Reproducing the assembly of massive galaxies within the hierarchical cosmogony

In order to gain insight into the physical mechanisms leading to the formation of stars and their assembly in galaxies, we compare the predictions of the MOdel for the Rise of GAlaxies aNd Active nuclei (MORGANA) to the properties of K- and 850 micron-selected galaxies (such as number counts, redshift distributions and luminosity functions) by combining MORGANA with the spectrophotometric model GRASIL. We find that it is possible to reproduce the K- and 850 micron-band datasets at the same time and with a standard Salpeter IMF, and ascribe this success to our improved modeling of cooling in DM halos. We then predict that massively star-forming discs are common at z~2 and dominate the star-formation rate, but most of them merge with other galaxies within ~100 Myr. Our preferred model produces an overabundance of bright galaxies at z<1; this overabundance might be connected to the build-up of the diffuse stellar component in galaxy clusters, as suggested by Monaco et al. (2006), but a naive implementation of the mechanism suggested in that paper does not produce a sufficient slow-down of the evolution of these objects. Moreover, our model over-predicts the number of 10^{10}-10^{11} M_sun galaxies at z~1; this is a common behavior of theoretical models as shown by Fontana et al. (2006). These findings show that, while the overall build-up of the stellar mass is correctly reproduced by galaxy formation models, the ``downsizing'' trend of galaxies is not fully reproduced yet. This hints to some missing feedback mechanism in order to reproduce at the same time the formation of both the massive and the small galaxies.Comment: 14 pages; 11 figures; accepted for publication by MNRA

Camel welfare: survey on camel caretakers' perspectives

Animal welfare depends on caretakers' handling and management skills. The study aimed at gaining information on camel caretakers' backgrounds, their perceptions of welfare and management practices and at investigating associations with camel health and behavioural problems. The study was conducted at a camel market in Qatar and 49 caretakers were interviewed (29 questions). Caretakers were male, mainly from Sudan (91.7%; P&lt;0.001), and had mainly learned camel management from family members (81.6%; P&lt;0.001). Camels were mainly from Qatar, reared for milk, breeding or meat. The majority of the caretakers under 30 years took care of camels reared as breeding animals or for milk production (n=12, 75.0%), while the caretakers over 40 years took care of camels for dual-purposes (n=7, 46.7%; P&lt;0.05) or meat (n=4, 26.7%). Camels received rationed feed and water (87.6%, 53.1%, P&lt;0.001), and were dewormed regularly (96.8%, P&lt;0.001) but not vaccinated (72.9%; P&lt;0.001). Respondents experienced at least one camel with a behavioural (45.8%) and a health (87.8%) problem and associations between management practices and those problems were found. Behavioural problems were associated with the number of health problems, suggesting that sick camels tended to show behavioural modifications. Caretakers ranked their ability to recognise a camel in distress/pain as high, reporting that the first sign was a change in behaviour. The caretakers' understanding of animal welfare was, however, low, missing the overall meaning of the concept; most caretakers defined animal welfare according to only one (52.2%) welfare principle. Overall, early and appropriate treatment of camels with health and behavioural problems, an increased presence of veterinarians at camel farms, and education on camel behaviour and welfare are recommended

