The synthesis and separation properties of organic cage compounds

Microporous materials play an important role in a variety of industrial and domestic applications. While a diverse range of microporous materials have been identified, this thesis focuses on porous organic cages (POCs) because they have received much attention as synthetically tunable, solution processable, microporous materials. After introducing the latest developments in POC synthesis and the general application of microporous materials as selective sorbents, this thesis presents three developments in organic cage chemistry: a high-throughput workflow for the discovery of POCs, which yielded a novel organic cage compound; the measurement of selective adsorption by POCs, wherein the first instance of chiral selectivity by a POC was recorded; and the first instance of applying POCs as stationary phases for gas chromatography, which produced columns that separate racemic mixtures, alkylaromatic isomers, and alkane isomers. Chapter 2, discovering novel organic cages, presents attempts to use high-throughput and in-silico techniques to accelerate the discovery of novel organic cages. These methods were utilised to isolate a novel organic cage, CCX-S, which is characterised and discussed. Chapter 3, organic cages as selective sorbents, presents the development of approaches for measuring selective adsorption. These methods were used to identify the first reported instance of enantioselective adsorption by an organic cage. Further measurements to explain this separation behavior are also presented. Chapter 4, chromatographic separations with organic cages, presents one method of practically leveraging the presented separation behavior. In Chapter 4, the coating of capillary columns with CC3 is presented. These columns were used to successfully perform gas chromatographic separations, the first recorded instance of using a POC to do so. The columns were further improved by modifying the coating method and using prefabricated CC3 nanoparticles. This modification enabled difficult separations to be performed using the column; for example, the separation of hexane’s five isomers

A physically-based model of the ionizing radiation from active galaxies for photoionization modeling

We present a simplified model of Active Galactic Nucleus (AGN) continuum emission designed for photoionization modeling. The new model {\sc oxaf} reproduces the diversity of spectral shapes that arise in physically-based models. We identify and explain degeneracies in the effects of AGN parameters on model spectral shapes, with a focus on the complete degeneracy between the black hole mass and AGN luminosity. Our re-parametrized model {\sc oxaf} removes these degeneracies and accepts three parameters which directly describe the output spectral shape: the energy of the peak of the accretion disk emission $E_\mathrm{peak}$, the photon power-law index of the non-thermal emission $\Gamma$, and the proportion of the total flux which is emitted in the non-thermal component $p_\mathrm{NT}$. The parameter $E_\mathrm{peak}$ is presented as a function of the black hole mass, AGN luminosity, and `coronal radius' of the {\sc optxagnf} model upon which {\sc oxaf} is based. We show that the soft X-ray excess does not significantly affect photoionization modeling predictions of strong emission lines in Seyfert narrow-line regions. Despite its simplicity, {\sc oxaf} accounts for opacity effects where the accretion disk is ionized because it inherits the `color correction' of {\sc optxagnf}. We use a grid of {\sc mappings} photoionization models with {\sc oxaf} ionizing spectra to demonstrate how predicted emission-line ratios on standard optical diagnostic diagrams are sensitive to each of the three {\sc oxaf} parameters. The {\sc oxaf} code is publicly available in the Astrophysics Source Code Library.Comment: 14 pages, 9 figures, 1 table. Accepted for publication in Ap

The mass-metallicity relation of local active galaxies

We systematically measure the gas-phase metallicities and the mass-metallicity relation of a large sample of local active galaxies for the first time. Observed emission-line fluxes from the Sloan Digital Sky Survey (SDSS) are compared to a four-dimensional grid of photoionization models using the Bayesian parameter estimation code NebulaBayes. For the first time we take into account arbitrary mixing between HII region and narrow-line region (NLR) emission, and the models are also varied with metallicity, ionization parameter in the NLR, and the gas pressure. The active galactic nucleus (AGN) oxygen abundance is found to increase by $\Delta {\rm O/H} \sim 0.1$ dex as a function of host galaxy stellar mass over the range $10.1 < \log M_* / M_\odot < 11.3$. We also measure the metallicity and ionization parameter of 231000 star-forming galaxies for comparison with the sample of 7670 Seyfert 2 galaxies. A systematic offset in oxygen abundance of 0.09 dex is observed between the mass-metallicity relations of the star-forming and active galaxies. We investigate potential causes of the offset, including sample selection and the treatment in the models of diffuse ionized gas, pressure, and ionization parameter. We cannot identify the major cause(s), but suspect contributions due to deficiencies in modeling the ionizing spectra and the treatment of dust physics. Optical diagnostic diagrams are presented with the star-forming and Seyfert data colored by the inferred oxygen abundance, ionization parameter and gas pressure, clearly illustrating the trends in these quantities.Comment: 12 pages, 4 figures and 1 table; accepted for publication in Ap

