Most distant gamma ray blast seen

[Martin]

http://news.bbc.co.uk/2/hi/science/nature/4237800.stm

 

Most distant cosmic blast sighted

 

"Astronomers have witnessed the most distant cosmic explosion on record: a gamma-ray burst that has come from the edge of the visible Universe.

Gamma-ray bursts are intense flares of high-energy radiation that appear without warning from across the cosmos.

 

They can release as much energy in a few minutes as our Sun will emit in its expected 10-billion-year lifetime.

 

The blast was observed by the Swift space telescope and by a number of ground-based observatories.

 

The latest, record gamma-ray burst was detected on 4 September, 2005, and lasted about three minutes. It probably marked the death of a massive star as it collapsed into a black hole.

 

It has a so-called redshift of 6.29, which translates to a distance of about 13 billion light-years from Earth.

 

Used by astronomers to measure cosmic distances, redshift refers to the extent to which light is shifted towards the red part of the electromagnetic spectrum during its long journey across the Universe. The greater the distance, the higher the redshift.

 

Record distance

 

"This burst smashes the old distance record by 500 million light-years," said Dr Daniel Reichart, of the University of North Carolina, US, who has been leading the measurement of its distance..."

[Martin]

http://news.bbc.co.uk/2/hi/science/nature/4237800.stm

 

"Most distant cosmic blast sighted

 

...It has a so-called redshift of 6.29' date=' which translates to a distance of about 13 billion light-years from Earth..."

[/quote']

 

let's check the distance the BBC gives, using Morgan's calculator, the link is post #5 of the Astronomy Reference thread

http://scienceforums.net/forums/showthread.php?p=56565#post56565

 

Here are two good online cosmology calculators

 

Siobahn Morgan's

http://www.earth.uni.edu/~morgan/ajjar/Cosmology/cosmos.html

 

and Ned Wright's

http://www.astro.ucla.edu/~wright/CosmoCalc.html

 

homepages for Morgan

http://www.earth.uni.edu/smm.html

and Wright

http://www.astro.ucla.edu/~wright/intro.html

 

To use Siobahn's calculator put Lambda = 0.73

Omega = 0.27

H = 71 (or leave her default value of H = 70, nearly the same)

those are the dark energy and the matter densities as fractions of rho crit,

and H is the present value of the Hubble parameter

 

then put in any redshift z,

like z =1 or 3 or 10 and it will tell you how far away the thing

was when it emitted the light we are now getting from it

and how far away it is now

and how fast it was receding then

and how fast it is receding now, at the present moment

 

in this case, after putting in cosmological constant Lambda 0.73 and matter fraction Omega 0.27 and Hubble parameter 71, what gets put in for z is 6.29. Let's see

[Martin]

the result is that the burst occurred 12.77 billion years ago

 

at a time when the source object was moving away from our galaxy's location at a speed of 2.84 times the speed of light

 

the distance then was 3.82 billion LY

and the age of the universe at that moment when the gammaray burst was emitted was 0.89 billion years

 

these are numbers which the calculator gives you for the reported redshift z = 6.29

 

it also gives the present distance (27.87 billion LY) and current recession speed (2.02 times c)

 

===================

 

the numbers that one of these cosmology calculators gives you can be rounded, because the data like Omega and Lambda is not known precisely. So what I found was that Morgan calculator says the same number as the BBC---namely the blast of gamma was emitted 13 billion years ago.

 

the redshift 6.29 means that space has expanded by factor of 7.29 while the blast was traveling. so it is not very meaningful to say (as journalists tend to) that the light "traveled 13 billion LY".

 

the actual path it traveled, from the collapsing star to us, has been stretched out to 27.87 billion LY.

 

but anyway the blast did happen 13 billion years ago. (let's forget about the length of the path the light traveled, it is too much unnecessary complication with the universe expanding so much while it was on its way)

[J.C.MacSwell]

Gamma bursts... redshifted 6.29?.... ....

 

 

Oops, that was my son with his little flashlight, I told him not to shine it at the scientists while they are working.

 

 

Just kidding!

[Martin]

Gamma bursts... redshifted 6.29?.... ....

...

 

yeah! it is really great, JC. I think there are only a handful of things known with such a large redshift.

