How big were the biggest galaxies in the early Universe?

Once upon a time (over a decade ago when I was still in Cardiff), I wrote a paper with PhD student Ian Harrison on the biggest (most massive) galaxy clusters. I even wrote a blog post about it. It was based on an interesting branch of statistical theory called extreme value statistics which I posted about in general terms here.

Well now the recent spate of observations of high-redshift galaxies by the James Webb Space Telescope has inspired Chris Lovell (who was a student at Cardiff back in the day then moved to Sussex to do his PhD and is now at the University of Hertfordshire) and Ian Harrison (who is back in Cardiff as a postdoc after a spell in the Midlands), and others at Cambridge and Sussex, to apply the extreme value statistics idea not to clusters but to galaxies. Here is the abstract:

The basic idea of galaxy formation in the standard ΛCDM cosmological model is that galaxies form in dark matter haloes that grow hierarchically so that the typical size of galaxies increases with time. The most massive haloes at high redshift should therefore be less massive than the most massive haloes at low redshift, as neatly illustrated by this figure, which shows the theoretical halo mass function (solid lines) and the predicted distribution of the most massive halo (dashed lines) at a number of redshifts, for a fixed volume of 100 Mpc³.

The colour-coding is with redshift as per the legend, with light blue the highest (z=16).

Of course we don’t observe the halo mass directly and the connection between this mass and the luminosity of a galaxy sitting in it is likely to be complicated because the formation of the stars that produce the light is a rather messy process; the ratio of mass to light is consequently hard to predict. Moreover we don’t even have overwhelmingly convincing measurements of the redshifts yet. A brief summary of the conclusions of this paper, however, is that is some of the big early galaxies recently observed by JWST seem to be a big too big for comfort if we take their observed properties at face value. A lot more observational work will be needed, however, before we can draw definite conclusions about whether the standard model is consistent with these new observations.

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Remembering Charles Byrd

Most of the belongings I’ve just had delivered to Maynooth are of sentimental rather than financial value so I suppose it was inevitable that I’d get a bit sentimental opening them up. The painting above is by a Cardiff-based Welsh artist called Charles Byrd and it was painted in 1963, the year of my birth. The story of how it came into my possession over a decade ago can be found here.

I unpacked this yesterday along with most of my other artwork but I haven’t decided where to put it yet so it’s sitting on my desk until I decide where to put it.

It was with some sadness that I found out recently that Charles Byrd passed away in 2018 at the age of 101. There’s a nice little tribute to him here. I found out reading it that in the least years of his life he lived in a little flat on Llandaff Road, very close to where I lived in Pontcanna, though I never met him, which is a shame because he seems to have been quite a character!

Rest in peace, Charles Byrd (1916-2018).

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Packing Up

Inventory

So here I am sitting in a virtually empty house in Cardiff, the bulk of my worldly goods now in transit to Ireland. The house seems a lot bigger with nothing in it. It also feels a bit strange to see all your possessions listed in an inventory.

The 9th and 10th of August were the first opportunities to do the removal from my Pontcanna residence, so I flew over at the weekend to be here to supervise the packing. I paid for the removals firm to do the actual packing, which was well worth the extra money. The company told me it would take two full days to pack up, which surprised me. In fact they did most of it on Monday arriving at 9.30am and departing around 3pm. Yesterday they arrived at 8.30am and were finished by 10.30am. They could easily have done it all in one day but they only had a smallish van which they filled up before leaving on Monday.

My stuff now gets stored in a container in a warehouse for a couple of weeks or so before being delivered to Maynooth by ferry. They’re doing this removal as a return load, which means waiting for a lorry to arrive to the UK from Ireland which would otherwise return empty. Taking my stuff on the return journey makes it more efficient for them and also quite a lot cheaper for me. This seemed the best option as I am not in a particular rush to receive delivery. I’ve waited a year so a couple more weeks won’t matter!

The fact they finished early yesterday got me out of an awkward situation. The powers that be scheduled three repeat examinations simultaneously at 2.30pm yesterday so I assumed I would have to be scrabbling around with my mobile phone in amongst the boxes and packing materials, which might have been awkward.

