Sister blog of Physicists of the Caribbean. Shorter, more focused posts specialising in astronomy and data visualisation.

Wednesday 31 October 2018

The importance of good science journalism

This is an ideal case, of course, but no less important for that. In such an ideal scenario, time currently spent writing grant proposals would be spent on outreach. It's probably easier to turn scientists into journalists than the other way around, but at the same time, journalists bring a much wider perspective.


Scientists and journalists share a passion for questioning assumptions and biases. We are trained to uncover hidden narratives in the pursuit of deeper understandings. And we share an enthusiasm for revealing new knowledge that can be shared with the world.

These values cannot be taken for granted, especially in our current political environment. It is no secret that both scientists and journalists are facing a concerted wave of allegations around “bias” and “fake news.” This type of regressive criticism is not new. Throughout history, those who have sought to suppress the truth have endeavored to muffle the voices of scientists and journalists. Without these voices societies decay. Therefore, when confronted with the current assaults, we cannot allow ourselves to recoil into our protective harbors and wait for the storm to pass. We cannot wait for others to step into the void. We have to shrug off whatever reluctances we may have and find ways to share the stories of science with a world in desperate need of hearing them.

We recognize that there are differences between the ways journalists and scientists perform their professions, and those differences could serve as barriers for cooperation. Scientists often are wary of the way their work might be presented by journalists. They have seen nuanced research oversimplified or hyped for more dramatic (and sometimes misleading) headlines. At the same time, journalists can be frustrated by scientists who respond to straightforward questions with jargon and are unable or unwilling to explain the essence of their discoveries without caveats and qualifiers.

We believe, however, this mistrust is superficial and can be overcome for the benefit of all of society. Scientists and journalists share core aspirations. Both disciplines are about observing the world, questioning the unknown and collecting facts. Both scientists and journalists know their work is built on the work of others and they must find a way to share their discoveries. Scientists may tell their stories in papers they publish to share with their colleagues in the field. Journalists may tell their stories in print, radio or film, often trying to reach as wide an audience as possible. But the mission is the same. Knowledge can only have an impact if others hear about it.


As far as journalism goes, it seems to me that poor science reporting is (mostly) simply due to ignorance. Maybe there ought to be more outreach courses aimed at journalists. Of course you need experts to tell you about the technical details and the results themselves. But beyond that, many of the techniques of critical analysis aren't that hard.

From the political perspective something much more sinister looks to be going on. It feels less of a case of simple ignorance and more of wilful bullshitting : not caring about the evidence rather than (but not excluding the case of) not understanding it. It's not difficult to understand, say, that something being possible doesn't mean it isn't fantastically unlikely, or that because something did happen once it doesn't mean that it happened much less often than other incidents. False degrees of confidence in or against a result aren't because politicians don't understand this, it's because they don't care (not always out of malevolence or even stupidity, but sometimes). When you strip away the objective evidence, all you have is subjective, emotion-driven ideology. And where it may be difficult to argue with a fact, it's easy to argue with an emotion.

That's not to say that there aren't media outlets that are hugely partisan and essentially nothing but the mouthpieces of their favourite political tribe : there are. These institutions attempt to discredit science but only as part of a larger campaign of discrediting anyone and anything (from any field) that even hints at disagreement with their moral values. Anyone who says otherwise, regardless of their status, is branded as a member of the controlling elite, and conversely, anyone agreeing with them is One of The People. They don't actually care a damn about The People, of course; mostly this kind of rhetoric is used by people who are far more out of touch than the "elite" they like to deride. It is merely a rhetorical tool to sow division, nothing more. The underlying theme is one of avoiding and ignoring the evidence, because even imperfect evidence is, if analysed sensibly, a damn sight harder to argue with than a whimsical feeling.

So yes, improving science journalism is important. But this is only one expression of the root problem, not the problem itself.


https://blogs.scientificamerican.com/observations/what-journalists-and-scientists-have-in-common/

Thursday 18 October 2018

The Big One-Zero

Submitted my tenth paper as first author :

Faint and fading tails : the fate of stripped HI gas in Virgo cluster galaxies

Although many galaxies in the Virgo cluster are known to have lost significant amounts of HI gas, only about a dozen features are known where the HI extends significantly outside its parent galaxy. Previous numerical simulations have predicted that HI removed by ram pressure stripping should have column densities far in excess of the sensitivity limits of observational surveys. We construct a simple model to try and quantify how many streams we might expect to detect. This accounts for the expected random orientation of the streams in position and velocity space as well as the expected stream length and mass of stripped HI. Using archival data from the Arecibo Galaxy Environment Survey, we search for any streams which might previously have been missed in earlier analyses. We report the confident discovery of nine streams as well as sixteen other less sure detections. We show that these well-match our analytic predictions for which galaxies should be actively losing gas, however the mass of the streams is typically far below the amount of missing HI in their parent galaxies, implying that a phase change and/or dispersal renders the gas undetectable. By estimating the orbital timescales we estimate that dissolution rates of 1-10 M⊙ yr−1 are able to explain both the presence of a few long, massive streams and the greater number of shorter, less massive features.

And now to pray to the Journal Gods for a fair and fast referee....

