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Register a new userEarly evolution of galaxies and of large-scale structure from CMB experiments
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Added by
Gianfranco De Zotti
Publication date
2019
fields
Physics
and research's language is
English
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Next generation CMB experiments with arcmin resolution will, for free, lay the foundations for a real breakthrough on the study of the early evolution of galaxies and galaxy clusters, thanks to the detection of large samples of strongly gravitationally lensed galaxies and of proto-clusters of dusty galaxies up to high redshifts. This has an enormous legacy value. High resolution follow-up of strongly lensed galaxies will allow the direct investigation of their structure and kinematics up to z~6, providing direct information on physical processes driving their evolution. Follow-up of proto-clusters will allow an observational validation of the formation history of the most massive dark matter halos up to z~4, well beyond the redshift range accessible via X-ray or SZ measurements. These experiments will also allow a giant leap forward in the determination of polarization properties of extragalactic sources, and will provide a complete census of cold dust available for star formation in the local universe.
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[ABRIDGED] We aim to provide a holistic view on the typical size and kinematic evolution of massive early-type galaxies (ETGs), that encompasses their high-$z$ star-forming progenitors, their high-$z$ quiescent counterparts, and their configurations in the local Universe. Our investigation covers the main processes playing a relevant role in the cosmic evolution of ETGs. Specifically, their early fast evolution comprises: biased collapse of the low angular momentum gaseous baryons located in the inner regions of the host dark matter halo; cooling, fragmentation, and infall of the gas down to the radius set by the centrifugal barrier; further rapid compaction via clump/gas migration toward the galaxy center, where strong heavily dust-enshrouded star-formation takes place and most of the stellar mass is accumulated; ejection of substantial gas amount from the inner regions by feedback processes, which causes a dramatic puffing up of the stellar component. In the late slow evolution, passive aging of stellar populations and mass additions by dry merger events occur. We describe these processes relying on prescriptions inspired by basic physical arguments and by numerical simulations, to derive new analytical estimates of the relevant sizes, timescales, and kinematic properties for individual galaxies along their evolution. Then we obtain quantitative results as a function of galaxy mass and redshift, and compare them to recent observational constraints on half-light size $R_e$, on the ratio $v/sigma$ between rotation velocity and velocity dispersion (for gas and stars) and on the specific angular momentum $j_star$ of the stellar component; we find good consistency with the available multi-band data in average values and dispersion, both for local ETGs and for their $zsim 1-2$ star-forming and quiescent progenitors.
We have searched for presence of current star formation in outer stellar rings of early-type disk (S0-Sb) galaxies by inspecting a representative sample of nearby galaxies with rings from the recent Spitzer catalog ARRAKIS (Comeron et al. 2014). We have found that regular rings (of R-type) reveal young stellar population with the age of less than 200~Myr in about half of all the cases, while in the pseudorings (open rings, R), which inhabit only spiral galaxies, current star formation proceeds almost always.
Our understanding of the cosmic evolution of supermassive black holes (SMBHs) has been revolutionized by the advent of large multiwavelength extragalactic surveys, which have enabled detailed statistical studies of the host galaxies and large-scale structures of active galactic nuclei (AGN). We give an overview of some recent results on SMBH evolution, including the connection between AGN activity and star formation in galaxies, the role of galaxy mergers in fueling AGN activity, the nature of luminous obscured AGN, and the connection between AGN and their host dark matter halos. We conclude by looking to the future of large-scale extragalactic X-ray and spectroscopic surveys.
The redshift distribution of galactic-scale lensing systems provides a laboratory to probe the velocity dispersion function (VDF) of early-type galaxies (ETGs) and measure the evolution of early-type galaxies at redshift z ~ 1. Through the statistical analysis of the currently largest sample of early-type galaxy gravitational lenses, we conclude that the VDF inferred solely from strong lensing systems is well consistent with the measurements of SDSS DR5 data in the local universe. In particular, our results strongly indicate a decline in the number density of lenses by a factor of two and a 20% increase in the characteristic velocity dispersion for the early-type galaxy population at z ~ 1. Such VDF evolution is in perfect agreement with the $Lambda$CDM paradigm (i.e., the hierarchical build-up of mass structures over cosmic time) and different from stellar mass-downsizing evolutions obtained by many galaxy surveys. Meanwhile, we also quantitatively discuss the evolution of the VDF shape in a more complex evolution model, which reveals its strong correlation with that of the number density and velocity dispersion of early-type galaxies. Finally, we evaluate if future missions such as LSST can be sensitive enough to place the most stringent constraints on the redshift evolution of early-type galaxies, based on the redshift distribution of available gravitational lenses.
Galaxies form and evolve in the context of their local and large-scale environments. Their baryonic content that we observe with imaging and spectroscopy is intimately connected to the properties of their dark matter halos, and to their location in the cosmic web of large-scale structure. Very large spectroscopic surveys of the local universe (e.g., SDSS and GAMA) measure galaxy positions (location within large-scale structure), statistical clustering (a direct constraint on dark matter halo masses), and spectral features (measuring physical conditions of the gas and stars within the galaxies, as well as internal velocities). Deep surveys with the James Webb Space Telescope (JWST) will revolutionize spectroscopic measurements of redshifts and spectral properties for galaxies out to the epoch of reionization, but with numerical statistics and over cosmic volumes that are too small to map large-scale structure and to constrain halo properties via clustering. Here, we consider advances in understanding galaxy evolution that would be enabled by very large spectroscopic surveys at high redshifts: very large numbers of galaxies (outstanding statistics) over large co-moving volumes (large-scale structure on all scales) over broad redshift ranges (evolution over most of cosmic history). The required observational facility can be established as part of the probe portfolio by NASA within the next decade.
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