Cosmic Horizons

Where did that month go? Winter is almost over and spring will be breaking, and my backlog of papers to comment on is getting longer and longer. So a quick post this morning on a recent cool paper by PhD student, Brendan McMonigal , called "Sailing under the Magellanic Clouds: A DECAm View of the Carina Dwarf". The title tells a lot of the story, but it all starts with a telescope with a big camera. The camera is DECam , the Dark Energy Camera located on the 4m CTIO telescope in Chile. This is what it looks like; It's not one CCD , but loads of them butted together allowing us to image a large chunk of sky. Over the next few years, this amazing camera will allow the Dark Energy Survey  which will hopefully reveal what is going on in the dark sector of the Universe , a place where Australia will play a key-role through OzDES . But one of the cool things is that we can use this superb facility to look at other things, and this is precisely what Bendan did...

Reviewing grants and postdoctoral researchers have completely absorbed the last week, and will similarly consume the week to come, so a quick post today, just posting a news article from our  School of Physics  webpage. Sydney University astronomers granted observing time on the Hubble Space Telescope By Tom Gordon 17 June 2013 Two astronomers, Professors Geraint Lewis and Joss Bland-Hawthorn, from the Sydney Institute for Astronomy, located in the School of Physics, have been awarded observing time on one of the world's premier observing facilities, the Hubble Space Telescope. Obtaining observations with this unparalleled telescope is extremely competitive, and this award has demonstrated that their research is world-leading. As part of an international team, Professor Lewis has secured 28 Primary Spacecraft Orbits and 28 parallel spacecraft orbits in Cycle 21 of the Hubble Space Telescope (HST) program due to begin in October this year. In addition, Professor Blan...

Another week gone, and no time for too much deep thinking (although progress is being made, so hopefully will have some interesting things to report). Luckily, the smart students out there are squirreling away, and so today I can present the latest in the study of the galactic bulge by ANU student Melissa Ness . I've written before about this really cool study, using the AAOmega Spectrograph  on the might Anglo-Australian Telescope  to measure the speeds and chemical make-up of stars in the Galactic Bulge , the centre of our Milky Way galaxy. This is hard work, as there are a lot of stars spread over a large amount of sky, and so to get lots of spectra, you need to use the multi-fibres and large field of view of AAOmega. This has been a mammoth task over the last few years, with us taking 28,000 spectra, and in this study almost 17,5000 stellar velocities were used. But what is it we want to know? Well, the present day shape, velocities and chemistry of the Milky Way is...

A weekend at home with the kids, with yesterday being wiped out by huge downpours from sunrise to sunset. Unfortunately, work has been full on, with a thousand different things going on, so no time to muck around. But we have another paper accepted, so here's a little summary. This week's paper is by PhD student,  Jovan Veljanoski , working at Edinburgh's  Institute for Astronomy . This is another paper based upon our extensive Pan-Andromeda Archaeological Survey (PAndAS) of Andromeda. As I've noted before, this survey reveals a mass of substructure in the outskirts of Andromeda, as well as a growing population of  dwarf galaxies.  It also reveals lots of  globular clusters , balls of a million or so stars orbiting Andromeda. The key thing in this study is the velocities of the globular clusters. Why? Well, their velocity depends upon the mass they are orbiting, so if you get lot of velocities, then you can measure the mass. But, of course, it is never as si...

I've finally succumbed to the sickness sweeping the land, and find myself wide awake at 5am (this is not really a natural state for an astronomer). So, as I sit here with sore throat, a quick post for you. Blair Conn, my ex-student and now Humboldt Fellow in Heidelberg, and I, have had a paper accepted for publication in the  Astrophysical Journal. The focus of the paper is the  Monoceros Ring , a vast "stream" of stars that appears to circle at the outer edge of the Milky Way galaxy. The ring has had a bit of a checkered past, not its existence, but its origin. People generally fall into two camps, those that think that Monoceros is just a natural piece of galaxy, a region of the stellar disk that has been puffed up (also known as the flare or warp of the disk), whereas others think the ring is the debris from a dwarf galaxy which was tidally disrupted when it came to close to the disk of the Milky Way. Potentially it is the debris from the Canis Major Dwarf Ga...

What's the goal of astronomy and astrophysics? Pretty Hubble pictures? Whacky statements about multi-verses and black hole entropy? Nope, not really. The goal is to understand the Universe in terms of the laws of physics. Like "real" science, there is a strong link between theory and observation and experimentation, each feeding off each other, and as I noted a little while ago, the development of new instrumentation on telescopes often opens a new window on the Universe. Instruments like SAMI will let us do something new, namely measure the spins and chemistry of a large number of objects. But now the key question - If you were going to measure the spins of a whole load of galaxies, what would you expect to see? Would they be randomly orientated? Would patches of galaxies spin together in unison? Would nearby galaxies spin in opposite directions? And how would you even begin to answer this question? There are paper-and-pen approaches to answering this question, b...

