Marine reserves are assumed to protect a wide range of species from deleterious effects stemming from exploitation. However, some species, due to their ecological characteristics, may not respond ...positively to protection. Very little is known about the effects of life history and ecological traits (e.g., mobility, growth, and habitat) on responses of fish species to marine reserves. Using 40 data sets from 12 European marine reserves, we show that there is significant variation in the response of different species of fish to protection and that this heterogeneity can be explained, in part, by differences in their traits. Densities of targeted size-classes of commercial species were greater in protected than unprotected areas. This effect of protection increased as the maximum body size of the targeted species increased, and it was greater for species that were not obligate schoolers. However, contrary to previous theoretical findings, even mobile species with wide home ranges benefited from protection: the effect of protection was at least as strong for mobile species as it was for sedentary ones. Noncommercial bycatch and unexploited species rarely responded to protection, and when they did (in the case of unexploited bentho-pelagic species), they exhibited the opposite response: their densities were lower inside reserves. The use of marine reserves for marine conservation and fisheries management implies that they should ensure protection for a wide range of species with different life-history and ecological traits. Our results suggest this is not the case, and instead that effects vary with economic value, body size, habitat, depth range, and schooling behavior.
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BFBNIB, FZAB, GIS, IJS, INZLJ, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZRSKP
The formation history of elliptical galaxies De Lucia, Gabriella; Springel, Volker; White, Simon D. M. ...
Monthly Notices of the Royal Astronomical Society,
February 2006, Volume:
366, Issue:
2
Journal Article
Peer reviewed
Open access
ABSTRACT
We take advantage of the largest high‐resolution simulation of cosmic structure growth ever carried out – the Millennium Simulation of the concordance Λ cold dark matter (CDM) cosmogony – to ...study how the star formation histories, ages and metallicities of elliptical galaxies depend on environment and on stellar mass. We concentrate on a galaxy formation model which is tuned to fit the joint luminosity/colour/morphology distribution of low‐redshift galaxies. Massive ellipticals in this model have higher metal abundances, older luminosity‐weighted ages and shorter star formation time‐scales, but lower assembly redshifts, than less massive systems. Within clusters the typical masses, ages and metal abundances of ellipticals are predicted to decrease, on average, with increasing distance from the cluster centre. We also quantify the effective number of progenitors of ellipticals as a function of present stellar mass, finding typical numbers below two for M* < 1011 M⊙, rising to approximately five for the most massive systems. These findings are consistent with recent observational results that suggest ‘down‐sizing’ or ‘antihierarchical’ behaviour for the star formation history of the elliptical galaxy population, despite the fact that our model includes all the standard elements of hierarchical galaxy formation and is implemented on the standard, ΛCDM cosmogony.
The estimate of stellar metallicities (
Z
*
) of high-
z
galaxies are of paramount importance in order to understand the complexity of dust effects and the reciprocal interrelations among stellar ...mass, dust attenuation, stellar age, and metallicity. Benefiting from uniquely deep far-UV spectra of > 500 star-forming galaxies at redshifts 2 <
z
< 5 extracted from the VANDELS survey and stacked in bins of stellar mass (
M
*
) and UV continuum slope (
β
), we estimate their stellar metallicities
Z
*
from stellar photospheric absorption features at 1501 and 1719 Å, which are calibrated with Starburst99 models and are largely unaffected by stellar age, dust, IMF, nebular continuum, or interstellar absorption. Comparing them to photometric-based spectral slopes in the 1250–1750 Å range, we find that the stellar metallicity increases by ∼0.5 dex from
β
∼ −2 to
β
∼ −1 (1 ≲
A
1600
≲ 3.2), and a dependence with
β
holds at fixed UV absolute luminosity
M
UV
and stellar mass up to ∼10
9.65
M
⊙
. As a result, metallicity is a fundamental ingredient for properly rescaling dust corrections based on
M
UV
and
M
*
. Using the same absorption features, we analyzed the mass-metallicity relation (MZR), and find it to be consistent with the previous VANDELS estimation based on a global fit of the FUV spectra. Similarly, we do not find a significant evolution between
z
∼ 2 and
z
∼ 3.5. Finally, the slopes of our MZR and
Z
*
−
β
relation are in agreement with the predictions of well-studied semi-analytic models (SAM) of galaxy formation, while some tensions remain concerning the absolute metallicity normalization. The relation between the UV slope and stellar metallicity is fundamental to the exploitation of large volume surveys with next-generation telescopes and for the physical characterization of galaxies in the first billion years of our Universe.
