 Hello everyone and welcome to this new webinar of physics and it's a pleasure designed to have here to our radio Carnero Rossell and he will present some results about the EAS, the Dark Energy Survey and telescope and well in relation with the cosmology and well the last week was very active for the these webinars of physics because we have a celebration of the 50 webinar and also we have this Darmatter day that I invite you to follow on the on the YouTube channel that we have and well just visit this and give us some likes okay and well I would like to remind you that well you can ask questions to Aurelio in YouTube in the chat of the YouTube I think around here and well some words about Aurelio, Aurelio did his PhD in CMAT in Madrid and he is now post-doc in Rio de Janeiro in the National Observatory in Brazil and in the Laboratorio Interestitucional the e-astronomia in Rio okay and well Aurelio thank you very much for being here and well if you want to say something and starting or if you want to start sharing your slides please go ahead thank you very much can you hear me yeah we perfectly so I hope you are seeing the first slide thank you all and thank you for the invitation I would like to speak today about the most recent results from the dark energy survey compromises the first year of observations and my name is Aurelio Camero and I'm working at Observatory National in Rio de Janeiro inside the Laboratorio Interestitucional the astronomy so basically today first I will do a brief introduction about dark energy how we can measure it from the sky and what are the current constraints on dark energy then I will do a basic introduction to gravitational lensing which has been the first the main method to obtain this first year cosmological results in the dark energy survey so after the introduction I will talk about the status of the survey and finally talk about what it's important today which are the new cosmological results I would like to thanks to Daniel Grunin and Judy Pratt that some of the slides I took it from past lectures from them but we are colleagues so that's not a problem to start with think about the universe in larger scales or the universe is described as an homogeneous fluid in an expanding universe in in common sense when we look around we see that gravity exists and gravity likes to pull things down to to to group things so in principle when we think about the universe we would assume that the universe is made of matter and this equation is the field equation of general general relativity where the dynamic of the universe is contained in the Hubble factor which is these eight knots divided by a where we were a is the scale factor basically is how much the universe expand in a time interval and and the and the expansion rate which is the acceleration of the expansion is given by eight knots so this is would be like the common first approach to the universe we have matter and other species like radiation and neutrinos but then in the end of the 20th century we discovered that actually there was another contribution that is making the universe to expand in a accelerated way in a universe with only matter we would expect the acceleration to to decreased but observations actually tell us that the expansion rate at this time is actually accelerating it's positive acceleration so in the field equation we have also a solution adding a constant so this constant could be associated with this effect that is making the expansion to accelerate that's why the dark energy is normally associated with the cosmological constant which would be the the easiest model which could integrate this effect into equations so we have these terms that are unknown in principle which is the density of matter and density of energy of dark energy in order to close the model the actual model we need to add four additional three parameters one is sigma eight with the amplitude amplitude of density fluctuations the ratio of neutrino masses the rate of expansion today and the scale dependence of density fluctuations in the in the the current model based on observation we are actually measuring that the universe and energy density is made 70% of this unknown term that we can associate with the with the energy of the vacuum also 25% of dark matter and 5% of ordinary matter which is baryonic matter so just to give you a hint of what this model can explain we have observation of the very early universe and we can make a photo of the cosmic microwave background which is a remand radiation coming from the big bang or when the universe was very hot and dense and the the the temperature distribution it fits exactly with a with that of a black body of a black body so the universe was very homogeneous in the early universe but then when we go to late time which is in our current time we actually see that the distribution of matter is very clustered is very condensing clams and filaments which are this structure here that we can see on data on the plot from slow and digital sky survey on the back of the images is a result from simulations so the this model assuming that the universe is a perfect fluid it's actually able to explain how structures grows from a very homogeneous universe because here we see in homogenities but these are on a scale of 10 to the minus 5 in density so the humor the universe was very homogeneous but today is very cluster and we can explain this with this model so as I said these are quite odd model in the sense that most of the unit of the content of the universe we don't know what it is 70% of the energy is an unknown substance that appear like vacuum energy although there is a drawback that the standard theory of quantum field theory predicts 100 120 times a bigger energy density than what we observe in the universe also 80% of the matter is unknown in the form of dark matter that only interacts via gravitation but fortunately even if it's other actually we have a lot of independent observation that sustained this model this model is mostly phenomenologically together with the question of general relativity but the three parameters that I said amplitude of fluctuations the content of energy matter neutrinos these are all three parameters that we need to constraint so some of the questions that we can ask to start investigating about dark energy that we might