Probing the cold phase of the interstellar medium and star formation in nearby galaxies

Properly measuring the spatial distribution of the star formation rate (SFR) in galaxies helps us to understand the driving forces for the star formation in galaxies, effects on their interstellar media (ISM), and their evolution. However, this is hindered by the uncertainties in estimating SFRs and calibrating the SFR prescriptions. These uncertainties are caused by not properly measuring the attenuation of light, probing large spatial scales, or averaging over large sample of galaxies. Additionally, the physical factors that set the efficiency whith which galaxies convert gas into stars (star formation efficiency; SFE), and their role in galactic evolution, are not yet fully understood. Variations in the SFE are difficult to disentangle from uncertainties of estimated SFRs. The main goal of this thesis is to use optical integral field unit (IFU) observations of nearby galaxies, in order to probe the cold phase of their ISM at sub-kpc scales. We aim to measure the attenuation, thus to properly estimate the SFRs and calibrate the SFR prescriptions. We also estimate variations of SFE across the disk of an interacting galaxy. Using IFU observations of the outskirts of the Andromeda galaxy (M31) at sub-kpc scales (from 10 pc to kpc), we derive the Balmer line attenuation. By comparing attenuation with the dust mass surface density, we derive the 3-dimensional spatial distribution of dust and ionized gas in M31. Our results indicate that the vertical dust/gas distribution from the central areas of nearby galaxies differs from the outskirts of M31. From this evidence, we hypothesize that the vertical dust/gas distribution in galactic disks varies as a function of the galactocentric distance. Following that, we use extinction corrected Balmer line emission as a reference SFR tracer in a combination with ultraviolet and near-infrared images, to calibrate hybrid SFR prescriptions. We find that the hybrid SFR prescriptions do not change with spatial scale or with the subtraction of a diffuse component. However, our SFR prescriptions observed in M31 differ from the prescriptions in the literature. This indicates that the SFR prescriptions are not universal and that they may vary with the inclination and the galactocentric radius, due to varying dust/gas distributions. Our IFU observations of the interacting galaxy NGC 2276 are used to investigate how the early phase of galactic interaction affects the ISM, and SFE across its disk. Although NGC 2276 shows a significant asymmetrically elevated SFR surface density, and asymmetric stellar distribution, it does not show an unusual gas phase metallicity gradient or shock ionization. On the other hand, we probed the SFE at sub-kpc scales (0.5 kpc) across NGC 2276's disk to trace the origin of its elevated and asymmetric SFR and found more than two orders of magnitude variation in SFE. This is significantly larger than what is seen in nearby galaxies. We speculate that this is caused by both tidal forces exerted from a neighboring galaxy and ram pressure affecting NGC 2276

