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Topics - JeanTate

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Many papers are based on values for several key parameters derived from MPA-JHU data products. These include various line fluxes (and their errors), the 4000 Å break strength ("D4000", and its error), velocity dispersion ("V_DISP", and its error), and the star-formation rate ("SFR").

The methods used to produce these estimates are described in a number of papers, principally Brinchmann+ 2004, Kauffmann+ 2003, and Tremonti+2004 (see above link for details).

I have downloaded and read each of these, looking specifically to understand how the data products address:

 - spectra contaminated by overlapping/foreground galactic stars (including the diffraction spikes - diffspikes - from very bright stars, which may be several arcmins from the galaxy)

 - spectra contaminated by overlapping - either foreground or background - galaxies, whether at similar or quite different redshifts

 - SDSS spectra with some regions masked out (these regions may be as small as a few pixels, or as large as ~1000+ Å)

 - SDSS spectra whose redshift estimate carries the warning "SMALL_DELTA_CHI2".

I found nothing; no mention in any of the papers of any of these. Although none seem to come out and say it openly, they all seem to very firmly assume that each and every spectrum they let their pipeline(s) loose on is 'good' (no masked regions, no poorly subtracted sky lines, etc) and is of a single system of gravitationally bound stars, gas, dust, and perhaps an AGN.

Yet there are hundreds of objects in the Quench project, and very likely tens of thousands in the full MPA-JHU catalog, which have either 'bad' spectra, spectra containing more than one redshift system, or both!  :P

How do astronomers decide which among these many hundred should be excluded from analyses which use the values of the MPA-JHU parameters.

Specifically, how can such decisions be made in an objective, quantitative, reproducible, scientifically-acceptable manner?

Consider AGS00001c9 (SDSS J152907.25+302944.5; DR7 ObjId 587736942525415485), seen here in DR9:

A diffraction spike from (of?) the neighboring bright star crosses the galaxy. If a non-BOSS* spectrum had been taken at the same time (it wasn't), it would have captured light from the star ... as can be seen here (the 3" fiber aperture would touch the inner ends of the cross-hairs):

As I understand it, in general the orientation - on the sky - of diffraction spikes depends on the type of telescope mount, and the altitude and azimuth of where it's pointed, at the time an image/spectrum is taken. So, in general, if an image and a spectrum of an object close to a bright star are taken at (very) different times, they won't both be diffspiked.

But is that true of SDSS images and spectra?

* BOSS spectra have 2" diameter fibers

... the DR9 galSpecLine ("Emission line measurements (from MPA-JHU spectroscopic re-analysis) for this spectrum") says they're both in emission?  ???

I have come across many examples, in the Quench project, among both the Quench sample (QS) and control (QC) objects.

Here's a particularly obvious one, a QS object, AGS00001xa, SDSS J114159.39+265700.0 (DR7 ObjId 587741601491517466, SpecObjID 2500685054489946112):

DR9 image:

And two screen-shots from the interactive spectrum (the red line is "Best Fit"):

The halpha_flux is given as 65.1764±8.19592, and the hbeta_flux as 0.063206±6.038076. Yes, "Warnings: MANY_OUTLIERS"; however, there are plenty of examples without such a warning.

Object of the Day / Friday, 21 February, 2014: Very Strange Spirals?
« on: February 21, 2014, 03:12:33 pm »

No, that's not a strange spiral!  :P That's M87, perhaps the most famous giant-elliptical-with-an-active-SMBH-and-jet; you can see the jet in the optical in this DR10 SDSS image (it's the small white streak at ~2 o'clock).

If we change the scale in a bit, and switch to the radio part of the spectrum, the jet is much more obvious, and we can also see huge clouds of plasma (hot, ionized gas), called lobes ... and the stars have disappeared (source, data is from the Very Large Array radio telescope):

Radio jets and lobes and giant elliptical galaxies are common companions; the super-massive black holes (SMBHs) associated with AGNs (active galactic nuclei) in elliptical galaxies somehow seem to often produce one or two radio jets and/or radio tails and/or lobes1.

The galaxy in the center is, obviously, not an elliptical. It is also - obviously - associated with a pair of radio jets/lobes. This galaxy is called 0313-192  ::) and is the subject of a 2006 paper by W. Keel, R. White, F. Owen, and M. Ledlow2 (you might recognize the first author ... he's none other than our very own zooite, NGC3314!).