 

The CMB redshift is estimated around 1100, but that is different

[Martin]

just saw the article in Nature about it:

http://www.nature.com/news/2005/050912/full/050912-3.html

[Skye]

What would be the minimum time it would have taken for the universe to produce such an event? I.e. the time it takes to go from big bang to a massive star evolving that would produce this kind of gamma ray burst.

[Martin]

What would be the minimum time it would have taken for the universe to produce such an event? I.e. the time it takes to go from big bang to a massive star evolving that would produce this kind of gamma ray burst.

 

 

that is the big question isnt it?

having this (and subsequent, perhaps older bursts) will help them get their model of early universe star formation right

 

it is a message to us about the earliest stars

 

 

I am not knowledgeable about the current models of earlyuniverse star formation, so all I can do is keep an eye out and post some pointers. Also Skye or anyone else if you find anything relevant to that question please post a link.

 

I do know that the French astronomer Roser Pello and her team thought they had found a GALAXY at redshift 10 and they published. This was IIRC late 2003 or early 2004. And this was contested by other astronomers who argued among other things that z = 10 is way too old, too near the beginning, for a galaxy to have coalesced.

And eventually somebody discredited the Roser Pello observational data, I forget how. Sorry I'm vague about it. I think this is still a controversial area of discussion. Some people think that the first galaxies and stars could have collected as early as, say, 500 million years, and other people think not. It is hard to imagine how clouds of gas could contract when there are no other chemical elements besides H and He (almost). there are no larger molecules! no dust! how do the clouds radiate heat as they contract? well hydrogen can radiate off some heat but it is not so efficient. once there were SOME stars and SOME explosions and some other chemical elements and stuff like that then it begins to look more normal. shockwaves trigger formation of the next generation etc.

 

It is interesting but I dont think I can come up with a believeable number for when the earliest stars could have formed. maybe someone else can.

[Martin]

A followup on this was just posted in the past couple of days.

It confirms the redshift z=6.29, putting errorbounds at +/- 0.01

 

http://arxiv.org/abs/astro-ph/0509640

Outshining the quasars at reionisation: The X-ray spectrum and lightcurve of the redshift 6.29 Gamma-Ray Burst GRB050904[/b]

D. Watson (1), J. N. Reeves (2,3), J. Hjorth (1), J. P. U. Fynbo (1), P. Jakobsson (1), K. Pedersen (1), J. M. Castro Cerón (1), S. McBreen (4), S. Foley (5) ((1) DARK Copenhagen, (2) NASA-GSFC (3) USRA (4) ESA-ESTEC (5) University College Dublin)

Submitted to ApJL, 5 pages, 3 figures

"A gamma-ray burst (GRB) has finally been found with a redshift comparable to the most distant quasars and galaxies: GRB050904 at z=6.29+/-0.01, making it the most distant X-ray source known....

 

... GRB050904 was extraordinarily bright in X-rays. In the first days after the burst, it was by far the brightest known X-ray source at z>4. In the first minutes after the burst, the X-ray flux was >10^{-9} erg cm^-2 s^-1 in the 0.2--10 keV band, corresponding to an apparent luminosity between 10^5 and 10^6 times greater than the brightest X-ray quasars at similar distances. More photons were acquired in the first minutes with Swift-XRT than XMM-Newton and Chandra have obtained in ~300 ks of pointed observations of z>5 AGN. ..."

 

Skye, you raise an interesting question about early star formation. A GRB comes from a collapsing star. If we see a GRB as early (distant) as 6.29 then there must be stars that early. How soon after Bang did stars and galaxies form? what is known about this?

 

I'm not knowledgeable enough to summarize the situation or point to sources readily---maybe someone else knows a good site about the early universe and early star formation.

 

All I can do for the moment is pass on something that came my way recently that gives the flavor of current research

 

http://arxiv.org/abs/astro-ph/0509616

Spectroscopic Studies of z~5.7 and z~6.5 Galaxies: Implications for Reionization

Esther M. Hu (1), Lennox L. Cowie (1), Peter Capak (1,2), Yuko Kakazu (1) ((1) IfA, Univ. of Hawaii, (2) Presently at Caltech)

6 pages, 6 figures, to appear in IAU 199 Conf. Proc.: "Probing Galaxies through Quasar Absorption Lines," eds. Williams, Shu, Menard

 

