tag:blogger.com,1999:blog-323908362024-03-06T11:03:55.587+01:00IAU General Assembly 2006, PragueBlogging from the International Astronomical Union Meeting, Prague, August 14 to 25, 2006Unknownnoreply@blogger.comBlogger78125tag:blogger.com,1999:blog-32390836.post-1160390460370236632006-10-09T12:00:00.000+02:002006-10-09T12:41:01.240+02:00An end and a new beginningThis blog will bear no further entries. Its sole purpose was to blog from the IAU meeting and we had fun writing it. Thanks to Ulrike and Jens for contributing.<br /><br />But this is not the end of the story: We just started a new, more persistent blog called "<a href="http://apparentbrightness.net">Apparent Brightness</a>". It has all the texts from here and will soon get new ones. Check it out!Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-32390836.post-1156164134294378482006-08-21T13:56:00.000+02:002006-08-21T14:45:05.183+02:00J. Casares: Observational evidence for stellar-mass black holesThis is the opening review talk of Symposium 238 on <span style="font-style:italic;">Black Holes: from stars to galaxies asross the range of masses</span>. This will be the last talk I listen to before I have to make my way to the airport, but Ulrike Heiter, a collegue from Uppsala who works on stellar atmospheres, said that she might write a few things from S239 about <span style="font-style:italic;">Convection</span> that starts this afternoon and will go on for the rest of this week.<br /><br />Now to the talk by Casares: X-ray binaries are believed to be a stellar-mass black hole oriting a normal star. From the study of the radial velocity shift, one can determine the orbital period of the system, and from additional information on the star and its mass and properties (inclination of the system), the mass of the black hole can be calculated. The first example for this was 30 years ago.<br /><br />The reason why these systems shine in X-rays is that material streams from the "donor star" towards the BH and forms an accretion disk around it that gets hot enough to do that. Depending on the type of the donor star, the accretion disk may even be optically brigher than the star during an active phase.<br /><br />The basic argument of course is, that when you find an object with a high mass that orbits closely with a star, but you cannot see it and physics tells you that there is no way to have such an object withstanding its own gravitational pull, it must be a black hole. However, the number of dynamically confirmed BHs is still quite low (~20).<br /><br />Also the lack of pulses and X-ray bursts indicates that there is no hard surface onto which things can bounce.<br /><br />So how many are there and what is the mass-spectrum? Extrapolating from the known numbers tells that there should be 1000 dormant X-ray Transients (i.e. binaries) in our galaxy (this fits with binary models), but from stellar evolution, there should be 10^8 BHs in the Milky Way, out of which only the tip of the iceberg can be seen as XRTs. <br /><br />The 15 reliable mass estimates range from 4-15 solar masses with more objects on the low-mass end. The most massive ones seem to lie above the values predicted from stellar evolution (Fryer & Kalogera 1999), but we are talking small-number-statistics here (2 objects).Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-32390836.post-1156157004167199592006-08-21T12:35:00.000+02:002006-08-21T12:43:24.166+02:00G. Tancredi: Activities of the Observatorio Astronomico Los Molinos, UruguayWhat can be done with a small telescope and a CCD-camera? Quite a lot. The speaker lists several projects that they do at their facility, including confirmation of near-earth objects, comet identification and photometry, asteroid photometry and astrometry. The common-day follow-up observations are valuable contributions to the scientific community and also attacking region in the sky that are rarely studied is a productive niche.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-32390836.post-1156156273376002572006-08-21T12:07:00.000+02:002006-08-21T12:34:35.420+02:00O. Alvarez: Planetario Habana: a cultural centre for science and technologyThe funding for this planetarium came internationally (maybe from IAU, I did not get that) and they use it to build up a center for the teaching of science and technology in central Habana. It is integrated with the museums of the city and will promote astronomical knowledge to the public, including cosmology. Architecturally, the big sphere inside the building that will hold the planetarium represents the sun and there will be models of the other planets in the same scale.<br /><br />Opening will be in the end of 2007.<br /><br />An inportant comment was made, namely to get to ineract with the teachers and provide help for them and a special program that is different from the popular show. Many planetaria seem to have problems to keep a steady audience that is used to visually impressive films and shows.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-32390836.post-1156154627124598392006-08-21T11:48:00.000+02:002006-08-21T12:03:47.133+02:00P. Rosenzweig: Encounters with science at ULA, Vernezula: An Incetive for LearningThis is about a program to establish science on all levels of education in order to counteract the lack of interest in science and the deterioration in the learning of science. They provide well prepared personnel which can aid faculty members who want to improve things and they organise events ("Encounters with Science") for children at the school of science where an extra effort is made to fight the impression that science is hard and that scientists are heartless, boring people.