Distant early-type galaxies: tracers of the galaxy mass assembly evolution

We review the most recent observational results on the formation and evolution of early-type galaxies and their mass assembly by focusing on: the existence, properties and role of distant old, massive, passive systems to z~2, the stellar mass function evolution, the ``downsizing'' scenario, and the high-z precursors of massive early-type galaxies.Comment: 8 pages, 7 figures; invited review at the Workshop on "AGN and galaxy evolution", Specola Vaticana, Castel Gandolfo, Italy, 3-6 October 200

The near-infrared view of galaxy evolution

Near-infrared surveys provide one of the best opportunities to investigate the cosmic evolution of galaxies and their mass assembly. We briefly review the main results obtained so far with the K20 and other recent near-IR surveys on the redshift distribution, the evolution of the luminosity function and luminosity density, the nature of old and dusty EROs, the evolution of the galaxy stellar mass function, the properties of the galaxies in the ``redshift desert'' and the nature of luminous starbursts at z~2.Comment: 6 pages, 2 figures, invited contribution, to appear in the Proceedings of the ESO/USM/MPE Workshop on "Multiwavelength Mapping of Galaxy Formation and Evolution", eds. R. Bender and A. Renzin

Odors, words and objects

The paper focuses on concepts and words referring to odors and to objects that have an odor. We argue that odors are an interesting object of study since they are evanescent, and since odor words do not refer to concrete and manipulable objects, but to scents evoked by objects. A second reason why odors are interesting is that some languages, as the Western ones, lack a specific odor lexicon, comparable in richness and variety to the color lexicon, and that performance on odors naming is typically worse than performance in color naming. In this work we discuss three main issues. First, we illustrate literature showing that, even if odor words do not have concrete referents, many languages encode them quite easily: the case of odors suggests that word meaning cannot be exhausted by the relationship with a referent, and highlights the importance of the social sharing of meaning. Second, we have discussed the peculiar status of odor concepts and words. Given their ambiguous status, their simple existence poses problems both to theories according to which concrete and abstract concepts do not differ, and to theories according to which they represent a dichotomy. Finally, we present an experiment in which we show that names of objects evoke their smell, and that these smells evoke approach and avoidance movements, in line with theories according to which words are grounded in both sensorial and motor systems

Redshift-space distortions of galaxies, clusters and AGN: testing how the accuracy of growth rate measurements depends on scales and sample selections

Redshift-space clustering anisotropies caused by cosmic peculiar velocities provide a powerful probe to test the gravity theory on large scales. However, to extract unbiased physical constraints, the clustering pattern has to be modelled accurately, taking into account the effects of non-linear dynamics at small scales, and properly describing the link between the selected cosmic tracers and the underlying dark matter field. We use a large hydrodynamic simulation to investigate how the systematic error on the linear growth rate, $f$, caused by model uncertainties, depends on sample selections and comoving scales. Specifically, we measure the redshift-space two-point correlation function of mock samples of galaxies, galaxy clusters and Active Galactic Nuclei, extracted from the Magneticum simulation, in the redshift range 0.2 < z < 2, and adopting different sample selections. We estimate $f\sigma_8$ by modelling both the monopole and the full two-dimensional anisotropic clustering, using the dispersion model. We find that the systematic error on $f\sigma_8$ depends significantly on the range of scales considered for the fit. If the latter is kept fixed, the error depends on both redshift and sample selection, due to the scale-dependent impact of non-linearities, if not properly modelled. On the other hand, we show that it is possible to get unbiased constraints on $f\sigma_8$ provided that the analysis is restricted to a proper range of scales, that depends non trivially on the properties of the sample. This can have a strong impact on multiple tracers analyses, and when combining catalogues selected at different redshifts.Comment: 17 pages, 14 figures. Accepted for publication in Astronomy & Astrophysic

Revisiting oldest stars as cosmological probes: new constraints on the Hubble constant

Despite the tremendous advance of observational cosmology, the value of the Hubble constant ($H_0$) is still controversial (the so called ``Hubble tension'') because of the inconsistency between local/late-time measurements and those derived from the cosmic microwave background. As the age of the Universe is very sensitive to $H_0$, we explored whether the present-day oldest stars could place independent constraints on the Hubble constant. To this purpose, we selected from the literature the oldest objects (globular clusters, stars, white dwarfs, ultra-faint and dwarf spheroidal galaxies) with accurate age estimates. Adopting a conservative prior on their formation redshifts ($11 \leq z_{\rm f} \leq 30$) and assuming $\Omega_{\rm M} = 0.3 \pm 0.02$, we developed a method based on Bayesian statistics to estimate the Hubble constant. We selected the oldest objects ($>13.3$ Gyr) and estimated $H_0$ both for each of them individually and for the average ages of homogeneous subsamples. Statistical and systematic uncertainties were properly taken into account. The constraints based on individual ages indicate that $H_0<70.6$ km/s/Mpc when selecting the most accurate estimates. If the ages are averaged and analyzed independently for each subsample, the most stringent constraints imply $H_0<73.0$ with a probability of 90.3% and errors around 2.5 km/s/Mpc. We also constructed an ``accuracy matrix'' to assess how the constraints on $H_0$ become more stringent with further improvements in the accuracy of stellar ages and $\Omega_{\rm M}$. The results show the high potential of the oldest stars as independent and competitive cosmological probes.Comment: 11 pages, 5 figures, 3 tables (including appendix). Submitted to Ap

