The European Alps are the site where classic geologic concepts such as nappe theory, continental subduction and slab breakoff have been first proposed. However, the deep tectonic structure of the ...Alps has long been poorly constrained by independent geophysical evidence. This review paper summarizes the main results of the CIFALPS passive seismic experiment, that was launched by Chinese, French and Italian scientists in the 2010s to provide new insights on the deep tectonic structure of the Alpine region. The application of a wide range of tomographic methods to the analysis of a single fossil subduction zone makes the CIFALPS experiment a potential reference case for the analysis of other orogenic belts. Major results include: (i) the first seismic evidence of European continental crust subducted into the Adriatic upper mantle, beneath the place where coesite was first recognized in continental (U)HP rocks in the Alps; (ii) evidence of a major involvement of the mantle wedge during (U)HP rock exhumation; (iii) evidence of a serpentinized plate interface favoring continental subduction; (iv) evidence of a continuous slab beneath the Western and Central Alps, ruling out the classic model of slab breakoff magmatism; (v) evidence of a polyphase development of anisotropic fabrics in the Alpine mantle, either representing active mantle flows or fossil fabrics inherited from previous rifting stages. Detection of these major tectonic features allows to propose interpretive geologic cross‐sections at the scale of the lithosphere and upper mantle, providing a baseline for future analyses of active continental margins.
Plain Language Summary
The European Alps are the site where classic geologic concepts such as nappe theory, continental subduction, and slab breakoff have been first proposed. However, the deep tectonic structure of the Alps has long been poorly constrained by independent geophysical evidence. This review paper summarizes the main results of the CIFALPS passive seismic experiment, which allows us to propose an updated image of the deep structure of the Alps at the scale of the lithosphere and the upper mantle. The concepts and ideas summarized in this article provide a baseline for further advances in the fields of Alpine tectonics and in the analysis of active continental margins more generally.
Key Points
Summary of the main results of the CIFALPS seismic experiment provides new insights on the deep tectonic structure of the Alpine region
Application of a wide range of tomographic methods and joint interpretation with geological and petrophysical data
Interpretive geologic cross‐sections at the scale of the lithosphere and the upper mantle
Aims. The goal of this work is to infer the star formation properties and the mass assembly process of high redshift ($0.3 \leq z < 2.5$) galaxies from their IR emission using the 24 μm band of ...MIPS-Spitzer. Methods. We used an updated version of the GOODS-MUSIC catalog, which has multiwavelength coverage from 0.3 to 24 μm and either spectroscopic or accurate photometric redshifts. We describe how the catalog has been extended by the addition of mid-IR fluxes derived from the MIPS 24 μm image. We compared two different estimators of the star formation rate (SFR hereafter). One is the total infrared emission derived from 24 μm, estimated using both synthetic and empirical IR templates. The other one is a multiwavelength fit to the full galaxy SED, which automatically accounts for dust reddening and age-star formation activity degeneracies. For both estimates, we computed the SFR density and the specific SFR. Results. We show that the two SFR indicators are roughly consistent, once the uncertainties involved are taken into account. However, they show a systematic trend, IR-based estimates exceeding the fit-based ones as the star formation rate increases. With this new catalog, we show that: a) at $z>0.3$, the star formation rate is correlated well with stellar mass, and this relationship seems to steepen with redshift if one relies on IR-based estimates of the SFR; b) the contribution to the global SFRD by massive galaxies increases with redshift up to $\simeq $2.5, more rapidly than for galaxies of lower mass, but appears to flatten at higher z; c) despite this increase, the most important contributors to the SFRD at any z are galaxies of about, or immediately lower than, the characteristic stellar mass; d) at $z\simeq 2$, massive galaxies are actively star-forming, with a median ${\it SFR} \simeq 300~ M_\odot$ yr-1. During this epoch, our targeted galaxies assemble a substantial part of their final stellar mass; e) the specific SFR (SSFR) shows a clear bimodal distribution. Conclusions. The analysis of the SFR density and the SSFR seems to support the downsizing scenario, according to which high mass galaxies have formed their stars earlier and more rapidly than their low mass counterparts. A comparison with renditions of theoretical simulations of galaxy formation and evolution indicates that these models follow the global increase in the SSFR with redshift and predict the existence of quiescent galaxies even at $z>1.5$. However, the average SSFR is systematically underpredicted by all models considered.
