Dust Evolution in Galaxy Cluster Simulations

Gaseous astrophysical media are splattered with solid agglomerates of molecules we call cosmic dust. Observations, in particular, are quite sensitive to dust properties such as composition and grain size. A need emerges to include dust within theoretical models of galaxy and galaxy cluster evolution. The INAF Astronomical Observatory of Trieste has developed a custom state-of-the-art cosmological N-body simulation of galaxy clusters based on the GADGET-3 code. Adding dust to this framework has not been feasible until now. Tracing the continuous grain size (or its discrete approximation) would burden with additional dimensions the already heavy particle structure and calculations, slowing down the runs to impractical rates. Dust was instead treated in post processing Granato+15, and its properties were assumed a priori. Then Hirashita15 proposed an approximation. Instead of computing the grain size continuum, he postulated that dust grains are divided between large (nominally 0.1 micrometers) and small (nominally 0.01 micrometers). He therefore adapted a comprehensive one-zone dust evolution model Asano+13 to this approximation. The binary grain size was selected for both observational and modeling reasons. When dust grains are produced in the envelopes of evolved stars or in supernova remnants, the dominant size is around 0.1 micrometers. In the ISM however, smaller dust is often just as prevalent or at times even dominant. This suggests that ISM evolution alters the grain size distribution. The phenomenon is captured in the modeling. Some processes are most efficient on one grain size over the other, or at times they have opposite effects on each size domain. We successfully adapted the Hirashita15 model to our custom GADGET-3 cosmological zoom-in simulation code, specifically we embedded the model so that each simulated gas particle will trace, on top of the usual gas elements obtained from stellar and supernovae yields, also small and large dust grains. We tested our method on four massive ( two M200 > 3 x 10e14 solar masses and two M200 > 10e15 solar masses) galaxy clusters. We also improved on previous dust production routines, which assumed a fixed dust condensation efficiency for each element. Instead, we form the two most representative dust species observed in nature: carbonaceous dust and astrophysical silicates, based on the element abundance produced by stellar or supernovae yields. At the peak of star formation activity at z > 3 when proto-clusters start to assemble, we find that the gas particles in our simulations are rich in dust, as expected. In order to test the impact of dust processes on dust growth other than stellar production, we ran simulations with dust production and destruction alone, without any grain-gas or grain-grain interactions. Dust is enhanced by a factor of two to three due to the processes occurring in the ISM. We investigated variations of the model through different runs to understand the interdependence of all the processes. We were able to reproduce the dust abundance to metallicity relations observed in local galaxies, however we under-produced the dust content of galaxy clusters around z < 0.5 observed by IRAS, Planck, and Herschel observations. This discrepancy can be mended only by assuming a lower sputtering efficiency, which erodes dust grains in the hot Intracluster Medium (ICM). The abundance of the two dust species, silicates and carbonaceous dust, is also slightly different from the Milky Way average, and from the common values adopted in calculations of dust reprocessing. These differences may have a strong impact on the predicted SED. This method lays the groundwork for further developments, such as cosmological simulations of single galaxies, or the refinement of radiative cooling routines and H2 catalysis on grain surfaces

Analytic Photometric Redshift Estimator for Type Ia Supernovae From the Large Synoptic Survey Telescope

