From seminars-announce.astro-at-su.se at lists.su.se Tue Sep 5 21:40:36 2017 From: seminars-announce.astro-at-su.se at lists.su.se (Astronomy seminar announcements) Date: Tue, 5 Sep 2017 21:40:36 +0200 Subject: [Astronomy seminar] Astronomy seminar this Friday Message-ID: All, The astronomy seminar this Friday will be *** Friday 8 of Sept from 10:30 to 11:30 at FC61 *** Welcome. Title: The circumgalactic gas and metals around star forming and elliptical galaxies Speaker: Sijing Shen, Institute of Theoretical Astrophysics, Oslo Abstract: Understanding the baryon cycle in galaxies, i.e., how gas is accreted onto galaxies, consumed in star formation, and ejected back to the environment is crucial to understand galaxy formation and evolution. Studies of the distribution, kinematics and evolution of the gas and metals in the circumgalactic medium (CGM) provide clues to understanding this baryon cycle. In this talk, I will briefly review recent progress on observational and theoretical studies on the CGM. I will then present new results on the circumgalactic gas and metals around massive star-forming and elliptical galaxies at z~3-0 from two suites of “zoom-in” cosmological hydrodynamic simulations, and detailed comparisons with observed Lyman alpha (Lya) and metal absorption data (e.g. Mg II, Si II, Si III, C II, C III, CIV and OVI) in particular from the COS-Halos Survey. We found that simulations generally reproduce the distributions of of neutron hydrogen and high-ionisation metal ions (such as O VI), but significantly underestimate the low-ionisation metal species. I will explore possible reasons for the mis-match and discuss the correlation between the cold, enriched gas probed by the low ions and the warm-hot gas probed by O VI. I will also discuss the impact of feedback from supernova and the active galactic nuclei (AGN). From seminars-announce.astro-at-su.se at lists.su.se Fri Sep 8 08:54:28 2017 From: seminars-announce.astro-at-su.se at lists.su.se (Astronomy seminar announcements) Date: Fri, 8 Sep 2017 08:54:28 +0200 Subject: [Astronomy seminar] Astronomy seminar this Friday In-Reply-To: References: Message-ID: Reminder! On 9/6/17 16:22, Matthew Hayes wrote: > All, > > The next Astronomy seminar will be: > > *** Friday 8 of Sept from 10:30 to 11:30 at FC61 *** > > Welcome. > > > Title:  The circumgalactic gas and metals around star forming and > elliptical galaxies > > Speaker: Sijing Shen, Institute of Theoretical Astrophysics, Oslo > > Abstract: > > Understanding the baryon cycle in galaxies, i.e., how gas is accreted > onto galaxies, consumed in star formation, and ejected back to the > environment is crucial to understand galaxy formation and evolution. > Studies of the distribution, kinematics and evolution of the gas and > metals in the circumgalactic medium (CGM) provide clues to understanding > this baryon cycle.  In this talk, I will briefly review recent progress > on observational and theoretical studies on the CGM. I will then present > new results on the circumgalactic gas and metals around massive > star-forming and elliptical galaxies at z~3-0 from two suites of > “zoom-in” cosmological hydrodynamic simulations, and detailed > comparisons with observed Lyman alpha (Lya) and metal absorption data > (e.g. Mg II, Si II, Si III, C II, C III, CIV and OVI) in particular from > the COS-Halos Survey. We found that simulations generally reproduce the > distributions of of neutron hydrogen and high-ionisation metal ions > (such as O VI), but significantly underestimate the low-ionisation metal > species. I will explore possible reasons for the mis-match and discuss > the correlation between the cold, enriched gas probed by the low ions > and the warm-hot gas probed by O VI. I will also discuss the impact of > feedback from supernova and the active galactic nuclei (AGN). -- Matthew Hayes Wallenberg Academy Fellow email: matthew at astro.su.se Stockholm University tel: +46 (0)8 5537 8521 Department of Astronomy & OKC fax: +46 (0)8 5537 8510 AlbaNova University Centre inst: www.astro.su.se SE-106 91 Stockholm personal: www.xayes.org/pub/ Sweden skype: matthewhayes From seminars-announce.astro-at-su.se at lists.su.se Mon Sep 18 14:39:46 2017 From: seminars-announce.astro-at-su.se at lists.su.se (Astronomy seminar announcements) Date: Mon, 18 Sep 2017 14:39:46 +0200 Subject: [Astronomy seminar] Astronomy Seminar on Friday 22nd of September Message-ID: Title: