205 research outputs found
Supermassive black holes and their feedback effects in galaxy formation
Supermassive black holes play a key role in modern galaxy formation research. They are conjectured to be present in almost all massive galaxies, and through the release of enormous amounts of energy triggered by gas accretion, they are able to substantially change the properties of the host galaxy. To which extent and how the interaction mechanisms work is an open question. In this thesis, I review the current state of galaxy formation research with a focus on cosmological simulations of structure formation as well as the basic theories of supermassive black holes as far as they are important for galaxy formation. Subsequently, I discuss a new model for black hole growth and feedback in cosmological simulations, along with its application in large cosmological volume simulations. I show how supermassive black holes affect the formation and evolution of their host galaxy as well as their own growth. Furthermore, I present a model for supermassive black hole jets in a galaxy cluster environment. Applying this model, I study the coupling between the jet and the surrounding intra-cluster gas
The star-formation activity of IllustrisTNG galaxies: main sequence, UVJ diagram, quenched fractions, and systematics
We select galaxies from the IllustrisTNG hydrodynamical simulations
( at ) and characterize the shapes and
evolutions of their UVJ and star-formation rate -- stellar mass (SFR-)
diagrams. We quantify the systematic uncertainties related to different
criteria to classify star-forming vs. quiescent galaxies, different SFR
estimates, and by accounting for the star formation measured within different
physical apertures. The TNG model returns the observed features of the UVJ
diagram at , with a clear separation between two classes of galaxies.
It also returns a tight star-forming main sequence (MS) for with a dex scatter at in our fiducial choices. If a
UVJ-based cut is adopted, the TNG MS exhibits a downwardly bending at stellar
masses of about . Moreover, the model predicts that
per cent of galaxies at
are quiescent and the numbers of quenched galaxies at intermediate redshifts
and high masses are in better agreement with observational estimates than
previous models. However, shorter SFR-averaging timescales imply higher
normalizations and scatter of the MS, while smaller apertures lead to
underestimating the galaxy SFRs: overall we estimate the inspected systematic
uncertainties to sum up to about dex in the locus of the MS and to
about 15 percentage points in the quenched fractions. While TNG color
distributions are clearly bimodal, this is not the case for the SFR logarithmic
distributions in bins of stellar mass (SFRyr).
Finally, the slope and normalization of the TNG MS are consistent with
observational findings; however, the locus of the TNG MS remains lower by about
dex at than the available observational estimates taken
at face value.Comment: 24 pages, 4 tables, 11 figures. Accepted for publication on MNRA
Self-regulated AGN feedback of light jets in cool-core galaxy clusters
Heating from active galactic nuclei (AGN) is thought to stabilize cool-core
clusters, limiting star formation and cooling flows. We employ radiative
magneto-hydrodynamic (MHD) simulations to model light AGN jet feedback with
different accretion modes (Bondi-Hoyle-Lyttleton and cold accretion) in an
idealised Perseus-like cluster. Independent of the probed accretion model,
accretion efficiency, jet density and resolution, the cluster self-regulates
with central entropies and cooling times consistent with observed cool-core
clusters in this non-cosmological setting. We find that increased jet
efficiencies lead to more intermittent jet powers and enhanced star formation
rates. Our fiducial low-density jets can easily be deflected by orbiting cold
gaseous filaments, which redistributes angular momentum and leads to more
extended cold gas distributions and isotropic bubble distributions. In
comparison to our fiducial low momentum-density jets, high momentum-density jet
heats less efficiently and enables the formation of a persistent cold-gas disc
perpendicular to the jet that is centrally confined. Cavity luminosities
measured from our simulations generally reflect the cooling luminosities of the
intracluster medium (ICM) and correspond to averaged jet powers that are
relatively insensitive to short periods of low-luminosity jet injection. Cold
gas structures in our MHD simulations with low momentum-density jets generally
show a variety of morphologies ranging from discy to very extended filamentary
structures. In particular, magnetic fields are crucial to inhibit the formation
of unrealistically massive cold gas discs by redistributing angular momentum
between the hot and cold phases and by fostering the formation of elongated
cold filaments that are supported by magnetic pressure.Comment: 24 pages, 13 figures, submitted to MNRS. Comments welcome
First Results from the TNG50 Simulation: Galactic outflows driven by supernovae and black hole feedback
We present the new TNG50 cosmological, magnetohydrodynamical simulation --
the third and final volume of the IllustrisTNG project. This simulation
occupies a unique combination of large volume and high resolution, with a 50
Mpc box sampled by 2160^3 gas cells (baryon mass of 8x10^4 Msun). The median
spatial resolution of star-forming ISM gas is ~100-140 parsecs. This resolution
approaches or exceeds that of modern 'zoom' simulations of individual massive
galaxies, while the volume contains ~20,000 resolved galaxies with M*>10^7
Msun. Herein we show first results from TNG50, focusing on galactic outflows
driven by supernovae as well as supermassive black hole feedback. We find that
the outflow mass loading is a non-monotonic function of galaxy stellar mass,
turning over and rising rapidly above 10^10.5 Msun due to the action of the
central black hole. Outflow velocity increases with stellar mass, and at fixed
mass is faster at higher redshift. The TNG model can produce high velocity,
multi-phase outflows which include cool, dense components. These outflows reach
speeds in excess of 3000 km/s out to 20 kpc with an ejective, BH-driven origin.
Critically, we show how the relative simplicity of model inputs (and scalings)
at the injection scale produces complex behavior at galactic and halo scales.
For example, despite isotropic wind launching, outflows exhibit natural
collimation and an emergent bipolarity. Furthermore, galaxies above the
star-forming main sequence drive faster outflows, although this correlation
inverts at high mass with the onset of quenching, whereby low luminosity,
slowly accreting, massive black holes drive the strongest outflows.Comment: MNRAS, see also companion paper by Pillepich et al. (2019b).
Visualizations, movies, and an image gallery of paper figures available on
the TNG50 website: www.tng-project.or
First results from the IllustrisTNG simulations: the stellar mass content of groups and clusters of galaxies
The IllustrisTNG project is a new suite of cosmological
magneto-hydrodynamical simulations of galaxy formation performed with the Arepo
code and updated models for feedback physics. Here we introduce the first two
simulations of the series, TNG100 and TNG300, and quantify the stellar mass
content of about 4000 massive galaxy groups and clusters () at recent times (). The richest
clusters have half of their total stellar mass bound to satellite galaxies,
with the other half being associated with the central galaxy and the diffuse
intra-cluster light. The exact ICL fraction depends sensitively on the
definition of a central galaxy's mass and varies in our most massive clusters
between 20 to 40% of the total stellar mass. Haloes of and above have more diffuse stellar mass outside 100 kpc than within 100
kpc, with power-law slopes of the radial mass density distribution as shallow
as the dark matter's ( ). Total halo mass is a
very good predictor of stellar mass, and vice versa: at , the 3D stellar
mass measured within 30 kpc scales as with a
dex scatter. This is possibly too steep in comparison to the
available observational constraints, even though the abundance of TNG less
massive galaxies ( in stars) is in good agreement with
the measured galaxy stellar mass functions at recent epochs. The 3D sizes of
massive galaxies fall too on a tight (0.16 dex scatter) power-law
relation with halo mass, with . Even more fundamentally, halo mass alone is a good predictor
for the whole stellar mass profiles beyond the inner few kpc, and we show how
on average these can be precisely recovered given a single mass measurement of
the galaxy or its halo.Comment: Accepted by MNRAS, updated to match published version. Highlights:
Figures 5, 9, 11. The IllustrisTNG website can be found at
http://www.tng-project.org
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