Galaxy Zoo Talk

# The Green Pea Galaxies.

• by Rick_N.

I was missing somewhere to post information on the Green Pea Galaxies, so I started this discussion. The links are to the two GZ Forum threads that this discussion continues:

Give peas a chance!
http://www.galaxyzooforum.org/index.php?topic=3638.0

Discussion: Green Peas: A Class of Compact Extremely Star-Forming Galaxies
http://www.galaxyzooforum.org/index.php?topic=275810.0

https://en.wikipedia.org/wiki/Pea_galaxy

Posted

• by Rick_N.

Green Pea Galaxies & The Early Universe.

Recently, a paper was published in ArXiv by Anne Jaskot and Sally Oey from the University of Michigan.
Entitled: "Linking Ly-alpha and Low-Ionization Transitions at Low Optical Depth", it delivered the first hints
of just how important some Green Pea galaxies will be in the studies of the early universe. Below is an image
of GP-J1219, which combines a newly-available Near Ultraviolet picture (on the left) from the Cosmic Origins
Spectrograph on board the Hubble Space Telescope with a familiar SDSS picture on the right.

The scale bar in each picture shows 1 arcsec, which corresponds to ~10,750 light years at the distance of 2.69 billion light years for this particular Pea.

We are some of the first to see this HST COS NUV image of GP J1219!

SDSS J121903.98+152608.5
http://skyserver.sdss3.org/dr9/en/tools/explore/obj.asp?id=1237661070336852109 (DR9)

Credit: Anne Jaskot, Sally Oey, HST COS, SDSS and Rick Nowell.

Not only that, the author Anne Jaskot kindly emailed me a few words about their latest studies:

"Our latest results not only support the idea that some GPs are LyC [Lyman Continuum] leakers, but they show
that the GPs are immensely important for our understanding of high-redshift Ly-alpha Emitters (LAEs). Ly-alpha
emitting galaxies are one of the main galaxy populations we detect at high redshift (z>2), but because of their
great distance, it's difficult to study many of their physical properties.

With the Ultraviolet spectra of the GPs, we've already solved one longstanding puzzle regarding LAE spectra: why certain low-ionization emission lines appear to correlate with strong Ly-alpha emission. We show that the neutral gas geometry can explain the observed emission. Galaxies with strong Ly-alpha emission, low-ionization emission lines, and no low-ionization absorption lines may be LyC leakers, with most of their neutral gas located to the side of the starburst, instead of in front of it. What's striking is how compact and featureless this galaxy appears, even with HST. The compact starburst region completely dominates the light of the galaxy.

We have imaging observations in both continuum and emission lines scheduled for the four GPs discussed in our recent Letter. Some of the data are in hand, and we're waiting on the rest. Stay tuned for a future analysis of the images." (July 2014)

Determining the population of objects that reionized the Universe (the epoch of reionization) remains an outstanding and pressing question in cosmology. The process of re-ionization is theorised to have taken place between 150 million and one billion years after the Big Bang. Finding suitable candidates in the local universe has proved difficult, as astronomers are looking for galaxies that emit Lyman Continuum photons (LyC). Lyman continuum photons (LyC) are a kind of photon emitted from stars. Hydrogen is ionized by the absorption of LyC photons, so finding galaxies that do this is very important to the study of the early
universe. This seems straightforward, but so far only two have been found in the local Universe (Haro 11 and Tol 1247-232). With the recent finds from Hubble, a few GPs are about to be added to those. That is a major achievement!

'Linking Ly-alpha and Low-Ionization Transitions at Low Optical Depth'
A. E. Jaskot, M. S. Oey http://arxiv.org/abs/1406.4413

Posted

• by Budgieye moderator

Thank you RickN for bringing back this thread. I have remembered to click "Follow" so I can find it again.

It doesn't seem likely that we will find any more green peas until we get new areas of the sky to explore, since the current SDSS footprint has been searched thoroughly. So this thread will be bringing us up to date on what these hot little galaxies actually are. Is there any hint to their formation?

EDIT: information about peas is indexed in Talk at
3.8 Green peas, compact starburst, Blue compact starburst , OIII objects http://talk.galaxyzoo.org/#/boards/BGZ0000001/discussions/DGZ0000wrb?page=3&comment_id=53d8b93a0d43f77bb6000f98

Posted

• by Rick_N.

Yes, it will be good to have somewhere to post info and suchlike, even though it might not get much attention.

As for their formation, I think that there is the theory that the starbursts are caused when new gas becomes available through a merger with an equally small galaxy. However, GPs exist in an environment which is less dense (two thirds) than normal space, so the chances of one dwarf galaxy bumping into another seem unlikely. They don't look like mergers though- the HST COS picture above is pretty featureless.

Another theory suggests that a gamma-ray burst acts as a 'fuse', setting off starbursts within gas that is already there- though I haven't seen anything more on this theory since 2012.

There's never been any literature on the effects of Dark matter or Dark energy, so I surmise these aren't likely sources.

I guess that no-one has come up with a definitive solution. If we extend our thoughts back to the epoch of reionisation, then the first galaxies would have been small I gather.

Posted

• It doesn't seem likely that we will find any more green peas until we get new areas of the sky to explore, since the current SDSS footprint has been searched thoroughly.

I'm sure this is right for GPs. However, below a certain z, the [OIII] and H-beta lines appear in the g filter (mapped to B ), rather than r (mapped to G, hence green peas); above a much higher z, they appear in the i filter (mapped to R). How thoroughly has SDSS been searched for blue peas*? Highly unlikely to be any red peas* - by that much higher z, the compact galaxies would be close to invisible in SDSS (not luminous enough) - but you never know, right?

'False positives' would include many QSOs which blue and possibly non-stellar; ditto magenta/red (FeLoBALs in particular).

*they're actually likely to be not quite a pure color; for the low-z ones, the [NII] and H-alpha (and to some extent [SII]) emission lines will make them look more, what, blue-green? magenta? for the high-z ones, strong [OII] emission will make them look various shades of magenta/pink.

Posted

• by ElisabethB moderator

If I remember correctly, once that we established that peas' spectra were very flat with an OIII spike, there were quite a number of other (than green) colored peas found and posted ! 😄

Posted

• by JeanTate

A quick look at the papers which cite Cardamone+ (2009) turns up Izotov+ (2011): "We present a large sample of 803 star-forming luminous compact galaxies (LCGs) in the redshift range z = 0.02-0.63, selected from Data Release 7 ... In contrast to green pea galaxies, our LCGs are selected on the basis of both their spectroscopic and photometric properties, resulting in a ~10 times larger sample, with galaxies spanning a redshift range ~2 times larger."

I wonder if any of the Green Peas zooites discovered are not among the 803? Other than those which may be in DR8, DR9, or DR10, but not DR7. Perhaps a quick analysis - magnitude vs redshift, say - might lead to an estimate of the size of the selection effect (there would surely be very few GPs with DR7 spectra, z > ~0.5, for example), and an estimate of the number of as yet unidentified GPs in DR10, particularly those without SDSS spectra.

Posted

• by Rick_N.

Contemplating how the GPs might have evolved is a fundamental question: what produces the least massive and most actively star-forming galaxies in the local universe?

Spectroscopy of superluminous supernova host galaxies. A preference of hydrogen-poor events for extreme emission
line galaxies. G. Leloudas et al. http://arxiv.org/pdf/1409.8331v1.pdf

The above paper, recently submitted, seems to suggest that in hydrogen-poor dwarf galaxies, superluminous supernova occur.
These SLSN only occur with the newest and most massive stars, as Gamma ray bursts need a more hydrogen-rich environment.
One of the authors of the paper is the scientist who suggested that GRBs might occur in GPs.

So, a possible scenario for the GPs to occur is that two very small galaxies merged in less dense environments. As new gases became available through the mixing of the dwarf galaxies, massive stars formed in metal-poor and possibly hydrogen-poor environments. After only a few million years these stars exploded, becoming SLSN. This would then tend to disperse the gases (SN Feedback), so the creation of new stars slows. GPs are thus likely to be merged dwarf galaxies hosting extreme starburst at a very young stage in the new galaxy's life. So we're observing dwarf galaxies just at the stage of the first generation of stars forming- a temporary occurence and why there are only a thousand or so in the local universe.

The above paper also mentions a paper in preparation by C. Thone giving a time limit to this event. A paper a few years back put a top limit of 5 million years, though this seems even too long. A few million years.

Perhaps quite like voorwerps, events occuring in a cosmic blink of an eye, that only analysis of large datasets could spot.

Posted

• by zutopian

I would like to suggest, that a moderator moves this topic to the board Science Powered by Citizens !

Posted

• Any particular reason?