Since 2006, a small number of papers have reported similar spiral/radio jet/lobe associations; unfortunately, all the objects seem to be like 0313-192, outside the SDSS footprint!  :(

So, there are (tens of? hundreds of??) thousands of ellipticals-with-jets/lobes, but just a tiny handful of spirals-with-jets/lobes, maybe only three. Or, as raynorris (scientist) said, on December 19 2013, over in Radio Galaxy Zoo (RGZ) Talk:

Keep an eye out for any #hourglass sources that seem to be hosted by galaxies that look spiral in the infrared. These objects are incredibly rare in the local Universe (only 2 or 3 known) and we may not see any in Radio Galaxy Zoo, but if someone does find one, that would be worth writing a paper about (with the discoverer as co-author, of course). The rarity of radio-loud spirals is thought to be because the radio jets heat up and disrupt the gas in the spiral, switching off star formation, and turning the galaxy into a "red dead" elliptical. But we might find one or two where the jets have only just switched on and haven't yet destroyed the spiral.

That is a compilation of SDSS DR10 images of galaxies which seem to be associated with jets/lobes, found by RGZ zooites; respectively (click the links for details): infobservador (ARG0002zck, SDSS J154336.07+110512.9), WizardHowl (ARG0001zj8, SDSS J122640.22+253855.5), infobservador (ARG0002esa, SDSS J140535.56+190612.9), and WizardHowl3 (ARG00022wh, SDSS J112811.63+241746.9). It's not complete - there are certainly others which have been reported by zooites, in RGZ - but they're the only ones I could find after an hour or two's searching4 (and which are more than a spiral associated with radio emission only in/from the nucleus/bulge).

Can you find spirals with jets or lobes, 'hourglass' or 'doublelobe' radio sources? Come along to RGZ and start classifying!  ;D

1 for more on this topic check out the GZ blog posts Tailed Radio Galaxies: Cometary-Shaped Radio Sources in Clusters of Galaxies (Part 1), More Information on Tailed Radio Galaxies (Part 2), How do black holes form jets?, The Curious Lives Of Radio Galaxies – Part One, and The Curious Lives of Radio Galaxies – Part Two (there are more, this is just a 'starter selection')

2 The image is from Hubblesite, "Credit: NASA, W. Keel (University of Alabama), M. Ledlow (Gemini Observatory), F. Owen (NRAO) and AUI/NSF"

3 Unfortunately, I don't seem to be able to make composite SDSS/radio images  :'(

3 Talk's search tool has got to be one of the primitive, inflexible, tiresome search tools ever invented!  >:(

ETA: I've added some names to the RGZ candidates, to more easily keep track of them

Object of the Day / Saturday, 15 February, 2014: Publication = Discovery
« on: February 15, 2014, 01:57:20 am »
Or, if you don't publish what you found, you cannot be said to have discovered it.  :'(


That's SDSS J114831.02+124344.5 (DR7 ObjId 588017704003043340; DR8 1237661950251237389). Its photocenter is a different SDSS object, SDSS J114830.66+124347.2 (DR7 ObjId 588017704003043337, DR8 1237661950251237398), and there are several others, all parts of the same galaxy.


A simple, far-from-exhaustive search that I did found this galaxy in dozens of posts, referenced by several different ObjIds (or other identifiers), by many different zooites, over many years; the earliest was one by Caro, on August 23, 2007, in the Clusters of Galaxies thread (Caro made no comment, other than to give a DR7 ObjId)1.

However, the post which references this galaxy that I want to focus on, in this OOTD, is perhaps the most recent; this one by c_cld, in the Do It Ourselves Science - The Irregulars Project thread:

Found and posted by zooites:
name objID dr7objid ra dec
F07-4 1237650797293994155 587725076069089459 146.7729 0.9642
F07-12 1237648720153411631 588848898835349545 171.8011 -0.9947
NA10-31 1237661950251237398 588017704003043337 177.1277 12.7299
NA10-33 1237661951339200541 588017705091006505 210.4864 12.3805

in many topics long time ago  :P  ;)

A rather terse post; what's going on?

For example, what's "F07-4 1237650797293994155 587725076069089459 146.7729 0.9642"?

* (source)

Well, earlier the same day, in the same thread, Astronomer KWillett posted this:

Hi everyone,

Looks like there hasn't been activity here for a bit, but I wanted to point out an interesting paper that just appeared on astro-ph. It's from a group of astronomers in Japan (K. Terao et al.) who combed two much smaller surveys of the SDSS for what they call "genuine" irregular galaxies - those without bulges, disks, bars, or any obvious large-scale, symmetrical structure. They found only 33 in their whole sample; using the power of citizen science and Galaxy Zoo, though, I'm confident we could make a significant improvement.

The link to the paper is here:

How many of these are galaxies that users found in the original Galaxy Zoo or GZ2? And are there ideas for how we could extend/improve what they've done?

- cheers,
Kyle (science team)

c_cld was responding to that ... and several other 'oldbie' zooites also responded; two of the responses are "ask waveney about his clean 5K list  ;)  ;)" (c_cld), and "Well, that would be my suggestion too : ask waveney ! :-D" (ElisabethB).

