87,026 research outputs found
Toward a tomographic analysis of the cross-correlation between planck cmb lensing and h-atlas galaxies
No full textINAF PRIN; ASI/INAF [2014-024-R.0]; INFN-INDARK initiative; Spanish MINECOBianchini, F., Lapi, A., Calabrese, M., Bielewicz, P., Gonzalez-Nuevo, J., Baccigalupi, C., Danese, L., Zotti, G.D., Bourne, N., Cooray, A., Dunne, L., Eales, S., Valiante, E
Measuring the spin of spiral galaxies
No full textWe compute the angular momentum, the spin parameter, and the related distribution function for dark matter halos hosting a spiral galaxy. We rely on scaling laws, inferred from observations, that link the properties of the galaxy to those of the host halo; we further assume that the dark matter has the same total specific angular momentum of the baryons. Our main results are as follows: (1) We find that the gas component of the disk significantly contributes to the total angular momentum of the system. (2) By adopting for the dark matter the observationally supported Burkert profile, we compute the total angular momentum of the disk and its correlation with the rotation velocity. (3) We find that the distribution function of the spin parameter λ peaks at a value of about 0.03, consistent with a no-major-merger scenario for the late evolution of spiral galaxies
Mechanical Behavior of Aluminum Sandwiches Made by Laser Welding
No full textAbstractAluminium sandwiches are interesting subcomponents for lightweight structures applied in rail cars for high speed. A method to realize aluminium sandwiches consists in welding sheets to elementary extruded profiles. Laser welding is the production technology that promises the better features in terms of quality and productivity. Thanks to concentrate energy and very small Heat Input (HI), the laser welding process minimizing the wide of the Heat Affected Zone (HAZ) and the distortions and allow high welding speed. In this work laser technique was applied to join a mock-up of a large aluminium sandwich panel. The mechanical behaviour of the assembled panel was investigated in the two main orthogonal direction of load by four point bending tests.Elastic-plastic FE Analysis confirm the results of bending tests and it is possible to appreciate the quality of welding process that produce joint strength and ductile. In fact in the both load direction it's possible to evaluate the plastic deformation on the welded beam without visible cracks in the welds. The data about the mechanical features of the welds for the FE analysis, about the 80% of the base materials, was achieved by tensile test on elementary but joint. The SEM fractography of the butt joint shows dimples in all the surface of the fracture, confirming the good quality and ductility of welds also in presence of some little micro porosity.The present paper is based on the achievements of the TRAIN Consortium within the research project SIFEG (Integrated freight transport rail-road), granted by the Italian Ministry of Economic Development for the Program “Industria 2015 – Mobilità Sostenibile”
Probing quasar feedback through enhanced Sunyaev-Zel'dovich signals
No full textWe show that powerful quasars feed enough energy back to the diffuse ambient baryons as to cause transient, enhanced Sunyaev-Zel’dovich effects, especially in early galaxies and groups. We compute amplitudes and statistics of the related signals in μwave and submm bands, and discuss their detectability with present and future instruments
The intracluster plasma
No full textThis study is devoted to the Sunyaev-Zeldovich (S-Z) effect, and important related topics in cluster and CMB research. S-Z science is about to be significantly enhanced by unique, multifaceted cluster and cosmological yield, at a level of precision in accord with the high standards of the current era that was heralded by spectacular achievements in cosmological CMB research. The pedagogical reviews and technical seminars included in this volume represent most of the important current topics in S-Z work and in the astrophysics of clusters. The publication touches upon all relevant aspects of the S-Z effect and its use as a precise cluster and cosmological probe. To commemorate the 40th anniversary of the detection of the CMB by Penzias and Wilson (in 1964), there is a chapter devoted to the history of this discovery. In his fascinating account of their work, he outlines also some lessons pertinent to current scientific issues. Other chapters discuss very interesting related observational work in Europe and the US
PIAL ARTERIOLAR VASOMOTION CHANGES DURING CORTICAL ACTIVATION IN RATS