Posted

• by c_cld

HST Approved Programs Cycle 22 from October 1, 2014 to September 30, 2015

Proposal Category: GO

Cosmology

ID: 13744

Green Peas and diagnostics for Lyman continuum leaking in star-forming dwarf galaxies

Trinh Thuan

The University of Virginia

One of the key questions in observational cosmology is the identification of the sources responsible for cosmic reionization. The general consensus is that a population of faint low-mass galaxies must be responsible for the bulk of the ionizing photons. However, attempts at identifying individual galaxies showing Lyman continuum (LyC) leakage have so far not been successful, both at high and low redshifts. We propose here to observe directly the LyC of five socalled "Green Pea" (GP) galaxies. GPs share many of the properties of the Lyman Break galaxies at high z (compactness, low mass, low metallicity, high specific star formation rate, gas-rich and clumpy morphology) and may constitute local examples of the long sought-after LyC leaking galaxies. The five GPs have been identified by searching the Sloan Data Release 10 spectral data base of 2 million spectra for non-AGN emission-line objects that meet the following criteria: high [OIII]5007/[OII]3727 ratios, large GALEX FUV fluxes, and redshifted enough (z~0.3) so that the LyC is shifted into the sensitive spectral range of COS. Our unique GP sample will allow us to combine for the first time four fundamental tests for LyC leaking in galaxies and validate their usefulness as LyC leaking indicators : 1) direct measurements of the LyC; 2) high [OIII]/[OII] ratios; 3) characteristics of the Lyman alpha line profile; and 4) residual intensities in the low-ionization ISM absorption UV lines.

😃

Posted

• Cool! 😃

I wonder whether AGNs with extraordinarily strong [OIII] emission have been researched, as possible candidates?

Here's a z_sp 0.507 one, SDSS J142636.36+274819.4, which super-zooite WizardHowl found recently (I think the almost-GP-looking neighbor is a chance alignment):

The spectrum looks similar to that of a GP, albeit at considerably higher redshift:

However, it's obviously a far more massive galaxy, and the host of radio emission whose morphology is 'triple' (i.e. core+double lobes):

Posted

• I recall that AGN's aren't thought to be responsible for re-ionisation, for the simple reason that there weren't enough of them at the early stages of the universe. I'll try and dig out the paper I'm thinking of, but that's the gist of it. The 80 GPs examined in Cardamone 2009 do not have AGNs: they are pure starbursts, which makes them a good candidate for early universe studies.

Posted

• I too vaguely recall reading papers with findings like that. However, what I'm wondering is whether there is a sub-class of AGN with similar (to GPs) LyC leakage.

Quite aside from whether there is such a sub-class of AGNs, SDSS J142636.36+274819.4 seems to have extraordinarily strong [OIII] emission; among AGNs, I wonder how common this is?

Posted

• Thanks Claude for posting the HST link.

Posted

• by Rick_N.

Continuing on the theme about Super-Luminous Supernovae (of which 3 are known) and that Pea galaxies might well host them, a paper by Chen et al. titled: "The host galaxy and late-time evolution of the Super-Luminous Supernova PTF12dam", uses and compares data from Cardamone 2009, Amorin 2012 and Izotov 2011- all GP papers (page 16).
http://arxiv.org/pdf/1409.7728v1.pdf

Quoting from that: "the host of PTF12dam shows very similar properties to Green Pea galaxies"

A Science Daily article from October 2013 explains more about SLSn:

New light on star death: Super-luminous supernovae may be powered by magnetars
http://www.sciencedaily.com/releases/2013/10/131016132155.htm

Posted

• by Rick_N.

A paper that also examines SLSN PTF12dam by the scientist who presented an abstract to the IAU in 2012 about GRBs and GPs.

"A young stellar environment for the superluminous supernova PTF12dam"

C. C. Thöne, A. de Ugarte Postigo, R. García-Benito, G. Leloudas, S. Schulze, R. Amorín
http://arxiv.org/abs/1411.1104

Data about GPs is used, which is taken from Amorin 2010 & 2012a and Jaskot & Oey 2013 (both specific GP papers). Quoting:
"The host does not show any enhancement in the N/O ratio as some green pea galaxies (GPs, a subsample of EELGs)
(Amorın et al. 2010), but has abundances of Ne, He, Ar and Fe very similar to those galaxies (Amorın et al. 2012a). The
ionization level is high and comparable to the most extreme EELGs (Jaskot & Oey 2013), indicating a hard radiation field
and young stellar population (e.g. Martın-Manjon et al. 2010).

Posted

• by Rick_N.

A paper that investigates the age limits of Luminous Compact Galaxies is available here:

Hα and UV luminosities and star formation rates in a large sample of luminous compact galaxies.

S. L. Parnovsky, I. Y. Izotova, Y. I. Izotov (2013). http://arxiv.org/abs/1209.3498

Luminous Compacts are Yuri Izotov's 803 galaxies that used the initial criteria of the GPs and extended them to the redshift range z = 0.02-0.63. If one looks at the GZ Forum thread, these might include the GPs that were different in colour e.g. purple (which became known as 'grapes') but shared the same spectral characteristics.

Parnovsky, Izotova and Izotov find that the rates of star formation of these Luminous Compacts starts to decrease after 3.2 million years or so. I venture that the most luminous GPs are in that initial phase. Interestingly, the largest, newest stars might only last for 2 million years or so before exploding massively, which would then drive material away, diffusing the matter that had allowed vigorous starbursts in the first place. As seen from the studies about superluminous supernovae, GPs would provide an environment for the most powerful stellar explosions.

So GPs could well be mini-mergers of dwarf galaxies in a not-dense environment that have yet to undergo a large number of massive
stellar explosions. So we might well be seeing these GPs at a specific point in their evolution, say before 3 or 4 million years old.

Green Pea Galaxies and cohorts: Luminous Compact Emission-Line Galaxies in the Sloan Digital Sky Survey

Y.I.Izotov, N.G.Guseva, T.X.Thuan (2011) http://arxiv.org/abs/1012.5639v1

A sample of GPs of different colours can be found here onwards for a few replies. Thanks to Starry Night for that:

Posted

• by c_cld

Yesterday 2014-12-14 13:23 and 16:49 HST observation SDSS-J121903.98+152608.5 12 19 03.983 +15 26 08.52 for

Original observing program:

13293 - Jaskot, Anne - Smith College

Green Pea Galaxies: Extreme, Optically-Thin Starbursts?
ISM IN EXTERNAL GALAXIES - Cycle 21 - Status: scheduling

1237661070336852109

Posted

• by Rick_N.

The five GPs observed on the HST COS (Cycle 22) by Thuan et al. are:

Green Peas and diagnostics for Lyman continuum leaking in star-forming dwarf galaxies (program 13744).

Trinh Thuan, Natalia G. Guseva, Yuri I. Izotov, Ivana Orlitova, Daniel Schaerer, Anne Verhamme

Hubble Space Telescope Approved Programs Cycle 22 from October 1, 2014 to September 30, 2015.

http://archive.stsci.edu/proposal_search.php?id=13744&mission=hst

http://www.stsci.edu/cgi-bin/get-proposal-info?observatory=HST&id=13744

Posted

• by JeanTate

SDSS J091536.19+064253.1 (DR12 link) is classified by SDSS as a STAR, yet it is this host of a bright, compact radio source. NED gives its photometric redshift as 0.355.

It looks - to me - rather like a Green Pea:

What do you think?

Posted

• It has 8 literature references in NED, which is rather a lot for a star. Seven of them are radio catalogs and the 8th is a catalog of QSO candidates.

I've noticed that post-starburst galaxies with an AGN often look green in that general redshift range (0.2 < z < 0.35) and also often appear to be quite compact. I wonder if there's a connection between green peas and post-starbursts.

Posted

• by Rick_N.

In the original Cardamone 2009 paper, GPs that were AGN's were found, as well as some 'transition objects''.

The graph above classifies 103 narrow-line GPs (all with SNR ≥ 3 in the emission lines) as 10 active galactic nuclei (blue diamonds), 13 transition objects (green crosses) and 80 starbursts (red stars).

http://arxiv.org/abs/0907.4155

Posted

• by Rick_N.

This post is surplus to requirement now that there's a new Wikipedia article on Tol 1247. This has a lovely pic though.
https://en.wikipedia.org/wiki/Tololo-1247-232

As followers of the GPs and their importance in the study of the 'Epoch of re-ionisation' might know, only two galaxies have so far been discovered that emit Lyman Continuum photons (LyC) - Haro 11 and Tol 1247-232. Haro 11 is a well-studied galaxy and a link about it is found at the bottom of this post. GPs are about to add a few more to these two.

Tol 1247-232 is a less well-known object that has not received as much attention. It's name comes from a survey of 'Emission-line galaxies and quasars' that took place in 1976 using the 61cm Curtis Schmidt telescope at The Cerro Tololo Inter-American Observatory (CTIO) in Chile. http://www.ctio.noao.edu/noao (picture below)

Posted

• by Budgieye moderator

Two peas in two pods. Two similar galaxies with a "pea" in SDSS at z=0.003 and in Hubble at z=1.294

Spectral chart of SDSS object, showing emission peaks of hot oxygen from many large stars that that rapidly formed and exploded. http://skyserver.sdss.org/dr8/en/get/specById.asp?id=2258666322118338560

The Hubble pea is about 200X further away than the SDSS pea

__249,000,000,000,000,000,000 miles away SDSS pea

52,800,000,000,000,000,000,000 miles away Hubble pea

SDSS pea
Lookback time
http://www.wolframalpha.com/input/?i=redshift+z%3D0.003&a=FSelect_**LookbackTimeFromRedshift--
distance 41.5 million light-years
41,500,000 light-years x 6,000,000,000,000 (6 trillion miles in a light year)
249,000,000,000,000,000,000 miles away

Hubble pea
http://www.wolframalpha.com/input/?i=redshift+z%3D1.294&a=FSelect_**LookbackTimeFromRedshift--
distance 8.8 billion light-years
8,800,000,000 light-years x 6,000,000,000,000
52,800,000,000,000,000,000,000

copied fromhttp://talk.galaxyzoo.org/#/boards/BGZ0000005/discussions/DGZ0001d9e

Posted

• by Budgieye moderator

z=3.166 pea with OIII lines

http://iopscience.iop.org/1538-3881/138/4/1022/article

PEARS 083553:[SMP2008] KNOT 01 03h32m42.8s -27d47m03s PofG >30000 3.166000 ... 0.003 2

http://talk.galaxyzoo.org/?_ga=1.221223262.711441289.1371287491#/subjects/AGZ00086ui

[EDIT: I'm not very convinced about this one, could the pea be the little red object just below the round object?]]

