About Me
See my CV here.
I am a fourth year PhD candidate going into my final year working with Prof. Renée Hložek at the University of Toronto and Dunlap Institute for Astronomy & Astrophysics. Prior to this, I completed my Master of Science in Astroparticle Physics and Cosmology from Queen's University and Honours Bachelor of Science in Physics and Astronomy from the University of Toronto. I use a combination of theory, simulations, pipeline development, and data analysis to determine constraints on the early universe and machine learning enabled millimeter transient detection. Alongside my research, I work on various outreach and EDI initiatives including coding and astronomy camps for high school students with Coding the Cosmos in order to promote enthusiasm for science in youth and advocate for diversity. See below for more information about me and my work!
Research
I have broad research interests ranging from constraining the early universe with both the cosmic microwave background (CMB) and stochastic gravitational wave backgrounds (SGWB) to machine learning enabled millimeter transient detection. I am a part of LiteBIRD, Atacama Cosmology Telescope (ACT), and Simons Observatory (SO) collaborations. See below for my publication list and summaries of some of my past work.
Publication ListMachine learning enabled glitch classification
Advances in detector development and read-out technology, coupled with improved angular resolution, has dramatically increased the potential for discovering astrophysical transients with Cosmic Microwave Background (CMB) telescopes. We developed a new algorithm utilizing machine learning for classifying short-duration features in raw time-ordered data (TODs) of CMB observations. Previous techniques that employ statistical thresholding to indiscriminately remove all large spikes in the data (called “data cuts”) end up excising real astrophysical sources, including transients, from the data. The pipeline uses the output from these data cuts but can differentiate between electronic noise, cosmic rays, and point sources, enabling the removal of undesired signals while retaining true astrophysical signals during TOD pre-processing. Our algorithm also produces a sub-minute to minute light curve, which will be particularly useful for upcoming surveys with large data volumes, such as SO. We are currently implementing this method in the SO pre-processing pipeline and TOD based transient alert system. Our proof of concept paper using ACT data can be seen here.
Constraining the primordial and matter power spectrum
Measurements of the microwave sky provide a window into the earliest moments of the cosmos. We used data from ACT which operated from 2007 to 2022 and offers the tightest constraints on the cosmic microwave background (CMB) to date. I determined constraints on the primordial power spectrum using new data from the ACT Data Release 6 (DR6) as well as Planck legacy data, baryon acoustic oscillation data from DESI Year-1, and CMB lensing data from both ACT and Planck. While the concordance cosmology Lambda Cold Dark Matter (LCDM) model is a good fit to our data, the ACT data allow us to study models beyond this standard picture. In order to explore a broader range of deviations from the simple power-law primordial adiabatic power spectrum than those captured solely by the running of the scalar spectral index, we consider a more model-independent approach. We reconstruct the primordial power spectrum of curvature scalar perturbations for 30 \(k\) bins from \(k = 10^{-4} - 0.43 ~\mathrm{Mpc^{-1}}\), and constrain the amplitude per bin. Given the degeneracy between the primordial power and the optical depth (often described in terms of the \({A_s-\tau}\) degeneracy), we sample the value of \(e^{-2\tau}P_{\mathcal{R}}(k_{i})\) for each \(i^{\rm th}\) bin. We find that the constraints from our combined analysis with all listed data sets are improved over the Planck-alone measurements wherever ACT data are included (for \(\ell \gtrsim 850\)). I map this measurement onto the linear matter power spectrum and compare with other measurements from the Dark Energy Survey (DES), the Sloan Digital Sky Survey (SDSS), the extended Baryon Oscillation Spectroscopic Survey (eBOSS), and the Hubble Space Telescope (HST) measurements of the UV galaxy luminosity function (UV LF). These results can be seen in the ACT DR6 extended models paper here.
SGWB from low-scale inflation
My MSc research focused on determining the SGWBs from both inhomogeneities in the inflaton field which drove inflation and from self interaction of the inflaton after inflation. I focused on E- and T-model inflation because they are used as generic inflation models. For different parameter values, E- and T-model inflation are identical to a range of inflationary models which match present CMB observations, including Starobinsky and Higgs inflation. The dynamics of these low scale inflaton fluctuations are complicated, and need to be studied computationally. I used the lattice simulation code HLattice to determine the SGWBs from these T- and E-models. Notably all these SGWB spectra peak in the MHz - GHz range. Current and upcoming experiments such as the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Laser Interferometer Space Antenna (LISA) will not be sensitive here, motivating the development of sensitivity in this regime. Two examples of prospective gravitational wave probes in this regime include, laboratory gravitational wave detectors at GHz frequencies or using the cosmological impact of MHz-GHz gravitational waves, which can contribute to the number of relativistic degrees of freedom in the early universe. This work can be seen both in this paper and my MSc thesis.
