Author Topic: Discussion: Green Peas: A Class of Compact Extremely Star-Forming Galaxies  (Read 24949 times)

Rick Nowell

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Some of them might actually look green if we were sitting next to one
So I guess they're greeny-blue with a bit of red. A friend, who is doing a physics degree, said after
reading the paper and hearing about the time given at the ESO, "why only five days? This is important!"

waveney

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A Peas question:

The paper shows they Peas are isolated from dense clusters of galaxies.  Is this real, or a consequence of the selection criteria for the SDSS to take the spectra?  If a Pea was in a cluster, would the SDSS have chosen it for a spectra?  Or is it more likely to have chosen other larger galaxies?
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Galaxy Hunters Inc

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I know this is an old topic, but has anyone speculated as to the kind of stars being formed? Being formed in this unusual enviroment would they be somthing a bit different as well?

c_cld

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Re: Discussion: Green Peas: A Class of Compact Extremely Star-Forming Galaxies
« Reply #33 on: January 22, 2011, 10:08:48 am »
I know this is an old topic, but has anyone speculated as to the kind of stars being formed? Being formed in this unusual enviroment would they be somthing a bit different as well?

As green peas are a kind of starburst compact dwarf galaxies, and with the conclusion of Izotov paper
Quote from:  Izotov
Star formation in LCGs at the rate derived from Ha emission cannot be continuous, but rather must occur in strong short bursts separated by long quiescent phases, just as in BCDs. The bursting nature of star formation is more pronounced in LCGs with higher EW(Hb) and lower masses.

and the fact that all 80 green peas (cardamone's list) but 4, are in DR8 spectroscopy class "GALAXY" and subclass "STARBURST",

I'm guessing that stars could be

O and B blue hot stars,  (cited in literature ) , in a close-by BCD (blue compact dwarf) UGC 05720 .

1237657611797594121  UGC 5720 z=0.0048





May be a zookeeper would kindly comment/answer this question ?

c_cld

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Re: Discussion: Green Peas: A Class of Compact Extremely Star-Forming Galaxies
« Reply #34 on: January 22, 2011, 07:28:35 pm »
Another puzzle for having coherent "type" matches between catalogs/data sources of information:

When you query NED for Cardamone's paper with the search NED results for object(s) in publication "2009MNRAS.399.1191C" you Retrieve 61 NED objects in this reference.

Of these 61 peas there are four in object type "QSO" seventeen in "*" and forty in "G".

In DR8, I found phototype, objtype(type of object targeted as) , Spectroscopic class (GALAXY, QSO, or STAR), Spectroscopic subclass.
Not all peas are  "Galaxy" in class "Galaxy / Starburst"  and here is a sample of other types:

IAUname,Object type in NED,urlobjid,PhotoType,objtype,class,subclass
SDSS J140740.08+021748.1,QSO, 1237651754024304896 ,GALAXY,SERENDIPITY_FIRST,QSO,AGN BROADLINE
SDSS J162209.42+352107.4,QSO, 1237659119871525118 ,GALAXY,QSO,GALAXY,AGN
SDSS J141918.90+510240.1,QSO, 1237659132208087323,GALAXY,SERENDIPITY_FIRST,QSO,AGN BROADLINE
SDSS J112615.25+385817.4,QSO, 1237662224599810234 ,STAR,QSO,QSO,AGN BROADLINE
SDSS J082651.80+182051.8,*, 1237667142324191658 ,STAR,SERENDIPITY_DISTANT,GALAXY,STARBURST
SDSS J092249.26+191339.4,*, 1237667486994137370,STAR,SERENDIPITY_DISTANT,GALAXY,STARBURST



How could you manage easily with this kind of difficulties?   ???

 ::)

