Pressemeddelelse

Galaksefodring fanget i det fjerne søgelys

ESOs Very Large Telescope kortlægger galaksers vækst

4. juli 2013

Astronomer har brugt ESOs Very Large Telescope, og fundet en fjern galakse, der glubsk 'spiser' af de nærliggende galakser. Det kan ses, at gassen falder ind mod galaksen, og skaber en strøm der sætter gang i stjernedannelse samtidig med at det driver galaksens rotation. Dette er det hidtil bedste direkte observationelle bevis, der støtter teorien om at galakser indfanger og fortager nærliggende materiale for at vokse sig større og danne stjerner. Resultaterne kan ses d. 5. juli 2013 i den videnskabelige journal Science.

Astronomer har altid haft en formodning om, at galakser vokser ved at indfange materiale fra deres omgivelser, men denne proces har vist sig at være svær at observere direkte. Nu er ESOs Very Large Telescope, blevet brugt til at undersøge en meget sjælden opstilling mellem en fjern galakse [1] og en endnu fjernere kvasar - galaksens centrum lyser ekstremt kraftigt grundet et supertungt sort hul. Lyset fra kvasaren går igennem materialet, der ligger omkring galaksen før det når til Jorden, hvilket gør det muligt at undersøge gassen omkring galaksen meget detaljeret [2]. Disse nye resultater giver det hidtil bedste udsyn af en galakse, der er i gang med at fodre sig selv.

"Denne type opstilling er meget sjælden, og har gjort det muligt for os, at gøre unikke observationer," forklarer Nicolas Bouché fra Research Institute in Astrophysics and Planetology (IRAP) i Toulouse, Frankrig, der er artiklens hovedforfatter. "Vi var i stand til at bruge ESOs Very Large Telescope til at kigge ind i selve galaksen og det omkringliggende gas. Dette betød, at vi kunne angribe et stort problem i teorien om galaksedannelse: Hvordan galakser vokser og tilfører materiale til stjernedannelse?"

Galakser udtømmer hurtigt dages gaslager, når de danner nye stjerner, og derfor må de hele tiden få 'friskt' gas for at opretholde stjernedannelsen. Astronomer har formodet, at svaret til dette spørgsmål lå i indsamlingen af koldt gas fra galaksens omgivelser, der blev tiltrukket af tyngdekraften. Her vil galaksen hive gas mod sig, der så vil cirkle rundt om galaksen, og roterer sammen med den før det falder ind. Selvom der tegn på dette indfald var blevet observeret i galakse førhen, har gassernes bevægelse og andre egenskaber ikke været undersøgt til fulde før nu.

Astronomerne brugte to instrumenter kaldet SINFONI og UVES [3], der begge er monteret på ESOs VLT på Paranal-observatoriet i det nordlige Chile. De nye observationer viste dem både hvordan galaksen selv roterede, og afslørede sammensætningen og bevægelsen af gassen udenom galaksen.

"Egenskaberne af denne store mængde omkringliggende gas, var lige præcis hvad vi forventede at finde, hvis koldt gas bliver tiltrukket af galaksen," siger medforfatter Michael Murphy (Swinburne University of Technology, Melbourne, Australia). "Gassen bevæger sig som forventet, der er omkring den forventede mængde, og det har også den rigtige sammensætning for at passe perfekt ind i modellerne. De er ligesom fodringtid for løverne i Zoo - denne galakse har en særlig glubsk appetit, og vi har fundet ud af, hvordan den fodrer sig selv for at vokse så hurtigt."

Astronomerne har allerede fundet bevis for, at der lå materiale omkring galakserne i det tidlige univers, men det er første gang at de har været i stand til klart at vise, hvordan materiale bevæger sig imod og ikke væk fra galaksen, og også hvad sammensætningen af dette friske brændstof der bruges af fremtidens generation af stjerner. Uden kvasarens lys der virker som en sonde, ville man ikke kunne opdage det omkringliggende gas.

"I dette tilfælde var vi heldige at kvasaren lå lige det rigtige sted, så dens lys kunne passere igennem det indfaldne gas. Den næste generation af ekstremt store teleskoper vil gøre det muligt at studere flere synslinjer for hver galakse og give en meget mere færdigt udsyn," konkluderer medforfatter Crystal Martin (University of California Santa Barbara, USA).

Noter

[1] Denne galakse blev i rødforskydning ~ 2 kortlægningsprojektet SINIFONI Mg II Program for Line Emitters (SIMPLE). Kvasaren i baggrunden hedder HE 2243-60, og galaksen ligger selv i rødforskydningen 2,3285 - hvilket betyder, at vi ser galaksen som den så ud, da universet blot var omkring to milliarder år gammelt.