Monte Carlo simulations of galaxy protoclusters in Cosmos Survey

Jata tj. skupovi galaksija su veliki virializirani skupovi galaksija. Galaksije doprinose oko 5% mase jata, unutar-klasterski medij oko 10% mase i tamna tvar do 85% mase. Te strukture su nastale iz protojata galaksija. Protojato je rani oblik jata sa manje galaksija i sa uočenom većom gustoćom broja galaksija u odnosu na ostale dijelove promatranog neba. Cilj ovog rada jest simuliranje protojata galaksija na različitim crvenim pomacima (z=2, 3, 4 i 5), pomoću Monte Carlo simulacije, prateći unaprijed definirane površinske profile protojata i uzimajući u obzir pogreške fotometrijskih crvenih pomaka (naspram spektroskopskih crvenih pomaka) specifičnih za COSMOS pregled neba. Simuliranjem 1,000 protojata različitih tipova (prema jatima potomcima ukupnih masa ≥ 10^15M , 3 - 10 x 10^14M⊙ i 1:37 - 3 x 10^14M⊙), kvantificirali smo karakteristike metode traženja protojata u COSMOS pregledu neba, poput kompletnosti (broj koji definira udio galaksija nakon izvedene metode traženja, naspram cijelog broja galaksija protojata), kontaminacije (broj koji definira udio galaksija na nebu koji ne pripada protojatu), gustoće broja (broj galaksija na povr šini neba) i efektivnog radijusa (radijus unutar kojeg se nalazi 68% mase protojata), te njihovo ponašanje za različite tipove protojata i crvene pomake. Također smo izveli metodu traženja protojata pomoću Voronoi dijagrama i metode određivanja ponašanja diferencijalnog viška gustoće (kojem je mjera δ_g) u ovisnosti o udaljenosti od središta protojata. Rezultati pokazuju da se kompletnost protojata ne mjenja u odnosu na crveni pomak, dok kontaminacija očekivano raste sa udaljenosti od središta protojata. Izračunati efektivni radijusi naših simuliranih protojata se slažu do na faktor 2 sa početnim efektivnim radijusima protojata, izračunatim u Chiang et al. (2013). Unatoč tom nepodudaranju, unutar naših efektivnih radijusa nalazi se 55-65% galaksija u protojatu, što je sukladno rezultatima Chiang et al. (2013). Objašnjenje za razlike među radijusima nalazimo u tome što u našim simulacijama nismo uzeli u obzir raspodjelu mase u protojatima. Pretpostavili smo da sve galaksije imaju istu masu, što može značajno utjecati na izračun efektivnog radijusa. Na kraju smo primijenili metode traženja protojata i metodu računanja efektivnog radijusa na postojeća protojata u COSMOS polju, na različitim crvenim pomacima.Galaxy clusters are large virialized collections of galaxies. Galaxies contribute about 5% to the mass of the cluster, the intracluster medium about 10% and the dark matter up to 85%. These structures are formed from galaxy protoclusters. A protocluster is an early type of cluster with fewer galaxies and an observed higher number density of galaxies, compared to other parts of the observed sky. The goal of this paper is to simulate galaxy protoclusters at different redshifts (z = 2, 3, 4 and 5), using Monte Carlo simulations, following the predefined surface profiles of the protoclusters and taking into account the errors of photometric redshifts (versus spectroscopic redshifts) specifically for the COSMOS survey. By simulating 1,000 different types of protoclusters (by the descendant clusters of the total masses ≥ 10^15M , 3 - 10 x 10^14M⊙ i 1:37 - 3 x 10^14M⊙), we quantified the characteristics of the search methods of protoclusters in the COSMOS sky survey, such as completeness (a number that defines the share of galaxies derived after search methods, compared to the total number of galaxies in the protocluster), contamination (a number that defines the share of galaxies in the sky that does not belong to the protocluster), number density (number of galaxies on the surface of the sky) and effective radius (radius within which there is 68% of the protocluster mass), and their behavior for different types of protoclusters and different redshifts. The results show that completeness of the protoclusters does not change compared to the redshift, while the contamination expectedly increases with distance from the centre of protoclusters. The calculated effective radii of our simulated protoclusters agree within a factor of 2 with the initial effective radii of protoclusters, calculated in Chiang et al. (2013). Despite this discrepancy within our effective radii, 55-65% of galaxies are in protoclusters, which is consistent with the results of Chiang et al. (2013). We believe that the differences between the radii are caused by the fact that our simulations do not take into account the distribution of the mass in the protoclusters. We assumed that all galaxies have the same mass, which can significantly affect the calculation of the effective radius. In the end we applied the search methods of protoclusters and the method of calculating the effective radius to existing protoclusters in COSMOS field, at different redshifts

Disruptive Business Model Innovation and Digital Transformation

Background: Innovating how organisations run their business is a strategic decision to create more value for customers using or consuming the product and/or service provided. In addition to the incentive of everybody embracing digital transformation, digital technologies, and digital innovation, which frame changes of operating business models today, disruptions, i.e., another incentive that occurs suddenly and impacts globally, all force businesses to adapt and change. Objectives: This research aims to provide a conceptual model that can be used for organisations to evaluate and propose feasible options for responding to disruptions that influence the businesses’ strategic innovation initiatives while assisting decision-makers in choosing the most appropriate option. Methods/Approach: Considering internal and external factors that influence digital transformation, the conceptual framework is designed to assess readiness and willingness to transform and create opportunities for future success digitally. Results: A conceptual framework was developed, tested, and demonstrated in a case study. The case study organisation rated positively the composition of steps to be perf readiness and willingness and choose the most feasible option to change. Conclusions: The digital environment and the influence of disruptions force organisations to change. The conceptual framework developed in this research helps the management choose the most feasible change option about the real as-is and the desired to-be state

GASP XXVII: Gas-phase metallicity scaling relations in disk galaxies with and without ram-pressure stripping