Camel welfare: survey on camel caretakers' perspectives

Animal welfare depends on caretakers’ handling and management skills. The study aimed at gaining information on camel caretakers’ backgrounds, their perceptions of welfare and management practices and at investigating associations with camel health and behavioural problems. The study was conducted at a camel market in Qatar and 49 caretakers were interviewed (29 questions). Caretakers were male, mainly from Sudan (91.7%; P&lt;0.001), and had mainly learned camel management from family members (81.6%; P&lt;0.001). Camels were mainly from Qatar, reared for milk, breeding or meat. The majority of the caretakers under 30 years took care of camels reared as breeding animals or for milk production (n=12, 75.0%), while the caretakers over 40 years took care of camels for dual-purposes (n=7, 46.7%; P&lt;0.05) or meat (n=4, 26.7%). Camels received rationed feed and water (87.6%, 53.1%, P&lt;0.001), and were dewormed regularly (96.8%, P&lt;0.001) but not vaccinated (72.9%; P&lt;0.001). Respondents experienced at least one camel with a behavioural (45.8%) and a health (87.8%) problem and associations between management practices and those problems were found. Behavioural problems were associated with the number of health problems, suggesting that sick camels tended to show behavioural modifications. Caretakers ranked their ability to recognise a camel in distress/pain as high, reporting that the first sign was a change in behaviour. The caretakers’ understanding of animal welfare was, however, low, missing the overall meaning of the concept; most caretakers defined animal welfare according to only one (52.2%) welfare principle. Overall, early and appropriate treatment of camels with health and behavioural problems, an increased presence of veterinarians at camel farms, and education on camel behaviour and welfare are recommended.Animal welfare depends on caretakers' handling and management skills. The study aimed at gaining information on camel caretakers' backgrounds, their perceptions of welfare and management practices and at investigating associations with camel health and behavioural problems. The study was conducted at a camel market in Qatar and 49 caretakers were interviewed (29 questions). Caretakers were male, mainly from Sudan (91.7%; P&lt;0.001), and had mainly learned camel management from family members (81.6%; P&lt;0.001). Camels were mainly from Qatar, reared for milk, breeding or meat. The majority of the caretakers under 30 years took care of camels reared as breeding animals or for milk production (n=12, 75.0%), while the caretakers over 40 years took care of camels for dual-purposes (n=7, 46.7%; P&lt;0.05) or meat (n=4, 26.7%). Camels received rationed feed and water (87.6%, 53.1%, P&lt;0.001), and were dewormed regularly (96.8%, P&lt;0.001) but not vaccinated (72.9%; P&lt;0.001). Respondents experienced at least one camel with a behavioural (45.8%) and a health (87.8%) problem and associations between management practices and those problems were found. Behavioural problems were associated with the number of health problems, suggesting that sick camels tended to show behavioural modifications. Caretakers ranked their ability to recognise a camel in distress/pain as high, reporting that the first sign was a change in behaviour. The caretakers' understanding of animal welfare was, however, low, missing the overall meaning of the concept; most caretakers defined animal welfare according to only one (52.2%) welfare principle. Overall, early and appropriate treatment of camels with health and behavioural problems, an increased presence of veterinarians at camel farms, and education on camel behaviour and welfare are recommended

Faint Lyman-Break galaxies as a crucial test for galaxy formation models

It has recently been shown that galaxy formation models within the LambdaCDM cosmology predict that, compared to the observed population, small galaxies (with stellar masses < 10^{11} M_sun) form too early, are too passive since z ~ 3 and host too old stellar populations at z=0. We then expect an overproduction of small galaxies at z > 4 that should be visible as an excess of faint Lyman-break galaxies. To check whether this excess is present, we use the MORGANA galaxy formation model and GRASIL spectro-photometric + radiative transfer code to generate mock catalogues of deep fields observed with HST-ACS. We add observational noise and the effect of Lyman-alpha emission, and perform color-color selections to identify Lyman-break galaxies. The resulting mock candidates have plausible properties that closely resemble those of observed galaxies. We are able to reproduce the evolution of the bright tail of the luminosity function of Lyman-break galaxies (with a possible underestimate of the number of the brightest i-dropouts), but uncertainties and degeneracies in dust absorption parameters do not allow to give strong constraints to the model. Besides, our model shows a clear excess with respect to observations of faint Lyman-break galaxies, especially of z_{850} ~ 27 V-dropouts at z ~ 5. We quantify the properties of these "excess" galaxies and discuss the implications: these galaxies are hosted in dark matter halos with circular velocities in excess of 100 km s^{-1}, and their suppression may require a deep re-thinking of stellar feedback processes taking place in galaxy formation.Comment: 17 pages, 13 figures, 1 table; accepted for publication by MNRA

Evaluating and Improving Semi-analytic modelling of Dust in Galaxies based on Radiative Transfer Calculations

The treatment of dust attenuation is crucial in order to compare the predictions of galaxy formation models with multiwavelength observations. Most past studies have either used simple analytic prescriptions or else full radiative transfer (RT) calculations. Here, we couple star formation histories and morphologies predicted by the semi-analytic galaxy formation model MORGANA with RT calculations from the spectrophotometric and dust code GRASIL to create a library of galaxy SEDs from the UV/optical through the far Infrared, and compare the predictions of the RT calculations with analytic prescriptions. We consider a low and high redshift sample, as well as an additional library constructed with empirical, non-cosmological star formation histories and simple (pure bulge or disc) morphologies. Based on these libraries, we derive fitting formulae for the effective dust optical depth as a function of galaxy physical properties such as metallicity, gas mass, and radius. We show that such fitting formulae can predict the V-band optical depth with a scatter smaller than 0.4 dex for both the low and high redshift samples, but that there is a large galaxy-to-galaxy scatter in the shapes of attenuation curves, probably due to geometrical variations, which our simple recipe does not capture well. However, our new recipe provides a better approximation to the GRASIL results at optical wavelength than standard analytic prescriptions from the literature, particularly at high redshift.Comment: 20 pages, 13 figures, 4 tables; accepted for publication by MNRA