46 research outputs found
Statistics of thermal gas pressure as a probe of cosmology and galaxy formation
The statistics of thermal gas pressure are a new and promising probe of cosmology and astrophysics. The large-scale cross-correlation between galaxies and the thermal Sunyaev-Zeldovich effect gives thebias-weighted mean electron pressure, hbhPei. In this paper, we show that hbhPei is sensitive to the amplitude of fluctuations in matter density, for example hbhPei â Ă°Ï8Ω0.81 m h0.67Ă3.14 at redshift z ÂŒ 0. We find that at z < 0.5 the observed hbhPei is smaller than that predicted by the state-of-the-art hydrodynamical simulations of galaxy formation, MillenniumTNG, by a factor of 0.93. This can beexplained by a lower value of Ï8 and Ωm, similar to the so-called âS8 tensionâ seen in the gravitational lensing effect, although the influence of astrophysics cannot be completely excluded. The difference between Magneticum and MillenniumTNG at z < 2 is small, indicating that the difference in the galaxy formation models used by these simulations has little impact on hbhPei at this redshift range. At higher z, we find that both simulations are in a modest tension with the existing upper bounds on hbhPei. We also find a significant difference between these simulations there, which we attribute to a larger sensitivity to the galaxy formation models in the high redshift regime. Therefore, more precise measurements of hbhPei at allredshifts will provide a new test of our understanding of cosmology and galaxy formation
Statistics of thermal gas pressure as a probe of cosmology and galaxy formation
The statistics of thermal gas pressure are a new and promising probe of
cosmology and astrophysics. The large-scale cross-correlation between galaxies
and the thermal Sunyaev-Zeldovich effect gives the bias-weighted mean electron
pressure, . In this paper, we show that
is sensitive to the amplitude of fluctuations
in matter density, for example at redshift
. We find that at the observed is
smaller than that predicted by the state-of-the-art hydrodynamical simulations
of galaxy formation, MillenniumTNG, by a factor of . This can be
explained by a lower value of and , similar to
the so-called " tension'' seen in the gravitational lensing effect,
although the influence of astrophysics cannot be completely excluded. The
difference between Magneticum and MillenniumTNG at is small, indicating
that the difference in the galaxy formation models used by these simulations
has little impact on at this redshift range.
At higher , we find that both simulations are in a modest tension with the
existing upper bounds on . We also find a
significant difference between these simulations there, which we attribute to a
larger sensitivity to the galaxy formation models in the high redshift regime.
Therefore, more precise measurements of at all
redshifts will provide a new test of our understanding of cosmology and galaxy
formation.Comment: 16 pages, 10 figure
Interpreting Sunyaev-Zel'dovich observations with MillenniumTNG: Mass and environment scaling relations
In the coming years, Sunyaev-Zel'dovich (SZ) measurements can dramatically
improve our understanding of the Intergalactic Medium (IGM) and the role of
feedback processes on galaxy formation, allowing us to calibrate important
astrophysical systematics in cosmological constraints from weak lensing galaxy
clustering surveys. However, the signal is only measured in a two-dimensional
projection, and its correct interpretation relies on understanding the
connection between observable quantities and the underlying intrinsic
properties of the gas, in addition to the relation between the gas and the
underlying matter distribution. One way to address these challenges is through
the use of hydrodynamical simulations such as the high-resolution, large-volume
MillenniumTNG suite. We find that measurements of the optical depth, ,
and the Compton-y parameter, , receive large line-of-sight contributions
which can be removed effectively by applying a Compensated Aperture Photometry
(CAP) filter. In contrast with other probes (e.g., X-rays and Fast Radio
Bursts), the kSZ-inferred receives most of its signal from a confined
cylindrical region around the halo due to the velocity decorrelation along the
line-of-sight. Additionally, we perform fits to the and scaling
relations and report best-fit parameters adopting the smoothly broken power law
(SBPL) formalism. We note that subgrid physics modeling can broaden the error
bar on these by 30\% for intermediate-mass halos (). The scatter of the scaling relations can be captured by an
intrinsic dependence on concentration, and an extrinsic dependence on tidal
shear. Finally, we comment on the effect of using galaxies rather than halos in
real observations, which can bias the inferred SZ profiles by 20\% for
-galaxies.Comment: 14 pages, 6 figure
Interpreting SunyaevâZelâdovich observations with MillenniumTNG: mass and environment scaling relations