<br /><br />These events have many stands with experiments (with much voluntary work from students) and are very popular with several thousand participants and intensive media coverage. This initiative from the most western part of Venezuela has spread over many parts of the country and will soon be held for the seventh time.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-32390836.post-1156153432084026862006-08-21T11:26:00.000+02:002006-08-21T11:43:52.096+02:00J. Fierro: Astronomy for Teachers in MexicoThis talk is about basic education and with a wonderful metaphore (ape-mother teaching the use of tools) she points out the basic structure of learning which includes the natural interest of children and practical experiments.<br /><br />The speaker was adressed by pre-school teachers with 650 questions of the children and there were books written about how to answer them. These books are very helpful for and popular among teachers. Several other books are presented and she throws a copy of each into the audience. :-)<br /><br />In middle school, where pupils think more about sex than science, the curriculum is less on astronomy and more on social problems and there are books by the speaker where different issues are adressed in a popular but scientific way.<br /><br />Finally, she stesses the importance of teachers and of finding good ways to teach, because education is the most important way to leave underdevelopment.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-32390836.post-1156152378217034932006-08-21T11:05:00.000+02:002006-08-23T08:31:21.893+02:00H. Levato: Formal Education in Astronomy in Latin AmericaThe speaker starts with an overview over the countries and places, where astronomy can be studied both at undergraduate and at graduate level. The amount of activity and students scales with the size of the country. 90% of the 500 PhD students in astronomy are in Argentina, Brazil, Chile and Mexico.<br /><br />There is an intermediate group of countries, where there is serious effort in astronomy, but it would take more resources to consolidate their astronomy programs. The largest number of countries however have seriuous deficiencies in that respect. The speaker also found a correlation between the astronomical effort and the reply-time to emails. :-)<br /><br />Although there are many astronomical facilities in latin america, it is the people who write the papers and it often is manpower which is the limiting factor.<br /><br />In a comment it was pointed out, that Venezuela probably should belong to the first group, which the speaker already had suggested, but with a question mark.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-32390836.post-1156149483819104572006-08-21T10:26:00.000+02:002006-08-21T10:38:03.826+02:00J. Ishitsuka: A new astronomical facility for Peru: transforming a 32m-antenna into a radio telescopeThere are some big antennae around that are not used anymore, because communication has been replaced by other means. Making telescopes out of them requires expertise which not necessarily available. For this project in Peru, they collaborated with japanese astronomers.<br /><br />The tansformation of this satellite communication antenna shall start radio astronomy in Peru, create radio anstronomers by gathering knowlege and of course promote international collaborations. The antenna is good enough to go up to 2.2 GHz and the site is high up, remote and has good conditions. The location on the globe also makes it interesting for Very Long Baseline Interferometry. They have a working reciever and are well underway.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-32390836.post-1156148667965862822006-08-21T10:12:00.000+02:002006-08-21T10:24:27.976+02:00S. Haque: The Caribbean view from the ground upIntitially, the drop-down list in the registration form for this meeting did not contain Trinidad (the speaker's home) - this was corrected. With a country of one million inhabitants and two astronomers, they are approached from all sides of society, also religious, for information about calenders and the sky. There is an effort on online-teaching and there are popular events like "star-parties", however classical seminars are widely ignored.<br /><br />Astronomy is in the primary school curriculum, voluntary student work is very important and at university level they have succeeded in sending students to internatonal winter schools and universities. Research has mainly been theoretical, but now also contains others, like astrobiology.<br /><br />They have a 46cm telecope, mainly used for monitoring quasar variability.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-32390836.post-1156147930544286062006-08-21T10:07:00.000+02:002006-08-21T10:12:10.546+02:00R. Kochhar: Promoting astronomy in developing countries: a historical perspectiveIs astronomy a "western astronomy"? There has been astronomy going on all over the world during mankind's history. The speaker tries to get attention to insensitivities that for example are written in the history section of textbooks. The "cultural perspective" should be taken more into accont.