Archive for the ‘PACS’ Category

Deepest and Largest

May 4, 2010

This afternoon has been hopping from nearby to more distant galaxies. I’m more interested in the latter, so payed close attention to the talk on H-ATLAS, a project I’m working on which is the largest single survey being conducted with Herschel in terms of area. We’re also getting a talk now on the PEP survey which is producing the deepest images obtained with the PACS instrument, probing the origins of the cosmic infrared background.

Astoundingly deep and high quality images – hopefully some of these will be released on Thursday – compared to what has gone before.


Herschel Observations of Trans-Neptunian Objects: New Light on the edge of the Solar System

January 16, 2010

Over the next several weeks we’re going to be saying a bit more about the various Herschel first science results that were discussed at the meeting in Madrid just before Christmas. These are very early results that have not been fully digested or understood, but they give a taste of what is to come once these various projects collect many times more data on their targets and the scientists working on them have had more time to understand the results.

The first set of new results we’re going to discuss are observations of Trans-Neptunian Objects – dwarf planets at the edges of our own solar system like Pluto, Makemake and Eris. My field is extragalactic astronomy and cosmology, so my professional work doesn’t usually involve such things, but I do find them interesting on several levels. Firstly, they’re the most distant objects in our solar system and the least affected by the Sun, so they’re the closest thing we have to the very earliest objects to form around the Sun. Secondly, they’re so distant that they could be thought of as being on the edge of interstellar space – they are, in a sense, the boarder guards of the solar system. Finally, and this isn’t really a scientific point, I’m working on some science fiction set in trans-Neptunian space and beyond so any new results have a bearing on what I’m going to write.

What has Herschel seen of TNOs? So far a handful have been observed with the SPIRE and PACS instruments. The aim is to better understand their basic properties – size, mass, albedo – by measuring the amount of far-IR light that they emit. Since they’re small, maybe 1000km in diameter, distant and cold, they are very faint and require a large telescope like Herschel for them to be detectable. The second picture shows what PACS saw when it observed Pluto. This is a ‘differencing’ observation, where the target is observed in one position on the detector, then moved to another and the two are subtracted. This process is repeated several times so you see a positive image at the centre and other positive and negative images at the reference positions.

PACS observed six TNOs, including Pluto. Two were fainter than predicted based on what we thought we knew about them, one was significantly brighter and three were about right. Meanwhile two TNOs were observed by SPIRE and here too things weren’t quite what was expected.

What does all this mean? We don’t know just yet, but since the results aren’t quite what was predicted we’re clearly learning something new about these objects. They might be more reflective – have higher albedo – than we thought, their surfaces might be more rocky, or their sizes might not be what is expected.

As with all the data we’ve seen from Herschel so far, there’s a lot more work to be done before we understand what the telescope is telling us. But it’s clear that Herschel is going to bring new light to our own solar system along with the rest of the observable universe!

First Herschel Science!

December 16, 2009

Lots of new Herschel science will be released over the next few days by ESA. The first new result is an image of a region in Acquilla (not the Eagle Nebula as I originally stated – apologies!) taken with the PACS and SPIRE instruments.

The Eagle Nebula image reveals the dust and young stars obscured from observation by telescopes, such as HST, working at shorter wavelengths. Much structure is seen in this image, revealing the complex turbulent interactions behind star and planet formation.

More images and science results are coming. There should be several more releases over the next few days, coinciding with the early Herschel science meeting currently underway in Madrid (I’m not there so can’t report live). ESA have set up a central resource for all new Herschel images – the OSHI – online showcase of Herschel images. There’s not much there at the moment, but it’ll soon be filling up!

First look at Herschel Spectroscopy

November 27, 2009

ESA put out a major release today showing the first results from the spectrographs on Herschel. The release includes data on the Orion star formation region, on nearby and distant galaxies, on a massive star about to become a supernova and on a comet in our own solar system. The latter set of data was taken with HIFI before the technical fault that has left it shut down, awaiting a restart early next year.

These spectroscopic observations show the huge potential of Herschel to show us the physical and chemical processes going on inside dusty objects, be they star formation regions in our own galaxy, or in luminous interacting galaxies like Arp220 and Mrk231. My own research interests are more focussed on the distant luminous objects, and the data shown here from two archetypical ULIRGs (Ultraluminous Infrared Galaxies) are really spectacular. Never before have we seen the rich range of spectral lines that PACS and SPIRE have revealed in these objects.

PACS also holds out the hope of examining the velocity structure of some of these lines. This is particularly interesting in Mrk231 which hosts not only a massive burst of star formation but also a supermassive black hole powering a hugely luminous active galactic nucleus (AGN). The relationship between galaxy interactions and mergers in triggering both starbursts and AGNs is a hot topic, and Mrk231 makes an ideal testbed.

Finally, for sheer spectral richness and complexity, the PACS spectrum of the massive star VYCMa takes some beating. There’s a huge amount of physics and chemistry in this spectrum of a star deep into its old age and soon to become a supernova. Unfortunately this isn’t my area, so hopefully someone will add comments describing what the data means for this object.

