Letters of Intent received in 2016

LoI 2018-1949
Dark Massive: Luminous and Dark Matter in Massive Galaxies

Topics

- Hyerarchical accretion
- Substructure, both local and at z~1
- Baryonic feedback
- Co-evolution of SMBHs and heir host galaxies since z~2
- Chemistry, multiple stellar and Globular Cluster populations
-Discrete halo tracers (Globular Clusters, Planetary Nebulae)
- X-ray gaseous halos
- Dynamics of massive galaxies and their dark matter halos
- Gravitational lensing
- Surveys

Rationale

The study of massive galaxies combines diverse fields of modern astrophysics, ranging from predictions of standard cosmology to the physics of gas accretion and star formation.

Cosmological simulations predict a hierarchical accretion of smaller structures onto larger ones, whose dark matter (DM) halos have almost universal density profiles and with a well defined substructure mass- function. Hence, the detection and characterization of substructure around massive galaxies enables crucial tests of predictions from the standard cosmological model. The quantitative study of luminous and dark substructure can either decree the triumph of CDM cosmology or lead to a rethinking of the whole paradigm, perhaps introducing more exotic forms of DM.
.
The buildup of stellar mass in the central regions of galaxies can alter the simple predictions from DM-only simulations. Depending on the timescales involved and amount of feedback from star-formation and Active Galactic Nuclei, the initial DM profiles can be made steeper or shallower. The hierarchical assembly of massive galaxies, as well as gas-dynamics, can lead to complex and extended star-formation, as is testified by colour gradients and multiple populations of Globular Clusters and Planetary Nebulae. Also, the accretion of circum-galactic gas can happen in radically different modes depending on the mass of the central object. These processes all concur to shape the final mass-profiles and stellar properties of massive galaxies. Modelling the structure of massive galaxies can then shed light on their DM content and mass profiles, establishing the contributions from different baryonic processes and the co-evolution channels of different components.

Observationally, massive galaxies show some general behaviours and puzzles that are not fully solved at present. For example, super-massive black hole masses correlate with the properties of their hosts (velocity dispersion and bulge mass), although the origin of this relationship is still debated. Modelling of gravitational lensing and stellar dynamics in massive galaxies has provided clues on their DM density profiles; however, sound theoretical predictions, a tighter control on observational uncertainties and studies on larger samples are needed. Finally, observations of X-ray emitting gas can yield valuable information on many aspects (masses, chemical composition, accretion modes and feedback, thermal instabilities), provided the observational and systematic uncertainties are well controlled.

The current status of research in massive galaxies is now benefiting from different factors, such as: spatially-resolved kinematics and chemistry, from integral-field spectroscopy and adaptive optics; extended surveys of nearby or massive galaxies; wide and deep searches for gravitational lenses; progress in hydro-dynamical simulations; large samples of resolved tracers (Globular Clusters and Planetary Nebulae); new X-ray observational facilities, with unprecedented spectral and angular resolution; refined and versatile modeling of kinematics, gravitational lensing and statistical inference
at population level.

Further improvement will soon be brought by many dedicated surveys, which by 2018 will be either complete or in full swing.In particular:
1. MaNGA, MGS, HET are gathering large samples of nearby and massive galaxies with spatially-resolved kinematics and chemistry.
2. The search for gravitational lens galaxies in deep and wide surveys (such as DES, KIDS, PanSTARRS-1) will soon unveil a wealth of new systems out to redshift z~1,
with potential for cosmography, galaxy evolution and substructure studies.
3. In the soft X-ray band (0.5-2 keV), where the gaseous halos of massive galaxies mostly emit, the eROSITA survey will have a spatial resolution comparable
to XMM-Newton and be ~30 times more sensitive than ROSAT.
4. MUSE is now surveying the spatially-resolved kinematics in the Fornax Cluster and in ~20 galaxies with M*>10^12.

Finally, theoretical understanding is gained from improvements in numerical simulations of galaxy formation. In particular, there is now a wider understanding of baryonic processes, such as gas dynamics and feedback from star-formation or Active Galactic Nuclei. Also, the resolution of simulations is now becoming sharp enough to provide predictions on the role of baryons in the central parts of galaxies.

Within the proposed Symposium taking place at the 30th IAU GA, we anticipate an intense interaction between specialists in these problems, towards a comprehensive understanding of issues, solutions and predictions.
With these in mind, we have outlined the composition of perspective SOC as follows:
Eric Peng (Peking), Luis Ho (Kavli Beijing)
Jenny Greene (Princeton), Oleg Gnedin (Michigan Univ)
Kosuke Sato (Tokyo Univ), Simon Driver (ICRAR Perth)
Laura Ferrarese (Victoria), Pierre-Alain Duc (IAP)
Anna Pasquali (ARI), Thomas Puzia (UCatolica),
Claudia Mendez de Oliveira (Brazil), Andreaa Font (LJMU)
- besides the Co-Chairs -.

The composition of the SOC is very well balanced with respect to Gender and Geografical coverage.