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Register a new userObservational tests of the evolution of spheroidal galaxies and predictions for SIRTF/Spitzer cosmological surveys
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Laura Silva
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Granato et al(2004) have elaborated a physically grounded model exploiting the mutual feedback between star-forming spheroidal galaxies and the active nuclei growing in their cores to overcome, within the hierarchical clustering scenario for galaxy formation, one of the main challenges facing such scenario, the fact that massive spheroidal galaxies appear to have formed earlier and faster than predicted by previous models. Adopting the choice by Granato et al for the parameters governing the history of the SF,of chemical abundances and of the gas and dust content of galaxies, we are left with only two parameters affecting the time and mass dependent SED of spheroidal galaxies. After complementing the model with a simple description of evolutionary properties of starburst, normal late-type galaxies and AGNs we have successfully compared the model with a broad variety of observational data, deep K-band, ISO, IRAS, SCUBA, radio counts, the corresponding redshift distributions, the IR background spectrum, and also with data for EROs. We also present detailed predictions for the GOODS and SWIRE surveys with the Spitzer Space Telescope. We find that the GOODS deep survey at 24$mu$m and the SWIRE surveys at 70 and 160$mu$m are likely to be severely confusion limited. The GOODS surveys in the IRAC channels are expected to resolve most of the background, to explore the full passive evolution phase of spheroidal galaxies and most of their active star-forming phase, detecting galaxies up to zsimeq 4. A substantial number of high z star-forming spheroidal galaxies should also be detected by the 24mum SWIRE and GOODS surveys, while the 70 and 160mum will be particularly useful to study the evolution of such galaxies in the range 1 lsim z lsim 2.[abridged]
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Granato et al (2004) have elaborated a physically grounded model exploiting the mutual feedback between star-forming spheroidal galaxies and the active nuclei growing in their cores to overcome, in the framework of the hierarchical clustering scenario for galaxy formation, one of the main challenges facing such scenario, the fact that massive spheroidal galaxies appear to have formed much earlier and faster than predicted by previous semi-analytical models. After having assessed the values of the two parameters that control the effect of the complex radiative transfer processes on the time-dependent SEDs we have compared the model predictions with a variety of IR to mm data. Our results support a rather strict continuity between objects where stars formed and evolved massive early-type galaxies, indicating that large spheroidal galaxies formed most of their stars when they were already assembled as single objects. The model is successful in reproducing the observed z distribution of Kle20 galaxies at z>1, in contrast with both the classical monolithic and the semi-analytic models, the ratio of star-forming to passively evolving spheroids and the counts and z distributions of EROs. The model also favourably compares with the ISOCAM 6.7 mu counts, with the corresponding z distribution, and with IRAC counts, which probe primarily the passive evolution phase, and with the submm SCUBA and MAMBO data, probing the active star-formation phase. The observed fraction of 24mu selected sources with no detectable emission in either the 8mu or R band nicely corresponds to the predicted surface density of star-forming spheroids with 8mu fluxes below the detection limit. Predictions for the z distributions of 24mu sources detected by MIPS surveys are pointed out. [Abridged]
We make predictions for the cosmological surveys to be conducted by MIPS/SIRTF at 24, 70 and 160 microns, for the GTO and the legacy programs, using the latest knowledge of the instrument. In addition to detector and cirrus confusion noise, we discuss in detail the derivation of the confusion noise due to extragalactic sources, that depends strongly on the shape of the source counts at a given wavelength and on the telescope and detector pixel sizes. We show that it is wise in general to compare the classical photometric criterion and the so called source density criterion to predict the confusion levels. We obtain, using the model of Lagache, Dole, & Puget (2002) limiting fluxes of 50 microJy, 3.2 mJy and 36 mJy at 24, 70 and 160 microns (resp.). We compute the redshift distributions of the detected sources at each wavelength, and show that they extend up to z ~ 2.7 at 24 microns and up to z ~ 2.5 at 70 and 160 microns, leading to resolve at most 69, 54 and 24% of the Cosmic Infrared Background (CIB) at 24, 70 and 160 microns (resp.). We estimate which galaxy populations will be used to derive the luminosity function evolution with redshift. We also give the redshift distributions of the unresolved sources in the FIR range, that dominates the fluctuations of the CIB, and a predicted power spectrum showing the feasibility of fluctuations (due to Poissonian & clustered source distributions) measurements. The main conclusion is that MIPS (and SIRTF in general) cosmological surveys will greatly improve our understanding of galaxy evolution by giving data with unprecedented accuracy in the mid and far infrared range.
A modified theory of gravity, avoiding singularities in the standard theory of gravitation, has been developed by Hess & Greiner, known as the pseudo-complex theory of gravitation. The pc-GR theory shows remarkable observational differences with respect to standard GR. The intensity profiles are significantly different between both theories, which is a rare phenomenon in astrophysics. This will allow robust tests of both theories using Event Horizon Telescope (EHT) observations of the Galactic Center. We also predict the time evolution of orbiting matter. In this paper we summarize the observational tests we have developed to date. The theory is described in the second paper of this series (Hess et al. 2019, referred to as paper II hereafter).
We make predictions for the cosmological surveys to be conducted by the future Herschel mission operating in the far-infrared. The far-infrared bands match the peak of the CIRB, the brightest background of astrophysical origin. Therefore, surveys in these bands will provide essential information on the evolutionary properties of Luminous and Ultra-Luminous Infrared Galaxies (LIGs and ULIGs), starburst and normal galaxies. Our predictions are based on a new phenomenological model obtained from the 15-micron luminosity function of galaxies and AGN, fitting all the ISOCAM observables (source counts and redshift distributions) and also the recently published Spitzer source counts in the 24-micron band. We discuss the confusion noise due to extragalactic sources, depending strongly on the shape of the source counts and on the telescope parameters. We derive the fraction of the CIRB expected to be resolved by Herschel in the different wavebands and we discuss extragalactic surveys that could be carried on by Herschel for different scientific puropouses (i.e. ultra-deep, deep and shallow).
We present 3D hydrodynamic simulations aimed at studying the dynamical and chemical evolution of the interstellar medium in dwarf spheroidal galaxies. This evolution is driven by the explosions of Type II and Type Ia supernovae, whose different contribution is explicitly taken into account in our models. We compare our results with avaiable properties of the Draco galaxy. Despite the huge amount of energy released by SNe explosions, in our model the galaxy is able to retain most of the gas allowing a long period ($> 3$ Gyr) of star formation, consistent with the star formation history derived by observations. The stellar [Fe/H] distribution found in our model matches very well the observed one. The chemical properties of the stars derive from the different temporal evolution between Type Ia and Type II supernova rate, and from the different mixing of the metals produced by the two types of supernovae. We reproduce successfully the observed [O/Fe]-[Fe/H] diagram.
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