Time for an eye-candy break; here's "F07-12 1237648720153411631 588848898835349545 171.8011 -0.9947":

* (source)

All very nice, I can hear you thinking, but what's that got to do with the "Publication = Discovery" in the OOTD title?  ???

If you're an oldbie, you probably already know, and the title of the thread in which Galaxy Zoo Science Team member Kyle Willett posted gives a clue.

The Irregular galaxy project is a zooite run project, blessed by Chris.  What is it about, how can you help?

There are thousands of irregular galaxies out there, some small and insignificant, others brights and dazzling.  We have gathered them here in the forum, but none of the professional astronomers behind the Zoo is currently looking at them.  This is a large group of galaxies, can we find anything about them?   The largest study of irregulars to date looked at 161 of them, we have thousands...

Star forming clumps
On its own
A friend?

[...] Data will be released so anybody and everybody can look at it and try their own analysis.  Some draft data (web page or as a CSV table) is available now, but it does not currently have enough clicks to generate good research on yet, but it does allow people to build up models.   Joining in the analysis or data presentation is another way you can help.  I have integrated the draft data with SDSS (under CasJObs) so advanced searches can look at both what we have found and the original SDSS data on the objects (e.g. colour and size info).

A special mention must be given to Lovethetropics, who is adding thousands of images to our data set.  (Others are also welcome to help find more).

Do this well, and we will have a proper scientific proper paper with Zooite names as authors 1,2,3...  Chris says he is happy to act as supervisor. [...]

That's an extract of the OP of the Do It Ourselves Science - The Irregulars Project thread; let me highlight one para:

Do this well, and we will have a proper scientific proper paper with Zooite names as authors 1,2,3...  Chris says he is happy to act as supervisor.

That post kicked off the project (though it had actually been underway for some time before then). Search ADS for "Proctor, R" (waveney's IRL name), and you'll find dozens of papers; refine your search so you select just waveney and you'll find just two papers2. Neither of which are about the Irregulars project, or even irregulars in general.  :'(

Did waveney et al. discover "genuine irregular galaxies", as defined by Terao+ 2013? If so, how many did they find ... 33?

I don't know; do you?

What other discoveries did Proctor+ make, concerning irregulars? And which of those discoveries are as important - scientifically speaking - as Hanny's Voorwerp or Green Peas?

I don't know; do you?

And the last piece of eye-candy, to close: "NA10-33 1237661951339200541 588017705091006505 210.4864 12.3805":
* (source)

1 It is possible, even likely, that some zooite posted it earlier; as I said, my search was far from exhaustive.

2 Darg D., et al., 2009, "Galaxy Zoo: the fraction of merging galaxies in the SDSS and their morphologies", MNRAS, 401, 1043. (available here: astro-ph/ADS): "R. Proctor" is an et al., with the affiliation "Waveney Consulting/Waveney Web Services"
Keel, William C. et al., 2012, "The Galaxy Zoo survey for giant AGN-ionized clouds: past and present black hole accretion events", MNRAS, 420, Issue 1, pp. 878-900 (ADS): "Proctor, Richard", "Waveney Consulting, Wimborne, Dorset"

* ETA: I learned from mlpeck's post, downthread, that the DR7 images are not displaying for at least some of you. I have removed them from this, the OP, replaced them with the corresponding DR10 ones, and pasted the original DR7 ones in a downthread post (here).

Over in The unbearable arbitrariness of serendipitous Galaxy Zoo discoveries? thread, zutopian wrote (in part):

Grant Miller is the Community Manager, who is apparently unreachable! That's strange, isn't it? I even didn't know before, that the Zooniverse has a Community Manager!

My turn next:

Announced on 11 December, 2013, in the Zooniverse blog: Rob and Grant are running out of ideas for the Advent Calendar: "It also serves as an introduction for me, the new Zooniverse community manager."

There is just one (published) response to that blog post, by me (December 13, 2013 at 4:48 pm):

Quote from: JeanTate
Welcome Grant!

Sounds like a really cool job you have. How much do you have to do with developing versions of various Zooniverse projects in languages other than English? Also, as I’m sure you know, it’s extremely difficult for zooites in China to access FB, Twitter, and even WP-based blogs (though many Zooniverse-related ones are OK because they do not have WP in their URLs), yet zooites in China as just as keen as those in the UK! What are your plans to enable zooites in China to go beyond mere classifying?

No reply.  :'(

And before you could say "Mr N. I. Aboc is unreachable, truly ...", Grant posted this:

Fear not! Reports of my unreachableness have been greatly exaggerated.

Pleased to virtually meet you all. I am Grant Miller, and as you seem to know already, I am the new Zooniverse Community Manager (for want of a much better title). If you want to reach me you can do so by emailing I am also @mrniaboc on Twitter and I manage the Zooniverse Facebook page, so if you wanted you could PM me there too.