Neutrino-Radiation Hydrodynamic Simulations of Core-Collapse Supernovae Speaker: Evan Patrick O'Connor (SU) Friday 22nd of September from 10:30 to 11:30 at FC61. Abstract: The end game of massive star stellar evolution is a core-collapse supernova. It is triggered when the iron core in a massive star (M>8-10Msun) can no longer counterbalance the force of gravity and collapses. The collapse continues to nuclear densities at which point the residual strong force can supply enough pressure to halt collapse. The inertia of the collapsing core is elastically transfer to outgoing kinetic energy (the core bounces) and a shockwave is launched. The core-collapse problem is that this shockwave stalls soon after bounce and becomes an accretion shock. The goal of supernova theory is to understand how this shock is reenergized and how it gives rise to the properties of observed supernovae. Crucial to this revival is the so-called neutrino mechanism where the intense luminosity of neutrinos emitted from the newly formed neutron star is able to heat the newly shocked material and drive an explosion. Modeling core-collapse supernovae numerically involves bringing together all four fundamental forces in a complex multi-physics environment. In this seminar, I will give an overview of the physics of core-collapse supernovae, present our recent efforts on modelling core-collapse supernovae in 1, 2, and 3 spatial dimensions and highlight the path forward in the coming years. From seminars-announce.astro-at-su.se at lists.su.se Mon Sep 25 10:02:41 2017 From: seminars-announce.astro-at-su.se at lists.su.se (Astronomy seminar announcements) Date: Mon, 25 Sep 2017 12:02:41 +0400 Subject: [Astronomy seminar] Astronomy seminar on Friday 29th of September Message-ID: Title: “Exoplanet characterisation with transit spectroscopy” Speaker: Nikolai Piskunov (Uppsala University) Friday 29th of September from 10:30 to 11:30 at FC61. Abstract: I will present novel data analysis methods for deriving transmission spectra from spectroscopic observations of exoplanets during transits. These methods were developed by Erik Aronsson and myself in anticipation of availability of the CRIRES+ VLT instrument, In the meantime we have applied them to existing data sets with some unexpected results. From seminars-announce.astro-at-su.se at lists.su.se Mon Oct 2 06:47:34 2017 From: seminars-announce.astro-at-su.se at lists.su.se (Astronomy seminar announcements) Date: Mon, 2 Oct 2017 06:47:34 +0200 Subject: [Astronomy seminar] Astronomy Seminar on Friday 6 October Message-ID: All, The next Astronomy seminar will be: *** Friday 6 of October from 10:30 to 11:30 at FC 61 *** Welcome. Title: Illuminating the Dark Universe with fluorescent Lyman-alpha emission Speaker: Sebastiano Cantalupo, ETH Zürich Abstract: Gravitational collapse during the Universe's first billion years transformed a nearly homogeneous matter distribution into a network of filaments - the Cosmic Web - where galaxies form and evolve. Because most of this material is too diffuse to form stars, its study has been limited so far to absorption probes against background sources. In this talk, I will present the results of a new program to directly detect and study high-redshift cosmic gas in emission using bright quasars and galaxies as external "sources of illumination’’. In particular, I will show results from ultra-deep narrow-band imaging and recent integral-field-spectroscopy as a part of the MUSE Guaranteed Time of Observation program that revealed numerous giant Lyman-alpha emitting filaments extending up to several hundred kpc around quasars and bright galaxies. I will discuss how the unexpectedly high luminosities of these systems, together with the constraints from Helium and metal extended emission, represent a challenge for our current understanding of cosmological structure formation. In particular, I will show that current observations suggest that a large amount of “cold" and dense gaseous “clumps" should be present around high-redshift galaxies and I will present our first attempts to understand the origin and nature of these structures using high-resolution hydrodynamical simulations. From seminars-announce.astro-at-su.se at lists.su.se Thu Oct 5 19:34:15 2017 From: seminars-announce.astro-at-su.se at lists.su.se (Astronomy seminar announcements) Date: Thu, 5 Oct 2017 19:34:15 +0200 Subject: [Astronomy seminar] Astronomy Seminar