Galaxy Zoo Starburst Talk

Detailed investigation: outliers and anomalies in 'redshift bin #10'

  • JeanTate by JeanTate

    Before we can start cleaning (see What is needed to get a clean QS and a clean QC?), I think it might be interesting to investigate a somewhat random sample, to see just how many objects - in either catalog - might be outliers or anomalies. That's what this thread is about.

    I combined the latest version of the QS and QC catalogs (by downloading them), combined them, and removed all the duplicates.

    How to get a 'random sample'?

    Well, I could simply generate 100 (say) random numbers in [0,1], multiply them by 5918 (=2*3002-861), and pick the objects with those 100 index values (having ranked the list in some fashion, perhaps even randomly?), making sure to have some 'spares' on hand in case the same index number comes up more than once. That's a good idea, and I might try it later.

    What I actually did was sort the 5918 objects by their redshifts, remove the two with 'wrong/highly uncertain' redshifts2, divide the remainder into 24 redshift bins (of equal size=number of objects±1), and choose a bin at random. That's how I came up with 'redshift bin #10'! 😮

    The minimum redshift in redshift bin #10 is 0.085967541 ( AGS00004h8), and the maximum is 0.0894129 ( AGS00000qr); there are 116 QS objects in this bin, and 130 QC ones.

    Let the detailed investigation begin! 😃

    1 3002 is the number of objects in each of QS and QC; 86 is the number of duplicate objects

    2 AGS00002ak and AGS00002ds

    Posted

  • JeanTate by JeanTate

    Here are the 130 QC objects, ranked in order of their Petro_R50 ("R50") values (DR10 60x60 image cutouts, scale=0.4):

    AGS00004h8AGS00003l0AGS000046pAGS00003zkAGS00002vrAGS00003ftAGS00002ptAGS00002dyAGS00002jwAGS000040c
    AGS000034sAGS00003orAGS000048zAGS00004ibAGS00003zaAGS00003ttAGS00003vtAGS00003maAGS00002e0AGS00004j3
    AGS00003tzAGS00004bcAGS00002nuAGS00002nqAGS0000302AGS00002p3AGS00002khAGS00004d7AGS00002jxAGS00002wl
    AGS00002vcAGS000047cAGS00003psAGS00004gbAGS00002w5AGS00003pyAGS00002rmAGS00003e8AGS00003fhAGS000048q
    AGS00003ldAGS0000344AGS00003ovAGS0000438AGS000042kAGS00003z6AGS00002njAGS00003blAGS00002rxAGS00004dd
    AGS00002svAGS000048mAGS00002mmAGS00003uwAGS00003l8AGS00003paAGS00002knAGS00002erAGS000031oAGS00003ub
    AGS0000318AGS00002stAGS000043yAGS00002yiAGS0000312AGS000044hAGS00004cbAGS00002r3AGS00002hdAGS000049l
    AGS0000380AGS000040sAGS00002m4AGS00004l6AGS00002ycAGS00003zgAGS00004h2AGS00002hrAGS00002ekAGS00004f5
    AGS00002osAGS00002cmAGS00003woAGS000049kAGS00003rwAGS00003p6AGS00002d2AGS000039dAGS00004f4AGS00002mn
    AGS00004dgAGS00002poAGS00004hiAGS00002pvAGS00004liAGS00003fiAGS000041mAGS00003gfAGS0000315AGS00004hp
    AGS00003iuAGS00003s9AGS00002t2AGS00003opAGS000039rAGS00003poAGS0000394AGS00004biAGS00004hcAGS00002dx
    AGS00002tcAGS00002goAGS00002k1AGS00004e2AGS00004a3AGS00003n1AGS00003ifAGS00004b6AGS00004ixAGS0000419
    AGS00003j2AGS00002edAGS00002f7AGS00003y4AGS00004f7AGS00003p9AGS00004jvAGS00002tsAGS00002zyAGS00002vf

    Posted

  • JeanTate by JeanTate

    And the 116 QS objects, same ranking (etc):

