BULGE FRACTION AND DISTRIBUTION OF STAR FORMATION IN SAMI GALAXIES Greg Goldstein PhD student, Dept of Physics and Astronomy, Macquarie University Supervisors: Dr Richard McDermid Dr Matt Owers

Galaxy Evolution: star-forming spirals decrease - quiescent ellipticals increase over time Brennan 2015

Spirals : disks, low bulge-to-disk fraction; contain cold gas that forms stars; blue colors. spirals transform into ellipticals via disk instability, or major galaxy mergers transformation accompanied by quenching which shifts them to the red sequence. spirals transform into ellipticals Ellipticals : spheroid-dominated, red, gas too hot to form stars.

DISK INSTABILITY, CLUMP MIGRATION AND BULGE FORMATION Star-forming clumps form quickly in the disk and move to the center, where they coalesce into a bulge within 1 Gyr.

mechanisms for quenching mass quenching AGN feedback. AGN activity driven by galaxy mergers, disc instabilities, bulge growth. Stellar Feedback Morphological quenching Virial shock heating: during collapse, gas can be heated via the conversion of gravitational potential energy into kinetic energy. Above a (redshift-dependent) critical halo mass of ∼ M ⊙, this shock heating may be able to keep a substantial fraction of the halo gas hot, leading to quenching environmental quenching ram pressure stripping, strangulation, tidal interaction

morphological quenching morphological transition from rotating stellar disk to pressure- supported spheroid. Removal of stellar disk, replaced by stellar spheroid. spheroid quenching may follow major merger, minor merger, or disk instabilities without gas removal or AGN feedback spheroid stabilizes inner disk against SF: – star formation less efficient – the higher concentration of stellar mass in the spheroid, affecting Toomre Q via kappa (epicyclic frequency or vorticity)

AGN Feedback: How responsible is it? Radio-mode: radiatively inefficient advection-dominated accretion flow; low accretion rates. Seen in local universe. Mechanical energy deposited by the jet heats ambient gas Quasar-mode: high radiative efficiency and high accretion rates close to the Eddington limit. High redshifts. Removes ambient gas from galaxy. Mechanisms (Cattaneo et al review 2009) Photons and jets from AGN drive winds: heat gas, photoionize metals, (gas expands  thermal ‘energy- driven’ winds) or radiation pressure (‘momentum-driven’ winds, role of dust).

the effect of bulge growth on the distribution of star formation integral field spectroscopy in the SAMI Galaxy Survey: explore distribution of star formation (SF) in disks of star-forming galaxies use nebular Hα recombination line - tracer of recent star formation compare SF in galaxies with varying bulge fraction.

ANALYSIS INDICES OF BULGE FRACTION  mass  Sersic index n  concentration of red continuum  u-r color  central velocity dispersion INDICES OF CONCENTRATION OF STAR FORMATION BASED ON CURVES OF GROWTH OF Hα  concentration of Hα using R90/R50 concentration index, Conselice conc index  scale parameter r50Hα/r50RC  radial profiles of Hα

concentration indices from curves of growth

no effect of mass/bulge fraction on scale ratio/conc Hα Sersic n: increased n associated with increased central Hα concentration

AGN: lower central concentration of Hα

conclusions spheroid growth not associated with decline in central SF concentration in SF galaxies AGN feedback associated with low central SF refined analysis using bulge-disk decompositions, radial profiles Hα other authors (Fabello, Bluck) find morphological quenching may not be dominant process – favor AGN feedback explanation