on Friday 6 October In-Reply-To: <753f44dc-c138-6417-5137-594967790790@astro.su.se> References: <753f44dc-c138-6417-5137-594967790790@astro.su.se> Message-ID: Reminder! On 2017-10-02 06:47, Matthew Hayes wrote: > All, > > The next Astronomy seminar will be: > > *** Friday 6 of October from 10:30 to 11:30 at FC 61 *** > > Welcome. > > > Title: Illuminating the Dark Universe with fluorescent Lyman-alpha emission > > Speaker: Sebastiano Cantalupo, ETH Zürich > > Abstract: Gravitational collapse during the Universe's first billion > years transformed a nearly homogeneous matter distribution into a > network of filaments - the Cosmic Web - where galaxies form and evolve. > Because most of this material is too diffuse to form stars, its study > has been limited so far to absorption probes against background sources. > In this talk, I will present the results of a new program to directly > detect and study high-redshift cosmic gas in emission using bright > quasars and galaxies as external "sources of illumination’’. In > particular, I will show results from ultra-deep narrow-band imaging and > recent integral-field-spectroscopy as a part of the MUSE Guaranteed Time > of Observation program that revealed numerous giant Lyman-alpha emitting > filaments extending up to several hundred kpc around quasars and bright > galaxies. I will discuss how the unexpectedly high luminosities of these > systems, together with the constraints from Helium and metal extended > emission, represent a challenge for our current understanding of > cosmological structure formation. In particular, I will show that > current observations suggest that a large amount of “cold" and dense > gaseous “clumps" should be present around high-redshift galaxies and I > will present our first attempts to understand the origin and nature of > these structures using high-resolution hydrodynamical simulations. -- Matthew Hayes Wallenberg Academy Fellow email: matthew at astro.su.se Stockholm University tel: +46 (0)8 5537 8521 Department of Astronomy & OKC fax: +46 (0)8 5537 8510 AlbaNova University Centre inst: www.astro.su.se SE-106 91 Stockholm personal: www.xayes.org/pub/ Sweden skype: matthewhayes From seminars-announce.astro-at-su.se at lists.su.se Mon Oct 16 10:52:58 2017 From: seminars-announce.astro-at-su.se at lists.su.se (Astronomy seminar announcements) Date: Mon, 16 Oct 2017 10:52:58 +0200 Subject: [Astronomy seminar] Astronomy seminar on Friday 20th of October Message-ID: Title: What causes the solar seasons? Speaker: Mausumi Dikpati (HAO/NCAR) Friday 20th of October from 10:30 to 11:30 at FC61. Abstract: Recent observations indicate that solar cycle variability consists of short-term quasi-periodic bursts of magnetic activity, or the ``solar seasons''. Burst periods are 6-18 months. Using a nonlinear MHD shallow water tachocline model we show that a back-and-forth exchange of energy between tachocline latitudinal differential rotation and Rossby waves occurs with a periodicity of 2-19 months, for a wide range of effective gravities, differential rotation amplitude, latitude location of toroidal magnetic bands and their peak field strength. These Tachocline Nonlinear Oscillations (TNO) can cause enhanced activity bursts when the Rossby wave energy grows to its maximum, because the tachocline top surface is maximally deformed then. Hence, nearly 'frozen-in' toroidal fields can enter the convection zone from the tachocline, starting their buoyant rise to the surface to erupt as active regions. The bursty phase is followed by a relatively quiet phase, during which the differential rotation gets restored by extracting energy from Rossby waves and top surface deformations subside. Our results indicate that the solar seasons can be caused by TNO's. I will close by discussing how we can forecast these seasons by coupling with data assimilation. From seminars-announce.astro-at-su.se at lists.su.se Mon Oct 23 13:04:20 2017 From: seminars-announce.astro-at-su.se at lists.su.se (Astronomy seminar announcements) Date: Mon, 23 Oct 2017 13:04:20 +0200 Subject: [Astronomy seminar] Astronomy seminar on Friday 27th of October Message-ID: Title: Combining observations and 3D numerical simulations for solar flare modelling Speaker: Miho Janvier (Institut d'Astrophysique Spatiale, Paris) Friday 27th of October from 10:30 to 11:30 at FC61. Abstract: Solar flares are the most energetic events taking place in our solar