Archive for ESO

Page Charges at A&A…

Posted in Open Access, The Universe and Stuff with tags , , , , on May 27, 2020 by telescoper

 

It was recently drawn to my attention that UK-based astronomers and astrophysicists now have to pay a charge of €100 per page (!) to publish in the journal Astronomy & Astrophysics (usually known as A&A for short). See their page charges information for details.

Contrary to popular belief, A&A only waives page charges for authors from countries who are sponsors of A&A, not all countries who are members of the European Southern Observatory (ESO) project. Although the United Kingdom is a member of ESO, it is not and never has been a sponsor of A&A: see the list of sponsoring countries and their representatives here .

Until recently, however, UK authors did have their page charges waived on what seems to have been an ex gratia basis. For some reason, that exception has now apparently been removed.

UPDATE 1: It should have occurred to me that that this also applies to authors from Ireland.

UPDATE 2: Apparently the liability for page charges is determined by the nationality of the first author. I had previously thought that if any of the authors belonged to a sponsoring country then charges would be waived.

Meanwhile, the Open Journal of Astrophysics publishes entirely for free and we are committed to continuing that way. You know what to do.

The Case for Irish Membership of CERN

Posted in Politics, The Universe and Stuff with tags , , , , on November 16, 2019 by telescoper

In the news here in Ireland this week is a new report from a Committee of the Houses of the Oireachtas making the case for Ireland to join CERN. You can download the report here (PDF) and you’ll find this rather striking graphic therein:

You will see that there are only three European countries that don’t have any form of membership or other agreement with CERN: Latvia, Bosnia-Herzegovina and Ireland. The fact that almost everyone else is in is not in itself necessarily a good argument for Ireland to join, but it does make one wonder why so many other countries have found it to join or have an agreement with CERN while Ireland has not.

As the document explains, if the Irish government  were to decide to take Ireland into CERN then  it would first have to become an Associate Member, which would cost around €1.2 million per year. That’s small potatoes really, and  the financial returns to Irish industry and universities are likely to far exceed that, so the report strongly recommends this step be taken. This Associate member stage would last up to 5 years, and then to acquire full membership a joining fee of around €15.6 million would have to be paid, which is obviously a much greater commitment but in my view still worthwhile.

While I strongly support the idea of Ireland joining CERN I do have a couple of concerns.

One is that I’m very sad that the actual science done at CERN is downplayed in the Oireachtas report. Most of it is about return to industry, training opportunities, etc. These are important, of course, but it must not be forgotten that big science projects like those carried out at CERN are above all else science projects. The quest for knowledge does have collateral benefits, but it a worthy activity in its own right and we shouldn’t lose sight of that.

My other (related) concern is that joining CERN is one thing, but in order to reap the scientific reward the government has to invest in the resources needed to exploit the access to facilities membership would provide. Without a related increase in research grant funding for basic science the opportunity to raise the level of scientific activity in Ireland would be lost.

Ireland recently joined the European Southern Observatory (ESO), a decision which gave Irish astronomers access to some amazing telescopes. However, there is no sign at all of Irish funding agencies responding to this opportunity by increasing funding for academic time, postdocs and graduate students needed to do the actual science.

Although astronomy is clearly much more interesting than particle physics (😉) in one respect the case of ESO is very like the case of CERN – the facilities do not themselves do the science. We need people to do that.

Who uses LinkedIn?

Posted in Science Politics, The Universe and Stuff with tags , , , , on September 5, 2019 by telescoper

We had a talk at INAM2019 yesterday about the Astronomical Science Group of Ireland which is about to be re-launched with a new website. One of the main reasons for doing this is that Ireland recently joined the European Southern Observatory and in order to capitalize on its involvement it is important to persuade the Irish government to invest in the resources needed (especially postdocs, etc) to do as much science as possible using ESO facilities. At the moment there isn’t a very well organized lobby for astronomy in Ireland.

One of the suggestions made yesterday was that astronomers in Ireland should join LinkedIn in order to raise their profile individually and collectively.

I am not, and have never been, on LinkedIn and this is the first time I’ve ever even thought of joining it (though I do from time to time receive emails from people I don’t know asking me to). I’ve always thought it was for more businessy types. I don’t know of any astronomers (or scientists generally) who use it either, but that may be just because I’m not on it and wouldn’t know either way.

I just thought therefore, that I might invite any readers of this blog – whether astronomers or not – if they use LinkedIn to please comment on its usefulness or otherwise using the box below. Please also comment on whether you think it would help astronomers in Ireland organize in the manner envisaged.

Banging the drum for ESO

Posted in Maynooth, The Universe and Stuff with tags , , , on February 6, 2019 by telescoper

It was a pleasure to welcome Rob Ivison, Director of Science at the European Southern Observatory (ESO) , to Maynooth this afternoon for a colloquium.