    AGS000005dAGS00000upAGS00000wbAGS000003fAGS00001h0AGS00001d3AGS00001jwAGS000026lAGS000012kAGS00000jn
    AGS00001vyAGS0000205AGS000006mAGS00000wiAGS00001m9AGS00001b9AGS000027yAGS000009uAGS000016jAGS000018a
    AGS00000xmAGS0000220AGS00001beAGS000002gAGS00000wmAGS00001htAGS00000hqAGS0000110AGS00001fqAGS00001nw
    AGS000007yAGS0000201AGS000022eAGS000019zAGS00000yeAGS00000hhAGS00001s8AGS000010zAGS00000cdAGS000022m
    AGS000021eAGS000027pAGS000003eAGS00001exAGS00001czAGS0000034AGS0000171AGS00000f1AGS00001ilAGS00001o1
    AGS00001zqAGS00000bjAGS00000ruAGS000018zAGS000028wAGS000013xAGS00000aqAGS00000ooAGS00000uwAGS000026k
    AGS00001v1AGS000004nAGS000003lAGS00000qlAGS000017gAGS000027jAGS000016tAGS00000z9AGS00001ekAGS000025o
    AGS00000z7AGS000001nAGS00000joAGS0000016AGS000012uAGS000006rAGS00001ybAGS00001cdAGS00001xuAGS00000p8
    AGS00001bbAGS00000lyAGS0000085AGS00000q5AGS000004iAGS00000wlAGS000012gAGS00001niAGS000020uAGS00001u1
    AGS00000lbAGS000010gAGS00000o7AGS00002b2AGS00000bdAGS00001x8AGS0000024AGS00000fnAGS000029nAGS00000y1
    AGS00000q6AGS00000aoAGS000013qAGS00000r4AGS0000155AGS00001zjAGS00000n4AGS00001eeAGS00000r5AGS00001ll
    AGS0000059AGS000028xAGS000015sAGS0000192AGS00002b9AGS00000qr

    Posted

  • JeanTate by JeanTate

    Nothing stands out - to me - as an anomaly in these two sets of images ... except for two:

    enter image description here

    This is AGS00002vf, a QC object, is a merger, with the smallest/faintest of the three obvious 'pieces' of the merger as 'the object'. R50 is given as 6.579" in the catalog, which is the same as the R50 value in DR7. However, this seems to be a failure of the deblender; the main object is surely 587742551211769894:

    enter image description here

    In DR9, R50 for AGS00002vf is 0.60" (and R90 1.13), and for 587742551211769894, they are 5.85 and 15.59, respectively.

    enter image description here

    AGS00000n4, a QS object. It too is a (spectacular!) merger. DR7 and DR9 disagree about R50 (and R90) - 3.27±0.15 (7.05±1.0) vs 2.34±0.22 (5.61±1.7), respectively - but not so radically as for AGS00002vf.

    Apart from the general question of "what is the 'galaxy' in 'post-quenched galaxy', where it's clearly an unfinished merger?" - for which we really should have a consistent answer, in order to be able to do robust analyses - these images also leave me wondering how good (and how useful!) R50 is, for very long and skinny Eos, especially those with a tiny bulge (or none at all).

    Posted

  • JeanTate by JeanTate

    As Brooke/vrooje klmasters says, in the First go at exploring data: Colors of quench versus control thread, "really recently starformation shows up in the u-band, while r-band will reveal more mature stars." We don't have images displaying (u-r), but maybe showing the galaxies in redshift bin #10 in (increasing) order of (u-r) will reveal an interesting pattern? Perhaps even some anomalies?

    Here are the 130 QC objects, sorted in just such a way (DR10 cutouts, 60x60, scale 0.2). AGS00003ov has the lowest (u-r), 1.31, followed by AGS00004a3 and AGS00002nu (1.43). At the other end, AGS0000380's is 3.14, and AGS00004d7's 3.19.

