Using data from the SCUBA Legacy Catalogue (850 µm) and Spitzer (3.6 - 70 µm), we explore dense cores in the Ophiuchus, Taurus, Perseus, Serpens, and Orion molecular clouds. In particular, we focus on identifying which cores host young stars while others remain starless. Understanding the nature of star formation and the influence of local environment will give us insight into several key properties, such as the origin of stellar mass. Here, we present starless and protostellar core mass functions (CMFs) for the five clouds. We develop a new method to discriminate starless from protostellar cores, using Spitzer colours and positions. We found best-fit slopes to the high-mass end of −1.26±0.20, −1.22±0.06, −0.95±0.20, and −1.85±0.53 for Ophiuchus, Taurus, Perseus, and Orion, respectively. We were unable to fit a slope to our fifth cloud, Serpens. Broadly, these slopes are consistent with the −1.35 power-law seen in the Salpeter IMF, but suggest some differences. We examined a variety of trends between these CMF shapes and their parent cloud properties, potentially finding a correlation between the high-mass slope and temperature. We also attempt to predict what future surveys with SCUBA-2 will detect in each of our clouds.

We investigate three separate topics associated with the formation and evolution of the stellar mass component in galaxy clusters. The work presented herein is based primarily on optical imaging and spectra taken with, respectively, the Canada-France-Hawaii Telescope and Gemini North/South. We confront the result from the optical data analysis with the results from the analysis of high-resolution X-ray data taken with the Chandra and XMM-Newton space observatories. Confirming earlier results, we find that 22% of brightest cluster galaxies (BCGs) show central inversions in their optical color profiles (blue-cores), indicative of recent star formation or AGN activity. Based on the extended sizes of the blue-core regions we favour recent star formation. Comparison with the host cluster central entropies (and other X-ray properties) demonstrates that the source of cold gas required to fuel the recent activity in BCG cores is direct condensation from the rapidly cooling intra-cluster medium. We measure the giant-to-dwarf ratio (GDR) of red sequence galaxies in a sample of 97 clusters to constrain its evolution over the redshift range 0.05 < z < 0.55. We find that the GDR is evolving and can be parameterized by GDR=(0.88 +/- 0.15)z+(0.44 +/- 0.03). We find that the intrinsic scatter in this relation is consistent with zero, after accounting for measurement error, Poisson noise and contributions from large-scale structure. After correcting for cluster mass effects we investigate the evolution of the individual dwarf and giant populations in order to probe the source of the observed GDR evolution. Beyond z=0.25 the GDR evolution is driven by an increase in the number of dwarfs (consistent with interpretations from the literature), however, below z=0.2 the GDR evolution is caused by a significant reduction in the number of giants. We interpret this a evidence for a significant number of major mergers in the giant population at late times. This is supported by the relatively short dynamical friction timescales for these galaxies. We use velocity-broadened stellar template models to fit the optical spectra of 19 BCGs in order to measure their the line-of-sight component of their central velocity dispersions (sigma). The sigma values are combined with previous measurements of effective radii re and effective surface brightness <I>e to investigate the properties of the BCG fundamental plane. We measure a BCG fundamental plane parameterized by log( re )= alpha log( sigma ) + beta log( <I>e ) + gamma, with best fit parameters alpha = 1.24 +/- 0.08, beta = -0.80 +/- 0.1 and gamma = (0.3 +/- 2.0)x10-4. We constrain the intrinsic scatter in this relation to be deltaint = 0.066 +/- 0.010 in re, consistent with previous measures of the scatter in the fundamental plane for regular cluster ellipticals. Comparing the slope parameters (alpha, beta) of the BCG FP to those from previous studies of the FP for regular cluster ellipticals, we find that there is no conclusive evidence for curvature in the unified FP. We use the sigma measurements to estimate the BCG dynamical masses Mdyn. Comparing these estimates with mass proxies for the clusters (Tx, ng) we find that BCG mass is independent of cluster mass with Mdyn = (2.9 +/- 1.8)x1012 solar masses. / Graduate / 0606 / 0605 / bildfell@uvic.ca