Posted

• by Budgieye moderator

Oiii lines, and Hα lines

Posted

• You may want to have a look through here Budgieye my collection called 'green'. If you get the time that is. may be something of interest. its mostly from the last hubble images we had.

http://talk.galaxyzoo.org/?_ga=1.86499544.1922104653.1389292904#/collections/CGZS000091

Posted

• by Budgieye moderator

I looked through your collection and there are nice green objects! I'm not sure which are Oiii objects, and it is a lot of work to track down a spectrum. Green things may also be stars, Lyman break galaxies and quasars, and it would take a spectrum to tell the difference. It seems that I am unable to tell the difference between a star, a pea and a quasar in these Hubble images. I put some objects in this discussion when I noted that there were oxygen emissions mentioned somewhere.

Posted

• yes very limited data. thanks for having a look Budgieye

Posted

• by c_cld

New preprint on Green Peas Submitted on 19 May 2015 to the Astrophysical Journal

#greenpea

Lyα emission from Green Peas: the role of circumgalactic gas density, covering, and kinematics Alaina Henry, Claudia Scarlata, Crystal Martin, Dawn Erb

We report Hubble Space Telescope/Cosmic Origins Spectrograph observations of the Lyα emission and interstellar absorption lines in a sample of ten star-forming galaxies at z~0.2. Selected on the basis of high equivalent width optical emission lines, the sample, dubbed "Green Peas," make some of the best analogs for young galaxies in an early Universe. We detect Lyα emission in all ten galaxies, and 9/10 show double-peaked line profiles suggestive of low H I column density. We measure Lyα /Hα flux ratios of 0.5-5.6, implying that 5% to 60% of Lyα photons escape the galaxies. These data confirm previous findings that low-ionization metal absorption (LIS) lines are weaker when Lyα escape fraction and equivalent width are higher. However, contrary to previously favored interpretations of this trend, increased Lyα output cannot be the result of a varying H I covering: the Lyman absorption lines (Lyβ and higher) show a covering fraction near unity for gas with N_{H I} >~ 10^{16} cm^{-2}. Moreover, we detect no correlation between Lyα escape and the outflow velocity of the LIS lines, suggesting that kinematic effects do not explain the range of Lyα /Hα flux ratios in these galaxies. In contrast, we detect a strong anti-correlation between the Lyα escape fraction and the velocity separation of the Lyα emission peaks, driven primarily by the velocity of the blue peak. As this velocity separation is sensitive to H I column density, we conclude that Lyα escape in these Green Peas is likely regulated by the H I column density rather than outflow velocity or H I covering fraction.

Posted

• by Rick_N.

103 Citations for the original Cardamone Green Peas paper 2009MNRAS.399.1191C from the ADS Databases:

Posted

• A paper entitled:

'Green Pea Galaxies Reveal Secrets of Lyα Escape' (v1 June 2015) by
Huan Yang, Sangeeta Malhotra, Max Gronke, James E. Rhoads, Anne Jaskot, Zhenya Zheng, Mark Dijkstra
http://arxiv.org/abs/1506.02885'

I should add that this paper's research has been questioned and might well be plagiarised.

Posted

• Cool paper, thanks for citing it Rick_Nowell! 😃

Posted

• by ccardamone scientist

Hi Everyone,

Sorry I just noted that this talk topic! I mentioned some of the recent paper results in http://blog.galaxyzoo.org/2015/07/07/eight-years-the-8th-paper-green-peas-living-fossils-of-galaxy-evolution/

I'm also happy to continue this conversation here if you have new questions about the Peas or are interested in hunting for new samples!

Posted

• Hey Carrie, nice to hear from you! Thanks for the link above as it's good to catch up. Gee, long time...

Personally, my lack of physics is beginning to tell in some of the more recent publications! The paper of Alaina Henry's is complicated going, but I am still finding the Jaskot & Oey 2014 paper (link below) a trial, especially the symbols. CII and CII*? SII and SII*? Enigmatic non-resonant emission? My quantum physics is very limited.

Any help would be much appreciated. Conversations are welcome. Pea hunts are always interesting! I wrote a list of 39 GPs on the 14th of December 2007, so next Monday will be eight years since then. Getting emotional now. It would be nice to hear from Zookeeper Kevin some time.

Best wishes!

Linking Ly-alpha and Low-Ionization Transitions at Low Optical Depth,
A. E. Jaskot, M. S. Oey,
http://arxiv.org/abs/1406.4413

Lyα emission from Green Peas: the role of circumgalactic gas density, covering, and kinematics,
Alaina Henry, Claudia Scarlata, Crystal L. Martin, Dawn Erb
http://arxiv.org/abs/1505.05149

Posted

• Very interested in hunting for new samples.Ive been looking but mostly purple peas so far.
B

Posted

• I´m also interested in looking för more Peas.

Posted

• Hi Carrie,

Ooh another pea hunt ! What are you suggesting ? 😃

Posted

• An informative blog post from Dr. Alaina Henry about the GPs and their Dark Matter properties, or lack of. The following link is from the 18th December:

http://alainahenry.com/2015/12/18/green-peas-and-dark-matter-q-a-with-richard-nowell-green-pea-enthusiast/

Posted

• by c_cld

New paper from Y.I. Izotov et al. Lyman continuum leaking from the compact star-forming dwarf galaxy
J0925+1403

One of the key questions in observational cosmology is the identification of the sources responsible for ionisation of the Universe after the cosmic Dark Ages, when the baryonic matter was neutral. The currently identified distant galaxies are insufficient to fully reionise the Universe by redshift z~6, but low-mass star-forming galaxies are thought to be responsible for the bulk of the ionising radiation. Since direct observations at high redshift are difficult for a variety of reasons, one solution is to identify local proxies of this galaxy population. However, starburst galaxies at low redshifts are generally opaque to their ionising radiation. This radiation with small escape fractions of 1-3% is directly detected only in three low-redshift galaxies. Here we present far-ultraviolet observations of a nearby low-mass star-forming galaxy, J0925+1403, selected for its compactness and high excitation. The galaxy is leaking ionising radiation, with an escape fraction of ~8%. The total number of photons emitted during the starburst phase is sufficient to ionize intergalactic medium material, which is about 40 times more massive than the stellar mass of the galaxy.

to appear in Nature on the 14th of January 2016

Figure 3: The double-peaked Lyα emission line in the COS spectrum of J0925+1403.

The centre of the emission line is shown by a vertical dashed line. The small separation of the two emission peaks is indicative of a low H I column density according to radiation transfer models for spherical geometry

pea SDSS J092532.36+140313.1 1237671262812897597 141.38484, 14.05364 09:25:32.36, +14:03:13.12

DR7 ObjId = 587745243087372534 in the list of 251 objects from Cardamone's 2009 paper

Hubble Space Telescope image of the compact green pea galaxy J0925. The diameter of the galaxy is approximately 6,000 lightyears, and about twenty times smaller than the Milky Way. Credit: © Ivana Orlitová, Astronomical Institute, Czech Academy of Sciences (Prague)

Posted

• by ccardamone scientist

Just a note to check out Kyle's new blog post about a new research paper on the peas!
http://blog.galaxyzoo.org/2016/01/17/green-pea-galaxies-may-have-been-responsible-for-re-ionizing-the-universe/

Posted

• An article from Physics World about Green Peas: 'Green-pea' galaxies may have kick-started universal reionization

Posted

• Thanks Geoff ! 😄

Posted

• Some observations of 13 GPs as part of Hubble Space Telescope Program 14080 are scheduled for varying dates from December 2015 until the end of September 2016. The PIs are Anne Jaskot and Sally Oey. Quoting from the abstract:

LyC, Ly-alpha, and Low Ions in Green Peas: Diagnostics of Optical Depth, Geometry, and Outflows.

"The "Green Peas" are extreme, low-redshift starbursts that are under intense scrutiny as a possible class of Lyman continuum (LyC) emitting galaxies. Their extreme [O III]/[O II] ratios resemble those of z>2 Ly-alpha emitters (LAEs) and suggest conditions conducive to high LyC escape fractions. Our initial COS study of four extreme GPs demonstrated the diagnostic power of Ly-alpha emission plus low-ionization absorption and emission lines to simultaneously relate optical depth, neutral gas geometry, and Ly-alpha radiative transfer."