system. They result from the conversion of magnetic energy stored in the Sun’s atmosphere into energetic particles, heat, and in some cases into the launch of solar storms (or Coronal Mass Ejections - CMEs) in interplanetary space. Solar flares and CMEs are at the origin of space weather events: on Earth, they lead to geomagnetic storms and can be responsible for disruptions of satellite systems, as well as electricity transport on large-scale national power grids. Auroras, atmospheric ion losses, and other effects of space weather also take place on other planets in the solar system. Therefore, understanding the underlying mechanisms of solar flares is of primary importance to better predict their evolution and influence on nearby planets. Increased temporal and spatial resolutions of ground and space observatories have allowed us to refine a standard model for eruptive flares, which can explain their generic features (the presence of flare ribbons, flare loops and a twisted erupting magnetic structure). In particular, 3D MHD modelling has provided us with some predictions on the magnetic field behaviour during the eruption, such as the evolution of regions where the magnetic field energy is converted. These predictions are nowadays well documented with the help of observations with, e.g., the AIA and HMI instruments aboard the NASA mission Solar Dynamics Observatory. We will look at how these predictions can be validated with a careful study of the active region configuration with different techniques, whether with dynamic (MHD) or static (also known as magnetic field extrapolations) numerical models. This will show how approaches combining different modelling techniques and observations provide a major step in extending and completing the standard model for eruptive flares in its 3D version. -------------- next part -------------- An HTML attachment was scrubbed... URL: From seminars-announce.astro-at-su.se at lists.su.se Mon Oct 30 21:33:13 2017 From: seminars-announce.astro-at-su.se at lists.su.se (Astronomy seminar announcements) Date: Mon, 30 Oct 2017 21:33:13 +0100 Subject: [Astronomy seminar] Astronomy seminar on Thursday 2nd of November Message-ID: Dear all, this week our weekly seminar will take place on *Thursday* at 10:30 instead of Friday. Title: A revised picture of properties of clumps observed in distant star-forming galaxies. Speaker: Miroslava Dessauges-Zavadsky (Geneva Observatory). *Thursday* 2nd of November from 10:30 to 11:30 at *FB54*. Abstract: Clumpy rest-frame UV morphologies have been revealed among z=1-3 star-forming galaxies, with the majority of galaxies shown to be dominated by ordered disk rotation. It has been suggested that the observed clumps are formed during the disk fragmentation resulting from gravitational instabilities maintained by the gas inflow onto galaxies. The physical properties (masses and radii) of these clumps and their possible role in the galactic bulge formation are, however, largely debated both on the observational point of view and in numerical simulations. Comparing clumps selected in different ways, and in lensed or blank field galaxies, we examine the effects of spatial resolution and sensitivity on the inferred stellar masses and radii. Large differences are found, with median stellar masses ranging from ~109 M☉ for clumps in the often-referenced field galaxies to ~107 M☉ for fainter clumps selected in deep-field or lensed galaxies. We argue that the clump masses, observed in non-lensed galaxies with a limited spatial resolution of ∼1 kpc, are artificially increased due to the clustering of clumps of smaller mass. Furthermore, we show that the sensitivity threshold used for the clump selection affects the inferred masses even more strongly than resolution, biasing clumps at the low-mass end. Both improved spatial resolution and sensitivity appear to shift the clump stellar mass distribution to lower masses by almost two orders of magnitude, in agreement with clump masses found in recent high-resolution simulations of disk fragmentation. We discuss: (1) the nature of the most massive clumps and the connection with the mass of their host galaxies; and (2) the existence of a characteristic clump mass scale against the hierarchical structure of clumps. Finally, we provide a direct proof of the resolution and sensitivity effects on clump properties thanks to a unique case-study supplied by an exceptional