Starship Asterisk*

Bill Keel, the astronomer who got this project up and running, wrote a nice long blog post about it, Gems of the Galaxy Zoos – help pick Hubble observations! https://blog.galaxyzoo.org/2018/02/02/gems-of-the-galaxy-zoos-help-pick-hubble-observations/ It includes nice explanations of the different ki...

In a different thread, in this same section/board, Chris Peterson mentioned 'bounded errors', and said that there are clever ways to handle these.

That would seem to be pertinent to this, long dormant, thread too.

So I'm bumping it.

Thanks everyone. :ssmile: There are clever ways of drawing error bars in cases like this (where the uncertainty in one direction would place the value outside of physical bounds). There are also analysis techniques for using these kinds of uncertainties in calculations, so they propagate correctly. ...

Consider this thought experiment, conducted in a toy universe. You select tens of thousands of images of galaxies, and discard those in which two galaxies appear to be interacting or overlapping, and those in which the central galaxy appears to be 'edge-on' or highly inclined. You prepare images of ...

I think Jean gave up on us as a serious source of information months ago. I remember having no idea at the time what to write in response to this but it does look like just an odd grouping of distant galaxies to me now. I think a little more context might help too. That's true, and it wasn't just t...

Well, there's a Green Pea in it. And it looks like either a merging pair of ellipticals, or perhaps a foreground lensing effect splitting the one elliptical galaxy into two. I can't tell if all these are in one galaxy cluster or not. If so, I'd guess the Green Pea is not part of the cluster, since ...

Thanks again for your replies, neufer. The question I asked, in the OP, has been answered; to pursue this further - what statistical tests are appropriate for distributions with > four groups, for example; the details of how to do chi-square tests in such cases; and so on - I will find a different f...

So, out of all three 2X2 pairs, is it possible to find just a single inconsistent one? Or must there be at least two? If there are four (or more) G/R/Ps, the patterns of results from the pair testing could be used to identify a single G/R/P which is inconsistent, right? I'm not sure how the chi-squa...

Thanks again neufer. So, for: #103, 33+29 = 62 #203, 1444+1336 = 2780 But what are #100 and #200? If I add the four counts for #101 and #102, I get 588 (not 580). And for #201 and #202, I get 3555. Was "580" a typo? More generally, a "not inconsistent" conclusion would involve do...

Thanks neufer. Yes, I should have asked about in consistency :oops: ; I struggle mightily to understand this (I am entirely self-taught), so please be gentle! You ran three 2x2 contingency table tests (is that the correct way to use the terms?), right? Perhaps if I re-state the question in terms of ...

Can anyone help me with this, please? It's about how you go about trying to decide if two distributions are consistent, statistically speaking; specifically, what statistical test, or tests, is (are) most appropriate to use. Here's the data: N(A) N(B) G/R/P 0043 0046 #101 0264 0235 #102 0033 0029 #1...

I posted this question on four different fora, here in Starship Asterisk*, the Cosmoquest forum, Galaxy Zoo forum, and Galaxy Zoo Talk. I will continue the discussion in the Galaxy Zoo forum. Please come and join in!

Suppose I have a bunch of SDSS galaxies (all spirals), with good - spectroscopic - redshifts and good photometry. Suppose I would like to make estimates of the stellar mass in each galaxy, using just the photometry (and the redshift); specifically, not using the spectra. How would I go about doing t...

Suppose I determine that the position angle (PA) of a galaxy, in one band - observed by SDSS - is -85.4 ± 8.9°, and is 84.7 ± 10.9° in another. Assuming - for now - that the errors have a Gaussian distribution, and that the "±" numbers are 1σ, how do I go about determining if the two (band...

The reference in the FITS standard document is incorrect! :o :shock: It is "Greisen, E.W. & Calabretta, M. R. 2002, A&A, 395, 1061 ", which is entitled "Representations of world coordinates in FITS"; the correct reference is "Greisen, E.W. & Calabretta, M. R. 200...

Thanks again Chris. Reading the FITS standard (per the link you posted), together with the key words in the FITS header, I have most of what I need to make sense of all this. In particular, CTYPE1 is 'RA---TAN'; CTYPE2 'DEC--TAN'; CUNIT1 (and 2) is 'deg'; CRVAL1 and 2 make sense as RA and DEC, expre...

Thank you Chris. In particular, the mJPEG utility. I have three SDSS FITS, cutouts created by GALFIT, all the same size, all centered on the same object; mJPEG gets upset: "Red and green FITS images don't match." From the detailed dump, I see that the values for crval1, crval2, crpix1, crp...

In particular, the mJPEG utility. I have three SDSS FITS, cutouts created by GALFIT, all the same size, all centered on the same object; mJPEG gets upset: "Red and green FITS images don't match." From the detailed dump, I see that the values for crval1, crval2, crpix1, crpix2, and crota2 a...

Its name is SDSS J075137.19+325447.3, and here is its SDSS DR7 spectrum:

The title say it all ... except to clarify: * 'spiral' includes edge-on and lenticulars Follow-on question: which NGC spiral is the largest, physically? Clarifications: * not counting the tidal tails of spirals in mergers * 'largest, physically', as a metric, should be consistent (i.e./e.g. NGC ABCD...

I'd love to check out the color index of this star, to see how the filters of SDSS "interpret" the actual color of stars. Well, I'm not going to find out about the color index of this star. I followed the link to the Galaxy Zoo page, and while I got excellent coordinates for the star that...

http://farm2.static.flickr.com/1141/5117690260_ac30b1e3b2_b.jpg Stellar190 got fascinated by NGC 1142, and wrote a whole Galaxy Zoo Object of the Day on it, stardate 27th October, 2010 . This image is her own version of the SDSS data, made by downloading the FITS data and playing working with the f...

http://zoo-hst.s3.amazonaws.com/90040267.jpg Looks vaguely like some bad art from the 1960s, eh? It's actually a rather bright double star imaged by the Hubble Space Telescope; AHZ40006z8 is its Galaxy Zoo identifier. Alice posted this as the Galaxy Zoo Object of the Day , stardate 23rd September, ...

http://s3.amazonaws.com/zoo2_extra/334182.jpg The object goes by the incredibly simple name of SDSS J233604.13+000440.6 (not!), but I think 'arrow pierced galaxy' is better. It's featured in the Galaxy Zoo Object of the Day , stardate 22nd October, 2010 , by Lightbulb500. As far as I know, it has n...

http://zoo-hst.s3.amazonaws.com/90022411.jpg http://zoo-hst.s3.amazonaws.com/90029358.jpg Budgieye, in her Galaxy Zoo Object of the Day , stardate 8th October, 2010 , posted several examples of cosmic ray artifacts in Hubble Zoo images. Most times the raw images are cleaned of these artifacts befor...