This dissertation presents new Herschel observations at 70 micron, 160 micron, 250 micron, 350 micron, and 500 micron of the Perseus molecular cloud from the Herschel Gould Belt Survey. The Perseus molecular cloud is a nearby star-forming region consisting of seven main star-forming clumps. The Herschel observations are used to characterize and contrast the properties of these clumps, and to study their embedded core populations. First, we probed the exceptionally young clump, B1-E. Using complementary molecular line data, we demonstrate that B1-E is likely fragmenting into a first generation of dense cores in relative isolation. Such a core formation region has never been observed before. Second, we use complementary long wavelength observations at 850 micron to study the dust properties in the larger, more active B1 clump. We find that Herschel data alone cannot constrain well the dust properties of cold dust emission and that long wavelength observations are needed. Additionally, we find evidence of dust grain growth towards the dense cores in B1, where the dust emissivity index, beta, varies from the often assumed value of beta = 2. In the absence of long wavelength observations, however, assuming beta = 2 is preferable over measuring beta with the Herschel-only bands. Finally, we use the source extraction code, getsources, to identify the core populations within each clump from the Herschel data. In addition, we use complementary archival infrared observations to study their populations of young stellar objects (YSOs). We find that the more massive clumps have an excess of older stage YSOs, suggesting that these regions contracted first. Starless cores are typically associated with peaks in the column density, where those found towards regions of higher column density also have higher average densities and colder temperatures. Starless cores associated with a strong, local interstellar radiation field, however, have higher temperatures. We find that the clumps with the most prominent high column density tails also had the highest fractions of early-stage YSOs. This relation suggests that the quantity of high column density material corresponds to recent star formation activity. / Graduate / 0606

Massive young star clusters and OB associations (M > 10 000 Msun) dominate the energetic feedback from stars into the interstellar medium. They contain the most massive and luminous stars in the Galaxy, which shape their environments through winds, ionizing flux, radiation pressure, and eventually supernovae, destroying their natal molecular clouds and inflating superbubbles. Few such clusters have been identified in our Galaxy. We systematically investigate the most luminous H II regions, which we identify using the WMAP foreground maps. We find that the 13 most luminous sources produce one-third of the Galaxy’s total ionizing luminosity, all with expected powering populations of M > 40 000 Msun. These populations are grouped in small numbers of clusters or associations for each WMAP source. The emission from these regions is dominated by the diffuse component at large radii (∼10-70 pc) indicating a high leaking fraction of ionizing photons. Using 8 μm maps from Spitzer GLIMPSE and published radio recombination line observations, we resolve the large (> 1◦) WMAP sources into 40 star forming complexes (SFCs) exhibiting shell morphology with evidence of expansion due to a central powering source. We develop a method, based on differential extinction of the galactic disk, to identify the SFC’s powering cluster candidates with 2MASS. We identify 22 cluster candidates within the 40 SFCs having extinctions consistent with their distances. With near-infrared spectroscopy from the New Technology Telescope, we have confirmed the existence of the most massive of these associations, the Dragonfish Association, with M = 100 000 Msun. Of the 50 sampled stars, we identify 2 Luminous Blue Variable candidates, a Wolf-Rayet, and 15 O-type stars, consistent with the yield expected from the candidate contamination rate, verifying the candidate cluster identification method. This investigation doubles the number of massive young star clusters and OB associations known and produces the most complete picture of the upper end of the Galaxy’s cluster mass function to date.

While the single core accretion model for low mass star formation is well developed, it cannot simply be extended into the high mass star formation regime where clustered star formation dominates. The study of intermediate-mass star formation should provide us with insights into how the process of star formation changes for high mass stars. In this thesis observations of H2O line emission from two intermediate-mass candidate Young Stellar Objects (YSOs) made using the HIFI instrument aboard the Herschel Space Observatory are presented. Modelling of molecular line emission using the radiative transfer code RATRAN is used to put constraints on kinematics and the abundance of water throughout the region by modelling the observed water lines after decomposing them into separate Gaussian components. The medium component of the 752 GHz line from Vela IRS 17 was modelled by using a turbulent velocity of 1.7 km s^-1 and an outer abundance of 6x10^-8. The narrow component of the 752 GHz line from Vela IRS 19 could be modelled using a turbulent velocity of 0.6 km s^-1 and an outer abundance of 6x 10^-8, while the medium component required an outer abundance of 4 x 10^-7 with a turbulent velocity of 2.5 km s^-1. The constraints on water abundance in these star-forming regions are to be used along with studies of water in low and high mass star-forming regions in the effort to improve our understanding of star formation across the entire stellar mass spectrum.