Interestingly, if I've got the coordinates right, none of them are Green! Colours are mostly purples and blues. J160810 has the highest OIII to OII flux ratio in the SDSS catalogue, which seems to be near 30. Above 5 is high.

http://www.stsci.edu/hst/phase2-public/14080.pro

http://www.stsci.edu/cgi-bin/get-proposal-info?id=14080&observatory=HST

http://www.stsci.edu/cgi-bin/get-visit-status?id=14080&markupFormat=html&observatory=HST

Posted

http://talk.galaxyzoo.org/#/boards/BGZ0000001/discussions/DGZ0001682

Two of the above 13 HST targets are already posted here!

Posted

• by Budgieye moderator

I found a faint greeny -blue object in DECaLS. Any ideas?

At the bottom of the first image.

http://legacysurvey.org/viewer?ra=120.2254&dec=6.1624&zoom=15&layer=decals-dr2

Posted

• An ArXiv pre-print is available for Izotov's new study of four GPs observed by the COS onboard the HST. Escape fractions of LyC up to 13% are found. http://arxiv.org/abs/1605.05160

Detection of high Lyman continuum leakage from four low-redshift compact star-forming galaxies
Y. I. Izotov, D. Schaerer, T. X. Thuan, G. Worseck, N. G. Guseva,I. Orlitova & A. Verhamme

The abstract states:
"Following our first detection reported in Izotov et al. (2016), we present the detection of Lyman continuum (LyC) radiation of four other compact star-forming galaxies observed with the Cosmic Origins Spectrograph (COS) onboard the Hubble Space Telescope (HST). These galaxies, at redshifts of z~0.3, are characterized by high emission-line flux ratios [OIII]5007/[OII]3727 > 5. The escape fractions of the LyC radiation fesc(LyC) in these galaxies are in the range of ~6%-13%, the highest values found so far in low-redshift star-forming galaxies. Narrow double-peaked Lyalpha emission lines are detected in the spectra of all four galaxies, compatible with predictions for Lyman continuum leakers. We find escape fractions of Lyalpha, fesc(Lyalpha) ~60%-90%, among the highest known for Lyalpha emitters (LAEs). Surface brightness profiles produced from the COS acquisition images reveal bright star-forming regions in the center and exponential discs in the outskirts with disc scale lengths alpha in the range ~0.6-1.4 kpc. Our galaxies are characterized by low metallicity, ~1/8-1/5 solar, low stellar mass ~(0.2 - 4)e9 Msun, high star formation rates SFR~14-36 Msun/yr, and high SFR densities Sigma~2-35 Msun/yr/kpc^2. These properties are comparable to those of high-redshift star-forming galaxies. Finally, our observations, combined with our first detection reported in Izotov et al. (2016), reveal that a selection for compact star-forming galaxies showing high [OIII]5007/[OII]3727 ratios appears to pick up very efficiently sources with escaping Lyman continuum radiation: all five of our selected galaxies are LyC leakers."

Posted

• by zutopian

Here is a new paper concerning the discovery process of the Green Peas!:

Giving Citizen Scientists a Chance: A Study of Volunteer-led Scientific Discovery
Author: Miranda C. P. Straub

(...) This paper gives a narrative of the 11-month, volunteer-led discovery process of the Green Pea galaxies and the transition to the Galaxy Zoo science team’s involvement to analyze and report on a new class of galaxy. (...)

Acknowledgements
This work was funded in part by the National Science Foundation award DRL-0941610 under the leadership of Lucy Fortson. I thank her and Kyle Willett for informative discussions in the early stages of this work.
I also thank Carolin Cardamone for her insight into this fascinating discovery and (...).

http://theoryandpractice.citizenscienceassociation.org/articles/10.5334/cstp.40

The paper was published today in the 1st issue of the "open access" journal "Citizen Science: Theory and Practice".

Posted

• by c_cld

Amazing compact pair

1237646587712766071 z_spec 0.116

![SpecObjID = 8170878386764967936](http://skyserver.sdss.org/dr12/en/get/SpecById.ashx?id=8170878386764967936 =609x435)

Posted

• A study about GPs of different colours has been published which finds 'important differences'. It's a poster from the "Proceeding of the conference; The Interplay between Local and Global Processes in Galaxies". The abstract states:

"The coloured galaxies were recently discovered in the data-base of the SDSS. They are all compact and show unsual colours in the gri composite image. The most studied so far are those called "green peas" because of their green colour but there are bright blue, purple, red, orange, grey and pink. The green, purple and blue also share a large equivalent width in the oxygen forbbiden line [OIII]5007, larger than 200 Å, being more intense than Halpha. This is quite unsual even for star forming galaxies. Although some authors have concluded that all three are the same kind of galaxies, we have studied them carefully and found out that there are important differences among the properties, including the scaling relations."

The poster concludes: "Scaling relationships between some of the parameters are fundamental to understand the evolution of these galaxies. It can be seen the Green peas do not have the same behaviour that the blue and purple marbles for most of the relationships. As can be seen, the green peas do not have the same steep than the blue and purple marbles for most of the relationships. This could be a consequence of the nature of the starburst process, or because we are working with different types of galaxies.."

Title: Are all the coloured galaxias the same?

Authors: Hidalgo-Gámez, A. M.; Miranda-Pérez, B. E.; Vega-Acevedo, I.; Castañeda, H.; Saviane, I.

06/2016 Universidad Nacional Autonoma de Mexico

Posted

• Cool! 😃

It'll be an interesting paper when it's out ... ("Hidalgo-Gámez et al., in preparation").

Posted

• I wonder how different they are? It seems odd that one type of starburst galaxy has a colour corresponding to that type. I thought, like others, they were GPs at different redshifts. Or is it something that combines the two ideas: type and/or redshift?

A post by Budgieye which has some 'coloured Peas' from the GZF:

Friday 21 May 2010 Peas! Blue, purple, white, green and red

Posted

• A comprehensive study of the 'Green Bean' galaxies was published in July 2016. Green Bean galaxies are AGN ionisation echoes- large voorwerps- and their name is inspired by the GPs, as pointed out in the first Green Bean paper from 2013. Somewhere on the GZ Forum there is possibly a thread about them. There is a Wikipedia article on GB galaxies which is handy and up-to-date. Nice pic.

In this recent study, GBGs are compared to high redshift 'Lyman Alpha Blobs'. Familiar names are among the authors:

About AGN ionization echoes, thermal echoes, and ionization deficits in low redshift Lyman-alpha blobs

Mischa Schirmer, Sangeeta Malhotra, Nancy A. Levenson, Hai Fu, Rebecca L. Davies, William C. Keel, Paul Torrey, Vardha N. Bennert, Anna Pancoast, James E. H. Turner.

https://en.wikipedia.org/wiki/Green_bean_galaxy

J224024.1−092748 (abbreviation J2240)

Posted

• Lyman alpha escape in Green Pea galaxies (give peas a chance)

Yet more time on the Hubble Pea Telescope! As part of Sangeeta Malhotra's HST program 14201, twenty, yes twenty, GPs have been observed with the Cosmic Origins Spectrograph. Starting in September 2015 and at various times up to late June 2016, the GPs have been observed for a study on Lyman Alpha emitters. This will be the fourth time the HST/COS has observed various GPs. Twenty! The abstract states:

"What makes a star-forming galaxy a Lyman-alpha (LyA) emitter? The answer to this question is essential to understand a large fraction of high-redshift galaxies and reionization. This answer is best found for low-z galaxies, where there is abundant multiwavelength data but UV spectroscopy of LyA line is needed with HST. Green Pea galaxies are the best low-redshift analogs of high redshift LyA galaxies, because they (1) have high specific star-formation rates, (2) have metallicities that are unusually low for their stellar masses, and (3) are spatially compact. (4) Archival COS spectra show LyA emission from all observed Green Peas; and high EW LyA from 7 out of 9 GPs. We propose to systematically study the dependence of LyA escape fraction on (A) metallicity (B) dust column (C) porosity of neutral gas and (D) outflow velocities to determine the dominant factor(s) in making LyA escape possible. The nine GPs available in the archives are the ones with lowest metallicities and dust extinctions. We propose COS spectroscopy for 20 Green Peas to span the full range of their metallicities, dust columns, and H-alpha equivalent widths. With COS spectra we will measure Lya flux and compare it to H-alpha to determine Lya escape fraction. We will compare velocity profiles of LyA and H-alpha to determine the outflow velocities, and constrain absorbing columns of neutral gas. By measuring optical depth in SiII and CII we will estimate the covering fraction of neutral gas. NUV images taken for acquisition will provide the morphologies of the star-forming regions. Finally, we will compare the Lya Luminosity and EWs to high redshift samples."