We used Early Release Science (ERS) observations taken with the Wide Field Camera 3 (WFC3) in the GOODS-S field to study the galaxy stellar mass function (GSMF) at 0.6 ≤ z < 4.5. Deep WFC3 near-IR ...data (for Y as faint as 27.3, J and H as faint as 27.4 AB mag at 5σ), as well as deep KS (as faint as 25.5 at 5σ) Hawk-I band data, provide an exquisite data set with which determine in an unprecedented way the low-mass end of the GSMF, allowing an accurate probe of masses as low as M∗ ≃ 7.6 × 109 M⊙ at z ~ 3. Although the area used is relatively small (~33 arcmin2), we found generally good agreement with previous studies on the entire mass range. Our results show that the slope of the faint-end increases with redshift, from α = −1.44 ± 0.03 at z ~ 0.8 to α = −1.86 ± 0.16 at z ~ 3, although indications exist that it does not steepen further between z ~ 3 and z ~ 4. This result is insensitive to any uncertainty in the M∗ parameter. The steepness of the GSMF faint-end solves the well-known disagreement between the stellar mass density (SMD) and the integrated star-formation history at z > 2. However, we confirm that there appears to be an excess of integrated star formation with respect to the SMD at z < 2, by a factor of ~2−3. Our comparison of the observations with theoretical predictions shows that the models forecast a greater abundance of low mass galaxies, at least up to z ~ 3, as well as a dearth of massive galaxies at z ~ 4 with respect to the data, and that the predicted SMD is generally overestimated at z ≲ 2.
We investigate the effect of AGN feedback associated with the bright QSO phase on the color distribution of galaxies from z = 0 up to z = 4. To this aim, we insert a blast-wave model of AGN feedback ...in our semianalytic model of galaxy formation, which includes the growth of supermassive black holes and the AGN activity triggered by interactions of the host galaxies. The AGN feedback is directly related to the impulsive, luminous quasar phase. We test our model by checking the consistency of its results against (1) the QSO luminosity functions from z = 0 to 4, and (2) the observed local relation between the black hole mass m sub(BH) and the mass of the host galaxy. At low redshift the inclusion of AGN feedback enhances the number of red bright galaxies so that the color distribution of M sub(r) < -22 objects is entirely dominated by red (u - r > 1.5) galaxies; at 0.5 < z < 2 it yields a rest-frame U - V color distribution, in agreement with existing observations. In the range z - 1.5-2.5, we find that 31% of galaxies contribute to the extremely red object (ERO) population with m sub(K)< 20 (Vega system); at such a magnitude, the model yields an ERO surface density of 6.3 x 10 super(3) deg super(2), matching existing data. Extending our analysis to z = 4, the model matches the observed surface density 1.5 x 10 super(3) deg super(2) of distant red galaxies (DRGs) at m sub(K)= 20; such a population is predicted to be dominated by galaxies with old stellar populations for z > 2.5.
Aims. We present a high quality multiwavelength (from 0.3 to 8.0 km) catalog of the large and deep area in the GOODS Southern Field covered by the deep near-IR observations obtained with the ESO VLT. ...Methods. The catalog is entirely based on public data: in our analysis, we have included the F435W, F606W, F115W and F850LP ACS images, the JHKs VLT data, the Spitzer data provided by IRAC instrument (3.6, 4.5, 5.8 and 8.0 km), and publicly available U-band data from the 2.2ESO and VLT-VIMOS. We describe in detail the procedures adopted to obtain this multiwavelength catalog. In particular, we developed a specific software for the accurate "PSF-matching" of space and ground-based images of different resolution and depth (ConvPhot), of which we analyse performances and limitations. We have included both z-selected, as well as Ks-selected objects, yielding a unique, self-consistent catalog. The largest fraction of the sample is 90% complete at z 26 or Ks 23.8 (AB scale). Finally, we cross-correlated our data with all the spectroscopic catalogs available to date, assigning a spectroscopic redshift to more than 1000 sources. Results. The final catalog is made up of 14 847 objects, at least 72 of which are known stars, 68 are AGNs, and 928 galaxies with spectroscopic redshift (668 galaxies with reliable redshift determination). We applied our photometric redshift code to this data set, and the comparison with the spectroscopic sample shows that the quality of the resulting photometric redshifts is excellent, with an average scatter of only 0.06. The full catalog, which we named GOODS-MUSIC (MUltiwavelength Southern Infrared Catalog), including the spectroscopic information, is made publicly available, together with the software specifically designed to this end.