No full textThe oscillatory pattern of pial arterioles, i.e. vasomotion, has been described since early 1980s, but the impact of neural activation on such oscillations has never been formally examined. Sciatic nerve stimulation, a well characterized model for studying neurovascular coupling (NVC), leads to a neural activity-related increase of pial arteriolar diameter in the contralateral hindlimb somatosensory cortex. Exploiting such an experimental model, the aim of the present study was to explore vasomotion and its changes during NVC with a novel analytical approach. Indeed, to characterize oscillations, we evaluated the total spectral power in the range 0.02-2.00 Hz and subdivided this frequency interval into seven 50% overlapping frequency bands. Results indicated that only arterioles overlying the stimulated hindlimb cortex showed a significant increase of total power, unlike arterioles overlaying the whisker barrel cortex, used as control for the vascular response specificity. The total power increase was sustained mainly by marked increments in the low frequency range, with two peaks at 0.03 and 0.08 Hz, and by a wide increase in the high frequency range (0.60-2.00 Hz) in the averaged spectrum. These activity-related spectral changes suggest: (i) that it is possible to assess the vascular responses by using total power; (ii) the existence of at least three distinct mechanisms involved in the control of NVC, two with a feedback frequency loop in the low frequency range and another one in the high range; (iii) a potential involvement of vasomotion in NVC. Moreover, these findings highlight the oscillatory nature of the mechanisms controlling NVC
Black hole and galaxy coevolution from continuity equation and abundance matching
No full textWe investigate the coevolution of galaxies and hosted supermassive black holes (BHs) throughout the history of the universe by a statistical approach based on the continuity equation and the abundance matching technique. Specifically, we present analytical solutions of the continuity equation without source terms to reconstruct the supermassive BH mass function from the active galactic nucleus (AGN) luminosity functions. Such an approach includes physically motivated AGN light curves tested on independent data sets, which describe the evolution of the Eddington ratio and radiative efficiency from slim- to thin-disk conditions. We nicely reproduce the local estimates of the BH mass function, the AGN duty cycle as a function of mass and redshift, along with the Eddington ratio function and the fraction of galaxies with given stellar mass hosting an AGN with given Eddington ratio. We exploit the same approach to reconstruct the observed stellar mass function at different redshift from the ultraviolet and far-IR luminosity functions associated with star formation in galaxies. These results imply that the build-up of stars and BHs in galaxies occurs via in situ processes, with dry mergers playing a ☉marginal role at least for stellar masses ≤ 3 × 1011 M☉ and BH masses 109 M where the statistical data are more secure and less biased by systematic errors. In addition, we develop an improved abundance matching technique to link the stellar and BH content of galaxies to the gravitationally dominant dark matter (DM) component. The resulting relationships constitute a testbed for galaxy evolution models, highlighting the complementary role of stellar and AGN feedback in the star formation process. In addition, they may be operationally implemented in numerical simulations to populate DM halos or to gauge subgrid physics. Moreover, they may be exploited to investigate the galaxy/AGN clustering as a function of redshift, mass, and/or luminosity. In fact, the clustering properties of BHs and galaxies are found to be in full agreement with current observations, thus further validating our results from the continuity equation. Finally, our analysis highlights that (i) the fraction of AGNs observed in the slim-disk regime, where most of the BH mass is accreted, increases with redshift; and (ii) already at z\gtrsim 6$ a substantial amount of dust must have formed over timescales 108 yr in strongly star-forming galaxies, making these sources well within the reach of ALMA surveys in (sub)millimeter bands
Tra Antonello, Bellini e storie perdute: quattro frammenti di Giovanni Buonconsiglio e Bartolomeo Montagna a confronto
No full textNew Relationships between Galaxy Properties and Host Halo Mass, and the Role of Feedbacks in Galaxy Formation
No full textWe present new relationships between halo masses (Mh) and several galaxy properties, including r*-band luminosities (Lr), stellar (Mstar) and baryonic masses, stellar velocity dispersions (σ), and black hole masses (MBH). Approximate analytic expressions are given. In the galaxy halo mass range 3×1010 Msolar<=Mh<=3×1013 Msolar the Mh-Lr, Mstar-Mh, and MBH-Mh relations are well represented by a double power law, with a break at Mh,break~3×1011 Msolar, corresponding to a mass in stars Mstar~1.2×1010 Msolar, to an r*-band luminosity Lr~5×109 Lsolar, to a stellar velocity dispersion σ~=88 km s-1, and to a black hole mass MBH~9×106 Msolar. The σ-Mh relation can be approximated by a single power law, although a double power law is a better representation. Although there are significant systematic errors associated with our method, the derived relationships are in good agreement with the available observational data and have comparable uncertainties. We interpret these relations in terms of the effect of feedback from supernovae and from the active nucleus on the interstellar medium. We argue that the break of the power laws occurs at a mass that marks the transition between the dominance of the stellar and the AGN feedback
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