67 research outputs found
AGN feedback, quiescence and CGM metal enrichment in early-type galaxies
We present three-dimensional hydrodynamical simulations showing the effect of
kinetic and radiative AGN feedback on a model galaxy representing a massive
quiescent low-redshift early-type galaxy of ,
harbouring a black hole surrounded by a
cooling gaseous halo. We show that, for a total baryon fraction of
of the cosmological value, feedback from the AGN can keep the galaxy quiescent
for about 4.35 Gyr and with properties consistent with black hole mass and
X-ray luminosity scaling relations. However, this can only be achieved if the
AGN feedback model includes both kinetic and radiative feedback modes. The
simulation with only kinetic feedback fails to keep the model galaxy fully
quiescent, while one with only radiative feedback leads to excessive black-hole
growth. For higher baryon fractions (e.g. 50\% of the cosmological value), the
X-ray luminosities exceed observed values by at least one order of magnitude,
and rapid cooling results in a star-forming galaxy. The AGN plays a major role
in keeping the circumgalactic gas at observed metallicities of within the central kpc by venting nuclear gas enriched
with metals from residual star formation activity. As indicated by previous
cosmological simulations, our results are consistent with a model for which the
black hole mass and the total baryon fraction are set at higher redshifts and the AGN alone can keep the model galaxy on observed scaling relations.
Models without AGN feedback violate both the quiescence criterion as well as
CGM metallicity constraints.Comment: 19 pages, 15 figures. Accepted for publication in MNRA
Momentum Driving: which physical processes dominate AGN feedback?
The deposition of mechanical feedback from a supermassive black hole (SMBH)
in an active galactic nucleus (AGN) into the surrounding galaxy occurs via
broad-line winds which must carry mass and radial momentum as well as energy.
The effect can be summarized by the dimensionless parameter
where
(\epslion_w \equiv dot{E}_w/(dot{M_accretion} c^2)) is the efficiency by
which accreted matter is turned into wind energy in the disc surrounding the
central SMBH. The outflowing mass and omentum are proportional to , and
many prior treatments have essentially assumed that . We perform one-
and two-dimensional simulations and find that the growth of the central SMBH is
very sensitive to the inclusion of the mass and momentum driving but is
insensitive to the assumed mechanical efficiency. For example in representative
calculations, the omission of momentum and mass feedback leads to an hundred
fold increase in the mass of the SMBH to over 10^{10} \Msun. When allowance
is made for momentum driving, the final SMBH mass is much lower and the wind
efficiencies which lead to the most observationally acceptable results are
relatively low with .Comment: 10 pages, 8 figures, resubmitted to ApJ, added reference
The Role of Black Hole Feedback on Size and Structural Evolution in Massive Galaxies
We use cosmological hydrodynamical simulations to investigate the role of
feedback from accreting black holes on the evolution of sizes, compactness,
stellar core density and specific star-formation of massive galaxies with
stellar masses of . We perform two sets of
cosmological zoom-in simulations of 30 halos to z=0: (1) without black holes
and Active Galactic Nucleus (AGN) feedback and (2) with AGN feedback arising
from winds and X-ray radiation. We find that AGN feedback can alter the stellar
density distribution, reduce the core density within the central 1 kpc by 0.3
dex from z=1, and enhance the size growth of massive galaxies. We also find
that galaxies simulated with AGN feedback evolve along similar tracks to those
characterized by observations in specific star formation versus compactness. We
confirm that AGN feedback plays an important role in transforming galaxies from
blue compact galaxies into red extended galaxies in two ways: (1) it
effectively quenches the star formation, transforming blue compact galaxies
into compact quiescent galaxies and (2) it also removes and prevents new
accretion of cold gas, shutting down in-situ star formation and causing
subsequent mergers to be gas-poor or mixed. Gas poor minor mergers then build
up an extended stellar envelope. AGN feedback also puffs up the central region
through the fast AGN driven winds as well as the slow expulsion of gas while
the black hole is quiescent. Without AGN feedback, large amounts of gas
accumulate in the central region, triggering star formation and leading to
overly massive blue galaxies with dense stellar cores.Comment: 13 pages, 7 figures, Accepted for publication in Ap
The impact of mechanical AGN feedback on the formation of massive early-type galaxies
We employ cosmological hydrodynamical simulations to investigate the effects
of AGN feedback on the formation of massive galaxies with present-day stellar
masses of . Using
smoothed particle hydrodynamics simulations with a pressure-entropy formulation
that allows an improved treatment of contact discontinuities and fluid mixing,
we run three sets of simulations of 20 halos with different AGN feedback
models: (1) no feedback, (2) thermal feedback, and (3) mechanical and radiation
feedback. We assume that seed black holes are present at early cosmic epochs at
the centre of emerging dark matter halos and trace their mass growth via gas
accretion and mergers with other black holes. Both feedback models successfully
recover the observed M_BH - sigma relation and black hole-to-stellar mass ratio
for simulated central early-type galaxies. The baryonic conversion efficiencies
are reduced by a factor of two compared to models without any AGN feedback at
all halo masses. However, massive galaxies simulated with thermal AGN feedback
show a factor of ~10-100 higher X-ray luminosities than observed. The
mechanical/radiation feedback model reproduces the observed correlation between
X-ray luminosities and velocity dispersion, e.g. for galaxies with sigma = 200
km/s, the X-ray luminosity is reduced from erg/s to erg/s.