I was on my best behaviour introducing his talk and even refrained from pointing out that his native Lancashire is actually in the Midlands.

Ireland became a full member of ESO earlier this year and Rob has been touring Ireland giving talks to encourage Irish astronomers to make the most of the many opportunities membership presents. Having already visited Cork and Galway he passed through Maynooth today before ending up in Dublin tomorrow.

It was an enjoyable and impressive talk and very nice to chat with Rob afterwards over dinner.

Bon voyage to Rob and thanks for the visit!

Newsflash: Ireland and ESO

Posted in Science Politics, The Universe and Stuff with tags , , on September 26, 2018 by telescoper

Some good news was waiting for me when I got back to the office after my lecture just now, namely that Astronomy in Ireland will shortly receive an enormous boost, as the Republic has joined the European Southern Observatory (ESO).

For those of you not in the know, ESO is an intergovernmental astronomy organisation and is the world’s most productive astronomical observatory. Founded in 1962, its headquarters are in Garching (near Munich, Germany), and it currently has 15 member states. On October 1st, Ireland will become the 16th. Its main work is conducted using a variety of large optical and radio telescopes which are all located in the southern hemisphere, notably at Paranal in Chile.

ESO’s VLT telescopes at Paranal (in the Andes Mountains).

The official press release includes the following:

We are delighted to welcome Ireland as the newest member of our organisation” stated ESO’s Director General, Xavier Barcons. “Ireland’s mature and thriving astronomical community will add to the broad variety of expertise in the ESO Member States, strengthening ESO’s position at the forefront of global astronomy. Irish astronomers will gain access to a suite of the world’s most advanced ground-based astronomical telescopes and will have the opportunity to be part of the construction of the next generation of ESO instruments in partnership with other ESO Member States. We are also very much looking forward to working with Irish industrial partners to build and operate ESO’s state-of-the-art telescopes.

It was probably the industrial opportunities afforded by ESO membership that persuaded the Irish government to stump up the subscription fee, but this decision is also extremely positive news for the relatively small but vibrant community in Ireland working on observational astronomy which I’m sure will make the most of the chance to do ever more exciting research using these facilities.

Gravitational Redshift around the Black Hole at the Centre of the Milky Way

Posted in The Universe and Stuff with tags , , , , , , on July 26, 2018 by telescoper

I’ve just been catching up on the arXiv, and found this very exciting paper by the GRAVITY collaboration (see herefor background on the relevant instrumentation). The abstract of the new paper reads:

The highly elliptical, 16-year-period orbit of the star S2 around the massive black hole candidate Sgr A* is a sensitive probe of the gravitational field in the Galactic centre. Near pericentre at 120 AU, ~1400 Schwarzschild radii, the star has an orbital speed of ~7650 km/s, such that the first-order effects of Special and General Relativity have now become detectable with current capabilities. Over the past 26 years, we have monitored the radial velocity and motion on the sky of S2, mainly with the SINFONI and NACO adaptive optics instruments on the ESO Very Large Telescope, and since 2016 and leading up to the pericentre approach in May 2018, with the four-telescope interferometric beam-combiner instrument GRAVITY. From data up to and including pericentre, we robustly detect the combined gravitational redshift and relativistic transverse Doppler effect for S2 of z ~ 200 km/s / c with different statistical analysis methods. When parameterising the post-Newtonian contribution from these effects by a factor f, with f = 0 and f = 1 corresponding to the Newtonian and general relativistic limits, respectively, we find from posterior fitting with different weighting schemes f = 0.90 +/- 0.09 (stat) +\- 0.15 (sys). The S2 data are inconsistent with pure Newtonian dynamics.

Note the sentence beginning `Over the past 26 years…’!. Anyway, this remarkable study seems to have demonstrated that, although the star S2 has a perihelion over a thousand times the Schwarzschild radius of the central black hole, the extremely accurate measurements demonstrate departures from Newtonian gravity.

The European Southern Observatory has called a press conference at 14.00 CEST (13.00 in Ireland and UK) today to discuss this result.

Absorbed in a Quasar Spectrum

Posted in The Universe and Stuff with tags , , , , , , on December 5, 2016 by telescoper

Many people seem to think that astronomers spend all their time looking at pretty pictures of stars and galaxies. Actually a large part of observational astronomy isn’t about making images of things but doing spectroscopy. In fact the rise of astronomical spectroscopy is what turned astronomy into astrophysics. But that’s not to say that spectra can’t be pretty either. Here is an example (from here) which shows the light from the quasar HE0940-1050 taken by the UVES instrument mounted on ESO’s Very Large Telescope in Chile.

