Lunedi 15 Luglio 2019, h. 11:30 

 Aula L. Rosino Dipartimento di Fisica e Astronomia

Tadayuki (Taddy) Kodama 

Astronomical Institute, Tohoku University

Transition of gas accretion mode in proto-clusters at the cosmic noon




Our Mahalo-Subaru project, a systematic narrow-band line emitter survey, has been mapping out star forming galaxies in and around galaxy clusters at 0.4<z<2.5, and revealing the inside-out quenching of star formation activities from cluster cores to the surrounding regions as time progresses.
  In the dense cores of the highest redshift cluster, we see an enhancement of star forming activities, which are likely driven by ample gas that is supplied by massive gas inflow through the filamentary structures. It is consistent with strong Lya line attenuations with respect to the Ha emission lines as indicated by dual narrow-band imaging (Lya and Ha), and also with higher molecular gas mass fraction as observed by ALMA.
  These results are different from recent studies of X-ray clusters at similar redshifts (z=2-2.5) where they find a deficit of gas while star formation efficiency tends to be higher in the cluster cores. Such discrepancy implies that the gas accretion mode may be changed from the cold accretion mode accompanied by high star formation activity, to the hot mode where gas cooling and thus accretion to galaxies become inefficient, resulting in the quenching of the cluster cores.
  If time allows, I will also touch on our on-going and future programs with Subaru and TAO to hunt photo-clusters and massive galaxies out to z=5 with medium-band imaging.




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