26 Feb 2016
In my last week as a postdoc in Oxford - my last week as a postdoc anywhere, in fact - I was very happy to have two new first-author papers accepted for publication in the space of 2 working days. They appeared on astro-ph together on Wednesday, here and here.
The first was a round-up of results from the work I've been doing on Milky Way galactic-scale star formation, using the data from the Milky Way Project (MWP) citizen science project. In the MWP, tens of thousands of volunteers helped us find and characterize interstellar medium bubbles in infrared images from the GLIMPSE and MIPSGAL surveys with the Spitzer Space Telescope. These surveys mapped the inner regions of our Galactic Plane with an unprecedented spatial resolution at infrared wavelengths, showing us a (then) unique view on the beauty and complexity (and chemistry!) of the Galaxy's interstellar medium (ISM).
These bubbles, first catalogued by Ed Churchwell and collaborators in 2006-2007, were found to be excellent tracers of where massive stars and clusters have recently formed. So we can use them to study the interaction between these stars and the surrounding cloud material. But while many authors have done this for one or a few bubbles - complementing the Spitzer IR images with CO observations of the molecular cloud, optical spectroscopy of the cluster stars, X-ray data, etc - the MWP catalogue of some 5000 bubbles allows us to study those interactions statistically, on a Galaxy-wide scale.
We first did this by correlating the locations of massive young protostars or young HII regions as detected by the RMS survey with those of the bubbles in our 2012 paper, finding evidence that we're more likely to find newly forming massive protostars in or on the outskirts of bubbles than in regions without bubbles. But there were some limitations to this study, and in the new paper we compare the distribution of cold massive dust clumps in the Galactic Plane to that of the bubbles to overcome some of those.
Our sample of cold dust clumps is taken from the ATLASGAL survey, a major survey led by Frederic Schuller of the Max Planck Institute for Radio Astronomy in Bonn (now actually working for ESO in Chile; see the rest of the team members here). The ATLASGAL survey, which was in fact just recently completed giving some nice media coverage, was carried out with the 12-m ESO APEX telescope in Chile, observing at submillimeter wavelengths (870 microns). The data I used was from a catalogue published in 2014 by team member Timea Csengeri and her collaborators, also at MPIfR (do check out Timea's interesting recent papers here and here on ATLASGAL). The clumps in this catalogue represent dense condensations in the ISM, cold, massive and dense enough to form massive stars. Some of them may contain such young stars, others are quiescent (for now). We also used a set of follow-up observations of a subset of the ATLASGAL clumps, where ammonia (NH3) spectroscopy with the 100-m Effelsberg radio telescope was used to derive physical properties of the clumps, such as their temperature and turbulence. These data were published in 2012 by Marion Wienen (MPIfR) and collaborators.
By studying the locations of these clumps as compared with the bubbles, we found the following:
- Around half the ATLASGAL clumps in our sample lie near an IR bubble, and a quarter appear projected towards the rim of a bubble;
- As the bubbles grow in size under the pressure of the young stars' radiation and of the hot ionized gas, they are sweeping up the dense material out of which the stars formed. A statistical correlation analysis between bubbles of increasing size and the clumps, shows the signature of this reordering of material on a Galactic scale.
- The observed correlation shows that it's standard for star forming regions in the Galactic Plane to harbour young stars with a wide range of ages; in other words that star formation proceeds in a phased way rather than in an instantaneous burst.
- From the ammonia measurements, we find that the clumps that are found near bubbles are hotter and more turbulent than their counterparts elsewhere, and this is circumstantial evidence that these clumps are more likely to be forming stars. That finding agrees well with those of our 2012 paper. Interestingly those different properties persist to quite large distances from the bubble. If the radiation from the massive young stars driving the bubbles expansion is responsible for this, it might indicate that a substantial amount of energy is able to leak out of the bubble and into the ISM, where it could contribute to the destruction of the cloud; however there could be underlying reasons for this connection.
- Importantly, our finding that massive star formation seems to be enhanced near the rims of bubbles may be indicative of the bubble expansion driving (''triggering'') a second generation of star formation, but our data cannot prove such a causal link. Jim Dale in Munich has done some excellent work on the difficulties of proving causality in this scenario, do check out his papers if you are interested in the phenomenon of triggered star formation.
