Posts Tagged ‘spire’

Dusty Galaxies & Gravitational Telescopes

November 9, 2010

It was an exciting time at the end of last week when the H-ATLAS consortium’s first paper to the journal Science came out. As a co-author I’ve been aware of this result for some time, but it was interesting to see how it got taken up by the press etc..

What we’ve found is that some bright sources seen by Herschel that appear to be associated with fairly nearby galaxies, in cosmological terms at least, are in fact dusty objects behind those nearby galaxies, having their far-IR light amplified through gravitational lensing. The process is illustrated in this figure form one of our press releases.

Herschel finds gravitationally lensed dusty galaxies

Herschel finds gravitationally lensed dusty galaxies

This result started off a long time ago, when the author of the paper, Dr Mattia Negrello, produced models in his PhD thesis of the sources we might expect to find in the Herschel surveys and came to the conclusion that many of the brightest objects would be the result of gravitational lensing. This result was included in the proposal for the H-ATLAS large area survey but I suspect that a fair number of us thought that this aspect of the proposal was a long shot – hugely important if it worked, but not that likely to be the case.

When the first H-ATLAS data came in and we started looking at the brightest reddest sources, though, it looked as if Mattia might have been onto something after all. But we couldn’t be sure. What followed was a rapid dash around many telescopes to get the multiwavelength data needed to confirm the nature of these objects. We needed optical and near-IR imaging, some of which came from Keck, we needed high resolution submm interferometry, which came form the SMA, and we needed submm spectroscopy, which came from the CSO and PdB interferometers. More data is coming from Spitzer and elsewhere, and this will appear in future papers. This is truly multiwavelength astronomy at its best, bringing a wide variety of tools and techniques together to produce the final answer.

And that answer is that Mattia was right, and there are lots of lenses to be found in the Herschel surveys. More than that, the lenses are easy to find. Previous searches for lenses in the optical and radio have had hit rates – ie. the number of lenses found to number of candidates looked at – as low as 1 in 1000. With Herschel, we seem to have a hit rate of 100%.

This has several implications. Firstly we can use the lenses as gravitational telescopes, allowing us to look at very distant objects that are much fainter than would otherwise be possible. Secondly, since mass is responsible for the lensing effect, we can use these systems to look at dark matter and how it evolves.

It’s early days yet, and the initial crop of lenses from H-ATLAS are just 5 in number, but this was based on less than 3% of the final H-ATLAS survey, and there are other Herschel surveys, like HerMES, that are adding to the database. Larger surveys with these lenses central to the science case are also planned, though we have yet to be awarded the time.

This result is also a great example of how science works. Mattia came up with this prediction as a student and has tested it in his postdoctoral work. It’s not often that the predictions and tests are done by the same person, but this is generally how things are meant to go.

The media, needless to say, has been quite interested. The story has been picked up from India to Italy. It’s also appeared on David Ike’s forums though quite where this result fits in with UFOs and alien conspiracy theories I don’t know. Perhaps most significant is that the BBC Today programme’s science correspondent was moved to write about it on his blog even though BBC journalists were on strike that day.

All in all, a great achievement for Mattia, for H-ATLAS and for Herschel!


Herschel instruments ready for PV!

July 8, 2009

Since launch Herschel and its instruments have been going through a testing phase known as Commissioning. Essentially this means making sure everything still works after launch and making sure the whole system works as a whole. The next phase, called Performance Verification consists of much more detailed testing and calibration of the instruments to get them working at optimal performance and to establish all the calibration data needed for full scientific use.

Yesterday there was a review of all three instruments to determine their readiness to move from Commissioning Phase to Performance Verification Phase.

All three are ready to go, which places us one important step closer to real science with Herschel! I’m sure you’ll join me in congratulating the instrument teams on completing this phase successfully!

SPIRE back on the air!

June 1, 2009

We’re not observing the sky yet, but SPIRE is back as the operating instrument on Herschel at the moment.

The cooler has been recycled some more times, most recently in an entirely automatic mode while Herschel was out of contact with the ground station, and it worked perfectly!

The detectors are now a little bit colder than before, at about 290mK, so SPIRE continues to be the coldest thing in space. The main sub-instrument being tested at the moment is the spectrometer side. This is a fourier transform spectrometer and is thus essentially an interferometer where we need to be able to acquire fringes as the mirrors are scanned. This is a critical step, and we now have our first fringes!

The other news from the current campaign is that we have tested the calibration system. All seems to be going well with this sub-system as well!

So, much progress since our last report.

You can keep up to date on this minute by minute on the SPIRE twitter.

Just before switch on…

May 22, 2009

Ready to go?

A picture of the SPIRE instrument team at the ESA Operations Centre in Darmstadt just before they turn SPIRE on for the first time.

Things went well, so a later photo would show a rather more relaxed team!

Instrument team Twitter

May 20, 2009

Those of you who are interested in following detailed reports of the SPIRE instrument switch on and testing can find them on our Twitter feed:

Some of it can be a bit technical, but it gives a very good view of the detailed process of commissioning a newly launched space instrument. If you’d like to understand some of the terminology you could always ask here and we’ll see if we can answer!

Full steam ahead to launch!

March 10, 2009

Hi all!

A quick introduction from me – my name is Brian O’Halloran, and I’m a member of the SPIRE ICC team based at Imperial College London and I’ll be contributing to the Herschel Blog from now on.

As you might expect. things are really beginning to ramp up for Herschel’s launch next month. At the end of of February, we on the SPIRE team received the following wonderful news from Kourou:

“After final functional testing at Kourou, SPIRE has been declared ready for launch. Our next tests will be done in flight.”

So now the fun and games really begin! Next stop (assuming no show stoppers) will be launch – targeted for April 16th.

The BBC has a rather nice article on Herschel and Planck at Kourou, and gives you some insight into the final testing, and the vehicle integration with the Ariane 5 booster.

Check out the audio interviews – in particular from Tanya Lim (RAL), on Herschel’s scientific goals.

As we speak, the various Herschel instrument teams are furiously working away to get everything on the operations side ready for launch – mission planning, observation planning for the performance verification and science demonstration phases post-launch, getting the Herschel data reduction software operational etc. – it’s now a 7-day week for a lot of people across ESA and beyond.

A key pre-launch event will come in late March, when data reduction workshops will be held in Madrid for team members from the successful Herschel Key Program proposal groups – time awarded early in the Herschel programme for large, fundamental observing programs. This is to get the respective groups up to speed with handling and reducing their data once they get it hand post-launch and commissioning phases. We want groups to be confident in dealing with Herschel data as soon as possible – and for papers to appear as quickly as possible, based on their datasets. It’s yet another sign that we’re now just about to move into the Herschel operational phase!


June 3, 2008

Welcome to the Herschel Space Observatory Blog.

Herschel is the European Space Agency’s far-infrared space telescope, due to be launched at the end of 2008.

This blog will give you some idea of what it’s like to work on a project like this, from day to day trivia to the excitement of launch and of getting new scientific results that tell us how the universe works.

The blog is open to various members of the Herschel team, and anyone can post a comment or ask us a question. At the moment it’s rather early days, and the blog has few posters and a rather basic style. That will change with time. Eventually we will have news of the latest science results covering everything from star and planet formation to galaxy formation in the high redshift universe.

So read, enjoy, and let us know what you think!