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SUR­VEY LED BY DURHAM UNI RE­VEALS THOU­SANDS OF GAL­AX­IES

The Chronicle - - News - By KALI LINDSAY kali.lindsay@reach­plc.com

ASTRONOMERS have dis­cov­ered thou­sands of pre­vi­ously un­seen gal­ax­ies scat­tered across space and time.

The im­age of the Abell 370 galaxy clus­ter and its sur­round­ings was pub­lished as part of the Durham Univer­sity-led Be­yond Ul­tra-deep Fron­tier Fields And Legacy Ob­ser­va­tions (BUF­FALO) sur­vey.

BUF­FALO, led by Durham and the Niels Bohr In­sti­tute in Den­mark, is a new sur­vey of the NASA/ESA Hub­ble Space Tele­scope aimed at ex­pand­ing its view of largely un­charted re­gions of the uni­verse.

Sev­eral hun­dred gal­ax­ies can be seen in Abell 370, around four bil­lion light years from earth, which lies at the cen­tre of the new im­age.

Thou­sands of pre­vi­ously un­seen dis­tant gal­ax­ies ly­ing be­hind Abell 370 are also re­vealed in the im­age through an ef­fect called grav­i­ta­tional lens­ing.

The im­mense mass of galaxy clus­ters like Abell 370, mainly com­posed of the mys­te­ri­ous dark mat­ter, bends and mag­ni­fies the light of th­ese far­away objects, turn­ing th­ese clus­ters into nat­u­ral telescopes.

This grav­i­ta­tional lens­ing ef­fect al­lows sci­en­tists to see fur­ther into space be­yond the clus­ter, by cap­tur­ing the light emit­ted by very dis­tant and faint objects.

The most stun­ning demon­stra­tion of grav­i­ta­tional lens­ing in Abell 370 can be seen just be­low the cen­tre of the clus­ter. Nick­named “The Dragon”, this feature is a com­bi­na­tion of five grav­i­ta­tion­ally lensed images of the same spi­ral galaxy that lies be­yond the clus­ter.

Although Hub­ble has al­ready de­tected some of the uni­verse’s ear­li­est gal­ax­ies through its Fron­tier Fields pro­gramme, th­ese fields are rel­a­tively small and might not fully rep­re­sent the num­ber of early gal­ax­ies in the wider uni­verse.

BUF­FALO builds upon th­ese ob­ser­va­tions us­ing grav­i­ta­tional lens­ing, and will ex­pand the search area around the six Fron­tier Fields pre­vi­ously ob­served by Hub­ble.

Abell 370 is the first clus­ter to be ob­served.

BUF­FALO will in­ves­ti­gate how and when the most mas­sive and lu­mi­nous gal­ax­ies in the uni­verse formed and how they are linked to dark mat­ter as­sem­bly – the con­strain­ing ef­fects of which are an es­sen­tial fac­tor in how the uni­verse looks to­day.

The sur­vey will also learn more about the evo­lu­tion of lens­ing galaxy clus­ters and will give clues on the na­ture of dark mat­ter.

The first step is mak­ing a de­tailed dark mat­ter mass map of th­ese galaxy clus­ters in or­der to mea­sure ex­actly by how much the lensed gal­ax­ies are be­ing mag­ni­fied.

The pro­gramme will de­ter­mine how rapidly gal­ax­ies formed in the first 800 mil­lion years af­ter the Big Bang – paving the way for ob­ser­va­tions with the up­com­ing NASA/ ESA/CSA James Webb Space Tele­scope.

Dr Mathilde Jauzac, BUF­FALO joint lead, in Durham Univer­sity’s Cen­tre for Ex­tra­galac­tic As­tron­omy, said: “By ex­pand­ing the area that we map around each of th­ese clus­ters, we will sig­nif­i­cantly im­prove our es­ti­mate of the clus­ters’ mag­ni­fi­ca­tion, a manda­tory step for study­ing the dis­tant gal­ax­ies that BUF­FALO will dis­cover.

“Plus, BUF­FALO will al­low us to map pre­cisely the dis­tri­bu­tion of dark mat­ter in th­ese mas­sive clus­ters, and thus trace their evo­lu­tion­ary his­tory, a miss­ing piece of in­for­ma­tion in to­day’s evo­lu­tion the­o­ries.

“BUF­FALO rep­re­sents an amaz­ing op­por­tu­nity to un­der­stand how dark mat­ter as­sem­bles, in­ter­acts, and evolves in the most mas­sive struc­tures present in our uni­verse.”

As well as us­ing Hub­ble, BUF­FALO will also use ob­ser­va­tions from other telescopes, in­clud­ing the Spitzer Space Tele­scope ob­ser­va­tions that al­ready ex­ist around th­ese clus­ters.

Sev­eral hun­dred gal­ax­ies can be seen in Abell 370, lo­cated about four bil­lion light years from Earth, which lies at the cen­tre of the new im­age. Thou­sands of more pre­vi­ously un­seen dis­tant gal­ax­ies ly­ing be­hind Abell 370 are also re­vealed in the im­age through an ef­fect called grav­i­ta­tional lens­ing. Re­porter Durham Univer­sity is lead­ing the BUF­FALO sur­vey

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