Jean, I apologise for giving you the cold shoulder with respects to your blog response! The fact is I never saw it. Comments are disabled for Daily Zoo and I'm not sure how you even managed to leave one, but I can't even see it now! If you see something you would like to talk to me about on Daily Zoo, you're best to just email me from now on so I definitely see it. Though I can't promise I'll reply right away. The Zooniverse community is getting pretty big ;)

Anyway, to answer your question: It is mainly Rob and Chris Snyder with the help of Meg Schwamb who have been leading the translation effort, and they're making some amazing progress. However, you are right about there being problems in CHina with major western social media platforms. To combat this I have been looking into the possibility of creating a Zooniverse presence on the major Chinese platforms such as Weibo and Tencent.



The unbearable arbitrariness of serendipitous Galaxy Zoo discoveries? thread was in danger of going serious OT (off-topic), so rather than take it even further OT, I decided to start this thread here, with the express purpose of having a thread focused on discussions with Grant Miller, the Zooniverse Community Manager!  ;D

Welcome to the Galaxy Zoo forum, Grant!  ;D Whoops ... wait a minute ... you're a much older oldbie than me!  :-[  8)

I posted this suggestion in page 2 of the The unbearable arbitrariness of serendipitous Galaxy Zoo discoveries? thread. So it is surely easily overlooked.

Here it is, in its own thread. Maybe we can get some discussion going on it ...

I think part of the problem is the change of numbers  58............ to the dr8 1..........numbers. It is harder to find out what has gone before.

That's certainly true.  :(

I'm fairly confident, however, that a 'hack' (as I believe it's called) to create a database of the (RA, Dec) coordinates of the centers of all images posted, together with their sizes and an ID of the field and object in the center (and a link to where - which post - they appeared in), could be fairly easily done. In fact, if gumbosea or waveney were still around, I think either of them could create just such a thing (or go a long way towards it). With an appropriate front end, such a database would make the essential job of finding out what's gone before very straight-forward.

In fact, hasn't ttfnrob written about just such 'hackdays' or 'hackathons'? Maybe we could approach him, with a request that a session in the next one be devoted to such a hack?

Separately, I suggested something similar for Talk: "a 'cone search' tool: input an (RA, Dec) and a radius, and you'll get all the images, collections, posts, etc which fall within the circle (some variant of this is standard in many external, online astronomy databases, e.g. NED)."


Hanny's Voorwerp is arguably the most famous of the serendipitous Galaxy Zoo discoveries. While there have certainly been others, the pace of such discoveries has fallen off markedly. Yet we ordinary zooites have continued to post unusual objects, a handful of which were later shown - by professional astronomers - to be just as previously-unknown and scientifically interesting ... and for many of these we've asked, in effect, if anyone knew what they are (an example).

Starting with today's OOTD, I would like to introduce to readers of this column some of unusual objects ordinary zooites have asked about, here in the Galaxy Zoo forum or in Galaxy Zoo Talk. Many, likely nearly all, are well-understood by the small cadre of professional astronomers who study galaxies out to a redshift of ~0.4. But perhaps some are not. And if one of those astronomers, a zookeeper perhaps, on seeing one thinks "Hmm, there is indeed something strange about that ..." and upon digging a bit finds that it is indeed HV/GP/BMVC-like*, then maybe another ordinary zooite will be feted, and may become a co-author of a paper published in MNRAS.

The image which kicks off this OOTD was first posted, on June 28, 2011, by LynnSeguin, in the Newbies, Post your Interesting objects/queries here. (The Newbies Thread) (at least, I think she first posted it; an earlier posting anyone?); click the 'source' link next to it for the source.

Here is the object as imaged by DR8:

LynnSeguin gives its ID as "AHZ60005gr Reference: 8647474691427205226"; the very next post in that thread is a lengthy response by paulrogers. Among other things, he notes that this object - or part of it, or something - is identified as "Sy1 ()" in SIMBAD, but as "GALAXY STARBURST" by the automatic SDSS spectroscopic pipeline. While paulrogers certainly did some research into the nature of this unusual object, and turned up some unusual features, perhaps he didn't dig deep enough (as he himself said)? Even though this object is referenced in quite a few papers - mostly surveys of one kind or another - is there something quite remarkable that no one has so far spotted? Something that might make it as worthy of a paper as SDSS1133 was?

But do we need to wait for a zookeeper to stumble upon this thread, to have her interest piqued? If you, dear reader, think this is truly unusual, what research could you yourself do - and as paulrogers started to do - to show just how strange it is? What sorts of things do you think could be done, by us ordinary zooites, to research this further, even if you personally don't have the skills or access to tools to do that research?