Accurate and precise photometric redshifts (photo-z's) of Type Ia supernovae (SNe Ia) can enable the use of SNe Ia, measured only with photometry, to probe cosmology. This dramatically increases the science return of supernova surveys planned for the Large Synoptic Survey Telescope (LSST). In this paper we describe a significantly improved version of the simple analytic photo-z estimator proposed by Wang (2007) and further developed by Wang, Narayan, and Wood-Vasey (2007). We apply it to 55,422 simulated SNe Ia generated using the SNANA package with the LSST filters. We find that the estimated errors on the photo-z's, \sigma_{z_{phot}}/(1+z_{phot}), can be used as filters to produce a set of photo-z's that have high precision, accuracy, and purity. Using SN Ia colors as well as SN Ia peak magnitude in the i band, we obtain a set of photo-z's with 2 percent accuracy (with \sigma(z_{phot}-z_{spec})/(1+z_{spec}) = 0.02), a bias in z_{phot} (the mean of z_{phot}-z_{spec}) of -9 X 10^{-5}, and an outlier fraction (with |(z_{phot}-z_{spec})/(1+z_{spec})|>0.1) of 0.23 percent, with the requirement that \sigma_{z_{phot}}/(1+z_{phot})<0.01. Using the SN Ia colors only, we obtain a set of photo-z's with similar quality by requiring that \sigma_{z_{phot}}/(1+z_{phot})<0.007; this leads to a set of photo-z's with 2 percent accuracy, a bias in z_{phot} of 5.9 X 10^{-4}, and an outlier fraction of 0.32 percent.Comment: 10 pages, 8 figures, 2 tables. Revised version, accepted by MNRA

Assessing stellar yields in Galaxy chemical evolution: observational stellar abundance patterns

One-zone Galactic Chemical Evolution (GCE) models have provided useful insights on a great wealth of average abundance patterns in many environments, especially for the Milky Way and its satellites. However, the scatter of such abundance patterns is still a challenging aspect to reproduce. The leading hypothesis is that dynamics is a likely major source of the dispersion. In this work we test another hypothesis, namely that different assumptions on yield modeling may be at play simultaneously. We compare whether the abundance patterns spanned by the models are consistent with those observed in Galactic data. First, we test the performance of recent yield tabulations, and we show which of these tabulations best fit Galactic stellar abundances. We then group the models and test if yield combinations match data scatter and standard deviation. On a fixed Milky-Way-like parametrization of NuPyCEE, we test a selection of yields for the three dominant yield sets: low-to-intermediate mass stars, massive stars, and Type Ia supernovae. We also include the production of r-process elements by neutron star mergers. We explore the statistical properties spanned by such yields. We identify the differences and commonalities among yield sets. We define criteria that estimate whether an element is in agreement with the data, or if the model overestimates or underestimates it in various redshift bins. While it is true that yields are a major source of uncertainty in GCE models, the scatter of abundances in stellar spectra cannot be explained by a simple averaging of runs across yield prescriptions.Comment: 22 pages, 19 figures, accepted for publication in MNRA

BASIC PRINCIPLES OF “COLLABORATIVE LEARNING”

The purpose of this article is to give a general overview on the basic principles and the implementation of one of the most recent learning techniques such as “Collaborative Learning”. More than thirty years on, it is interesting to look at the legacy of the communicative approach and to observe how current practice has been affected by its basic principles. It has become a popular approach to the organization of the classroom around the world and recently in Albania as well. Collaborative Learning, and its Techniques (also referred to as CoLTs) pay an important role in the learning process as a social activity. This article is designed to discuss the “What” (definition), “Why” (purpose), and “How” (manner) collaborative learning questions. The three of these questions will be answered and analyzed step by step in the following article

COPULAR VERBS IN ENGLISH AND ALBANIAN LANGUAGE

This paper aims to make a comparative study of copular verbs between two different linguistic systems, English and Albanian ones. The question of what the copula is, and whether it is part of the predicate or not, has been considered for years by English and Albanian linguists. As the etymology of its name suggests, the copula (from Latin copular 'to link') serves to link the predicate to the subject. Since the copula does not contribute lexical meaning of its own, those who argue that the copula is a verb often argue that it is a verb of a special sort, for example a verb empty of semantic or syntactic features. This research, also plays a crucial role in studying and analyzing the classification of copular verbs, taking into consideration their lexical meaning. Considering both languages, there are clauses which involve the juxtaposition of the subject and its complement, expressed by an adjective, noun or pronoun