find hints about the nature of or the content of dark energy in the universe is if we are the the physics of the early universe which is for example this image from CMB and the physics from late universe which is this image where we have galaxies and cluster of galaxies are those fitted by the same parameters also do measurements of cosmic distances and growth of a structure agree also we can try to look at changes in the in the energy density of dark energy basically what this means is trying to obtain the equation of a state of dark energy defined as the pressure divided by density if we can find variation through time of the question of state of dark energy this will imply that dark energy is not the cosmological constant for example so these are some of the observables that we will that nowadays surface try to answer looking at the late universe and comparing with early early universe measurements of cosmic distances and growth of a structure in order to obtain the question of a state of dark energy so how do we observe dark energy in the universe we have basically dark energy enters into observation in two different effects one is it actually modifies the rate of expansion as many dark energy we have in the universe the universe will expand quicker another the dark energy is sensitive to the growth of a structure which means as we said in the early universe the universe was very homogeneous but today is very structured we have filament galaxy clusters so this that is the growth of a structure through time is sensitive to the amount of dark energy in the universe so the question that we need to ask is do all these measurements agree with predictions in the same fiducial lambda called our matter model and the answer is for now it looks like so now I'm going to explain the current status of observations of dark energy basically the expansion history of servables that would be which in this previous slide I'm talking about CnB, Vio and supernova the idea is that we compare known distances or known objects at different times and we can create like a distance ladder from the early universe to today and that's what different surveys have done here measuring the the the BOS scale so one method to study the expansion history is to look at standard rulers imagine that we know a physical distance that is imprinted in the CnB and down this physical distance can be later measured in late-time universe looking at the galaxy distribution and then we can compare the size of the scale this is what we I'm showing in the top plot basically the gray area is the measurement of the sound horizon in the early universe when the universe was 30, 3800 years and and today in the galaxy distribution we can measure the same scale but expanded at later times and in the distribution of galaxies this is called baryonic acoustic oscillation or Vio so as we can see here in the top panel the agreement between the measurement of the sound horizon is in gray and how the prediction of the sound horizon scale at different red shifts they agree all the it agrees with the measurements done at late time using 6DF, SDSS, BOS and WGLZ. Another case to study the expansion history is to look at standard candles imagine that we know the intrinsic luminosity of an object of an event in the universe if we observe at later times or at different times we will see a dimming of the light and we can correlate to obtain the distance this has been used fortunately we have supernova type 1A that are considered as standard candles and we can plot its magnitude as a function of redshift and we see that the prediction of the CMB which is the gray line behind the point agree very well with our with the current measurements of supernova and these two measurements give very tight constraints on dark matter and dark energy. Another observable that we have to measure only the growth of a structure is the redshift space distortion basically I won't give into I won't enter into details about here but basically this the redshift space distortion effect what it measures is in in a cluster of galaxies we measure redshift to obtain their distances but these galaxies have peculiar movements where the galaxies in fall into the cluster so we can measure blue shifts and redshift on top of the expansion redshift and this can be measured to give us a hint of the strength of gravity at that time and the measurements today they are all agree with a fiducial lambda called dark matter which is signalized in this plot with a gray band which are the results coming from from CMB experiment so this plot are showing that late time measurements with this galaxy surveys agree with measurements of the early universe then we have the other observables like the galaxy cluster number counts this this observable depends both on growth of a structure and expansion history and it give and basically we measure the amount of galaxy cluster as a function of redshift and mass and it is very it is sensitive to that energy in a sense that is actually very good to to separate to break the generacies of other methods for example this plot on the right is on based on simulations we see that the clusters at quite good constraints to other observables like supernova in green CMB which early universe and VO that is late time universe so it's promising is very promising the use of galaxy clusters to improve the constraints on dark energy although the results that I'm presenting today we are not using cluster number counts yet again all these results are consistent with fiducia lambda colder matter and now I'm going to give a small brief up a summary on gravitational lensing since it's the main method using DS basically when light passes through massive structures it feels gravity and its path will get bent that is why we this effect is called gravitational lensing because it's similar to an optical lens so these the this distortion causes shifting and magnification of the images of background galaxies as well as a shear so they here on on the bottom I'm showing some example of some extreme gravitational lensings where in the center we have a bright galaxy yellow and then there are these rings around which are actually images of normal galaxies that but the images has been sheared due to the mass of the galaxy in front in so the method that we use in DS is basically