Wednesday 10 October 2018

A Volumetric Law For Star Formation

It's well-known that there's a correlation between galaxy gas density and star formation rate. The problem is that no-one's clear on exactly what sort of correlation it is, or what sort of gas it is. In general, galaxies which have significant amounts of atomic hydrogen (which is relatively warm) tend to be forming stars, so there's definitely some sort of connection there. But recent studies have found the correlation is much better when considering only the colder, molecular hydrogen, which gives a much nicer linear relation. And that makes physical sense too, since to form a star you need higher gas density, which is easier if the gas is cold as it can't use thermal pressure to support itself against collapse. Perhaps most convincing were the discovery of holes in the atomic gas component of some spiral galaxies, which seem to be the result of star formation consuming all the gas. Also, the atomic gas has a strict upper density limit, beyond which all gas seems to become molecular.

The shape of the correlation between the gas and star formation rate is somewhat unclear as well. Mostly it's a nice power law, but there's some evidence for a density threshold below which the star formation activity drops sharply. This, say the authors of this work, is quite controversial (more so than I realised, and I'm supposed to know about this stuff), as is the choice of which gas component to use.

There are lots of uncertainties, but perhaps the main one is the gas density (of either the cold or the warm component). We can estimate the gas density per unit area (surface density) easily enough, but the true volume density is much harder because we can't directly measure the thickness of the gas disc. Here the authors attempt to overcome this. They assume the gas is in hydrostatic equilibrium, meaning that its outward pressure (due to thermal and other motions) is balanced by its tendency to collapse under gravity. This isn't straightforward : it requires detailed knowledge of the mass and distribution of stars and dark matter as well as that of the gas, and also it needs the velocity dispersion and overall rotation curve of the gas. This is currently only possible for quite nearby galaxies since you need very detailed, well-resolved data to do this properly. Even then there are still uncertainties and assumptions that have to be made.

This paper is under review, but it seems to me to be a careful, detailed work more in need of correcting typos than methodological revisions. After describing their methods with considerable precision, they find that both the atomic and molecular components show very clear, power-law correlations with star formation. There's no change of slope with density either. They say this could be because the thickness of the gas disc varies significantly depending on where you are in the galaxy : it's much fatter in the low-density outskirts than the centre. The surface density measurement would give a misleadingly high estimate in the outer regions.

The fact that both warm gas correlates with star formation is also very interesting. Previously the tendency had been to assume that this connection would be somewhat secondary : the picture has been shifting to the atomic gas having to transition to molecular gas before forming stars. So the correlation is expected to be rather rough, but in fact it's very clear - certainly no worse than that of the molecular gas. They give two interpretations :
- The warm gas is a good tracer of the cold gas. The connection between atomic gas and star formation could then still be indirect. It would also mean that there could be undetected cold gas (which is very difficult to detect directly - normally other components have to be used) in the outskirts of galaxies, where star formation activity has previously been puzzling.
- The warm gas can form stars directly. This is theoretically possible : there are conditions under which the warm gas could cool so quickly that there's no time for molecular gas to form and it goes directly into stars.

There's a lot of work to be done, but this isn't the only evidence for atomic gas being directly involved in star formation. The idea that actually this complex process is governed by a rather simple condition - true density - but that this condition is hard to measure is very appealing.
https://arxiv.org/abs/1810.03616

Tuesday 2 October 2018

"Freedom from" versus "freedom to" in the world of science journals

A central charge, from some publishers and some academics is that Plan S is an infringement of academic freedom to choose how and where your work is published and it therefore unethical.

Blink.

Whut ?

Kudos to the author of this piece for the detailed legalistic analysis of why this is wrong, but surely from an ethical standpoint this is Bloody Obvious ?

As I understand it, the Plan calls for all publically-funded research to be made Open Access, i.e. freely available to the public. Since the public funded the research, they ought to get to read it if they want to. As far as I know it doesn't affect private research, and nor should it. If you privately commission a study, I don't think you're invariably, necessarily obligated to release its findings or data (though that's not to say there might not be some cases, e.g. legal proceedings, in which release could be demanded) to the public. But you wouldn't expect the researchers to turn around and say, "I've published the findings in this journal you can't read, because I'm exercising my academic freedom". You'd feel a common-sense entitlement to see what you'd paid for, unless for some strange reason you'd previously agreed an exception with the researchers. Could happen, but unlikely. Generally speaking you'd say the researcher was being unethical by denying your right to inspect the findings.

And so if the public fund research and the researcher has the option and ability to make it publicly visible, then the default expectation should be that it will be public. For them to actively choose an alternative, unless their are compelling reasons to do so (currently Open Access is frickin' expensive), is clearly unethical. Removing a freedom to do an unethical thing isn't itself a fundamentally unethical act - it's normally known as, for instance, "justice". Unless I'm missing something obvious, I find this "infringes academic freedom" argument to be so stupid I can't believe this is really what's bothering them, even if they think it is (with the possible exception of a few Randian devotees).

People are weird.

http://occamstypewriter.org/scurry/2018/10/01/academic-freedom-and-responsibility-why-plan-s-is-not-unethical/

Back from the grave ?

I'd thought that the controversy over NGC 1052-DF2 and DF4 was at least partly settled by now, but this paper would have you believe ot...