by JeanTate in response to Peter_Dzwig's comment.

Hi Peter, and thanks.

"Of the group of sources in RGZ what is (currently) the highest z for which a RGZ source has been identified with an optical counterpart". I assume that some have been identified already.

I don't think anyone is keeping track of things like that, and within this Talk it'd be quite challenging to find out, especially if you're interested in establishing 'the highest' with a high degree of confidence.

I know I've identified quite a few QSO hosts with spectroscopic redshifts (zsp) >2, and may have found some between 3 and 4. I suspect almost all would be classed as STAR by the SDSS photometric pipeline (they'd be pretty remarkable objects otherwise!). Of those classed as GALAXY, and with zsps, I think I found one ~1, and certainly more than handful >0.6.

Of course, there are surely hosts with reliable redshifts but no SDSS zsp, and likely some which are too faint for the SDSS photometric pipeline to regard as an object (and which have a WISE ID) ... maybe one day NED will have tools to find these ...

Posted January 10, 2017 7:58 PM