measuring the shear of galaxies around galaxy clusters in order to to obtain a mass mass map because this method is only sensitive to the amount of mass which is in front of the of the galaxy so the shear of the galaxy is a function of the mass that finds in its path to us so this is more like a visual image of what the shear image is here maybe it's not very clear but for train eyes you get you can see these yellow points that are bright galaxies and on the back there are a lot of blue small galaxies if we would measure the shears of the galaxy we will see that they are correlated with the position of this galaxy cluster telling us that the giving giving us and an amount of the matter that is in front of us remember that most of the matter is dark matter is not luminous matter so we could not make the same we could not obtain the amount of shear if we only count the the visible mass we really need dark matter to too much to our observations so recent results from cosmic shear from galaxy from gravitational lensing claimed to have detected at two three sigma offset from a surement of early universe which is CMB versus late-time universe obtained from galaxy surveys with kids and see fetch the lens but the thing is like is this effect comparing the red circle the red contours versus the green one is this a non-issue is this actually statistically significant is this maybe pointing to a crack in the model or is maybe a systematic error from the surveys so this was kind of the answer that we tried to well that's with a question that we try to answer with this first year analysis if this effect if we could see this this offset in the DS data and if it was a significant so going to the dark energy survey now I'm going to explain the results from the first year's observation the dark energy surveys and imaging galaxy survey a mapping five thousand square degrees of this in the southern hemisphere in five years we are already in the taking the five years observation still we are only presenting the first year observations where we are still having four years ahead of us to to analyze it's a we are using a camera in the telescope in the several total inter-american observatory in Chile serving in five filters covering the the optical GRI and the near infrared Z and why this is the footprint of the area that we have observed the results that I'm presenting today are based on on what is shown as red in this plot covering around 1500 square degrees and covering the observation from to 2013 to 2014 so the results I'm presenting today of course are not only mine this is a great collaboration of more than 400 scientists and actually now they are meeting in Brisbane in Australia where it's happening the DS collaboration meeting and this is a photo from the previous one in Chicago so we are universities from the US mainly but also England United Kingdom Spain Brazil Australia Switzerland and Germany so in DS for the year one results we use actually we didn't use only weak lensing but we could cross correlate with results of large-scale structure which is basically the distribution of galaxies in the universe so with these observables we we measure the positions of galaxies that has been lens that are tracing the large-scale structure and also we made we measure shapes of these galaxies then we can combine the measurements of the galaxy autocorrelation function which is basically proportional to the density of galaxies then we can measure directly the pure cosmic shear which is a correlation of shapes and shapes and this is a this is proportional to the density of matter I didn't explain but the density of galaxies here as you can see this small formula is given by a galaxy bias B times the density of matter bias give the the ratio of galaxies as a function of the matter field but also we can make a cross correlation between cosmic shear and galaxy autocorrelation function and this will be proportional to the density of galaxies times the density of matter so these are the three formulas of observations that we are going to measure from data and finally combining these measurements we get the best constraints on year 1 data so the the measurement of the the shear it get us directly to to the content to the mass content looking out the autocorrelation we need to look at galaxies which have these bias that sometimes is can be unknown but cosmic shear actually looks directly to dark matter because it's made of 80 80% of the matter is that matter so basically we can make a map of the matter content due to the shapes due to the shear of the images of the galaxies and this is one of the results of the survey we have created the biggest matter map up to date and covering from redshift 0.2 to 1.3 by looking at the shear of galaxies so with this map we can also we can study the the dark energy content at late time of the universe but to get here this is important a thing to remark that we are entering the dark energy survey enters into the realm of big data so we had many different and we had to carry a very detailed analysis of the data that we take from the telescope we created the gold cataloging that you can see in three cowback net at all paper we create red magic galaxies we can calculate the shear catalogs and we finally obtain the galaxy clustering and cosmic shear but to do so we also need to understand the wretched distribution of the galaxies we need we need a very robust analysis of systematics to get to the final final results I'm putting this slide as well to to reference many of the authors of this analysis that you can find today in the archive and also in the dark energy webpage so as I said with big data demands a great we have great statistical power we need a great systematic analysis since we have an unprecedented size and depth of automatic data this has been very well calibrated then the shear measurements has been measured by two completely two independent codes and calibration to and both both pipelines actually agree on the results we have we did a full treatment of covariance matrices including nuisance parameters which are those that we might not know their value for example uncertainties in red sheets uncertainties in neutrino mass and then before we produce the results we tested in simulations and in theory and we applied two different mc codes cosmo like