For more information and coverage of these results see the ESA web release, BBC News Online, and the SPIRE website at Cardiff University.

Stunning new Herschel Images of the Milky Way

October 2, 2009

ESA released new images form the Herschle telescope today. This shows a two degree square region of our galaxy at wavelengths and resolutions that have never before been achieved.

5 Colour Herschel Image of part of our own galaxy

The images show intricate filamentary structures made from cold interstellar material. This matter feeds galactic star formation, and this image provides new insights into these highly turbulent processes. This is also the first image released from Herschel’s ‘parallel mode’ that allows it’s two imaging instruments, PACS and SPIRE, to work together. This observing mode is immensely powerful as it allows 5 colour images such as this to be produced which might otherwise have had to be pieced together from separate observations. It’s a critically important mode for many of Herschel’s large area surveys, including the HIGAL project which will observe the entire galactic plane with sensitivity and resolution matching the 2 degree by 2 degree image shown here.

Further information about Herschel can be found from ESA, the SPIRE instrument team, the UK’s STFC and the BBC.

Another first light image

July 12, 2009

One of the first light images that didn’t get posted on Friday is attached below. It’s from PACS and shows a rather different imaging mode that PACS is capable of: spectral imaging.

Spectral image of the Catseye Nebula in the far-IR line NIII taken by PACS

Spectral image of the Catseye Nebula in the far-IR line NIII taken by PACS

This is an image of the Catseye Nebula in the far-infrared emission line NIII – or, for those who aren’t astronomers, Nitrogen 2+ – which lies at a wavelength of 57 microns, and is thus completely inaccessible from the ground.

This image is taken with PACS’s line imaging mode. This uses a different part of the instrument which is set up to be able to take spectra in a 5×5 grid. The result is not a 2D image but a 3D data cube where there is a spectrum for each of the 25 pixels – you can see these plotted out in the image. This approach is very powerful for looking at the spatial distribution of emission lines. The Catseye Nebula is a so-called planetary nebula. This class of objects represent a late stage in stellar evolution, where a star expels the outer layers of its atmosphere and have nothing to do with planets. The PACS image clearly shows that the NIII line emission has a hole in the middle, and is thus coming form the shell of material ejected by the star. This is just what is expected, so there’s no new science here, but it’s an ideal test of the capabilities of this aspect of PACS that has not been demonstrated before.

SPIRE first light images arrive!

July 10, 2009

The news is out, on the BBC and elsewhere, with the full coverage from ESA – first light results from all three of Herschel’s instruments, including the one I work on – SPIRE.

Image of the galaxy M66 taken with SPIRE at a wavelength of 250 microns compared to Spitzer image at 160 microns.

Image of the galaxy M66 taken with SPIRE at a wavelength of 250 microns compared to Spitzer image at 160 microns.

The images are superb! You can see far more structure in these images than in the best previously available even though SPIRE’s are at longer wavelengths. You can see structure in the dust distribution in these galaxies and, by comparing the three different colours SPIRE observes in, you can get some idea of the temperature distribution of the dust.

SPIRE image of M74

Also, the faint background blobs in these images are real, as they’re present at all three SPIRE wavelengths. These are background dusty galaxies which we expect SPIRE will be able to detect in great numbers. This promise is now fulfilled marvelously in the first images we’ve taken. These are the galaxies responsible for the Cosmic Infrared Background which encompasses half the energy generated in the universe since the Big Bang. It’s made up of light emitted by stars, and accreting supermassive back holes, which has been absorbed by dust and reradiated at these long far-IR wavelengths. It is the hidden history of the universe, something we have had little access to before now, but which SPIRE will now help us to understand in detail.

M74 images in all 3 SPIRE bands

M74 images in all 3 SPIRE bands

HIFI, the high resolution spectrometer, also has released its first spectra, showing strong emission lines from gas involved in star formation in the DR21 molecular cloud.

Herschel was only launched about 7 weeks ago, and these observations are just a first quick look at what the instruments can do. There is a lot more tuning, calibration and refinement to be done before we can do real quantitative science with these instruments. For that reason to get decent data on anything at this stage is quite amazing. To get data of the quality seen in the SPIRE images, the PACS images you can find below and in the HIFI spectra is absolutely astounding.

Herschel really is going to bring a new era to far-IR astronomy!

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More news releases next week

July 3, 2009

Watch out for some more press releases from Herschel next Friday!

First Light Images!

June 19, 2009

The PACS instrument on Herschel has taken the observatory’s first images, of the galaxy M51, and they’ve just been released.

Here’s a three colour image at the PACS wavelengths (70, 100 and 160 microns):

PACS images of M51 in the far-IR

PACS images of M51 in the far-IR

You can find more imaformation and more images at the ESA Website.

The telescope and instrument have yet to be fully tuned, but these images are already spectacularly good. Herschel is going to be doing great science!

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I have seen the future…

June 17, 2009

Just got a glimpse of the PACS first light image, and it’s most impressive!

I could tell you more, but then I’d have to kill you, but it should go down very well on Friday at the Paris Air Show.