As it turned out I had plenty time to walk across Bute Park to Cardiff University where a former colleague in the School of Physics & Astronomy was kind enough to let me use an empty office and eduroam did the rest. All three papers passed without incident, and I had the added bonus of a few pints in the Flute and Tankard afterwards.

Yesterday was A-level results day so there was much talk about the new academic year. It seems Cardiff University is going to resume face-to-face teaching in September. I hope the School of Physics & Astronomy gets a good intake of first-years and that all goes well for all students and staff as they prepare to resume some form of normality. Cardiff has been very good to me over the years and I wish everyone there all the best for the future.

Incidentally I popped in to the Data Innovation Research Institute (where I used to work) while I was at the School of Physics and Astronomy, just to see if I could say hello to anyone I used to work with. The office is just over the other side of a car park from the Queen’s Buildings. I found that the folks are being relocated from the old office to a new building along with Mathematics and Computer Science up near Cathays Station. There was only one person there, packing up his stuff for removal…

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Back to Civilisation

So last night I returned safely from Cardiff to Ireland via Birmingham. Travel both ways was relatively uneventful. There can’t have been more than 30 people on the flight in either direction. I did however almost screw up the return flight by omitting to fill in the obligatory Covid-19 passenger locator form which I hadn’t realised is now online-only. I only found out that I had to do it before they would let me on the plane, resulting in a mad scramble with a poor phone connection to get it done. After a few goes and quite a bit of stress I succeeded and was allowed to board, conspicuously the last passenger to do so. We still managed to leave early though, and the short flight to Dublin – passing directly over Ynys Môn was relaxing and arrived on schedule; the immigration officer scanned my new-fangled Covid-19 vaccination certificate but wasn’t interested in the passenger locator form that caused me so much stress on departure.

I returned to Cardiff to take a bit of a break, to check up on my house and also prepare to move the rest of my belongings to Ireland. I was relieved when I got there last week that everything was basically in order, although there were lots of cobwebs and a very musty smell, which was hardly surprising since I hadn’t been there for 15 months. The inside of the fridge wasn’t a pretty sight either.

One night last week after meeting some friends for a beer in Cardiff I walked back via Pontcanna Fields and saw, much to my surprise, Camogie practice in progress in the twilight:

Camogie Practice, Pontcanna Fields, Cardiff.

The logistics of my planned removal proved a bit more complicated than I expected but eventually I cracked it and all the arrangements are now in place. I should receive delivery here in Maynooth next month. I’m doing it on the cheap as a part-load, which is why it will take a bit longer than usual.

Cleaning and packing was very hard work owing to the intense heat over the last week or so – it was regularly over 30° C – during the day, so I took quite a few siestas. My neighbours tell me it’s been much the same here in Maynooth, although it is a bit cooler today, around 20° with a very pleasant breeze.

Despite the hard work it was nice to have a change of scenery for a bit and also to meet up with some old friends from Cardiff days. Everyone has been in a state of limbo for the last 18 months or so, and although we’re not out of the woods yet there are signs of things coming back to life. When I went to Bubs in Cardiff for a drink last week it was the first time I’d been inside a pub since February 2020!

Incidentally, most people I saw observed social distancing, wore masks, etc. The rules in Wales are still fairly strict. Although open for indoor service, bars and restaurants seem to have few customers. Some people on trains to and from Birmingham didn’t wear masks. One group of unmasked and obnoxious English passengers on my return journey were loudly boasting how backwards Wales was compared to England, where the rules have relaxed despite a huge surge in cases. I moved to another carriage.

The only other thing I managed to do was attend a Royal London One-Day Cup match at Sophia Gardens between Glamorgan and Warwickshire in the baking heat of Sophia Gardens. It turned out to be a good tight game, with Glamorgan winning by 2 wickets courtesy of two consecutive boundaries. Most of the time I was sitting there in the shade I was thinking how glad I was not to be fielding in such conditions.

One thing that was very noticeable during my stay in Wales was that it was very hard to get fresh salad vegetables and the like. That may be partly due to weather-related demand or it may be due to a shortage of lorry drivers or other staff owing to Covid-19 isolation requirements and may be a consequence of Brexit. Who knows? I’ll just say that there’s been hot weather in Ireland, where the Covid-19 pandemic is also happening but there are no reports of shortages of fresh food here. I’m very much looking forward to having a nice salad with my dinner this evening.