The full paper is freely available on astro-ph and will be published in the Astrophysical Journal fairly soon. I had a lot of fun with this paper, the research and presenting it to others, and had great input from my co-authors as well as numerous colleagues at conferences. And of course it wouldn't have been possible without the tens of thousands of MWP volunteers who gave up their time in the name of science. The MWP catalogue is a unique and hugely valuable dataset, and it's great to see our bubbles making an impact.
21 Nov 2015
Next Thursday, 26 November 2015, I'm the speaker at Skeptics in the Pub, Winchester. I'll be giving a talk about the James Webb Space Telescope, its history, science goals and technology.
As I'm entering my last few months in Oxford and the UK, I'm having to turn down lots of invitations to speak in the coming months. Moving across the Atlantic is becoming very real!
17 Nov 2015
As a working astronomer I get to travel the world, and this is one part of the job that makes me feel particularly privileged. Several times a year I get to travel to remote mountain tops or vibrant cities of the world, and spend time with interesting, talented and fun people. After all these years, one country still formed a hole in my map of the world visited: Australia. After all I'd heard about Australia from friends and colleagues who have visited or lived there, the country has been top of my must-see list for several years now. The final push I needed was our decision to host .Astronomy in Sydney some months ago - that was it, flights booked. So this year I finally made it to Australia, and I've not been disappointed.
I spent almost 3 weeks in Sydney, and in this time I attended 2 conferences and met many local astronomers and instrument builders from the University of Sydney, the University of New South Wales and the Anglo-Australian Observatory (AAO). I also managed to squeeze in a quick stop at Swinburne in Melbourne.
This year saw the 7th edition of .Astronomy and the first time we held the conference outside of Europe and the US, and in the Southern hemisphere - .Astro now feels properly global, and I hope we can continue to bring the conference to other parts of the world. The organisers in Australia - Amanda Bauer, James Allen, Vanessa Moss, Rob Hollow and Arna Karick - did a fantastic job of infusing .Astro with local Aussie colour and once again the conference was inspirational, eye opening and a lot of fun. More about that later.
In a nice confluence of events, .Astronomy took place the week after ADASS, a major annual conference for the astronomy data and software community now in its 25th year. The effect of this was more spill-over between the two events than I'd noted before. I was very pleased to be invited to speak at ADASS about the legacy and impact of .Astronomy. It felt all wrong, by the way, to be giving this talk instead of Rob Simpson, who has been the heart behind .Astronomy for so many years, but I was happy to be able to represent the so-called conference "brainstrust".
Writing the talk got me thinking about the "big-picture" value of .Astronomy: what have we achieved, how have we changed, where are we going? The main message I tried to convey was one of community building for the astronomy of the future. The web will be an essential aspect of storing, disseminating, exploring and analysing the large data volumes from our observational facilities (and simulations). In the era of SKA and LSST, the process of turning data into new knowledge will proceed very differently from our current methods. Optimising that process will depend entirely on having people with the right skills developing the right tools. In a sense, we've already entered the so-called data-driven era with the generations of Sloan surveys, Gaia etc, and the sheer survey speed of SKA and LSST will add the hugely under-explored time dimension into the mix.
I think the value of .Astronomy is that we bring together the astronomers who have these skills combined with an appetite for innovation. At ADASS, most participants have software development in their job description, as a result they typically have more experience, background knowledge and real-world development experience than the .Astro crowd, and I think we can learn a lot from them. So having these 2 conferences alongside each other was a great opportunity to bridge these communities. I hope we can continue that in the future.
22 Sep 2015
Today we are celebrating the official signing of the contract for the HARMONI spectrograph, one of the first-light instruments for the European Extremely Large Telescope, led by Prof. Niranjan Thatte in the Oxford instrumentation group and our friends at the UK Astronomy Technology Centre in Edinburgh. I've been part of the team for the past 2 years, working on simulations of how the instrument will perform in the study of galaxies at high redshift.
It's taken a while for the instrument projects to gather momentum, while ESO worked on getting the green light for the construction of the telescope from its Council. Given the global economic climate of the last 5 years, it's been tough to get financial commitments for such a big project, and all 3 major ELT projects (the US-based Giant Magellan Telescope and Thirty Meter Telescope projects alongside the E-ELT) have been facing some flavour of this issue. So it's very exciting that we can finally take this big leap from design study to real instrument.
There's a long and challenging road ahead, and festive occasions are few and far between in a 10-year project. We'll be enjoying this one!