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-32390836.post-1156147447826142692006-08-21T09:53:00.000+02:002006-08-21T10:04:07.836+02:00J. Hearnshaw: A survey of published astronomical outputs of countries 1976-2005I could not resist to return to the meeting anyway before I fly back to Sweden tonight. I was tempted by the Session about the "Virtual Observatory", but I guess one can find out about that on the web anyway.<br /><br />Therefore, I am sitting in the Special Session 5 on "Astronomy for the Developing World" right now. I only got the last minutes of J. Heranshaws talk, but the summary contained the following:<br />- There are 1.39 astronomers per million population over the world.<br />- There are 9000 members in the IAU.<br />- The majority of papers is published by IAU members.<br />- 112 countries have no IAU members, but 3/4 of the world's population live in IAU member-countries.<br />- The GDP of a country correlates with the number of it's IAU members.<br />- It also correlates with the number of papers published.<br />- Since 2001, there has been a rapid increase in multi-national papers and large collaborations.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-32390836.post-1155975291598536392006-08-19T09:17:00.000+02:002006-08-19T10:15:59.856+02:00The Planet IssueBelow I commented on the link to this blog from Seed Magazine where they said that one could find out about Pluto being a planet or not in this blog. I wrote that I will not write about this issue at all because I find it unimportant. They now have even <a href="http://www.seedmagazine.com/news/2006/08/seeds_daily_zeitgeist_8152006.php">added a reply</a>, correcting their "mistake". :-)<br /><br />Maybe my choice of words was provocative, but for some reason, most of the links to this blog seem to be about these three lines and how bad they are. I will now list the major critics and adress them. Some wrote that:<br />1. I was a snobbish extra-galactic astronomer bashing planetary science.<br />2. I had forgotten where my money came from and that popularising is important.<br />3. Even if this topic may be unimportant, it attracts attention and all popular attention to astronomy (or the IAU) is good.<br />4. I should have written about it.<br /><br />My replies:<br />1. This could not be further from the truth. Yes, this subject is quite remote from what I do myself, but finding out how the solar system came about is great science and with the discovery of extra-solar planets, this topic is deservedly becoming more and more popular among astronomers.<br /><br />2. Of course it is! Popularising is immensely important and I think that every astronomer is aware of that. But isn't it somehow logical, that I try to do that in my own field? To justify that what I myself do is interesting and important? If that is not possible and unapplicable, I totally agree that planetary science is a popular topic. When I do popular shows at our <a href="http://www.astro.uu.se/history/images/refraktor.jpg">old refractor</a> I certainly do not point at feeble galaxies, but at the moon and the planets.<br /><br />3. Now we come to the point where I disagree. Attention for astronomy is good, yes. The topic, if Pluto is a planet, and how to define a planet has gotten attention, yes. Does that make it good automatically? I think not and here is why: It is semantics and not science. It creates the (almost totally wrong) impression in the public that what astronomers do is sitting in committees and debate what a planet is. Is that what they are willing to give tax money for instead for new discoveries? I doubt it. In addition, it takes the media attention away from real science (including planetary, in case you missed point 1.) and I think I am far from the only one who feels misrepresented by this issue.<br /><br />4. Must I write about everything? I think everyone has to make choices because you cannot cover all. I wrote about this meeting from my own perspective and the meaning was to give people a glimpse of what is going on here. I chose to ignore the "planet issue" and hope it became somehow clear why.Unknownnoreply@blogger.com4tag:blogger.com,1999:blog-32390836.post-1155916512848588062006-08-18T17:49:00.000+02:002006-08-18T17:55:12.856+02:00The second weekI just tried to convince a collegue, who will be here during the next week, to continue what I started. I've said it before: If you yourself are an astronomer at this meeting and are interested in blogging here, please drop me an email (thomas.marquart (at) astro.uu.se) and I'll add you to the list. The technical part is easy.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-32390836.post-1155915114938126212006-08-18T17:15:00.000+02:002006-08-18T17:31:54.946+02:00The end?First of all, thanks to Jens, who also wrote some summaries during the last days and posted them below.<br /><br />The poster session is over (I got some nice feedback from people), I have checked out and will soon meet the guy with whom I'll be staying over the week-end (with <a href="http://hospitalityclub.org">HC</a>). This means the conference is over for me and I certainly enjoyed it.<br /><br />During the week-end, I'll finally get to see Prague. There is a slight chance that I will attend some talks on Monday before I fly back to Sweden in the evening. If not, I will at least address some of the critics that I got for turning down the "planet issue" below.