This quasar is an interesting object, at a redshift of z= 3.0932 (which converts to a look-back time of about 11.6 billion years). The dark bands and lines you can see in the spectrum are caused by absorption of the light from the quasar by clouds of hydrogen gas between the quasar and the observer; the strength of the absorption indicates how much gas the light from the quasar has travelled through.  The absorption occurs at a particular wavelength corresponding to the Lyman-α transition but, because the clouds are all at different redshifts, each produces a line at a different observed wavelength in the quasar spectrum. There are many lines, which is why the collection of clouds responsible for them is often called the Lyman-α Forest. In effect the quasar sample is very much like a core sample, as if we were able to drill back in time to the quasar through the material that lies along the line of sight.

This spectrum is particularly remarkable because of the number of faint lines that can be seen: it’s like a detailed DNA Fingerprint of cosmic structure. It’s also very pretty.

 

Dark Matter: Dearth Evaded

Posted in Astrohype, The Universe and Stuff with tags , , , , , , on May 23, 2012 by telescoper

While I’m catching up on developments over the last week or so I thought I’d post an update on a story I blogged about a few weeks ago. This concerns the the topic of dark matter in the Solar Neighbourhood and in particular a paper on the arXiv by Moni Bidin et al. with the following abstract:

We measured the surface mass density of the Galactic disk at the solar position, up to 4 kpc from the plane, by means of the kinematics of ~400 thick disk stars. The results match the expectations for the visible mass only, and no dark matter is detected in the volume under analysis. The current models of dark matter halo are excluded with a significance higher than 5sigma, unless a highly prolate halo is assumed, very atypical in cold dark matter simulations. The resulting lack of dark matter at the solar position challenges the current models.

In my earlier post I remarked that this  study   makes a number of questionable assumptions about the shape of the Milky Way halo – they take it to be smooth and spherical – and the distribution of velocities within it is taken to have a very simple form.

Well, only last week a rebuttal paper by Bovy & Tremaine appeared on the arXiv. Here is its abstract:

An analysis of the kinematics of 412 stars at 1-4 kpc from the Galactic mid-plane by Moni Bidin et al. (2012) has claimed to derive a local density of dark matter that is an order of magnitude below standard expectations. We show that this result is incorrect and that it arises from the invalid assumption that the mean azimuthal velocity of the stellar tracers is independent of Galactocentric radius at all heights; the correct assumption—that is, the one supported by data—is that the circular speed is independent of radius in the mid-plane. We demonstrate that the assumption of constant mean azimuthal velocity is physically implausible by showing that it requires the circular velocity to drop more steeply than allowed by any plausible mass model, with or without dark matter, at large heights above the mid-plane. Using the correct approximation that the circular velocity curve is flat in the mid-plane, we find that the data imply a local dark-matter density of 0.008 +/- 0.002 Msun/pc^3= 0.3 +/- 0.1 Gev/cm^3, fully consistent with standard estimates of this quantity. This is the most robust direct measurement of the local dark-matter density to date.

So it seems reports of the dearth were greatly exaggerated..

Having read the paper I think this is a pretty solid refutation, and if you don’t want to take my word for it I’ll also add that Scott Tremaine is one of the undisputed world experts in the field of Galactic Dynamics. It will be interesting to see how Moni Bidin et al. respond.

This little episode raises the question that, if there was a problem with the assumed velocity distribution in the original paper (as many of us suspected), why wasn’t this spotted by the referee?

Of course to a scientist there’s nothing unusual about scientific results being subjected to independent scrutiny and analysis. That’s how science advances. There is a danger in all this, however, with regard to the public perception of science. The original claim – which will probably turn out to be wrong – was accompanied by a fanfare of publicity. The later analysis arrives at a much less spectacular conclusion,  so will probably attract much less attention. In the long run, though, it probably isn’t important if this is regarded as a disappointingly boring outcome. I hope what really matters for scientific progress is people doing things properly. Even if it  don’t make the headlines, good science will win out in the end. Maybe.

On the Dearth of Dark Matter in the Solar Neighbourhood

Posted in Astrohype, The Universe and Stuff with tags , , , , , , , , on April 22, 2012 by telescoper

I’m a bit late getting onto the topic of dark matter in the Solar Neighbourhood, but it has been generating quite a lot of news, blogposts and other discussion recently so I thought I’d have a bash this morning. The result in question is a paper on the arXiv by Moni Bidin et al. which has the following abstract:

We measured the surface mass density of the Galactic disk at the solar position, up to 4 kpc from the plane, by means of the kinematics of ~400 thick disk stars. The results match the expectations for the visible mass only, and no dark matter is detected in the volume under analysis. The current models of dark matter halo are excluded with a significance higher than 5sigma, unless a highly prolate halo is assumed, very atypical in cold dark matter simulations. The resulting lack of dark matter at the solar position challenges the current models.