c_cld

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Re: Discussion: Green Peas: A Class of Compact Extremely Star-Forming Galaxies
« Reply #35 on: February 01, 2012, 12:33:17 pm »
Quote from: Roderik Overzier
arXiv:0910.1352v1 7 Oct 2009  Local Lyman Break Galaxy Analogs: The Impact of Massive Star-forming Clumps on the Interstellar Medium and the Global Structure of Young, Forming Galaxies
We present HST UV/optical imaging, Spitzer mid-IR photometry, and optical spectroscopy of a sample of 30 low-redshift (z=0.1-0.3) galaxies chosen from SDSS/GALEX to be accurate local analogs of the high-z Lyman Break Galaxies. The Lyman Break Analogs (LBAs) are similar in mass, metallicity, dust, SFR, size and gas velocity dispersion, thus enabling a detailed investigation of processes that are important at high-z. The optical emission line properties of LBAs are also similar to those of LBGs, indicating comparable conditions in their ISM. In the UV, LBAs are characterized by complexes of massive star-forming "clumps", while in the optical they most often show evidence for (post-)mergers/interactions. In 6 cases, we find an extremely massive (>10^9 Msun) compact (R~100 pc) dominant central object (DCO). The DCOs are preferentially found in LBAs with the highest mid-IR luminosities and correspondingly high SFRs (15-100 Msun/yr). We show that the massive SF clumps (including the DCOs) have masses much larger than the nuclear super star clusters seen in normal late type galaxies. However, the DCOs have masses, sizes, and densities similar to the excess-light/central-cusps seen in typical elliptical galaxies with masses similar to the LBA galaxies. We suggest that the DCOs form in present-day examples of the dissipative mergers at high redshift that are believed to have produced the central-cusps in local ellipticals. More generally, the properties of the LBAs are consistent with the idea that instabilities in a gas-rich disk lead to very massive star-forming clumps that eventually coalesce to form a spheroid. We speculate that the DCOs are too young at present to be growing a supermassive black hole because they are still in a supernova-dominated outflow phase.

It is to be noticed that 4 peas are in the Overzier's sample.
587724199349387411 1237649920574292233
587731187273892048 1237663462607552754
588013384341913605 1237657630590107652
587729155743875234 1237651067351073064
The HST imaging studied by Ovizier's paper are cited for 3 of them in Cardamone's paper.
The last one DR7 587729155743875234 / DR8 1237651067351073064  is in the peas list but not cited by Carie as HST imaging .

The part II following this paper is referenced in Wikipedia page "Pea Galaxy"  ;D

Rick Nowell

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Re: Discussion: Green Peas: A Class of Compact Extremely Star-Forming Galaxies
« Reply #36 on: February 01, 2012, 02:52:54 pm »
On page 7 (fig.7) of the original Cardamone paper, there is a picture of six objects (Peas).
Five have some definition. Table 2 is this:
http://arxiv.org/pdf/0907.4155v1.pdf
587729155743875234        1237651067351073064 is not present.

Table 2. HST Images
SDSS Obj ID                  RA (J2000) Dec(J2000)           z              Instrument Chip Filter Exposure Time (s) Figure location
587731187273892048 351.41345  0.75201             0.2770      WFPC2 PC F606W 3600 top left
588013384341913605 141.50168  44.46004           0.1807      ACS WF F850LP 2274 top centre
587724199349387411 10.22636    15.56935           0.2832      WFPC2 PC F606W 3600 top right
587726879424118904 344.49532  -8.62438            0.3081      ACS WF clear 1071 bottom left
587726032799400204 211.91701   2.29671             .3092      WFPC2 WF4 F814W 1200 bottom centre

Interesting. Of course as many Hubble images of Peas that can be found is beneficial. Do you know
which picture it is please in the Overzier paper 'The Impact of Massive Star-forming Clumps'?

Rick Nowell

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Re: Discussion: Green Peas: A Class of Compact Extremely Star-Forming Galaxies
« Reply #37 on: February 01, 2012, 03:17:53 pm »
Do you know which picture it is please in the Overzier paper 'The Impact of Massive Star-forming Clumps'?

I think     Dr7 587729155743875234    Dr8 1237651067351073064   is 113303  (Fig.1 page 4) in the above paper.


c_cld

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Re: Discussion: Green Peas: A Class of Compact Extremely Star-Forming Galaxies
« Reply #38 on: February 01, 2012, 03:21:11 pm »
The HST imaging pea in Overzier's paper (missing in Carie's) is
113303 (named with RA)

c_cld

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Re: Discussion: Green Peas: A Class of Compact Extremely Star-Forming Galaxies
« Reply #39 on: February 01, 2012, 04:05:15 pm »
studied also in following paper
arXiv:1009.4934v1 24 Sep 2010 The kinematics of ionized gas in Lyman-Break Analogs at z ~ 0.2
092600 : 588013384341913605 
113303 : 587729155743875234

Quote from: Thiago S. Gonçalves, Antara Basu-Zych, Roderik Overzier et all
3.11. 092600 This is another example of an LBA with a companion structure, also evident in the HST image. The companion presents a ~50 km s-1 shift with respect to the main structure. Also evident is a velocity shear across the main region itself, albeit small { ~50 km s-1 { especially when compared to the velocity dispersion of approximately ~100 km s-1 found in the galaxy. This is the least massive of our objects (log M*/Msol = 9.1) and has also been described in Basu-Zych et al. (2009a).

