Puffing up elliptical galaxies October 3, 2009
Posted by sarah in: new astronomy, science . 3comments
Elliptical galaxies are the boring uncles of the galaxy family: they’re amorphous blobby things, ubiquitous in the Universe, that contain a fairly uniform population of old, red stars. Without the interstellar gas and dust that is needed to harbour pretty sites of star formation, they are supremely unphotogenic. But they have far more going on beneath their featureless surface: the complex dynamics inside many ellipticals show evidence of a turbulent past and, with many of the most massive known galaxies in our local Universe being ellipticals, they clearly play an important role in galaxies’ evolution.
Studies seem to suggest that high-redshift elliptical galaxies are more compact than their present-day counterparts (figure from Glazebrook, 2009)
Observational surveys of elliptical galaxies at high redshift have in recent years revealed a further interesting fact: ellipticals at high redshift appear to be much smaller in size than those in our local Universe, but have about the same mass and density of stars. In a recent ApJ paper, Ivana Damjanov of the University of Toronto and collaborators describe how a sample of elliptical galaxies at redshifts 1 to 2 looked 2-3 times smaller than those in the local Universe. The first surprise lies in that they evolve at all between redshift 2 and 0. In our current understanding of galaxy formation and evolution, ellipticals are the “red and dead” endpoints of evolution.
More dark chatter February 9, 2009
Posted by sarah in: science . 1 comment so farWhile Mars and exoplanets stole most of the science headlines in 2008, papers reporting results from a number of cosmic ray detectors gathered a lot of attention in the (astro-)physics community. Excesses in the number of particles detected at high energies (~50 GeV) that could not be explained by theoretical predictions sparked speculations that cosmic ray satellite PAMELA may be picking up the signature of dark matter in the Galaxy. A commonly accepted scenario for the nature of dark matter are the so-called WIMPs, or weakly interacting massive particles, which don’t interact in “regular” processes but may annihilate each other to produce high energy cosmic radiation. A number of cosmic ray and gamma ray detectors have produced intriguing results, leaving scientists with an intricate puzzle of information to assemble into a coherent picture.
An Early Universe 101 December 23, 2008
Posted by sarah in: science . Add a commentI’ve been learning a bit recently about dark matter, dark energy and the history of the Universe, which are all fascinating. Mark over on Cosmic Variance has writted this interesting post on preheating in the early Universe. This proposed phenomenon has important consequences for the formation theory of dark matter, amongst other things.
While I’m on the topic, one of the best books I read this year was The Inflationary Universe by Alan Guth. I admit I don’t read as many popular science books as I should, and I finish even fewer – but this one is a cracker. Guth builds an excellent story about how he arrived at the theory, in collaboration and in conflict with other scientists around the world. It’s a fascinating account of a great scientific discovery, told in such an anecdotal style that it’s super easy to read. It’s completely rekindled my interest in fundamental physics and cosmology, which explains some recent posts (here, or here) on the topic 
More cosmic ray excesses reported November 24, 2008
Posted by sarah in: science . Add a comment
The Milagro cosmic ray detector
In a busy week for cosmic ray science, yet another paper reports the detection of excesses in cosmic ray detections from galactic sources. Using 7 years of data from the Milagro detector, scientists of the University of Maryland and Los Alamos National Laboratory have found two hotspots of high-energy cosmic radiation.
The cosmic ray signature of dark matter? November 24, 2008
Posted by sarah in: science . 1 comment so far
Detecting supersymmtric dark matter
A very interesting paper was published in last week’s issue of Nature – I blogged about it before after reading the NASA press release. It’s wasn’t all that helpful without reading the actual paper but the cosmic ray – dark matetr link caught my attention.
Just today a conference paper (i.e. not peer-reviewed) appeared on astro-ph about some preliminary results from PAMELA – another cosmic ray detector that focuses on antiparticles (positrons and antiprotons). Recall that PAMELA was the source of some controversy earlier this year. Another paper on PAMELA data was posted on astro-ph back in October, it’s listed as being submitted to Nature so again, not reviewed yet. But perhaps another cosmic rays Nature paper soon, and there’s certainly a lot of buzz!
I had a read through these papers and some background stuff – it’s something I didn’t know much about and it’s very cool. Cosmic rays: inneresting akshually!