[2] Når kvasarens lys passerer igennem gasskyen vil nogle af bølgelængderne bliver absorberet. Mønstrene af dette absorptionsfingeraftryk kan fortælle astronomerne meget omkring gassens bevægelse og kemiske sammensætning. Uden kvasaren i baggrunden ville meget mindre information kunne findes - gasskyen lyser ikke, og kan ikke ses i direkte billeder.

[3] SINFONI står for Spectrograph for INtegral Field Observations in the Near Infrared men UVES står for UVES is the Ultraviolet and Visual Echelle Spectrograph. De er begge monteret på ESOs Very Large Telescope. SINFONI afslørede gassens bevægelse i selve galaksen, og UVES effekterne af gassen omkring galaksen i lyset fra den fjerne kvasar.

Mere information

Denne forskning kan ses i den videnskabelige artikel “Signatures of Cool Gas Fueling a Star-Forming Galaxy at Redshift 2.3”, der kan læses d. 5. juli 2013 i journalen Science.

Gruppen bestod af N. Bouché (CNRS; IRAP, Frankrig), M. T. Murphy (Swinburne University of Technology, Melbourne, Australien), G. G. Kacprzak (Swinburne University of Technology, Australien; Australian Research Council Super Science Fellow), C. Péroux (Aix Marseille University, CNRS, Frankrig), T. Contini (CNRS; University Paul Sabatier of Toulouse, Frankrig), C. L. Martin (University of California Santa Barbara, USA), M. Dessauges-Zavadsky (Observatory of Geneva, Schweiz).

ESO er den mest fremtrædende internationale astronomi-organisation i Europa og verdens mest produktive astronomiske observatorium. ESO har i dag følgende 15 medlemslande: Belgien, Brasilien, Danmark, Finland, Frankrig, Holland, Italien, Portugal, Schweiz og Storbritannien, Spanien, Sverige, Tjekkiet, Tyskland og Østrig. ESOs aktiviteter er fokuseret på design, konstruktion og drift af jordbaserede observationsfaciliteter for at muliggøre vigtige videnskabelige opdagelser inden for astronomi. ESO spiller også en ledende rolle for at fremme og organisere samarbejdet inden for astronomisk forskning. I Chile driver ESO tre unikke observatorier i verdensklasse: La Silla, Paranal og Chajnantor. På Paranal driver ESO Very Large Telescope (VLT), der er verdens mest avancerede astronomiske observatorium til observationer i synligt lys samt to kortlægningsteleskoper. VISTA arbejder i infrarødt lys og er verdens største kortlægningsteleskop, mens VLT Survey Telescope (VST) er det største teleskop, der udelukkende er bygget til at kortlægge himlen i synligt lys. ESO er den europæiske partner i et revolutionerede astronomisk teleskop kaldet ALMA, det største igangværende astronomiske projekt. ESO planlægger i øjeblikket et 39 meter optisk/nær-infrarødt teleskop kaldet European Extremely Large Telescope (E-ELT), der vil blive ”verdens største øje mod himlen”.

Links

Kontakter

Nicolas Bouché
Observatoire Midi-Pyrénées–IRAP
Toulouse, France
Tel: +33 5 61 33 27 87
Mobil: +33 7 51 51 46 83
E-mail: Nicolas.Bouche@irap.omp.eu

Michael Murphy
Centre for Astrophysics and Supercomputing, Swinburne University of Technology
Melbourne, Australia
Tel: +61 3 9214 5818
Mobil: +61 405 214 461
E-mail: mmurphy@swin.edu.au

Richard Hook
ESO education and Public Outreach Department
Garching bei München, Germany
Tel: +49 89 3200 6655
Mobil: +49 151 1537 3591
E-mail: rhook@eso.org

Ole J. Knudsen (Pressekontakt Danmark)
ESOs formidlingsnetværk og Aarhus Space Centre, Aarhus Universitet
Aarhus, Danmark
Tel: +45 8715 5597
E-mail: eson-denmark@eso.org

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Dette er en oversættelse af ESO pressemeddelelse eso1330 lavet af ESON - et netværk af personer i ESOs medlemslande, der er kontaktpunkter for medierne i forbindelse med ESO nyheder, pressemeddelelser mm.

Om pressemeddelelsen

Pressemeddelelse nr.:eso1330da
Navn:HE 2243-60, QSO J2246-6015
Type:Early Universe : Galaxy
Early Universe : Galaxy : Activity : AGN : Quasar
Facility:Very Large Telescope
Instruments:SINFONI, UVES
Science data:2013Sci...341...50B

Billeder

Illustration af galaksen der indfanger materiale fra sine omgivelser
Illustration af galaksen der indfanger materiale fra sine omgivelser
Himlen omkring kvasaren HE 2243-6031
Himlen omkring kvasaren HE 2243-6031

Videoer

Zoom of an artist's impression of a galaxy accreting material from its surroundings
Zoom of an artist's impression of a galaxy accreting material from its surroundings
tekst kun tilgængelig på engelsk

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