abstract: This work examines star formation in the debris associated with collisions of dwarf and spiral galaxies. While the spectacular displays of major mergers are famous (e.g., NGC 4038/9, ``The Antennae''), equal mass galaxy mergers are relatively rare compared to minor mergers (mass ratio <0.3) Minor mergers are less energetic than major mergers, but more common in the observable universe and, thus, likely played a pivotal role in the formation of most large galaxies. Centers of mergers host vigorous star formation from high gas density and turbulence and are surveyed over cosmological distances. However, the tidal debris resulting from these mergers have not been well studied. Such regions have large reservoirs of gaseous material that can be used as fuel for subsequent star formation but also have lower gas density. Tracers of star formation at the local and global scale have been examined for three tidal tails in two minor merger systems. These tracers include young star cluster populations, H-alpha, and [CII] emission. The rate of apparent star formation derived from these tracers is compared to the gas available to estimate the star formation efficiency (SFE). The Western tail of NGC 2782 formed isolated star clusters while massive star cluster complexes are found in the UGC 10214 (``The Tadpole'') and Eastern tail of NGC 2782. Due to the lack of both observable CO and [CII] emission, the observed star formation in the Western tail of NGC 2782 may have a low carbon abundance and represent only the first round of local star formation. While the Western tail has a normal SFE, the Eastern tail in the same galaxy has an low observed SFE. In contrast, the Tadpole tidal tail has a high observed star formation rate and a corresponding high SFE. The low SFE observed in the Eastern tail of NGC 2782 may be due to its origin as a splash region where localized gas heating is important. However, the other tails may be tidally formed regions where gravitational compression likely dominates and enhances the local star formation. / Dissertation/Thesis / Ph.D. Astrophysics 2013

The Generalised Star-Height Problem is an open question in the field of formal language theory that concerns a measure of complexity on the class of regular languages; specifically, it asks whether or not there exists an algorithm to determine the generalised star-height of a given regular language. Rather surprisingly, it is not yet known whether there exists a regular language of generalised star-height greater than one. Motivated by a theorem of Thérien, we first take a combinatorial approach to the problem and consider the languages in which every word features a fixed contiguous subword an exact number of times. We show that these languages are all of generalised star-height zero. Similarly, we consider the languages in which every word features a fixed contiguous subword a prescribed number of times modulo a fixed number and show that these languages are all of generalised star-height at most one. Using these combinatorial results, we initiate work on identifying the generalised star-height of the languages that are recognised by finite semigroups. To do this, we establish the generalised star-height of languages recognised by Rees zero-matrix semigroups over nilpotent groups of classes zero and one before considering Rees zero-matrix semigroups over monogenic semigroups. Finally, we explore the generalised star-height of languages recognised by finite groups of a given order. We do this through the use of finite state automata and 'count arrows' to examine semidirect products of the form A x Zr where A is an abelian group and Zr is the cyclic group of order r.

We report the discovery and constrain the physical conditions of the interstellar medium of the highest-redshift millimeter-selected dusty star-forming galaxy to date, SPT-S J031132-5823.4 (hereafter SPT0311-58), at z = 6.900 +/- 0.002. SPT0311-58 was discovered via its 1.4 mm thermal dust continuum emission in the South Pole Telescope (SPT)-SZ survey. The spectroscopic redshift was determined through an Atacama Large Millimeter/submillimeter Array 3 mm frequency scan that detected CO(6-5), CO(7-6), and [C I](2-1), and subsequently was confirmed by detections of CO(3-2) with the Australia Telescope Compact Array and[C II] with APEX. We constrain the properties of the ISM in SPT0311-58 with a radiative transfer analysis of the dust continuum photometry and the CO and [C I] line emission. This allows us to determine the gas content without ad hoc assumptions about gas mass scaling factors. SPT0311-58 is extremely massive, with an intrinsic gas mass of M-gas = 3.3 +/- 1.9 x 10(11) M-circle dot. Its large mass and intense star formation is very rare for a source well into the epoch of reionization.

We present a new study of the spatial distribution and ages of the star clusters in the Small Magellanic Cloud (SMC). To detect and estimate the ages of the star clusters we rely on the new fully automated method developed by Bitsakis et al. Our code detects 1319 star clusters in the central 18 deg(2) of the SMC we surveyed (1108 of which have never been reported before). The age distribution of those clusters suggests enhanced cluster formation around 240 Myr ago. It also implies significant differences in the cluster distribution of the bar with respect to the rest of the galaxy, with the younger clusters being predominantly located in the bar. Having used the same setup, and data from the same surveys as for our previous study of the LMC, we are able to robustly compare the cluster properties between the two galaxies. Our results suggest that the bulk of the clusters in both galaxies were formed approximately 300 Myr ago, probably during a direct collision between the two galaxies. On the other hand, the locations of the young (<= 50 Myr) clusters in both Magellanic Clouds, found where their bars join the H I arms, suggest that cluster formation in those regions is a result of internal dynamical processes. Finally, we discuss the potential causes of the apparent outside-in quenching of cluster formation that we observe in the SMC. Our findings are consistent with an evolutionary scheme where the interactions between the Magellanic Clouds constitute the major mechanism driving their overall evolution.