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We present a detailed mass reconstruction and a novel study on the substructure properties in the core of the Cluster Lensing And Supernova survey with Hubble (CLASH) and Frontier Fields galaxy ...clusterMACS J0416.1-2403. We reproduce the measured positions of a set of 30 multiple images with a remarkable median offset of only 0.3 by means of a comprehensive strong lensing model comprised of two cluster dark-matter halos, represented by cored elliptical pseudo-isothermal mass distributions, and the cluster member components, parameterized with dual pseudo-isothermal total mass profiles. We investigate the galaxy contribution, both in terms of total and stellar mass, to the total mass budget of the cluster. Our findings of the location and shape of the cluster dark-matter halo density profiles and on the cluster substructures provide intriguing tests of the assumed collisionless, cold nature of dark matter and of the role played by baryons in the process of structure formation.
We present a simulation of the cosmic evolution of the atomic and molecular phases of the cold hydrogen gas in about 3 X 107 galaxies, obtained by postprocessing the virtual galaxy catalog produced ...by De Lucia & Blaizot on the Millennium Simulation of cosmic structure. Our method uses a set of physical prescriptions to assign neutral atomic hydrogen (H I) and molecular hydrogen (H2) to galaxies, based on their total cold gas masses and a few additional galaxy properties. These prescriptions are specially designed for large cosmological simulations, where, given current computational limitations, individual galaxies can only be represented by simplistic model objects with a few global properties. Our recipes allow us to (1) split total cold gas masses between H I, H2, and helium, (2) assign realistic sizes to both the H I and H2 disks, and (3) evaluate the corresponding velocity profiles and shapes of the characteristic radio emission lines. The results presented in this paper include the local H I and H2 mass functions, the CO luminosity function, the cold gas mass-diameter relation, and the Tully-Fisher relation (TFR), which all match recent observational data from the local universe. We also present high-redshift predictions of cold gas diameters and the TFR, both of which appear to evolve markedly with redshift.
We investigate the galaxy population in simulated protocluster regions using a semi-analytic model of galaxy formation, coupled to merger-trees extracted from N-body simulations. We select the most ...massive clusters at redshift z = 0 from our set of simulations, and follow their main progenitors back in time. The analysis shows that protocluster regions are dominated by central galaxies and their number decreases with time as many become satellites, clustering around the central object. In agreement with observations, we find an increasing velocity dispersion with cosmic time, the increase being faster for satellites. The analysis shows that protoclusters are very extended regions, ≳20 Mpc at z ≳ 1. The fraction of galaxies in protocluster regions that are not progenitor of cluster galaxies varies with redshift, stellar mass and area considered. It is about 20–30 per cent for galaxies with stellar mass ∼109 M⊙, while negligible for the most massive galaxies considered. Nevertheless, these objects have properties similar to those of progenitors. We investigate the building-up of the passive sequence in clusters, and find that their progenitors are on average always active at any redshift of interest of protoclusters. The main mechanism which quenches their star formation is the removal of the hot gas reservoir at the time of accretion. The later galaxies are accreted (become satellite), and the more the cold gas available, the longer the time spent as active. Central galaxies are active over all redshift range considered, although a non-negligible fraction of them become passive at redshift z < 1, due to strong feedback from active galactic nuclei.
We present new constraints on the relationship between galaxies and their host dark matter haloes, measured from the location of the peak of the stellar-to-halo mass ratio (SHMR), up to the most ...massive galaxy clusters at redshift z ∼ 0.8 and over a volume of nearly 0.1 Gpc3. We use a unique combination of deep observations in the CFHTLenS/VIPERS field from the near-UV to the near-IR, supplemented by ∼60 000 secure spectroscopic redshifts, analysing galaxy clustering, galaxy–galaxy lensing and the stellar mass function. We interpret our measurements within the halo occupation distribution (HOD) framework, separating the contributions from central and satellite galaxies. We find that the SHMR for the central galaxies peaks at
$M_{\rm h, peak} = 1.9^{+0.2}_{-0.1}\times 10^{12}{\,{\rm M}_{{\odot }}}$
with an amplitude of 0.025, which decreases to ∼0.001 for massive haloes (
${{{M}_{\rm h}}}> 10^{14} {\,{\rm M}_{{\odot }}}$
). Compared to central galaxies only, the total SHMR (including satellites) is boosted by a factor of 10 in the high-mass regime (cluster-size haloes), a result consistent with cluster analyses from the literature based on fully independent methods. After properly accounting for differences in modelling, we have compared our results with a large number of results from the literature up to z = 1: we find good general agreement, independently of the method used, within the typical stellar-mass systematic errors at low to intermediate mass (
${{{M}_{\rm \star }}}<10^{11} {\,{\rm M}_{{\odot }}}$
) and the statistical errors above. We have also compared our SHMR results to semi-analytic simulations and found that the SHMR is tilted compared to our measurements in such a way that they over- (under-) predict star formation efficiency in central (satellite) galaxies.