My thanks to fellow OOTD author TonyWei for bringing this beautiful object to my attention.  :)

* Hanny's Voorwerp/Green Peas/Bruno's Mystery Violin Clef

Technical Support / Galaxy Zoo Talk down?
« on: February 08, 2014, 03:38:12 pm »
The classify site is working OK (so it seems), but Talk is down: I get the 'spinning spokes' symbol of 'forever loading' (I'm using Firefox).


This SDSS image appeared in the Wanted galaxies pair!One blue,red the other one. thread (here in the GZ forum), stardate November 20, 2008, 05:18:25 am, posted by sayonave08:

Other than the pair of IDs ("id=587731870169301121,id=587733081347063839"), sayonave08 wrote nothing.

A few minutes later, at 05:32:14 am, sayonave08 posted something a bit meatier, in the Quasi-Stellar radio sources. Find a Quasar? Post it here! thread:

QSO z=0.008,id=587733081347063838,My best friend,Galaxy Part of UGCA 239,id=587733081347063839

Later that same day (at 11:24:48 am), dthomas02 responded:

QSO z=0.008,id=587733081347063838,My best friend,Galaxy Part of UGCA 239,id=587733081347063839

Hi sayonave08. You might want to recheck this one. It doesn't much look like one and the z is 0.0085 with a high confidence - the nearest recorded to date is 3C273 which is at z=0.158

Fast forward a bit over five years, to January 28 2014 11:52 AM, and SCIENTIST KWillett wrote, in the A new transient discovered in SDSS data thread in GZ Talk:

Quote from: KWillett
M. Koss and collaborators (including GZ science team member Kevin Schawinski) have just submitted a new paper on a transient object discovered in a nearby dwarf galaxy. Originally thought to be either a supernova or a QSO, they suggest that it is a luminous blue variable (LBV) star that has been erupting for decades, since at least 1950, and then FOLLOWED by a supernova in 2001.

A very interesting object, and one that was discussed by GZ volunteers back on the forum in 2011.

Later that same day (04:47:33 pm), he wrote a post in the Wednesday, 2nd November, 2011: A Pretty Galaxy Group OOTD, quoting a long post by c_cld from earlier in that thread, dated November 16, 2011, 06:25:42 pm, and added: "A new paper on this precise object has been submitted to MNRAS. They suggest that it's in fact a luminous blue variable (LBV) star erupting over decades, followed by a supernova explosion in 2001."

The paper by M. Koss and collaborators (including GZ science team member Kevin Schawinski) is titled "SDSS1133: An Unusually Persistent Transient in a Nearby Dwarf Galaxy"; here's the abstract:

Quote from: Koss+ 2014
We have discovered an unusual source offset by 0.8 kpc from a nearby dwarf galaxy while performing a survey to detect recoiling black holes. The object, SDSS J113323.97+550415.8, exhibits broad emission lines and strong variability. While originally classified as a supernova (SN) because of its nondetection in 2005, we detect it in recent and past observations over 63 yr. Using high-resolution adaptive optics observations, we constrain the source emission region to be <12 pc and find a disturbed host morphology indicative of recent merger activity. Observations taken over more than a decade show narrow [O III], constant ultraviolet emission, broad Balmer lines, a constant putative black hole mass over a decade of observations despite changes in the continuum, and optical emission-line diagnostics consistent with an active galactic nucleus (AGN). However, the optical spectra show blueshifted absorption, and eventually narrow Fe II and [Ca II] emission, each of which is rarely found in AGN spectra. While this peculiar source displays many of the observational properties expected of a potential black hole recoil candidate, most of the properties could also be explained by a luminous blue variable star (LBV) erupting for decades since 1950, followed by a Type IIn SN in 2001. Interpreted as an LBV followed by a SN analogous to SN 2009ip, the multi-decade LBV eruptions would be the longest ever observed, and the broad Halpha emission would be the most luminous ever observed at late times (>10 yr), larger than that of unusually luminous supernovae such as SN 1988Z, suggesting one of the most extreme episodes of pre-SN mass loss ever discovered.

Koss et al. recount the history of "SDSS J113323.97+550415.8 (hereafter SDSS1133)" in their introduction:

SDSS1133 was mentioned as a possible case of a quasar having a noncosmological redshift because of its broad Balmer lines but very low luminosity (Lopez-Corredoira & Gutierrez 2005). In a study of narrow-line Seyfert 1 galaxies, Zhou et al. (2006) classified SDSS1133 as a SN because of its nondetection in data obtained in January 2005 with the 2.16 m telescope at the Beijing Observatory. Finally, SDSS1133 was listed as a possible “Voorwerp” candidate for a giant ionized cloud (Keel et al. 2012).

Hmm, "Voorwerp" candidate, Keel, ... sounds like it was mentioned - possibly even discussed - here in the GZ forum too. Time to dig a bit ...