Living with Star Trek investigates the connections between Star Trek fandom and the Star Trek text. This study identifies and examines the American themes of utopia, community and self-improvement inherent within the fictional text which also form the thematic framework for letters written by fans to express their affection for the series. These letters represent a `network of support', whereby a community of fans is able to communicate with each other through written correspondence sent to producers, edited collections, and fan magazines. In talking about the series, fans confess and share intimate stories, often based around trauma or bereavement, and at the same time describe how Star Trek has played an important and inspirational part in their daily lives; Star Trek's utopian vision and communal spirit has given them the impetus to enact positive change. Drawing together the themes identified in the text and fan letters, the first half of the thesis examines Star Trek's use of history, narrative and myth to tell its futuristic stories. In particular, I examine how Star Trek has used the distinctive literary tradition of the Puritan American Jeremiad to create a didactic narrative that emphasises the attainment of utopia through communal effort and personal change. The second half of the thesis continues this inquiry by examining a range of letters that describe how fans are able to tap into the open nature of the Star Trek text and use it to fulfil needs and desires in their own daily lives. In particular, I stress how the letters are not just examples of fan affection but also represent a reciprocal relationship where fans can criticise and engage with the programme as well as use it as a form of motivation.

Målet med denna studie är att undersöka om det finns några principer för hur actionsekvenser är klippta och om utvecklingen av ny klippteknik ändrat på sättet man klipper actionsekvenser i Star Wars eller om man arbetar för att behålla och återskapa samma emotionella klippkänsla som i de äldre filmerna. Studien är genomförd i form av två stycken analysmetoder, den första metoden bygger på Berry Salt's analysmetod för att få ut statistik över hur actionsekvenserna är klippta, genom att se hur många klipp det är i en sekvens och dela antal klipp med tiden som sekvensen utspelar sig under, på så sätt får man ut en så kallad "average shot lenght" (ASL). Den andra metoden är en bildanalys där jag undersöker hur man har arbetat med dramaturgin och informationen man ger publiken. Undersökningens ramverk bygger på Dancygers  (2011) kriterier för en actionssekvens och det innebär i korthet att en actionsekvens ska innehålla identifikation, excitation, en konfilkt och intensifiering för att en actionsekvens ska räknas som en actionsekvens. Undersökningens resultat visar på att de actionsekvenser som ingått i studien skiljer sig åt. Men det finns en del genomgående principer som gäller samtliga sekvenser och de är att varje bild ska ge information om var man befinner sig, vad det är som händer och vad som kommer att hända i nästa bild. Ur min studie kan man se att sekvenserna skiljer sig i tid, antal klipp och hur lång ASL varje sekvens har. Med hjälp av klippningen ska man ge publiken den information som dem behöver för att förstå berättelsen som projiceras framför dom. Utgår man ifrån hur Star Wars filmerna är klippta i en bransch som utvecklats under 40 år, då ser man hur man använt sig av en liknande klippteknik för att fånga publikens uppmärksamhet, föra berättelsen framåt och ge publiken rätt information.

The young moving groups are collections of nearby (<200 pc), young (5-150 Myr) pre-main sequence stars; these stars offer us one of the best opportunities to characterise stellar multiplicity, sub-stellar phenomena, disc evolution and planet formation. Here we present results from a series of multiplicity studies aimed at producing comprehensive multiplicity statistics of the young moving groups. The aim was to compare the derived statistics of the young moving groups to other populations in order to investigate whether the abundance and properties of multiple systems are environment independent. We have combined high-resolution spectroscopy, AO-imaging and direct imaging to identify and characterise multiple systems across a huge range of orbital periods (1- 10e10 day). The observational techniques also allow us to constrain the abundance of multiple systems in these populations by calculating detection limits. We found many similarities (frequency of spectroscopic binaries; frequency, mass-ratio and physical separation of visual binaries) between the young moving groups and both younger and older regions, for multiple systems with physical separations smaller than 1000 au. We did, however, identify a significant number of new wide (>1000 au) companions. We reconciled the apparent excess of wide binary systems, when compared to the field population, by arguing that the wide systems are weakly bound and most likely decaying. By comparing the multiplicity statistics in one particular moving group we showed that the dynamical evolution of non-hierarchical protostars could lead to the population of wide binaries we can observe today. Our results indicate that the majority of low-mass stars form in small groups with 3 or 4 components that undergo significant dynamical evolution. The multiplicity properties of the young nearby moving groups are statistically similar to many other populations, supporting the environment-independent formation of multiple systems.