In this paper, we carry out a detailed analysis of the performance of two different methods to identify the diffuse stellar light in cosmological hydrodynamical simulations of galaxy clusters. One ...method is based on a dynamical analysis of the stellar component, which separates the brightest central galaxy (BCG) from the stellar component not gravitationally bound to any galaxy, what we call 'diffuse stellar component' (DSC). The second method is closer to techniques commonly employed in observational studies. We generate mock images from simulations, and assume a standard surface brightness limit (SBL) to disentangle the BCG from the intra-cluster light (ICL). Both the dynamical method and the method based on the SBL criterion are applied to the same set of hydrodynamical simulations for a large sample of about 80 galaxy clusters. We analyse two sets of radiative simulations: a first set includes the effect of cooling, star formation, chemical enrichment and galactic outflows triggered by supernova feedback (CSF set); a second one also includes the effect of thermal feedback from active galactic nuclei triggered by gas accretion on to supermassive black holes (AGN set). We find significant differences between the ICL and DSC fractions computed with the two corresponding methods, which amounts to about a factor of 2 for the AGN simulations, and a factor of 4 for the CSF set. We also find that the inclusion of AGN feedback boosts the DSC and ICL fractions by a factor of 1.5-2, respectively, while leaving the BCG+ICL and BCG+DSC mass fraction almost unchanged. The sum of the BCG and DSC mass stellar mass fraction is found to decrease from ∼80 per cent in galaxy groups to ∼60 per cent in rich clusters, thus in excess of that found from observational analysis. We identify the average SBLs that yield the ICL fraction from the SBL method close to the DSC fraction from the dynamical method. These SBLs turn out to be brighter in the CSF than in the AGN simulations. This is consistent with the finding that AGN feedback makes BCGs to be less massive and with shallower density profiles than in the CSF simulations. The BCG stellar components, as identified by both methods, are slightly older and more metal-rich than the stars in the diffuse component. Relaxed clusters have somewhat higher stellar mass fractions in the diffuse component. The metallicity and age of both the BCG and diffuse components in relaxed clusters are also richer in metals and older.
Temporal trends in the recovery of exploited species in marine protected areas (MPAs) are useful for a proper assessment of the efficacy of protection measures. The effects of protection on the fish ...assemblages of the sublittoral rocky reefs in the "Penisola del Sinis-Isola di Mal di Ventre" MPA (W. Sardinia, Italy) were evaluated using a multi-year series of data. Four surveys, conducted 7, 10, 13 and 15 years after the area was designated as an MPA and carried out in the period spanning June and July, were used to estimate the abundance and biomass of commercial species. The surveys were carried out in zones with decreasing levels of fishing restrictions within the MPA (zones A, B, C) and in unprotected zones (OUT1 and OUT2), and underwater video visual census techniques were used. Protected zones only occasionally showed higher levels of abundance or biomass, and the trajectories of those metrics were not consistent across the years. In addition, the zone with the highest level of protection (zone A) never presented levels of abundance and biomass higher than those in zones B and C. This study shows that even 15 years after designation, protection has had no appreciable effect in the MPA studied. It is argued that this is emblematic of several shortcomings in the planning, regulation and enforcement frameworks of the MPA.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We use semi-analytic techniques to study the formation and evolution of brightest cluster galaxies (BCGs). We show the extreme hierarchical nature of these objects and discuss the limitations of ...simple ways to capture their evolution. In a model where cooling flows are suppressed at late times by active galactic nucleus (AGN) activity, the stars of BCGs are formed very early (50 per cent at z∼ 5, 80 per cent at z∼ 3) and in many small galaxies. The high star formation rates in these high-z progenitors are fuelled by rapid cooling, not by merger-triggered starbursts. We find that model BCGs assemble surprisingly late: half their final mass is typically locked up in a single galaxy after z∼ 0.5. Because most of the galaxies accreted on to BCGs have little gas content and red colours, late mergers do not change the apparent age of BCGs. It is this accumulation of a large number of old stellar populations – driven mainly by the merging history of the dark matter halo itself – that yields the observed homogeneity of BCG properties. In the second part of the paper, we discuss the evolution of BCGs to high redshifts, from both observational and theoretical viewpoints. We show that our model BCGs are in qualitative agreement with high-z observations. We discuss the hierarchical link between high-z BCGs and their local counterparts. We show that high-z BCGs belong to the same population as the massive end of local BCG progenitors, although they are not in general the same galaxies. Similarly, high-z BCGs end up as massive galaxies in the local Universe, although only a fraction of them are actually BCGs of massive clusters.
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