In the Wanted! Galaxy pairs which overlap but are not merging thread, on February 11, 2010, 04:47:37 pm, c_cld wrote:

587733081347063839 z=0.0078 , SDSS J113323.47+550420.6  SpecObjID = 285923593806675968
in front of
QSO 587733081347063838 z=0.0085 , SDSS J113323.97+550415.8 SpecObjID = 285642003167838208


Not exactly voorwerpje, so how did the "possible “Voorwerp” candidate" come about?

Well, Table 1 of Keel et al. 20121 - "Candidate AGN with extended emission-line clouds" - includes SDSS J113323.97+550415.8 (DR7 ObjId 587733081347063838), with a "Sy 1" nucleus (Seyfert type 1), "Mkn 177 compn" note (companion to Markarian 177?), "S" as search type ("serendipitous") and "stellar190" as posted by. And here's stellar190's post (dated August 31, 2009, 01:39:19 pm), the OP of the Whats going on here? thread:

I'm confused with this one, i thought at first a star forming region or a star, but the z for the galaxy and the blob are the same ( 0.008 ) and the spectra doesnt look right for a star forming region ??? Its looks to be active?

Posted before by sayonave08 in the QSO thread

And so it goes ... the bright blue star-like object - named SDSS1133 by Koss et al. - and/or the dwarf galaxy Mkn 177/UGCA 239 was posted here in the GZ forum many, many times. By quite a few different zooties. Some of whom were not aware of who had posted it earlier, or why. Etc, etc, etc.

It certainly is a very unusual object2, at least as unusual as Hanny's Voorwerp, Bruno's Mystery Violin Clef, and mitch's Mystery Star.

SDSS1133, the giant fish that got away Galaxy Zoo discovery that wasn't.  ;)   :P :(

1 "The Galaxy Zoo survey for giant AGN-ionized clouds: past and present black hole accretion events" is the title, and the authors are William C. Keel, S. Drew Chojnowski, Vardha N. Bennert, Kevin Schawinski, Chris J. Lintott, Stuart Lynn, Anna Pancoast, Chelsea Harris, A.M. Nierenberg, Alessandro Sonnenfeld, & Richard Proctor. You can get a copy of this from the Zooniverse Published Papers page, or by clicking this link

2 Koss+ write "A survey of all [...] found only two objects offset from the host-galaxy nucleus: SDSS1133 along with a very close dual AGN Mrk 739 (Koss et al. 2011)." I wonder whether the "very close dual AGN Mrk 739" has been posted here before, by zooites who noted it as unusual?

On January 28 2014 11:52 AM, SCIENTIST KWillett wrote, in the A new transient discovered in SDSS data thread in GZ Talk:

Quote from: KWillett
M. Koss and collaborators (including GZ science team member Kevin Schawinski) have just submitted a new paper on a transient object discovered in a nearby dwarf galaxy. Originally thought to be either a supernova or a QSO, they suggest that it is a luminous blue variable (LBV) star that has been erupting for decades, since at least 1950, and then FOLLOWED by a supernova in 2001.

A very interesting object, and one that was discussed by GZ volunteers back on the forum in 2011.

Everyone reading this post must surely be aware of the impact Hanny's discovery of what became known as Hanny's Voorwerp had, in terms of understanding the duty cycle of AGNs, the potential scientific value of citizen science projects such as Galaxy Zoo (re serendipitous discoveries), and more; likewise of the (collective, serendipitous) discovery of, and investigation into, Green Peas. For example, these figure prominently in Michael Nielsen's book "Reinventing Discovery" (discussed in this GZ forum thread), and more generally are frequently and widely promoted (not an inaccurate word, right?) as the sorts of 'serious science' discoveries zooites - as citizen scientists - can make, and so contribute to astronomy in ways that go beyond mere classification clicking.

It's always puzzled me why the Galaxy Zoo serendipity seemed to come to a screeching halt not long after Green Peas (of course, serendipity has surely continued in other Zooniverse projects - or at least I hope it has!). And this recent discovery - of an apparently completely new kind of variable star, one which was flagged by at least one zooite as being unusual, several years' ago - led me to a mild Ah ha!

You see, GZ zooites have, in fact, continued to make serendipitous discoveries, and by now have possibly noted dozens, even hundreds  :o  8) But it takes a professional astronomer to read those posts, containing such discoveries, to recognize that there's something odd/really new/cool/etc, and then to take the time to look into them a bit more. Many, perhaps most, "What’s the [something odd]? – Anyone?" (source) are not anything like Hanny's Voorwerps or Green Peas. But, as we now know, at least one certainly is!