Exploiting the data from the GAs Stripping Phenomena in galaxies with MUSE (GASP) survey, we study the gas-phase metallicity scaling relations of a sample of 29 cluster galaxies undergoing ram-pressure stripping and of a reference sample of (16 cluster and 16 field) galaxies with no significant signs of gas disturbance. We adopt the PYQZ code to infer the mean gas metallicity at the effective radius and achieve a well-defined mass-metallicity relation (MZR) in the stellar mass range $10^{9.25}\le M_\star \le 10^{11.5}\,{\rm M_\odot}$ with a scatter of 0.12 dex. At any given mass, reference cluster and stripping galaxies have similar metallicities, while the field galaxies with $M_\star < 10^{10.25}\,{\rm M_\odot}$ show on average lower gas metallicity than galaxies in clusters. Our results indicate that at the effective radius the chemical properties of the stripping galaxies are independent of the ram-pressure stripping mechanism. Nonetheless, at the lowest masses we detect 4 stripping galaxies well above the common MZR that suggest a more complex scenario. Overall, we find signs of an anti-correlation between the metallicity and both the star formation rate and the galaxy size, in agreement with previous studies. No significant trends are instead found with the halo mass, clustercentric distance and local galaxy density in clusters. In conclusion, we advise a more detailed analysis of the spatially resolved gas metallicity maps of the galaxies, able to highlight effects of gas redistribution inside the disk due to the ram-pressure stripping.Comment: accepted for publication in ApJ, 24 pages, 21 figures, 2 table

Ultraviolet imaging observations of three jellyfish galaxies: Star formation suppression in the centre and ongoing star formation in stripped tails

Spiral galaxies undergo strong ram-pressure effects when they fall into the galaxy cluster potential. As a consequence, their gas is stripped to form extended tails within which star formation can happen, giving them the typical jellyfish appearance. The ultraviolet imaging observations of jellyfish galaxies provide an opportunity to understand ongoing star formation in the stripped tails. We report the ultraviolet observations of the jellyfish galaxies JW39, JO60, JO194 and compare with observations in optical continuum and $\mathrm{H}{\alpha}$. We detect knots of star formation in the disk and tails of the galaxies and find that their UV and H$\alpha$ flux are well correlated. The optical emission line ratio maps of these galaxies are used to identify for every region the emission mechanism, due to either star formation, LINER or a mix of the two phenomena. The star-forming regions in the emission line maps match very well with the regions having significant UV flux. The central regions of two galaxies (JW39, JO194) show a reduction in UV flux which coincides with composite or LINER regions in the emission line maps. The galaxies studied here demonstrate significant star formation in the stripped tails, suppressed star formation in the central regions and present a possible case of accelerated quenching happening in jellyfish galaxies.Comment: Accepted for publication in MNRA

Disruptive Business Model Innovation and Digital Transformation

Innovating how organisations run their business is a strategic decision to create more value for customers using or consuming the product and/or service provided. In addition to the incentive of everybody embracing digital transformation, digital technologies, and digital innovation, which frame changes of operating business models today, disruptions, i.e., another incentive that occurs suddenly and impacts globally, all force businesses to adapt and change

Challenges of Processes Simulation with Dynamic Batch Processing Activities

Business Process Management (BPM) often encompasses process improvements based on Information and Communication Technologies (ICT). Business processes simulation can be used as a tool for estimation of optimization parameters. Commercially available BPM tools in accordance with BPMN 2.0 support have built-in simulation features, which vary in the extent of support to advanced process simulation options. In this paper, we address dynamic batch processing activities as a challenge for BPM tools with simulation features and their dynamic impact on the executing activities. Further on, basic process scenarios examples were used to test and evaluate the capabilities of selected BPM tools, especially in relation to the Time Driven Activity Based Costing model (TD ABC model). The closing part of the paper deals with significant limitations of BPM tools in terms of supporting the batch processing activities, and the comparison with the TD ABC model simulation as a temporary solution to these problems. The main findings of this paper imply that contemporary BPM tools with BPMN 2.0 support still need to implement better options for handling simulation of dynamic batch processing activities

Two Orders of Magnitude Variation in the Star Formation Efficiency across the Premerger Galaxy NGC 2276