It also efficiently suppresses late time star formation, reducing the specific
star formation rate from to on
average and resulting in quiescent galaxies since z=2, whereas the thermal
feedback model shows higher late time in-situ star formation rates than
observed.Comment: 13 pages, 11 figures, accepted for the publication in MNRA
Consequences of Mechanical and Radiative Feedback from Black Holes in Disc Galaxy Mergers
We study the effect of AGN mechanical and radiation feedback on the formation
of bulge dominated galaxies via mergers of disc galaxies. The merging galaxies
have mass-ratios of 1:1 to 6:1 and include pre-existing hot gaseous halos to
properly account for the global impact of AGN feedback. Using smoothed particle
hydrodynamics simulation code (GADGET-3) we compare three models with different
AGN feedback models: (1) no black hole and no AGN feedback; (2) thermal AGN
feedback; and (3) mechanical and radiative AGN feedback. The last model is
motivated by observations of broad line quasars which show winds with initial
velocities of 10,000 km/s and also heating associated with the
central AGN X-ray radiation. The primary changes in gas properties due to
mechanical AGN feedback are lower thermal X-ray luminosity from the final
galaxy - in better agreement with observations - and galactic outflows with
higher velocity km/s similar to recent direct observations of
nearby merger remnants. The kinetic energy of the outflowing gas is a factor of
20 higher than in the thermal feedback case. All merger remnants with
momentum-based AGN feedback with km/s and , independent of their progenitor mass-ratios, reproduce the
observed relations between stellar velocity dispersion and black hole mass
() as well as X-ray luminosity () with
erg/s erg/s for
velocity dispersions in the range of 120 km/s 190
km/s. In addition, the mechanical feedback produces a much greater AGN
variability. We also show that gas is more rapidly and impulsively stripped
from the galactic centres driving a moderate increase in galaxy size and
decrease in central density with the mechanical AGN feedback model.Comment: 16 pages, 10 figures, resubmitted to MNRA
The Impact of Outflows driven by Active Galactic Nuclei on Metals in and around Galaxies
Metals in the hot gaseous halos of galaxies encode the history of star
formation as well as the feedback processes that eject metals from the
galaxies. X-ray observations suggest that massive galaxies have extended
distributions of metals in their gas halos. We present predictions for the
metal properties of massive galaxies and their gaseous halos from recent high
resolution zoom-in simulations that include mechanical and radiation driven
feedback from Active Galactic Nuclei (AGN). In these simulations, AGN launch
high-velocity outflows, mimicking observed broad absorption line winds. By
comparing two sets of simulations with and without AGN feedback, we show that
our prescription for AGN feedback is capable of driving winds and enriching
halo gas `inside-out' by spreading centrally enriched metals to the outskirts
of galaxies, into the halo and beyond. The metal (iron) profiles of halos
simulated with AGN feedback have a flatter slope than those without AGN
feedback, consistent with recent X-ray observations. The predicted gas iron
abundance of group scale galaxies simulated with AGN feedback is at , which is 2.5 times higher than that
in simulations without AGN feedback. In these simulations, AGN winds are also
important for the metal enrichment of the intergalactic medium, as the vast
majority of metals ejected from the galaxy by AGN-driven winds end up beyond
the halo virial radius.Comment: Accepted for publication in ApJ. 16 pages, 9 figures. Key figures are
8 &
The impact of AGN on stellar kinematics and orbits in simulated massive galaxies
We present a series of 20 cosmological zoom simulations of the formation of
massive galaxies with and without a model for AGN feedback. Differences in
stellar population and kinematic properties are evaluated by constructing mock
integral field unit (IFU) maps. The impact of the AGN is weak at high redshift
when all systems are mostly fast-rotating and disc-like. After the
AGN simulations result in lower mass, older, less metal rich and slower