For a long time, I have been a fan of David Bowie , and have seen him in concert a couple of times. In the good old days (early 1980s), when MTV showed nothing but music videos, I would happily while away the hours on Bowie (and Queen, and just about everything else). But as everyone knows, people grow-up and have to go to university, and MTV went the way of pathetic shows rather than showing videos, and so I didn't really watch music videos any more. While holidaying last week, we happened to be chilling, and decided to watch a bit of Rage as they were showing a series of Bowie videos, and while watching Let's Dance , I had a "ehh - that's familiar" kind of moment. It was driven by this image a sight what will be familiar to astronomers the world over. No, not the people in the foreground, or the nuclear explosion in the background, but the mountains! Why? Because they are the mighty Warrumbungles , mountains in Northern(ish) New South Wales, near the ...

When I say modern astronomy, what do you think of? Large telescopes peering into the sky, looking to unlock the secrets of the Universe? Of course, telescopes drive astronomical research, but what is often forgotten is the business end of the telescope, the instruments that collect the light, are the things that really define the science we can do. And such instruments can be extremely complex, and extremely expensive. Here at Sydney we have a group working on astronomical instrumentation and a new instrument, The Sydney-AAO Multi-object Integral field spectrograph (SAMI) , has recently be commissioned and the first paper has been accepted. So, what does this new instrument do? Well, spectroscopy is an essential part of astronomy. Basically, it just means collecting light and dispersing it into a rainbow. Over to Pink Floyd We don't use prisms any more (we use volume phase holographic gratings, which sounds much more science fiction). Looking at the light tells us lots and l...

The Sagittarius Dwarf galaxy is a pretty cool object. It was discovered by a very close collaborator of mine, Rodrigo Ibata of the Strasbourg Observatory, way back in the ancient past (well, 1993), and it is clearly a little galaxy in trouble. It's orbit brings it dangerously close to the Milky Way, where its tidal gravitational pull is ripping it apart. During its destruction, stars have been continuously pulled from the dwarf and are now wrapped around the Milky Way. These tidal streams are really interesting, and can be used to work out how the dwarf has been pulled apart. More importantly, if we can work out the orbit of the streams, then we can measure the amount of dark matter surrounding the Milky Way, a very important thing to do. But look at this This is a map of the sky in coordinates where the tidal stream of Sagittarius wraps around the equator.  You can clearly see the Milky Way galaxy. The colour are fields from the Sloan Digital Sky Survey where stars in the ...

I'm still at Kitt Peak, on the 5th night of a 6 night run at the Mayall 4-m Telescope. Observing sometimes make me think of life in a nuclear shelter, post-apocalypse. No windows, no daylight, being very tired and drinking lots of coffee, which is not good given the nearest toilet is two floors down, down a very nuclear-shelter-like steel stairway. When the mighty dome moves, it's like another nuclear strike. In the control room, it's a little dark, with music thumping, and science being done. Bed at about 6am with sleep to the early afternoon, followed by an hour or two of absorbing Sun-shine. Today we had a trundle around Kitt Peak to see the other telescopes. Here's a couple of snap-shots: After a little instrument failure, we're back on the sky, but one thing I think people don't know is that we typically finish the night when it is still dark outside. Why? Well, even when the Sun is well below the horizon, it still lights up the sky and, whil...

After a rushed week, it was time to hop on a plane and head for the US. After passing through LA Airport (not my favorite, especially given the time taken to fingerprint me and the several hundred people who arrived with me, but the passport checking guy was friendly and chatted about astronomy - holding up the hundreds behind me :), I got into Tucson yesterday where it was 37C. Today was the drive up to Kitt Peak, through very stark desert, with amazing cacti and people seemingly living in the middle of nowhere. Definitely cooler, the view from almost 7000 ft over the desert is very cool. Here's the view from the bottom of the 4m Mayall Telescope , overlooking the rest of Kitt Peak. The clouds, of course, aren't exactly a good sign, and we've lost a little time this evening to them, but things look like they will be running a soon. I will write a little more about the science later in the week. Before going back to the clearing skies, a couple of interesting things...

A great week for the Conns! My ex-students, Blair Conn (who is no relation to Anthony), Richard Lane and I have just had a new paper accepted on the discovery of a Collisional Ring Galaxy at redshift z=0.111 (the most distant one known - correction, one of the most distant known). The galaxy was found serendipitously in a Subaru survey of the galactic disk and looks quite interesting. Here's two images of the system, in g-band (left) and r-band (right). Cool eh! But it looks a bit better when you combine these to make a colour picture (we can make a pretend in-between band by averaging the two pictures above). This is what you get (and is annotated as in the paper). The Slits in the image correspond to where we pointed the GMOS spectrograph on the Gemini-North telescope, allowing us to measure the velocities of the various components. It also revealed that there are active galaxies hidden down in the middle. So, what's going on here? Well, we have some local examples...

I've been observing at the AAT a couple of time over the last few months. It's a long drive from Sydney (almost 6 hours), for long winter nights in the dome. We were using the rather wonderful AAOmega spectrograph to chase stars in the Sagittarius Dwarf and its associated tidal stream (I'll write more about these later). I'm not much of an Astronomer, in the sense that I am pretty clueless about constellations and the names of stars (but having Google Sky on my phone is really starting to help). But when I am observing, I take the chance to really look up. My first observing run (in 1991) was at the William Herschel Telescope in the Canary Island, and it was the first time that I **really** saw stars, and saw that they had colours. I have a valid excuse, having grown up in the not-so-clear skies of South Wales, followed by a few years in London. However, there are more than things to look at other than stars. I really like catching Iridium Flares , a family of co...