3.14. 113303 This galaxy shows a remarkable lack of velocity structure within the main component, with a shear of a few tens of km s-1, comparable to the instrument resolution itself. However, we were able to detect some faint emission from a component to the southwest, offset from the main region at approximately 100 km s-1.

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Re: Discussion: Green Peas: A Class of Compact Extremely Star-Forming Galaxies
« Reply #40 on: February 15, 2012, 09:27:40 pm »
There is a new paper on the chemical composition of the gas in the Green Peas, which does not seem to have been posted to arxiv.org - oddly enough in this day and age, I first saw it in the paper journal. It's by Steve Hawley, better known as one of the astronauts who deployed Hubble on STS-31 back in 1990, serviced it during STS-82, and helped deploy Chandra on STS-93 in 1999. His graduate training was in emission-line astrophysics and abundances (under the same thesis advisor, I might note to bask in reflected glory), so he's kind of returning to his scientific roots. 

Anyway, he considers such details as the contribution of Wolf-Rayet stars to the gas ionization, and which sets of emission lines give the most accurate results for these galaxies, resolving some earlier discrepancies. He uses a lot of abbreviations for various sets of emission-line ratios, which does make it slightly slow going.

Edit to add: Rick Nowell found this link to the paper text.

Abundances in ""Green Pea"" Star-forming Galaxies

Quote
He II λ4686 is identified in the spectra of nine of the original ""Green Peas,"" a type of compact star-forming galaxy characterized by low mass; low metallicity; strong [O III] λλ4959, 5007; and redshifts in the range of ˜0.1-0.4. Measured λ4686/Hβ ratios are roughly 1--2%, consistent with photoionization by Wolf-Rayet stars. Emission-line intensities are measured from Sloan Digital Sky Survey spectra for 71 Green Peas and are used to determine Te-based abundances of O, N, Ne, S, and He. Neon abundances confirm the mass-metallicity relation inferred from O/H. The N/O ratio is roughly constant with O/H, and the average N/O is evidence of a modest nitrogen enhancement compared with other low-metallicity galaxies. Nitrogen enrichment could be due to Wolf-Rayet stars or to intermediate-mass stars during a previous quiescent period. The Teformula>-based abundances allow a reevaluation of some of the strong-line methods favored for estimating O/H or N/O in large spectroscopic surveys of star-forming galaxies. Photoionization by Wolf-Rayet stars raises questions about the validity of strong-line methods based on [N II]/Hα, [N II]/[O III], or [N II]/[S II], as those line ratios are known to be ionization-sensitive. Analysis of these measurements shows that ionization, low metallicity, and the small variation in important line ratios in the Green Pea spectra all affect the behavior of one or more of the N2, O3N2, N2O2 and N2S2 strong-line methods. The previous findings for trends in O/H and N/O in the Green Peas can be reproduced and the discrepancies can be explained. In particular, the reported increase of N/O with O/H appears to be a bias introduced by combining N2 with N2S2. N2O2 does not give valid results in the Green Peas, while N2 and N2S2 do, although the calibrations of the N2 and N2S2 methods based on Green Pea abundances are different from the existing calibrations based primarily on abundances in extragalactic H II regions and H II galaxies.
« Last Edit: February 16, 2012, 01:35:05 pm by NGC3314 »

Rick Nowell

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Re: Discussion: Green Peas: A Class of Compact Extremely Star-Forming Galaxies
« Reply #41 on: February 15, 2012, 11:33:19 pm »
Anyway, he considers such details as the contribution of Wolf-Rayet stars to the gas ionization, and which sets of emission lines give the most accurate results for these galaxies, resolving some earlier discrepancies. He uses a lot of abbreviations for various sets of emission-line ratios, which does make it slightly slow going. (Well, that plus the full text not being freely available yet).
Thanks for the link. Uncanny, weird even, that I posted a link to the WolfRayet galaxy thread in today's OOTD.