As far as I’m aware, Oort (1932, 1960) was the first to perform an analysis of the vertical equilibrium of the stellar distribution in the solar neighbourhood. He argued that there is more mass in the galactic disk than can be accounted for by star counts. A reanalysis of this problem by Bahcall (1984) argued for the presence of a dark “disk” of a scale height of about 700 pc. This was called into question by Bienaymé et al. (1987), and by Kuijken & Gilmore in 1989. In a later analysis based on a sample of stars with HIPPARCOS distances and Coravel radial velocities, within 125 pc of the Sun. Crézé et al. (1998) found that there is no evidence for dark matter in the disk of the Milky Way, claiming that all the matter is accounted for by adding up the contributions of gas, young stars and old stars.

The lack of evidence for dark matter in the Solar Neighbourhood is not therefore a particularly new finding; there’s never been any strong evidence that it is present in significant quantities out in the suburbs of the Milky Way where we reside. Indeed, I remember a big bust-up about this at a Royal Society meeting I attended in 1985 as a fledgling graduate student. Interesting that it’s still so controversial 27 years later.

Of course the result doesn’t mean that the dark matter isn’t there. It just means that its effect is too small compared to that of the luminous matter, i.e. stars, for it to be detected. We know that the luminous matter has to be concentrated more centrally than the dark matter, so it’s possible that the dark component is there, but does not have a significant effect on stellar motions near the Sun.

The latest, and probably most accurate, study has again found no evidence for dark matter in the vicinity of the Sun. If true, this may mean that attempts to detect dark matter particles using experiments on Earth are unlikely to be successful.

The team in question used the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory, along with other telescopes, to map the positions and motions of more than 400 stars with distances up to 13000 light-years from the Sun. From these new data they have estimated the mass of material in a volume four times larger than ever considered before but found that everything is well explained by the gravitational effects of stars, dust and gas with no need for a dark matter component.

The reason for postulating the existence of large quantities of dark matter in spiral galaxies like the Milky Way is the motion of material in the outer parts, far from the Solar Neighbourhood (which is a mere 30,000 light years from Galactic Centre). These measurements are clearly inconsistent with the distribution of visible matter if our understanding of gravity is correct. So either there’s some invisible matter that gravitates or we need to reconsider our theories of gravitation. The dark matter explanation also fits with circumstantial evidence from other contexts (e.g. galaxy clusters), so is favoured by most astronomers. In the standard theory the Milky Way is surrounded by am extended halo of dark matter which is much less concentrated than the luminous material by virtue of it not being able to dissipate energy because it consists of particles that only interact weakly and can’t radiate. Luminous matter therefore outweighs dark matter in the cores of galaxies, but the situation is reversed in the outskirts. In between there should be some contribution from dark matter, but since it could be relatively modest it is difficult to estimate.

The study by Moni Bidin et al. makes a number of questionable assumptions about the shape of the Milky Way halo – they take it to be smooth and spherical – and the distribution of velocities within it is taken to have a very simple form. These may well turn out to be untrue. In any case the measurements they needed are extremely difficult to make, so they’ll need to be checked by other teams. It’s quite possible that this controversy won’t be actually resolved until the European Space Agency’s forthcoming GAIA mission.

So my take on this is that it’s a very interesting challenge to the orthodox theory, but the dark matter interpretation is far from dead because it’s not obvious to me that these observations would have uncovered it even if it is there. Moreover, there are alternative analyses (e.g. this one) which find a significant amount of dark matter using an alternative modelling method which seems to be more robust. (I’m grateful to Andrew Pontzen for pointing that out to me.)

Anyway, this all just goes to show that absence of evidence is not necessarily evidence of absence…

VISTA on Video

Posted in The Universe and Stuff with tags , , , , , on March 23, 2012 by telescoper

A chance tweet brought to my attention this video that fits well with a news story that’s been doing the rounds for a few days.   This concerns a very deep and wide survey called UltraVISTA, that has been made using the VISTA telescope at the European Southern Observatory’s Paranal Observatory in Chile. You can find the full press release from ESO that started the media interest here, where some lovely images can also be found.

VISTA is the world’s largest infra-red survey telescope, and is unusual among telescopes for having only one instrument on it, an Infra-red camera.  Technically, therefore,  it should really be called ISTA; owing to cost constraints the Visible camera that was initially proposed to accompany the Infra-red one and supply the V in its acronym,  was never built. Anyway, VISTA was designed explicitly to do survey work involving very distant and faint objects; its forte is to allow very deep images to be made with a very wide field of view, as demonstrated on the video…

Since I’m using the handle “telescoper” on this blog, I suppose I really should post about telescopes a bit more often than I do but I hope this will do for now!