The many tensions with dark-matter based models and implications on the nature of the Universe

(Abridged) Fundamental tensions between observations and dark-matter based cosmological models have emerged. This updated review has two purposes: to explore new tensions that have arisen in recent years, compounding the unresolved tensions from previous studies, and to use the shortcomings of the current theory to guide the development of a successful model. Tensions arise in view of the profusion of thin disk galaxies, the pronounced symmetrical structure of the Local Group of Galaxies, the common occurrence of planes of satellite systems, the El Gordo and Bullet galaxy clusters, significant matter inhomogeneities on scales much larger than 100 Mpc, and the observed rapid formation of galaxies and super-massive black holes at redshifts larger than 7. Given the nature of the tensions, the real Universe needs to be described by a model in which gravitation is effectively stronger than Einsteinian/Newtonian gravitation at accelerations below Milgrom's acceleration scale. The promising nuHDM model, anchored on Milgromian dynamics but keeping the standard expansion history with dark energy, solves many of the above tensions. However galaxy formation appears to occur too late in this model, model galaxy clusters reach too large masses, and the mass function of model galaxy clusters is too flat and thus top-heavy in comparison to the observed mass function. Classes of models that reassess inflation, dark energy and the role of the CMB should be explored.Comment: 58 pages, 9 figures, 291 references, based on invited presentation and to appear in the proceedings of Corfu2022: Workshop on Tensions in Cosmology, Corfu Sept. 7-12., 2022 (organisers: E. Saridakis, S. Basilakos, S. Capozziello, E. Di Valentino, O. Mena, S. Pan, J. Levi Said); replaced version contains updated citation

Type Ia Supernovae Selection and Forecast of Cosmology Constraints for the Dark Energy Survey

We present the results of a study of selection criteria to identify Type Ia supernovae photometrically in a simulated mixed sample of Type Ia supernovae and core collapse supernovae. The simulated sample is a mockup of the expected results of the Dark Energy Survey. Fits to the MLCS2k2 and SALT2 Type Ia supernova models are compared and used to help separate the Type Ia supernovae from the core collapse sample. The Dark Energy Task Force Figure of Merit (modified to include core collapse supernovae systematics) is used to discriminate among the various selection criteria. This study of varying selection cuts for Type Ia supernova candidates is the first to evaluate core collapse contamination using the Figure of Merit. Different factors that contribute to the Figure of Merit are detailed. With our analysis methods, both SALT2 and MLCS2k2 Figures of Merit improve with tighter selection cuts and higher purities, peaking at 98% purity.Comment: submitted to JCAP, 23 pages, 36 picture

Dust evolution in galaxy cluster simulations

We implement a state-of-the-art treatment of the processes affecting the production and Interstellar Medium (ISM) evolution of carbonaceous and silicate dust grains within SPH simulations. We trace the dust grain size distribution by means of a two-size approximation. We test our method on zoom-in simulations of four massive (M_{200} 65 3 7 10^{14} M_{ 99 }) galaxy clusters. We predict that during the early stages of assembly of the cluster at z 73 3, where the star formation activity is at its maximum in our simulations, the proto-cluster regions are rich in dusty gas. Compared to the case in which only dust production in stellar ejecta is active, if we include processes occurring in the cold ISM, the dust content is enhanced by a factor 2-3. However, the dust properties in this stage turn out to be significantly different from those observationally derived for the average Milky Way dust, and commonly adopted in calculations of dust reprocessing. We show that these differences may have a strong impact on the predicted spectral energy distributions. At low redshift in star-forming regions our model reproduces reasonably well the trend of dust abundances over metallicity as observed in local galaxies. However we underproduce by a factor of 2-3 the total dust content of clusters estimated observationally at low redshift, z 72 0.5 using IRAS, Planck, and Herschel satellites data. This discrepancy does not subsist by assuming a lower sputtering efficiency, which erodes dust grains in the hot intracluster medium