Interrogating Seyferts with NebulaBayes: Spatially probing the narrow-line region radiation fields and chemical abundances

NebulaBayes is a new Bayesian code that implements a general method of comparing observed emission-line fluxes to photoionization model grids. The code enables us to extract robust, spatially resolved measurements of abundances in the extended narrow line regions (ENLRs) produced by Active Galactic Nuclei (AGN). We observe near-constant ionization parameters but steeply radially-declining pressures, which together imply that radiation pressure regulates the ENLR density structure on large scales. Our sample includes four `pure Seyfert' galaxies from the S7 survey that have extensive ENLRs. NGC2992 shows steep metallicity gradients from the nucleus into the ionization cones. An {\it inverse} metallicity gradient is observed in ESO138-G01, which we attribute to a recent gas inflow or minor merger. A uniformly high metallicity and hard ionizing continuum are inferred across the ENLR of Mrk573. Our analysis of IC5063 is likely affected by contamination from shock excitation, which appears to soften the inferred ionizing spectrum. The peak of the ionizing continuum E_peak is determined by the nuclear spectrum and the absorbing column between the nucleus and the ionized nebula. We cannot separate variation in this intrinsic E_peak from the effects of shock or HII region contamination, but E_peak measurements nevertheless give insights into ENLR excitation. We demonstrate the general applicability of NebulaBayes by analyzing a nuclear spectrum from the non-active galaxy NGC4691 using a HII region grid. The NLR and HII region model grids are provided with NebulaBayes for use by the astronomical community.Comment: Accepted for publication in ApJ; 29 pages with 10 figures and 3 table

VLBI detection of an Infrared-Faint Radio Source

Infrared-Faint Radio Sources represent a new and unexpected class of object which is bright at radio wavelengths but unusually faint at infrared wavelengths. If, like most mJy radio sources, they were either conventional active or star-forming galaxies in the local Universe, we would expect them to be detectable at infrared wavelengths, and so their non-detection by the Spitzer Space Telescope is surprising. Here we report the detection of one of these sources using Very Long Baseline Interferometry, from which we conclude that the sources are driven by Active Galactic Nuclei. We suggest that these sources are either normal radio-loud quasars at high redshift or abnormally obscured radio galaxies.Comment: accepted by MNRA

A new diagnostic to separate line emission from star formation, shocks, and AGNs simultaneously in IFU data

In the optical spectra of galaxies, methods for the separation of line emission arising from star formation and an additional hard component, such as shocks or active galactic nuclei (AGNs), is well-understood and possible with current diagnostics. However, such diagnostics fail when attempting to separate and define line emission which arises from shocked gas, and that arising from AGNs. We present a new three-dimensional diagnostic diagram for integral field unit data which can simultaneously separate the line emission amongst star formation, shocks, and AGNs within a galaxy. We show that regions we define as AGN-dominated correlate well with the hard X-ray distribution in our test case NGC 1068, as well as with known regions of AGN activity in NGC 1068. Similarly, spaxels defined as shock-dominated correlate strongly with regions of high-velocity dispersion within the galaxy.Parts of this research were conducted by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3Dimensions (ASTRO 3D), through project number CE170100013

Z-FIRE: ISM properties of the z = 2.095 COSMOS Cluster

We investigate the ISM properties of 13 star-forming galaxies within the z~2 COSMOS cluster. We show that the cluster members have [NII]/Ha and [OIII]/Hb emission-line ratios similar to z~2 field galaxies, yet systematically different emission-line ratios (by ~0.17 dex) from the majority of local star-forming galaxies. We find no statistically significant difference in the [NII]/Ha and [OIII]/Hb line ratios or ISM pressures among the z~2 cluster galaxies and field galaxies at the same redshift. We show that our cluster galaxies have significantly larger ionization parameters (by up to an order of magnitude) than local star-forming galaxies. We hypothesize that these high ionization parameters may be associated with large specific star formation rates (i.e. a large star formation rate per unit stellar mass). If this hypothesis is correct, then this relationship would have important implications for the geometry and/or the mass of stars contained within individual star clusters as a function of redshift.Comment: 11 pages, 5 figures, accepted for publication in Ap