Lyman alpha escape in Green Pea galaxies (give peas a chance)
http://archive.stsci.edu/proposal_search.php?id=14201&mission=hst

HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 14201
http://www.stsci.edu/hst/phase2-public/14201.pro

https://en.wikipedia.org/wiki/Cosmic_Origins_Spectrograph

Posted

• Spectral Diagnostics for the Reionization Era: Exploring the Semi-Forbidden CIII] Emission in Low Metallicity Green Pea Galaxies

Additionally, another large GP survey has taken place on the HST between January and July 2016 at various times. The 12 GP observations are the fifth HST study and use the Space Telescope Imaging Spectrograph (STIS). Swara Ravindranath is the P.I. The proposal abstract for GO:14134 states:

"Proposal Abstract
Identifying the sources of reionization at z>6 is one of the primary science goals of cosmology and the main driver for upcoming large telescopes. The main tools for confirming the redshifts and tracing the earliest stellar population are the UV continuum and Ly-alpha emission. At z>6 and further into the reionization era these UV photons are severly quenched by the largely neutral IGM, making it crucial to seek other diagnostics. The semi- forbidden CIII]1909 emission is emerging as promising tool based on the strength and frequency of its observation in low metallicity galaxies at z>2. We propose to use the HST STIS to observe the local analogs of such a population locally, which are the recently discovered ''Green Pea'' galaxies. We propose to observe the CIII] line and use it with the shorter wavelength observations in the HST archive to (1) establish the ubiquity of this line, (2) calibrate the CIII] emission strength against Ly-alpha to explore its usefulness as a potential redshift indicator, (3) derive C/O ratios from CIII]1909 and OIII]1663 lines, and study their dependence on metallicity, and (4) construct high quality composite rest-UV spectra of these star-forming dwarfs. These new calibrations and templates will serve as important diagnostic tools for high redshift galaxies."

Spectral Diagnostics for the Reionization Era: Exploring the Semi-Forbidden CIII] Emission in Low Metallicity Green Pea Galaxies
http://archive.stsci.edu/proposal_search.php?id=14134&mission=hst

HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 14134 http://www.stsci.edu/hst/phase2-public/14134.pro

https://en.wikipedia.org/wiki/Space_Telescope_Imaging_Spectrograph

Posted

• by NGC3314 scientist

Rick Nowell pointed me to this thread, and it’s worth chiming in with some background on the recent Green Bean galaxy results.

Misha Schirmer of the Gemini Observatory happened across the first Green Bean while working on large-scale structure using deep CFHT survey data. That got him interested in their occurrence, so he started an automated search from the SDSS database; since these objects show very strong [O III] at redshifts z=0.2 to 0.4, he started with the same color criteria as the GZ Green Pea search settled on, but reversed the size threshold. Green Bean candidates had SDSS sizes larger than 2 arcseconds while Peas are smaller. This search gave hundreds of false positives (image blends, artifacts) but also gave about 20 actual [O III] emission clouds. When his team examined the neighborhoods in SDSS, they are found near AGN, but AGN which are energetically insufficient to ionize the clouds as strongly as we see. This all sounded familiar - as they concluded in their original reporting paper, the Green Beans are in general analogs to the GZ Voorwerp(jes), at higher redshifts and in some cases requiring their AGN to have been even brighter in the recent past (100,00 years or so before we observe them now).

As with the Voorwerpjes, this sample fairly cried out for more data. We were able to help out with the last unknown redshifts for some (and started communicating enough that Mischa Schirmer has been part of our team getting Gemini data on the Voorwerpjes, while I’ve been on his in examining the UV properties of Green Beans). The latest
Green Bean paper includes Chandra X-ray observations, which strengthen the case for fading of the AGN, and also gives the first evidence for a conjecture on how these photoionization echos might contribute to a puzzling phenomenon which was most common early in cosmic history - Lyman alpha blobs.

In the late 1990s, increasingly detailed study of galaxy environments at redshifts 2-3 often found gigantic nebulae which were very bright in Lyman alpha. Lyman alpha is the strongest emission line of hydrogen, emitted deep in the ultraviolet
1216 Angstroms = 121.6 nm, so it takes these high redshifts to see it from the ground). There are multiple ways to produce such a huge ionized nebula - widespread and intense star formation, a powerful AGN via either UV radiation or jets, or exotic possibilities such as gas first falling together to grow an initially small galaxy. The most interesting of these blobs were the “orphans” - where there was no embedded galaxy or AGN bright enough to account for the Lyman alpha clouds. Episodically bright AGN are a natural way to account for such things. I talked about this last year while visiting Arizona State University, where ASU professor Sangeeta Malhotra pointed out an important facet that I had missed - the special properties of Lyman alpha make the interpretation perhaps more likely and powerful than I fist thought. Because hydrogen is so common, and its atoms in low-lying energy states can absorb as well as emit Lyman alpha so strongly, she had calculated how radiation at this wavelength diffuses on a random walk rather than streaming right out of the nebula like other wavelengths. This means that such an echo will glow in Lyman alpha for as much as 10 times longer than other emission line (which fits since some Lyman alpha blobs have essentially no emissions from other species such as helium and carbon, which we once spent a week of time at Kitt Peak to show).

So far, UV images from the GALEX survey are fully consistent with this idea, that the Green Beans are strong Lyman alpha emitters. But the real test is in coming months, when Hubble is scheduled to get UV images and spectra of three of them; then it will be clear whether the Green Bean galaxies are not only like Voorwerpjes, but help explain the high-redshift Universe as well.

(Updated to fix really confusing error when I once typed Peas instead of Beans)

Posted

• by zutopian

New paper:

Lyα and UV Sizes of Green Pea Galaxies
Huan Yang, Sangeeta Malhotra, James E. Rhoads, Claus Leitherer, Aida Wofford, Tianxing Jiang, Junxian Wang

Green Peas are nearby analogs of high-redshift Lyα-emitting galaxies. To probe their Lyα escape, we study the spatial profiles of Lyα and UV continuum emission of 24 Green Pea galaxies using the Cosmic Origins Spectrograph (COS) on Hubble Space Telescope (HST). We extract the spatial profiles of Lyα emission from their 2D COS spectra, and of UV continuum from both the 2D spectra and NUV images. The Lyα emission shows more extended spatial profiles than the UV continuum in most Green Peas. The deconvolved Full Width Half Maximum (FWHM) of the Lyα spatial profile is about 2 to 4 times that of the UV continuum in most cases. The Lyα light shows significant offsets from the UV continuum in four galaxies and central absorption in one galaxy. We also compare the spatial profiles of Lyα photons at blueshifted and redshifted velocities in eight Green Peas with sufficient data quality, and find the blue wing of the Lyα line has a larger spatial extent than the red wing in four Green Peas with comparatively weak blue Lyα line wings. These results together indicate that most Lyα photons escape out of Lyα-emitting galaxies through many resonant scatterings in the HI gas. Five Lyman continuum (LyC) leakers in this sample have similar Lyα to UV continuum size ratios (1.4−4.3) to the other Green Peas, indicating their LyC emission escape through ionized holes in the interstellar medium.

(Submitted on 18 Oct 2016)
https://arxiv.org/abs/1610.05767

Posted

• by zutopian

New paper:

Local analogues of high-redshift star-forming galaxies: integral field spectroscopy of green peas
Authors: Emma K. Lofthouse, Ryan C. W. Houghton, Sugata Kaviraj

We use integral field spectroscopy, from the SWIFT and Palm3K instruments, to perform a spatially-resolved spectroscopic analysis of four nearby highly star-forming `green pea' (GP) galaxies, that are likely analogues of star-forming systems at z~2.5-3. (...)
Nevertheless, the fact that the other two GPs appear morphologically undisturbed suggests that mergers (including minor mergers) are not necessary for driving the high star formation rates in such galaxies. We show that the GPs are metal-poor systems (25-40 per cent of solar) and that the gas ionization is not driven by AGN in any of our systems, indicating that AGN activity is not co-eval with star formation in these starbursting galaxies.

(Submitted on 23 Jan 2017)
https://arxiv.org/abs/1701.07015

Posted

• Thanks, that paper has been years in finally coming to publication. The new Yang et al. paper is important:

Ly$\alpha$ profile, dust, and prediction of Ly$\alpha$ escape fraction in Green Pea Galaxies

Posted

• "Green Peas emit X-rays: Extreme Star Formation in Early Universe Analog Galaxies" by M. Borby and P. Karet.

"Luminous compact galaxies (LCGs), Lyman Alpha Emitters (LAEs), and Lyman Break Analog galaxies (LBAs) are all used as proxies for star-forming galaxies in the early Universe (z ≥ 6). The X-ray emission from such galaxies has been found to be elevated compared to other star-forming galaxies in our local Universe. It has been suggested that this may be due to the lower metallicity seen in these proxies to high-redshift galaxies and the elevated X-ray emission may affect the heating and Reionization evolution of the early Universe. Our previous studies have suggested the existence of an LX-SFR-metallicity plane for all star-forming galaxies. We present these results in the context of our newest Joint Chandra/HST study containing the first X-ray detection of the Green Pea galaxies, a population of compact starburst galaxies discovered by volunteers in the Galaxy Zoo Project (Cardamone+2009). The galaxies were given the name Green Peas due to their compact size and green appearance in the gri composite images from SDSS. The green color is caused by a strong [OIII]λ5007Å emission line, an indicator of recent star formation. We observed a few of the most promising candidates with joint Chandra/HST observation and discuss our findings here."