and cosmosis that gave us also the same results so we we develop a machinery to be sure that we we were obtaining robust results from from good data where is it where is a novel thing that we did again this is the mass map that we obtain so measure I mean a cosmic shear as I explained earlier light passes through distant galaxies and when it passes their light path gets distorted and we can measure the shapes and also we measure correlation of shapes of galaxy pairs we created a catalog of 35 million galaxies and we measure with a different independent methods and we got the same answer independent of the algorithm so the measurement of cosmic shear during the analysis we were very aware of not being blind of not being biased by our perception of the data this is a an important issue that is starting to be common at least in galaxy surveys is that we need to make the preliminary tests on blinded blinded which means for example if we look on the plot we can see on the top we can see the results from plank in red and in orange the results from other galaxy surveys and here we have our constraints but there has been shifts so we don't want to know the value yet we only we only release reveal the results when we have passed all the tests and all the systematic tests so of course our result is not here it has been shifts so we are not biased by our perception imagine that we find a discrepancy and maybe we say um this discrepancy I don't like maybe I have done something wrong so to avoid that let's make be sure that we have everything right and then we look to the result so as I said we will not use only shear but we can we use also galaxy clustering the combination of three these three joint analysis maximizes the use of information and this is the largest individual data set and now join constraint from these three probes for the first time so this is a novelty in the community so combining these three observables as I said what are the consistency of the individual constraints from these three observables we have matter density the cross correlation and the shear-shear measurements so these three observables give us similar results we are not showing the results yet this is only to see the consistency of the different measurements and we use the criterion of the bias factor and also we did other systematic tests to to demonstrate that the three observables are are consistent and they give us a bias factor of 2.8 for the three hypothesis the the shear measurement the cross correlation and the auto correlation of galaxies and these is already one so one of the results as we so as you can see we agree to one to sigma with Planck which are results from early universe versus our results are late-time universe that are in orange so as I said in the start when I talk about gravitational lensing there seem to be some discrepancy between early universe and us and I say okay was that significant or not we are also finding an apparent minor discrepancy but is this really a discrepancy well actually not if we look at the bias factor the results from Planck agrees with those from DS in the sense that a combining a central value that would be represented by the green line if we measure it with two different experiments can give us the results that we obtain so basically we haven't found any discrepancy with Planck therefore we can combine the results from Planck and DS to get even tighter constraint on the six mate and which is the amplitude of fluctuations and dark matter so following the analysis then we we farther at other late-time physics which is low wretched means we are near the our time and so we we join our analysis with other measurements from baryonyka acoustic oscillation and supernovae and we actually obtain tighter constraints on the late-time measurements in orange than using only DS data no which is this contours here here they got reduced and they are still consistent although it is true that the discrepancy is in the same direction that we have found in previous surveys we cannot claim to be a discrepancy so Planck and galaxy surveys agrees on this so finally combining all late-time experiments and CMB experiments we get these very tight constraints on equation of a state of dark matter they have a parameter and other cosmological parameters and we have obtained the most precise measurements of the of the land the cold matter parameters with a density of matter of 0.3 and absolutely no evidence for varying equation of a state of dark energy so this is telling us that the lambda cold matter is working very well agrees very well with our observations one one note that I forgot to say but I think it's important this plot this is the first time that a galaxy survey reach reaches the same resolution of a CMB experiment so this has been very a major major result is that we finally get the same resolution as CMB for these cosmological parameters so get into an end so what's for the future the what I've presented here is a very precise test of the lambda cold matter model and it shows that we haven't found any discrepancies with previous measurements of measurements of the CMB but of course this doesn't explain what is lambda cold matter it doesn't explain what is dark energy or or dark matter this is due because it is not very sensitive to models of time-varying dark energy but for the year 5 if we join the results from weak lensing with galaxy clusters this will break the degeneracy and here is a forecast on the plot and in the middle we see the the resolution of year 5 when it's finished when we finish the analysis so pay attention for the future since we DS in principle will be able to give tight constraints on the possible evolution of the dark energy equation of a state so finally we've seen that there are wide range of probes from early and late light time universe with geometry test that agree on a common fiducian lambda cold matter cosmology DS with year 1 observation has added most of the precise measurements of a structure in the late time universe very and the results are competitive and consistent with plan CMB results and this claim offset between Planck and late time surveys is insignificant and we can give precise joints measurements which gave us the results that are are expected in the sense a density matter of 0.3 an amplitude of fluctuation of 0.8 