<br /><br />It was fun to write this blog and it felt good that it at least got some attention. Thanks to all readers. At times it was more effort than I expected to simultaneously listen, get the major points and rephrase them in own words. I will have to read over all of it after a while to judge for myself if I succeeded or not.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-32390836.post-1155902814772641842006-08-18T13:15:00.000+02:002006-08-18T14:06:54.780+02:00Friday's star formationI missed some talks in the morning, but sleep is important, too. I came in time for the last three talks of S237 on "Triggered Star Formation in a Turbulent ISM" and all three were interesting.<br /><br />C. Norman was talking about his theoretical work on disk simulations and what struck me a little was that people have enough confidence in the simulations being a good approximation for the real world, to do physics with "observations" on the simulated world and derive properties and laws from there. Of course, this is tempting since one has complete control over the simulation and can get much better "data" than in the real world. There are tons of arguments and tests that reassure and convince people that this really works and, indeed, why should a program that implements a well-understood physical process fail, except for (also well-understood) limitations like resolution and other approximations. But still, if one could observe it, one would not need simulated data, so since we cannot, there is also a lack in testing the simulations to the real world.<br /><br />Using the density distribution function of the ISM (log-normal except at very low densities) and a scaling relation for the critical density where SF sets in, Norman showed an alternative to the Schmitt-law (also called Kennicutt-law) that has a more shallow slope and flattens out at high gas surface densities. The observed slope then has to be understood by a change in SF-efficiency, which offset the model with respect to each other. Since the observed correlation is very tight, this would mean that also SFE correlates tighly with gas density.<br /><br />The next speaker, M. Krumholtz, started from simple arguments to understand why SF is so inefficient in the sense that the SFR would be 50 higher (both in the Milky-Way and in extreme cases like Arp220) if all the molecular clouds that are present would collapse and form stars. I cannot reproduce the whole line of argument now, but he also used the density distribution (depending on mass and virial parameter) in the turbulent medium and integrated over the region above the critical value to get SFRs which fell into the observed regime. This could be tested, if the census of molecular clouds in nearby galaxies would stretch to smaller masses, by simply comparing the predicted SFR as derived from the molecular gas content with the observed one.<br /><br />The last talk and summary of this symposium was given by B. Elmegreen and he again stressed the importance of turbulence for SF, instead of the older picture of monolithic collapse of a molecular cloud.<br /><br />In the afternoon, there will be a "poster session", which basically means that everyone who has a poster, stands by it to answer the questions of the people coming by. The problem is that, although not all have posters, many do and one has to find the balance to also look at the other posters and talk to the author, but that won't work if they just do the same thing. Surprisingly, it always works out somehow anyway and I am happy that they scheduled this also for S235 for which no poster session was planned initially.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-32390836.post-1155831034246123002006-08-17T17:50:00.000+02:002006-08-17T18:10:34.260+02:00M. Hudson: "Downsizing" from the fossil recordThis is the final talk of Symposium 235 on Galaxy Evolution, but there will be much more other things going on tomorrow that are worth writing about.<br /><br />Downsizing was mentioned frequently during the last days and in the presented survey, red, emission-line-less cluster-galaxies are used to measure the "fossil record" of galaxies, i.e. the old stars. The thousands of spectra are sorted by velocity dispersion (a measure of the total mass) and stacked together to get high quality average spectra with many spectral features that can be analysed to get ages of the stellar population.<br /><br />Tey find that the smaller galaxies have smaller ages, i.e. downsizing. The age-spread is much larger at low masses than at the high-mass end. There was no morphological selection but of course it is ellipical that dominate the sample. The S0-type galaxies are slightly younger than Es with the same sigma, but this trend is weaker than the trend with sigma itself.<br /><br />Comparisons with the total dynamical mass (also using Sauron-data) there is little room for dark matter (25%).<br /><br />The ages also correlate with environment, i.e. distance from cluster center (16% change). Again, this is not a strong trend. Metallicity does not show a trend, but alpha-enhancment does. The tilt of the distribution in a color-agnitude diagram comes half from ages, half from metallicity.<br /><br />By calculating backward, how te CMD would have looked for these galaxies at some earlier time, they can be compared to CMDs at some redshift.