In the early days of GZ, professional astronomers seemed to be very keen to read each and every post (at least those which contained images of, or reference to, something some zooite had classified), and in every new astronomy-related Zooniverse project (well, extra-galactic ones at least), in the early days, the SCIENTISTs* of such projects seem just as keen. They also were - and still are, when new projects are still new - enthusiastic about answering zooites' astronomy-related questions, explaining the astrophysics (and more) underlying the phenomena, the data, etc. Not just Science Team members either; who can forget EigenState's great posts!  :D

How things have changed!  :'(

My subjective impression is that none of the original zookeepers post here any more, nor in any (extra-galactic astronomy) Zooniverse project's Talk. Yes, NGC3314 posts here often; yes SpaceWarps seems to have plenty of Talk-active SCIENTISTs; and so on. So the opportunity for new GZ serendipitous discoveries is greatly reduced, if only because no professional astronomer seems to be even reading what zooites post.

There is a sunny side however, and that's what I'd like - hope - this thread will discuss.

You see, instead of professional astronomers answering newbie (and oldbie!) zooites' questions about what they find in images they've just classified, there are now a cadre of (mostly) oldbie zooites. Over in GZ Talk, for example, MODERATOR Els does an awe-inspiring job of concisely and accurately answering almost all such newbie zooite questions!  8)  ;D So it's these, ordinary citizen scientists, who first read the "What’s the [something odd]? – Anyone?" posts. Maybe, with some directed assistance from a handful of professional astronomers, with some training, ... these super-users (as I've seen these zooites being referred to sometimes) could learn to recognize, from among the thousands of ordinary objects, the handful which might be genuinely new to astronomy (in a broad sense)? And maybe one or two professional astronomers could dedicate/commit some of their precious time to checking these few 'super-user recommended' objects out?

There's more.

A looooong time ago zkKevin announced the soft launch of Letters, intended as a place where ordinary zooites could publish their own, independent research. Search as you might, you'll find Letters very hard to find. And writing a Letter is almost guaranteed to give you ulcers. Yet wouldn't it be a great vehicle for getting serendipitous discoveries noticed? So perhaps a modest amount of Zooniverse development effort could be devoted to finally getting Letters to work as intended?

To close: as I understand it, many professional astronomers these days have some sort of 'outreach' goal/target to meet, as part of their jobs. Maybe we ordinary zooites could encourage at least one such astronomer to make active development of a 'serendipitous discovery framework' their outreach target?

* since there are no more SMF forums, just Talks, and that's how official Science Team members are labeled

CANDELS Visual Classifications: Scheme, Data Release, and First Results - makes GZ CANDELS irrelevant? is the title of a thread in GZ Talk, which I posted on January 24 2014 7:37 PM.

Here's a copy of its contents:

"CANDELS Visual Classifications: Scheme, Data Release, and First Results" is the title of arXiv:1401.2455 (link is to the abstract), an astro-ph preprint posted on 10 Jan, 2014. The lead author is Jeyhan S. Kartaltepe.

Here's the abstract:

Quote from: Kartaltepe+
We have undertaken an ambitious program to visually classify all galaxies in the five CANDELS fields down to H&lt;24.5 involving the dedicated efforts of 65 individual classifiers. Once completed, we expect to have detailed morphological classifications for over 50,000 galaxies up to z&lt;4 over all the fields. Here, we present our detailed visual classification scheme, which was designed to cover a wide range of CANDELS science goals. This scheme includes the basic Hubble sequence types, but also includes a detailed look at mergers and interactions, the clumpiness of galaxies, k-corrections, and a variety of other structural properties. In this paper, we focus on the first field to be completed -- GOODS-S. The wide area coverage spanning the full field includes 7634 galaxies that have been classified by at least three different people. In the deep area of the field, 2534 galaxies have been classified by at least five different people at three different depths. With this paper, we release to the public all of the visual classifications in GOODS-S along with the GUI that we developed to classify galaxies. We find that the level of agreement among classifiers is good and depends on both the galaxy magnitude and the galaxy type, with disks showing the highest level of agreement and irregulars the lowest. A comparison of our classifications with the Sersic index and rest-frame colors shows a clear separation between disk and spheroid populations. Finally, we explore morphological k-corrections between the V-band and H-band observations and find that a small fraction (84 galaxies in total) are classified as being very different between these two bands. These galaxies typically have very clumpy and extended morphology or are very faint in the V-band.

At first read, it seems that the classifications being done here, in this part of Galaxy Zoo, will be irrelevant (or at least relatively marginal), unless GZ:CANDELS is published in the next month or so.

What do you think?

So far, not a single response.

Maybe regular readers of this section of the GZ forum will be more interested?

Star space / Dust in galaxy halos?
« on: January 25, 2014, 02:58:48 pm »
The title of a recent astro-ph, "Detection of Ultraviolet Halos around Highly Inclined Galaxies", doesn't seem to have anything to do with dust. However, when you read the abstract ..