"The recent development of large, complete samples which identify high-redshift galaxies at z~5.7 and z~6.5 from deep, wide-field surveys provides detailed information on the earliest galaxies, their numbers, spatial and kinematic distributions, and implications for early reionization of the IGM. In this contribution we present results of spectroscopic studies of z~5.7 and z~6.5 galaxies identified from our deep, Lyman alpha narrowband and multicolor surveys conducted with the SuprimeCam mosaic CCD camera on the 8.3-m Subaru telescope and observed with the DEIMOS multi-object spectrograph on Keck. The luminosity function of the z~6.5 galaxies is shown to be similar to the luminosity function of the z~5.7 galaxy samples, suggesting that a substantial star-forming population is already in place at z~6.5. Comparisons of both individual and stacked spectra of galaxies in these two samples show that the Lyman alpha emission profiles, equivalent widths, and continuum break strengths do not substantially change over this redshift interval. The wide-field nature of the surveys also permits mapping the large-scale distribution of the high-redshift galaxies in spatial structures extending across individual SuprimeCam fields (~60 Mpc). Field-to-field variations in the number of objects at z~6.5 may shortly be able to place constraints on the porosity of the reionization boundary."

 

=====my summary====

"Current investigations use approx. 120 A bandpass filters centered at 8150 A and 9130 A (Ly alpha at z approx 5.7 and z approx 6.5) for the narrowband studies, with follow-up DEIMOS spectra (3.6 A resolution, R approx 2700) at Keck. "

 

ALL THEY SEEM TO BE DOING IS LOOKING AT LYMAN ALPHA LIGHT stretched out BY RATIOS OF 6.7 AND 7.5 which ratios THEY CHOOSE IN ADVANCE BY WHAT FILTER THEY USE. And they have some clever data processing HOOKED TO THE CCD so that they can collect and analyse data over a WIDE FIELD of these hundreds of tiny points of shifted Lyman Alpha light.

 

So if the experts are only just now constructing a adequate picture of the galaxies back that far in time. My inclination is to be laid back and not worry about it. Somehow it seems stars and galaxies did form in what seems like a hurry-----within the first billion years after the Bang. But probably the experts don't yet understand how that happened and if we wait patiently we will hear more about it.

 

In other words Skye I'm afraid all I can say is Duh. Would be delighted to hear something more alert about this, if anyone knows anything.

[Martin]

What would be the minimum time it would have taken for the universe to produce such an event? I.e. the time it takes to go from big bang to a massive star evolving that would produce this kind of gamma ray burst.

 

Oh, one thing. Massive stars, really massive stars, have very short lifetimes. On the order of a million years IIRC. so there is no problem with the time it takes for the star to burn down to where it can collapse and produce a GRB.

the interesting thing is how early can stars start to condense in the first place. I think once you have any massive stars at all, you can begin to have GammaRay Bursts almost immediately after

 

I used Morgan's calculator back in post #2 and #3 to get that at z=6.29 the burst occurred when the universe was

0.9 billion years old.

 

big stars formed after only 900 million years

that is the hard thing that we just bit on

nothing helpful to say

[Martin]

no rest for the wicked

recently posted paper gives evidence that star formation could have occurred as early as z=15

this is hard to put up with. it has been accepted for publication in Astrophysical Letters and rumor says people in the astrophysics coffeeroom at Princeton find it credible.

http://arxiv.org/abs/astro-ph/0509605

Direct evidence for an early reionization of the Universe?

N. Panagia (1), S.M. Fall (2), B. Mobasher (1), M. Dickinson (3), H.C. Ferguson (2), M. Giavalisco (2), D. Stern (4), T. Wiklind (1) ((1) ESA/STScI, (2) STScI, (3) NOAO/Tucson, (4) JPL)

6 pages, 2 figures. Accepted for publication in ApJ Letters

 

"We examine the possible reionization of the intergalactic medium (IGM) by the source UDF033238.7-274839.8 (hereafter HUDF-JD2), which was discovered in deep HST/VLT/ Spitzer images obtained as part of the Great Observatory Origins Deep Survey and Hubble Ultra-Deep Field projects. Mobasher et al (2005) have identified HUDF-JD2 as a massive

([math]\sim6\times10^{11}M_\odot[/math])

post-starburst galaxy at redshift z[math]\gtrsim6.5[/math].