X-RAYS FROM GREEN PEA ANALOGS HST Proposal 13940

http://archive.stsci.edu/proposal_search.php?id=13940&mission=hst

HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 13940

http://www.stsci.edu/hst/phase2-public/13940.pro

Posted

• A new paper about the x-ray observations of two GPs has been posted to arXiv. This is the first detection of Green Pea analogs in X-rays.

"X-ray observations of two metal-deficient luminous compact galaxies (LCG) (SHOC~486 and SDSS J084220.94+115000.2) with properties similar to the so-called Green Pea galaxies were obtained using the {\emph{Chandra X-ray Observatory}}. Green Pea galaxies are relatively small, compact (a few kpc across) galaxies that get their green color from strong [OIII]λ5007\AA\ emission, an indicator of intense, recent star formation. These two galaxies were predicted to have the highest observed count rates, using the X-ray luminosity -- star formation rate (LX--SFR) relation for X-ray binaries, from a statistically complete sample drawn from optical criteria. We determine the X-ray luminosity relative to star-formation rate and metallicity for these two galaxies. Neither exhibit any evidence of active galactic nuclei and we suspect the X-ray emission originates from unresolved populations of high mass X-ray binaries. We discuss the LX--SFR--metallicity plane for star-forming galaxies and show that the two LCGs are consistent with the prediction of this relation. This is the first detection of Green Pea analogs in X-rays."

X-rays from Green Pea Analogs

Matthew Brorby, Philip Kaaret

https://arxiv.org/abs/1705.07958

Posted

• by ccardamone scientist

You all (especially Rick!) have been doing an amazing job keeping up with the peas literature. I'm going to talk about some of these tomorrow (mostly in a 1 slide summary), and talk a bit about selecting a new sample from DR13 (where we have more spectra, but not more photometry) from SDSS. I keep saying I want to follow up on the peas and getting side tracked by other projects. I'm hoping to move forward with them now - looking a bit into their 'environments'. My slides will be designed for the other astronomers for the meeting, but I'll remember to come back here to answer any questions if they come up.

Carie

Posted

• by JeanTate

Posted

• by JeanTate

My question, as a comment in the #GZoo10 Day 3 blog post, was too late for the session on Green Peas (you can watch Carie's presentation in the livestream Session 6, starting at ~56.5 minutes), but she kindly answered it afterwards. Here's the exchange; me:

Could you say a few words about blueberries and red peas?

Carrie's response:

Hi Jean!

I think maybe asking about the “Red Nugget’s” that astronomers found in the Sloan Sky Survey. They are compact but red galaxies. The galaxies, like peas, are also analogous to high redshift galaxies, however they represent a very different type of galaxy – more massive and likely rather passive (not forming stars). Since they were discovered there have been many follow-up studies There is a great story about them at the CFA – https://www.cfa.harvard.edu/news/2013-24 and one at astrobites (https://astrobites.org/2013/04/14/digging-up-red-nuggets-in-local-elliptical-galaxies/).

There was a recent article about Blueberry galaxies (Yang et al 2017), these are much more similar to the peas being extreme emission line galaxies, analogous to high redshift star forming galaxies. The study searched for lower mass, closer galaxies (so they didn’t appear green in the Sloan images as the peas did because OIII wasn’t bright in the SDSS ‘r’ band).

Hope this answers your question. If you have more – feel free to reach out over the green peas thread on talk!

So first, a really big THANK YOU CARRIE! for that response. 😃

As you can see, I knew about blueberries, but not Red Nuggets.

I am most interested in space densities: unless they're incredibly rare or form only during a very narrow slice of Hubble time, there should be at least some Green Peas (with typical GP stellar masses etc) close enough that they appear as blueberries ... but apparently not?

Also, at least some of the brighter and more massive GPs should be visible - as red peas - once their redshift puts the [OIII] into the i band. And unlike low-z versions, there should be more of them in SDSS (space density again). These red peas would be very different from Red Nuggets: their optical emission would be dominated by the same forbidden lines as GPs (esp [OIII]), rather than red stars (whose light dominates in Red Nuggets).

There would likely also be some transition objects, where redshifted [OIII] falls at the red end of the g filter and blue end of the i one; they may not be easily visible, given that both filters' sensitivies (quantum efficiencies) are considerably lower there.

So, has anyone searched for either? And if so and none have been found, doesn't this make GPs an extraordinary class of object, one which appears only during a very thin slice of recent history?

Posted

• by c_cld

Could we find green peas in "Galaxies nurseries" project?

I posted in "Galaxies nurseries" talk 10230564 and 10230565 for their #emission_line (s) 0 and 1 with a guess of a green quasar. Another possibility would be a green pea as this galaxy 1237654383056650509 ra, dec 154.070816 59.406322 is right in that kind of color-color space but without a SDSS spectrum.

I have no reference or template of an IR spectrum of a green pea and can't infer further group membership.

Could @ccardamone help?

Posted

• In principle, yes.

However, it may be that the most luminous GP (real one) would not be detected by the HST, at the minimal redshift for [OIII]5007 to appear at the blue end of a spectrum.

As the research on GPs shows clearly, QSOs/AGNs and GPs are about as different as one could imagine (the prodigious [OIII] comes from very different astrophysics; said another way, GPs do not have accretion disks around SMBHs).

Posted

• by c_cld

May be a galaxy at redshift 0.3 could exhibit Hydrogen Paschen lines that all lie in the infrared band suitable for the HST WFC3 Grism Resource IR/ G141/ wavelength range 1075-1700 nm.

My object 1237654383056650509 posted on "galaxy nursery talk" would eventually show Pashen lines, don't you think?

Guess: redshift 0.321 for fitting pashen line 954.6nm at peak 12611 Å and pashen line 1094nm at peak 14332Å.

Posted

• by c_cld

" Do GP nebulae produce similarly strong line emission in the IR?" thread started by @JeanTate in GZ forum on: May 03, 2013.

@NGC3314 provided some answers with reference to the Prototypical Starburst Galaxy NGC 7714.

Lines to be considered:
He I 952.6 nm, Paγ 1094 nm, O i 1128.7 nm, Paß 1281.8 nm

Posted

• Hey, thanks for the mention! The Wikipedia article is pretty much up-to-date, though contributions are always needed. The latest research mentioned at GZ10 seems exciting- look forward to the study.

Posted

• Relevant to whether there are any red peas (GPs at higher redshift): the Green Bean (GB) discovery paper (Schirmer+ 2013) reports results of an attempt to find GBs at higher redshifts, where the [OIII] lines are shifted into the i band (~0.39<z<0.69). They report finding eight candidates (Table 5, Figure 13).

There are, as Bill points out (further details in the Schirmer+ paper), some differences in how GPs and GBs were searched for. The most obvious is size (GBs appear bigger than GPs), but there's also a difference or two in the color selection criteria. So perhaps there are indeed red peas, but no one has done the kind of SQL search Schirmer+ report for GBs followed by careful inspection of the results (most of which are likely to be something other than red peas) ...

Posted

• by JeanTate

In this Dolorous_Edd RGZ Talk post the host of the #asymmetric #triple radio source is STAR (photometric pipeline) zsp 0.864 (!) SDSS J161756.89+545113.5:

From the spectrum, it seems to be a much-higher-redshift GP:

There may be enough data to make an estimate of where it falls in a BPT diagram ... but it's surely far too luminous to be a GP (were it to be at z ~0.3 say), right?

Posted

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

I think part of the answer (on whether they are a unique set of objects in a unique slice of time) depends on the definition - which is actually something i'm pondering right now.

Fundamentally what does it mean to be a 'pea' galaxy. In the original paper, we started with a definition of an appearance in a survey and then went on to characterize a set of intrinsic physical properties. But these two sets of properties rarely map 1-1 onto each other.

So IF peas are small, round green things in SDSS, then yes some are Star Forming, compact galaxies whose color is dominated by OIII emission in the 3 bands used to make the 3 color images. But there might also be lots of other things that meet the same color-space/size criteria who turn out to be strange artifacts on the image, or galaxies at a very different redshift who have the same appearance due to another emission line falling into the 'r' band image.

In contrast other studies have defined "Peas" as objects with strong OIII emission powered by star formation, and started out by searching the spectral archive of SDSS (e.g., Isatov et al. 2011), who end up with a larger sample of objects spanning a larger redshift range.

So in the end, "blueberries", "Red nuggets", "Green Beans" and all the like can be overlapping sets of objects (similar in appearance on images, spectra line features or other intrinsic properties like size or star formation), but each a unique sample based on it's own selection.

Also, when you start looking at different redshifts, you start to have to consider effects of galaxy evolution over time . . . redshift 0.05 was less than 1 billion years ago, redshift 0.15 was nearly 2 Billion years ago, and redshift 0.35 (near the top of our original redshift range of selection) was nearly 4 billion years ago. If you go to even higher redshifts, you're looking at younger galaxies at stages earlier in the universe.

My random musings in response to your question Jean ....

Posted

• Wow, tx Carrie, this is really interesting ! 😄

Posted

• Green Beans are big Voorwerps, but not star-forming non-AGN galaxies like GPs, surely? Blueberries are nearby GPs, but very small one with very low metallicities. I've not heard of red nuggets before. Perhaps Yuri Izotov's title of 'Compact Star-forming galaxies' (CSFG) is helpful.

https://en.wikipedia.org/wiki/Green_bean_galaxy

Posted

• It's a bit more complicated than that.