and a dark an equation of a state of dark matter equals to minus 1 so in the next years we will combine with more data and with other observables to improve what we have done so far so thank you and please we are open to questions okay thank you very much a radio was very nice talk and well well now we have people here in the room that I don't know if any of you have questions or some comments about the presentation go ahead Nicolas please just before the summary aurelio you say like it was written that it doesn't explain lambda CDM I am not sure to understand what do you mean what let me sorry my computer got trying to find the where I think the previous one so slight 36 I think yeah so yes right so you say it doesn't explain lambda CDM exactly so to explain to explain lambda CDM we would prove because we would probably we need to answer which is the equation of a state of dark energy so far we can measure the density basically the amount of dark energy with these weak lensing probe we can measure the density of dark energy but we don't know if the question of a state of dark energy evolve or if it's equals to minus one which is for the energy of the vacuum so this method is insensitive to the question of a state of dark energy okay I have a question regarding this comparison with plan results because what you have there is if I see correctly you have like less omega matter right there is some reason why the VAS point to to this lower value I mean well I know that it's not exactly what you are measuring here but it's just for relation but why it's a good question because it is actually also related to this other problem that I don't know if you have heard about it which is the measurement of the expansion rate they have a constant measurements of CMB experiments give I think are lower values of the expansion rate while high rate like galaxy surveys give a higher rates of expansion and this value is actually very correlated to dark matter also so they are very they are coupled so this discrepancy might be related also to the discrepancy of the Hubble expansion rate so those effects are together so I don't know if these shifts if we if we fix they have a constant if we imagine okay we know Hubble constant is 70 probably this discrepancy would wouldn't be present so it is related to also to the Hubble expansion rate but of course I mean it is not significant so maybe we cannot say that there is a discrepancy but but it's also related to the Hubble expansion rate okay thank you any other question here in the room yes I have a question can you hear me yes yeah hi John please so I was wondering if the combined feet gives any further constraints to parameters like the sum of neutrino masses I think that there was someone the collaboration that look at but actually I think we are again we are not very sensitive to neutrino masses yet more the biggest con constraints come from CMB from early from early time but I think there's been a paper that put constraints on neutrino masses but sorry unfortunately I don't know the details of the result but I know someone look at but the different the increase on resolution is not is not great probably we have to wait to the five year results when we combine with galaxy clusters and supernovae that we might have an answer to the neutrino masses but it's been look at of course it's been look at but nothing significant yet constraints are almost the same as in the universe okay thank you thank you any other question here yes I have another one yeah so at the very beginning of your presentation over a year just before talking about the DS experiment so we were talking about the cosmic shear and this tension with the lambda CDM yeah so just be clear this tension is when you compare high and low redshift right exactly okay yeah that's not exactly CMB means cosmic microwave backgrounds that is when the universe was less than 400,000 years old yeah but it was because in in this figure you cannot see really attention no I mean all the blobs seems to be yeah no no exactly I mean I think was too early to say and I think it was acclaimed by kids team I think kids said okay I think there is a tension and that's spread on the news and spread on the community but basically what we are showing in our result is that that tension is not significant this it's a non-issue for now but it's true that is in the same direction but it's a non-issue and of course I when I see this figure I always get surprised okay Planck is more recent but if you look at WMAP there is the same result so I kind of repeated this because it's kind of common today hot topic but for me it's never was such an issue but at least I wanted to create some controversy because if not it looks like I mean the lambda-cold armatter fits very well to the data so at least I want to give some uncertainties okay and the last question is how long is DS supposed to take data so in principle it should finish now in February it during five year it has been using five months of the Blanco telescope the best night to the survey so we are ending the five year but it might be an extension for a six year since we have in the middle we have one very bad year because of the Nino and we could only take almost half of our exposures so it might be an extension for a six that means that by probably by 2020 I guess that we would have final cosmological results maybe earlier 19 2019 probably okay thanks okay thank you very much well I don't see any other question or comments here then I think we can say thank you to our radio for this very nice talk and well it was how well we would have this we hope to have these slides in our white page in the future so yeah I mean when I close the room I send you the slides okay perfect that will be great and also well this video will be on YouTube you can watch this and send to my family as you like and then well thank you very much also I will follow these talks from now on okay that's great those well I think I mean it's funny but that we never hear here in my observatory no one knows about these talks maybe about I don't know why the dissemination yeah anyway we are trying to make more publicity also invited but would be great okay well in two weeks we will have another webinar and well just follow us in our social networks okay thank you very much and goodbye everyone