    AGS00003ovAGS00004a3AGS00002nuAGS00004b6AGS00004jvAGS00003ldAGS00002tcAGS00002mmAGS0000438AGS00003iu
    AGS00002p3AGS00002tsAGS00003uwAGS00003zgAGS00002hdAGS00003y4AGS00004e2AGS0000419AGS00002poAGS00002os
    AGS00004liAGS00003p6AGS00002njAGS00004l6AGS00002knAGS00003zkAGS000049lAGS00002m4AGS00004f7AGS00003l8
    AGS00003j2AGS00003blAGS00003opAGS000044hAGS00002edAGS00003fhAGS00003paAGS00002d2AGS00003pyAGS00003n1
    AGS00004ixAGS00004hiAGS00004cbAGS000047cAGS000041mAGS00002ycAGS00004hcAGS00003fiAGS00002r3AGS00002jx
    AGS00002zyAGS00004ddAGS000039rAGS00002svAGS00002yiAGS000031oAGS00003ttAGS000049kAGS00004dgAGS00002vf
    AGS00002stAGS00002goAGS00003ifAGS000046pAGS0000344AGS00003woAGS00003rwAGS00002erAGS00002t2AGS00002rx
    AGS00004f5AGS000040sAGS00004f4AGS00002ekAGS00003z6AGS00002pvAGS00003orAGS0000315AGS00004hpAGS00002nq
    AGS0000312AGS000048mAGS00002k1AGS0000394AGS00003poAGS00002mnAGS00002f7AGS00004j3AGS00003ubAGS00003ft
    AGS00002cmAGS00003p9AGS000048zAGS000042kAGS00004biAGS00002khAGS00002dyAGS0000318AGS0000302AGS00004h8
    AGS00002rmAGS00003vtAGS000039dAGS00004gbAGS00002jwAGS00003l0AGS00002w5AGS00003psAGS00003e8AGS00002pt
    AGS000034sAGS00003s9AGS00003tzAGS00002e0AGS000043yAGS00004bcAGS00003maAGS00002wlAGS000040cAGS00002vr
    AGS00003zaAGS00004h2AGS00003gfAGS00004ibAGS00002hrAGS00002dxAGS00002vcAGS000048qAGS0000380AGS00004d7

    Posted

  • JeanTate by JeanTate

    Here's the same thing, for the 116 QS objects.

    AGS00000jn begins the parade, with (u-r)=1.41, followed by AGS0000024 (1.43) and AGS000017g (1.57). At the other end, (u-r) for AGS00000ao is 3.15, AGS00000ye's is 3.23, and AGS00000f1's is ... wait for it ... 6.84!

    AGS00000jnAGS0000024AGS000017gAGS00000lbAGS00000r4AGS00000lyAGS00001exAGS000004nAGS00000hhAGS00001cd
    AGS00002b2AGS000010gAGS000026kAGS000012gAGS00002b9AGS00000bjAGS00001ybAGS000015sAGS000027pAGS000006r
    AGS00001xuAGS000027jAGS00001zqAGS00000q6AGS00000hqAGS000018zAGS000016jAGS0000205AGS000018aAGS00001ll
    AGS00001o1AGS00001u1AGS000006mAGS00001s8AGS00000xmAGS0000059AGS0000034AGS00000p8AGS0000085AGS00001ee
    AGS00001htAGS000013qAGS00001v1AGS000010zAGS000009uAGS00000r5AGS00001h0AGS00000wbAGS00000n4AGS00000up
    AGS000028wAGS00000fnAGS00000wiAGS000005dAGS000022eAGS00000aqAGS00001jwAGS00001ekAGS00000z7AGS000003f
    AGS00000bdAGS00001beAGS000025oAGS000003lAGS00000wlAGS000029nAGS00000q5AGS00001b9AGS00001fqAGS000020u
    AGS000002gAGS000004iAGS00000cdAGS00001niAGS00000uwAGS00001zjAGS00000y1AGS00000z9AGS0000220AGS000026l
    AGS000028xAGS00001czAGS0000155AGS000021eAGS000016tAGS000003eAGS00001d3AGS00000o7AGS00001m9AGS0000171
    AGS00001bbAGS00000qlAGS000012kAGS000019zAGS00000ooAGS0000016AGS000027yAGS000001nAGS000022mAGS000007y
    AGS00001vyAGS0000110AGS0000201AGS000012uAGS00000qrAGS00000ruAGS00001ilAGS00001nwAGS0000192AGS000013x
    AGS00000wmAGS00001x8AGS00000joAGS00000aoAGS00000yeAGS00000f1

    Posted

  • JeanTate by JeanTate

    There's just one object whose (u-r) color seems, well, wild; the QS galaxy AGS00000f1:

    enter image description here

    Its enormous (u-z) value (6.84 mags) comes from its extremely faint u-band modelmag - 24.68±2.45 (in DR9 it's 25.13±1.90) - rather than an especially bright r (17.84±0.01). Even at the extreme bright end, the u-band mag is still far to faint to bring this galaxy within range of the others.

    enter image description here

    Anything else?