lensing configuration in the field of the galaxy cluster MACSJ1206, allowing to reach in one counter-image 30 pc physical scales in a z=1 galaxy. A coherent view of the formation and evolution of clumps in distant galaxies emerges fully in agreement with state-of-the art numerical and mock simulations. -------------- next part -------------- An HTML attachment was scrubbed... URL: From seminars-announce.astro-at-su.se at lists.su.se Mon Nov 6 12:50:38 2017 From: seminars-announce.astro-at-su.se at lists.su.se (Astronomy seminar announcements) Date: Mon, 6 Nov 2017 12:50:38 +0100 Subject: [Astronomy seminar] Astronomy seminar on Friday 10th of November Message-ID: Title: Stellar activity and its effects on exoplanets and their detection Speaker: Heidi Korhonen (University of Copenhagen) Friday 10th of November from 10:30 to 11:30 at FC61. Abstract: Our Sun is known to harbour magnetic fields which cause myriad of phenomena, e.g., starspots, flares, and coronal mass ejections. The existence of starspots in other stars than the Sun has been known for more than five decades. The development of observing and analysis techniques that has occurred during the past two decades has enabled us to study the detailed starspot and magnetic field configurations on stars of different types and ages. Starspots also change the shape of the observed spectral line profiles in a way that can mimic radial velocity variations from exoplanet, especially hampering the detection of small exoplanets. Additionally, coronal mass ejections, explosive events that occur basically daily on the Sun, are one of the main ingredients in the changing space environment of the Earth. The lack of knowledge on the properties of stellar coronal mass ejections hinders our understanding of the space environments of planets orbiting other stars. In this talk I will discuss stellar activity, especially starspots and coronal mass ejections, and how it affects the orbiting planets and their detection. From seminars-announce.astro-at-su.se at lists.su.se Mon Nov 13 22:44:46 2017 From: seminars-announce.astro-at-su.se at lists.su.se (Astronomy seminar announcements) Date: Mon, 13 Nov 2017 22:44:46 +0100 Subject: [Astronomy seminar] Astronomy seminar on Friday 17th November Message-ID: Title: Observations of fast-moving structures in the debris disk of AU Mic: 3 years of follow-up with SPHERE Speaker: Anthony Boccaletti (Observatoire de Paris) Friday 17th of November from 10:30 to 11:30 at FC61. Abstract: The instrument SPHERE was installed at the VLT in 2014 and provides a significant gain in terms of contrast with respect to the previous generation of instruments. As a result, we now have access to very high contrast in the close environment of bright stars in particular the young systems in order to search for giant planets and circumstellar disks. During the commissioning in Aug 2014, SPHERE has revealed several structures (several AU in size) in the form of arches or undulations in the midplane of the debris disk around the star AU Microscopii. This disk is seen edge on and the system is conveniently close (~10 pc) and young as well (~20 Myr). The comparison of these SPHERE observations with the ones from STIS/HST 4 years before, not only allowed us to re-identify the structures in older data but most importantly led us to conclude that these structures were moving outwards in the disk, some with very large projected speed (4-10 km/s) hence possibly escaping the system. Several assumptions were considered to explain this behaviour, one of the them involves a body in Keplerian motion releasing some dust under the influence of the star’s activity. Since then, the object is regularly observed with SPHERE as part of the GTO and during a monitoring program. After a short introduction on the instrument and its modes as well as the achieved performance, I’ll remind the initial results from 2014 which led to the discovery of these fast-moving structures. Then, I’ll present the recent observations obtained from the last 3 years which unambiguously confirm the motion of the structures. The hypothesis of a parent body emitting an outflow of dust will be discussed in the light of these observations. From seminars-announce.astro-at-su.se at lists.su.se Wed Dec 6 09:42:29 2017 From: seminars-announce.astro-at-su.se at lists.su.se (Astronomy seminar announcements) Date: Wed, 06 Dec 2017 09:42:29 +0100 Subject: [Astronomy