The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) is a 1.8 meter Cassegrain telescope that operates in three bands (250, 350, and 500 μm), each with 30% bandwidth. The detection system is comprised of 280 silicon-nitride micromesh bolometers distributed on three focal plane arrays with 30”, 42”, and 60” FWHM (full width at half max) beam sizes, respectively. BLAST's goal is to study the evolutionary history and processes associated with star formation. Earth's atmosphere is opaque to submillimeter radiation and astronomical observations in this wavelength are best conducted at high altitudes. BLAST is designed to be flown above 99.5% of the atmosphere on a stratospheric balloon. BLAST has made three scientific flights and this thesis covers the last two. The second flight was made in 2006 from McMurdo, Antarctica and studied the evolutionary history and processes associated with star formation. For the third flight, BLAST was reconfigured as a polarimeter (BLAST-Pol) and was also launched from McMurdo in December 2010. BLAST-Pol's objective is to determine what role, if any, magnetic fields play in star formation. This thesis will describe the BLAST-Pol instrument and provide a summery of key observations made by the 2006 flight.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第23704号 / 理博第4794号 / 新制||理||1686(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 嶺重 慎, 教授 長田 哲也, 准教授 細川 隆史 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

Le but de la présente thèse est l'étude de la compléxité moléculaire dans les régions de formation stellaires. Cette thèse s'axe sur deux classes de molécule aux caractéristiques prébiotiques : les molécules organiques complexes et les cyanopolyynes.Dans ce contexte, j'ai analysé des données d'un seul échantillon de relevés spec- traux en exploitant des codes de transfert radiatif à l'équilibre thermodynamique local (LTE) et/ou non-LTE pour deux sources : une proto-étoile de type solaire dans un environnement calme (IRAS 16293-2422) et un proto-ama constitué de proto-étoile de type solaire (OMC2-FIR4).L'objectif est de trouver des similar- ités et des différences entre ces deux cas.J'ai utilisé des données issu de deux relevés spectraux : TIMASSS (The IRAS16293-2422 Millimeter And Submilimeter Spectral Survey) réalisés en 2011 (Caux et al. 2011), et ASAI(Astrochemical Surveys At IRAM) réalisés pen- dant la période 2013-2015 (eg Lopez-Sepulcre et al.2015). J'ai extrais les lignes (identification et intensité intégrée) en utilisant le paquet disponible publique- ment : CASSIS (Centre d'Analyse Scientifique de Spectres Infrarouges et Sub- millimetrique). Pour finir, j'ai utilisé le paquet GRAPES (GRenoble Analysis of Protostellar Envelope Spectral) afin de modéliser la distribution spectrale énergétique de ligne (SLED) des molécules détectées, mais aussi afin d'estimer leurs abondances à travers l'envelope de IRAS16293 et du coeur chaud OMC2- FIR4.Les principaux résultats de la thèse sont :1. Le premier recensement complet des molecules organiques complexes (COMs) dans IRAS162932. La première détéction de COMs dans l'enveloppe froide d'une proto-étoile de type solaire (IRAS16293-2422) supportant l'idée qu'un méchanisme de formation, relativement efficace pour les COMs détectées, doit exister en phase gazeuse froide.3. La découverte d'une fine corrélation entre le diméthyle-éther (DME) et le méthyle-formate (MF) suggère une relation mère fille entre ces deux espèces.4. La detection de formamide, espèce avec un très fort potentiel prébiotique, dans plusieurs protoétoiles incluant IRAS16293-2422 et OMC2-FIR4.5. Le recensement complet des cyanopolyynes dans IRAS16293 et OMC2- FIR4 avec la détection de HC3N, HC5N, DC3N et pour OMC2-FIR4: le C13 isotopologue du HC3N cyanopolyynes.Ces résultats sont le sujet principal de deux publications (Jaber et al.2014, ApJ; Lopez-Sepulcre, Jaber et al.2015,MNRAS), un article accepté (Jaber et al., A & A) et un article à soumettre (Jaber et al. A & A). / The present PhD thesis goal is the study of the molecular complexity in solar type star forming regions. It specifically focuses on two classes of molecules with a pre-biotic value, the complex organic molecules and the cyanopolyynes.At this scope, I analyzed data from single-dish spectral surveys by means of non-LTE or/and non-LTE radiative transfer codes in two sources, a solar type protostar