Dust in high-z radio-loud AGN

We present continuum observations of a small sample of high-redshift, radio-loud AGN (radio galaxies and quasars) aimed at the detection of thermal emission from dust. Seven AGN were observed with IRAM and SEST at 1.25mm; two of them, the radio galaxies 1243+036 ($z \sim 3.6$) and MG1019+0535 ($z \sim 2.8$) were also observed at 0.8mm with the JCMT submillimetre telescope. Additional VLA observations were obtained in order to derive the spectral shape of the synchrotron radiation of MG1019+0535 at high radio frequencies. MG1019+0535 and TX0211$-$122 were expected to contain a large amount of dust based on their depleted Ly$\alpha$ emission. The observations suggest a clear 1.25-mm flux density excess over the synchrotron radiation spectrum of MG1019+0535, suggesting the presence of thermal emission from dust in this radio galaxy, whereas the observations of TX0211$-$122 were not sensitive enough to meaningfully constrain its dust content. On the other hand, our observations of 1243+036 provide a stringent upper limit on the total dust mass of $<10^8$ M$_{\odot}$. Finally, we find that the spectra of the radio-loud quasars in our sample ($2 < z < 4.5$) steepen between rest-frame radio and the far-infrared. We discuss the main implications of our results, concentrating on the dusty radio galaxy, MG1019+0535.Comment: 11 pages, A&A LaTeX, 4 figure

Catching galaxies in the act of quenching star formation

Detecting galaxies when their star-formation is being quenched is crucial to understand the mechanisms driving their evolution. We identify for the first time a sample of quenching galaxies selected just after the interruption of their star formation by exploiting the [O III]5007/Halpha ratio and searching for galaxies with undetected [O III]. Using a sample of ~174000 star-forming galaxies extracted from the SDSS-DR8 at 0.04 < z < 0.21,we identify the ~300 quenching galaxy best candidates with low [O III]/Halpha, out of ~26000 galaxies without [O III] emission. They have masses between 10^9.7 and 10^10.8 Mo, consistently with the corresponding growth of the quiescent population at these redshifts. Their main properties (i.e. star-formation rate, colours and metallicities) are comparable to those of the star-forming population, coherently with the hypothesis of recent quenching, but preferably reside in higher-density environments.Most candidates have morphologies similar to star-forming galaxies, suggesting that no morphological transformation has occurred yet. From a survival analysis we find a low fraction of candidates (~0.58% of the star-forming population), leading to a short quenching timescale of tQ~50Myr and an e-folding time for the quenching history of tauQ~90Myr, and their upper limits of tQ<0.76 Gyr and tauQ<1.5Gyr, assuming as quenching galaxies 50% of objects without [O III] (~7.5%).Our results are compatible with a 'rapid' quenching scenario of satellites galaxies due to the final phase of strangulation or ram-pressure stripping. This approach represents a robust alternative to methods used so far to select quenched galaxies (e.g. colours, specific star-formation rate, or post-starburst spectra).Comment: 22 pages, 23 figures, accepted for publication in MNRA

Effects of Massive Neutrinos on the Large-Scale Structure of the Universe

Cosmological neutrinos strongly affect the evolution of the largest structures in the Universe, i.e. galaxies and galaxy clusters. We use large box-size full hydrodynamic simulations to investigate the non-linear effects that massive neutrinos have on the spatial properties of cold dark matter (CDM) haloes. We quantify the difference with respect to the concordance LambdaCDM model of the halo mass function and of the halo two-point correlation function. We model the redshift-space distortions and compute the errors on the linear distortion parameter beta introduced if cosmological neutrinos are assumed to be massless. We find that, if not taken correctly into account and depending on the total neutrino mass, these effects could lead to a potentially fake signature of modified gravity. Future nearly all-sky spectroscopic galaxy surveys will be able to constrain the neutrino mass if it is larger than 0.6 eV, using beta measurements alone and independently of the value of the matter power spectrum normalisation. In combination with other cosmological probes, this will strengthen neutrino mass constraints and help breaking parameter degeneracies.Comment: Minor changes, refs added, the version to appear in MNRA