Analysis of LiteBIRD Systematics and their Impact on Cosmology
For my undergraduate thesis I was a part of the science maturation study on the proposed Japanese CMB satellite, LiteBIRD, for the Canada Space Agency. I ran simulations using Time Ordered Astrophysics Scalable Tools (TOAST) in order to determine what the noise spectra for LiteBIRD would look like over the course of its lifetime. Using these noise curves, I did Fisher Forecasts in order to determine LiteBIRD's sensitivity to inflationary models. See the poster above for a summary of this work.
Outreach and EDI
Outreach and equity work is is one of my core passions in order to challenge stereotypes of who can be a scientist, increase science literacy, and provide educational experiences to minoritized and low socio-economic students who would not otherwise have such opportunities. I'm committed to building a more inclusive research community and aim to actively shape the culture of our community and help open doors for people who have too often been excluded. Below, I've summarized a few projects I’ve led or contributed to, focused on expanding access, mentorship, and advocacy in astronomy.
Coding the Cosmos
I founded and served as PI for Coding the Cosmos, receiving $36,000 from the Dunlap Institute to run coding and astronomy camps for marginalized high school students. and low socio-economic high school students. I was the PI for our seed funding grants, wrote curriculum, developed materials, recruited volunteers and executives, ran trainings for volunteers, oversaw and managed all working groups totalling over 35 volunteers, and led organization logistics. We ran training sessions for our volunteers, which consisted of both undergraduate and graduate students from both the University of Toronto and McMaster University, in order to teach them science communication skills and best practices. We also had a team of volunteers aid in material and curriculum development. This allowed them to significantly expand their science communication skills. You can access the materials from our 2023 camp here and 2024 camps here.
AstroTours
I was the co-director for AstroTours from 2021 to 2023 which is a monthly outreach event run by the graduate students in the Astronomy & Astrophysics department at the University of Toronto. Our events are free and open to the public which cultivates a consistent (typically 100+ attendees per talk) but varied audience of students, professionals, enthusiasts, families, and even occasionally school groups. We design for our activities and talks to be appealing and approachable for a variety of demographics. We train the volunteers on how to use the telescopes, how to run the science demos, and have the monthly speaker give a practice talk to get feedback from our executives which improves their science communication. Additionally, during my time as co-director, we introduced lab tours of the different astronomy instrumentation labs. Attendee feedback indicates that they really enjoy having the opportunity to see how research is conducted.
Let's Talk Science
Let's Talk Science is a national Canada wide outreach organization which runs both large events and classroom visits to schools across the country with the goal to improve science literacy and building youth interest in STEM. I was a part of Let's Talk Science from 2019 to 2021 as first a volunteer then coordinator for the Queen's University branch. As a volunteer I ran classroom visits at elementary schools involving leading demonstrations, giving quick lectures on the science behind the activities, and supporting students in conducting their own experiments. As a coordinator I managed volunteers and connected them with outreach opportunities, organized virtual outreach for K-12 classes and developed new kits for topics such as physics, astronomy, and computer science. While coordinator, I also organized a virtual Canada wide national symposium called Let's Talk Astrophysics where we taught high school and CÉGEP students the basics of python using a Jupyter Notebook and go through making a galactic rotation curve. You can access these materials here.
Mentorship
I ran a pilot mentorship program at Queen’s University for upper year undergraduates at Queen's University that matched students and mentors based on their research interests and intersecting identities. I sourced mentors from around the world, in order to have mentors in the specific fields and identities with the mentee pool. I’ve also personally mentored multiple students and co-supervised three undergrad research projects.
National Advocacy
I have served on three committees within the Canadian Astronomical Society (CASCA), contributing to outreach, graduate student support, and equity. I co-designed a national demographics and harassment survey, now ethics-approved, to assess and improve Canadian astronomy culture.
Contact Me
You can contact me at simran.nerval@mail.utoronto.ca.