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GONE WITH THE WIND

GONE WITH THE WIND. Galaxy Transformation in Abell 2125. Galaxy Cluster Abell 2125. Among richest clusters in Abell catalog Redshift z=0.25, D=3 billion light-years 266 confirmed members Uniquely rich in radio sources Complex structure; assembly by infall?

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GONE WITH THE WIND

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  1. GONE WITH THE WIND Galaxy Transformation in Abell 2125

  2. Galaxy Cluster Abell 2125 • Among richest clusters in Abell catalog • Redshift z=0.25, D=3 billion light-years • 266 confirmed members • Uniquely rich in radio sources • Complex structure; assembly by infall? • Underachieving in X-rays for a rich cluster • Laboratory for active galaxy evolution

  3. Trail of evidence • Radio survey shows A2125 as special • C153 among strongest radio emitters • Redshift survey identifies cluster components • Hubble imaging shows unusual structure • Narrowband imaging reveals O+ tail • Spectra show gas and stars move differently • Chandra shows soft X-ray tail

  4. Frazer Owen and Mike Ledlow at Kitt Peak

  5. Abell 2125 is unusual… A2125: X-ray clumps, many radio sources A2645: just as rich, X-rays smooth, few radio sources

  6. Galaxy redshifts show multiple subgroups: C153

  7. Hubble WFPC2 imagery • Asymmetric “flying fish” structure • Disturbed disk, chaotic dust lanes • Star-forming blue knots “downstream”

  8. Kitt Peak Mosaic images • Narrow-band filter isolated [O II] emission • Long ionized-gas trail stretching 200,000 ly • Mass greater than 100 million solar masses

  9. Gemini-N spectra • Burst of star formation 100 million years ago (as galaxy entered cluster core?) involving several billion solar masses • This fits with galaxy being ~7 times too bright for its gravitational mass • Stars’ orbits not strongly disturbed • Gas and stellar motions are completely different – which would not result from gravity during a tidal interaction

  10. Gemini spectrum Best-fit model: (100 Myr burst on 10-Gyr basis)

  11. Chandra X-ray results • C153 shows a trail in soft X-rays (cooler gas than surrounding cluster material) • Roughly matches optical gas trail

  12. Galaxies in the eggbeater • Known since Butcher/Oemler in 1978 that galaxy populations in rich clusters change with time (especially over last 5 Gyr) • Hubble images show much of the action is in destruction/transformation of spirals • Usually hard to distinguish roles of multiple processes in these busy environments

  13. Coma - 300 million l.y. (Bothun/McGraw-Hill Obs.)

  14. Abell 851 – 5 billion l.y. Hubble (Dressler/Morrison)

  15. Coma cluster in X-rays U. Briel et al, XMM-Newton

  16. Clusters themselves are dynamic • Local redshift model implies Virgo growing • Even rich “relaxed” clusters (Coma) show X-ray and redshift substructure • Clusters as well as galaxies grow by merger and acquisition

  17. Where have all the spirals gone? • Most into elliptical and S0 galaxies • Galaxy collisions/mergers • Tidal forces from the cluster core • Cumulative weak tides – “harassment” • Stripping by ram pressure as galaxies move through hot cluster gas • These would often happen together and are difficult to separate

  18. An ongoing view of stripping • C153 has an unusually high velocity within A2125 (at least 2000 km/s) • It is the only large disk to have passed close to the dense gas of the cluster core • Distinct star/gas responses tell us that its transformation is being dominated by gas stripping.

  19. Summary • We see all the signatures of ongoing stripping of gas from a spiral galaxy • Previous detections have inferred this process from its aftermath, or seen more subtle effects from a single tracer • Favorable circumstances of C153 allow this process to be seen very clearly • Is this the Milky Way in 50 billion years?

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