Research

I have a BSc in chemistry, MSc in astronomy and PhD in astrophysics. I am dedicated to contributing to space science via my interdisciplinary skills in the field of astrochemistry. I am highly motivated to work on some of the open questions crucial to our understanding of the universe, especially those involving the physics and chemistry of the interstellar medium.

My Research Interest

Interstellar medium, interstellar dust, interstellar ice, interstellar extinction, interstellar chemical abundances, interstellar carbon, carbon chemistry in interstellar and circumstellar environments, carbonaceous material in interstellar / interplanetary dust, ice and planetesimals.

Observational Astronomy: spectrophotometric observations of interstellar dust.

Laboratory Astrophysics: production and spectral analysis of interstellar dust analogues.

Computational Chemistry: computational spectra of interstellar molecules.

Current Research

In the ISM, dust and ice particles are solid components of the interstellar matter. C, Si and O are the major ice and dust forming elements. The elemental abundances proposed in the ISD and ices should be in accordance with the cosmic abundances. However, carbon depletion from the gas phase is not sufficient to account for the proposed abundance in carbonaceous solids and the oxygen abundance proposed to be in siliceous material cannot be accounted for by the depleted oxygen from the gas phase. These have been referred to as the carbon crisis and the missing oxygen problem. The presence of interstellar ice within the ISD in the cold regions of the ISM add more complications to abundance studies. There are some spectral features in the IR region that can be used to trace elements incorporated in solid phase ISM. The water ice O-H feature at 3.0-µm, the aliphatic hydrocarbon C-H feature at 3.4-µm and the silicate feature Si-O at 9.8-µm have particular importance as they are suitable for quantitative observational studies. It is possible to estimate the abundance of C-H, O-H and Si-O groups from optical depth measurements in MIR – NIR region by combination with laboratory work (i.e. [G18]). The investigation of solid phase elemental abundances in large scales in ISM along with the photometric measurements of the 3.4-µm aliphatic hydrocarbon C-H feature and the 9.8-µm Si-O feature has the potential to help map the carbonaceous dust and siliceous dust distribution separately. Additionally, application of the photometric method to the 3.0-µm water ice O-H feature can be used to probe ices in large scales.

We are working on a code to obtain optical depth of the 3.0-µm water ice O-H feature, the 3.4-µm aliphatic hydrocarbon C-H feature and the 9.8-µm silicate Si-O feature, using the combination of NIRCam and MIRI imaging filters. This code will model photometric observations and link them to the corresponding spectroscopic optical depths. We are simulating spectra and obtaining simulated fluxes by using transmission profiles of NIRCam and MIRI imaging filters. We are supporting this model through analysis of laboratory computational spectra and observational spectra from the literature to improve the calibration. Additionally, we are working on code to obtain siliceous and carbonaceous dust and ice maps by analysing photometric fluxes measured by JWST data processing tools. We are aiming to use outcomes of the current work to propose a JWST observation program.

Future Research

We aim to apply the photometric mapping method with JWST to investigate the Galactic plane through the lines of sight of the GC. The central region of our Galaxy contains an exotic collection of objects including a supermassive black hole (Sagittarius A*). However, the GC is obscured by the spiral arms of the Galaxy, which are containing vast amounts of gas, dust and ices. The position of the Sun in the Galactic disc significantly prevents the study of the GC and spiral arm structure of our Galaxy and its properties. The interstellar matter obscures the low-Galactic-latitude lines of sight towards GC and we do not have much information on the physics and chemistry of this obscuring matter. Therefore, study of the spiral arms of our Galaxy is of fundamental interest because it is essential to the understanding of superimposed GC objects, galactic morphology, dynamics and evolution.

The 3.4-µm aliphatic hydrocarbon, 9.8-µm silicate and 3.0-µm ices absorptions can probe different chemical and physical environments in the ISM. The maps aliphatic hydrocarbons, silicates and ices will reveal the abundances and distributions of the major solid phase elements in the ISM. Such an investigation through the lines of sight of the GC has a potential to reveal different chemical and physical conditions of the ISM and therefore, help to understand the Galactic Centre morphology and chemical evolution of the ISM in our Galaxy.