Anyway, I suppose that’s enough rambling. At some point I’ll have to open up my email box to see what horrors lurk therein. Still can’t be worse than the fridge I opened last week. Can it?

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Weekend Weather and Travel Updates

I got back from London to Dublin last night, rather later than planned courtesy of Storm Dennis. I made my way to Heathrow more in hope than expectation, as there seemed to be a significant probability that my flight would be cancelled (as several were), but in the end it was only delayed by about an hour. It was a bit wobbly coming in to land, but the weather in Dublin wasn’t all that bad last night so there wasn’t the level of drama I expected. I did miss the last Hopper bus, though, and had to take a taxi to Maynooth.

There was another bit of disruption earlier in the day when I discovered that there were no Piccadilly or District line trains between Hyde Park Corner and Acton Town (in either direction), which makes it impossible to get to Heathrow directly by Tube. That gave me an opportunity to explore the London Underground to find a way through. I had plenty of time so I thought it would be fun. In the end I chose the Central Line to Ealing Broadway then a quick couple of stops on the District Line to Acton Town where there were trains to Mornington Crescent Heathrow Airport.

Dublin is to leeward when bad weather comes in from the Atlantic, so doesn’t get the worst of it. This seems to have been the case for Storm Dennis. Wales hasn’t been so lucky and I’ve spent the morning following messages on social media from friends and former colleagues about flooding along the Rover Taff. At one point there were 85 active flood warnings in Wales:

When I bought my house in Pontcanna I signed up for Flood Alerts, and I got one of them too. Here are some pictures of the area taken this morning:

Pontcanna Fields, Cardiff underwater this morning after Taff bursts its banks at Blackweir. Photos by Geoff Gobody/Jemima Tulip on FB. #StormDennis pic.twitter.com/EBB5lVxYRg

— I Loves The ‘Diff (@ILovesTheDiff) February 16, 2020

This grim scene is not far from my house, but it’s not as scary as it looks. The River Taff is flanked by steep embankments as it passes into Cardiff and these provide strong flood defences. There is also a tidal barrage across Cardiff Bay which prevents tidewater coming up the River Taff while floodwater is trying to come down it, which is the usual recipe for a flood. The whole system is designed so that before these are breached, water floods out further North over Pontcanna Fields (a wide flat area that is part of the natural flood plain of the Taff that doesn’t have houses on it). A huge amount of water can be `parked’ in this area until the spate subsides. This happened before when I lived in Cardiff in 2009 and it’s nothing to worry too much about. It’s not good for people wanting to play rugby on the playing fields though!

After the terrible floods of 1979 Cardiff built very strong flood defences, but the same is not true for smaller towns up in the Welsh valleys. It seems that Pontypridd has been particularly badly hit this time. There seems to be no political will to spend money protecting such places, which in my view would be far more worthwhile than building HS2.

This all reminds me of the time when I first moved in to my house in Pontcanna over a decade ago. Late one rainy evening the phone rang and it was an automated flood warning. I responded by doing everything the message told me not to do: I put on my coat and went to the river to see what was happening. It’s only a ten minute walk from my house to the embankment. When I got there, I found a crowd of about a dozen people watching. The river was only about a metre below the level of the embankment as it roared its way down to Cardiff Bay carrying along tree trunks, car tyres and various other items of rubbish. It was quite impressive, but I didn’t watch for long as it was very cold and wet.

I’m told that the worst part of the 1979 flood was not the surface water, but the fact that the drainage system couldn’t cope and sewage backed up into the houses and streets. That must have been horrible as well as causing a serious health hazard.

Update: I heard last night that the level of the Taff on Sunday was 80cm higher than it was during the 1979 floods.

Anyway, I was glad I did get back last night as today I am giving a talk at the Joint Congress of University Astronomical Societies. I’d better get on and write it!

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Cardiff Pride!

I got up early this morning to fly back to Cardiff in time for Cardiff Pride, this being the twentieth such event in Cardiff. I was a bit worried I wouldn’t make here before the start of the Parade but I did, with time to spare. St Mary’s Street was quite a sight with all the rainbow flags.

