GALAXY MAI KUSAN BA CARBON, SHEKARA BILIYAN 1 BAYAN BIG BANG

Jim kaɗan bayan Big Bang, kwayoyin halitta na yau da kullum kusan hydrogen da helium ne kawai. Kowane sinadari mafi nauyi — carbon, oxygen, ƙarfe — an yi shi daga baya, a cikin taurari, kuma fashewarsu ce ta watsa shi.

Wannan yana da muhimmanci ga yadda ake haifar taurari. Girgijen iska da ke rushewa yana yin zafi yayin da yake ƙanƙancewa, kuma dole ne ya zubar da wannan zafi don ya rarrabu zuwa taurari. A Sararin Samaniya na yau, ion na carbon da oxygen ne ke yin yawancin sanyayawar, kuma girgije suna rarrabuwa zuwa taurari masu girma iri-iri, da yawa daga cikinsu ƙanana fiye da Rana. Ba tare da waɗannan sinadarai ba, girgijen farko za su iya yin sanyi ne kawai ta ƙwayoyin hydrogen. Sun rarrabu zuwa manyan guntaye, kuma taurarin da suka yi galibi manya ne.

Nawa ne ake buƙata na carbon da oxygen don a koma ga haifar taurari “na yau da kullum”? Kaɗan sosai: kusan 1/3,000 na rabon Rana. An wuce wannan iyaka da sauri ta yadda kowace galaxy mai nisa da aka gani tana haske har zuwa yanzu, har da ta James Webb Space Telescope, ta riga ta wuce shi sosai a lokacin da ta yi haske isasshe a gan ta.

Karanta girgije a cikin hasken quasar

Akwai wata hanya ta neman iskar farko: a bar ta ta sha hasken wani abu mafi haske da ke bayanta. Sarah Bosman, ta Heidelberg University, Frederick Davies, na Max Planck Institute for Astronomy, da abokan aiki 23 suna bincika quasar 30 mafi haske a redshift tsakanin 4.5 da 5.5 da GHOST, na’urar bakan haske da aka girka a 2024 a kan na’urar hangen nesa ta Gemini South a Chile, wadda suka bayyana a matsayin na’urar bakan haske mai babban daidaito mafi hankali da aka taɓa ginawa.

Hasken quasar J1941−4500 yana ratsa wani girgije mai kauri na hydrogen mara caji — “damped Lyman-alpha absorber”, irin ma’ajiyar iska da ake tsammanin tana cikin ’yan kiloparsec daga yankunan da galaxy ke haifar taurari. Kowane sinadari a cikin girgijen yana shan haske a tsawon raƙumansa. Bayan ɗaukar hoto na sa’o’i 5.8, ƙungiyar ta iya auna silicon, oxygen da carbon; ba a gano ƙarfe ko kaɗan ba.

Girgije mafi tsabta zuwa yanzu

Girgijen, mai suna UMP-DLA-1, yana a redshift 5.14, kusan shekara biliyan 1.1 bayan Big Bang. Lambobinsa:

• Carbon: ƙasa da sau 11,000 fiye da a cikin Rana idan aka kwatanta da hydrogen (kusan ƙasa da sau 16,000 da ma’aunin Rana mafi sabo).
• Oxygen da silicon: kusan ƙasa da sau 5,000 fiye da a cikin Rana.
• Wannan ya fi kowane irin girgije da aka sani a baya ƙarancin oxygen da silicon sama da sau uku, da ƙarancin carbon sau huɗu. Shi ne kuma mafi ƙarancin ƙarfe.
• Jimillar kason nauyin sinadarai masu nauyi fiye da helium: kashi 3.16 cikin miliyan.

Marubutan sun haɗa carbon da oxygen zuwa lamba ɗaya, “transition discriminant”, wadda ke hasashen ko girgije zai iya yin sanyi isasshe:

D_trans = log₁₀ (10^[C/H] + 0.3 × 10^[O/H])

Ƙasa da −3.5, girgije ba zai iya rushewa zuwa taurari ƙanana fiye da kusan nauyin Rana ɗaya ba. UMP-DLA-1 yana a −3.85. Shi ne ma’ajiyar iska ta farko da aka taɓa samu ƙasa da wannan layi — don haka ƙarancin ƙarfensa (metal) kaɗai ya tabbatar da cewa taurarinsa galibi masu nauyi ne.

Wani aljihu na ƙarshe na Sararin Samaniya na farko

Wannan yana nufin cewa haifar taurari a cikin iska kusan wadda ba a taɓa ba, da galibin manyan taurari, har yanzu yana yiwuwa tun bayan da taurari na farko suka bayyana — har ma bayan ƙarshen zamanin reionisation.

Sinadaran girgijen kuma samfuri ne na abin da waɗannan manyan taurari masu ƙarancin ƙarfe suka bari a baya lokacin da suka fashe: carbon ɗan ƙasa da oxygen, kuma oxygen da silicon a cikin gwargwadonsu na Rana. Shi kaɗai, wannan tsari ba zai iya faɗin ko taurarin ƙarni na farko ne na gaske ko ƙarni na biyu na farko ba. Amma ya yi daidai da girgijen da aka samu a lokuta na baya waɗanda aikin baya ya danganta da supernova 1 zuwa 30 kawai na taurari na ƙarni na farko. Marubutan suna ba da shawarar cewa farautar alamomin taurari na farko a cikin ragowar aljihun iska mai tsabta, a redshift ƙasa da 7, zai iya fi ba da sakamako fiye da duba baya can nesa, bayan redshift 20.

Wasu taurari tsofaffi sosai, matalauta sosai a cikin ƙananan dwarf galaxy kusa da Milky Way suna da irin wannan alamar sinadarai. Marubutan sun ce “mai yiwuwa ne sosai” su ne na ƙarshe da suka tsira daga cikin ƙananan taurarin da aka haifa a galaxy kamar wannan.

Sa’a, ko ruwan dare?

Samun irin wannan girgije a cikin quasar 30 kawai abin mamaki ne. Sai dai idan binciken ya yi sa’a ta ban mamaki, marubutan sun rubuta, ƙarin irin waɗannan girgije za su iya ɓoye a cikin bakan haske da ake da su, binne a cikin shan haske mai kauri na hydrogen na Sararin Samaniya na farko. Manyan na’urorin hangen nesa na nan gaba, kamar Extremely Large Telescope, idan aka karkatar da su ga quasar marasa haske da manufar Euclid za ta gano, ya kamata su yi cikakken ƙidaya. A yanzu, UMP-DLA-1 abu ɗaya ne, wanda aka auna bisa zaton cewa iskarsa tana motsi a matsayin dunƙule ɗaya — zato da marubutan suka goyi baya da rashin layukan shan haske masu cikawa (saturated).