In the GP discovery paper (Cardamone+ 2009), they are shown to be a heterogeneous class; from Table 1: 9 Seyfert (Sy) type 1's, 10 Sy2, 13 transition objects, 80 star forming (one of the Sy1's is a broadline AGN).

There are 17 GBs in the Schirmer+ 2013 discovery paper, all of which are Sy2 AGN ("All confirmed GBs are type-2 AGNs, as broad-line components have not been identified"). They are similar to Voorwerps in that the green so visible in SDSS images is extended [OIII] emission (plus other species of course), almost certainly almost entirely ionized by an earlier, much more active AGN (not all Voorwerps show current AGN activity). So some GPs are simply smaller GBs.

Red Nuggets are quite different: compact red galaxies with no sign of any EELRs, NLRs, or AGN activity; I think they're more like bigger and more massive versions of the ultra-compact dwarfs found near some cD galaxies in the centers of rich clusters, but with star-formation having ceased much earlier.

Posted

• by JeanTate

Possible red pea, zsp 0.436 SDSS J100429.78+462933.4:

If you click on the interactive spectrum link, you'll see that the model fit substantially underestimates the actual [OIII] flux (and [NeIII]), overestimates the [SII] flux, and that there's almost no continuum emission. No sign of line broadening, e.g. in H-alpha, so it's certainly not a Sy1. It may be the host of a #double (double lobe radio emission, see my Comment here), which would point to an AGN rather than a starburst (both are possible of course).

Pity it's not a purer 'red' color ... 😃

Posted

• by JeanTate

zsp 0.157 SDSS J110419.21+154508.2, Green Pea? or Green Bean?

Dolorous_Edd pointed to it, in this RGZ Comment. NED has 5 refs, but none which report GPs or GBs ...

Posted

• by bluemagi

Hello
Been working with Quasars. Came across these:
1237666299481686697 Z:.626
1237651752954823293 Z:.726
1237651735223009867 Z:.732
1237665570901459900 Z:.864
1237665567683838729 Z:.882
1237668311087513911 Z:.882
Thought they might fit in the Red Nuggets category.
Also,Possible Green Bean 1237659119871525118
Cheers, Magi

Posted

• zsp 0.266 SDSS J162209.41+352107.5, one of the original (Cardamone+ 2009) GPs:

zsp 0.864 SDSS J161756.89+545113.5, an "IR pea"? No NED refs:

zsp 0.732 SDSS J122656.48+013124.2, a broadline QSO with very strong [OIII] emission; 41 refs in NED

zsp 0.626 SDSS J031950.52-005850.4, a red pea (broadline QSO):

I don't think the rest of your nice candidates could be called "peas", bluemagi. And none are Red Nuggets. 😉

Posted

• by bluemagi

Thanks, Jean Tate.

Posted

• Special Green Pea birthday! Ten years since citizen scientist 'Nightblizzard' posted the first Pea on the GZForum July 28th 2007. Hanny started the GP thread on the 12th August 2007. 157 NED citations and counting...

The green galaxy

Posted

• That's awesome! Thanks for noticing the 10th anniversary of the very first pea!

Posted

• From Alice's GZ blog:

"The earliest topic to contain a green object we now know to be special is Topic No. 158, “The Green Galaxy”, on Day 2 of the forum’s existence. Nightblizzard first posted two galaxies with apparent greenness around them."

https://blog.galaxyzoo.org/2009/07/07/peas-in-the-universe-goodwill-and-a-history-of-zooite-collaboration-on-the-peas-project/

Posted

• 2017 has so far seen three HST programs. These are:

1. LyC, Ly-alpha, and Low Ions in Green Peas: Diagnostics of Optical Depth, Geometry, and Outflows

PI: Dr. Anne Jaskot Smith College , CoI: Dr. Sally Oey University of Michigan OBSERVING PROGRAM 14080

"The "Green Peas" are extreme, low-redshift starbursts that are under intense scrutiny as a possible class of Lyman continuum (LyC) emitting galaxies. Their extreme [O III]/[O II] ratios resemble those of z>2 Ly-alpha emitters (LAEs) and suggest conditions conducive to high LyC escape fractions. Our initial COS study of four extreme GPs demonstrated the diagnostic power of Ly-alpha emission plus low-ionization absorption and emission lines to simultaneously relate optical depth, neutral gas geometry, and Ly-alpha radiative transfer. We now propose to test this understanding by confirming these relationships and trends: we will combine these data with new COS spectra of 13 of the most extreme GPs, extending our analysis to a statistically significant sample."

http://www.stsci.edu/hst/phase2-public/14080.pro

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2 )How does ionizing radiation escape from galaxies?

PI: Dr. Ivana Orlitova Astronomical Institute, Academy of Sciences of CR, CoI: Prof. Matthew James Hayes Stockholm University
CoI: Dr. Anne Verhamme Observatoire de Geneve, CoI: Prof. Daniel Schaerer Observatoire de Geneve, CoI: Dr. Jens Melinder Stockholm University, CoI: Prof. Goeran Oestlin Stockholm University, CoI: Dr. Yuri I. Izotov Ukrainian National Academy of Sciences
CoI: Prof. Trinh Xuan Thuan The University of Virginia, CoI: Dr. Natalia G. Guseva Ukrainian National Academy of Sciences, CoI: Dr. Gabor Worseck Max-Planck-Institut fur Astronomie, Heidelberg OBSERVING PROGRAM 14656

"Search for sources that reionized the Universe from z~15 to z~6 is one of the main drivers of present-day astronomy. Low-mass star-forming galaxies are the most favoured sources of ionizing photons, but the searches of escaping Lyman continuum (LyC) have not been extremely successful. Our team has recently detected prominent LyC escape from five Green Pea galaxies at redshift ~0.3, using the HST/COS spectrograph, which represents a significant breakthrough. We propose here to study
the LyC escape of the strongest among these leakers, J1152, with spatial resolution. From the comparison of the ionizing and non-ionizing radiation maps, and surface brightness profiles, we will infer the major mode in which LyC is escaping."

http://www.stsci.edu/hst/phase2-public/14656.pro

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1. Lyman continuum leaking in luminous compact star-forming galaxies

PI: Dr. Yuri I. Izotov Ukrainian National Academy of Sciences, CoI: Dr. Natalia G. Guseva Ukrainian National Academy of Sciences,
CoI: Dr. Ivana Orlitova Astronomical Institute, Academy of Sciences of CR, CoI: Prof. Daniel Schaerer Observatoire de Geneve
CoI: Prof. Trinh Xuan Thuan The University of Virginia, CoI: Dr. Anne Verhamme Observatoire de Geneve, CoI: Dr. Gabor Worseck Max-Planck-Institut fur Astronomie,Heidelberg, CoI: Prof. Klaus J. Fricke Universitats-Sternwarte Gottingen. OBSERVING PROGRAM 14635

"One of the key questions in observational cosmology is the identification of the sources responsible for cosmic reionization. The general consensus is that a population of faint low-mass galaxies must be responsible for the bulk of the ionizing photons. However, until recently, attempts at identifying individual galaxies showing Lyman continuum (LyC) leakage have only found very few such galaxies, both at high and low redshifts. A breakthrough was recently achieved by Izotov et al. (2016ab), who detected LyC emission in five out of five low-redshift (z~0.3) luminous compact star-forming galaxies (LCGs) with robust LyC escape
fractions of 6-13%, using HST/COS observations."

http://www.stsci.edu/hst/phase2-public/14635.pro

Posted

• by JeanTate

From today's astro-ph (in arXiv): "Census of the Local Universe (CLU) I: Characterization of Galaxy Catalogs from Preliminary Fields". Here's the abstract (link):

We present a Census of the Local Universe (CLU) -- a combination of the largest area Hα survey for nearby emission-line galaxies to date as well as a compilation of all publicly available galaxy catalogs out to a distance of 200 Mpc. With the Palomar 48-inch telescope, our Hα survey images ≈3π of the sky (3626 pointings) in 4 narrowband filters to an Hα flux limit of 10−14 erg/s/cm2 at 90% completeness. To characterize the completeness and contamination of the Hα survey, we undertook a study of 14 preliminary fields (0.3% of total pointings) where we have obtained spectroscopic follow-up of all galaxy candidates with no previous distance information and a narrow-band color excess greater than 2.5σ. Comparison of the resulting CLU-Hα galaxy catalog to a statistically complete sample of star-forming galaxies in a 11 Mpc volume (the LVL sample), we find that the Hα survey would be complete to 85% in star-formation (using Hα flux corrected for extinction as a proxy) and 70% in stellar mass at 200 Mpc. The contamination from high-redshift galaxies is lower than 8% (40%) for a 5σ (2.5σ) color excess. Even with just 290 emission-line galaxies in the 14 preliminary fields, we find several interesting objects: 7 newly discovered blue compact dwarfs (aka, blueberries), 1 new green pea, 1 new QSO, and a known planetary nebula. The extreme galaxies (green pea and blueberries) have high star formation rates, low stellar masses, and low metallicities and could be local analogs to higher redshift primordial galaxies. The existence of these objects in our preliminary Hα sample exemplifies that the full CLU-Hα survey can be used as a discovery machine for a wide variety of objects in our own Galaxy and extreme galaxies out to intermediate redshifts.

