National Astronomy Meeting Poster Exhibition

Shocks are regularly observed in the lower solar atmosphere, for example, umbral flashes which have average lifetimes of roughly a minute. For ideal magnetohydrodynamic (MHD) theory, slow-mode shocks should become unstable to the corrugation instability, triggered by the inhomogeneities in the solar atmosphere. However, the lower solar atmosphere is partially ionised, and the presence of a neutral species can stabilise the shock front. Here I present numerical results to investigate the stability conditions for a partially-ionised slow-mode shock with regards to the corrugation instability. Our results indicate that a stability range can be determined based on physical parameters of the system, where partially-ionised shocks are stable depending on the perturbation wavelength relative to the finite shock width. We relate these results to umbral flashes by estimating the wavelengths that could result in a stable shock front, and the observational consequences in terms of observing two-fluid effects in the lower solar atmosphere with the latest instruments.

The Kinetic Inductance Detector Spectrometer (KIDSpec) is an upcoming Microwave Kinetic Inductance Detector (MKID) optical to NIR instrument which has the potential to contribute science to a wide variety of fields. One such field is transients. Due to the MKID's native time resolution on the order of μs and lack of read noise and dark current, KIDSpec will be well suited to observations of these objects. Here we briefly outline the KIDSpec concept, the KIDSpec Simulator (KSIM) and show results from simulations of KIDSpec's observations when used to view these objects when completed.

Magnetic helicity is an invariant of the ideal MHD equations and is used as a diagnostic tool in the analysis of magnetic fields in active regions. Here, we explore an associated quantity, the winding number, that measures the degree of knotedness of a magnetic field configuration. The winding has the advantage of not being strongly concentrated in regions of strong magnetic field, and therefore it is more sensitive to changes in the topology of the magnetic field in the whole domain. The winding has been shown to be an efficient tool in MHD simulations of magnetic field emergence, now we present evidence of its efficacy in observations. We present the analysis of a few active regions using the winding and compare it with the analysis of helicity. In summary, we find that the winding is able to detect structural changes in the magnetic field more effectively than the helicity, and suggest that it can be used as an alternative predictive tool for eruptive events in active regions.

The two widely separated epochs of UKIDSS K band photometry yielded a sample of almost 400 highly variable YSO candidates, many located in nearby, well-studied star forming regions. Here I present a follow-up study of a set of 32 of these objects using K band spectroscopy from Subaru/IRCS and Gemini/NIFS, as well as time-series mid-infrared photometry from NEOWISE.

The sample appears to confirm one FUor, with 2 further FUor-like stars, whilst other candidates displayed a mixture of characteristics, including an EXor-like star, and others with heavily veiled spectra. Furthermore, an equally wide range of behaviours can be seen in the light-curves, notably some periodic LCs similar to dusty long-period variable AGB stars, and others possibly undergoing extreme periodic extinction events.

The sample's stars mostly reside in the Cygnus-X star formation region, which allows for comparison to other large scale YSO surveys of the complex, this consequently allows for additional high-amplitude variables to be located, by examining UKIDSS photometry for confirmed YSOs that don't appear in multiple epochs. This yielded 16 new eruptive variable candidates, including several that resemble FUor type events. This survey confirms the diversity of YSOs in the infra-red and highlights how much more we can still learn about the IR variable sky.

In order to better understand star formation in galaxies, it is important to have a firm grasp on the physics of the ISM. In particular, the role of magnetic fields in controlling the large-scale dynamics of the ISM and molecular cloud formation, is still unclear. In 2020, Tress et al presented high-resolution, three-dimensional AREPO simulations inspired by the M51 galaxy, and in this project, we will be running magnetised versions of these hydrodynamic simulations to investigate how this changes the dynamics of the ISM. The initial goals of this work are threefold; firstly to find if magnetic fields significantly change the properties of molecular clouds, secondly to determine if magnetic fields change the star formation history of molecular clouds, and thirdly to discern what observational signatures of magnetic fields on the cloud formation process can be detected.

The last catalog released of HII regions from CALIFA survey comprises the information of 27000 objects. In previous work, we explored the dependence on the distribution of HII regions sample on the BPT diagram with the morphological type and galactocentric distance. We found a relation between the strong emission lines of nebulae and the subjacent stellar populations' properties. In this work, we present the physical properties from HII regions sample: oxygen abundance, ionization parameter, the fraction of young stellar population, nitrogen-oxygen ratio, electronic density, and dust extinction (Av). We analyzed the dependence between the physical properties and the galactocentric distance, the morphological type, and the stellar mass of the respective host galaxies. We found a relation between the oxygen abundance of HII regions and the age and metallicity of underlying stellar populations.