in an isolated and quiet environment (IRAS16293-2422) and a proto-cluster of solar type protostars (OMC2-FIR4). The goal is to find similarities and differences between these two cases.I used data from two spectra surveys: TIMASSS (The IRAS16293-2422 Millimeter And Submillimeter Spectral Survey), which has been carried out in 2011 (Caux et al. 2011), and ASAI (Astrochemical Surveys At IRAM), which has been carried out in 2013-2015 (e.g. Lopez-Sepulcre et al. 2015).I extracted the lines (identification and integrated intensity) by means of the publicly available package CASSIS (Centre dAnalyse Scientifique de Spectres Infrarouges et Submillimtriques).Finally, I used the package GRAPES (GRenoble Analysis of Protostellar Envelope Spectra) to model the Spectral Line Energy Distribution (SLED) of the detected molecules, and to estimate their abundance across the envelope and hot corino of IRAS16293-2422 and OMC2-FIR4, respectively.The major results of the thesis are:1) The first full census of complex organic molecules (COMs) in IRAS16293-2422;2) The first detection of COMs in the cold envelope of a solar type protostar (IRAS16293-2422), supporting the idea that a relatively efficient formation mechanism for the detected COMs must exist in the cold gas phase;3) The discovery of a tight correlation between the dimethyl ether (DME) and methyl format (MF), suggesting a mother-daughter relationship;4) The detection of formamide, a species with a very high pre-biotic value, in several protostars, included IRAS16293-2422 and OMC2-FIR4;5) The full census of the cyanopolyynes in IRAS16293-2422 and OMC2-FIR4, with the detection of HC3N and HC5N, DC3N and, for OMC2-FIR4, the 13C isotopologue of HC3N cyanopolyynes.These results are the focus of two published articles (Jaber et al. 2014, ApJ; Lopez-Sepulcre, Jaber et al. 2015, MNRAS), one accepted article (Jaber et al., A&A) and a final article to be submitted (Jaber et al., A&A).

Remarkable progress has been made over the last few decades in furthering our understanding of the growth of cosmic structure. Nonetheless, there remains a great deal of uncertainty regarding the precise details of the complex baryonic physics that regulate galaxy formation. Any theory of star formation in galaxies must encompass the radiative cooling of gas into dark matter haloes, the formation of a turbulent, multiphase interstellar medium (ISM), the efficiency with which molecular gas is able to collapse into cores and ultimately stars, and the subsequent interaction of those stars with the gas through ionizing radiation, winds and supernova (SN) explosions. Given the highly non-linear nature of the problem, numerical simulations provide an invaluable tool with which to study galaxy formation. Yet, even with contemporary computational resources, the inherently large dynamical range of spatial scales that must be tackled makes the development of such models extremely challenging, inevitably leading to the adoption of `subgrid' approximations at some scale. In this thesis, I explore new methods of incorporating the physics of star formation and stellar feedback into high resolution hydrodynamic simulations of galaxies. I first describe a new implementation of star formation and SN feedback that I have developed for the state-of-the-art moving mesh code Arepo. I carry out a detailed study into various classes of subgrid SN feedback schemes commonly adopted in the literature, including injections of thermal and/or kinetic energy, two parametrizations of delayed cooling feedback and a 'mechanical' feedback scheme that injects the appropriate amount of momentum depending on the relevant scale of the SN remnant (SNR) resolved. All schemes make use of individually time-resolved SN events. Adopting isolated disk galaxy setups at different resolutions, with the highest resolution runs reasonably resolving the Sedov-Taylor phase of the SNR, I demonstrate that the mechanical scheme is the only physically well-posed method of those examined, is efficient at suppressing star formation, agrees well with the Kennicutt-Schmidt relation and leads to converged star formation rates and galaxy morphologies with increasing resolution without fine tuning any parameters. However, I find that it is difficult to produce outflows with high enough mass loading factors at all but the highest resolution. I discuss the various