ZTF Faces

This section features PhD students, postdocs and young faculty who are part of the global ZTF collaboration.

Mathew Smith

Senior Postdoc at IN2P3, France

Tell us briefly about your background and current position

My route to Lyon has been a fairly circuitous one. I’ve studied mathematics in London, radio astronomy in South Africa and cosmic explosions in the UK. Over the past 5 years, based in Southampton in the UK, I was one of the core members of the Dark Energy Survey: the largest search for transients in the distant universe. This survey searched for supernovae at much larger distances than ZTF, billions of years in the past, and used them to measure the contents and eventual fate of the universe.

Having discovered, classified and analysed thousands of faint specks in the sky, now comes the fun challenge: applying my expertise to the tens of thousands of bright specks in the sky discovered by ZTF! Over the next 3 years or so, I’m working with the team in Lyon and across the globe to discover more of these objects than ever before, measure each one more accurately, and combine the two to see if we can produce the most robust measurements of what the Universe is like today. Overall, I hope we’ll make the ZTF dataset the sample that all others look to in the future.

How does ZTF enable your research goals?

Put simply, ZTF is the largest search for transients there is; everything else is dwarfed by comparison. Personally, I’m interested in a unique class of events, type Ia supernovae, that seem standardisable, and thus used to measure the expansion history of the Universe, but we have little idea why they all look the same. With existing datasets of a few hundred events, it’s always been difficult to distinguish between models, and discover why, or why not, these objects are all the same.

ZTF has already discovered over 3000 type Ia supernovae, so it’s an amazing dataset, with loads of opportunity to understand what causes subtle changes in the brightness of an individual event, and how best to turn our measurements into accurate distances. Beyond that, working in the Dark Energy Survey has given me a passion for all things weird: the more you look, the more oddities you find. ZTF is full of cosmic explosions with no obvious origin: I love it.

What’s your most scientifically exciting work?

So, whilst working in the Dark Energy Survey, I found the most distant supernova ever seen; that was pretty cool! In terms of cosmology, I’ve worked a lot recently on the link between SN and the environment in which they explode. This, until very recently, has never really been considered when measuring the expansion rate of the universe. Last year, I discovered that unless you model this relationship correctly all of the inferred distances in your dataset will be wrong, and hence your understanding of the cosmological parameters, or expansion rate of the Universe will be biased. The plan is to determine the true link between a supernova and it’s host galaxy using the ZTF dataset, and thus make sure that when experiments like LSST come along, our estimates of the cosmological parameters are unbiased.

What are your future scientific aspirations?

So the overall aim of my research is to measure ‘what the Universe is made of’; not exactly a small task!
Overall, I love working with a dedicated, passionate team of people on a common goal to explore an interesting dataset or new approach to a common problem, so I hope that in the future I’ll be doing that. Overall, there are so many interesting questions to be addressed, both in astrophysics and beyond, and the world is full of people that I love spending time with, so here’s hoping that over the next few years, I can form new collaborations and answer an interesting question or two.

If you were not an astronomer, what would you be?

So the honest answer to this is “I don’t know”. While I’ve always been inspired by the large concepts explored by astronomy, at the core of it is a love of problem solving. Being able to see ‘the other side’ of a problem, especially an abstract one, is a real thrill, so if I wasn’t doing this, then I’d probably be twisting around another large dataset in search of a hidden correlation or two. The more time I spend doing this job, the more I realise that the skills and problems are entirely transferable to other disciplines: it’s mostly a case of trying to communicate across the divide that is jargon and acronyms. Once you get past those, we’re all working on similar problems, so I like to think that I could be helpful elsewhere. Over the past two years, I’ve worked a lot with front-line doctors on how techniques, developed in astrophysics, can be used to address problems faced in medicine, and amazingly they can! So, while I dream of a career in astrophysics, it’s comforting to know that my skills could be useful elsewhere.

A book that shook your worldview?

So the classic answer here is Douglas Adams’ “The Hitchiker’s Guide to the Galaxy”: I read this relentlessly as a child and it’s probably the reason I’m sitting here today.

The real answer though is Rohinton Mistry’s “A Fine Balance”. I read this in my first year at university with a friend who is now a professional writer. While the story remains one of the most engaging and heart-breaking stories I’ve ever read, it also changed my perspective on the world: I could read things that I liked. Before that, I’d always followed others and tried to echo their opinions as to not stand out. With this book, I chose it, and I loved it. It’s still a work in progress, but it put me on the road of making my own choices in life.

If you’ve had a bad day at work, you will….

To be truthful, on a really bad day at work, I go home late, scream at the wall, eat chocolate and then curl up and hide from the world. On a bad day though, the company of friends and family changes everything. Hearing about and connecting to other people’s lives, and just spending time talking and listening to others, gives me a real sense of balance. It helps me find the perspective and grounding to see how fortunate I am to be able to pursue a subject I love, in a wonderful place surrounded by kind people. As a result, it’s easy to get up the next day with a renewed sense of purpose and direction.