Quote from: Hodges-Kluck&Bregman
We report the discovery of diffuse ultraviolet light around late-type galaxies out to 5-20 kpc from the midplane using Swift and GALEX images. The emission is consistent with the stellar outskirts in the early-type galaxies but not in the late-type galaxies, where the emission is quite blue and consistent with a reflection nebula powered by light escaping from the galaxy and scattering off dust in the halo. Fitting a simple reflection nebula model to the halo SEDs points to SMC-type dust (lacking a UV bump), and the halo colors and luminosities are consistent with this scenario. Our results agree with expectations from halo dust discovered (at larger radii) in extinction by Menard et al. (2010) to within a few kpc of the disk and imply a comparable amount of hot and cold gas in galaxy halos (a few x10^8 Msun within 20 kpc) if the dust resides primarily in Mg II absorbers.

I guess there's so little of this dust that it doesn't show up in the various 'overlapping pairs' studies NGC3314 et al. have conducted ...

The Menard+ 2010 paper referred to reports "dust reddening effects due to galactic halos and large-scale structure", and "The presence of dust is detected from 20 kpc to several Mpc, [...] The amount of dust in galactic halos is found to be comparable to that in disks.??? :o 8) I thought halos were essentially dust-free, and that dust couldn't survive there for very long anyway ... so how does the dust get there? and how can it survive?

The full sentence is: "So this data should represent the true shape of the galaxies as best as humans can describe it." And it comes from the Kaggle forum discussing Galaxy Zoo - The Galaxy Challenge; specifically, this post in the "Root Mean Squared Error as the evaluation metric" thread.

I've started this thread with the aim of having a discussion of this statement; specifically, to explore the extent to which humans could describe the true shape of a large subset of the ~300k GZ2 galaxies better.

In context, there's an obvious - but unstated - caveat (or series of caveats), which goes something like thisa:
  • as imaged by SDSS
  • with raw data processed by the SDSS photometric pipeline
  • and converted to GZ2 RGB JPG images
  • using data from just three, of five, filters
  • within a morphological classification scheme of GZ2

In terms of resolution and dynamic range (and more), there are obviously many telescopes+cameras+processing pipelines which could produce far better images of a large subset of the GZ2 galaxies than the SDSS, and just as consistently too. But let's accept that the input data is that from SDSS; that deals with points 1 and 2.

For point 3 (converting SDSS data - FITS files - to GZ2 RGB JPG images): if I recall correctly, GZ2 used DR8 images (except for Stripe 82). Comparison of archived DR8 images with the current DR10 ones shows that it is certainly possible to produce crisper visual images (JPGs), so some improvement is certainly possible. Willett+ 2013 (W13) presents details of how the different Stripe 82 sets of images were created and how morphological classifications differ among these. With the benefit of these results, would it be possible to produce "better" Stripe 82 images (better in the sense of being crisper and displaying more of the features)? I think so.

I'll leave my initial comments about points 4 and 5 to later posts.

a There's also the stated caveat, that the statement applies to the galaxies used in the Kaggle Galaxy Zoo Challenge, only.

The context: in "Galaxy Zoo: morphologies derived from visual inspection of galaxies from the Sloan Digital Sky Survey, Lintott+ 2008" (Available here), Section 4 ("COMPARISON WITH OTHER SAMPLES") begins:

Quote from: Lintott+ 2008
In order to assess the reliability of the Galaxy Zoo classifications, we compare our sample with that produced by previous projects. The MOSES sample (Schawinski et al. 2007) described in Section 1 consists of 15 729 galaxies classified as elliptical selected from an initial set of 48 023 galaxies. Of the 48 023 the clean sample includes classifications for 19 649 systems. The results for the weighted clean sample are given in

"Schawinski et al. 2007" is, in the References, "Schawinski K., Thomas D., Sarzi M., Maraston C., Kaviraj S., Joo S.-J., Yi S. K., Silk J., 2007, MNRAS, 382, 1415". MOSES, by the way, stands for "MOrphologically Selected Ellipticals in SDSS"

Checking that paper, I find (bold added):

Quote from: Schawinski et al. 2007
For the MOSES sample we carried out manual inspection of multi-colour images from SDSS by eye for all 48,023 galaxies, in order to avoid any potential bias introduced by selecting by colours or spectral features. We define as early-type galaxies all objects earlier than and including S0 galaxies and reject galaxies from our sample if they show distinct spiral arms or a disk. We include in this selection objects with clear tidal features or other signs of morphological disturbance. In the paper presenting the MOSES catalogue (Schawinski et al., in preparation) we present a number of example images from SDSS to illustrate the effectiveness of our visual inspection. Out of the 48,023 galaxies in our volume limited sample, we identify 15,729 early-type galaxies.

Using ADS I find:

a) no "Schawinski et al., in preparation" paper among those which Schawinski et al. 2007 references
b) nothing by "Schawinski, K." published since 2006 which resembles a paper "presenting the MOSES catalogue"
c) no paper published since 2006, with any author, which seems to present a MOSES catalog

Can any reader help, please?

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