    Well, have the superior DR10 image processing routines shown that there are foreground stars almost 'on top of' galactic nuclei, in two QS objects?

    enter image description here AGS0000201 enter image description here

    enter image description here AGS000025o enter image description here

    This galaxy, AGS000006r - NOT anomalous in any way that I can tell! - shows the superiority of the DR10 images:

    enter image description here enter image description here

    But does it, too, sometimes mislead? Consider AGS00002os; is there a faint foreground star on top of (or a faint galaxy in the background of) the somewhat disturbed barred CW spiral? Or is it just an artifact? Or ...?

    enter image description here enter image description here

    Posted

  • JeanTate by JeanTate

    This is a check I would not normally even have thought of doing; however, having discovered that the Quench project images do not match the SDSS DR7 ObjIds for 13 QC objects1, I decided to check the SDSS DR7 entries for each of the 246 redshift bin#10 objects, to see if they match what's in the QS and QC catalogs that I downloaded.

    This is a fairly simple CasJobs query, so I also downloaded the R50 and R90 values (as well as their errors).

    The R50 values match, to ~six significant figures; good.

    However, the RA and Dec values rarely do 😮

    Here are two examples, the DR9 image you get when you click on the "View on SkyServer" link in the GZ/Quench Examine page, then the DR7 'cross-hairs' one, for the DR7 ObjId; first AGS000013q (588017626682556693):

    enter image description here enter image description here

    Next, AGS00001yb (587741387809292832):

    enter image description here enter image description here

    What's going on?

    I'm not 100% sure, but for these two at least it's a case of the QS/QC catalog values - especially the RA ones - being rounded down too much. Not only on the GZ/Quench Examine page, but also in the downloaded catalog, the RAs have only three significant digits - 154.964 and 119.576 for the two examples above, respectively - but you need at least four, preferably five, to pinpoint the location of the center of the spectroscope's fiber.

    But, are there any cases like AGS00001bl (588017726012129327)1, in the redshift bin #10 objects? I'm still checking, and will update this post when I've finished. 😃

    UPDATE: it seems it's a lot more complicated than simply too few significant digits. For example, the live link sometimes does strange things. Consider AGS00001xu (587741531719139429; catalog (RA, Dec) = 190.17, 29.0572). When you click the "View on SkyServer" link, you get this (DR7 ObjId 587741531719139429 for comparison):

    enter image description here enter image description here

    The URL for the DR9 image says it's centered on "ra=190.17458653&dec=29.05313864"! 😮 So it would seem that the GZ Examine code does something like 'search for the DR9 primary galaxy object closest to these coordinates', and because the coordinates aren't precise enough, it sometimes makes a big mistake.

    1 I discovered something similar, in terms of a much less severe mismatch, for AGS00001bl (588017726012129327). This is the DR9 image you get when you click the "View on SkyServer" link in the GZ/Quench Examine page; next to it is the DR7 object 588017726012129327:

    enter image description here enter image description here

    This is a complicated case; the nucleus/bulge has no spectrum, but there are two, of two different clumps in the arms. But it's not in bin #10!

    Posted

  • JeanTate by JeanTate in response to JeanTate's comment.

    In choosing to work with DR7 ObjIds - and their associated (RA, Dec) coordinates - but to display using the DR9 SkyServer, the GZ Examine tool sometimes gets tripped up ... by inconsistencies between DR7 and DR9! 😮

    Take AGS00001xu (DR7 ObjId 587741531719139429). This is what you get when you use DR7 Navigate and enter (190.17, 29.0572) as the location:

    enter image description here

    The blue circle is a 'photometric object', and the red square an 'object with spectra'1; the RA of AGS00001xu is 190.170417 (to six significant figures), hence the obvious offset between the cross-hairs and the location of the photometric object.