The parade gathered on North Road this year before it got moving and it extended all the way from the castle to the Royal Welsh College of Music and Drama:

This is the reflection in one of the windows of the RWCMD building..

Not being in the parade myself, when it got going I moved to St Mary Street to watch it go by. It took so long for the front to arrive I started to worry something had happened, but eventually it appeared..

I watched a while enjoying the colourful sights and fun sounds before walking to Pontcanna for lunch.

It’s a lovely warm and sunny day for the carnival and concerts that take place this afternoon and evening so I’m sure everyone there will have a great time!

Me? I’m obviously too old for that sort of thing and will celebrate the occasion with appropriate indoor activities (if you know what I mean) but the least I can do is wish Cardiff Pride a very happy 20th birthday!

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Health and the Season

After I came out as having arthritis a few months ago, I’m sure all both my readers are agog to hear news about the state of my knees. There’s only good news to report, actually. The warmer weather seems to have brought considerable respite. I have not taken any anti-inflammatory medicine for a couple of months now, and have largely dispensed with the walking stick too (at least for the time being). I still get the odd twinge, but nothing compared to what things were like during the winter.

I ended my earlier post about this with this paragraph:

One other thing worth mentioning is that this condition does seem to be highly temperature-dependent. This last week the weather suddenly turned a lot colder and the arthritis definitely got worse. Perhaps in future I could learn to use the colour of my knees as some kind of forecasting method?

Talk to anyone who suffers from arthritis and they will tell you a similar story – it gets worse in cold and/or damp weather. Talk to any medical expert, however, and they will tell you that there’s very little hard evidence about this and what evidence there is suggests that the effect is very weak. See, for example, this paper, which has the following abstract:

It is a common observation that pain and stiffness in patients known to have arthritis get worse in cold and damp weather conditions. The objective of this article is to review the available literature on this subject and to put forward an explanation for this common clinical finding. Literature search revealed twelve relevant articles including laboratory experiments and prospective questionnaire-based human studies. Various investigators have tried to study the effect of cold weather on arthritic symptoms and have suggested different theories. The effect of temperature changes localized to the joints has shown to increase stiffness at lower temperatures and decrease stiffness at higher temperatures. The effect of these changes has been found more pronounced in elderly population with arthritis and patients with advanced disease. The evidence to support this common observation is weak; however some studies have reported a trend towards worsening of pain and stiffness with falling temperature and barometric pressure in arthritic patients.

Among the problems associated with studying such effects is the issue of how to measure `pain’ in a reliable way. It may be in the winter people are generally less upbeat about their health which may affect the way they self-report the state of their arthritis. And even if one could measure the level of pain objectively, there are obvious confounding factors: people are generally more active during the summer months, for example, which may help ease joint pain. And what aspect of the weather really matters: temperature, humidity or atmospheric pressure? These tend to be correlated in complicated ways.

All I can say is that the last couple of months have been far better for me. Whether that is because of some direct causative influence of the weather or not I can’t say.

While I am on about health and the time of year, I’ll comment on another personal matter. Seven years ago I was suffering some serious mental health problems, which resulted in me being for some time on an acute ward in a psychiatric institution. That happened in July 2012. I’ve dreaded the arrival of July every year since because it reminds me of that very bad period in my life and I worry that might bring on something similar again. This year, though, has been much better. I can’t attribute this entirely to my move here to Ireland, but the change of scene has undoubtedly contributed.

As a final comment I’ll just say that 31st July was the third anniversary of my leaving Sussex (in 2016) to return to Cardiff on a three-year part-time contract back. I was planning to take early retirement when that expired, but things seem to have turned out rather differently. Things have a habit of doing that. Then again, if life were predictable it would be very dull. Anyway, it was very nice to meet up with quite a few former colleagues from Cardiff during recent week off, including at their summer barbecue at Llandaff. It seems quite a few will be spending the next week or so marking repeat resit examinations, so let me take this opportunity to wish them all the very best!

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The End of the Common Travel Area?

I’m back in Cardiff for a couple of days after flying from Dublin this morning.