rotating systems with less disky isophotes - in general agreement with
observations. Two-dimensional kinematic maps of in-situ and accreted stars show
that these differences result from reduced in-situ star formation due to AGN
feedback. A full analysis of stellar orbits indicates that galaxies simulated
with AGN are typically more triaxial and have higher fractions of x-tubes and
box orbits and lower fractions of z-tubes. This trend can also be explained by
reduced late in-situ star formation. We introduce a global parameter, ,
to characterise the anti-correlation between the third-order kinematic moment
and the line-of-sight velocity (), and compare to
ATLAS observations. The kinematic asymmetry parameter might be a
useful diagnostic for large integral field surveys as it is a kinematic
indicator for intrinsic shape and orbital content
Linking galaxy structural properties and star formation activity to black hole activity with IllustrisTNG
We study the connection between active galactic nuclei (AGN) and their host
galaxies through cosmic time in the large-scale cosmological IllustrisTNG
simulations. We first compare BH properties, i.e. the hard X-ray BH luminosity
function, AGN galaxy occupation fraction, and distribution of Eddington ratios,
to available observational constraints. The simulations produce a population of
BHs in good agreement with observations, but we note an excess of faint AGN in
hard X-ray (L_x ~ 10^{43-44} erg/s), and a lower number of bright AGN
(L_x>10^{44} erg/s), a conclusion that varies quantitatively but not
qualitatively with BH luminosity estimation method. The lower Eddington ratios
of the 10^{9} Msun BHs compared to observations suggest that AGN feedback may
be too efficient in this regime. We study galaxy star formation activity and
structural properties, and design sample-dependent criteria to identify
different galaxy types (star-forming/quiescent, extended/compact) that we apply
both to the simulations and observations from the candels fields. We analyze
how the simulated and observed galaxies populate the specific star formation
rate - stellar mass surface density diagram. A large fraction of the z=0
M_{star}>10^{11} Msun quiescent galaxies first experienced a compaction phase
(i.e. reduction of galaxy size) while still forming stars, and then a quenching
event. We measure the dependence of AGN fraction on galaxies' locations in this
diagram. After correcting the simulations with a redshift and AGN
luminosity-dependent model for AGN obscuration, we find good qualitative and
quantitative agreement with observations. The AGN fraction is the highest among
compact star-forming galaxies (16-20% at z~1.5-2), and the lowest among compact
quiescent galaxies (6-10% at z~1.5-2).Comment: 35 pages, 22 figures, accepted for publication in MNRA
On the Effects of Local Environment on Active Galactic Nucleus (AGN) in the Horizon Run 5 Simulation
We use the Horizon Run 5 cosmological simulation to study the effect of galaxy intrinsic properties and the local environment on active galactic nuclei (AGNs) characterized by their threshold of the accretion rate. We select galaxies in the stellar mass range 10 9.5 ≤ M * / M ⊙ ≤ 10 10.5 in the snapshot at redshift z = 0.625. Among various intrinsic properties, we find that the star formation rate of the host galaxy is most correlated to the AGN activity. To quantify the environment, we use background galaxy number density (large-scale environment) and distance and morphological type of the nearest neighbors (small-scale environment), and study their relative effects on the AGN properties. We find that, compared to the background density, the nearest neighbor environment is the dominant quantity determining the bolometric luminosity, star formation rate, and kinematic properties of AGNs and better dictates the gas mass of the host galaxy. We show that the cold gas content in the host galaxies is crucial in triggering AGN activity. However, when the nearest neighbor environment effects start to act at the neighbor distance of less than about half the virial radius of the neighbor, the neighbor environmental effects are the most dominant factor for quasar activity
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