SunyaevâZelâdovich (SZ) measurements can dramatically improve our understanding of the intergalactic medium and the role of feedback processes in galaxy formation, allowing us to calibrate important astrophysical systematics in cosmological constraints from weak lensing galaxy clustering surveys. However, the signal is only measured in a two-dimensional projection, and its correct interpretation relies on understanding the connection between observable quantities and the underlying intrinsic properties of the gas, in addition to the relation between the gas and the underlying matter distribution. One way to address these challenges is through the use of hydrodynamical simulations such as the high-resolution, large-volume MillenniumTNG suite. We find that measurements of the optical depth, Ï , and the Compton-y parameter, Y, receive large line-of-sight contributions that can be removed effectively by applying a compensated aperture photometry filter. In contrast with other Ï probes (e.g. X-rays and fast radio bursts), the kinematic SZ-inferred Ï receives most of its signal from a confined cylindrical region around the halo due to the velocity decorrelation along the line of sight. Additionally, we perform fits to the YâM and ÏâM scaling relations and report best-fitting parameters adopting the smoothly broken power law formalism. We note that subgrid physics modelling can broaden the error bar on these by 30 per cent for intermediate-mass haloes (âŒ1013 M). The scatter of the scaling relations canbe captured by an intrinsic dependence on concentration and an extrinsic dependence on tidal shear. Finally, we comment on theeffect of using galaxies rather than haloes in observations, which can bias the inferred profiles by âŒ20 per cent for Lâ galaxies
The MillenniumTNG Project: the large-scale clustering of galaxies
Modern redshift surveys are tasked with mapping out the galaxy distribution over enormous distance scales. Existing hydrodynamical simulations, however, do not reach the volumes needed to match upcoming surveys. We present results for the clustering of galaxies using a new, large volume hydrodynamical simulation as part of the MillenniumTNG (MTNG) project. With a computational volume that is â15 times larger than the next largest such simulation currently available, we show that MTNG is able to accurately reproduce the observed clustering of galaxies as a function of stellar mass. When separated by colour, there are some discrepancies with respect to the observed population, which can be attributed to the quenching of satellite galaxies in our model. We combine MTNG galaxies with those generated using a semi-analytic model to emulate the sample selection of luminous red galaxies (LRGs) and emission-line galaxies (ELGs) and show that, although the bias of these populations is approximately (but not exactly) constant on scales larger than â10 Mpc, there is significant scale-dependent bias on smaller scales. The amplitude of this effect varies between the two galaxy types and between the semi-analytic model and MTNG. We show that this is related to the distribution of haloes hosting LRGs and ELGs. Using mock SDSS-like catalogues generated on MTNG lightcones, we demonstrate the existence of prominent baryonic acoustic features in the large-scale galaxy clustering. We also demonstrate the presence of realistic redshift space distortions in our mocks, finding excellent agreement with the multipoles of the redshift-space clustering measured in SDSS data
The MillenniumTNG Project: semi-analytic galaxy formation models on the past lightcone
Upcoming large galaxy surveys will subject the standard cosmological model, Lambda Cold Dark Matter, to new precision tests. These can be tightened considerably if theoretical models of galaxy formation are available that can predict galaxy clustering and galaxyâgalaxy lensing on the full range of measurable scales, throughout volumes as large as those of the surveys, and with sufficient flexibility that uncertain aspects of the underlying astrophysics can be marginalized over. This, in particular, requires mock galaxy catalogues in large cosmological volumes that can be directly compared to observation, and can be optimized empirically by Monte Carlo Markov Chains or other similar schemes, thus eliminating or estimating parameters related to galaxy formation when constraining cosmology. Semi-analytic galaxy formation methods implemented on top of cosmological dark matter simulations offer a computationally efficient approach to construct physically based and flexibly parametrized galaxy formation models, and as such they are more potent than still faster, but purely empirical models. Here, we introduce an updated methodology for the semi-analytic L-GALAXIES code, allowing it to be applied to simulations of the new MillenniumTNG project, producing galaxies directly on fully continuous past lightcones, potentially over the full sky, out to high redshift, and for all galaxies more massive than ⌠108 M. We investigate the numerical convergence of the resulting predictions, and study the projected galaxy clustering signals of different samples. The new methodology can be viewed as an important step towards more faithful forward-modelling of observational data, helping to reduce systematic distortions in the comparison of theory to observations
The MillenniumTNG Project: High-precision predictions for matter clustering and halo statistics
Cosmological inference with large galaxy surveys requires theoretical models
that combine precise predictions for large-scale structure with robust and
flexible galaxy formation modelling throughout a sufficiently large cosmic
volume. Here, we introduce the MillenniumTNG (MTNG) project which combines the
hydrodynamical galaxy formation model of IllustrisTNG with the large volume of
the Millennium simulation. Our largest hydrodynamic simulation, covering (500
Mpc/h)^3 = (740 Mpc)^3, is complemented by a suite of dark-matter-only
simulations with up to 4320^3 dark matter particles (a mass resolution of 1.32
x 10^8 Msun/h) using the fixed-and-paired technique to reduce large-scale
cosmic variance. The hydro simulation adds 4320^3 gas cells, achieving a
baryonic mass resolution of 2 x 10^7 Msun/h. High time-resolution merger trees
and direct lightcone outputs facilitate the construction of a new generation of
semi-analytic galaxy formation models that can be calibrated against both the
hydro simulation and observation, and then applied to even larger volumes -