    Here's the same thing, using DR9:

    enter image description here

    DR7 587741531719139429 is still a spectroscopic object (red square), but is no longer a photometric object (no blue circle)! 😮 😮

    So it would seem that SkyServer jumps to the closest photometric object, given the (RA, Dec) coordinates, but not the location specified ... the URLs give this game away.

    This also explains what happens with AGS00001yb (DR7 ObjId 587741387809292832), above. The lack of precision in RA means that the DR9 SkyServer pointed to a photometric object close to DR7 ObjId 587741387809292832, one without a spectrum (DR7 first):

    enter image description here enter image description here

    Does this lead to mismatched objects in the downloaded QS and QC catalogs?

    I can certainly come up with a scenario or two where it might, but for redshift bin #10, it seems that the only mismatches are between what the DR9 SkyServer displays and what's actually in the two catalogs.

    1 Quite coincidentally, you can see that the fiber covering fraction is high; the blue circle is ~5" in diameter, while the fiber aperture is 3", add in ~1.4" seeing (FWHM), and the spectrum of 587741531719139429 is of light from just a bit smaller than the blue circle

    Posted

  • JeanTate by JeanTate in response to JeanTate's comment.

    I just posted this, concerning the redshift bin #10 QS object AGS00000qr, over in the Galaxy Zoo forum (What are the galaxy's ugriz magnitudes?); I'll copy any replies here too:

    The galaxy is SDSS J085928.63+455113.2, DR7 ObjId 587731887351857350:

    enter image description here

    It has several photometric objects as 'neighbors', two of which - 587731887351857353 ("NE1") and 587731887351857351 ("NE2"), both "GALAXY", photometrically speaking - are, most of us would say, simply part of the galaxy itself:

    enter image description here

    The photometry of 587731887351857350 is, per the SDSS DR7 Explore page, (u, g, r, i, z) = (19.32, 17.38, 16.61, 16.09, 15.77); the (u-r) color is thus 2.71.
    That of NE1 is (19.99, 21.78, 22.84, 22.37, 22.81), and its (u-r) color is -2.85.
    And NE2 (22.00, 21.93, 21.93, 21.63, 20.78), giving a (u-r) color of 0.07.

    In SDSS the photometric magnitudes quoted, for galaxies, are modelmags, the output of a part of the pipeline which selects a 'best fit model' for the galaxy, and derives the magnitudes from that model.

    As NE1 and NE2 are, almost certainly, part of the main galaxy (and not separate, overlapping, galaxies), I can combine the photometry, to get (18.79, 17.35, 16.60, 16.08, 15.76), and a (u-r) color of 2.19.

    Now the g, r, i, and z mags hardly change; the differences are all1 ~the same as the quoted error (0.01, in all four cases). However, the u-band modelmag is quite different, 0.53 mags in fact, which is much greater than the quoted error (0.08). More dramatically, the (u-r) color has gone from 2.71 to 2.19.

    What to do?

    Work with the main - central, brightest, etc - component alone, and assume that the other pieces are never bright enough (or differ wildly enough, in color) to matter? Perhaps double or triple the quoted errors to CYA?

    Diligently track down each errant stray piece, and add them all back, to get a more realistic photometric picture of the galaxy?

    Something else?

    1 the g-band one is a bit bigger, 0.035

    As you might guess, it was AGS00001yb (DR7 ObjId 587741387809292832) that got me thinking about this. While the differences for AGS00001yb are trivial - adding the two smaller pieces (which are, interestingly, both "STAR") makes essentially no difference to any color - I guessed that this would not always be the case. And I checked only two other QS objects (yes, both Eos) before finding AGS00000qr.

    Posted

  • JeanTate by JeanTate in response to JeanTate's comment.

    mlpeck replied:

    I'd vote for something else, namely use DR8+ data (link goes to DR10 explore, I hope). Note below that a photometric object has been dropped. The photometry for the object coinciding with the spectrum position looks reasonable to me at least.

    enter image description here

    Posted

  • JeanTate by JeanTate in response to JeanTate's comment.