seminar] Astronomy seminar on Thusday 7th of December Message-ID: Title: Gravitational waves, short GRBs and kilonova: new signals of merging binaries Speaker: Andrew Levan (University of Warwick) Thursday 7th of December from 10:30 to 11:30 at FA32. Abstract: The discovery of coincident gravitational waves and light from a merger neutron star opens a new window into the Universe, allowing us to use these “multiple” messengers to answer central questions in astrophysics. Here I will discuss how the combination of gravitational waves with a short-GRB and an associated kilonova provides new insights into the origins of short GRBs, the sites for the production of the heaviest elements and a new ruler for the Universe. I will end by looking forward to what we might expect for new events, discovered in the coming years.   -------------- next part -------------- An HTML attachment was scrubbed... URL: From seminars-announce.astro-at-su.se at lists.su.se Mon Dec 11 18:46:17 2017 From: seminars-announce.astro-at-su.se at lists.su.se (Astronomy seminar announcements) Date: Mon, 11 Dec 2017 18:46:17 +0100 Subject: [Astronomy seminar] Astronomy Seminar on Friday 15 December Message-ID: Dear all, The next Astronomy Seminar, and the final one for the 2017, will be: *** Friday 15 of December from 10:30 to 11:30 at FC 61 *** Welcome. Speaker: Celine Peroux, Laboratoire dʼAstrophysique de Marseille Title: The Cosmic Baryon Cycle: Accretion, Outflows and the Circum-Galactic Medium Abstract: Studies of the circumgalactic medium are crucial for understanding both the inflows of gas accreting into galaxies and the outflows carrying away the energy and metals generated inside galaxies. We have shown that a powerful tool to study this so-called "baryon cycle" is offered by absorption lines observed in background quasar spectra which trace the neutral gas reservoir for star formation. It is also essential to complement the absorption spectroscopy with imaging of the stellar component and cold gas content of the absorbing galaxies. We find that while Integral field spectroscopy (IFS) has proven an efficient way to detect these objects in emission, radio observations are just starting to unveil their molecular gas content. I will present new MUSE and ALMA observations which, together, provide fresh clues on the physics of gas flows. I will discuss prospects of detecting the circumgalactic medium in emission and other future progress which will likely impact galaxy formations studies at all cosmic epochs. From seminars-announce.astro-at-su.se at lists.su.se Thu Dec 14 19:45:12 2017 From: seminars-announce.astro-at-su.se at lists.su.se (Astronomy seminar announcements) Date: Thu, 14 Dec 2017 19:45:12 +0100 Subject: [Astronomy seminar] Astronomy Seminar on Friday 15 December In-Reply-To: <6b1412ce-bdd8-157b-f5de-848cf06705e7@astro.su.se> References: <6b1412ce-bdd8-157b-f5de-848cf06705e7@astro.su.se> Message-ID: All, A reminder about tomorrow's Astronomy seminar, the last of the year. Matt On 12/11/17 18:46, Matthew Hayes wrote: > Dear all, > > The next Astronomy Seminar, and the final one for the 2017, will be: > > *** Friday 15 of December from 10:30 to 11:30 at FC 61 *** > > Welcome. > > Speaker: Celine Peroux, Laboratoire dʼAstrophysique de Marseille > > Title: The Cosmic Baryon Cycle: Accretion, Outflows and the > Circum-Galactic Medium > > Abstract: Studies of the circumgalactic medium are crucial for > understanding both the inflows of gas accreting into galaxies and the > outflows carrying away the energy and metals generated inside galaxies. > We have shown that a powerful tool to study this so-called "baryon > cycle" is offered by absorption lines observed in background quasar > spectra which trace the neutral gas reservoir for star formation. It is > also essential to complement the absorption spectroscopy with imaging of > the stellar component and cold gas content of the absorbing galaxies. We > find that while Integral field spectroscopy (IFS) has proven an > efficient way to detect these objects in emission, radio observations > are just starting to unveil their molecular gas content. I will present > new MUSE and ALMA observations which, together, provide fresh clues on > the physics of gas flows. I will > discuss prospects of detecting the circumgalactic medium in emission and > other future progress which will likely impact galaxy formations studies > at all cosmic epochs.