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-32390836.post-1155829815306905422006-08-17T17:29:00.000+02:002006-08-17T17:50:15.320+02:00O. Gnedin: The formation of dwarf galaxies and small-scale problems of lambda-CDMThe Lambda-CDM cosmological model works very well in predicting large scale structure. It however predicts many more dwarf galaxies than are found. This is called the "missing satellite problem" and it is not just a few missing, but it should be ten times more.<br /><br />The solution may be twofold: fist of all, only the more massive of satellite halos may be able to retain enough gas to form stars and thereby are seen by us. In addition, subhalos evaporate due to tidal forces, once they come close to "their" big galaxy. It has been known since long from studies of the Local Group that different types of dwarfs live at different radii from the large galaxies and there seems to be an evolutionary connection.<br /><br />A new method of measuring the DM-halo of the Milky Way are hypervelocity stars that move at 500-1000 km/s with respect to us. They probably have been slingshotted by the black hole in the center of our galaxy. By following and calculating the paths of these stars, the shape of the DM-halo can be determined and according to CDM, it should be triaxial. This test will yield first results in a few years and it is a good test of predictions from lambda-cold-dark-matter cosmology, which is the widely accepted picture of our universe.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-32390836.post-1155828536286433532006-08-17T17:06:00.000+02:002006-08-22T17:37:38.743+02:00C. Conselice: Galaxy Interactions and Mergers at High RedshiftsWhen do galaxies merge? The merger fraction does evolve lowly up to z=1.2 but at around 2-3, 50% of all high-mass systems are mergers. The small ones again have only slightly higer merging rate. So at z=1 most of the high-mass objects were in place.<br /><br />Using the same methodology to find mergers on numerically simulated data (with C. Mihos), they derive absolute merger rates (per volume) and a sharp drop after z=1 is found for all masses. A typical massive elliptical galaxy (today) will have undergone 3-5 major mergers since z=3.<br /><br />A significant fraction (maybe the majority) of SF at z<1 is produced by interactions and mergers. I think this is last point is still debated and there have been contradicting results, e.g. showing that interactions dot not really increase SFR as much as one would think.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-32390836.post-1155827167772731342006-08-17T16:43:00.000+02:002006-08-17T17:06:08.026+02:00D. Elmegreen: Clumpy Galaxies in the Early UniverseBy looking at the Hubble Ultra Deep Field (UDF), one can classify galaxies by how they look. The number of clumpy and irregular looking galaxies increases as one looks at further and further distances. Disk galaxies seem to disappear at a certain redshift and only thick disks are found.<br /><br />Clumpy galaxies seem to be more frequent at high z and it is basically the large star forming regions that are seen there. These clumps should dissolve and could build up a normal spirals. Indeed the "clump clusters" share several properties, altough they are less massive. The scale height of "clump chains" is found to be 1kpc, which could be connected to forming a thick disk.<br /><br />A usual problem here is that one looks with a fixed set of filters (opitcal in this case), but due to the redshift, one looks at different wavelenths inside the galaxy. In this case, one admittedly only sees the regions that actively form stars and a much smoother underlying population of older stars would not be seen.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-32390836.post-1155823285973120612006-08-17T15:30:00.000+02:002006-08-17T16:01:26.150+02:00R. Bouwens: Galaxies Buildup in the Frist 2 GyrUV-luminosity functions at z=4,5,6 are presented and <span style="font-style:italic;">no</span> evolution is found at the low mass end and the slope is steep there (-1.75). However, at the high-mass end things get brighter with time. This is the opposite of downsizing that I wrote about yesterday. <br /><br />Converting this to the Madau plot means that it peaks around z=4 and declines towards 5 and 6. This is heavily debated since the dust-correction at high z is fairly uncertain.<br /><br />Going even further (z-J), they found 4 candidates of z~7-8 galaxies (Bouwens & Illingworth, Nature 2006).Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-32390836.post-1155821268016838302006-08-17T15:03:00.000+02:002006-08-17T15:27:48.076+02:00T. Wilkind: Massive and old galaxies at z>5If galaxies form hierarchically, i.e. big ones form by the merging of small ones, shouldn't big galaxies then appear rather late in the history of the universe? One cound think so, but would be mistaken. Tommy repots on their finding from last year of a massive galaxy at z=6.5 that is red in color and show no ongoing star formation at all.<br /><br />Is the presence of such an object that has finished forming all its stars at so early times a threat to the lambda-CDM cosmological model? This first of all depends on how many of these really exist. They look in the K-selected GOODS-south sample and find 18 candidates out of which 5 had to be discarded as being something else.