    What difference does this make, going from DR7 to DR10?

    In DR7, the edge-on disk galaxy has (u, g, r, i, z) photometry of (19.32, 17.38, 16.61, 16.09, 15.77), and a (u-z) color of 2.71; in DR10 it is (18.92, 17.35, 16.6, 16.08, 15.75), and a (u-z) color of 2.32. Adding in the photometric object at the NE tip changes the DR10 photometry by amounts that are ~within the stated error bars, and the (u-z) color is almost the same.

    At least in this case, the DR10 photometry seems more robust.

    Posted

  • JeanTate by JeanTate in response to JeanTate's comment.

    To what extent are the "Yes, this disk galaxy could be edge-on" and "This is a cigar-shaped smooth galaxy" overlapping classifications? If no true elliptical is more elongated than E71, then any 'cigar-shaped' galaxy with an AB2 of <~0.3 must be an edge-on disk galaxy (Eos).

    Here are DR10 images (scale=0.2) of all such galaxies; also all 'disk_edge' galaxies. Ranked, in order of the mean r-band AB value.

    First, cigar-shaped QC galaxies (all of them); AB ranges from 0.13 to 0.31:

    AGS00002mnAGS00002goAGS00002k1AGS00004hiAGS0000312

    AGS00004hcAGS00004ddAGS00003if

    Next, cigar-shaped QS galaxies (all of them); AB ranges from 0.19 to 0.27:

    AGS0000155AGS00000wmAGS000013qAGS00000wiAGS00001ee

    AGS00000bj

    Edge-on QC galaxies (first row), and - in the second row - NOT edge-on disk QC galaxies, with AB values less than or equal to 0.36 (the max such, for the edge-on ones):

    AGS00004hpAGS0000380AGS00002f7AGS00002pv

    AGS00004biAGS00002t2

    Edge-on QS galaxies (first row), and - in the second row - NOT edge-on disk QS galaxies, with AB values less than or equal to 0.32 (the max such, for the edge-on ones):

    AGS00000qrAGS0000192AGS00000p8AGS00000lyAGS0000034

    AGS00001ekAGS000006rAGS00000q6AGS00001ni

    And finally, two edge-on QS objects, in the first row, whose AB values are 0.34 and 0.55, respectively; in the second row, the two NOT edge-on disk QS galaxies, both with AB values of ~0.55:

    AGS00001d3AGS00000o7

    AGS0000059AGS000015s

    OK, not quite ... there are three smooth galaxies, classified as "In between", with AB values of 0.28 (the first one, the only QS), 0.30, and 0.31:

    AGS00001ybAGS00003pyAGS00003pa

    1 In the Hubble classification scheme, an elliptical's 'ellipticity' is quantitative, derived from the ratio of the semi-minor axis length (b) to the semi-major one (a) as follows: 10*(1-b/a). More in this GZ forum thread: What is the relationship between 'ellipticity' and 'axis ratio'?

    2 There are at least ten "AB" parameters in the SDSS DR7 PhotoObj table (and errors for each); they are all estimates of the ratio of the semi-minor axis length (b) to the semi-major one (a) ... one for each band, and one for each of the two radial profile models applied ("exponential" and "deVaucouleurs")

    Posted

  • jules by jules moderator in response to JeanTate's comment.

    Good call Jean! I've been looking at my set of edge on galaxies and wondering the same thing. Looking at your images there doesn't appear to be a clear distinction between the 2 categories. Hope a scientist drops by to answer this one.

    Posted

  • mlpeck by mlpeck

    I'm not sure I understand a few points. Are the NOT edge on galaxies ones that the GZ classifiers decided weren't edge on but the SDSS photo pipeline estimated a low value of the ratio a/b?

    I had a personal rule for classifying. Any time I was tempted to call something smooth and cigar shaped I picked edge on disk instead.

    I wonder why both options were even offered. I suppose edge on lenticulars could be seen as smooth and cigar shaped, but I expect real lenticulars are scattered among several classifications.