ZFIRE: Using Hα\alpha equivalent widths to investigate the in situ initial mass function at z~2

We use the ZFIRE survey (http://zfire.swinburne.edu.au) to investigate the high mass slope of the initial mass function (IMF) for a mass-complete (log10(M$_*$/M$_\odot$)~9.3) sample of 102 star-forming galaxies at z~2 using their H$\alpha$ equivalent widths (H$\alpha$-EW) and rest-frame optical colours. We compare dust-corrected H$\alpha$-EW distributions with predictions of star-formation histories (SFH) from PEGASE.2 and Starburst99 synthetic stellar population models. We find an excess of high H$\alpha$-EW galaxies that are up to 0.3--0.5 dex above the model-predicted Salpeter IMF locus and the H$\alpha$-EW distribution is much broader (10--500 \AA) than can easily be explained by a simple monotonic SFH with a standard Salpeter-slope IMF. Though this discrepancy is somewhat alleviated when it is assumed that there is no relative attenuation difference between stars and nebular lines, the result is robust against observational biases, and no single IMF (i.e. non-Salpeter slope) can reproduce the data. We show using both spectral stacking and Monte Carlo simulations that starbursts cannot explain the EW distribution. We investigate other physical mechanisms including models with variations in stellar rotation, binary star evolution, metallicity, and the IMF upper-mass cutoff. IMF variations and/or highly rotating extreme metal poor stars (Z~0.1Z$_\odot$) with binary interactions are the most plausible explanations for our data. If the IMF varies, then the highest H$\alpha$-EWs would require very shallow slopes ($\Gamma$>-1.0) with no one slope able to reproduce the data. Thus, the IMF would have to vary stochastically. We conclude that the stellar populations at z~2 show distinct differences from local populations and there is no simple physical model to explain the large variation in H$\alpha$-EWs at z~2.Comment: Accepted to MNRAS. 43 pages, 27 Figures. Survey website: http://zfire.swinburne.edu.au

ZFIRE: A KECK/MOSFIRE Spectroscopic Survey of Galaxies in Rich Environments at z~2

We present an overview and the first data release of ZFIRE, a spectroscopic redshift survey of star-forming galaxies that utilizes the MOSFIRE instrument on Keck-I to study galaxy properties in rich environments at $1.5<z<2.5$. ZFIRE measures accurate spectroscopic redshifts and basic galaxy properties derived from multiple emission lines. The galaxies are selected from a stellar mass limited sample based on deep near infra-red imaging ($\mathrm{K_{AB}<25}$) and precise photometric redshifts from the ZFOURGE and UKIDSS surveys as well as grism redshifts from 3DHST. Between 2013--2015 ZFIRE has observed the COSMOS and UDS legacy fields over 13 nights and has obtained 211 galaxy redshifts over $1.57<z<2.66$ from a combination of nebular emission lines (such as \Halpha, \NII, \Hbeta, \OII, \OIII, \SII) observed at 1--2\micron. Based on our medium-band NIR photometry, we are able to spectrophotometrically flux calibrate our spectra to \around10\% accuracy. ZFIRE reaches $5\sigma$ emission line flux limits of \around$\mathrm{3\times10^{-18}~erg/s/cm^2}$ with a resolving power of $R=3500$ and reaches masses down to \around10$^{9}$\msol. We confirm that the primary input survey, ZFOURGE, has produced photometric redshifts for star-forming galaxies (including highly attenuated ones) accurate to $\Delta z/(1+z\mathrm{_{spec})}=0.015$ with $0.7\%$ outliers. We measure a slight redshift bias of $<0.001$, and we note that the redshift bias tends to be larger at higher masses. We also examine the role of redshift on the derivation of rest-frame colours and stellar population parameters from SED fitting techniques. The ZFIRE survey extends spectroscopically-confirmed $z\sim 2$ samples across a richer range of environments, here we make available the first public release of the data for use by the community.\footnote{\url{http://zfire.swinburne.edu.au}}Comment: Published in ApJ. Data available at http://zfire.swinburne.edu.au, Code for figures at https://github.com/themiyan/zfire_survey, 31 pages, 24 figure