I wonder how many more blueberries and green peas await discovery?

Posted

• Another likely blueberry, no photoZ or redshift:

GALEXASC J013821.83+290022.4

G=19.0
R=19.9
I=19.5

assuming Z less than 0.07, and assuming the fuzziness above it is a member of the galaxy, it would be less than 20,000 light years across. A lack of far-infrared emission rules out a quasar, and the particular color rules out a white dwarf.

Posted

• Another blueberry? I am getting too good at seeing purple.

SDSS J083309.69+114800.4

G=20.1
R=20.9
I=20.5

PhotoZ = 0.256 +/- 0.0722, although probably in error.

Posted

• Might as well do a survey search while I'm at it:

SDSS J000529.22+011031.0

G=20.9 R=21.8 I=21.1

PhotoZ = 0.089 +/- 0.1297

SDSS J000956.96-095145.7

G=21.8 R=22.7 I=22.3

PhotoZ= not measured

SDSS J001738.66+112533.7

G=19.9 R=20.7 I=20.4

PhotoZ = not measured

Note: Probably a spectrally anomalous quasar (~70% certainty)

SDSS J002214.84-000337.1

G= 21.2 R=22.0 I=21.3

PhotoZ = not measured

part of GALEXASC J002615.32+102140.7

G=21.6 R=22.5 I=22.2

PhotoZ = 0.098 +/- 0.1123

GALEXASC J003210.80+304946.2

G=19.4 R=20.1 I=19.8

PhotoZ = 0.303 +/- 0.0597

Some kind of diffuse cloud to the lower left? Related?

part of SDSS J003359.16-005919.7

G=20.7 R=21.3 I=20.8

PhotoZ = 0.505 +/- 0.0834 (0.051683 +/- 0.000006 if part of SDSS J003359.16-005919.7)

SSTSL2 J003702.13+402443.9 (known emission object near Andromeda- MLA 23. although the paper does not identify what kind of object it is.)

G=20.6 R=21.3 I=21.1

PhotoZ = not measured

SDSS J003828.32-000009.7

G=19.5, R=19.9, I=19.9

PhotoZ = 0.244 +/- 0.1636

Looks more like a starburst galaxy with an OIII region than a true "blueberry"

GALEXASC J003850.67-074154.5

G=19.1 R=19.8 I=19.4

PhotoZ = not measured

SDSS J004230.90+272100.6

G=21.8 R=22.2 I=21.9

PhotoZ = not measured

SDSS J004539.12+114249.3

G=22.0 R=21.7 I=22.5

PhotoZ= 0.500 +/- 0.1616

Could totally be a voorwerpje or something like that, but that seems odd for such small (or distant) galaxies, which both have a photoZ of ~0.20.

SDSS J005022.57+133709.5

G=19.2 R=20.0 I=19.7

PhotoZ = not measured

Those are all the ones I could find below 1 hour of RA, so there's probably about ~24x as many undiscovered ones detectable by the same method.

Posted

• Another one I found previously:

RA/DEC 115.59650 +16.23559

Posted

• Some Pseudo-BBs (I'm not 100% sure these are actual ones):

SDSS J000008.68-003122.3

G=22.2 R=23.3 I=22.7

PhotoZ = not measured

SDSS J000011.13-070818.7

G=22.7 R=23.4 I=22.9

PhotoZ = not measured

SDSS J000023.30+010419.4

G=22.3 R=22.9 I=22.5

PhotoZ = 0.551 +/- 0.1269

part of SDSS J000026.08+055322.0

G=20.5 R=21.5 I=20.7

PhotoZ = 0.003 +/- 0.1425

part of SDSS J000037.29+341433.0

G=21.8 R=22.1 I=21.6

PhotoZ = 0.044 +/- 0.0228 (host galaxy)

part of GALEXASC J000101.16+022738.1

G=20.7 R=21.3 I=20.9

PhotoZ = 0.267 +/- 0.0823, 0.047 +/- 0.0373 (host galaxy)

SDSS J000138.30+154952.2

G=22.7 R=23.3 I=22.9

PhotoZ = 0.423 +/- 0.1224

SDSS J000143.37+212304.8

G=22.3 R=22.7 I=22.4

PhotoZ = 0.450 +/- 0.1235

SDSS J000249.41+334051.9

G=22.5 R=22.5 I=22.3

PhotoZ = 0.307 +/- 0.178

part of AGC 784777

G=21.6 R=23.3 I=23.0

Z = 0.046032 (host galaxy)

SDSS J000344.54+003040.7

G=22.1 R=22.6 I=22.4

PhotoZ = 0.211 +/- 0.0789

part of GALEXASC J000345.17+133606.6

G=20.7 R=21.7 I=21.2

PhotoZ = 0.026 +/- 0.022 (host galaxy)

Posted

• by c_cld

AGZ000dsgl RA = 179.598 Dec = 1.527527

Green Pea in KiDS-ESO-DR3 multi-band source catalogue and GAMA's master input catalogue

UV-luminous, detected in GALEX Object ID 6379113801155874579

Fflux 3.0896e+01 uJy FUV calibrated flux (fuv_flux)

Nflux 3.6102e+01 uJy NUV calibrated flux (nuv_flux)

GAMAJ115823.55+013139.0 CATAID = 219922

GAMA G12_Y1_DX1_211

Posted

• New paper on the Green Peas:

Kinematics and Optical Depth in the Green Peas: Suppressed Superwinds in Candidate LyC Emitters

Anne E. Jaskot, M. S. Oey, Claudia Scarlata, Tara Dowd

https://arxiv.org/abs/1711.09516

Very young 'extreme' GPs, less than a million years old, produce conditions with very slow velocities that give rise to 'catastrophic cooling scenarios'. The most massive stars produce pathways through the IGM by zapping it with intense radiation, rather than, say, supernovae exploding. The 13 'extreme Peas' were observed using the HST COS. The standard thinking, as used in Ricardo Amorin's study of 3 GPs (2012), is that in order for LyC photons to escape, pathways must be created through the galactic space by explosions and superwinds clearing the way. Jaskot et al reckon that's a good theory for most starburst galaxies, but with the extreme GPs, the internal movement of the galaxy is very slow, which does not agree with supernovae and superwinds. They conclude that the intense radiation given out by very massive stars drives a pathway through the galaxy. As the extreme GPs are so young, supernovae woukd not have had time to happen and the 'catastrophic cooling' suppresses any superwinds.

A useful paper on radiative cooling is:

The pressure confined wind of the massive and compact superstar cluster M82-A1 (2007)

Sergiy Silich, Guillermo Tenorio-Tagle, Casiana Munoz-Tunon

https://arxiv.org/abs/0707.2771

Posted

• SDSS J115448.85+244333.0

1237667550350672203

This is an extraordinary galaxy that is featured in a recent study by Yuri Izotov et al (published 2018). After observation with the Cosmic Origins Spectrograph aboard the Hubble Space Telescope, the team have discovered a galaxy with the most leakage of Lyman Continuum Photons in the local universe. After extremely thorough analysis, they present a figure of 46% leakage (the escape fraction). This is the biggest value found yet! Previous observations (Izotov 2016) of GPs give values of 6-13%, themselves breakthrough objects which doubled the number of LyC leakers detected in the local universe.

46% leakage of LyC photons is accompanied by the extraordinary value of 98% Lyman Alpha leakage. These values easily fulfill the criteria for the galaxies that were responsible for Reionisation at the start of the Universe, which are calculated to be 10-20% LyC leakage.

The SDSS spectrum is a classic GP one, with an equivalent width for [OIII] of 1121 Angstroms (112.1 nanometres) (from paper). Enormous! A great read which mentions GPs.

J1154+2443: a low-redshift compact star-forming galaxy with a 46 per cent leakage of Lyman continuum photons.

https://arxiv.org/abs/1711.11449

https://en.wikipedia.org/wiki/Reionization

https://en.wikipedia.org/wiki/Pea_galaxy#J0925+1403_and_LyC_Leakage (the first Izotov GP LyC leaker 2016)

Posted

• A study on the "Chemical abundances of a sample of coloured galaxies" has been published. The abstract states: "We obtain chemical abundances for a sample of 81 coloured galaxies very similar to known galaxies called as Green Peas. Our sample has mainly three different colours of galaxies, such as green, purple and blue. In this analysis we determine oxygen, neon, argon and sulphur abundances and found out the similarities in the results in the three colour groups, as well as striking differences." For collectors of different colours of Peas, this means that blue, purple or green examples are similar but different.

The authors also state that they don't know why this behaviour is so.

It concludes:" Although green peas have been compared with Lyman-break galaxies (Cardamone et al. (2009)) and with Luminous Compact Galaxies (Izotov, Guseva, and Thuan (2011)) based mainly on their physical properties like size, luminosity and colour, the chemical abundances was not considered. In particular, the abundances of other elements beyond Oxygen. Concerning such elements, it can be concluded that coloured galaxies are similar to normal, local irregular galaxies".

Chemical abundances of a sample of coloured galaxies

A.M. Hidalgo-Gámez, and B.E. Miranda-Pérez,