MTNG includes a flagship simulation with 1.1 trillion dark matter particles and
massive neutrinos in a volume of (3000 Mpc)^3. In this introductory analysis we
carry out convergence tests on basic measures of non-linear clustering such as
the matter power spectrum, the halo mass function and halo clustering, and we
compare simulation predictions to those from current cosmological emulators. We
also use our simulations to study matter and halo statistics, such as halo bias
and clustering at the baryonic acoustic oscillation scale. Finally we measure
the impact of baryonic physics on the matter and halo distributions.Comment: submitted to MNRAS, 23 pages, 19 figures, for future public data
release, see https://www.mtng-project.or
The MillenniumTNG Project: The galaxy population at
The early release science results from have yielded an
unexpected abundance of high-redshift luminous galaxies that seems to be in
tension with current theories of galaxy formation. However, it is currently
difficult to draw definitive conclusions form these results as the sources have
not yet been spectroscopically confirmed. It is in any case important to
establish baseline predictions from current state-of-the-art galaxy formation
models that can be compared and contrasted with these new measurements. In this
work, we use the new large-volume ()
hydrodynamic simulation of the MillenniumTNG project, suitably scaled to match
results from higher resolution - smaller volume simulations, to make
predictions for the high-redshift () galaxy population and compare
them to recent observations. We show that the simulated galaxy
population is broadly consistent with observations until . From
, the observations indicate a preference for a galaxy population
that is largely dust-free, but is still consistent with the simulations. Beyond
, however, our simulation results underpredict the abundance of
luminous galaxies and their star-formation rates by almost an order of
magnitude. This indicates either an incomplete understanding of the new
data or a need for more sophisticated galaxy formation models
that account for additional physical processes such as Population~III stars,
variable stellar initial mass functions, or even deviations from the standard
CDM model. We emphasise that any new process invoked to explain this
tension should only significantly influence the galaxy population beyond
, while leaving the successful galaxy formation predictions of the
fiducial model intact below this redshift.Comment: Accepted for publication in MNRAS -- Part of the initial set of
papers introducing the MillenniumTNG project. Visit www.mtng-project.org for
more detail
Tracing the assembly histories of galaxy clusters in the nearby universe
We have compiled a sample of 67 nearby ( < 0.15) clusters of galaxies, for
which on average more than 150 spectroscopic members are available, and, by
applying different methods to detect substructures in their galaxy
distribution, we have studied their assembly history. Our analysis confirms
that substructures are present in 70% of our sample, having a significant
dynamical impact in 57% of them. A classification of the assembly state of the
clusters based on the dynamical significance of their substructures is
proposed. In 19% of our clusters, the originally identified brightest cluster
galaxy is not the central gravitationally dominant galaxy (CDG), but turns out
to be either the second-rank, or the dominant galaxy of a substructure (a SDG,
in our classification), or even a possible "fossil" galaxy in the periphery of
the cluster. Moreover, no correlation was found in general between the
projected offset of the CDG from the X-ray peak and its peculiar velocity. The
comparison of the CDGs properties with the assembly states and dynamical state
of the intracluster media, especially the core cooling status, suggests a
complex assembly history, with clear evidence of co-evolution of the CDG and
its host cluster in the innermost regions.Comment: Contains 33 pages, 12 figures, 8 tables. On the accompanying webpage
( http://www.astro.ugto.mx/recursos/HP_SCls/Top70.html ), we offer the
complete set of figures describing all clusters presented in this articl
The MillenniumTNG Project: the impact of baryons and massive neutrinos on high-resolution weak gravitational lensing convergence maps
We study weak gravitational lensing convergence maps produced from the MILLENNIUMTNG simulations by direct projection of the mass distribution on the past backwards lightcone of a fiducial observer. We explore the lensing maps over a large dynamic range in simulation mass and angular resolution, allowing us to establish a clear assessment of numerical convergence. By comparing full physics hydrodynamical simulations with corresponding dark-matter-only runs, we quantify the impact of baryonic physics on the most important weak lensing statistics. Likewise, we predict the impact of massive neutrinos reliably far into the non-linear regime. We also demonstrate that the âfixed & pairedâ variance suppression technique increases the statistical robustness of the simulation predictions on large scales not only for time slices but also for continuously output lightcone data. We find that both baryonic and neutrino effects substantially impact weak lensing shear measurements, with the latter dominating over the former on large angular scales. Thus, both effects must explicitly be included to obtain sufficiently accurate predictions for stage IV lensing surveys. Reassuringly, our results agree accurately with other simulation results where available, supporting the promise of simulation modelling for precision cosmology far into the non-linear regime