We present the first spatially resolved (∼0.5 kpc) measurements of the molecular gas depletion time τ depl across the disk of the interacting spiral galaxy NGC 2276, a system with an asymmetric morphology in various star formation rate (SFR) tracers. To estimate τ depl, we use new NOEMA observations of the 12CO(1-0) emission tracing the bulk molecular gas reservoir in NGC 2276, and extinction-corrected Hα measurements obtained with the PMAS/PPaK integral field unit for robust estimates of the SFR. We find a systematic decrease in τ depl of 1-1.5 dex across the disk of NGC 2276, with a further, abrupt drop in τ depl of ∼1 dex along the galaxy's western edge. The global τ depl in NGC 2776 is τdepl = 0.55 Gyr, consistent with literature measurements for the nearby galaxy population. Such a large range in τ depl on subkiloparsec scales has never previously been observed within an individual isolated or premerger system. When using a metallicity-dependent molecular gas conversion factor the variation decreases by 0.5 dex. We attribute the variation in τ depl to the influence of galactic-scale tidal forces and ram pressure on NGC 2276's molecular interstellar medium. Our observations add to the growing body of numerical and observational evidence that galaxy-galaxy interactions significantly modify the molecular gas properties and star-forming activity within galactic disks throughout the interaction, and not just during the final merger phase

Calibrating Star Formation Rate Prescriptions at Different Scales (10 pc-1 kpc) in M31

We calibrate commonly used star formation rate (SFR) prescriptions using observations in five kiloparsec-sized fields in the nearby galaxy Andromeda (M31) at 10 pc spatial resolution. Our observations at different scales enable us to resolve the star-forming regions and to distinguish them from non-star-forming components. We use extinction-corrected Ha from optical integral field spectroscopy as our reference tracer and have verified its reliability via tests. It is used to calibrate monochromatic and hybrid (H alpha+alpha xIR and far-UV+bxIR) SFR prescriptions, which use far-UV (GALEX), 22 mu m (Wide-field Infrared Survey Explorer), and 24 mu m (MIPS). Additionally, we evaluate other multiwavelength infrared tracers. Our results indicate that the SFR prescriptions do not change (in M31) with spatial scales or with subtraction of the diffuse component. For the calibration factors in the hybrid SFR prescriptions, we find a approximate to 0.2 and b approximate to 22 in M31, which are a factor of 5 higher than in the literature. As the fields in M31 exhibit high attenuation and low dust temperatures, lie at large galactocentric distances, and suffer from high galactic inclination compared to measurements in other galaxies, we propose that the fields probe a dust layer extended along the line of sight that is not directly spatially associated with star-forming regions. This (vertically) extended dust component increases the attenuation and alters the SFR prescriptions in M31 compared to literature measurements. We recommend that SFR prescriptions should be applied with caution at large galactocentric distances and in highly inclined galaxies, due to variations in the relative (vertical) distribution of dust and gas.The authors wish to kindly thank Alexia Lewis, who shared the maps of modeled FUV emission and star formation history in M31, and to Sarah Leslie for additional comments. T.N. and K.K. acknowledge grants SCHI 536/8-2 and KR 4598/1-2 from the DFG Priority Program 1573

GASP. XXII. The Molecular Gas Content of the JW100 Jellyfish Galaxy at z ∼ 0.05: Does Ram Pressure Promote Molecular Gas Formation?

Within the GASP survey, aimed at studying the effect of the ram-pressure stripping on the star formation quenching in cluster galaxies, we analyze here ALMA observations of the jellyfish galaxy JW100. We find an unexpected large amount of molecular gas (∼ 2.5 × 10 10 M), 30% of which is located in the stripped gas tail out to ∼35 kpc from the galaxy center. The overall kinematics of molecular gas is similar to the one shown by the ionized gas, but for clear signatures of double components along the stripping direction detected only out to 2 kpc from the disk. The line ratio r 21 has a clumpy distribution and in the tail can reach large values (≥ 1), while its average value is low (0.58 with a 0.15 dispersion). All these evidence strongly suggest that the molecular gas in the tail is newly born from stripped HI gas or newly condensed from stripped diffuse molecular gas. The analysis of interferometric data at different scales reveals that a significant fraction (∼ 40%) of the molecular gas is extended over large scales (≥ 8 kpc) in the disk, and this fraction becomes predominant in the tail (∼ 70%). By comparing the molecular gas surface density with the star formation rate surface density derived from the Hα emission from MUSE data, we find that the depletion time on 1 kpc scale is particularly large (5 − 10 Gyr) both within the ram-pressure disturbed region in the stellar disk, and in the complexes along the tail