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Register a new userSynergistic science with Euclid and SKA : the nature and history of Star Formation
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Authors
Paolo Ciliegi
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We explored the impact of the synergy between the Euclid near-infrared photometric surveys and the SKA radio continuum surveys on the studies of the cosmic star formation. The Euclid satellite is expected to perform a Wide and Deep photometric surveys to an infrared limit of H ~ 24 and H ~ 26 respectively and a spectroscopy survey with a flux limit of $sim 3 times 10^{-16}$ erg cm$^{-2}$ s$^{-1}$ in the Halpha line. Combining the H band Euclid selected samples with the ground based ancillary data (fundamental for the SFR estimation) we will be able to detect the star forming galaxies down to SFRs of order of unit to z ~ 2 and down to SFR ~ 10 to z ~ 3, sampling the majority of the star forming galaxies up to z ~3 and beyond and placing definitive constraints on the star formation history of the universe at z<4-5 (is there a peak a z ~2 or a plateau at 1 <z <5 ?) and on the galaxies evolution models. The only tools able to provide a accurate dust-free calculation of their SFR are the SKA continuum surveys. The observational parameters of the Deep Tier SKA1 reference survey (a 0.2- 0.5 arcsec resolution and a 5 sigma detection limit of 1 microJy over 30 deg2 at Band 1/2 ) are the perfect complement of the Euclid survey. We showed, in fact, that with this kind of SKA survey we will be able to determine a dust unbiased SFR for a huge fraction (~85 %) of the Euclid SFG providing strong constraints on the star formation history of the Universe.
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Radio wavelengths offer the unique possibility of tracing the total star-formation rate in galaxies, both obscured and unobscured. As such, they may provide the most robust measurement of the star-formation history of the Universe. In this chapter we highlight the constraints that the SKA can place on the evolution of the star-formation history of the Universe, the survey area required to overcome sample variance, the spatial resolution requirements, along with the multi-wavelength ancillary data that will play a major role in maximising the scientific promise of the SKA. The required combination of depth and resolution means that a survey to trace the star formation in the Universe should be carried out with a facility that has a resolution of at least ~0.5arcsec, with high sensitivity at < 1 GHz. We also suggest a strategy that will enable new parameter space to be explored as the SKA expands over the coming decade.
Over the next decade, observations conducted with ALMA and the SKA will reveal the process of mass assembly and accretion onto young stars and will be revolutionary for studies of star formation. Here we summarise the capabilities of ALMA and discuss recent results from its early science observations. We then review infrared and radio variability observations of both young low-mass and high-mass stars. A time domain SKA radio continuum survey of star forming regions is then outlined. This survey will produce radio light-curves for hundreds of young sources, providing for the first time a systematic survey of radio variability across the full range of stellar masses. These light-curves will probe the magnetospheric interactions of young binary systems, the origins of outflows, trace episodic accretion on the central sources and potentially constrain the rotation rates of embedded sources.
Halo Occupation Distribution (HOD) is a model giving the average number of galaxies in a dark matter halo, function of its mass and other intrinsic properties, like distance from halo center, luminosity and redshift of its constituting galaxies. It is believed that these parameters could also be related to the galaxy history of formation. We want to investigate more this relation in order to test and better refine this model. To do that, we extract HOD indicators from EUCLID mock catalogs for different luminosity cuts and for redshifts ranges going from 0.1 < z < 3.0. We study and interpret the trends of indicators function of these variations and tried to retrace galaxy formation history following the idea that galaxy evolution is the combination rather than the conflict of the two main proposed ideas nowadays: the older hierarchical mass merger driven paradigm and the recent downsizing star formation driven approach.
$Lambda$-Warm Dark Matter (WDM) has been proposed as alternative scenario to $Lambda$ cold dark matter (CDM), motivated by discrepancies at the scale of dwarf galaxies, with less small-scale power and realized by collisionless particles with energies in the range $1-3$ keV. We present a new approach to constrain the viability of such WDM models using star formation histories of the dwarf spheroidal galaxies (dSphs) in the Local Group. We compare their high time-resolution star formation histories (SFHs) obtained with HST-based color magnitude diagrams with the range of possible collapse redshifts of their dark matter halos expected in CDM and in different WDM scenarios. The collapse redshift is inferred after determining a plausible infall mass of the subhalo. This is based on the current mass of individual dwarf inferred from stellar kinematics combined with results of cosmological simulations providing information on the subhalo evolution. Since WDM subhalos close to the filtering mass scale form significantly later than CDM, we show that they are in the first place difficult to reconcile with a truncation of star formation occurring as early as $zgeq 3$. The Ultra-Faint Dwarfs (UFDs) provide the most stringent constraints. Using 6 UFDs with the best determination of the SFHs, we show that we can exclude a 1 keV warm particle to a 2-$sigma$ confidence interval consistently with other methods reported in the literature. For some objects the $2$ keV model is also excluded. We discuss the various caveats of the method, most notably the low number of dwarfs with accurately determined star formation histories and the uncertainties in the determination of the infall mass of the subhalos. Our preliminary analysis serves as a pathfinder for future investigations that will combine upcoming accurate SFHs for more local dSphs with direct analysis of WDM cosmological simulations with baryons.
Highlights are presented about the science to be done with SKA. as well as state of the art science already done today with its precursors (MeerKAT, ASKAP) and pathfinders (LOFAR, NenuFAR), with accent on the expected breakthroughs.
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