    Posted

  • JeanTate by JeanTate in response to jules's comment.

    I think it's a bit more complicated than that.

    The FIRST classification question - "Is the galaxy simply smooth and rounded with no sign of a disk?" - concerns smoothness and roundedness, so an elongated object which is smooth (and rounded 😉) gets the 'Smooth' vote. At the next question - "How rounded is it?" - you don't get a chance to say if you think it could be an edge-on object. While you and I (and mlpeck!) might agree that most, possibly all, the 'cigar-shaped' objects here do have features, we'd be being a bit unfair ... these are DR10 images, not the DR8/9 ones served up in Phase 1 (I'll have a go at posting these 14 objects - and the edge-on ones too - as they appear in DR8/9, later).

    Perhaps more interesting - to me anyway - is that 'rounded' does not include 'having pointy ends' 😃 And several of the 'cigar-shaped' galaxies seem, to me, to have pointy ends (again, though, based on DR10 images).

    On the other hand, I think all the objects classified as edge-on do have features ... if you also allow that 'being extremely thin and skinny' is a 'sign of a disk' 😉

    Finally, this is just one, very narrow, redshift range; I expect that the mapping of zooite classifications to Hubble type (or similar) may be different in different redshift ranges (or, somewhat similar, different size-on-the-sky ranges).

    I don't think this matters much, in terms of analysis - there are other criteria we can use to say whether an object is more likely to be and ETG than a disk with on-going star-formation (or similar) - as long as there are no apparent systematic differences between QS classifications and QC ones ... a key advantage of having each QS object paired with a QC one is that it greatly reduces the scope of systematic effects!

    Posted

  • JeanTate by JeanTate in response to mlpeck's comment.

    Are the NOT edge on galaxies ones that the GZ classifiers decided weren't edge on but the SDSS photo pipeline estimated a low value of the ratio a/b?

    Yes.

    I wonder why both options were even offered.

    It's a good question; I think there may have been an expectation that E6 and E7 galaxies would classified as 'cigar-shaped', and that most zooites - like you - would have selected 'features or disk' for highly inclined disk galaxies, even if they appeared smooth (and rounded).

    Posted

  • JeanTate by JeanTate in response to mlpeck's comment.

    I'll have a go at posting these 14 objects - and the edge-on ones too - as they appear in DR8/9, later

    Here are the QC cigar-shaped galaxies, in the same order as in my earlier post, with the same size (120x120) and scale (0.2), but from DR9 (first row), with the corresponding DR10 image immediately below:

    AGS00002mnAGS00002goAGS00002k1AGS00004hiAGS0000312
    AGS00002mnAGS00002goAGS00002k1AGS00004hiAGS0000312
    AGS00004hcAGS00004ddAGS00003if

    AGS00004hcAGS00004ddAGS00003if

    And the QS cigar-shaped galaxies (same deal); for the last one, the DR10 image is next to (rather than under) the DR9 one:

    AGS0000155AGS00000wmAGS000013qAGS00000wiAGS00001ee
    AGS0000155AGS00000wmAGS000013qAGS00000wiAGS00001ee

    AGS00000bj AGS00000bj

    And the QC edge-on disk galaxies (DR9 images, then DR10 ones):

    AGS00004hpAGS0000380AGS00002f7AGS00002pv

    AGS00004hpAGS0000380AGS00002f7AGS00002pv

    The first five QS edge-on disk galaxies:

    AGS00000qrAGS0000192AGS00000p8AGS00000lyAGS0000034

    AGS00000qrAGS0000192AGS00000p8AGS00000lyAGS0000034

    And the last two (I made the field bigger for the last one, to try to understand why it was classified 'edge-on'):

    AGS00001d3 AGS00000o7

    AGS00001d3 AGS00000o7

    Posted

  • JeanTate by JeanTate

    AGS00001x8 (DR7 587741601492238440), a QS object, has a u-band modelmag of 20.12±0.11. Adding that of the photometric object which is clearly part of the galaxy itself, the u-band modelmag becomes 19.69. In DR10, there's just one photometric object, and it has a u-band model mag of 19.83±0.09.

    enter image description here

    Posted