zutopian

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Re: Discussion: Green Peas: A Class of Compact Extremely Star-Forming Galaxies
« Reply #42 on: February 16, 2012, 07:28:55 am »
Here is another new paper, which seems to be similiar to the other new paper:

"The star formation history and metal content of the "Green Peas". New detailed GTC-OSIRIS spectrophotometry of three galaxies"
Authors: Ricardo Amorín, E. Pérez-Montero, J. M. Vílchez, P. Papaderos
Quote
We present deep broad-band imaging and long-slit spectroscopy of three compact, low-mass starburst galaxies at redshift z\sim0.2-0.3, also referred to as Green Peas (GP). We measure physical properties of the ionized gas and derive abundances for several species with high precision. We find that the three GPs display relatively low extinction, low oxygen abundances, and remarkably high N/O ratios We also report on the detection of clear signatures of Wolf-Rayet (WR) stars in these galaxies. We carry out a pilot spectral synthesis study using a combination of both population and evolutionary synthesis models. Their outputs are in qualitative agreement, strongly suggesting a formation history dominated by starbursts. In agreement with the presence of WR stars, these models show that these GPs currently undergo a major starburst producing between ~4% and ~20% of their stellar mass. However, as models imply, they are old galaxies having had formed most of their stellar mass several Gyr ago. The presence of old stars has been spectroscopically verified in one of the galaxies by the detection of Mg I 5167, 5173 absorption line. Additionally, we perform a surface photometry study based on HST data, that indicates that the three galaxies posses an exponential low-surface brightness envelope. If due to stellar emission, the latter is structurally compatible to the evolved hosts of luminous BCD/HII galaxies, suggesting that GPs are identifiable with major episodes in the assembly history of local BCDs. These conclusions highlight the importance of these objects as laboratories for studying galaxy evolution at late cosmic epochs.
(Submitted on 15 Feb 2012)
http://arxiv.org/abs/1202.3419
« Last Edit: February 16, 2012, 07:32:31 am by zutopian »

Rick Nowell

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Re: Discussion: Green Peas: A Class of Compact Extremely Star-Forming Galaxies
« Reply #43 on: February 16, 2012, 01:19:37 pm »
There is a new paper on the chemical composition of the gas in the Green Peas, which does not seem to have been posted to arxiv.org - oddly enough in this day and age, I first saw it in the paper journal. It's by Steve Hawley, better known as one of the astronauts who deployed Hubble on STS-31 back in 1990, serviced it during STS-82, and helped deploy Chandra on STS-93 in 1999. His graduate training was in emission-line astrophysics and abundances (under the same thesis advisor, I might note to bask in reflected glory), so he's kind of returning to his scientific roots.  Anyway, he considers such details as the contribution of Wolf-Rayet stars to the gas ionization, and which sets of emission lines give the most accurate results for these galaxies, resolving some earlier discrepancies. He uses a lot of abbreviations for various sets of emission-line ratios, which does make it slightly slow going.

Available at:   http://www.physics.ku.edu/~physics/momentum/pdfs/hawleys.pdf

Rick Nowell

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Re: Discussion: Green Peas: A Class of Compact Extremely Star-Forming Galaxies
« Reply #44 on: February 22, 2012, 07:28:50 pm »
There is a new paper on the chemical composition of the gas in the Green Peas, which does not seem to have been posted to arxiv.org - oddly enough in this day and age, I first saw it in the paper journal. It's by Steve Hawley, better known as one of the astronauts who deployed Hubble on STS-31 back in 1990, serviced it during STS-82, and helped deploy Chandra on STS-93 in 1999. His graduate training was in emission-line astrophysics and abundances (under the same thesis advisor, I might note to bask in reflected glory), so he's kind of returning to his scientific roots.  Anyway, he considers such details as the contribution of Wolf-Rayet stars to the gas ionization, and which sets of emission lines give the most accurate results for these galaxies, resolving some earlier discrepancies. He uses a lot of abbreviations for various sets of emission-line ratios, which does make it slightly slow going.
Available at:   http://www.physics.ku.edu/~physics/momentum/pdfs/hawleys.pdf

I took the chance of contacting former astronaut Prof. Steve Hawley with an exchange of emails. I informed him of the above link,
just to be sure. To quote from his emails:  "I'm pleased to be considered part of the Green Pea team."

http://www2.ku.edu/~physics/vita/hawley.shtml