<br /><br />So they have 13 galaxies at z>5 with over 10^11 solar masses in stars and no ongoing star formation (although 50% are detected in 24micron). Correcting this for completeness gives a rather high number density which indeed opposes the lamba-CDM paradigm (too many as compared to existing DM-halos at that time), unless these estimates are either flawed in redshift or stellar-mass-estimates.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-32390836.post-1155819731601001562006-08-17T14:33:00.000+02:002006-08-17T15:02:11.610+02:00M. Steinmetz: Cosmic Web - SimulationsThe "Cosmic Web" is the structure that arises in cosmological simulations and that is also observed: the universe is clumpy and most of the matter is in huge filametary structures that are made of and connect galaxy clusters.<br /><br />In simulations the control of the dark matter is much easier than normal matter since it only interacts by gravity. With normal matter, one needs recipies for handling star formation, hydrodynamics have to be taken into account.<br /><br />Very important: he shows in simulations that a merger may actually look like a disk in kinematical data and he warns the people around Genzel who find "rotating disks" at high redshift. I have to find that movie/paper on the web.<br /><br />Simulated disks nowadays however seem to fit nicely wit observed ones when it comes to angular momentum. A comparison of a merger with and without AGN feedback is shown and it helps in the sense that otherwise simulated galaxies are too centrally concetrated as compared to real ones.<br /><br />To test if angular momentum is induced to disks by tidal torques from the cosmic web, it is possible to check the orientations of disks. Indeed there is a correlation between the large scale structure and the orientation of disk galaxies.<br /><br />The Milky-Way dark matter halo seems to rotate with around 100 km/s as derived from halo star kinematics. But I might have gotten this part wrong. :-)Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-32390836.post-1155817972611341062006-08-17T14:04:00.000+02:002006-08-17T14:32:52.700+02:00L. Portinari: Cosmological formation of disk galaxies and the Tully-Fischer relationThe Tully-Fischer relation (TFR) for disk galaxies relates the absolute luminosity to its rotation speed. The angular momentum in simulations however is difficult to match with observed values and this is most probably due to the simplified treatment of baryons and thereby, again, feedback.<br /><br />The question if the disk forms from a cooling flow from hot gas (at virial temperature) or by cold accretion is adressed and X-ray observations can give important clues here. Birnmoim & Dekel 2003 found less than 10% of the expected amount of hot gas, so cold accretion might be favorable. Gas does not need to be heated to virial temperature and there can be cold gas accreting along filaments.<br /><br />They found an offset in the TFR for certain models but it was hard to grasp which objects they were, but one solution is claimed to be dynamical friction, i.e. the galaxy rotates slower than it should for the same luminosity.<br /><br />Portinari et al. 2006 look at the evolution of the TFR from z=1 and find no significant mass evolution, while the individual objects gets to almost twice its mass.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-32390836.post-1155809445832478532006-08-17T11:50:00.000+02:002006-08-17T12:10:45.840+02:00A. Shapley: Galaxy Formation in protoclusters at high redshiftThousands of UV-selected galaxies at z>1.5 with spectroscopic confirmation from Keck. 25% contain AGN. From clustering length (4 Mpc) the DM halo mass is derived to roughly 10^11.5-12 solar masses and these objects are presumably the progenitors of nowadays ellipticals (by following halo-evolution in simulations).<br /><br />The highest X-ray detected cluster is at z=1.45. The speaker and collaborators find protoclusters at z>2 also from UV and measure/find the overdenities (factor 7) in a redshift subslice. The galaxies there have double stellar mass than the ones outside the cluster. They find the morphologies not to fall on the Hubble sequence, but I wonder if they took into account that even normal galaxies look very different in different wavelenth, especially in rest-frame UV which the HST images were made in, if I got it right.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-32390836.post-1155808070651997012006-08-17T11:31:00.000+02:002006-08-17T11:47:50.660+02:00M. Franx: Properties of galaxies at z=2-3Between z=2-3 presumably many galaxies build the bulk of their stars and one has to have control over sample properties and selection effects.<br /><br />The authors and collaborators select galaxies in rest-frame optical which means deep NIR-imaging with VLT in that case (MUSYC-survey). They place a mass limit at 10^11 solar masses. At this massive end, the red galaxies dominate the population (77%) already at that time.<br /><br />But these red galaxies are not "dead", but still show significant dusty star formation. In the U-V over V-J diagram, a large part of the population lies below the local population.<br /><br />Clustering correlation length correlates with J-K color (Quadri et al. 2006) which means that redder galaxies ar emore clustered.Unknownnoreply@blogger.com0