We find that HUDF-JD2 may be capable of reionizing its surrounding region of the Universe, starting the process at a redshift as high as z [math]\approx 15 \pm 5[/math]"

 

sample quote from page 2

 

"On the other hand, the presence of a clear Balmer break in the observed SED of the HUDF-JD2 solidifies its high redshift identification and reveals a post-starburst population. From their best-fit models, Mobasher et al. (2005) derive a photometric redshift of z approx 6.5 and a bolometric luminosity of L_bol = 1 x 10^12 L_solar (for a cosmology with H_0 = 70 km/s per Mpc, Omega_matter = 0.3 and Omega_Lambda = 0.7). ... The strong Balmer break displayed by HUDF-JD2 requires that its SED be dominated by stars of spectral types A0 or later, i.e. main-sequence stars with masses less than approx 3 solar masses (e.g., Allen 1973). This fact unambiguously indicates a rather old age (greater than 300 Myr) for the stellar population of HUDF-JD2. Mobasher et al. (2005) conclude that the stars were formed at z greater than 9 (i.e. an age of the Universe less than 540 Myr), and possibly as high as z about 12-20, so that most of the stars were in place when the Universe was only about 200 - 400 Myr old. Moreover, their model fitting indicates that HUDF-JD2 formed the bulk of its stars very rapidly, on time scales less than or equal to 100 Myr, and the subsequent evolution was essentially passive. A stringent upper limit to the starburst age is set by the photometric redshift z about 6.5 of HUDF-JD2, which corresponds to a time when the Universe was only 830 Myr old. Adopting this prior, the model fitting procedure indicates that the age of the stellar population in HUDF-JD2 is likely to be bracketed between 350 and 650 Myr. These ages correspond to redshifts of galaxy formation between 10 and 20. "

[Martin]

another followup on this GRB at redshift z = 6.29

 

http://www.arxiv.org/abs/astro-ph/0509737

Detection of a huge explosion in the early Universe

 

Authors: G. Cusumano, V. Mangano, G. Chincarini, A. Panaitescu, D.N. Burows, V. La Parola, T. Sakamoto, S. Campana, T. Mineo, G. Tagliaferri, L. Angelini, S.D. Barthelemy, A.P. Beardmore, P.T. Boyd, L. Cominsky, C. Gronwall, E.E. Fenimore, N. Gehrels, P. Giommi, M. Goad, K. Hurley, J.A. Kennea, K.O. Mason, F. Marshall, P. Meszaros, J.A. Nousek, J.P. Osborne, D.M. Palmer, P.W.A. Roming, A. Wells, N.E. White, B. Zhang

Categories: astro-ph

Comments: 11 pages, 1 table, 3 figures. Note: this paper has been submitted for publication in Nature, It is embargoed for discussion in the popular press

 

"Gamma-ray Bursts (GRBs) are bright flashes of high energy photons that can last from about 10 milliseconds to 10 minutes. Their origin and nature have puzzled the scientific community for about 25 years until 1997, when the first X-ray afterglows of long (> 2 s duration) bursts were detected and the first optical and radio counterparts were found. These measurements established that long GRBs are typically at high redshift (z 1.6) and are in sub-luminous star-forming host galaxies. They are likely produced in core-collapse explosions of a class of massive stars that give rise to highly relativistic jets (collapsar model). Internal inhomogeneities in the velocity field of the relativistic expanding flow lead to collisions between fast moving and slow moving fluid shells and to the formation of internal shock waves. These shocks are believed to produce the observed prompt emission in the form of irregularly shaped and spaced pulses of gamma-rays, each pulse corresponding to a distinct internal collision. The expansion of the jet outward into the circumstellar medium is believed to give rise to ``external'' shocks, responsible for producing the smoothly fading afterglow emission seen in the X-ray, optical and radio bands. Here we report on the gamma-ray and x-ray observation of the most distant gamma-ray burst ever observed: its redshift of 6.29 translates to a distance of 13 billion light-years from Earth, corresponding to a time when the Universe was just 700 million to 750 million years old. The discovery of a gamma-ray burst at such a large redshift implies the presence of massive stars only 700 million years after the Big Bang. The very high redshift bursts represent a good way to study the re-ionization era soon after the Universe came out of the Dark Ages."

 

several groups seem to be getting into the act on this one