Lecture 29 Flashcards
what relation was found in the late 90;s with the first measurements of a BH mass?
tight relations was found with the velocity dispersion of stars in galaxies(omega)
what is velocity dispersion in terms of galaxies and what does it mean for black hole growth
holds up ellipticals, spirals also lay on the relation using omega for just the central bulge. This suggests bulge of galaxies grow together
what happens as mergers randomise orbits
omega increases
what does mergers have to do with growth of BH
BH growth could be associated, Strongest AGN (BH growth) are in post merger remnants but statistically, evidence is weak
what does Cosmic BH growth rate density plot and the Madau plot (SF) show us when combined
the two track each other, offset by a factor of 3000
so BH grow tracing the total number of stars in the galaxy about 1/3000 as much
what do we need for the SHMR
energy release by AGN
what did models initially focus on for AGN feedback with mergers
focused on putting BHs, growing them and taking some energy and heating a gas near BH. AGN feedback added as heat around BH. This was influenced by ULIRG/AGN
merger scenario pros
explains why bulge and BH grow together
explains why ellipticals have large BHs
explains why Ellipticals have no cold gas
observe galaxies in these various stages
give full outline of merger scenario
isolated disk galaxy, small group of galaxies, galaxies interact/merge, ULIRG, blow out, quasar, decay, red and dead elliptical (quenched)
merger scenario cons
not nearly enough merger to happen to make all the ellipticals
after gas blow out, reaccelration will start in a Gyr or two but massive quenched galaxies haunt formed stars for at least 8 Gyr
AGN jets scenario:
Jets carry out lots of energy into CGM, could add heat to prevent gas cooling
don’t need much BH accretion to get a lot of energy
what is the downside to AGN jet scenario
jets mostly seen in quenched ellipticals, how do these become quenched ellipticals in the first place?
where are most AGN? evidence for jets
green Valley, not starbursts area where you would expect. Radio mode AGN could be responsible for turning galaxies from SF to quenched thru green valley
quasar mode agn feedback (ejective):
mergers make a galaxy an elliptical by causing an ULIRG then a quasar, resulting in elliptical
BH grows large, gas evacuated
radio mode AGN feedback (prevetive)
some gas falls onto large BH triggering a jet
jet keeps CGM hot, stalling future infall
cycle repeats whenever a bit of infall stars
what do we ned to get quenched massive galaxies
quasar mode agn feedback and radio mode agn feedback
how can you quench low mass galaxies if they are satellites
satellite at high velocity in a galaxy cluster full of hot gas
wind from hot cluster strips out satellite cold gas
saw as jellyfish galaxies, leave behind trails of cold gas
star formation stops when cold gas is stropped
not quenched by feedback, agn or otherwise
what happens as a satellite falls towards the centre of a cluster
it gets stripped so we expect more red satellites towards the centres of clusters which is saw in the sloan digital sky survey
why do galaxies M* not grow
AGN feedback quenches star formation
why does galaxies Mhalo continue to grow despite M* not growing
halo continues to accrete dark matter and hot gas
what happens as the halo of galaxies gets larger
SHMR drops
outline the basic story of galaxy formation
- CMB Fluctiations lead to cosmic web, filaments, sheets, nodes
- halos with disk (spiral) galaxies form in the middle
- groups and clusters of galaxies form
- spirals in denser reginons merge forming ellipticals
- temp merger phase creates ULRIG irregular galaxies
- spirals are blue, star forming, filled with cold gas and dust: ellipticals are red, not forming stars, contain hot gas with little or no dust
- inefficient conversion of baryons into stars in low-mass halos from supernova feedback
- hot CGM around massive E’s cool CGM AROUND SPRIALS
- mergers grow bhs. while growing they shine as AGN
- AGN from massive BHS put out energy that quenches galaxies via quasar + radio mode feedback
- AGN quench massive galaxies causing HI-Mhalo drop in SHMR