The evolution of the photospheric magnetic field plays a key role in the energy transport into the chromosphere and the corona. In active regions, newly emerging magnetic flux interacts with the preexistent magnetic field, which can lead to reconnection events that convert magnetic energy to thermal energy. We aim to study the heating caused by a strong reconnection event that was triggered by magnetic flux cancellation. We use imaging-spectropolarimetric data in the Fe I 6301A, Fe I 6302A, Ca II 8542A and Ca II K obtained with the CRISP and CHROMIS instruments at the Swedish 1-m Solar Telescope. This data was inverted using multi-atom, multi-line non-LTE inversions using the STiC code. The inversion yielded a three-dimensional model of the reconnection event and surrounding atmosphere, including temperature, velocity, microturbulence, magnetic file configuration, and the radiative loss rate. The model atmosphere shows the emergence of magnetic loops with a size of several arcsecs into a pre-existing predominantly unipolar field. Where the reconnection region is expected to be, we see an increase in the chromospheric temperature of roughly 2000 K as well as bidirectional flows of the order of 10 km/s emanating from the region. We see bright blobs of roughly 0.2 arcsec diameter in the Ca II K moving at a plane-of-the-sky velocity of order 100 km/s and a blueshift of 100 km/s, which we interpret as plasmoids ejected from the same region. This evidence is consistent with theoretical models of reconnection and we thus conclude that reconnection is taking place. The chromospheric radiative losses at the reconnection site in our inferred model are as high as 160 kW/m2, providing a quantitative constraint on theoretical models that aim to simulate reconnection caused by flux emergence in the chromosphere.

About 90% of the stellar build-up in galaxies is thought to occur gradually on the Main Sequence (MS), with the tightness of this relation commonly interpreted as a consequence of the self-regulative nature of galaxies. Importantly, the scatter of the relation (at the level of ~0.2-0.3 dex across observed redshifts) encodes key information about the nature of the driver(s) of star formation. In particular, it is currently still unclear whether there are multiple pathways of stellar mass growth. In other words, does the observed scatter in the MS relation stem from systematic long-term differences in the star formation histories of galaxies residing above/below the Main Sequence today (set by e.g. variations in halo assembly)? Or can the spread simply be attributed to short-term stochastic fluctuations in the growth rates of galaxies (e.g. variations in gas inflow, minor mergers, "breathing" cycles of star-bursting episodes followed by a suppression due to feedback)?
The above questions are also indirectly related to the end of the lifecycle of galaxies. By discriminating between a predominantly smooth or bursty evolution of galaxies, quenching may be interpreted as a natural progression of a continuous decline in star formation (slow quenching) or a disruptive process (fast quenching).
Within this framework, I will present new insights into the the star formation histories of massive star-forming SDSS-IV MaNGA galaxies, as reconstructed via full spectro-photometric fitting with the novel stellar population synthesis code Bagpipes (Carnall et al., 2018).

In July 2007, a regional dust storm on Mars grew and became global, engulfing the entire planet and lasting several months. This storm had a profound impact across Mars, with dust reaching altitudes of 80 km and global temperatures rising by up to 40 K. It is seen from Mars Express (MEx) MARSIS data that ionization created in the lower atmosphere is observed at higher altitudes, with an altitude dependent enhancement in plasma density over crustal magnetic fields (Venkateswara et al., 2019). The Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3) experiment on the MEx spacecraft has operated at Mars since 2004 (continuing to operate today) and has produced a long time-base of plasma measurements from as low as 250 km. ASPERA-3 on MEx will be used to investigate the effects the 2007 global dust storm had on the plasma environment by comparing data before, during, and after the event. Of particular interest are plasma measurements over radial magnetic fields from crustal anomalies, where transport of charged particles is guided out of the atmosphere. The before, during, and after effects will shed light on to the influence dust storms have on the escaping plasma measured by ASPERA-3 and how dust changes the local plasma escape directly from the atmosphere. Our initial study focuses on data from the electron spectrometer (ELS) where we investigate how the energy distribution and peak energy value varies in altitude above the Martian surface.

Upcoming large-area narrow band photometric surveys, such as Javalambre Physics of the Accelerating Universe Astrophysical Survey (J-PAS), will enable us to observe a large number of galaxies simultaneously and efficiently. However, it will be challenging to analyse the spatially resolved stellar populations of galaxies from such big data to investigate galaxy formation and evolutionary history. We have applied a convolutional neural network (CNN) technique, which is known to be computationally inexpensive once it is trained, to retrieve the metallicity and age from J-PAS-like narrow-band images. The CNN was trained using synthetic photometry from the integral field unit spectra of the Calar Alto Legacy Integral Field Area survey and the age and metallicity obtained in a full spectral fitting on the same spectra. We demonstrate that our CNN model can consistently recover age and metallicity from each J-PAS-like spectral energy distribution. The radial gradients of the age and metallicity for galaxies are also recovered accurately, irrespective of their morphology. However, it is demonstrated that the diversity of the data set used to train the neural networks has a dramatic effect on the recovery of galactic stellar population parameters. Hence, future applications of CNNs to constrain stellar populations will rely on the availability of quality spectroscopic data from samples covering a wide range of population parameters.