Previous Research

We implement a new method for measuring the amount and distribution of aliphatic carbon within the interstellar dust (ISD) over wide fields of view of our Galaxy. We used 3.4-μm aliphatic hydrocarbon absorption feature absorption coefficient measured in the laboratory and 3.4-μm aliphatic hydrocarbon optical depth measured by the observational studies to obtain column density of the aliphatic hydrocarbons in the interstellar medium (ISM).

Laboratory Studies: We produced reliable analogues of ISD from gas phase precursor molecules by experimentally mimicking interstellar/circumstellar conditions using a discharge and vacuum chamber in the laboratory. The images of interstellar dust analogues (ISDAs) were analysed by scanning electron microscopy (SEM) to investigate their physical structures (amorphous or graphitic). We analysed their infrared (IR) spectra using high resolution cryogen cooling vacuum Fourier Transform IR (FTIR) Spectroscopy in the laboratory. The spectra of ISDAs were compared with a set of ISM spectra in Near-IR (NIR) and Mid-IR (MIR) from the literature and we found they closely match those from astronomical observations. Additionally, we compared their spectra with a meteoritic (Murchison meteorite) spectrum in NIR and found them to be similar. Then we used ISDAs samples to obtain the 3.4-µm absorption coefficients of aliphatic hydrocarbons incorporated in the ISD. Measurements of the absorption coefficients were carried out by a procedure combining FTIR and 13C NMR (nuclear magnetic resonance) spectroscopy methods. While this procedure has been never applied previously since it requires large amount of ISDAs, it can supply the most accurate measurement of the absorption coefficient than the previous methods in the literature. The results allowed us to direct calibration of the astronomical observations and provided precise estimates of the amount of aliphatic hydrocarbon in the ISD (MNRAS 479, 4336–4344 (2018), hereafter [G18]).

Observational Studies: Measurement of the 3.4-μm optical depth can be done readily for individual sightlines by single point or long-slit spectroscopy but these processes require long observing times. While this method cannot produce as accurate a determination of the spectra, it can supply better source detection and can be applied to all of the sources above a threshold flux in the field of view. We carried out the photometric measurements using narrow band filters in L-band by using the United Kingdom Infrared Telescope (UKIRT) (MNRAS 493, 1109–1119 (2020), hereafter [G20]). We first applied the method through the dusty sightlines of the diffuse interstellar medium towards the centre of the Galaxy (Field A), where the optical depth of the 3.4-µm absorption had been reported for the GC cluster (references in [G20]). We used the reported values in the literature to calibrate the UKIRT narrow band measurements. We combined laboratory ([G18]) and observational studies to obtain a map that shows the distribution of the aliphatic carbon in the interstellar dust along the lines of sight to the Galactic Centre (GC). After obtaining the first map of interstellar aliphatic hydrocarbons in the literature we extended the method to a new field in the GC region (Field B) where the 3.4-µm absorption feature has not been previously measured and a field in the Galactic Plane to sample the diffuse local interstellar medium where the 3.4-µm absorption feature has been previously measured (Field C). We analysed 3.4-µm optical depth and aliphatic hydrocarbon column density maps for these new fields. Thus, we have clarified that the photometric method is applicable to other fields in the Galactic Plane (MNRAS 515, 4201–4216 (2022), hereafter [G22]).  

These studies have brought the largest perspective to date on the amount and distribution of solid phase hydrocarbons in the ISM. For the Galactic centre fields (Field A and Field B), we found that hydrocarbon abundances vary in small scale in by taking values above and below the cosmic abundances. We also found a mild gradient in the optical depth of 3.4-µm toward the Galactic midplane, rising by about a factor of 50 %. We showed that, an important part of cosmic carbon (least 10 – 20 %) is in aliphatic hydrocarbon form in the ISD in the Galactic disk. We compared aliphatic hydrocarbon maps (Field A and Field B) reddening maps. However, we could not find any correlation. This implies that the distribution of the carbonaceous dust is not homogenous in ISM ([G22]).