15 Sep 2015
The House of Commons Science and Technology Committee is currently taking evidence from stakeholders on an inquiry into the UK's science budget. One recent submission of evidence came on behalf of STFC's Science Board, chaired by Prof Alison Davenport of the University of Birmingham. You can read the full document here, or download the PDF. With George Osborne promising to push on with his programme of austerity unencumbered by pesky coalition partners, and the research councils once again under review, the science community (myself included) are concerned about the future of the science budget in the UK. It's always good to have some numbers and facts at hand when trying to argue such things, and this document provides a useful insight into how the science budget in the coming years will affect STFC science, including astrophysics, in a concrete way.
For 5 years, the UK science budget has been protected from cuts. Given rising costs this still means a real-terms cut of around 10%, however given the scale of the austerity programme across the board science has fared pretty well these last years. The Conservatives highlighted science and innovation as a top priority in their election campaign, but their funding strategy does not always yield the best results for UK science, which requires long-term sustained funding for people as well as facilities.
It's fantastic to hear ministers speak proudly of flagship projects the UK plays a leading role in, such as the Square Kilometer Array, but science is more than buying into a collaboration or paying for a shiny new building. We need the resources to keep the lights on, fill the buildings, run the experiments, train the students, and bring the science home. It's astonishing to read that a facility like ISIS, a world-leading neutron and muon source facility at the Rutherford Appleton Laboratory is now only operated for 90 days a year, down from the optimal number of 200, for lack of funding. Without an increase in funding, ISIS faces closure in 2019/2020, and Diamond will see a decline to 70% of optimal capacity even if the flat cash arrangement is maintained, without even considering the additional operating costs required for its newest beamlines.
This is a recurring theme in Davenport's report, using the expression ``Batteries not Included'' for this funding strategy: substantial investment in new world-class projects such as high performance computing and international physics and astrophysics projects like the European Spallation Source (ESS) or the Square Kilometer Array (SKA), but no money to hire the technical and scientific staff necessary to bring the exciting new science and technology to our universities. And the country's investment in science affects far more than our scientific excellence. Our experimental physics facilities provide important services to physical and life sciences industry, and astronomers collaborate heavily with industrial partners on new projects. The whole economy can suffer.
A third of internationally-recognised astronomers in the UK now receive no funding from STFC, the number of STFC PhD studentships has declined by 25% since 2008, and fellowship schemes have been terminated. UK astronomy does extremely well in securing EU funding, but the UK's position there too faces a precarious future in the next few years. The best students and postdocs are being snatched up for trendy data science jobs, and experienced technical personnel leave for more secure and better paid positions in industry. There is little room for innovative and high-risk projects, and our credibility as reliable long-term partners in international collaborations is under threat. The report estimates that an additional £18m per year in STFC's annual resource budget of £400m would restore the programme to healthier (but still squeezed) 2010 levels - a pretty modest rise.
Politicians speak highly of UK excellence in science, but our current reputation is the result of investment 10-20 years ago - the LHC in the 1990s, Diamond in the early 2000s. The true consequences of the decline in funding since 2010 will only be felt in the next decade. The UK's science spend has dropped to the lowest level in the G8 countries as a percentage of GDP. Science and innovation are a long-term game, and it's important that we raise awareness as a community of the consequences of the current research funding climate. I note that the Science is Vital group is once again stepping up to the plate, with an event planned on 26 October at Conway Hall in London. I'm out of the country that day sadly and many times zones away, but I'm sure it'll be a worthwhile evening for all those who care about the future UK science.
08 Sep 2015
Top of the Arxiv this morning is a great paper I was happy to collaborate on with Adam Ginsburg (ESO) and a large team of scientists from around the world, showing new temperature maps of the Central Molecular Zone. The Central Molecular Zone, or CMZ, occupies some 500 pc around the centre of our Galaxy (around 1600 light years), which hosts around 10% of all the molecular gas in the Galaxy. We know that the gas clouds in the region are hotter than similar clouds further out in the Galaxy, and because of the strong gravity so close to the Galactic Centre they show high velocities and strong turbulence. The conditions are not too dissimilar from what we observe at the centres of other galaxies, in particular galaxies in the early Universe; as such the CMZ is a useful local template for these distant galaxies.