When my flight arrived at Cardiff Airport there was yet again a full passport and immigration check on all passengers.

There is supposed to be a Common Travel Area including the UK and Ireland (as well as the Channel Islands and the Isle of Man), and passport checks are not supposed to be made routinely at borders within the CTA.

I have noticed passport checks happening at Cardiff Airport before (e.g. here and here) but I’ve previously imagined there was some specific reason for them. Passport checks have, however, been carried out every time I have arrived in Cardiff recently and it is now abundantly clear that there has been a material change of policy.

When I got to the desk and handed over my passport I asked the Officer whether these checks were being imposed all the time now. She said yes: there are now full passport and immigration checks on all flights to Cardiff from Dublin.

This is from the UK Government’s website:

Well, if they check all passengers on all flights then that sounds like ‘routine’ to me. In other words the British authorities are violating the Common Travel Area agreement just weeks after undertaking to uphold it.

Did someone say ‘Perfidious Albion’?

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Walter’s Leaving Do

As I had little window of opportunity before the start of exam marking season and other goings-on in Maynooth I decided to make a quick trip back to Wales back in Cardiff for the weekend.

I flew back on Thursday evening. It had been a busy day and I’d only had a sandwich for lunch so I went into the bar in Dublin Airport to get a beer and a burger. Who did I bump into there but Professor Walter Gear…

Walter was Head of the School of Physics and Astronomy at Cardiff University when I joined it in 2007, so and was he persuaded me to leave Nottingham. He was a very good Head of School and, in particular, he helped a lot when I had mental health problems seven years ago.

Anyway after twenty years in Cardiff during which he built up the School and particularly the world-leading Astronomy Instrumentation Group there, Walter has left for a new position as Dean for Science and Engineering at NUI Galway, in Ireland.

He was in Dublin Airport because he was travelling back to his leaving do in Cardiff, which I turned up for on Friday. There were drinks and speeches and presents and it was nice to see some old friends there and in the Flute and Tankard afterwards. It was a good send-off.

I’m sure that Walter (who was born in Ireland) enjoy his new role in the Emerald Isle very much indeed. Galway is quite a distance from Maynooth (almost 200 km) but I hope we will be in regular contact.

Anyway I should mention that there are advertisements out for a Research Associate in Sub-mm Astronomy and and a Lecturer in Astronomy (with an emphasis on the same) in Galway. I’m sure these will prove very attractive to many applicants!

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Back to Sunny Ireland

Well here I am, back in Maynooth, after a week’s restful leave in Cardiff. The weather here is just as nice as it was in Wales when I left yesterday: sunny and about 20 degrees. I’m enjoying the warm weather very much indeed, as my arthritis seems to have eased off considerably.

I was planning to return to Ireland today (Monday) but the flights were far cheaper yesterday. The plane I took yesterday (Sunday) less than half full. Incidentally, after their recent rescue and restructuring FlyBe have announced that after this summer they will no longer operate jets from Cardiff. Flights to Dublin will therefore be by their smaller Bombardier turboprops rather than the Embraer aircraft that I took yesterday.

Today is a Bank holiday in Ireland, as it is in the UK, but after that the Easter break is over; I’m officially back to work tomorrow. This semester will have been divided into three pieces, firstly by the half-term study week (around St Patrick’s Day) and now by a one-week Easter break. Last year these two breaks were contiguous, but Easter is quite late this year so they are separate this time.

Anyway, we now have three weeks of teaching left followed by the May examination period and, of course, the inevitable Marking of the Scripts.

The three remaining weeks include two Bank Holiday Mondays including today, Easter Monday, and the May Day Holiday on 6th May). I have lectures on Mondays I will miss two sessions, leaving only seven lectures remaining for Engineering Mathematics. I’d better make sure that in the short time remaining I cover everything that is in the examination!

Anyway, although it’s a holiday I’ve got to get my lecture together for tomorrow morning so I’d better get to work. It’s a shame not to be out and about in the sunshine but there you go. That is the price you pay for having a week off. No doubt there is a ton of emails to reply to as well; I’ve tried not to look at my inbox while I’ve been off. I’ve made that a rule for holidays now: put the out of office message on and leave the email alone!

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