Aims. We attempt to compile a complete, mass-selected sample of galaxies with low specific star-formation rates, and compare their properties with theoretical model predictions. Methods. We use the ...$f(24~{\rm \mu m})/f(K)$ flux ratio and the SED fitting to the $0.35{-}8.0~\mu$m spectral distribution, to select quiescent galaxies from $z\simeq 0.4$ to $z\simeq 4$ in the GOODS-MUSIC sample. Our observational selection can be translated into thresholds in specific star-formation rate $\dot{M}/M_*$, which can be compared with theoretical predictions. Results. In the framework of the well-known global decline in quiescent galaxy fraction with redshift, we find that a non-negligible fraction ${\simeq} 15{-}20\%$ of massive galaxies with low specific star-formation rate exists up to $z\simeq 4$, including a tail of “red and dead” galaxies with $\dot{M}/M_*<10^{-11}$ yr-1. Theoretical models vary to a large extent in their predictions for the fraction of galaxies with low specific star-formation rates, but are unable to provide a global match to our data.
We report on the evolution of the number density and size of early-type galaxies (ETGs) from z ~ 2 to z ~ 0. We select a sample of 563 massive (M > 1010 M ), passively evolving (specific star ...formation rate <10--2 Gyr--1), and morphologically spheroidal galaxies at 0 < z < 2.5, using the panchromatic photometry and spectroscopic redshifts available in the Great Observatories Origins Deep Surveys fields. We combine Advanced Camera for Surveys and Wide Field Camera 3 Hubble Space Telescope images to study the morphology of our galaxies in their optical rest frame in the entire 0 < z < 2.5 range. We find that throughout the explored redshift range the passive galaxies selected with our criteria have weak morphological K-correction, with size being slightly smaller in the optical than in the UV rest frame (by ~20% and ~10% at z > 1.2 and z < 1.2, respectively). We measure a significant evolution of the mass-size relation of ETGs, with a fractional increment that is almost independent of the stellar mass. ETGs formed at z > 1 appear to be preferentially small, and the evolution of the mass-size relation at z < 1 is driven by both the continuous size growth of the compact galaxies and the appearance of new ETGs with large sizes. We also find that the number density of all passive ETGs increases rapidly, by a factor of five, from z ~ 2 to z ~ 1, and then more mildly by another factor of 1.5 from z ~ 1 to z ~ 0. We interpret these results as evidence that the bulk of the ETGs are formed at 1 < z < 3 through a mechanism that leaves very compact remnants. At z < 1 the compact ETGs grow gradually in size, becoming normal-size galaxies, and at the same time new ETGs with normal-large sizes are formed.
On 2009 April 6, the Central Apennines were hit by an Mw = 6.3 earthquake. The region had been shaken since 2008 October by seismic activity that culminated in two foreshocks with Mw > 4, 1 week and ...a few hours before the main shock. We computed seismic moment tensors for 26 events with Mw between 3.9 and 6.3, using the Regional Centroid Moment Tensor (RCMT) scheme. Most of these source parameters have been computed within 1 hr after the earthquake and rapidly revised successively. The focal mechanisms are all extensional, with a variable and sometimes significant strike-slip component. This geometry agrees with the NE–SW extensional deformation of the Apennines, known from previous seismic and geodetic observations. Events group into three clusters. Those located in the southern area have larger centroid depths and a wider distribution of T-axis directions. These differences suggest that towards south a different fault system was activated with respect to the SW-dipping normal faults beneath L'Aquila and more to the north.
We show how the observed bimodality in the color distribution of galaxies can be explained in the framework of the hierarchical clustering picture in terms of the interplay between the properties of ...the merging histories and the feedback/star formation processes in the progenitors of local galaxies. Using a semianalytic model of hierarchical galaxy formation, we compute the color distributions of galaxies with different luminosities and compare them with the observations. Our fiducial model matches the fundamental properties of the observed distributions, namely: (1) the distribution of objects brighter than M sub(r) -18 is clearly bimodal, with a fraction of red objects increasing with luminosity; (2) for objects brighter than M sub(r) -21, the color distribution is dominated by red objects with color u - r - 2.2-2.4; (3) the spread on the distribution of the red population is smaller than that of the blue population; (4) the fraction of red galaxies is larger in denser environments, even for low-luminosity objects; and (5) the bimodality in the distribution persists up to z - 1.5. We discuss the role of the different physical processes included in the model in producing the above results.
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