These new maps are the result of 150 hours of observations with the sub-millimeter APEX telescope in the Atacama desert in Chile, and they are the largest consistent temperature maps of the CMZ to date. The temperature was derived from spectral line observations of formaldehyde (H2CO) using a combination of measurements and modelling. The whole data processing and analysis procedure was a major effort and much kudos to Adam for doing a phenomenal job. Overall the maps are broadly consistent with previous measurements using different molecules, but no previous studies have covered such a large area of the CMZ with one campaign so many aspects of the measurements are completely new.
The data will be a fantastic reference set for scientists studying other aspects of the CMZ, such as star formation and cloud dynamics, as well as those studying the conditions at the hearts of other galaxies. Together with today's paper, the data, maps and all the source code used in the project have been made publicly available.
05 Sep 2015
I think it's fair to say that the average astronomer's knowledge of statistics falls short of what's required for the big data-based research many of us are increasingly creeping into. Some of us take action and sign up for one of the excellent statistics-focused meetings or summer schools that have sprung up in recent years: the 12-step Rehab Programme for the Statistically Challenged Astronomer, seeking help after Hitting Rock Bottom having found their work disproven by 5 lines of Python code from the eager hands of the new summer intern who daily chooses her breakfast cereal via Markov Chain Monte Carlo. The rest of us just soldier on, silently praying that our executioner will be kind, and not in a position to decide on our next promotion.
I currently have a statistics-heavy paper going through peer review - a long overdue follow-up to my 2012 paper examining correlations between the locations of bubbles in the interstellar medium of the Milky Way Galaxy (as identified by our Milky Way Project volunteers) and other markers of high mass star formation. In the new paper, I examine the distribution and physical properties of cold dust clumps near to and away from those bubbles, using sub-millimeter data from the ATLASGAL survey.
About a week after submitting the paper to ApJ I received a first round of comments, not from the standard anonymous referee, but passed on from the journal's Statistics Editor. Whilst it means I now have two sets of comments to address, and I will probably grumble about that at a later time, the specific feedback on the statistical methods I've used is more in-depth and helpful than I've had for other papers. Apparently this is a relatively new practice at the journal, and based on this recent experience (bearing in mind the danger of extrapolating from one datapoint), one that I wholeheartedly support. There are too many papers in the literature that use overly simplistic, inappropriate or inadequate statistical methods - and yes, I'm sure that includes some of my own efforts.
It's nice to see a journal play an active role in improving the quality of the science presented in the literature, and it's made me a little more confident that Kendrew et al 2015b will not be the cause of my statistical downfall.
01 Sep 2015
An article in the Guardian Higher Education section grabbed my attention in the last few days: a debate about whether PhD students in the UK should be classified as employees. I've worked in countries that take different approaches: I myself was a PhD student here in the UK, with student status, whilst in the Netherlands, where I did my first postdoc, our PhD students were classed as employees. The major advantage to PhD students being employees is that they pay into the social security system of their country - pension, healthcare and such - and are protected by employment legislation. This can have a big knock-on effect later in life. As the proponent of employment status in the article also points out, not having a taxable income can present problems when e.g. buying a house.
More subtly, it might change the status of PhD students in a department or research group: rather than work towards writing a thesis mostly for their own benefit, they'd be seen as a more integral part of the research workforce. To me this makes sense, as the day-to-day business of research resembles "a job" more than "an educational course", and students' contributions are often invaluable to the outcomes of a research project. If a PhD were seen as a transition in employment, rather than a drastic move back into education, it might also make it easier and more attractive for older, more experienced professionals to re-enter universities and get PhDs.
Classing PhD students as employees would make them more expensive of course, possibly reducing the overall number that can be taken on. I'd be interested in seeing the calculations for that. As the opponent in the Guardian piece points out, foreign PhD students might then also count towards any immigration quotas, though I don't see why there couldn't be an exemption for them. And students themselves would have to come to terms with losing "student benefits" like council tax exemptions, cheap overdrafts and other financial perks. The question of self-funded students could pose some problems too, though I expect that the number of students funding their own way through a PhD without needing any kind of employment is very small.
I'd be interested in learning more about how different countries arrived at the systems they use, and what is says about how they perceive the role of PhD students in education and research, and their value to the country's economy as a whole.
31 Aug 2015
I kept a blog for many years called One Small Step, where I wrote about new results in astrophysics, my own work, and community and cultural issues in our field. I felt it didn't really reflect what I wanted to write about very well anymore, so I closed it down earlier this year.
As I enjoy writing, I created this page where I will continue to post bits of news and thoughts.