possible solutions to this effect, including improved modelling of star formation. Moving on to a more self-consistent setup, I carry out a suite of cosmological zoom-in simulations of low mass haloes at very high resolution, performed to z = 4, to investigate the ability of SN feedback models to produce realistic galaxies. The haloes are selected in a variety of environments, ranging from voids to crowded locations. In the majority of cases, SN feedback alone has little impact at early times even in low mass haloes ($\sim10^{10}\,\mathrm{M_\odot}$ at z = 0). This appears to be due largely to the build up of very dense gas prior to SN events, suggesting that other mechanisms (such as other stellar feedback processes) are required to regulate ISM properties before SNe occur. The effectiveness of the feedback also appears to be strongly dependent on the merger history of the halo. Finally, I describe a new scheme to drive turbulence in isolated galaxy setups. The turbulent structure of the ISM very likely regulates star formation efficiencies on small scales, as well as affecting the clustering of SNe. The large range of potential drivers of ISM turbulence are not fully understood and are, in any case, unlikely to arise ab initio in a whole galaxy simulation. I therefore neglect these details and adopt a highly idealised approach, artificially driving turbulence to produce an ISM structure of my choice. This enables me to study the effects of a given level of ISM turbulence on global galaxy properties, such as the fragmentation scale of the disk and the impact on SN feedback efficiencies. I demonstrate this technique in the context of simulations of isolated dwarfs, finding that moderate levels of turbulent driving in combination with SN feedback can produce a steady-state of star formation rates and global galaxy properties, rather than the extremely violent SN feedback that is produced by a rapidly fragmenting disk.

abstract: Green pea galaxies are a class of rare, compact starburst galaxies that have powerful optical emission line [OIII]$\lambda$5007. They are the best low-redshift analogs of high-redshift (z$>$2) Lyman-alpha emitting galaxies (LAEs). They provide unique opportunities to study physical conditions in high-redshift LAEs in great detail. In this dissertation, a few physical properties of green peas are investigated. The first study in the dissertation presents star formation rate (SFR) surface density, thermal pressure in HII regions, and a correlation between them for 17 green peas and 19 Lyman break analogs, which are nearby analogs of high-redshift Lyman break galaxies. This correlation is consistent with that found from the star-forming galaxies at z $\sim$ 2.5. In the second study, a new large sample of 835 green peas in the redshift range z = 0.011 -- 0.411 are assembled from Data Release 13 of the Sloan Digital Sky Survey (SDSS) with the equivalent width of the line [OIII]$\lambda$5007 $>$ 300\AA\ or the equivalent width of the line H$\beta$ $>$ 100\AA. The size of this new sample is ten times that of the original 80 star-forming green pea sample. With reliable T$_e$-based gas-phase metallicity measurements for the 835 green peas, a new empirical calibration of R23 (defined as ([OIII]$\lambda$$\lambda$4959,5007 + [OII]$\lambda$$\lambda$3726,3729)/H$\beta$) for strong line emitters is then derived. The double-value degeneracy of the metallicity is broken for galaxies with large ionization parameter (which manifests as log([OIII]$\lambda$$\lambda$4959,5007/[OII]$\lambda$$\lambda$3726,3729) $\geq$ 0.6). This calibration offers a good way to estimate metallicities for extreme emission-line galaxies and high-redshift LAEs. The third study presents stellar mass measurements and the stellar mass-metallicity relation of 828 green peas from the second study. The stellar mass covers 6 orders of magnitude in the range 10$^{5}$ -- 10$^{11}$ M$_{\odot}$, with a median value of 10$^{8.8}$ M$_{\odot}$. The stellar mass-metallicity relation of green peas is flatter and displays about 0.2 - 0.5 dex offset to lower metallicities in the range of stellar mass higher than 10$^{8}$ M$_{\odot}$ compared to the local SDSS star-forming galaxies. A significant dependence of the stellar mass-metallicity relation on star formation rate is not found in this work. / Dissertation/Thesis / Doctoral Dissertation Astrophysics 2018