Understanding the time evolution of the star formation in the Universe is one of the main aims of observational astronomy. Since a significant portion of the UV starlight is being absorbed by dust and re-emitted in the IR, we need to understand both of those regimes to properly describe the cosmic star formation history. In UV, the depth and the resolution of the data permits calculations of the star formation rate densities out to very high redshifts (z ∼ 8 − 9). In IR however, the large beam sizes and the relatively shallow data limits these calculations to z ∼ 2. In this thesis, I explore the SMA and PdBI high-resolution follow-up of 30 bright sources originally selected by AzTEC and LABOCA instruments at 1.1 mm and 870 μm respectively in conjunction with the SCUBA-2 Cosmology Legacy Survey (S2CLS) deep COSMOS and wide UDS maps, where 106 and 283 sources were detected, with the signal-to-noise ratio of > 5 and > 3.5 at 850 μm respectively. I find that the (sub)mm-selected galaxies reside and the mean redshifts of ¯z ≃ 2.5±0.05 with the exception of the brightest sources which seem to lie at higher redshifts (¯z ≃ 3.5 ± 0.2), most likely due to the apparent correlation of the (sub)mm flux with redshift, where brighter sources tend to lie at higher redshifts. Stellar masses, M⋆, and star formation rates, SFRs, were found (M⋆ & 1010M⊙ and SFR & 100M⊙ yr−1) and used to calculate the specific SFRs. I determine that the (sub)mm-selected sources mostly lie on the high-mass end of the star formation ‘main-sequence’ which makes them a high-mass extension of normal star forming galaxies. I also find that the specific SFR slightly evolves at redshifts 2−4, suggesting that the efficiency of the star formation seems to be increasing at these redshifts. Using the S2CLS data, the bolometric IR luminosity functions (IR LFs) were found for a range of redshifts z = 1.2 − 4.2 and the contribution of the SMGs to the total star formation rate density (SFRD) was calculated. The IR LFs were found to evolve out to redshift ∼ 2.5. The star formation activity in the Universe was found to peak at z ≃ 2 followed by a slight decline. Assuming the IR to total SFRD correction found in the literature the SFRD found in this work closely follows the best-fitting function of Madau & Dickinson (2014).

We present our new, fully automated method to detect and measure the ages of star clusters in nearby galaxies, where individual stars can be resolved. The method relies purely on statistical analysis of observations and Monte-Carlo simulations to define stellar overdensities in the data. It decontaminates the cluster color-magnitude diagrams and, using a revised version of the Bayesian isochrone fitting code of Ramirez-Siordia et al., estimates the ages of the clusters. Comparisons of our estimates with those from other surveys show the superiority of our method to extract and measure the ages of star clusters, even in the most crowded fields. An application of our method is shown for the high-resolution, multiband imaging of the Large Magellanic Cloud. We detect 4850 clusters in the 7 deg(2) we surveyed, 3451 of which have not been reported before. Our findings suggest multiple epochs of star cluster formation, with the most probable occurring similar to 310 Myr ago. Several of these events are consistent with the epochs of the interactions among the Large and Small Magellanic Clouds, and the Galaxy, as predicted by N-body numerical simulations. Finally, the spatially resolved star cluster formation history may suggest an inside-out cluster formation scenario throughout the LMC, for the past 1 Gyr.

The process of massive star formation greatly influences its surroundings through their outflows, vast UV output and shocks from their supernova death. They form at great distances from the Earth, enshrouded by dust and gas and have relatively short lifetimes. Astrophysical masers which form in these environments may act as locators of the star forming regions. The aim of this thesis is to study massive star formation using masers to probe these regions. The three main masers used in this thesis are the Class I and Class II methanol masers and the 6035 MHz ex-OH maser. The methanol masers are divided into two groups, Class I and Class II, based on their distance from a central source. The Class I masers are separated 1-2 pc from a central source, the central source is the star forming region. The Class II masers are associated close to a star forming source. They are often associated with a 6035 MHz ex-OH maser. The 6035 MHz ex-OH masers are less common than the 6668 MHz Class I methanol masers. They are often found at sites of the 6668 MHz Class I masers and 1665/7 MHz OH masers. This thesis presents two maser surveys, the Methanol Multibeam (MMB) survey and the Class I survey. The MMB survey is currently surveying the entire Galactic Plane for the 6668 MHz Class II methanol maser and the 6035 MHz ex-OH maser. Over 60\% of the survey in the Southern hemisphere is now complete using the Parkes telescope. Over 900 6668 MHz Class I methanol masers and 110 6035 MHz ex-OH masers have been detected, with all of these masers pinpoint the location of newly forming high mass stars. Follow up observations to determine the precise locations of the 6668 MHz methanol and 6035 MHz ex-OH masers are currently underway. The first ever unbiased Class I survey has observed 1 sq degree of the Galactic Plane for the 44 GHz Class I methanol masers using the Mopra telescope in Australia. The 44 GHz Class II methanol masers are hypothesised to be associated with the outflows of high mass stellar objects. The Class I survey has detected 25 44 GHz methanol masers, with 23 being new detections. A smaller survey for 36 GHz Class I masers was also conducted using the Mopra telescope centered on the region with the highest population of 44 GHz Class I masers.